mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-24 05:04:00 +08:00
d3acb15a3a
Pull iov_iter updates from Al Viro: "iov_iter cleanups and fixes. There are followups, but this is what had sat in -next this cycle. IMO the macro forest in there became much thinner and easier to follow..." * 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (37 commits) csum_and_copy_to_pipe_iter(): leave handling of csum_state to caller clean up copy_mc_pipe_to_iter() pipe_zero(): we don't need no stinkin' kmap_atomic()... iov_iter: clean csum_and_copy_...() primitives up a bit copy_page_from_iter(): don't need kmap_atomic() for kvec/bvec cases copy_page_to_iter(): don't bother with kmap_atomic() for bvec/kvec cases iterate_xarray(): only of the first iteration we might get offset != 0 pull handling of ->iov_offset into iterate_{iovec,bvec,xarray} iov_iter: make iterator callbacks use base and len instead of iovec iov_iter: make the amount already copied available to iterator callbacks iov_iter: get rid of separate bvec and xarray callbacks iov_iter: teach iterate_{bvec,xarray}() about possible short copies iterate_bvec(): expand bvec.h macro forest, massage a bit iov_iter: unify iterate_iovec and iterate_kvec iov_iter: massage iterate_iovec and iterate_kvec to logics similar to iterate_bvec iterate_and_advance(): get rid of magic in case when n is 0 csum_and_copy_to_iter(): massage into form closer to csum_and_copy_from_iter() iov_iter: replace iov_iter_copy_from_user_atomic() with iterator-advancing variant [xarray] iov_iter_npages(): just use DIV_ROUND_UP() iov_iter_npages(): don't bother with iterate_all_kinds() ...
3855 lines
108 KiB
C
3855 lines
108 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* linux/mm/filemap.c
|
|
*
|
|
* Copyright (C) 1994-1999 Linus Torvalds
|
|
*/
|
|
|
|
/*
|
|
* This file handles the generic file mmap semantics used by
|
|
* most "normal" filesystems (but you don't /have/ to use this:
|
|
* the NFS filesystem used to do this differently, for example)
|
|
*/
|
|
#include <linux/export.h>
|
|
#include <linux/compiler.h>
|
|
#include <linux/dax.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/sched/signal.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/capability.h>
|
|
#include <linux/kernel_stat.h>
|
|
#include <linux/gfp.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/mman.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/file.h>
|
|
#include <linux/uio.h>
|
|
#include <linux/error-injection.h>
|
|
#include <linux/hash.h>
|
|
#include <linux/writeback.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/pagevec.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/security.h>
|
|
#include <linux/cpuset.h>
|
|
#include <linux/hugetlb.h>
|
|
#include <linux/memcontrol.h>
|
|
#include <linux/cleancache.h>
|
|
#include <linux/shmem_fs.h>
|
|
#include <linux/rmap.h>
|
|
#include <linux/delayacct.h>
|
|
#include <linux/psi.h>
|
|
#include <linux/ramfs.h>
|
|
#include <linux/page_idle.h>
|
|
#include <asm/pgalloc.h>
|
|
#include <asm/tlbflush.h>
|
|
#include "internal.h"
|
|
|
|
#define CREATE_TRACE_POINTS
|
|
#include <trace/events/filemap.h>
|
|
|
|
/*
|
|
* FIXME: remove all knowledge of the buffer layer from the core VM
|
|
*/
|
|
#include <linux/buffer_head.h> /* for try_to_free_buffers */
|
|
|
|
#include <asm/mman.h>
|
|
|
|
/*
|
|
* Shared mappings implemented 30.11.1994. It's not fully working yet,
|
|
* though.
|
|
*
|
|
* Shared mappings now work. 15.8.1995 Bruno.
|
|
*
|
|
* finished 'unifying' the page and buffer cache and SMP-threaded the
|
|
* page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
|
|
*
|
|
* SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
|
|
*/
|
|
|
|
/*
|
|
* Lock ordering:
|
|
*
|
|
* ->i_mmap_rwsem (truncate_pagecache)
|
|
* ->private_lock (__free_pte->__set_page_dirty_buffers)
|
|
* ->swap_lock (exclusive_swap_page, others)
|
|
* ->i_pages lock
|
|
*
|
|
* ->i_mutex
|
|
* ->i_mmap_rwsem (truncate->unmap_mapping_range)
|
|
*
|
|
* ->mmap_lock
|
|
* ->i_mmap_rwsem
|
|
* ->page_table_lock or pte_lock (various, mainly in memory.c)
|
|
* ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
|
|
*
|
|
* ->mmap_lock
|
|
* ->lock_page (access_process_vm)
|
|
*
|
|
* ->i_mutex (generic_perform_write)
|
|
* ->mmap_lock (fault_in_pages_readable->do_page_fault)
|
|
*
|
|
* bdi->wb.list_lock
|
|
* sb_lock (fs/fs-writeback.c)
|
|
* ->i_pages lock (__sync_single_inode)
|
|
*
|
|
* ->i_mmap_rwsem
|
|
* ->anon_vma.lock (vma_adjust)
|
|
*
|
|
* ->anon_vma.lock
|
|
* ->page_table_lock or pte_lock (anon_vma_prepare and various)
|
|
*
|
|
* ->page_table_lock or pte_lock
|
|
* ->swap_lock (try_to_unmap_one)
|
|
* ->private_lock (try_to_unmap_one)
|
|
* ->i_pages lock (try_to_unmap_one)
|
|
* ->lruvec->lru_lock (follow_page->mark_page_accessed)
|
|
* ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
|
|
* ->private_lock (page_remove_rmap->set_page_dirty)
|
|
* ->i_pages lock (page_remove_rmap->set_page_dirty)
|
|
* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
|
|
* ->inode->i_lock (page_remove_rmap->set_page_dirty)
|
|
* ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
|
|
* bdi.wb->list_lock (zap_pte_range->set_page_dirty)
|
|
* ->inode->i_lock (zap_pte_range->set_page_dirty)
|
|
* ->private_lock (zap_pte_range->__set_page_dirty_buffers)
|
|
*
|
|
* ->i_mmap_rwsem
|
|
* ->tasklist_lock (memory_failure, collect_procs_ao)
|
|
*/
|
|
|
|
static void page_cache_delete(struct address_space *mapping,
|
|
struct page *page, void *shadow)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, page->index);
|
|
unsigned int nr = 1;
|
|
|
|
mapping_set_update(&xas, mapping);
|
|
|
|
/* hugetlb pages are represented by a single entry in the xarray */
|
|
if (!PageHuge(page)) {
|
|
xas_set_order(&xas, page->index, compound_order(page));
|
|
nr = compound_nr(page);
|
|
}
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
VM_BUG_ON_PAGE(PageTail(page), page);
|
|
VM_BUG_ON_PAGE(nr != 1 && shadow, page);
|
|
|
|
xas_store(&xas, shadow);
|
|
xas_init_marks(&xas);
|
|
|
|
page->mapping = NULL;
|
|
/* Leave page->index set: truncation lookup relies upon it */
|
|
mapping->nrpages -= nr;
|
|
}
|
|
|
|
static void unaccount_page_cache_page(struct address_space *mapping,
|
|
struct page *page)
|
|
{
|
|
int nr;
|
|
|
|
/*
|
|
* if we're uptodate, flush out into the cleancache, otherwise
|
|
* invalidate any existing cleancache entries. We can't leave
|
|
* stale data around in the cleancache once our page is gone
|
|
*/
|
|
if (PageUptodate(page) && PageMappedToDisk(page))
|
|
cleancache_put_page(page);
|
|
else
|
|
cleancache_invalidate_page(mapping, page);
|
|
|
|
VM_BUG_ON_PAGE(PageTail(page), page);
|
|
VM_BUG_ON_PAGE(page_mapped(page), page);
|
|
if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
|
|
int mapcount;
|
|
|
|
pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
|
|
current->comm, page_to_pfn(page));
|
|
dump_page(page, "still mapped when deleted");
|
|
dump_stack();
|
|
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
|
|
|
|
mapcount = page_mapcount(page);
|
|
if (mapping_exiting(mapping) &&
|
|
page_count(page) >= mapcount + 2) {
|
|
/*
|
|
* All vmas have already been torn down, so it's
|
|
* a good bet that actually the page is unmapped,
|
|
* and we'd prefer not to leak it: if we're wrong,
|
|
* some other bad page check should catch it later.
|
|
*/
|
|
page_mapcount_reset(page);
|
|
page_ref_sub(page, mapcount);
|
|
}
|
|
}
|
|
|
|
/* hugetlb pages do not participate in page cache accounting. */
|
|
if (PageHuge(page))
|
|
return;
|
|
|
|
nr = thp_nr_pages(page);
|
|
|
|
__mod_lruvec_page_state(page, NR_FILE_PAGES, -nr);
|
|
if (PageSwapBacked(page)) {
|
|
__mod_lruvec_page_state(page, NR_SHMEM, -nr);
|
|
if (PageTransHuge(page))
|
|
__mod_lruvec_page_state(page, NR_SHMEM_THPS, -nr);
|
|
} else if (PageTransHuge(page)) {
|
|
__mod_lruvec_page_state(page, NR_FILE_THPS, -nr);
|
|
filemap_nr_thps_dec(mapping);
|
|
}
|
|
|
|
/*
|
|
* At this point page must be either written or cleaned by
|
|
* truncate. Dirty page here signals a bug and loss of
|
|
* unwritten data.
|
|
*
|
|
* This fixes dirty accounting after removing the page entirely
|
|
* but leaves PageDirty set: it has no effect for truncated
|
|
* page and anyway will be cleared before returning page into
|
|
* buddy allocator.
|
|
*/
|
|
if (WARN_ON_ONCE(PageDirty(page)))
|
|
account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
|
|
}
|
|
|
|
/*
|
|
* Delete a page from the page cache and free it. Caller has to make
|
|
* sure the page is locked and that nobody else uses it - or that usage
|
|
* is safe. The caller must hold the i_pages lock.
|
|
*/
|
|
void __delete_from_page_cache(struct page *page, void *shadow)
|
|
{
|
|
struct address_space *mapping = page->mapping;
|
|
|
|
trace_mm_filemap_delete_from_page_cache(page);
|
|
|
|
unaccount_page_cache_page(mapping, page);
|
|
page_cache_delete(mapping, page, shadow);
|
|
}
|
|
|
|
static void page_cache_free_page(struct address_space *mapping,
|
|
struct page *page)
|
|
{
|
|
void (*freepage)(struct page *);
|
|
|
|
freepage = mapping->a_ops->freepage;
|
|
if (freepage)
|
|
freepage(page);
|
|
|
|
if (PageTransHuge(page) && !PageHuge(page)) {
|
|
page_ref_sub(page, thp_nr_pages(page));
|
|
VM_BUG_ON_PAGE(page_count(page) <= 0, page);
|
|
} else {
|
|
put_page(page);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* delete_from_page_cache - delete page from page cache
|
|
* @page: the page which the kernel is trying to remove from page cache
|
|
*
|
|
* This must be called only on pages that have been verified to be in the page
|
|
* cache and locked. It will never put the page into the free list, the caller
|
|
* has a reference on the page.
|
|
*/
|
|
void delete_from_page_cache(struct page *page)
|
|
{
|
|
struct address_space *mapping = page_mapping(page);
|
|
unsigned long flags;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
xa_lock_irqsave(&mapping->i_pages, flags);
|
|
__delete_from_page_cache(page, NULL);
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
|
|
page_cache_free_page(mapping, page);
|
|
}
|
|
EXPORT_SYMBOL(delete_from_page_cache);
|
|
|
|
/*
|
|
* page_cache_delete_batch - delete several pages from page cache
|
|
* @mapping: the mapping to which pages belong
|
|
* @pvec: pagevec with pages to delete
|
|
*
|
|
* The function walks over mapping->i_pages and removes pages passed in @pvec
|
|
* from the mapping. The function expects @pvec to be sorted by page index
|
|
* and is optimised for it to be dense.
|
|
* It tolerates holes in @pvec (mapping entries at those indices are not
|
|
* modified). The function expects only THP head pages to be present in the
|
|
* @pvec.
|
|
*
|
|
* The function expects the i_pages lock to be held.
|
|
*/
|
|
static void page_cache_delete_batch(struct address_space *mapping,
|
|
struct pagevec *pvec)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, pvec->pages[0]->index);
|
|
int total_pages = 0;
|
|
int i = 0;
|
|
struct page *page;
|
|
|
|
mapping_set_update(&xas, mapping);
|
|
xas_for_each(&xas, page, ULONG_MAX) {
|
|
if (i >= pagevec_count(pvec))
|
|
break;
|
|
|
|
/* A swap/dax/shadow entry got inserted? Skip it. */
|
|
if (xa_is_value(page))
|
|
continue;
|
|
/*
|
|
* A page got inserted in our range? Skip it. We have our
|
|
* pages locked so they are protected from being removed.
|
|
* If we see a page whose index is higher than ours, it
|
|
* means our page has been removed, which shouldn't be
|
|
* possible because we're holding the PageLock.
|
|
*/
|
|
if (page != pvec->pages[i]) {
|
|
VM_BUG_ON_PAGE(page->index > pvec->pages[i]->index,
|
|
page);
|
|
continue;
|
|
}
|
|
|
|
WARN_ON_ONCE(!PageLocked(page));
|
|
|
|
if (page->index == xas.xa_index)
|
|
page->mapping = NULL;
|
|
/* Leave page->index set: truncation lookup relies on it */
|
|
|
|
/*
|
|
* Move to the next page in the vector if this is a regular
|
|
* page or the index is of the last sub-page of this compound
|
|
* page.
|
|
*/
|
|
if (page->index + compound_nr(page) - 1 == xas.xa_index)
|
|
i++;
|
|
xas_store(&xas, NULL);
|
|
total_pages++;
|
|
}
|
|
mapping->nrpages -= total_pages;
|
|
}
|
|
|
|
void delete_from_page_cache_batch(struct address_space *mapping,
|
|
struct pagevec *pvec)
|
|
{
|
|
int i;
|
|
unsigned long flags;
|
|
|
|
if (!pagevec_count(pvec))
|
|
return;
|
|
|
|
xa_lock_irqsave(&mapping->i_pages, flags);
|
|
for (i = 0; i < pagevec_count(pvec); i++) {
|
|
trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
|
|
|
|
unaccount_page_cache_page(mapping, pvec->pages[i]);
|
|
}
|
|
page_cache_delete_batch(mapping, pvec);
|
|
xa_unlock_irqrestore(&mapping->i_pages, flags);
|
|
|
|
for (i = 0; i < pagevec_count(pvec); i++)
|
|
page_cache_free_page(mapping, pvec->pages[i]);
|
|
}
|
|
|
|
int filemap_check_errors(struct address_space *mapping)
|
|
{
|
|
int ret = 0;
|
|
/* Check for outstanding write errors */
|
|
if (test_bit(AS_ENOSPC, &mapping->flags) &&
|
|
test_and_clear_bit(AS_ENOSPC, &mapping->flags))
|
|
ret = -ENOSPC;
|
|
if (test_bit(AS_EIO, &mapping->flags) &&
|
|
test_and_clear_bit(AS_EIO, &mapping->flags))
|
|
ret = -EIO;
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(filemap_check_errors);
|
|
|
|
static int filemap_check_and_keep_errors(struct address_space *mapping)
|
|
{
|
|
/* Check for outstanding write errors */
|
|
if (test_bit(AS_EIO, &mapping->flags))
|
|
return -EIO;
|
|
if (test_bit(AS_ENOSPC, &mapping->flags))
|
|
return -ENOSPC;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
|
|
* @mapping: address space structure to write
|
|
* @start: offset in bytes where the range starts
|
|
* @end: offset in bytes where the range ends (inclusive)
|
|
* @sync_mode: enable synchronous operation
|
|
*
|
|
* Start writeback against all of a mapping's dirty pages that lie
|
|
* within the byte offsets <start, end> inclusive.
|
|
*
|
|
* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
|
|
* opposed to a regular memory cleansing writeback. The difference between
|
|
* these two operations is that if a dirty page/buffer is encountered, it must
|
|
* be waited upon, and not just skipped over.
|
|
*
|
|
* Return: %0 on success, negative error code otherwise.
|
|
*/
|
|
int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
|
|
loff_t end, int sync_mode)
|
|
{
|
|
int ret;
|
|
struct writeback_control wbc = {
|
|
.sync_mode = sync_mode,
|
|
.nr_to_write = LONG_MAX,
|
|
.range_start = start,
|
|
.range_end = end,
|
|
};
|
|
|
|
if (!mapping_can_writeback(mapping) ||
|
|
!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
|
|
return 0;
|
|
|
|
wbc_attach_fdatawrite_inode(&wbc, mapping->host);
|
|
ret = do_writepages(mapping, &wbc);
|
|
wbc_detach_inode(&wbc);
|
|
return ret;
|
|
}
|
|
|
|
static inline int __filemap_fdatawrite(struct address_space *mapping,
|
|
int sync_mode)
|
|
{
|
|
return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
|
|
}
|
|
|
|
int filemap_fdatawrite(struct address_space *mapping)
|
|
{
|
|
return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawrite);
|
|
|
|
int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
|
|
loff_t end)
|
|
{
|
|
return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawrite_range);
|
|
|
|
/**
|
|
* filemap_flush - mostly a non-blocking flush
|
|
* @mapping: target address_space
|
|
*
|
|
* This is a mostly non-blocking flush. Not suitable for data-integrity
|
|
* purposes - I/O may not be started against all dirty pages.
|
|
*
|
|
* Return: %0 on success, negative error code otherwise.
|
|
*/
|
|
int filemap_flush(struct address_space *mapping)
|
|
{
|
|
return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
|
|
}
|
|
EXPORT_SYMBOL(filemap_flush);
|
|
|
|
/**
|
|
* filemap_range_has_page - check if a page exists in range.
|
|
* @mapping: address space within which to check
|
|
* @start_byte: offset in bytes where the range starts
|
|
* @end_byte: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Find at least one page in the range supplied, usually used to check if
|
|
* direct writing in this range will trigger a writeback.
|
|
*
|
|
* Return: %true if at least one page exists in the specified range,
|
|
* %false otherwise.
|
|
*/
|
|
bool filemap_range_has_page(struct address_space *mapping,
|
|
loff_t start_byte, loff_t end_byte)
|
|
{
|
|
struct page *page;
|
|
XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
|
|
pgoff_t max = end_byte >> PAGE_SHIFT;
|
|
|
|
if (end_byte < start_byte)
|
|
return false;
|
|
|
|
rcu_read_lock();
|
|
for (;;) {
|
|
page = xas_find(&xas, max);
|
|
if (xas_retry(&xas, page))
|
|
continue;
|
|
/* Shadow entries don't count */
|
|
if (xa_is_value(page))
|
|
continue;
|
|
/*
|
|
* We don't need to try to pin this page; we're about to
|
|
* release the RCU lock anyway. It is enough to know that
|
|
* there was a page here recently.
|
|
*/
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return page != NULL;
|
|
}
|
|
EXPORT_SYMBOL(filemap_range_has_page);
|
|
|
|
static void __filemap_fdatawait_range(struct address_space *mapping,
|
|
loff_t start_byte, loff_t end_byte)
|
|
{
|
|
pgoff_t index = start_byte >> PAGE_SHIFT;
|
|
pgoff_t end = end_byte >> PAGE_SHIFT;
|
|
struct pagevec pvec;
|
|
int nr_pages;
|
|
|
|
if (end_byte < start_byte)
|
|
return;
|
|
|
|
pagevec_init(&pvec);
|
|
while (index <= end) {
|
|
unsigned i;
|
|
|
|
nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
|
|
end, PAGECACHE_TAG_WRITEBACK);
|
|
if (!nr_pages)
|
|
break;
|
|
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page = pvec.pages[i];
|
|
|
|
wait_on_page_writeback(page);
|
|
ClearPageError(page);
|
|
}
|
|
pagevec_release(&pvec);
|
|
cond_resched();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* filemap_fdatawait_range - wait for writeback to complete
|
|
* @mapping: address space structure to wait for
|
|
* @start_byte: offset in bytes where the range starts
|
|
* @end_byte: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Walk the list of under-writeback pages of the given address space
|
|
* in the given range and wait for all of them. Check error status of
|
|
* the address space and return it.
|
|
*
|
|
* Since the error status of the address space is cleared by this function,
|
|
* callers are responsible for checking the return value and handling and/or
|
|
* reporting the error.
|
|
*
|
|
* Return: error status of the address space.
|
|
*/
|
|
int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
|
|
loff_t end_byte)
|
|
{
|
|
__filemap_fdatawait_range(mapping, start_byte, end_byte);
|
|
return filemap_check_errors(mapping);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawait_range);
|
|
|
|
/**
|
|
* filemap_fdatawait_range_keep_errors - wait for writeback to complete
|
|
* @mapping: address space structure to wait for
|
|
* @start_byte: offset in bytes where the range starts
|
|
* @end_byte: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Walk the list of under-writeback pages of the given address space in the
|
|
* given range and wait for all of them. Unlike filemap_fdatawait_range(),
|
|
* this function does not clear error status of the address space.
|
|
*
|
|
* Use this function if callers don't handle errors themselves. Expected
|
|
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
|
|
* fsfreeze(8)
|
|
*/
|
|
int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
|
|
loff_t start_byte, loff_t end_byte)
|
|
{
|
|
__filemap_fdatawait_range(mapping, start_byte, end_byte);
|
|
return filemap_check_and_keep_errors(mapping);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
|
|
|
|
/**
|
|
* file_fdatawait_range - wait for writeback to complete
|
|
* @file: file pointing to address space structure to wait for
|
|
* @start_byte: offset in bytes where the range starts
|
|
* @end_byte: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Walk the list of under-writeback pages of the address space that file
|
|
* refers to, in the given range and wait for all of them. Check error
|
|
* status of the address space vs. the file->f_wb_err cursor and return it.
|
|
*
|
|
* Since the error status of the file is advanced by this function,
|
|
* callers are responsible for checking the return value and handling and/or
|
|
* reporting the error.
|
|
*
|
|
* Return: error status of the address space vs. the file->f_wb_err cursor.
|
|
*/
|
|
int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
__filemap_fdatawait_range(mapping, start_byte, end_byte);
|
|
return file_check_and_advance_wb_err(file);
|
|
}
|
|
EXPORT_SYMBOL(file_fdatawait_range);
|
|
|
|
/**
|
|
* filemap_fdatawait_keep_errors - wait for writeback without clearing errors
|
|
* @mapping: address space structure to wait for
|
|
*
|
|
* Walk the list of under-writeback pages of the given address space
|
|
* and wait for all of them. Unlike filemap_fdatawait(), this function
|
|
* does not clear error status of the address space.
|
|
*
|
|
* Use this function if callers don't handle errors themselves. Expected
|
|
* call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
|
|
* fsfreeze(8)
|
|
*
|
|
* Return: error status of the address space.
|
|
*/
|
|
int filemap_fdatawait_keep_errors(struct address_space *mapping)
|
|
{
|
|
__filemap_fdatawait_range(mapping, 0, LLONG_MAX);
|
|
return filemap_check_and_keep_errors(mapping);
|
|
}
|
|
EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
|
|
|
|
/* Returns true if writeback might be needed or already in progress. */
|
|
static bool mapping_needs_writeback(struct address_space *mapping)
|
|
{
|
|
return mapping->nrpages;
|
|
}
|
|
|
|
/**
|
|
* filemap_range_needs_writeback - check if range potentially needs writeback
|
|
* @mapping: address space within which to check
|
|
* @start_byte: offset in bytes where the range starts
|
|
* @end_byte: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Find at least one page in the range supplied, usually used to check if
|
|
* direct writing in this range will trigger a writeback. Used by O_DIRECT
|
|
* read/write with IOCB_NOWAIT, to see if the caller needs to do
|
|
* filemap_write_and_wait_range() before proceeding.
|
|
*
|
|
* Return: %true if the caller should do filemap_write_and_wait_range() before
|
|
* doing O_DIRECT to a page in this range, %false otherwise.
|
|
*/
|
|
bool filemap_range_needs_writeback(struct address_space *mapping,
|
|
loff_t start_byte, loff_t end_byte)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
|
|
pgoff_t max = end_byte >> PAGE_SHIFT;
|
|
struct page *page;
|
|
|
|
if (!mapping_needs_writeback(mapping))
|
|
return false;
|
|
if (!mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
|
|
!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
|
|
return false;
|
|
if (end_byte < start_byte)
|
|
return false;
|
|
|
|
rcu_read_lock();
|
|
xas_for_each(&xas, page, max) {
|
|
if (xas_retry(&xas, page))
|
|
continue;
|
|
if (xa_is_value(page))
|
|
continue;
|
|
if (PageDirty(page) || PageLocked(page) || PageWriteback(page))
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
return page != NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(filemap_range_needs_writeback);
|
|
|
|
/**
|
|
* filemap_write_and_wait_range - write out & wait on a file range
|
|
* @mapping: the address_space for the pages
|
|
* @lstart: offset in bytes where the range starts
|
|
* @lend: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Write out and wait upon file offsets lstart->lend, inclusive.
|
|
*
|
|
* Note that @lend is inclusive (describes the last byte to be written) so
|
|
* that this function can be used to write to the very end-of-file (end = -1).
|
|
*
|
|
* Return: error status of the address space.
|
|
*/
|
|
int filemap_write_and_wait_range(struct address_space *mapping,
|
|
loff_t lstart, loff_t lend)
|
|
{
|
|
int err = 0;
|
|
|
|
if (mapping_needs_writeback(mapping)) {
|
|
err = __filemap_fdatawrite_range(mapping, lstart, lend,
|
|
WB_SYNC_ALL);
|
|
/*
|
|
* Even if the above returned error, the pages may be
|
|
* written partially (e.g. -ENOSPC), so we wait for it.
|
|
* But the -EIO is special case, it may indicate the worst
|
|
* thing (e.g. bug) happened, so we avoid waiting for it.
|
|
*/
|
|
if (err != -EIO) {
|
|
int err2 = filemap_fdatawait_range(mapping,
|
|
lstart, lend);
|
|
if (!err)
|
|
err = err2;
|
|
} else {
|
|
/* Clear any previously stored errors */
|
|
filemap_check_errors(mapping);
|
|
}
|
|
} else {
|
|
err = filemap_check_errors(mapping);
|
|
}
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(filemap_write_and_wait_range);
|
|
|
|
void __filemap_set_wb_err(struct address_space *mapping, int err)
|
|
{
|
|
errseq_t eseq = errseq_set(&mapping->wb_err, err);
|
|
|
|
trace_filemap_set_wb_err(mapping, eseq);
|
|
}
|
|
EXPORT_SYMBOL(__filemap_set_wb_err);
|
|
|
|
/**
|
|
* file_check_and_advance_wb_err - report wb error (if any) that was previously
|
|
* and advance wb_err to current one
|
|
* @file: struct file on which the error is being reported
|
|
*
|
|
* When userland calls fsync (or something like nfsd does the equivalent), we
|
|
* want to report any writeback errors that occurred since the last fsync (or
|
|
* since the file was opened if there haven't been any).
|
|
*
|
|
* Grab the wb_err from the mapping. If it matches what we have in the file,
|
|
* then just quickly return 0. The file is all caught up.
|
|
*
|
|
* If it doesn't match, then take the mapping value, set the "seen" flag in
|
|
* it and try to swap it into place. If it works, or another task beat us
|
|
* to it with the new value, then update the f_wb_err and return the error
|
|
* portion. The error at this point must be reported via proper channels
|
|
* (a'la fsync, or NFS COMMIT operation, etc.).
|
|
*
|
|
* While we handle mapping->wb_err with atomic operations, the f_wb_err
|
|
* value is protected by the f_lock since we must ensure that it reflects
|
|
* the latest value swapped in for this file descriptor.
|
|
*
|
|
* Return: %0 on success, negative error code otherwise.
|
|
*/
|
|
int file_check_and_advance_wb_err(struct file *file)
|
|
{
|
|
int err = 0;
|
|
errseq_t old = READ_ONCE(file->f_wb_err);
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
/* Locklessly handle the common case where nothing has changed */
|
|
if (errseq_check(&mapping->wb_err, old)) {
|
|
/* Something changed, must use slow path */
|
|
spin_lock(&file->f_lock);
|
|
old = file->f_wb_err;
|
|
err = errseq_check_and_advance(&mapping->wb_err,
|
|
&file->f_wb_err);
|
|
trace_file_check_and_advance_wb_err(file, old);
|
|
spin_unlock(&file->f_lock);
|
|
}
|
|
|
|
/*
|
|
* We're mostly using this function as a drop in replacement for
|
|
* filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
|
|
* that the legacy code would have had on these flags.
|
|
*/
|
|
clear_bit(AS_EIO, &mapping->flags);
|
|
clear_bit(AS_ENOSPC, &mapping->flags);
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(file_check_and_advance_wb_err);
|
|
|
|
/**
|
|
* file_write_and_wait_range - write out & wait on a file range
|
|
* @file: file pointing to address_space with pages
|
|
* @lstart: offset in bytes where the range starts
|
|
* @lend: offset in bytes where the range ends (inclusive)
|
|
*
|
|
* Write out and wait upon file offsets lstart->lend, inclusive.
|
|
*
|
|
* Note that @lend is inclusive (describes the last byte to be written) so
|
|
* that this function can be used to write to the very end-of-file (end = -1).
|
|
*
|
|
* After writing out and waiting on the data, we check and advance the
|
|
* f_wb_err cursor to the latest value, and return any errors detected there.
|
|
*
|
|
* Return: %0 on success, negative error code otherwise.
|
|
*/
|
|
int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
|
|
{
|
|
int err = 0, err2;
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
if (mapping_needs_writeback(mapping)) {
|
|
err = __filemap_fdatawrite_range(mapping, lstart, lend,
|
|
WB_SYNC_ALL);
|
|
/* See comment of filemap_write_and_wait() */
|
|
if (err != -EIO)
|
|
__filemap_fdatawait_range(mapping, lstart, lend);
|
|
}
|
|
err2 = file_check_and_advance_wb_err(file);
|
|
if (!err)
|
|
err = err2;
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL(file_write_and_wait_range);
|
|
|
|
/**
|
|
* replace_page_cache_page - replace a pagecache page with a new one
|
|
* @old: page to be replaced
|
|
* @new: page to replace with
|
|
*
|
|
* This function replaces a page in the pagecache with a new one. On
|
|
* success it acquires the pagecache reference for the new page and
|
|
* drops it for the old page. Both the old and new pages must be
|
|
* locked. This function does not add the new page to the LRU, the
|
|
* caller must do that.
|
|
*
|
|
* The remove + add is atomic. This function cannot fail.
|
|
*/
|
|
void replace_page_cache_page(struct page *old, struct page *new)
|
|
{
|
|
struct address_space *mapping = old->mapping;
|
|
void (*freepage)(struct page *) = mapping->a_ops->freepage;
|
|
pgoff_t offset = old->index;
|
|
XA_STATE(xas, &mapping->i_pages, offset);
|
|
unsigned long flags;
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(old), old);
|
|
VM_BUG_ON_PAGE(!PageLocked(new), new);
|
|
VM_BUG_ON_PAGE(new->mapping, new);
|
|
|
|
get_page(new);
|
|
new->mapping = mapping;
|
|
new->index = offset;
|
|
|
|
mem_cgroup_migrate(old, new);
|
|
|
|
xas_lock_irqsave(&xas, flags);
|
|
xas_store(&xas, new);
|
|
|
|
old->mapping = NULL;
|
|
/* hugetlb pages do not participate in page cache accounting. */
|
|
if (!PageHuge(old))
|
|
__dec_lruvec_page_state(old, NR_FILE_PAGES);
|
|
if (!PageHuge(new))
|
|
__inc_lruvec_page_state(new, NR_FILE_PAGES);
|
|
if (PageSwapBacked(old))
|
|
__dec_lruvec_page_state(old, NR_SHMEM);
|
|
if (PageSwapBacked(new))
|
|
__inc_lruvec_page_state(new, NR_SHMEM);
|
|
xas_unlock_irqrestore(&xas, flags);
|
|
if (freepage)
|
|
freepage(old);
|
|
put_page(old);
|
|
}
|
|
EXPORT_SYMBOL_GPL(replace_page_cache_page);
|
|
|
|
noinline int __add_to_page_cache_locked(struct page *page,
|
|
struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp,
|
|
void **shadowp)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, offset);
|
|
int huge = PageHuge(page);
|
|
int error;
|
|
bool charged = false;
|
|
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
VM_BUG_ON_PAGE(PageSwapBacked(page), page);
|
|
mapping_set_update(&xas, mapping);
|
|
|
|
get_page(page);
|
|
page->mapping = mapping;
|
|
page->index = offset;
|
|
|
|
if (!huge) {
|
|
error = mem_cgroup_charge(page, NULL, gfp);
|
|
if (error)
|
|
goto error;
|
|
charged = true;
|
|
}
|
|
|
|
gfp &= GFP_RECLAIM_MASK;
|
|
|
|
do {
|
|
unsigned int order = xa_get_order(xas.xa, xas.xa_index);
|
|
void *entry, *old = NULL;
|
|
|
|
if (order > thp_order(page))
|
|
xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
|
|
order, gfp);
|
|
xas_lock_irq(&xas);
|
|
xas_for_each_conflict(&xas, entry) {
|
|
old = entry;
|
|
if (!xa_is_value(entry)) {
|
|
xas_set_err(&xas, -EEXIST);
|
|
goto unlock;
|
|
}
|
|
}
|
|
|
|
if (old) {
|
|
if (shadowp)
|
|
*shadowp = old;
|
|
/* entry may have been split before we acquired lock */
|
|
order = xa_get_order(xas.xa, xas.xa_index);
|
|
if (order > thp_order(page)) {
|
|
xas_split(&xas, old, order);
|
|
xas_reset(&xas);
|
|
}
|
|
}
|
|
|
|
xas_store(&xas, page);
|
|
if (xas_error(&xas))
|
|
goto unlock;
|
|
|
|
mapping->nrpages++;
|
|
|
|
/* hugetlb pages do not participate in page cache accounting */
|
|
if (!huge)
|
|
__inc_lruvec_page_state(page, NR_FILE_PAGES);
|
|
unlock:
|
|
xas_unlock_irq(&xas);
|
|
} while (xas_nomem(&xas, gfp));
|
|
|
|
if (xas_error(&xas)) {
|
|
error = xas_error(&xas);
|
|
if (charged)
|
|
mem_cgroup_uncharge(page);
|
|
goto error;
|
|
}
|
|
|
|
trace_mm_filemap_add_to_page_cache(page);
|
|
return 0;
|
|
error:
|
|
page->mapping = NULL;
|
|
/* Leave page->index set: truncation relies upon it */
|
|
put_page(page);
|
|
return error;
|
|
}
|
|
ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO);
|
|
|
|
/**
|
|
* add_to_page_cache_locked - add a locked page to the pagecache
|
|
* @page: page to add
|
|
* @mapping: the page's address_space
|
|
* @offset: page index
|
|
* @gfp_mask: page allocation mode
|
|
*
|
|
* This function is used to add a page to the pagecache. It must be locked.
|
|
* This function does not add the page to the LRU. The caller must do that.
|
|
*
|
|
* Return: %0 on success, negative error code otherwise.
|
|
*/
|
|
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
return __add_to_page_cache_locked(page, mapping, offset,
|
|
gfp_mask, NULL);
|
|
}
|
|
EXPORT_SYMBOL(add_to_page_cache_locked);
|
|
|
|
int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
|
|
pgoff_t offset, gfp_t gfp_mask)
|
|
{
|
|
void *shadow = NULL;
|
|
int ret;
|
|
|
|
__SetPageLocked(page);
|
|
ret = __add_to_page_cache_locked(page, mapping, offset,
|
|
gfp_mask, &shadow);
|
|
if (unlikely(ret))
|
|
__ClearPageLocked(page);
|
|
else {
|
|
/*
|
|
* The page might have been evicted from cache only
|
|
* recently, in which case it should be activated like
|
|
* any other repeatedly accessed page.
|
|
* The exception is pages getting rewritten; evicting other
|
|
* data from the working set, only to cache data that will
|
|
* get overwritten with something else, is a waste of memory.
|
|
*/
|
|
WARN_ON_ONCE(PageActive(page));
|
|
if (!(gfp_mask & __GFP_WRITE) && shadow)
|
|
workingset_refault(page, shadow);
|
|
lru_cache_add(page);
|
|
}
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
|
|
|
|
#ifdef CONFIG_NUMA
|
|
struct page *__page_cache_alloc(gfp_t gfp)
|
|
{
|
|
int n;
|
|
struct page *page;
|
|
|
|
if (cpuset_do_page_mem_spread()) {
|
|
unsigned int cpuset_mems_cookie;
|
|
do {
|
|
cpuset_mems_cookie = read_mems_allowed_begin();
|
|
n = cpuset_mem_spread_node();
|
|
page = __alloc_pages_node(n, gfp, 0);
|
|
} while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
|
|
|
|
return page;
|
|
}
|
|
return alloc_pages(gfp, 0);
|
|
}
|
|
EXPORT_SYMBOL(__page_cache_alloc);
|
|
#endif
|
|
|
|
/*
|
|
* In order to wait for pages to become available there must be
|
|
* waitqueues associated with pages. By using a hash table of
|
|
* waitqueues where the bucket discipline is to maintain all
|
|
* waiters on the same queue and wake all when any of the pages
|
|
* become available, and for the woken contexts to check to be
|
|
* sure the appropriate page became available, this saves space
|
|
* at a cost of "thundering herd" phenomena during rare hash
|
|
* collisions.
|
|
*/
|
|
#define PAGE_WAIT_TABLE_BITS 8
|
|
#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
|
|
static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
|
|
|
|
static wait_queue_head_t *page_waitqueue(struct page *page)
|
|
{
|
|
return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
|
|
}
|
|
|
|
void __init pagecache_init(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
|
|
init_waitqueue_head(&page_wait_table[i]);
|
|
|
|
page_writeback_init();
|
|
}
|
|
|
|
/*
|
|
* The page wait code treats the "wait->flags" somewhat unusually, because
|
|
* we have multiple different kinds of waits, not just the usual "exclusive"
|
|
* one.
|
|
*
|
|
* We have:
|
|
*
|
|
* (a) no special bits set:
|
|
*
|
|
* We're just waiting for the bit to be released, and when a waker
|
|
* calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
|
|
* and remove it from the wait queue.
|
|
*
|
|
* Simple and straightforward.
|
|
*
|
|
* (b) WQ_FLAG_EXCLUSIVE:
|
|
*
|
|
* The waiter is waiting to get the lock, and only one waiter should
|
|
* be woken up to avoid any thundering herd behavior. We'll set the
|
|
* WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
|
|
*
|
|
* This is the traditional exclusive wait.
|
|
*
|
|
* (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
|
|
*
|
|
* The waiter is waiting to get the bit, and additionally wants the
|
|
* lock to be transferred to it for fair lock behavior. If the lock
|
|
* cannot be taken, we stop walking the wait queue without waking
|
|
* the waiter.
|
|
*
|
|
* This is the "fair lock handoff" case, and in addition to setting
|
|
* WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
|
|
* that it now has the lock.
|
|
*/
|
|
static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
|
|
{
|
|
unsigned int flags;
|
|
struct wait_page_key *key = arg;
|
|
struct wait_page_queue *wait_page
|
|
= container_of(wait, struct wait_page_queue, wait);
|
|
|
|
if (!wake_page_match(wait_page, key))
|
|
return 0;
|
|
|
|
/*
|
|
* If it's a lock handoff wait, we get the bit for it, and
|
|
* stop walking (and do not wake it up) if we can't.
|
|
*/
|
|
flags = wait->flags;
|
|
if (flags & WQ_FLAG_EXCLUSIVE) {
|
|
if (test_bit(key->bit_nr, &key->page->flags))
|
|
return -1;
|
|
if (flags & WQ_FLAG_CUSTOM) {
|
|
if (test_and_set_bit(key->bit_nr, &key->page->flags))
|
|
return -1;
|
|
flags |= WQ_FLAG_DONE;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We are holding the wait-queue lock, but the waiter that
|
|
* is waiting for this will be checking the flags without
|
|
* any locking.
|
|
*
|
|
* So update the flags atomically, and wake up the waiter
|
|
* afterwards to avoid any races. This store-release pairs
|
|
* with the load-acquire in wait_on_page_bit_common().
|
|
*/
|
|
smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
|
|
wake_up_state(wait->private, mode);
|
|
|
|
/*
|
|
* Ok, we have successfully done what we're waiting for,
|
|
* and we can unconditionally remove the wait entry.
|
|
*
|
|
* Note that this pairs with the "finish_wait()" in the
|
|
* waiter, and has to be the absolute last thing we do.
|
|
* After this list_del_init(&wait->entry) the wait entry
|
|
* might be de-allocated and the process might even have
|
|
* exited.
|
|
*/
|
|
list_del_init_careful(&wait->entry);
|
|
return (flags & WQ_FLAG_EXCLUSIVE) != 0;
|
|
}
|
|
|
|
static void wake_up_page_bit(struct page *page, int bit_nr)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
struct wait_page_key key;
|
|
unsigned long flags;
|
|
wait_queue_entry_t bookmark;
|
|
|
|
key.page = page;
|
|
key.bit_nr = bit_nr;
|
|
key.page_match = 0;
|
|
|
|
bookmark.flags = 0;
|
|
bookmark.private = NULL;
|
|
bookmark.func = NULL;
|
|
INIT_LIST_HEAD(&bookmark.entry);
|
|
|
|
spin_lock_irqsave(&q->lock, flags);
|
|
__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
|
|
|
|
while (bookmark.flags & WQ_FLAG_BOOKMARK) {
|
|
/*
|
|
* Take a breather from holding the lock,
|
|
* allow pages that finish wake up asynchronously
|
|
* to acquire the lock and remove themselves
|
|
* from wait queue
|
|
*/
|
|
spin_unlock_irqrestore(&q->lock, flags);
|
|
cpu_relax();
|
|
spin_lock_irqsave(&q->lock, flags);
|
|
__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
|
|
}
|
|
|
|
/*
|
|
* It is possible for other pages to have collided on the waitqueue
|
|
* hash, so in that case check for a page match. That prevents a long-
|
|
* term waiter
|
|
*
|
|
* It is still possible to miss a case here, when we woke page waiters
|
|
* and removed them from the waitqueue, but there are still other
|
|
* page waiters.
|
|
*/
|
|
if (!waitqueue_active(q) || !key.page_match) {
|
|
ClearPageWaiters(page);
|
|
/*
|
|
* It's possible to miss clearing Waiters here, when we woke
|
|
* our page waiters, but the hashed waitqueue has waiters for
|
|
* other pages on it.
|
|
*
|
|
* That's okay, it's a rare case. The next waker will clear it.
|
|
*/
|
|
}
|
|
spin_unlock_irqrestore(&q->lock, flags);
|
|
}
|
|
|
|
static void wake_up_page(struct page *page, int bit)
|
|
{
|
|
if (!PageWaiters(page))
|
|
return;
|
|
wake_up_page_bit(page, bit);
|
|
}
|
|
|
|
/*
|
|
* A choice of three behaviors for wait_on_page_bit_common():
|
|
*/
|
|
enum behavior {
|
|
EXCLUSIVE, /* Hold ref to page and take the bit when woken, like
|
|
* __lock_page() waiting on then setting PG_locked.
|
|
*/
|
|
SHARED, /* Hold ref to page and check the bit when woken, like
|
|
* wait_on_page_writeback() waiting on PG_writeback.
|
|
*/
|
|
DROP, /* Drop ref to page before wait, no check when woken,
|
|
* like put_and_wait_on_page_locked() on PG_locked.
|
|
*/
|
|
};
|
|
|
|
/*
|
|
* Attempt to check (or get) the page bit, and mark us done
|
|
* if successful.
|
|
*/
|
|
static inline bool trylock_page_bit_common(struct page *page, int bit_nr,
|
|
struct wait_queue_entry *wait)
|
|
{
|
|
if (wait->flags & WQ_FLAG_EXCLUSIVE) {
|
|
if (test_and_set_bit(bit_nr, &page->flags))
|
|
return false;
|
|
} else if (test_bit(bit_nr, &page->flags))
|
|
return false;
|
|
|
|
wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
|
|
return true;
|
|
}
|
|
|
|
/* How many times do we accept lock stealing from under a waiter? */
|
|
int sysctl_page_lock_unfairness = 5;
|
|
|
|
static inline int wait_on_page_bit_common(wait_queue_head_t *q,
|
|
struct page *page, int bit_nr, int state, enum behavior behavior)
|
|
{
|
|
int unfairness = sysctl_page_lock_unfairness;
|
|
struct wait_page_queue wait_page;
|
|
wait_queue_entry_t *wait = &wait_page.wait;
|
|
bool thrashing = false;
|
|
bool delayacct = false;
|
|
unsigned long pflags;
|
|
|
|
if (bit_nr == PG_locked &&
|
|
!PageUptodate(page) && PageWorkingset(page)) {
|
|
if (!PageSwapBacked(page)) {
|
|
delayacct_thrashing_start();
|
|
delayacct = true;
|
|
}
|
|
psi_memstall_enter(&pflags);
|
|
thrashing = true;
|
|
}
|
|
|
|
init_wait(wait);
|
|
wait->func = wake_page_function;
|
|
wait_page.page = page;
|
|
wait_page.bit_nr = bit_nr;
|
|
|
|
repeat:
|
|
wait->flags = 0;
|
|
if (behavior == EXCLUSIVE) {
|
|
wait->flags = WQ_FLAG_EXCLUSIVE;
|
|
if (--unfairness < 0)
|
|
wait->flags |= WQ_FLAG_CUSTOM;
|
|
}
|
|
|
|
/*
|
|
* Do one last check whether we can get the
|
|
* page bit synchronously.
|
|
*
|
|
* Do the SetPageWaiters() marking before that
|
|
* to let any waker we _just_ missed know they
|
|
* need to wake us up (otherwise they'll never
|
|
* even go to the slow case that looks at the
|
|
* page queue), and add ourselves to the wait
|
|
* queue if we need to sleep.
|
|
*
|
|
* This part needs to be done under the queue
|
|
* lock to avoid races.
|
|
*/
|
|
spin_lock_irq(&q->lock);
|
|
SetPageWaiters(page);
|
|
if (!trylock_page_bit_common(page, bit_nr, wait))
|
|
__add_wait_queue_entry_tail(q, wait);
|
|
spin_unlock_irq(&q->lock);
|
|
|
|
/*
|
|
* From now on, all the logic will be based on
|
|
* the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
|
|
* see whether the page bit testing has already
|
|
* been done by the wake function.
|
|
*
|
|
* We can drop our reference to the page.
|
|
*/
|
|
if (behavior == DROP)
|
|
put_page(page);
|
|
|
|
/*
|
|
* Note that until the "finish_wait()", or until
|
|
* we see the WQ_FLAG_WOKEN flag, we need to
|
|
* be very careful with the 'wait->flags', because
|
|
* we may race with a waker that sets them.
|
|
*/
|
|
for (;;) {
|
|
unsigned int flags;
|
|
|
|
set_current_state(state);
|
|
|
|
/* Loop until we've been woken or interrupted */
|
|
flags = smp_load_acquire(&wait->flags);
|
|
if (!(flags & WQ_FLAG_WOKEN)) {
|
|
if (signal_pending_state(state, current))
|
|
break;
|
|
|
|
io_schedule();
|
|
continue;
|
|
}
|
|
|
|
/* If we were non-exclusive, we're done */
|
|
if (behavior != EXCLUSIVE)
|
|
break;
|
|
|
|
/* If the waker got the lock for us, we're done */
|
|
if (flags & WQ_FLAG_DONE)
|
|
break;
|
|
|
|
/*
|
|
* Otherwise, if we're getting the lock, we need to
|
|
* try to get it ourselves.
|
|
*
|
|
* And if that fails, we'll have to retry this all.
|
|
*/
|
|
if (unlikely(test_and_set_bit(bit_nr, &page->flags)))
|
|
goto repeat;
|
|
|
|
wait->flags |= WQ_FLAG_DONE;
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* If a signal happened, this 'finish_wait()' may remove the last
|
|
* waiter from the wait-queues, but the PageWaiters bit will remain
|
|
* set. That's ok. The next wakeup will take care of it, and trying
|
|
* to do it here would be difficult and prone to races.
|
|
*/
|
|
finish_wait(q, wait);
|
|
|
|
if (thrashing) {
|
|
if (delayacct)
|
|
delayacct_thrashing_end();
|
|
psi_memstall_leave(&pflags);
|
|
}
|
|
|
|
/*
|
|
* NOTE! The wait->flags weren't stable until we've done the
|
|
* 'finish_wait()', and we could have exited the loop above due
|
|
* to a signal, and had a wakeup event happen after the signal
|
|
* test but before the 'finish_wait()'.
|
|
*
|
|
* So only after the finish_wait() can we reliably determine
|
|
* if we got woken up or not, so we can now figure out the final
|
|
* return value based on that state without races.
|
|
*
|
|
* Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
|
|
* waiter, but an exclusive one requires WQ_FLAG_DONE.
|
|
*/
|
|
if (behavior == EXCLUSIVE)
|
|
return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;
|
|
|
|
return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
|
|
}
|
|
|
|
void wait_on_page_bit(struct page *page, int bit_nr)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
|
|
}
|
|
EXPORT_SYMBOL(wait_on_page_bit);
|
|
|
|
int wait_on_page_bit_killable(struct page *page, int bit_nr)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, SHARED);
|
|
}
|
|
EXPORT_SYMBOL(wait_on_page_bit_killable);
|
|
|
|
/**
|
|
* put_and_wait_on_page_locked - Drop a reference and wait for it to be unlocked
|
|
* @page: The page to wait for.
|
|
* @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
|
|
*
|
|
* The caller should hold a reference on @page. They expect the page to
|
|
* become unlocked relatively soon, but do not wish to hold up migration
|
|
* (for example) by holding the reference while waiting for the page to
|
|
* come unlocked. After this function returns, the caller should not
|
|
* dereference @page.
|
|
*
|
|
* Return: 0 if the page was unlocked or -EINTR if interrupted by a signal.
|
|
*/
|
|
int put_and_wait_on_page_locked(struct page *page, int state)
|
|
{
|
|
wait_queue_head_t *q;
|
|
|
|
page = compound_head(page);
|
|
q = page_waitqueue(page);
|
|
return wait_on_page_bit_common(q, page, PG_locked, state, DROP);
|
|
}
|
|
|
|
/**
|
|
* add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
|
|
* @page: Page defining the wait queue of interest
|
|
* @waiter: Waiter to add to the queue
|
|
*
|
|
* Add an arbitrary @waiter to the wait queue for the nominated @page.
|
|
*/
|
|
void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
|
|
{
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&q->lock, flags);
|
|
__add_wait_queue_entry_tail(q, waiter);
|
|
SetPageWaiters(page);
|
|
spin_unlock_irqrestore(&q->lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(add_page_wait_queue);
|
|
|
|
#ifndef clear_bit_unlock_is_negative_byte
|
|
|
|
/*
|
|
* PG_waiters is the high bit in the same byte as PG_lock.
|
|
*
|
|
* On x86 (and on many other architectures), we can clear PG_lock and
|
|
* test the sign bit at the same time. But if the architecture does
|
|
* not support that special operation, we just do this all by hand
|
|
* instead.
|
|
*
|
|
* The read of PG_waiters has to be after (or concurrently with) PG_locked
|
|
* being cleared, but a memory barrier should be unnecessary since it is
|
|
* in the same byte as PG_locked.
|
|
*/
|
|
static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
|
|
{
|
|
clear_bit_unlock(nr, mem);
|
|
/* smp_mb__after_atomic(); */
|
|
return test_bit(PG_waiters, mem);
|
|
}
|
|
|
|
#endif
|
|
|
|
/**
|
|
* unlock_page - unlock a locked page
|
|
* @page: the page
|
|
*
|
|
* Unlocks the page and wakes up sleepers in wait_on_page_locked().
|
|
* Also wakes sleepers in wait_on_page_writeback() because the wakeup
|
|
* mechanism between PageLocked pages and PageWriteback pages is shared.
|
|
* But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
|
|
*
|
|
* Note that this depends on PG_waiters being the sign bit in the byte
|
|
* that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
|
|
* clear the PG_locked bit and test PG_waiters at the same time fairly
|
|
* portably (architectures that do LL/SC can test any bit, while x86 can
|
|
* test the sign bit).
|
|
*/
|
|
void unlock_page(struct page *page)
|
|
{
|
|
BUILD_BUG_ON(PG_waiters != 7);
|
|
page = compound_head(page);
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
|
|
wake_up_page_bit(page, PG_locked);
|
|
}
|
|
EXPORT_SYMBOL(unlock_page);
|
|
|
|
/**
|
|
* end_page_private_2 - Clear PG_private_2 and release any waiters
|
|
* @page: The page
|
|
*
|
|
* Clear the PG_private_2 bit on a page and wake up any sleepers waiting for
|
|
* this. The page ref held for PG_private_2 being set is released.
|
|
*
|
|
* This is, for example, used when a netfs page is being written to a local
|
|
* disk cache, thereby allowing writes to the cache for the same page to be
|
|
* serialised.
|
|
*/
|
|
void end_page_private_2(struct page *page)
|
|
{
|
|
page = compound_head(page);
|
|
VM_BUG_ON_PAGE(!PagePrivate2(page), page);
|
|
clear_bit_unlock(PG_private_2, &page->flags);
|
|
wake_up_page_bit(page, PG_private_2);
|
|
put_page(page);
|
|
}
|
|
EXPORT_SYMBOL(end_page_private_2);
|
|
|
|
/**
|
|
* wait_on_page_private_2 - Wait for PG_private_2 to be cleared on a page
|
|
* @page: The page to wait on
|
|
*
|
|
* Wait for PG_private_2 (aka PG_fscache) to be cleared on a page.
|
|
*/
|
|
void wait_on_page_private_2(struct page *page)
|
|
{
|
|
page = compound_head(page);
|
|
while (PagePrivate2(page))
|
|
wait_on_page_bit(page, PG_private_2);
|
|
}
|
|
EXPORT_SYMBOL(wait_on_page_private_2);
|
|
|
|
/**
|
|
* wait_on_page_private_2_killable - Wait for PG_private_2 to be cleared on a page
|
|
* @page: The page to wait on
|
|
*
|
|
* Wait for PG_private_2 (aka PG_fscache) to be cleared on a page or until a
|
|
* fatal signal is received by the calling task.
|
|
*
|
|
* Return:
|
|
* - 0 if successful.
|
|
* - -EINTR if a fatal signal was encountered.
|
|
*/
|
|
int wait_on_page_private_2_killable(struct page *page)
|
|
{
|
|
int ret = 0;
|
|
|
|
page = compound_head(page);
|
|
while (PagePrivate2(page)) {
|
|
ret = wait_on_page_bit_killable(page, PG_private_2);
|
|
if (ret < 0)
|
|
break;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(wait_on_page_private_2_killable);
|
|
|
|
/**
|
|
* end_page_writeback - end writeback against a page
|
|
* @page: the page
|
|
*/
|
|
void end_page_writeback(struct page *page)
|
|
{
|
|
/*
|
|
* TestClearPageReclaim could be used here but it is an atomic
|
|
* operation and overkill in this particular case. Failing to
|
|
* shuffle a page marked for immediate reclaim is too mild to
|
|
* justify taking an atomic operation penalty at the end of
|
|
* ever page writeback.
|
|
*/
|
|
if (PageReclaim(page)) {
|
|
ClearPageReclaim(page);
|
|
rotate_reclaimable_page(page);
|
|
}
|
|
|
|
/*
|
|
* Writeback does not hold a page reference of its own, relying
|
|
* on truncation to wait for the clearing of PG_writeback.
|
|
* But here we must make sure that the page is not freed and
|
|
* reused before the wake_up_page().
|
|
*/
|
|
get_page(page);
|
|
if (!test_clear_page_writeback(page))
|
|
BUG();
|
|
|
|
smp_mb__after_atomic();
|
|
wake_up_page(page, PG_writeback);
|
|
put_page(page);
|
|
}
|
|
EXPORT_SYMBOL(end_page_writeback);
|
|
|
|
/*
|
|
* After completing I/O on a page, call this routine to update the page
|
|
* flags appropriately
|
|
*/
|
|
void page_endio(struct page *page, bool is_write, int err)
|
|
{
|
|
if (!is_write) {
|
|
if (!err) {
|
|
SetPageUptodate(page);
|
|
} else {
|
|
ClearPageUptodate(page);
|
|
SetPageError(page);
|
|
}
|
|
unlock_page(page);
|
|
} else {
|
|
if (err) {
|
|
struct address_space *mapping;
|
|
|
|
SetPageError(page);
|
|
mapping = page_mapping(page);
|
|
if (mapping)
|
|
mapping_set_error(mapping, err);
|
|
}
|
|
end_page_writeback(page);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_endio);
|
|
|
|
/**
|
|
* __lock_page - get a lock on the page, assuming we need to sleep to get it
|
|
* @__page: the page to lock
|
|
*/
|
|
void __lock_page(struct page *__page)
|
|
{
|
|
struct page *page = compound_head(__page);
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE,
|
|
EXCLUSIVE);
|
|
}
|
|
EXPORT_SYMBOL(__lock_page);
|
|
|
|
int __lock_page_killable(struct page *__page)
|
|
{
|
|
struct page *page = compound_head(__page);
|
|
wait_queue_head_t *q = page_waitqueue(page);
|
|
return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE,
|
|
EXCLUSIVE);
|
|
}
|
|
EXPORT_SYMBOL_GPL(__lock_page_killable);
|
|
|
|
int __lock_page_async(struct page *page, struct wait_page_queue *wait)
|
|
{
|
|
struct wait_queue_head *q = page_waitqueue(page);
|
|
int ret = 0;
|
|
|
|
wait->page = page;
|
|
wait->bit_nr = PG_locked;
|
|
|
|
spin_lock_irq(&q->lock);
|
|
__add_wait_queue_entry_tail(q, &wait->wait);
|
|
SetPageWaiters(page);
|
|
ret = !trylock_page(page);
|
|
/*
|
|
* If we were successful now, we know we're still on the
|
|
* waitqueue as we're still under the lock. This means it's
|
|
* safe to remove and return success, we know the callback
|
|
* isn't going to trigger.
|
|
*/
|
|
if (!ret)
|
|
__remove_wait_queue(q, &wait->wait);
|
|
else
|
|
ret = -EIOCBQUEUED;
|
|
spin_unlock_irq(&q->lock);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Return values:
|
|
* 1 - page is locked; mmap_lock is still held.
|
|
* 0 - page is not locked.
|
|
* mmap_lock has been released (mmap_read_unlock(), unless flags had both
|
|
* FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
|
|
* which case mmap_lock is still held.
|
|
*
|
|
* If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
|
|
* with the page locked and the mmap_lock unperturbed.
|
|
*/
|
|
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
|
|
unsigned int flags)
|
|
{
|
|
if (fault_flag_allow_retry_first(flags)) {
|
|
/*
|
|
* CAUTION! In this case, mmap_lock is not released
|
|
* even though return 0.
|
|
*/
|
|
if (flags & FAULT_FLAG_RETRY_NOWAIT)
|
|
return 0;
|
|
|
|
mmap_read_unlock(mm);
|
|
if (flags & FAULT_FLAG_KILLABLE)
|
|
wait_on_page_locked_killable(page);
|
|
else
|
|
wait_on_page_locked(page);
|
|
return 0;
|
|
}
|
|
if (flags & FAULT_FLAG_KILLABLE) {
|
|
int ret;
|
|
|
|
ret = __lock_page_killable(page);
|
|
if (ret) {
|
|
mmap_read_unlock(mm);
|
|
return 0;
|
|
}
|
|
} else {
|
|
__lock_page(page);
|
|
}
|
|
return 1;
|
|
|
|
}
|
|
|
|
/**
|
|
* page_cache_next_miss() - Find the next gap in the page cache.
|
|
* @mapping: Mapping.
|
|
* @index: Index.
|
|
* @max_scan: Maximum range to search.
|
|
*
|
|
* Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
|
|
* gap with the lowest index.
|
|
*
|
|
* This function may be called under the rcu_read_lock. However, this will
|
|
* not atomically search a snapshot of the cache at a single point in time.
|
|
* For example, if a gap is created at index 5, then subsequently a gap is
|
|
* created at index 10, page_cache_next_miss covering both indices may
|
|
* return 10 if called under the rcu_read_lock.
|
|
*
|
|
* Return: The index of the gap if found, otherwise an index outside the
|
|
* range specified (in which case 'return - index >= max_scan' will be true).
|
|
* In the rare case of index wrap-around, 0 will be returned.
|
|
*/
|
|
pgoff_t page_cache_next_miss(struct address_space *mapping,
|
|
pgoff_t index, unsigned long max_scan)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, index);
|
|
|
|
while (max_scan--) {
|
|
void *entry = xas_next(&xas);
|
|
if (!entry || xa_is_value(entry))
|
|
break;
|
|
if (xas.xa_index == 0)
|
|
break;
|
|
}
|
|
|
|
return xas.xa_index;
|
|
}
|
|
EXPORT_SYMBOL(page_cache_next_miss);
|
|
|
|
/**
|
|
* page_cache_prev_miss() - Find the previous gap in the page cache.
|
|
* @mapping: Mapping.
|
|
* @index: Index.
|
|
* @max_scan: Maximum range to search.
|
|
*
|
|
* Search the range [max(index - max_scan + 1, 0), index] for the
|
|
* gap with the highest index.
|
|
*
|
|
* This function may be called under the rcu_read_lock. However, this will
|
|
* not atomically search a snapshot of the cache at a single point in time.
|
|
* For example, if a gap is created at index 10, then subsequently a gap is
|
|
* created at index 5, page_cache_prev_miss() covering both indices may
|
|
* return 5 if called under the rcu_read_lock.
|
|
*
|
|
* Return: The index of the gap if found, otherwise an index outside the
|
|
* range specified (in which case 'index - return >= max_scan' will be true).
|
|
* In the rare case of wrap-around, ULONG_MAX will be returned.
|
|
*/
|
|
pgoff_t page_cache_prev_miss(struct address_space *mapping,
|
|
pgoff_t index, unsigned long max_scan)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, index);
|
|
|
|
while (max_scan--) {
|
|
void *entry = xas_prev(&xas);
|
|
if (!entry || xa_is_value(entry))
|
|
break;
|
|
if (xas.xa_index == ULONG_MAX)
|
|
break;
|
|
}
|
|
|
|
return xas.xa_index;
|
|
}
|
|
EXPORT_SYMBOL(page_cache_prev_miss);
|
|
|
|
/*
|
|
* mapping_get_entry - Get a page cache entry.
|
|
* @mapping: the address_space to search
|
|
* @index: The page cache index.
|
|
*
|
|
* Looks up the page cache slot at @mapping & @index. If there is a
|
|
* page cache page, the head page is returned with an increased refcount.
|
|
*
|
|
* If the slot holds a shadow entry of a previously evicted page, or a
|
|
* swap entry from shmem/tmpfs, it is returned.
|
|
*
|
|
* Return: The head page or shadow entry, %NULL if nothing is found.
|
|
*/
|
|
static struct page *mapping_get_entry(struct address_space *mapping,
|
|
pgoff_t index)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, index);
|
|
struct page *page;
|
|
|
|
rcu_read_lock();
|
|
repeat:
|
|
xas_reset(&xas);
|
|
page = xas_load(&xas);
|
|
if (xas_retry(&xas, page))
|
|
goto repeat;
|
|
/*
|
|
* A shadow entry of a recently evicted page, or a swap entry from
|
|
* shmem/tmpfs. Return it without attempting to raise page count.
|
|
*/
|
|
if (!page || xa_is_value(page))
|
|
goto out;
|
|
|
|
if (!page_cache_get_speculative(page))
|
|
goto repeat;
|
|
|
|
/*
|
|
* Has the page moved or been split?
|
|
* This is part of the lockless pagecache protocol. See
|
|
* include/linux/pagemap.h for details.
|
|
*/
|
|
if (unlikely(page != xas_reload(&xas))) {
|
|
put_page(page);
|
|
goto repeat;
|
|
}
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return page;
|
|
}
|
|
|
|
/**
|
|
* pagecache_get_page - Find and get a reference to a page.
|
|
* @mapping: The address_space to search.
|
|
* @index: The page index.
|
|
* @fgp_flags: %FGP flags modify how the page is returned.
|
|
* @gfp_mask: Memory allocation flags to use if %FGP_CREAT is specified.
|
|
*
|
|
* Looks up the page cache entry at @mapping & @index.
|
|
*
|
|
* @fgp_flags can be zero or more of these flags:
|
|
*
|
|
* * %FGP_ACCESSED - The page will be marked accessed.
|
|
* * %FGP_LOCK - The page is returned locked.
|
|
* * %FGP_HEAD - If the page is present and a THP, return the head page
|
|
* rather than the exact page specified by the index.
|
|
* * %FGP_ENTRY - If there is a shadow / swap / DAX entry, return it
|
|
* instead of allocating a new page to replace it.
|
|
* * %FGP_CREAT - If no page is present then a new page is allocated using
|
|
* @gfp_mask and added to the page cache and the VM's LRU list.
|
|
* The page is returned locked and with an increased refcount.
|
|
* * %FGP_FOR_MMAP - The caller wants to do its own locking dance if the
|
|
* page is already in cache. If the page was allocated, unlock it before
|
|
* returning so the caller can do the same dance.
|
|
* * %FGP_WRITE - The page will be written
|
|
* * %FGP_NOFS - __GFP_FS will get cleared in gfp mask
|
|
* * %FGP_NOWAIT - Don't get blocked by page lock
|
|
*
|
|
* If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
|
|
* if the %GFP flags specified for %FGP_CREAT are atomic.
|
|
*
|
|
* If there is a page cache page, it is returned with an increased refcount.
|
|
*
|
|
* Return: The found page or %NULL otherwise.
|
|
*/
|
|
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index,
|
|
int fgp_flags, gfp_t gfp_mask)
|
|
{
|
|
struct page *page;
|
|
|
|
repeat:
|
|
page = mapping_get_entry(mapping, index);
|
|
if (xa_is_value(page)) {
|
|
if (fgp_flags & FGP_ENTRY)
|
|
return page;
|
|
page = NULL;
|
|
}
|
|
if (!page)
|
|
goto no_page;
|
|
|
|
if (fgp_flags & FGP_LOCK) {
|
|
if (fgp_flags & FGP_NOWAIT) {
|
|
if (!trylock_page(page)) {
|
|
put_page(page);
|
|
return NULL;
|
|
}
|
|
} else {
|
|
lock_page(page);
|
|
}
|
|
|
|
/* Has the page been truncated? */
|
|
if (unlikely(page->mapping != mapping)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto repeat;
|
|
}
|
|
VM_BUG_ON_PAGE(!thp_contains(page, index), page);
|
|
}
|
|
|
|
if (fgp_flags & FGP_ACCESSED)
|
|
mark_page_accessed(page);
|
|
else if (fgp_flags & FGP_WRITE) {
|
|
/* Clear idle flag for buffer write */
|
|
if (page_is_idle(page))
|
|
clear_page_idle(page);
|
|
}
|
|
if (!(fgp_flags & FGP_HEAD))
|
|
page = find_subpage(page, index);
|
|
|
|
no_page:
|
|
if (!page && (fgp_flags & FGP_CREAT)) {
|
|
int err;
|
|
if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
|
|
gfp_mask |= __GFP_WRITE;
|
|
if (fgp_flags & FGP_NOFS)
|
|
gfp_mask &= ~__GFP_FS;
|
|
|
|
page = __page_cache_alloc(gfp_mask);
|
|
if (!page)
|
|
return NULL;
|
|
|
|
if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
|
|
fgp_flags |= FGP_LOCK;
|
|
|
|
/* Init accessed so avoid atomic mark_page_accessed later */
|
|
if (fgp_flags & FGP_ACCESSED)
|
|
__SetPageReferenced(page);
|
|
|
|
err = add_to_page_cache_lru(page, mapping, index, gfp_mask);
|
|
if (unlikely(err)) {
|
|
put_page(page);
|
|
page = NULL;
|
|
if (err == -EEXIST)
|
|
goto repeat;
|
|
}
|
|
|
|
/*
|
|
* add_to_page_cache_lru locks the page, and for mmap we expect
|
|
* an unlocked page.
|
|
*/
|
|
if (page && (fgp_flags & FGP_FOR_MMAP))
|
|
unlock_page(page);
|
|
}
|
|
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(pagecache_get_page);
|
|
|
|
static inline struct page *find_get_entry(struct xa_state *xas, pgoff_t max,
|
|
xa_mark_t mark)
|
|
{
|
|
struct page *page;
|
|
|
|
retry:
|
|
if (mark == XA_PRESENT)
|
|
page = xas_find(xas, max);
|
|
else
|
|
page = xas_find_marked(xas, max, mark);
|
|
|
|
if (xas_retry(xas, page))
|
|
goto retry;
|
|
/*
|
|
* A shadow entry of a recently evicted page, a swap
|
|
* entry from shmem/tmpfs or a DAX entry. Return it
|
|
* without attempting to raise page count.
|
|
*/
|
|
if (!page || xa_is_value(page))
|
|
return page;
|
|
|
|
if (!page_cache_get_speculative(page))
|
|
goto reset;
|
|
|
|
/* Has the page moved or been split? */
|
|
if (unlikely(page != xas_reload(xas))) {
|
|
put_page(page);
|
|
goto reset;
|
|
}
|
|
|
|
return page;
|
|
reset:
|
|
xas_reset(xas);
|
|
goto retry;
|
|
}
|
|
|
|
/**
|
|
* find_get_entries - gang pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @start: The starting page cache index
|
|
* @end: The final page index (inclusive).
|
|
* @pvec: Where the resulting entries are placed.
|
|
* @indices: The cache indices corresponding to the entries in @entries
|
|
*
|
|
* find_get_entries() will search for and return a batch of entries in
|
|
* the mapping. The entries are placed in @pvec. find_get_entries()
|
|
* takes a reference on any actual pages it returns.
|
|
*
|
|
* The search returns a group of mapping-contiguous page cache entries
|
|
* with ascending indexes. There may be holes in the indices due to
|
|
* not-present pages.
|
|
*
|
|
* Any shadow entries of evicted pages, or swap entries from
|
|
* shmem/tmpfs, are included in the returned array.
|
|
*
|
|
* If it finds a Transparent Huge Page, head or tail, find_get_entries()
|
|
* stops at that page: the caller is likely to have a better way to handle
|
|
* the compound page as a whole, and then skip its extent, than repeatedly
|
|
* calling find_get_entries() to return all its tails.
|
|
*
|
|
* Return: the number of pages and shadow entries which were found.
|
|
*/
|
|
unsigned find_get_entries(struct address_space *mapping, pgoff_t start,
|
|
pgoff_t end, struct pagevec *pvec, pgoff_t *indices)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, start);
|
|
struct page *page;
|
|
unsigned int ret = 0;
|
|
unsigned nr_entries = PAGEVEC_SIZE;
|
|
|
|
rcu_read_lock();
|
|
while ((page = find_get_entry(&xas, end, XA_PRESENT))) {
|
|
/*
|
|
* Terminate early on finding a THP, to allow the caller to
|
|
* handle it all at once; but continue if this is hugetlbfs.
|
|
*/
|
|
if (!xa_is_value(page) && PageTransHuge(page) &&
|
|
!PageHuge(page)) {
|
|
page = find_subpage(page, xas.xa_index);
|
|
nr_entries = ret + 1;
|
|
}
|
|
|
|
indices[ret] = xas.xa_index;
|
|
pvec->pages[ret] = page;
|
|
if (++ret == nr_entries)
|
|
break;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
pvec->nr = ret;
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* find_lock_entries - Find a batch of pagecache entries.
|
|
* @mapping: The address_space to search.
|
|
* @start: The starting page cache index.
|
|
* @end: The final page index (inclusive).
|
|
* @pvec: Where the resulting entries are placed.
|
|
* @indices: The cache indices of the entries in @pvec.
|
|
*
|
|
* find_lock_entries() will return a batch of entries from @mapping.
|
|
* Swap, shadow and DAX entries are included. Pages are returned
|
|
* locked and with an incremented refcount. Pages which are locked by
|
|
* somebody else or under writeback are skipped. Only the head page of
|
|
* a THP is returned. Pages which are partially outside the range are
|
|
* not returned.
|
|
*
|
|
* The entries have ascending indexes. The indices may not be consecutive
|
|
* due to not-present entries, THP pages, pages which could not be locked
|
|
* or pages under writeback.
|
|
*
|
|
* Return: The number of entries which were found.
|
|
*/
|
|
unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
|
|
pgoff_t end, struct pagevec *pvec, pgoff_t *indices)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, start);
|
|
struct page *page;
|
|
|
|
rcu_read_lock();
|
|
while ((page = find_get_entry(&xas, end, XA_PRESENT))) {
|
|
if (!xa_is_value(page)) {
|
|
if (page->index < start)
|
|
goto put;
|
|
VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
|
|
if (page->index + thp_nr_pages(page) - 1 > end)
|
|
goto put;
|
|
if (!trylock_page(page))
|
|
goto put;
|
|
if (page->mapping != mapping || PageWriteback(page))
|
|
goto unlock;
|
|
VM_BUG_ON_PAGE(!thp_contains(page, xas.xa_index),
|
|
page);
|
|
}
|
|
indices[pvec->nr] = xas.xa_index;
|
|
if (!pagevec_add(pvec, page))
|
|
break;
|
|
goto next;
|
|
unlock:
|
|
unlock_page(page);
|
|
put:
|
|
put_page(page);
|
|
next:
|
|
if (!xa_is_value(page) && PageTransHuge(page)) {
|
|
unsigned int nr_pages = thp_nr_pages(page);
|
|
|
|
/* Final THP may cross MAX_LFS_FILESIZE on 32-bit */
|
|
xas_set(&xas, page->index + nr_pages);
|
|
if (xas.xa_index < nr_pages)
|
|
break;
|
|
}
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return pagevec_count(pvec);
|
|
}
|
|
|
|
/**
|
|
* find_get_pages_range - gang pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @start: The starting page index
|
|
* @end: The final page index (inclusive)
|
|
* @nr_pages: The maximum number of pages
|
|
* @pages: Where the resulting pages are placed
|
|
*
|
|
* find_get_pages_range() will search for and return a group of up to @nr_pages
|
|
* pages in the mapping starting at index @start and up to index @end
|
|
* (inclusive). The pages are placed at @pages. find_get_pages_range() takes
|
|
* a reference against the returned pages.
|
|
*
|
|
* The search returns a group of mapping-contiguous pages with ascending
|
|
* indexes. There may be holes in the indices due to not-present pages.
|
|
* We also update @start to index the next page for the traversal.
|
|
*
|
|
* Return: the number of pages which were found. If this number is
|
|
* smaller than @nr_pages, the end of specified range has been
|
|
* reached.
|
|
*/
|
|
unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
|
|
pgoff_t end, unsigned int nr_pages,
|
|
struct page **pages)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, *start);
|
|
struct page *page;
|
|
unsigned ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
while ((page = find_get_entry(&xas, end, XA_PRESENT))) {
|
|
/* Skip over shadow, swap and DAX entries */
|
|
if (xa_is_value(page))
|
|
continue;
|
|
|
|
pages[ret] = find_subpage(page, xas.xa_index);
|
|
if (++ret == nr_pages) {
|
|
*start = xas.xa_index + 1;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We come here when there is no page beyond @end. We take care to not
|
|
* overflow the index @start as it confuses some of the callers. This
|
|
* breaks the iteration when there is a page at index -1 but that is
|
|
* already broken anyway.
|
|
*/
|
|
if (end == (pgoff_t)-1)
|
|
*start = (pgoff_t)-1;
|
|
else
|
|
*start = end + 1;
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* find_get_pages_contig - gang contiguous pagecache lookup
|
|
* @mapping: The address_space to search
|
|
* @index: The starting page index
|
|
* @nr_pages: The maximum number of pages
|
|
* @pages: Where the resulting pages are placed
|
|
*
|
|
* find_get_pages_contig() works exactly like find_get_pages(), except
|
|
* that the returned number of pages are guaranteed to be contiguous.
|
|
*
|
|
* Return: the number of pages which were found.
|
|
*/
|
|
unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
|
|
unsigned int nr_pages, struct page **pages)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, index);
|
|
struct page *page;
|
|
unsigned int ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
for (page = xas_load(&xas); page; page = xas_next(&xas)) {
|
|
if (xas_retry(&xas, page))
|
|
continue;
|
|
/*
|
|
* If the entry has been swapped out, we can stop looking.
|
|
* No current caller is looking for DAX entries.
|
|
*/
|
|
if (xa_is_value(page))
|
|
break;
|
|
|
|
if (!page_cache_get_speculative(page))
|
|
goto retry;
|
|
|
|
/* Has the page moved or been split? */
|
|
if (unlikely(page != xas_reload(&xas)))
|
|
goto put_page;
|
|
|
|
pages[ret] = find_subpage(page, xas.xa_index);
|
|
if (++ret == nr_pages)
|
|
break;
|
|
continue;
|
|
put_page:
|
|
put_page(page);
|
|
retry:
|
|
xas_reset(&xas);
|
|
}
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_pages_contig);
|
|
|
|
/**
|
|
* find_get_pages_range_tag - Find and return head pages matching @tag.
|
|
* @mapping: the address_space to search
|
|
* @index: the starting page index
|
|
* @end: The final page index (inclusive)
|
|
* @tag: the tag index
|
|
* @nr_pages: the maximum number of pages
|
|
* @pages: where the resulting pages are placed
|
|
*
|
|
* Like find_get_pages(), except we only return head pages which are tagged
|
|
* with @tag. @index is updated to the index immediately after the last
|
|
* page we return, ready for the next iteration.
|
|
*
|
|
* Return: the number of pages which were found.
|
|
*/
|
|
unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
|
|
pgoff_t end, xa_mark_t tag, unsigned int nr_pages,
|
|
struct page **pages)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, *index);
|
|
struct page *page;
|
|
unsigned ret = 0;
|
|
|
|
if (unlikely(!nr_pages))
|
|
return 0;
|
|
|
|
rcu_read_lock();
|
|
while ((page = find_get_entry(&xas, end, tag))) {
|
|
/*
|
|
* Shadow entries should never be tagged, but this iteration
|
|
* is lockless so there is a window for page reclaim to evict
|
|
* a page we saw tagged. Skip over it.
|
|
*/
|
|
if (xa_is_value(page))
|
|
continue;
|
|
|
|
pages[ret] = page;
|
|
if (++ret == nr_pages) {
|
|
*index = page->index + thp_nr_pages(page);
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* We come here when we got to @end. We take care to not overflow the
|
|
* index @index as it confuses some of the callers. This breaks the
|
|
* iteration when there is a page at index -1 but that is already
|
|
* broken anyway.
|
|
*/
|
|
if (end == (pgoff_t)-1)
|
|
*index = (pgoff_t)-1;
|
|
else
|
|
*index = end + 1;
|
|
out:
|
|
rcu_read_unlock();
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(find_get_pages_range_tag);
|
|
|
|
/*
|
|
* CD/DVDs are error prone. When a medium error occurs, the driver may fail
|
|
* a _large_ part of the i/o request. Imagine the worst scenario:
|
|
*
|
|
* ---R__________________________________________B__________
|
|
* ^ reading here ^ bad block(assume 4k)
|
|
*
|
|
* read(R) => miss => readahead(R...B) => media error => frustrating retries
|
|
* => failing the whole request => read(R) => read(R+1) =>
|
|
* readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
|
|
* readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
|
|
* readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
|
|
*
|
|
* It is going insane. Fix it by quickly scaling down the readahead size.
|
|
*/
|
|
static void shrink_readahead_size_eio(struct file_ra_state *ra)
|
|
{
|
|
ra->ra_pages /= 4;
|
|
}
|
|
|
|
/*
|
|
* filemap_get_read_batch - Get a batch of pages for read
|
|
*
|
|
* Get a batch of pages which represent a contiguous range of bytes
|
|
* in the file. No tail pages will be returned. If @index is in the
|
|
* middle of a THP, the entire THP will be returned. The last page in
|
|
* the batch may have Readahead set or be not Uptodate so that the
|
|
* caller can take the appropriate action.
|
|
*/
|
|
static void filemap_get_read_batch(struct address_space *mapping,
|
|
pgoff_t index, pgoff_t max, struct pagevec *pvec)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, index);
|
|
struct page *head;
|
|
|
|
rcu_read_lock();
|
|
for (head = xas_load(&xas); head; head = xas_next(&xas)) {
|
|
if (xas_retry(&xas, head))
|
|
continue;
|
|
if (xas.xa_index > max || xa_is_value(head))
|
|
break;
|
|
if (!page_cache_get_speculative(head))
|
|
goto retry;
|
|
|
|
/* Has the page moved or been split? */
|
|
if (unlikely(head != xas_reload(&xas)))
|
|
goto put_page;
|
|
|
|
if (!pagevec_add(pvec, head))
|
|
break;
|
|
if (!PageUptodate(head))
|
|
break;
|
|
if (PageReadahead(head))
|
|
break;
|
|
xas.xa_index = head->index + thp_nr_pages(head) - 1;
|
|
xas.xa_offset = (xas.xa_index >> xas.xa_shift) & XA_CHUNK_MASK;
|
|
continue;
|
|
put_page:
|
|
put_page(head);
|
|
retry:
|
|
xas_reset(&xas);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
static int filemap_read_page(struct file *file, struct address_space *mapping,
|
|
struct page *page)
|
|
{
|
|
int error;
|
|
|
|
/*
|
|
* A previous I/O error may have been due to temporary failures,
|
|
* eg. multipath errors. PG_error will be set again if readpage
|
|
* fails.
|
|
*/
|
|
ClearPageError(page);
|
|
/* Start the actual read. The read will unlock the page. */
|
|
error = mapping->a_ops->readpage(file, page);
|
|
if (error)
|
|
return error;
|
|
|
|
error = wait_on_page_locked_killable(page);
|
|
if (error)
|
|
return error;
|
|
if (PageUptodate(page))
|
|
return 0;
|
|
shrink_readahead_size_eio(&file->f_ra);
|
|
return -EIO;
|
|
}
|
|
|
|
static bool filemap_range_uptodate(struct address_space *mapping,
|
|
loff_t pos, struct iov_iter *iter, struct page *page)
|
|
{
|
|
int count;
|
|
|
|
if (PageUptodate(page))
|
|
return true;
|
|
/* pipes can't handle partially uptodate pages */
|
|
if (iov_iter_is_pipe(iter))
|
|
return false;
|
|
if (!mapping->a_ops->is_partially_uptodate)
|
|
return false;
|
|
if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page)))
|
|
return false;
|
|
|
|
count = iter->count;
|
|
if (page_offset(page) > pos) {
|
|
count -= page_offset(page) - pos;
|
|
pos = 0;
|
|
} else {
|
|
pos -= page_offset(page);
|
|
}
|
|
|
|
return mapping->a_ops->is_partially_uptodate(page, pos, count);
|
|
}
|
|
|
|
static int filemap_update_page(struct kiocb *iocb,
|
|
struct address_space *mapping, struct iov_iter *iter,
|
|
struct page *page)
|
|
{
|
|
int error;
|
|
|
|
if (!trylock_page(page)) {
|
|
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
|
|
return -EAGAIN;
|
|
if (!(iocb->ki_flags & IOCB_WAITQ)) {
|
|
put_and_wait_on_page_locked(page, TASK_KILLABLE);
|
|
return AOP_TRUNCATED_PAGE;
|
|
}
|
|
error = __lock_page_async(page, iocb->ki_waitq);
|
|
if (error)
|
|
return error;
|
|
}
|
|
|
|
if (!page->mapping)
|
|
goto truncated;
|
|
|
|
error = 0;
|
|
if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page))
|
|
goto unlock;
|
|
|
|
error = -EAGAIN;
|
|
if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
|
|
goto unlock;
|
|
|
|
error = filemap_read_page(iocb->ki_filp, mapping, page);
|
|
if (error == AOP_TRUNCATED_PAGE)
|
|
put_page(page);
|
|
return error;
|
|
truncated:
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return AOP_TRUNCATED_PAGE;
|
|
unlock:
|
|
unlock_page(page);
|
|
return error;
|
|
}
|
|
|
|
static int filemap_create_page(struct file *file,
|
|
struct address_space *mapping, pgoff_t index,
|
|
struct pagevec *pvec)
|
|
{
|
|
struct page *page;
|
|
int error;
|
|
|
|
page = page_cache_alloc(mapping);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
error = add_to_page_cache_lru(page, mapping, index,
|
|
mapping_gfp_constraint(mapping, GFP_KERNEL));
|
|
if (error == -EEXIST)
|
|
error = AOP_TRUNCATED_PAGE;
|
|
if (error)
|
|
goto error;
|
|
|
|
error = filemap_read_page(file, mapping, page);
|
|
if (error)
|
|
goto error;
|
|
|
|
pagevec_add(pvec, page);
|
|
return 0;
|
|
error:
|
|
put_page(page);
|
|
return error;
|
|
}
|
|
|
|
static int filemap_readahead(struct kiocb *iocb, struct file *file,
|
|
struct address_space *mapping, struct page *page,
|
|
pgoff_t last_index)
|
|
{
|
|
if (iocb->ki_flags & IOCB_NOIO)
|
|
return -EAGAIN;
|
|
page_cache_async_readahead(mapping, &file->f_ra, file, page,
|
|
page->index, last_index - page->index);
|
|
return 0;
|
|
}
|
|
|
|
static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
|
|
struct pagevec *pvec)
|
|
{
|
|
struct file *filp = iocb->ki_filp;
|
|
struct address_space *mapping = filp->f_mapping;
|
|
struct file_ra_state *ra = &filp->f_ra;
|
|
pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
|
|
pgoff_t last_index;
|
|
struct page *page;
|
|
int err = 0;
|
|
|
|
last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE);
|
|
retry:
|
|
if (fatal_signal_pending(current))
|
|
return -EINTR;
|
|
|
|
filemap_get_read_batch(mapping, index, last_index, pvec);
|
|
if (!pagevec_count(pvec)) {
|
|
if (iocb->ki_flags & IOCB_NOIO)
|
|
return -EAGAIN;
|
|
page_cache_sync_readahead(mapping, ra, filp, index,
|
|
last_index - index);
|
|
filemap_get_read_batch(mapping, index, last_index, pvec);
|
|
}
|
|
if (!pagevec_count(pvec)) {
|
|
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
|
|
return -EAGAIN;
|
|
err = filemap_create_page(filp, mapping,
|
|
iocb->ki_pos >> PAGE_SHIFT, pvec);
|
|
if (err == AOP_TRUNCATED_PAGE)
|
|
goto retry;
|
|
return err;
|
|
}
|
|
|
|
page = pvec->pages[pagevec_count(pvec) - 1];
|
|
if (PageReadahead(page)) {
|
|
err = filemap_readahead(iocb, filp, mapping, page, last_index);
|
|
if (err)
|
|
goto err;
|
|
}
|
|
if (!PageUptodate(page)) {
|
|
if ((iocb->ki_flags & IOCB_WAITQ) && pagevec_count(pvec) > 1)
|
|
iocb->ki_flags |= IOCB_NOWAIT;
|
|
err = filemap_update_page(iocb, mapping, iter, page);
|
|
if (err)
|
|
goto err;
|
|
}
|
|
|
|
return 0;
|
|
err:
|
|
if (err < 0)
|
|
put_page(page);
|
|
if (likely(--pvec->nr))
|
|
return 0;
|
|
if (err == AOP_TRUNCATED_PAGE)
|
|
goto retry;
|
|
return err;
|
|
}
|
|
|
|
/**
|
|
* filemap_read - Read data from the page cache.
|
|
* @iocb: The iocb to read.
|
|
* @iter: Destination for the data.
|
|
* @already_read: Number of bytes already read by the caller.
|
|
*
|
|
* Copies data from the page cache. If the data is not currently present,
|
|
* uses the readahead and readpage address_space operations to fetch it.
|
|
*
|
|
* Return: Total number of bytes copied, including those already read by
|
|
* the caller. If an error happens before any bytes are copied, returns
|
|
* a negative error number.
|
|
*/
|
|
ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
|
|
ssize_t already_read)
|
|
{
|
|
struct file *filp = iocb->ki_filp;
|
|
struct file_ra_state *ra = &filp->f_ra;
|
|
struct address_space *mapping = filp->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
struct pagevec pvec;
|
|
int i, error = 0;
|
|
bool writably_mapped;
|
|
loff_t isize, end_offset;
|
|
|
|
if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
|
|
return 0;
|
|
if (unlikely(!iov_iter_count(iter)))
|
|
return 0;
|
|
|
|
iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
|
|
pagevec_init(&pvec);
|
|
|
|
do {
|
|
cond_resched();
|
|
|
|
/*
|
|
* If we've already successfully copied some data, then we
|
|
* can no longer safely return -EIOCBQUEUED. Hence mark
|
|
* an async read NOWAIT at that point.
|
|
*/
|
|
if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
|
|
iocb->ki_flags |= IOCB_NOWAIT;
|
|
|
|
error = filemap_get_pages(iocb, iter, &pvec);
|
|
if (error < 0)
|
|
break;
|
|
|
|
/*
|
|
* i_size must be checked after we know the pages are Uptodate.
|
|
*
|
|
* Checking i_size after the check allows us to calculate
|
|
* the correct value for "nr", which means the zero-filled
|
|
* part of the page is not copied back to userspace (unless
|
|
* another truncate extends the file - this is desired though).
|
|
*/
|
|
isize = i_size_read(inode);
|
|
if (unlikely(iocb->ki_pos >= isize))
|
|
goto put_pages;
|
|
end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
|
|
|
|
/*
|
|
* Once we start copying data, we don't want to be touching any
|
|
* cachelines that might be contended:
|
|
*/
|
|
writably_mapped = mapping_writably_mapped(mapping);
|
|
|
|
/*
|
|
* When a sequential read accesses a page several times, only
|
|
* mark it as accessed the first time.
|
|
*/
|
|
if (iocb->ki_pos >> PAGE_SHIFT !=
|
|
ra->prev_pos >> PAGE_SHIFT)
|
|
mark_page_accessed(pvec.pages[0]);
|
|
|
|
for (i = 0; i < pagevec_count(&pvec); i++) {
|
|
struct page *page = pvec.pages[i];
|
|
size_t page_size = thp_size(page);
|
|
size_t offset = iocb->ki_pos & (page_size - 1);
|
|
size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
|
|
page_size - offset);
|
|
size_t copied;
|
|
|
|
if (end_offset < page_offset(page))
|
|
break;
|
|
if (i > 0)
|
|
mark_page_accessed(page);
|
|
/*
|
|
* If users can be writing to this page using arbitrary
|
|
* virtual addresses, take care about potential aliasing
|
|
* before reading the page on the kernel side.
|
|
*/
|
|
if (writably_mapped) {
|
|
int j;
|
|
|
|
for (j = 0; j < thp_nr_pages(page); j++)
|
|
flush_dcache_page(page + j);
|
|
}
|
|
|
|
copied = copy_page_to_iter(page, offset, bytes, iter);
|
|
|
|
already_read += copied;
|
|
iocb->ki_pos += copied;
|
|
ra->prev_pos = iocb->ki_pos;
|
|
|
|
if (copied < bytes) {
|
|
error = -EFAULT;
|
|
break;
|
|
}
|
|
}
|
|
put_pages:
|
|
for (i = 0; i < pagevec_count(&pvec); i++)
|
|
put_page(pvec.pages[i]);
|
|
pagevec_reinit(&pvec);
|
|
} while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);
|
|
|
|
file_accessed(filp);
|
|
|
|
return already_read ? already_read : error;
|
|
}
|
|
EXPORT_SYMBOL_GPL(filemap_read);
|
|
|
|
/**
|
|
* generic_file_read_iter - generic filesystem read routine
|
|
* @iocb: kernel I/O control block
|
|
* @iter: destination for the data read
|
|
*
|
|
* This is the "read_iter()" routine for all filesystems
|
|
* that can use the page cache directly.
|
|
*
|
|
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
|
|
* be returned when no data can be read without waiting for I/O requests
|
|
* to complete; it doesn't prevent readahead.
|
|
*
|
|
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
|
|
* requests shall be made for the read or for readahead. When no data
|
|
* can be read, -EAGAIN shall be returned. When readahead would be
|
|
* triggered, a partial, possibly empty read shall be returned.
|
|
*
|
|
* Return:
|
|
* * number of bytes copied, even for partial reads
|
|
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
|
|
*/
|
|
ssize_t
|
|
generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
|
|
{
|
|
size_t count = iov_iter_count(iter);
|
|
ssize_t retval = 0;
|
|
|
|
if (!count)
|
|
return 0; /* skip atime */
|
|
|
|
if (iocb->ki_flags & IOCB_DIRECT) {
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
loff_t size;
|
|
|
|
size = i_size_read(inode);
|
|
if (iocb->ki_flags & IOCB_NOWAIT) {
|
|
if (filemap_range_needs_writeback(mapping, iocb->ki_pos,
|
|
iocb->ki_pos + count - 1))
|
|
return -EAGAIN;
|
|
} else {
|
|
retval = filemap_write_and_wait_range(mapping,
|
|
iocb->ki_pos,
|
|
iocb->ki_pos + count - 1);
|
|
if (retval < 0)
|
|
return retval;
|
|
}
|
|
|
|
file_accessed(file);
|
|
|
|
retval = mapping->a_ops->direct_IO(iocb, iter);
|
|
if (retval >= 0) {
|
|
iocb->ki_pos += retval;
|
|
count -= retval;
|
|
}
|
|
if (retval != -EIOCBQUEUED)
|
|
iov_iter_revert(iter, count - iov_iter_count(iter));
|
|
|
|
/*
|
|
* Btrfs can have a short DIO read if we encounter
|
|
* compressed extents, so if there was an error, or if
|
|
* we've already read everything we wanted to, or if
|
|
* there was a short read because we hit EOF, go ahead
|
|
* and return. Otherwise fallthrough to buffered io for
|
|
* the rest of the read. Buffered reads will not work for
|
|
* DAX files, so don't bother trying.
|
|
*/
|
|
if (retval < 0 || !count || iocb->ki_pos >= size ||
|
|
IS_DAX(inode))
|
|
return retval;
|
|
}
|
|
|
|
return filemap_read(iocb, iter, retval);
|
|
}
|
|
EXPORT_SYMBOL(generic_file_read_iter);
|
|
|
|
static inline loff_t page_seek_hole_data(struct xa_state *xas,
|
|
struct address_space *mapping, struct page *page,
|
|
loff_t start, loff_t end, bool seek_data)
|
|
{
|
|
const struct address_space_operations *ops = mapping->a_ops;
|
|
size_t offset, bsz = i_blocksize(mapping->host);
|
|
|
|
if (xa_is_value(page) || PageUptodate(page))
|
|
return seek_data ? start : end;
|
|
if (!ops->is_partially_uptodate)
|
|
return seek_data ? end : start;
|
|
|
|
xas_pause(xas);
|
|
rcu_read_unlock();
|
|
lock_page(page);
|
|
if (unlikely(page->mapping != mapping))
|
|
goto unlock;
|
|
|
|
offset = offset_in_thp(page, start) & ~(bsz - 1);
|
|
|
|
do {
|
|
if (ops->is_partially_uptodate(page, offset, bsz) == seek_data)
|
|
break;
|
|
start = (start + bsz) & ~(bsz - 1);
|
|
offset += bsz;
|
|
} while (offset < thp_size(page));
|
|
unlock:
|
|
unlock_page(page);
|
|
rcu_read_lock();
|
|
return start;
|
|
}
|
|
|
|
static inline
|
|
unsigned int seek_page_size(struct xa_state *xas, struct page *page)
|
|
{
|
|
if (xa_is_value(page))
|
|
return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
|
|
return thp_size(page);
|
|
}
|
|
|
|
/**
|
|
* mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
|
|
* @mapping: Address space to search.
|
|
* @start: First byte to consider.
|
|
* @end: Limit of search (exclusive).
|
|
* @whence: Either SEEK_HOLE or SEEK_DATA.
|
|
*
|
|
* If the page cache knows which blocks contain holes and which blocks
|
|
* contain data, your filesystem can use this function to implement
|
|
* SEEK_HOLE and SEEK_DATA. This is useful for filesystems which are
|
|
* entirely memory-based such as tmpfs, and filesystems which support
|
|
* unwritten extents.
|
|
*
|
|
* Return: The requested offset on success, or -ENXIO if @whence specifies
|
|
* SEEK_DATA and there is no data after @start. There is an implicit hole
|
|
* after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
|
|
* and @end contain data.
|
|
*/
|
|
loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
|
|
loff_t end, int whence)
|
|
{
|
|
XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
|
|
pgoff_t max = (end - 1) >> PAGE_SHIFT;
|
|
bool seek_data = (whence == SEEK_DATA);
|
|
struct page *page;
|
|
|
|
if (end <= start)
|
|
return -ENXIO;
|
|
|
|
rcu_read_lock();
|
|
while ((page = find_get_entry(&xas, max, XA_PRESENT))) {
|
|
loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
|
|
unsigned int seek_size;
|
|
|
|
if (start < pos) {
|
|
if (!seek_data)
|
|
goto unlock;
|
|
start = pos;
|
|
}
|
|
|
|
seek_size = seek_page_size(&xas, page);
|
|
pos = round_up(pos + 1, seek_size);
|
|
start = page_seek_hole_data(&xas, mapping, page, start, pos,
|
|
seek_data);
|
|
if (start < pos)
|
|
goto unlock;
|
|
if (start >= end)
|
|
break;
|
|
if (seek_size > PAGE_SIZE)
|
|
xas_set(&xas, pos >> PAGE_SHIFT);
|
|
if (!xa_is_value(page))
|
|
put_page(page);
|
|
}
|
|
if (seek_data)
|
|
start = -ENXIO;
|
|
unlock:
|
|
rcu_read_unlock();
|
|
if (page && !xa_is_value(page))
|
|
put_page(page);
|
|
if (start > end)
|
|
return end;
|
|
return start;
|
|
}
|
|
|
|
#ifdef CONFIG_MMU
|
|
#define MMAP_LOTSAMISS (100)
|
|
/*
|
|
* lock_page_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
|
|
* @vmf - the vm_fault for this fault.
|
|
* @page - the page to lock.
|
|
* @fpin - the pointer to the file we may pin (or is already pinned).
|
|
*
|
|
* This works similar to lock_page_or_retry in that it can drop the mmap_lock.
|
|
* It differs in that it actually returns the page locked if it returns 1 and 0
|
|
* if it couldn't lock the page. If we did have to drop the mmap_lock then fpin
|
|
* will point to the pinned file and needs to be fput()'ed at a later point.
|
|
*/
|
|
static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
|
|
struct file **fpin)
|
|
{
|
|
if (trylock_page(page))
|
|
return 1;
|
|
|
|
/*
|
|
* NOTE! This will make us return with VM_FAULT_RETRY, but with
|
|
* the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
|
|
* is supposed to work. We have way too many special cases..
|
|
*/
|
|
if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
|
|
return 0;
|
|
|
|
*fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
|
|
if (vmf->flags & FAULT_FLAG_KILLABLE) {
|
|
if (__lock_page_killable(page)) {
|
|
/*
|
|
* We didn't have the right flags to drop the mmap_lock,
|
|
* but all fault_handlers only check for fatal signals
|
|
* if we return VM_FAULT_RETRY, so we need to drop the
|
|
* mmap_lock here and return 0 if we don't have a fpin.
|
|
*/
|
|
if (*fpin == NULL)
|
|
mmap_read_unlock(vmf->vma->vm_mm);
|
|
return 0;
|
|
}
|
|
} else
|
|
__lock_page(page);
|
|
return 1;
|
|
}
|
|
|
|
|
|
/*
|
|
* Synchronous readahead happens when we don't even find a page in the page
|
|
* cache at all. We don't want to perform IO under the mmap sem, so if we have
|
|
* to drop the mmap sem we return the file that was pinned in order for us to do
|
|
* that. If we didn't pin a file then we return NULL. The file that is
|
|
* returned needs to be fput()'ed when we're done with it.
|
|
*/
|
|
static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
|
|
{
|
|
struct file *file = vmf->vma->vm_file;
|
|
struct file_ra_state *ra = &file->f_ra;
|
|
struct address_space *mapping = file->f_mapping;
|
|
DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
|
|
struct file *fpin = NULL;
|
|
unsigned int mmap_miss;
|
|
|
|
/* If we don't want any read-ahead, don't bother */
|
|
if (vmf->vma->vm_flags & VM_RAND_READ)
|
|
return fpin;
|
|
if (!ra->ra_pages)
|
|
return fpin;
|
|
|
|
if (vmf->vma->vm_flags & VM_SEQ_READ) {
|
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
|
|
page_cache_sync_ra(&ractl, ra->ra_pages);
|
|
return fpin;
|
|
}
|
|
|
|
/* Avoid banging the cache line if not needed */
|
|
mmap_miss = READ_ONCE(ra->mmap_miss);
|
|
if (mmap_miss < MMAP_LOTSAMISS * 10)
|
|
WRITE_ONCE(ra->mmap_miss, ++mmap_miss);
|
|
|
|
/*
|
|
* Do we miss much more than hit in this file? If so,
|
|
* stop bothering with read-ahead. It will only hurt.
|
|
*/
|
|
if (mmap_miss > MMAP_LOTSAMISS)
|
|
return fpin;
|
|
|
|
/*
|
|
* mmap read-around
|
|
*/
|
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
|
|
ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
|
|
ra->size = ra->ra_pages;
|
|
ra->async_size = ra->ra_pages / 4;
|
|
ractl._index = ra->start;
|
|
do_page_cache_ra(&ractl, ra->size, ra->async_size);
|
|
return fpin;
|
|
}
|
|
|
|
/*
|
|
* Asynchronous readahead happens when we find the page and PG_readahead,
|
|
* so we want to possibly extend the readahead further. We return the file that
|
|
* was pinned if we have to drop the mmap_lock in order to do IO.
|
|
*/
|
|
static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
|
|
struct page *page)
|
|
{
|
|
struct file *file = vmf->vma->vm_file;
|
|
struct file_ra_state *ra = &file->f_ra;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct file *fpin = NULL;
|
|
unsigned int mmap_miss;
|
|
pgoff_t offset = vmf->pgoff;
|
|
|
|
/* If we don't want any read-ahead, don't bother */
|
|
if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
|
|
return fpin;
|
|
mmap_miss = READ_ONCE(ra->mmap_miss);
|
|
if (mmap_miss)
|
|
WRITE_ONCE(ra->mmap_miss, --mmap_miss);
|
|
if (PageReadahead(page)) {
|
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
|
|
page_cache_async_readahead(mapping, ra, file,
|
|
page, offset, ra->ra_pages);
|
|
}
|
|
return fpin;
|
|
}
|
|
|
|
/**
|
|
* filemap_fault - read in file data for page fault handling
|
|
* @vmf: struct vm_fault containing details of the fault
|
|
*
|
|
* filemap_fault() is invoked via the vma operations vector for a
|
|
* mapped memory region to read in file data during a page fault.
|
|
*
|
|
* The goto's are kind of ugly, but this streamlines the normal case of having
|
|
* it in the page cache, and handles the special cases reasonably without
|
|
* having a lot of duplicated code.
|
|
*
|
|
* vma->vm_mm->mmap_lock must be held on entry.
|
|
*
|
|
* If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
|
|
* may be dropped before doing I/O or by lock_page_maybe_drop_mmap().
|
|
*
|
|
* If our return value does not have VM_FAULT_RETRY set, the mmap_lock
|
|
* has not been released.
|
|
*
|
|
* We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
|
|
*
|
|
* Return: bitwise-OR of %VM_FAULT_ codes.
|
|
*/
|
|
vm_fault_t filemap_fault(struct vm_fault *vmf)
|
|
{
|
|
int error;
|
|
struct file *file = vmf->vma->vm_file;
|
|
struct file *fpin = NULL;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
pgoff_t offset = vmf->pgoff;
|
|
pgoff_t max_off;
|
|
struct page *page;
|
|
vm_fault_t ret = 0;
|
|
|
|
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
|
|
if (unlikely(offset >= max_off))
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
/*
|
|
* Do we have something in the page cache already?
|
|
*/
|
|
page = find_get_page(mapping, offset);
|
|
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
|
|
/*
|
|
* We found the page, so try async readahead before
|
|
* waiting for the lock.
|
|
*/
|
|
fpin = do_async_mmap_readahead(vmf, page);
|
|
} else if (!page) {
|
|
/* No page in the page cache at all */
|
|
count_vm_event(PGMAJFAULT);
|
|
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
|
|
ret = VM_FAULT_MAJOR;
|
|
fpin = do_sync_mmap_readahead(vmf);
|
|
retry_find:
|
|
page = pagecache_get_page(mapping, offset,
|
|
FGP_CREAT|FGP_FOR_MMAP,
|
|
vmf->gfp_mask);
|
|
if (!page) {
|
|
if (fpin)
|
|
goto out_retry;
|
|
return VM_FAULT_OOM;
|
|
}
|
|
}
|
|
|
|
if (!lock_page_maybe_drop_mmap(vmf, page, &fpin))
|
|
goto out_retry;
|
|
|
|
/* Did it get truncated? */
|
|
if (unlikely(compound_head(page)->mapping != mapping)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto retry_find;
|
|
}
|
|
VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
|
|
|
|
/*
|
|
* We have a locked page in the page cache, now we need to check
|
|
* that it's up-to-date. If not, it is going to be due to an error.
|
|
*/
|
|
if (unlikely(!PageUptodate(page)))
|
|
goto page_not_uptodate;
|
|
|
|
/*
|
|
* We've made it this far and we had to drop our mmap_lock, now is the
|
|
* time to return to the upper layer and have it re-find the vma and
|
|
* redo the fault.
|
|
*/
|
|
if (fpin) {
|
|
unlock_page(page);
|
|
goto out_retry;
|
|
}
|
|
|
|
/*
|
|
* Found the page and have a reference on it.
|
|
* We must recheck i_size under page lock.
|
|
*/
|
|
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
|
|
if (unlikely(offset >= max_off)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return VM_FAULT_SIGBUS;
|
|
}
|
|
|
|
vmf->page = page;
|
|
return ret | VM_FAULT_LOCKED;
|
|
|
|
page_not_uptodate:
|
|
/*
|
|
* Umm, take care of errors if the page isn't up-to-date.
|
|
* Try to re-read it _once_. We do this synchronously,
|
|
* because there really aren't any performance issues here
|
|
* and we need to check for errors.
|
|
*/
|
|
fpin = maybe_unlock_mmap_for_io(vmf, fpin);
|
|
error = filemap_read_page(file, mapping, page);
|
|
if (fpin)
|
|
goto out_retry;
|
|
put_page(page);
|
|
|
|
if (!error || error == AOP_TRUNCATED_PAGE)
|
|
goto retry_find;
|
|
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
out_retry:
|
|
/*
|
|
* We dropped the mmap_lock, we need to return to the fault handler to
|
|
* re-find the vma and come back and find our hopefully still populated
|
|
* page.
|
|
*/
|
|
if (page)
|
|
put_page(page);
|
|
if (fpin)
|
|
fput(fpin);
|
|
return ret | VM_FAULT_RETRY;
|
|
}
|
|
EXPORT_SYMBOL(filemap_fault);
|
|
|
|
static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page)
|
|
{
|
|
struct mm_struct *mm = vmf->vma->vm_mm;
|
|
|
|
/* Huge page is mapped? No need to proceed. */
|
|
if (pmd_trans_huge(*vmf->pmd)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return true;
|
|
}
|
|
|
|
if (pmd_none(*vmf->pmd) && PageTransHuge(page)) {
|
|
vm_fault_t ret = do_set_pmd(vmf, page);
|
|
if (!ret) {
|
|
/* The page is mapped successfully, reference consumed. */
|
|
unlock_page(page);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
if (pmd_none(*vmf->pmd)) {
|
|
vmf->ptl = pmd_lock(mm, vmf->pmd);
|
|
if (likely(pmd_none(*vmf->pmd))) {
|
|
mm_inc_nr_ptes(mm);
|
|
pmd_populate(mm, vmf->pmd, vmf->prealloc_pte);
|
|
vmf->prealloc_pte = NULL;
|
|
}
|
|
spin_unlock(vmf->ptl);
|
|
}
|
|
|
|
/* See comment in handle_pte_fault() */
|
|
if (pmd_devmap_trans_unstable(vmf->pmd)) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
static struct page *next_uptodate_page(struct page *page,
|
|
struct address_space *mapping,
|
|
struct xa_state *xas, pgoff_t end_pgoff)
|
|
{
|
|
unsigned long max_idx;
|
|
|
|
do {
|
|
if (!page)
|
|
return NULL;
|
|
if (xas_retry(xas, page))
|
|
continue;
|
|
if (xa_is_value(page))
|
|
continue;
|
|
if (PageLocked(page))
|
|
continue;
|
|
if (!page_cache_get_speculative(page))
|
|
continue;
|
|
/* Has the page moved or been split? */
|
|
if (unlikely(page != xas_reload(xas)))
|
|
goto skip;
|
|
if (!PageUptodate(page) || PageReadahead(page))
|
|
goto skip;
|
|
if (PageHWPoison(page))
|
|
goto skip;
|
|
if (!trylock_page(page))
|
|
goto skip;
|
|
if (page->mapping != mapping)
|
|
goto unlock;
|
|
if (!PageUptodate(page))
|
|
goto unlock;
|
|
max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
|
|
if (xas->xa_index >= max_idx)
|
|
goto unlock;
|
|
return page;
|
|
unlock:
|
|
unlock_page(page);
|
|
skip:
|
|
put_page(page);
|
|
} while ((page = xas_next_entry(xas, end_pgoff)) != NULL);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static inline struct page *first_map_page(struct address_space *mapping,
|
|
struct xa_state *xas,
|
|
pgoff_t end_pgoff)
|
|
{
|
|
return next_uptodate_page(xas_find(xas, end_pgoff),
|
|
mapping, xas, end_pgoff);
|
|
}
|
|
|
|
static inline struct page *next_map_page(struct address_space *mapping,
|
|
struct xa_state *xas,
|
|
pgoff_t end_pgoff)
|
|
{
|
|
return next_uptodate_page(xas_next_entry(xas, end_pgoff),
|
|
mapping, xas, end_pgoff);
|
|
}
|
|
|
|
vm_fault_t filemap_map_pages(struct vm_fault *vmf,
|
|
pgoff_t start_pgoff, pgoff_t end_pgoff)
|
|
{
|
|
struct vm_area_struct *vma = vmf->vma;
|
|
struct file *file = vma->vm_file;
|
|
struct address_space *mapping = file->f_mapping;
|
|
pgoff_t last_pgoff = start_pgoff;
|
|
unsigned long addr;
|
|
XA_STATE(xas, &mapping->i_pages, start_pgoff);
|
|
struct page *head, *page;
|
|
unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
|
|
vm_fault_t ret = 0;
|
|
|
|
rcu_read_lock();
|
|
head = first_map_page(mapping, &xas, end_pgoff);
|
|
if (!head)
|
|
goto out;
|
|
|
|
if (filemap_map_pmd(vmf, head)) {
|
|
ret = VM_FAULT_NOPAGE;
|
|
goto out;
|
|
}
|
|
|
|
addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
|
|
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
|
|
do {
|
|
page = find_subpage(head, xas.xa_index);
|
|
if (PageHWPoison(page))
|
|
goto unlock;
|
|
|
|
if (mmap_miss > 0)
|
|
mmap_miss--;
|
|
|
|
addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
|
|
vmf->pte += xas.xa_index - last_pgoff;
|
|
last_pgoff = xas.xa_index;
|
|
|
|
if (!pte_none(*vmf->pte))
|
|
goto unlock;
|
|
|
|
/* We're about to handle the fault */
|
|
if (vmf->address == addr)
|
|
ret = VM_FAULT_NOPAGE;
|
|
|
|
do_set_pte(vmf, page, addr);
|
|
/* no need to invalidate: a not-present page won't be cached */
|
|
update_mmu_cache(vma, addr, vmf->pte);
|
|
unlock_page(head);
|
|
continue;
|
|
unlock:
|
|
unlock_page(head);
|
|
put_page(head);
|
|
} while ((head = next_map_page(mapping, &xas, end_pgoff)) != NULL);
|
|
pte_unmap_unlock(vmf->pte, vmf->ptl);
|
|
out:
|
|
rcu_read_unlock();
|
|
WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(filemap_map_pages);
|
|
|
|
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
|
|
{
|
|
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
|
|
struct page *page = vmf->page;
|
|
vm_fault_t ret = VM_FAULT_LOCKED;
|
|
|
|
sb_start_pagefault(mapping->host->i_sb);
|
|
file_update_time(vmf->vma->vm_file);
|
|
lock_page(page);
|
|
if (page->mapping != mapping) {
|
|
unlock_page(page);
|
|
ret = VM_FAULT_NOPAGE;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We mark the page dirty already here so that when freeze is in
|
|
* progress, we are guaranteed that writeback during freezing will
|
|
* see the dirty page and writeprotect it again.
|
|
*/
|
|
set_page_dirty(page);
|
|
wait_for_stable_page(page);
|
|
out:
|
|
sb_end_pagefault(mapping->host->i_sb);
|
|
return ret;
|
|
}
|
|
|
|
const struct vm_operations_struct generic_file_vm_ops = {
|
|
.fault = filemap_fault,
|
|
.map_pages = filemap_map_pages,
|
|
.page_mkwrite = filemap_page_mkwrite,
|
|
};
|
|
|
|
/* This is used for a general mmap of a disk file */
|
|
|
|
int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
|
|
if (!mapping->a_ops->readpage)
|
|
return -ENOEXEC;
|
|
file_accessed(file);
|
|
vma->vm_ops = &generic_file_vm_ops;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This is for filesystems which do not implement ->writepage.
|
|
*/
|
|
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
|
|
return -EINVAL;
|
|
return generic_file_mmap(file, vma);
|
|
}
|
|
#else
|
|
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
|
|
{
|
|
return VM_FAULT_SIGBUS;
|
|
}
|
|
int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
#endif /* CONFIG_MMU */
|
|
|
|
EXPORT_SYMBOL(filemap_page_mkwrite);
|
|
EXPORT_SYMBOL(generic_file_mmap);
|
|
EXPORT_SYMBOL(generic_file_readonly_mmap);
|
|
|
|
static struct page *wait_on_page_read(struct page *page)
|
|
{
|
|
if (!IS_ERR(page)) {
|
|
wait_on_page_locked(page);
|
|
if (!PageUptodate(page)) {
|
|
put_page(page);
|
|
page = ERR_PTR(-EIO);
|
|
}
|
|
}
|
|
return page;
|
|
}
|
|
|
|
static struct page *do_read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data,
|
|
gfp_t gfp)
|
|
{
|
|
struct page *page;
|
|
int err;
|
|
repeat:
|
|
page = find_get_page(mapping, index);
|
|
if (!page) {
|
|
page = __page_cache_alloc(gfp);
|
|
if (!page)
|
|
return ERR_PTR(-ENOMEM);
|
|
err = add_to_page_cache_lru(page, mapping, index, gfp);
|
|
if (unlikely(err)) {
|
|
put_page(page);
|
|
if (err == -EEXIST)
|
|
goto repeat;
|
|
/* Presumably ENOMEM for xarray node */
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
filler:
|
|
if (filler)
|
|
err = filler(data, page);
|
|
else
|
|
err = mapping->a_ops->readpage(data, page);
|
|
|
|
if (err < 0) {
|
|
put_page(page);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
page = wait_on_page_read(page);
|
|
if (IS_ERR(page))
|
|
return page;
|
|
goto out;
|
|
}
|
|
if (PageUptodate(page))
|
|
goto out;
|
|
|
|
/*
|
|
* Page is not up to date and may be locked due to one of the following
|
|
* case a: Page is being filled and the page lock is held
|
|
* case b: Read/write error clearing the page uptodate status
|
|
* case c: Truncation in progress (page locked)
|
|
* case d: Reclaim in progress
|
|
*
|
|
* Case a, the page will be up to date when the page is unlocked.
|
|
* There is no need to serialise on the page lock here as the page
|
|
* is pinned so the lock gives no additional protection. Even if the
|
|
* page is truncated, the data is still valid if PageUptodate as
|
|
* it's a race vs truncate race.
|
|
* Case b, the page will not be up to date
|
|
* Case c, the page may be truncated but in itself, the data may still
|
|
* be valid after IO completes as it's a read vs truncate race. The
|
|
* operation must restart if the page is not uptodate on unlock but
|
|
* otherwise serialising on page lock to stabilise the mapping gives
|
|
* no additional guarantees to the caller as the page lock is
|
|
* released before return.
|
|
* Case d, similar to truncation. If reclaim holds the page lock, it
|
|
* will be a race with remove_mapping that determines if the mapping
|
|
* is valid on unlock but otherwise the data is valid and there is
|
|
* no need to serialise with page lock.
|
|
*
|
|
* As the page lock gives no additional guarantee, we optimistically
|
|
* wait on the page to be unlocked and check if it's up to date and
|
|
* use the page if it is. Otherwise, the page lock is required to
|
|
* distinguish between the different cases. The motivation is that we
|
|
* avoid spurious serialisations and wakeups when multiple processes
|
|
* wait on the same page for IO to complete.
|
|
*/
|
|
wait_on_page_locked(page);
|
|
if (PageUptodate(page))
|
|
goto out;
|
|
|
|
/* Distinguish between all the cases under the safety of the lock */
|
|
lock_page(page);
|
|
|
|
/* Case c or d, restart the operation */
|
|
if (!page->mapping) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto repeat;
|
|
}
|
|
|
|
/* Someone else locked and filled the page in a very small window */
|
|
if (PageUptodate(page)) {
|
|
unlock_page(page);
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* A previous I/O error may have been due to temporary
|
|
* failures.
|
|
* Clear page error before actual read, PG_error will be
|
|
* set again if read page fails.
|
|
*/
|
|
ClearPageError(page);
|
|
goto filler;
|
|
|
|
out:
|
|
mark_page_accessed(page);
|
|
return page;
|
|
}
|
|
|
|
/**
|
|
* read_cache_page - read into page cache, fill it if needed
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @filler: function to perform the read
|
|
* @data: first arg to filler(data, page) function, often left as NULL
|
|
*
|
|
* Read into the page cache. If a page already exists, and PageUptodate() is
|
|
* not set, try to fill the page and wait for it to become unlocked.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*
|
|
* Return: up to date page on success, ERR_PTR() on failure.
|
|
*/
|
|
struct page *read_cache_page(struct address_space *mapping,
|
|
pgoff_t index,
|
|
int (*filler)(void *, struct page *),
|
|
void *data)
|
|
{
|
|
return do_read_cache_page(mapping, index, filler, data,
|
|
mapping_gfp_mask(mapping));
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page);
|
|
|
|
/**
|
|
* read_cache_page_gfp - read into page cache, using specified page allocation flags.
|
|
* @mapping: the page's address_space
|
|
* @index: the page index
|
|
* @gfp: the page allocator flags to use if allocating
|
|
*
|
|
* This is the same as "read_mapping_page(mapping, index, NULL)", but with
|
|
* any new page allocations done using the specified allocation flags.
|
|
*
|
|
* If the page does not get brought uptodate, return -EIO.
|
|
*
|
|
* Return: up to date page on success, ERR_PTR() on failure.
|
|
*/
|
|
struct page *read_cache_page_gfp(struct address_space *mapping,
|
|
pgoff_t index,
|
|
gfp_t gfp)
|
|
{
|
|
return do_read_cache_page(mapping, index, NULL, NULL, gfp);
|
|
}
|
|
EXPORT_SYMBOL(read_cache_page_gfp);
|
|
|
|
int pagecache_write_begin(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
struct page **pagep, void **fsdata)
|
|
{
|
|
const struct address_space_operations *aops = mapping->a_ops;
|
|
|
|
return aops->write_begin(file, mapping, pos, len, flags,
|
|
pagep, fsdata);
|
|
}
|
|
EXPORT_SYMBOL(pagecache_write_begin);
|
|
|
|
int pagecache_write_end(struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata)
|
|
{
|
|
const struct address_space_operations *aops = mapping->a_ops;
|
|
|
|
return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
|
|
}
|
|
EXPORT_SYMBOL(pagecache_write_end);
|
|
|
|
/*
|
|
* Warn about a page cache invalidation failure during a direct I/O write.
|
|
*/
|
|
void dio_warn_stale_pagecache(struct file *filp)
|
|
{
|
|
static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
|
|
char pathname[128];
|
|
char *path;
|
|
|
|
errseq_set(&filp->f_mapping->wb_err, -EIO);
|
|
if (__ratelimit(&_rs)) {
|
|
path = file_path(filp, pathname, sizeof(pathname));
|
|
if (IS_ERR(path))
|
|
path = "(unknown)";
|
|
pr_crit("Page cache invalidation failure on direct I/O. Possible data corruption due to collision with buffered I/O!\n");
|
|
pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
|
|
current->comm);
|
|
}
|
|
}
|
|
|
|
ssize_t
|
|
generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
loff_t pos = iocb->ki_pos;
|
|
ssize_t written;
|
|
size_t write_len;
|
|
pgoff_t end;
|
|
|
|
write_len = iov_iter_count(from);
|
|
end = (pos + write_len - 1) >> PAGE_SHIFT;
|
|
|
|
if (iocb->ki_flags & IOCB_NOWAIT) {
|
|
/* If there are pages to writeback, return */
|
|
if (filemap_range_has_page(file->f_mapping, pos,
|
|
pos + write_len - 1))
|
|
return -EAGAIN;
|
|
} else {
|
|
written = filemap_write_and_wait_range(mapping, pos,
|
|
pos + write_len - 1);
|
|
if (written)
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* After a write we want buffered reads to be sure to go to disk to get
|
|
* the new data. We invalidate clean cached page from the region we're
|
|
* about to write. We do this *before* the write so that we can return
|
|
* without clobbering -EIOCBQUEUED from ->direct_IO().
|
|
*/
|
|
written = invalidate_inode_pages2_range(mapping,
|
|
pos >> PAGE_SHIFT, end);
|
|
/*
|
|
* If a page can not be invalidated, return 0 to fall back
|
|
* to buffered write.
|
|
*/
|
|
if (written) {
|
|
if (written == -EBUSY)
|
|
return 0;
|
|
goto out;
|
|
}
|
|
|
|
written = mapping->a_ops->direct_IO(iocb, from);
|
|
|
|
/*
|
|
* Finally, try again to invalidate clean pages which might have been
|
|
* cached by non-direct readahead, or faulted in by get_user_pages()
|
|
* if the source of the write was an mmap'ed region of the file
|
|
* we're writing. Either one is a pretty crazy thing to do,
|
|
* so we don't support it 100%. If this invalidation
|
|
* fails, tough, the write still worked...
|
|
*
|
|
* Most of the time we do not need this since dio_complete() will do
|
|
* the invalidation for us. However there are some file systems that
|
|
* do not end up with dio_complete() being called, so let's not break
|
|
* them by removing it completely.
|
|
*
|
|
* Noticeable example is a blkdev_direct_IO().
|
|
*
|
|
* Skip invalidation for async writes or if mapping has no pages.
|
|
*/
|
|
if (written > 0 && mapping->nrpages &&
|
|
invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
|
|
dio_warn_stale_pagecache(file);
|
|
|
|
if (written > 0) {
|
|
pos += written;
|
|
write_len -= written;
|
|
if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
|
|
i_size_write(inode, pos);
|
|
mark_inode_dirty(inode);
|
|
}
|
|
iocb->ki_pos = pos;
|
|
}
|
|
if (written != -EIOCBQUEUED)
|
|
iov_iter_revert(from, write_len - iov_iter_count(from));
|
|
out:
|
|
return written;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_direct_write);
|
|
|
|
/*
|
|
* Find or create a page at the given pagecache position. Return the locked
|
|
* page. This function is specifically for buffered writes.
|
|
*/
|
|
struct page *grab_cache_page_write_begin(struct address_space *mapping,
|
|
pgoff_t index, unsigned flags)
|
|
{
|
|
struct page *page;
|
|
int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
|
|
|
|
if (flags & AOP_FLAG_NOFS)
|
|
fgp_flags |= FGP_NOFS;
|
|
|
|
page = pagecache_get_page(mapping, index, fgp_flags,
|
|
mapping_gfp_mask(mapping));
|
|
if (page)
|
|
wait_for_stable_page(page);
|
|
|
|
return page;
|
|
}
|
|
EXPORT_SYMBOL(grab_cache_page_write_begin);
|
|
|
|
ssize_t generic_perform_write(struct file *file,
|
|
struct iov_iter *i, loff_t pos)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
const struct address_space_operations *a_ops = mapping->a_ops;
|
|
long status = 0;
|
|
ssize_t written = 0;
|
|
unsigned int flags = 0;
|
|
|
|
do {
|
|
struct page *page;
|
|
unsigned long offset; /* Offset into pagecache page */
|
|
unsigned long bytes; /* Bytes to write to page */
|
|
size_t copied; /* Bytes copied from user */
|
|
void *fsdata;
|
|
|
|
offset = (pos & (PAGE_SIZE - 1));
|
|
bytes = min_t(unsigned long, PAGE_SIZE - offset,
|
|
iov_iter_count(i));
|
|
|
|
again:
|
|
/*
|
|
* Bring in the user page that we will copy from _first_.
|
|
* Otherwise there's a nasty deadlock on copying from the
|
|
* same page as we're writing to, without it being marked
|
|
* up-to-date.
|
|
*/
|
|
if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
|
|
status = -EFAULT;
|
|
break;
|
|
}
|
|
|
|
if (fatal_signal_pending(current)) {
|
|
status = -EINTR;
|
|
break;
|
|
}
|
|
|
|
status = a_ops->write_begin(file, mapping, pos, bytes, flags,
|
|
&page, &fsdata);
|
|
if (unlikely(status < 0))
|
|
break;
|
|
|
|
if (mapping_writably_mapped(mapping))
|
|
flush_dcache_page(page);
|
|
|
|
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
|
|
flush_dcache_page(page);
|
|
|
|
status = a_ops->write_end(file, mapping, pos, bytes, copied,
|
|
page, fsdata);
|
|
if (unlikely(status != copied)) {
|
|
iov_iter_revert(i, copied - max(status, 0L));
|
|
if (unlikely(status < 0))
|
|
break;
|
|
}
|
|
cond_resched();
|
|
|
|
if (unlikely(status == 0)) {
|
|
/*
|
|
* A short copy made ->write_end() reject the
|
|
* thing entirely. Might be memory poisoning
|
|
* halfway through, might be a race with munmap,
|
|
* might be severe memory pressure.
|
|
*/
|
|
if (copied)
|
|
bytes = copied;
|
|
goto again;
|
|
}
|
|
pos += status;
|
|
written += status;
|
|
|
|
balance_dirty_pages_ratelimited(mapping);
|
|
} while (iov_iter_count(i));
|
|
|
|
return written ? written : status;
|
|
}
|
|
EXPORT_SYMBOL(generic_perform_write);
|
|
|
|
/**
|
|
* __generic_file_write_iter - write data to a file
|
|
* @iocb: IO state structure (file, offset, etc.)
|
|
* @from: iov_iter with data to write
|
|
*
|
|
* This function does all the work needed for actually writing data to a
|
|
* file. It does all basic checks, removes SUID from the file, updates
|
|
* modification times and calls proper subroutines depending on whether we
|
|
* do direct IO or a standard buffered write.
|
|
*
|
|
* It expects i_mutex to be grabbed unless we work on a block device or similar
|
|
* object which does not need locking at all.
|
|
*
|
|
* This function does *not* take care of syncing data in case of O_SYNC write.
|
|
* A caller has to handle it. This is mainly due to the fact that we want to
|
|
* avoid syncing under i_mutex.
|
|
*
|
|
* Return:
|
|
* * number of bytes written, even for truncated writes
|
|
* * negative error code if no data has been written at all
|
|
*/
|
|
ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct address_space *mapping = file->f_mapping;
|
|
struct inode *inode = mapping->host;
|
|
ssize_t written = 0;
|
|
ssize_t err;
|
|
ssize_t status;
|
|
|
|
/* We can write back this queue in page reclaim */
|
|
current->backing_dev_info = inode_to_bdi(inode);
|
|
err = file_remove_privs(file);
|
|
if (err)
|
|
goto out;
|
|
|
|
err = file_update_time(file);
|
|
if (err)
|
|
goto out;
|
|
|
|
if (iocb->ki_flags & IOCB_DIRECT) {
|
|
loff_t pos, endbyte;
|
|
|
|
written = generic_file_direct_write(iocb, from);
|
|
/*
|
|
* If the write stopped short of completing, fall back to
|
|
* buffered writes. Some filesystems do this for writes to
|
|
* holes, for example. For DAX files, a buffered write will
|
|
* not succeed (even if it did, DAX does not handle dirty
|
|
* page-cache pages correctly).
|
|
*/
|
|
if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
|
|
goto out;
|
|
|
|
status = generic_perform_write(file, from, pos = iocb->ki_pos);
|
|
/*
|
|
* If generic_perform_write() returned a synchronous error
|
|
* then we want to return the number of bytes which were
|
|
* direct-written, or the error code if that was zero. Note
|
|
* that this differs from normal direct-io semantics, which
|
|
* will return -EFOO even if some bytes were written.
|
|
*/
|
|
if (unlikely(status < 0)) {
|
|
err = status;
|
|
goto out;
|
|
}
|
|
/*
|
|
* We need to ensure that the page cache pages are written to
|
|
* disk and invalidated to preserve the expected O_DIRECT
|
|
* semantics.
|
|
*/
|
|
endbyte = pos + status - 1;
|
|
err = filemap_write_and_wait_range(mapping, pos, endbyte);
|
|
if (err == 0) {
|
|
iocb->ki_pos = endbyte + 1;
|
|
written += status;
|
|
invalidate_mapping_pages(mapping,
|
|
pos >> PAGE_SHIFT,
|
|
endbyte >> PAGE_SHIFT);
|
|
} else {
|
|
/*
|
|
* We don't know how much we wrote, so just return
|
|
* the number of bytes which were direct-written
|
|
*/
|
|
}
|
|
} else {
|
|
written = generic_perform_write(file, from, iocb->ki_pos);
|
|
if (likely(written > 0))
|
|
iocb->ki_pos += written;
|
|
}
|
|
out:
|
|
current->backing_dev_info = NULL;
|
|
return written ? written : err;
|
|
}
|
|
EXPORT_SYMBOL(__generic_file_write_iter);
|
|
|
|
/**
|
|
* generic_file_write_iter - write data to a file
|
|
* @iocb: IO state structure
|
|
* @from: iov_iter with data to write
|
|
*
|
|
* This is a wrapper around __generic_file_write_iter() to be used by most
|
|
* filesystems. It takes care of syncing the file in case of O_SYNC file
|
|
* and acquires i_mutex as needed.
|
|
* Return:
|
|
* * negative error code if no data has been written at all of
|
|
* vfs_fsync_range() failed for a synchronous write
|
|
* * number of bytes written, even for truncated writes
|
|
*/
|
|
ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
|
|
{
|
|
struct file *file = iocb->ki_filp;
|
|
struct inode *inode = file->f_mapping->host;
|
|
ssize_t ret;
|
|
|
|
inode_lock(inode);
|
|
ret = generic_write_checks(iocb, from);
|
|
if (ret > 0)
|
|
ret = __generic_file_write_iter(iocb, from);
|
|
inode_unlock(inode);
|
|
|
|
if (ret > 0)
|
|
ret = generic_write_sync(iocb, ret);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(generic_file_write_iter);
|
|
|
|
/**
|
|
* try_to_release_page() - release old fs-specific metadata on a page
|
|
*
|
|
* @page: the page which the kernel is trying to free
|
|
* @gfp_mask: memory allocation flags (and I/O mode)
|
|
*
|
|
* The address_space is to try to release any data against the page
|
|
* (presumably at page->private).
|
|
*
|
|
* This may also be called if PG_fscache is set on a page, indicating that the
|
|
* page is known to the local caching routines.
|
|
*
|
|
* The @gfp_mask argument specifies whether I/O may be performed to release
|
|
* this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
|
|
*
|
|
* Return: %1 if the release was successful, otherwise return zero.
|
|
*/
|
|
int try_to_release_page(struct page *page, gfp_t gfp_mask)
|
|
{
|
|
struct address_space * const mapping = page->mapping;
|
|
|
|
BUG_ON(!PageLocked(page));
|
|
if (PageWriteback(page))
|
|
return 0;
|
|
|
|
if (mapping && mapping->a_ops->releasepage)
|
|
return mapping->a_ops->releasepage(page, gfp_mask);
|
|
return try_to_free_buffers(page);
|
|
}
|
|
|
|
EXPORT_SYMBOL(try_to_release_page);
|