mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-05 10:04:12 +08:00
730633f0b7
Currently, serializing operations such as page fault, read, or readahead against hole punching is rather difficult. The basic race scheme is like: fallocate(FALLOC_FL_PUNCH_HOLE) read / fault / .. truncate_inode_pages_range() <create pages in page cache here> <update fs block mapping and free blocks> Now the problem is in this way read / page fault / readahead can instantiate pages in page cache with potentially stale data (if blocks get quickly reused). Avoiding this race is not simple - page locks do not work because we want to make sure there are *no* pages in given range. inode->i_rwsem does not work because page fault happens under mmap_sem which ranks below inode->i_rwsem. Also using it for reads makes the performance for mixed read-write workloads suffer. So create a new rw_semaphore in the address_space - invalidate_lock - that protects adding of pages to page cache for page faults / reads / readahead. Reviewed-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz>
718 lines
20 KiB
C
718 lines
20 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* mm/readahead.c - address_space-level file readahead.
|
|
*
|
|
* Copyright (C) 2002, Linus Torvalds
|
|
*
|
|
* 09Apr2002 Andrew Morton
|
|
* Initial version.
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/dax.h>
|
|
#include <linux/gfp.h>
|
|
#include <linux/export.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/backing-dev.h>
|
|
#include <linux/task_io_accounting_ops.h>
|
|
#include <linux/pagevec.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/syscalls.h>
|
|
#include <linux/file.h>
|
|
#include <linux/mm_inline.h>
|
|
#include <linux/blk-cgroup.h>
|
|
#include <linux/fadvise.h>
|
|
#include <linux/sched/mm.h>
|
|
|
|
#include "internal.h"
|
|
|
|
/*
|
|
* Initialise a struct file's readahead state. Assumes that the caller has
|
|
* memset *ra to zero.
|
|
*/
|
|
void
|
|
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
|
|
{
|
|
ra->ra_pages = inode_to_bdi(mapping->host)->ra_pages;
|
|
ra->prev_pos = -1;
|
|
}
|
|
EXPORT_SYMBOL_GPL(file_ra_state_init);
|
|
|
|
/*
|
|
* see if a page needs releasing upon read_cache_pages() failure
|
|
* - the caller of read_cache_pages() may have set PG_private or PG_fscache
|
|
* before calling, such as the NFS fs marking pages that are cached locally
|
|
* on disk, thus we need to give the fs a chance to clean up in the event of
|
|
* an error
|
|
*/
|
|
static void read_cache_pages_invalidate_page(struct address_space *mapping,
|
|
struct page *page)
|
|
{
|
|
if (page_has_private(page)) {
|
|
if (!trylock_page(page))
|
|
BUG();
|
|
page->mapping = mapping;
|
|
do_invalidatepage(page, 0, PAGE_SIZE);
|
|
page->mapping = NULL;
|
|
unlock_page(page);
|
|
}
|
|
put_page(page);
|
|
}
|
|
|
|
/*
|
|
* release a list of pages, invalidating them first if need be
|
|
*/
|
|
static void read_cache_pages_invalidate_pages(struct address_space *mapping,
|
|
struct list_head *pages)
|
|
{
|
|
struct page *victim;
|
|
|
|
while (!list_empty(pages)) {
|
|
victim = lru_to_page(pages);
|
|
list_del(&victim->lru);
|
|
read_cache_pages_invalidate_page(mapping, victim);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* read_cache_pages - populate an address space with some pages & start reads against them
|
|
* @mapping: the address_space
|
|
* @pages: The address of a list_head which contains the target pages. These
|
|
* pages have their ->index populated and are otherwise uninitialised.
|
|
* @filler: callback routine for filling a single page.
|
|
* @data: private data for the callback routine.
|
|
*
|
|
* Hides the details of the LRU cache etc from the filesystems.
|
|
*
|
|
* Returns: %0 on success, error return by @filler otherwise
|
|
*/
|
|
int read_cache_pages(struct address_space *mapping, struct list_head *pages,
|
|
int (*filler)(void *, struct page *), void *data)
|
|
{
|
|
struct page *page;
|
|
int ret = 0;
|
|
|
|
while (!list_empty(pages)) {
|
|
page = lru_to_page(pages);
|
|
list_del(&page->lru);
|
|
if (add_to_page_cache_lru(page, mapping, page->index,
|
|
readahead_gfp_mask(mapping))) {
|
|
read_cache_pages_invalidate_page(mapping, page);
|
|
continue;
|
|
}
|
|
put_page(page);
|
|
|
|
ret = filler(data, page);
|
|
if (unlikely(ret)) {
|
|
read_cache_pages_invalidate_pages(mapping, pages);
|
|
break;
|
|
}
|
|
task_io_account_read(PAGE_SIZE);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
EXPORT_SYMBOL(read_cache_pages);
|
|
|
|
static void read_pages(struct readahead_control *rac, struct list_head *pages,
|
|
bool skip_page)
|
|
{
|
|
const struct address_space_operations *aops = rac->mapping->a_ops;
|
|
struct page *page;
|
|
struct blk_plug plug;
|
|
|
|
if (!readahead_count(rac))
|
|
goto out;
|
|
|
|
blk_start_plug(&plug);
|
|
|
|
if (aops->readahead) {
|
|
aops->readahead(rac);
|
|
/* Clean up the remaining pages */
|
|
while ((page = readahead_page(rac))) {
|
|
unlock_page(page);
|
|
put_page(page);
|
|
}
|
|
} else if (aops->readpages) {
|
|
aops->readpages(rac->file, rac->mapping, pages,
|
|
readahead_count(rac));
|
|
/* Clean up the remaining pages */
|
|
put_pages_list(pages);
|
|
rac->_index += rac->_nr_pages;
|
|
rac->_nr_pages = 0;
|
|
} else {
|
|
while ((page = readahead_page(rac))) {
|
|
aops->readpage(rac->file, page);
|
|
put_page(page);
|
|
}
|
|
}
|
|
|
|
blk_finish_plug(&plug);
|
|
|
|
BUG_ON(!list_empty(pages));
|
|
BUG_ON(readahead_count(rac));
|
|
|
|
out:
|
|
if (skip_page)
|
|
rac->_index++;
|
|
}
|
|
|
|
/**
|
|
* page_cache_ra_unbounded - Start unchecked readahead.
|
|
* @ractl: Readahead control.
|
|
* @nr_to_read: The number of pages to read.
|
|
* @lookahead_size: Where to start the next readahead.
|
|
*
|
|
* This function is for filesystems to call when they want to start
|
|
* readahead beyond a file's stated i_size. This is almost certainly
|
|
* not the function you want to call. Use page_cache_async_readahead()
|
|
* or page_cache_sync_readahead() instead.
|
|
*
|
|
* Context: File is referenced by caller. Mutexes may be held by caller.
|
|
* May sleep, but will not reenter filesystem to reclaim memory.
|
|
*/
|
|
void page_cache_ra_unbounded(struct readahead_control *ractl,
|
|
unsigned long nr_to_read, unsigned long lookahead_size)
|
|
{
|
|
struct address_space *mapping = ractl->mapping;
|
|
unsigned long index = readahead_index(ractl);
|
|
LIST_HEAD(page_pool);
|
|
gfp_t gfp_mask = readahead_gfp_mask(mapping);
|
|
unsigned long i;
|
|
|
|
/*
|
|
* Partway through the readahead operation, we will have added
|
|
* locked pages to the page cache, but will not yet have submitted
|
|
* them for I/O. Adding another page may need to allocate memory,
|
|
* which can trigger memory reclaim. Telling the VM we're in
|
|
* the middle of a filesystem operation will cause it to not
|
|
* touch file-backed pages, preventing a deadlock. Most (all?)
|
|
* filesystems already specify __GFP_NOFS in their mapping's
|
|
* gfp_mask, but let's be explicit here.
|
|
*/
|
|
unsigned int nofs = memalloc_nofs_save();
|
|
|
|
filemap_invalidate_lock_shared(mapping);
|
|
/*
|
|
* Preallocate as many pages as we will need.
|
|
*/
|
|
for (i = 0; i < nr_to_read; i++) {
|
|
struct page *page = xa_load(&mapping->i_pages, index + i);
|
|
|
|
if (page && !xa_is_value(page)) {
|
|
/*
|
|
* Page already present? Kick off the current batch
|
|
* of contiguous pages before continuing with the
|
|
* next batch. This page may be the one we would
|
|
* have intended to mark as Readahead, but we don't
|
|
* have a stable reference to this page, and it's
|
|
* not worth getting one just for that.
|
|
*/
|
|
read_pages(ractl, &page_pool, true);
|
|
i = ractl->_index + ractl->_nr_pages - index - 1;
|
|
continue;
|
|
}
|
|
|
|
page = __page_cache_alloc(gfp_mask);
|
|
if (!page)
|
|
break;
|
|
if (mapping->a_ops->readpages) {
|
|
page->index = index + i;
|
|
list_add(&page->lru, &page_pool);
|
|
} else if (add_to_page_cache_lru(page, mapping, index + i,
|
|
gfp_mask) < 0) {
|
|
put_page(page);
|
|
read_pages(ractl, &page_pool, true);
|
|
i = ractl->_index + ractl->_nr_pages - index - 1;
|
|
continue;
|
|
}
|
|
if (i == nr_to_read - lookahead_size)
|
|
SetPageReadahead(page);
|
|
ractl->_nr_pages++;
|
|
}
|
|
|
|
/*
|
|
* Now start the IO. We ignore I/O errors - if the page is not
|
|
* uptodate then the caller will launch readpage again, and
|
|
* will then handle the error.
|
|
*/
|
|
read_pages(ractl, &page_pool, false);
|
|
filemap_invalidate_unlock_shared(mapping);
|
|
memalloc_nofs_restore(nofs);
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);
|
|
|
|
/*
|
|
* do_page_cache_ra() actually reads a chunk of disk. It allocates
|
|
* the pages first, then submits them for I/O. This avoids the very bad
|
|
* behaviour which would occur if page allocations are causing VM writeback.
|
|
* We really don't want to intermingle reads and writes like that.
|
|
*/
|
|
void do_page_cache_ra(struct readahead_control *ractl,
|
|
unsigned long nr_to_read, unsigned long lookahead_size)
|
|
{
|
|
struct inode *inode = ractl->mapping->host;
|
|
unsigned long index = readahead_index(ractl);
|
|
loff_t isize = i_size_read(inode);
|
|
pgoff_t end_index; /* The last page we want to read */
|
|
|
|
if (isize == 0)
|
|
return;
|
|
|
|
end_index = (isize - 1) >> PAGE_SHIFT;
|
|
if (index > end_index)
|
|
return;
|
|
/* Don't read past the page containing the last byte of the file */
|
|
if (nr_to_read > end_index - index)
|
|
nr_to_read = end_index - index + 1;
|
|
|
|
page_cache_ra_unbounded(ractl, nr_to_read, lookahead_size);
|
|
}
|
|
|
|
/*
|
|
* Chunk the readahead into 2 megabyte units, so that we don't pin too much
|
|
* memory at once.
|
|
*/
|
|
void force_page_cache_ra(struct readahead_control *ractl,
|
|
unsigned long nr_to_read)
|
|
{
|
|
struct address_space *mapping = ractl->mapping;
|
|
struct file_ra_state *ra = ractl->ra;
|
|
struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
|
|
unsigned long max_pages, index;
|
|
|
|
if (unlikely(!mapping->a_ops->readpage && !mapping->a_ops->readpages &&
|
|
!mapping->a_ops->readahead))
|
|
return;
|
|
|
|
/*
|
|
* If the request exceeds the readahead window, allow the read to
|
|
* be up to the optimal hardware IO size
|
|
*/
|
|
index = readahead_index(ractl);
|
|
max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages);
|
|
nr_to_read = min_t(unsigned long, nr_to_read, max_pages);
|
|
while (nr_to_read) {
|
|
unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE;
|
|
|
|
if (this_chunk > nr_to_read)
|
|
this_chunk = nr_to_read;
|
|
ractl->_index = index;
|
|
do_page_cache_ra(ractl, this_chunk, 0);
|
|
|
|
index += this_chunk;
|
|
nr_to_read -= this_chunk;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Set the initial window size, round to next power of 2 and square
|
|
* for small size, x 4 for medium, and x 2 for large
|
|
* for 128k (32 page) max ra
|
|
* 1-8 page = 32k initial, > 8 page = 128k initial
|
|
*/
|
|
static unsigned long get_init_ra_size(unsigned long size, unsigned long max)
|
|
{
|
|
unsigned long newsize = roundup_pow_of_two(size);
|
|
|
|
if (newsize <= max / 32)
|
|
newsize = newsize * 4;
|
|
else if (newsize <= max / 4)
|
|
newsize = newsize * 2;
|
|
else
|
|
newsize = max;
|
|
|
|
return newsize;
|
|
}
|
|
|
|
/*
|
|
* Get the previous window size, ramp it up, and
|
|
* return it as the new window size.
|
|
*/
|
|
static unsigned long get_next_ra_size(struct file_ra_state *ra,
|
|
unsigned long max)
|
|
{
|
|
unsigned long cur = ra->size;
|
|
|
|
if (cur < max / 16)
|
|
return 4 * cur;
|
|
if (cur <= max / 2)
|
|
return 2 * cur;
|
|
return max;
|
|
}
|
|
|
|
/*
|
|
* On-demand readahead design.
|
|
*
|
|
* The fields in struct file_ra_state represent the most-recently-executed
|
|
* readahead attempt:
|
|
*
|
|
* |<----- async_size ---------|
|
|
* |------------------- size -------------------->|
|
|
* |==================#===========================|
|
|
* ^start ^page marked with PG_readahead
|
|
*
|
|
* To overlap application thinking time and disk I/O time, we do
|
|
* `readahead pipelining': Do not wait until the application consumed all
|
|
* readahead pages and stalled on the missing page at readahead_index;
|
|
* Instead, submit an asynchronous readahead I/O as soon as there are
|
|
* only async_size pages left in the readahead window. Normally async_size
|
|
* will be equal to size, for maximum pipelining.
|
|
*
|
|
* In interleaved sequential reads, concurrent streams on the same fd can
|
|
* be invalidating each other's readahead state. So we flag the new readahead
|
|
* page at (start+size-async_size) with PG_readahead, and use it as readahead
|
|
* indicator. The flag won't be set on already cached pages, to avoid the
|
|
* readahead-for-nothing fuss, saving pointless page cache lookups.
|
|
*
|
|
* prev_pos tracks the last visited byte in the _previous_ read request.
|
|
* It should be maintained by the caller, and will be used for detecting
|
|
* small random reads. Note that the readahead algorithm checks loosely
|
|
* for sequential patterns. Hence interleaved reads might be served as
|
|
* sequential ones.
|
|
*
|
|
* There is a special-case: if the first page which the application tries to
|
|
* read happens to be the first page of the file, it is assumed that a linear
|
|
* read is about to happen and the window is immediately set to the initial size
|
|
* based on I/O request size and the max_readahead.
|
|
*
|
|
* The code ramps up the readahead size aggressively at first, but slow down as
|
|
* it approaches max_readhead.
|
|
*/
|
|
|
|
/*
|
|
* Count contiguously cached pages from @index-1 to @index-@max,
|
|
* this count is a conservative estimation of
|
|
* - length of the sequential read sequence, or
|
|
* - thrashing threshold in memory tight systems
|
|
*/
|
|
static pgoff_t count_history_pages(struct address_space *mapping,
|
|
pgoff_t index, unsigned long max)
|
|
{
|
|
pgoff_t head;
|
|
|
|
rcu_read_lock();
|
|
head = page_cache_prev_miss(mapping, index - 1, max);
|
|
rcu_read_unlock();
|
|
|
|
return index - 1 - head;
|
|
}
|
|
|
|
/*
|
|
* page cache context based read-ahead
|
|
*/
|
|
static int try_context_readahead(struct address_space *mapping,
|
|
struct file_ra_state *ra,
|
|
pgoff_t index,
|
|
unsigned long req_size,
|
|
unsigned long max)
|
|
{
|
|
pgoff_t size;
|
|
|
|
size = count_history_pages(mapping, index, max);
|
|
|
|
/*
|
|
* not enough history pages:
|
|
* it could be a random read
|
|
*/
|
|
if (size <= req_size)
|
|
return 0;
|
|
|
|
/*
|
|
* starts from beginning of file:
|
|
* it is a strong indication of long-run stream (or whole-file-read)
|
|
*/
|
|
if (size >= index)
|
|
size *= 2;
|
|
|
|
ra->start = index;
|
|
ra->size = min(size + req_size, max);
|
|
ra->async_size = 1;
|
|
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* A minimal readahead algorithm for trivial sequential/random reads.
|
|
*/
|
|
static void ondemand_readahead(struct readahead_control *ractl,
|
|
bool hit_readahead_marker, unsigned long req_size)
|
|
{
|
|
struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host);
|
|
struct file_ra_state *ra = ractl->ra;
|
|
unsigned long max_pages = ra->ra_pages;
|
|
unsigned long add_pages;
|
|
unsigned long index = readahead_index(ractl);
|
|
pgoff_t prev_index;
|
|
|
|
/*
|
|
* If the request exceeds the readahead window, allow the read to
|
|
* be up to the optimal hardware IO size
|
|
*/
|
|
if (req_size > max_pages && bdi->io_pages > max_pages)
|
|
max_pages = min(req_size, bdi->io_pages);
|
|
|
|
/*
|
|
* start of file
|
|
*/
|
|
if (!index)
|
|
goto initial_readahead;
|
|
|
|
/*
|
|
* It's the expected callback index, assume sequential access.
|
|
* Ramp up sizes, and push forward the readahead window.
|
|
*/
|
|
if ((index == (ra->start + ra->size - ra->async_size) ||
|
|
index == (ra->start + ra->size))) {
|
|
ra->start += ra->size;
|
|
ra->size = get_next_ra_size(ra, max_pages);
|
|
ra->async_size = ra->size;
|
|
goto readit;
|
|
}
|
|
|
|
/*
|
|
* Hit a marked page without valid readahead state.
|
|
* E.g. interleaved reads.
|
|
* Query the pagecache for async_size, which normally equals to
|
|
* readahead size. Ramp it up and use it as the new readahead size.
|
|
*/
|
|
if (hit_readahead_marker) {
|
|
pgoff_t start;
|
|
|
|
rcu_read_lock();
|
|
start = page_cache_next_miss(ractl->mapping, index + 1,
|
|
max_pages);
|
|
rcu_read_unlock();
|
|
|
|
if (!start || start - index > max_pages)
|
|
return;
|
|
|
|
ra->start = start;
|
|
ra->size = start - index; /* old async_size */
|
|
ra->size += req_size;
|
|
ra->size = get_next_ra_size(ra, max_pages);
|
|
ra->async_size = ra->size;
|
|
goto readit;
|
|
}
|
|
|
|
/*
|
|
* oversize read
|
|
*/
|
|
if (req_size > max_pages)
|
|
goto initial_readahead;
|
|
|
|
/*
|
|
* sequential cache miss
|
|
* trivial case: (index - prev_index) == 1
|
|
* unaligned reads: (index - prev_index) == 0
|
|
*/
|
|
prev_index = (unsigned long long)ra->prev_pos >> PAGE_SHIFT;
|
|
if (index - prev_index <= 1UL)
|
|
goto initial_readahead;
|
|
|
|
/*
|
|
* Query the page cache and look for the traces(cached history pages)
|
|
* that a sequential stream would leave behind.
|
|
*/
|
|
if (try_context_readahead(ractl->mapping, ra, index, req_size,
|
|
max_pages))
|
|
goto readit;
|
|
|
|
/*
|
|
* standalone, small random read
|
|
* Read as is, and do not pollute the readahead state.
|
|
*/
|
|
do_page_cache_ra(ractl, req_size, 0);
|
|
return;
|
|
|
|
initial_readahead:
|
|
ra->start = index;
|
|
ra->size = get_init_ra_size(req_size, max_pages);
|
|
ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size;
|
|
|
|
readit:
|
|
/*
|
|
* Will this read hit the readahead marker made by itself?
|
|
* If so, trigger the readahead marker hit now, and merge
|
|
* the resulted next readahead window into the current one.
|
|
* Take care of maximum IO pages as above.
|
|
*/
|
|
if (index == ra->start && ra->size == ra->async_size) {
|
|
add_pages = get_next_ra_size(ra, max_pages);
|
|
if (ra->size + add_pages <= max_pages) {
|
|
ra->async_size = add_pages;
|
|
ra->size += add_pages;
|
|
} else {
|
|
ra->size = max_pages;
|
|
ra->async_size = max_pages >> 1;
|
|
}
|
|
}
|
|
|
|
ractl->_index = ra->start;
|
|
do_page_cache_ra(ractl, ra->size, ra->async_size);
|
|
}
|
|
|
|
void page_cache_sync_ra(struct readahead_control *ractl,
|
|
unsigned long req_count)
|
|
{
|
|
bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
|
|
|
|
/*
|
|
* Even if read-ahead is disabled, issue this request as read-ahead
|
|
* as we'll need it to satisfy the requested range. The forced
|
|
* read-ahead will do the right thing and limit the read to just the
|
|
* requested range, which we'll set to 1 page for this case.
|
|
*/
|
|
if (!ractl->ra->ra_pages || blk_cgroup_congested()) {
|
|
if (!ractl->file)
|
|
return;
|
|
req_count = 1;
|
|
do_forced_ra = true;
|
|
}
|
|
|
|
/* be dumb */
|
|
if (do_forced_ra) {
|
|
force_page_cache_ra(ractl, req_count);
|
|
return;
|
|
}
|
|
|
|
/* do read-ahead */
|
|
ondemand_readahead(ractl, false, req_count);
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_cache_sync_ra);
|
|
|
|
void page_cache_async_ra(struct readahead_control *ractl,
|
|
struct page *page, unsigned long req_count)
|
|
{
|
|
/* no read-ahead */
|
|
if (!ractl->ra->ra_pages)
|
|
return;
|
|
|
|
/*
|
|
* Same bit is used for PG_readahead and PG_reclaim.
|
|
*/
|
|
if (PageWriteback(page))
|
|
return;
|
|
|
|
ClearPageReadahead(page);
|
|
|
|
/*
|
|
* Defer asynchronous read-ahead on IO congestion.
|
|
*/
|
|
if (inode_read_congested(ractl->mapping->host))
|
|
return;
|
|
|
|
if (blk_cgroup_congested())
|
|
return;
|
|
|
|
/* do read-ahead */
|
|
ondemand_readahead(ractl, true, req_count);
|
|
}
|
|
EXPORT_SYMBOL_GPL(page_cache_async_ra);
|
|
|
|
ssize_t ksys_readahead(int fd, loff_t offset, size_t count)
|
|
{
|
|
ssize_t ret;
|
|
struct fd f;
|
|
|
|
ret = -EBADF;
|
|
f = fdget(fd);
|
|
if (!f.file || !(f.file->f_mode & FMODE_READ))
|
|
goto out;
|
|
|
|
/*
|
|
* The readahead() syscall is intended to run only on files
|
|
* that can execute readahead. If readahead is not possible
|
|
* on this file, then we must return -EINVAL.
|
|
*/
|
|
ret = -EINVAL;
|
|
if (!f.file->f_mapping || !f.file->f_mapping->a_ops ||
|
|
!S_ISREG(file_inode(f.file)->i_mode))
|
|
goto out;
|
|
|
|
ret = vfs_fadvise(f.file, offset, count, POSIX_FADV_WILLNEED);
|
|
out:
|
|
fdput(f);
|
|
return ret;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)
|
|
{
|
|
return ksys_readahead(fd, offset, count);
|
|
}
|
|
|
|
/**
|
|
* readahead_expand - Expand a readahead request
|
|
* @ractl: The request to be expanded
|
|
* @new_start: The revised start
|
|
* @new_len: The revised size of the request
|
|
*
|
|
* Attempt to expand a readahead request outwards from the current size to the
|
|
* specified size by inserting locked pages before and after the current window
|
|
* to increase the size to the new window. This may involve the insertion of
|
|
* THPs, in which case the window may get expanded even beyond what was
|
|
* requested.
|
|
*
|
|
* The algorithm will stop if it encounters a conflicting page already in the
|
|
* pagecache and leave a smaller expansion than requested.
|
|
*
|
|
* The caller must check for this by examining the revised @ractl object for a
|
|
* different expansion than was requested.
|
|
*/
|
|
void readahead_expand(struct readahead_control *ractl,
|
|
loff_t new_start, size_t new_len)
|
|
{
|
|
struct address_space *mapping = ractl->mapping;
|
|
struct file_ra_state *ra = ractl->ra;
|
|
pgoff_t new_index, new_nr_pages;
|
|
gfp_t gfp_mask = readahead_gfp_mask(mapping);
|
|
|
|
new_index = new_start / PAGE_SIZE;
|
|
|
|
/* Expand the leading edge downwards */
|
|
while (ractl->_index > new_index) {
|
|
unsigned long index = ractl->_index - 1;
|
|
struct page *page = xa_load(&mapping->i_pages, index);
|
|
|
|
if (page && !xa_is_value(page))
|
|
return; /* Page apparently present */
|
|
|
|
page = __page_cache_alloc(gfp_mask);
|
|
if (!page)
|
|
return;
|
|
if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
|
|
put_page(page);
|
|
return;
|
|
}
|
|
|
|
ractl->_nr_pages++;
|
|
ractl->_index = page->index;
|
|
}
|
|
|
|
new_len += new_start - readahead_pos(ractl);
|
|
new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE);
|
|
|
|
/* Expand the trailing edge upwards */
|
|
while (ractl->_nr_pages < new_nr_pages) {
|
|
unsigned long index = ractl->_index + ractl->_nr_pages;
|
|
struct page *page = xa_load(&mapping->i_pages, index);
|
|
|
|
if (page && !xa_is_value(page))
|
|
return; /* Page apparently present */
|
|
|
|
page = __page_cache_alloc(gfp_mask);
|
|
if (!page)
|
|
return;
|
|
if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
|
|
put_page(page);
|
|
return;
|
|
}
|
|
ractl->_nr_pages++;
|
|
if (ra) {
|
|
ra->size++;
|
|
ra->async_size++;
|
|
}
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(readahead_expand);
|