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linux-next/fs/afs/file.c
David Howells 5a81327616 afs: Do better accretion of small writes on newly created content
Processes like ld that do lots of small writes that aren't necessarily
contiguous result in a lot of small StoreData operations to the server, the
idea being that if someone else changes the data on the server, we only
write our changes over that and not the space between.  Further, we don't
want to write back empty space if we can avoid it to make it easier for the
server to do sparse files.

However, making lots of tiny RPC ops is a lot less efficient for the server
than one big one because each op requires allocation of resources and the
taking of locks, so we want to compromise a bit.

Reduce the load by the following:

 (1) If a file is just created locally or has just been truncated with
     O_TRUNC locally, allow subsequent writes to the file to be merged with
     intervening space if that space doesn't cross an entire intervening
     page.

 (2) Don't flush the file on ->flush() but rather on ->release() if the
     file was open for writing.

Just linking vmlinux.o, without this patch, looking in /proc/fs/afs/stats:

	file-wr : n=441 nb=513581204

and after the patch:

	file-wr : n=62 nb=513668555

there were 379 fewer StoreData RPC operations at the expense of an extra
87K being written.

Signed-off-by: David Howells <dhowells@redhat.com>
2018-04-09 21:54:48 +01:00

675 lines
15 KiB
C

/* AFS filesystem file handling
*
* Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/gfp.h>
#include <linux/task_io_accounting_ops.h>
#include "internal.h"
static int afs_file_mmap(struct file *file, struct vm_area_struct *vma);
static int afs_readpage(struct file *file, struct page *page);
static void afs_invalidatepage(struct page *page, unsigned int offset,
unsigned int length);
static int afs_releasepage(struct page *page, gfp_t gfp_flags);
static int afs_readpages(struct file *filp, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages);
const struct file_operations afs_file_operations = {
.open = afs_open,
.release = afs_release,
.llseek = generic_file_llseek,
.read_iter = generic_file_read_iter,
.write_iter = afs_file_write,
.mmap = afs_file_mmap,
.splice_read = generic_file_splice_read,
.fsync = afs_fsync,
.lock = afs_lock,
.flock = afs_flock,
};
const struct inode_operations afs_file_inode_operations = {
.getattr = afs_getattr,
.setattr = afs_setattr,
.permission = afs_permission,
.listxattr = afs_listxattr,
};
const struct address_space_operations afs_fs_aops = {
.readpage = afs_readpage,
.readpages = afs_readpages,
.set_page_dirty = afs_set_page_dirty,
.launder_page = afs_launder_page,
.releasepage = afs_releasepage,
.invalidatepage = afs_invalidatepage,
.write_begin = afs_write_begin,
.write_end = afs_write_end,
.writepage = afs_writepage,
.writepages = afs_writepages,
};
static const struct vm_operations_struct afs_vm_ops = {
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = afs_page_mkwrite,
};
/*
* Discard a pin on a writeback key.
*/
void afs_put_wb_key(struct afs_wb_key *wbk)
{
if (refcount_dec_and_test(&wbk->usage)) {
key_put(wbk->key);
kfree(wbk);
}
}
/*
* Cache key for writeback.
*/
int afs_cache_wb_key(struct afs_vnode *vnode, struct afs_file *af)
{
struct afs_wb_key *wbk, *p;
wbk = kzalloc(sizeof(struct afs_wb_key), GFP_KERNEL);
if (!wbk)
return -ENOMEM;
refcount_set(&wbk->usage, 2);
wbk->key = af->key;
spin_lock(&vnode->wb_lock);
list_for_each_entry(p, &vnode->wb_keys, vnode_link) {
if (p->key == wbk->key)
goto found;
}
key_get(wbk->key);
list_add_tail(&wbk->vnode_link, &vnode->wb_keys);
spin_unlock(&vnode->wb_lock);
af->wb = wbk;
return 0;
found:
refcount_inc(&p->usage);
spin_unlock(&vnode->wb_lock);
af->wb = p;
kfree(wbk);
return 0;
}
/*
* open an AFS file or directory and attach a key to it
*/
int afs_open(struct inode *inode, struct file *file)
{
struct afs_vnode *vnode = AFS_FS_I(inode);
struct afs_file *af;
struct key *key;
int ret;
_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
key = afs_request_key(vnode->volume->cell);
if (IS_ERR(key)) {
ret = PTR_ERR(key);
goto error;
}
af = kzalloc(sizeof(*af), GFP_KERNEL);
if (!af) {
ret = -ENOMEM;
goto error_key;
}
af->key = key;
ret = afs_validate(vnode, key);
if (ret < 0)
goto error_af;
if (file->f_mode & FMODE_WRITE) {
ret = afs_cache_wb_key(vnode, af);
if (ret < 0)
goto error_af;
}
if (file->f_flags & O_TRUNC)
set_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
file->private_data = af;
_leave(" = 0");
return 0;
error_af:
kfree(af);
error_key:
key_put(key);
error:
_leave(" = %d", ret);
return ret;
}
/*
* release an AFS file or directory and discard its key
*/
int afs_release(struct inode *inode, struct file *file)
{
struct afs_vnode *vnode = AFS_FS_I(inode);
struct afs_file *af = file->private_data;
_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
if ((file->f_mode & FMODE_WRITE))
return vfs_fsync(file, 0);
file->private_data = NULL;
if (af->wb)
afs_put_wb_key(af->wb);
key_put(af->key);
kfree(af);
afs_prune_wb_keys(vnode);
_leave(" = 0");
return 0;
}
/*
* Dispose of a ref to a read record.
*/
void afs_put_read(struct afs_read *req)
{
int i;
if (refcount_dec_and_test(&req->usage)) {
for (i = 0; i < req->nr_pages; i++)
if (req->pages[i])
put_page(req->pages[i]);
if (req->pages != req->array)
kfree(req->pages);
kfree(req);
}
}
#ifdef CONFIG_AFS_FSCACHE
/*
* deal with notification that a page was read from the cache
*/
static void afs_file_readpage_read_complete(struct page *page,
void *data,
int error)
{
_enter("%p,%p,%d", page, data, error);
/* if the read completes with an error, we just unlock the page and let
* the VM reissue the readpage */
if (!error)
SetPageUptodate(page);
unlock_page(page);
}
#endif
/*
* Fetch file data from the volume.
*/
int afs_fetch_data(struct afs_vnode *vnode, struct key *key, struct afs_read *desc)
{
struct afs_fs_cursor fc;
int ret;
_enter("%s{%x:%u.%u},%x,,,",
vnode->volume->name,
vnode->fid.vid,
vnode->fid.vnode,
vnode->fid.unique,
key_serial(key));
ret = -ERESTARTSYS;
if (afs_begin_vnode_operation(&fc, vnode, key)) {
while (afs_select_fileserver(&fc)) {
fc.cb_break = vnode->cb_break + vnode->cb_s_break;
afs_fs_fetch_data(&fc, desc);
}
afs_check_for_remote_deletion(&fc, fc.vnode);
afs_vnode_commit_status(&fc, vnode, fc.cb_break);
ret = afs_end_vnode_operation(&fc);
}
if (ret == 0) {
afs_stat_v(vnode, n_fetches);
atomic_long_add(desc->actual_len,
&afs_v2net(vnode)->n_fetch_bytes);
}
_leave(" = %d", ret);
return ret;
}
/*
* read page from file, directory or symlink, given a key to use
*/
int afs_page_filler(void *data, struct page *page)
{
struct inode *inode = page->mapping->host;
struct afs_vnode *vnode = AFS_FS_I(inode);
struct afs_read *req;
struct key *key = data;
int ret;
_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
BUG_ON(!PageLocked(page));
ret = -ESTALE;
if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
goto error;
/* is it cached? */
#ifdef CONFIG_AFS_FSCACHE
ret = fscache_read_or_alloc_page(vnode->cache,
page,
afs_file_readpage_read_complete,
NULL,
GFP_KERNEL);
#else
ret = -ENOBUFS;
#endif
switch (ret) {
/* read BIO submitted (page in cache) */
case 0:
break;
/* page not yet cached */
case -ENODATA:
_debug("cache said ENODATA");
goto go_on;
/* page will not be cached */
case -ENOBUFS:
_debug("cache said ENOBUFS");
default:
go_on:
req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *),
GFP_KERNEL);
if (!req)
goto enomem;
/* We request a full page. If the page is a partial one at the
* end of the file, the server will return a short read and the
* unmarshalling code will clear the unfilled space.
*/
refcount_set(&req->usage, 1);
req->pos = (loff_t)page->index << PAGE_SHIFT;
req->len = PAGE_SIZE;
req->nr_pages = 1;
req->pages = req->array;
req->pages[0] = page;
get_page(page);
/* read the contents of the file from the server into the
* page */
ret = afs_fetch_data(vnode, key, req);
afs_put_read(req);
if (ret < 0) {
if (ret == -ENOENT) {
_debug("got NOENT from server"
" - marking file deleted and stale");
set_bit(AFS_VNODE_DELETED, &vnode->flags);
ret = -ESTALE;
}
#ifdef CONFIG_AFS_FSCACHE
fscache_uncache_page(vnode->cache, page);
#endif
BUG_ON(PageFsCache(page));
if (ret == -EINTR ||
ret == -ENOMEM ||
ret == -ERESTARTSYS ||
ret == -EAGAIN)
goto error;
goto io_error;
}
SetPageUptodate(page);
/* send the page to the cache */
#ifdef CONFIG_AFS_FSCACHE
if (PageFsCache(page) &&
fscache_write_page(vnode->cache, page, vnode->status.size,
GFP_KERNEL) != 0) {
fscache_uncache_page(vnode->cache, page);
BUG_ON(PageFsCache(page));
}
#endif
unlock_page(page);
}
_leave(" = 0");
return 0;
io_error:
SetPageError(page);
goto error;
enomem:
ret = -ENOMEM;
error:
unlock_page(page);
_leave(" = %d", ret);
return ret;
}
/*
* read page from file, directory or symlink, given a file to nominate the key
* to be used
*/
static int afs_readpage(struct file *file, struct page *page)
{
struct key *key;
int ret;
if (file) {
key = afs_file_key(file);
ASSERT(key != NULL);
ret = afs_page_filler(key, page);
} else {
struct inode *inode = page->mapping->host;
key = afs_request_key(AFS_FS_S(inode->i_sb)->cell);
if (IS_ERR(key)) {
ret = PTR_ERR(key);
} else {
ret = afs_page_filler(key, page);
key_put(key);
}
}
return ret;
}
/*
* Make pages available as they're filled.
*/
static void afs_readpages_page_done(struct afs_call *call, struct afs_read *req)
{
#ifdef CONFIG_AFS_FSCACHE
struct afs_vnode *vnode = call->reply[0];
#endif
struct page *page = req->pages[req->index];
req->pages[req->index] = NULL;
SetPageUptodate(page);
/* send the page to the cache */
#ifdef CONFIG_AFS_FSCACHE
if (PageFsCache(page) &&
fscache_write_page(vnode->cache, page, vnode->status.size,
GFP_KERNEL) != 0) {
fscache_uncache_page(vnode->cache, page);
BUG_ON(PageFsCache(page));
}
#endif
unlock_page(page);
put_page(page);
}
/*
* Read a contiguous set of pages.
*/
static int afs_readpages_one(struct file *file, struct address_space *mapping,
struct list_head *pages)
{
struct afs_vnode *vnode = AFS_FS_I(mapping->host);
struct afs_read *req;
struct list_head *p;
struct page *first, *page;
struct key *key = afs_file_key(file);
pgoff_t index;
int ret, n, i;
/* Count the number of contiguous pages at the front of the list. Note
* that the list goes prev-wards rather than next-wards.
*/
first = list_entry(pages->prev, struct page, lru);
index = first->index + 1;
n = 1;
for (p = first->lru.prev; p != pages; p = p->prev) {
page = list_entry(p, struct page, lru);
if (page->index != index)
break;
index++;
n++;
}
req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *) * n,
GFP_NOFS);
if (!req)
return -ENOMEM;
refcount_set(&req->usage, 1);
req->page_done = afs_readpages_page_done;
req->pos = first->index;
req->pos <<= PAGE_SHIFT;
req->pages = req->array;
/* Transfer the pages to the request. We add them in until one fails
* to add to the LRU and then we stop (as that'll make a hole in the
* contiguous run.
*
* Note that it's possible for the file size to change whilst we're
* doing this, but we rely on the server returning less than we asked
* for if the file shrank. We also rely on this to deal with a partial
* page at the end of the file.
*/
do {
page = list_entry(pages->prev, struct page, lru);
list_del(&page->lru);
index = page->index;
if (add_to_page_cache_lru(page, mapping, index,
readahead_gfp_mask(mapping))) {
#ifdef CONFIG_AFS_FSCACHE
fscache_uncache_page(vnode->cache, page);
#endif
put_page(page);
break;
}
req->pages[req->nr_pages++] = page;
req->len += PAGE_SIZE;
} while (req->nr_pages < n);
if (req->nr_pages == 0) {
kfree(req);
return 0;
}
ret = afs_fetch_data(vnode, key, req);
if (ret < 0)
goto error;
task_io_account_read(PAGE_SIZE * req->nr_pages);
afs_put_read(req);
return 0;
error:
if (ret == -ENOENT) {
_debug("got NOENT from server"
" - marking file deleted and stale");
set_bit(AFS_VNODE_DELETED, &vnode->flags);
ret = -ESTALE;
}
for (i = 0; i < req->nr_pages; i++) {
page = req->pages[i];
if (page) {
#ifdef CONFIG_AFS_FSCACHE
fscache_uncache_page(vnode->cache, page);
#endif
SetPageError(page);
unlock_page(page);
}
}
afs_put_read(req);
return ret;
}
/*
* read a set of pages
*/
static int afs_readpages(struct file *file, struct address_space *mapping,
struct list_head *pages, unsigned nr_pages)
{
struct key *key = afs_file_key(file);
struct afs_vnode *vnode;
int ret = 0;
_enter("{%d},{%lu},,%d",
key_serial(key), mapping->host->i_ino, nr_pages);
ASSERT(key != NULL);
vnode = AFS_FS_I(mapping->host);
if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
_leave(" = -ESTALE");
return -ESTALE;
}
/* attempt to read as many of the pages as possible */
#ifdef CONFIG_AFS_FSCACHE
ret = fscache_read_or_alloc_pages(vnode->cache,
mapping,
pages,
&nr_pages,
afs_file_readpage_read_complete,
NULL,
mapping_gfp_mask(mapping));
#else
ret = -ENOBUFS;
#endif
switch (ret) {
/* all pages are being read from the cache */
case 0:
BUG_ON(!list_empty(pages));
BUG_ON(nr_pages != 0);
_leave(" = 0 [reading all]");
return 0;
/* there were pages that couldn't be read from the cache */
case -ENODATA:
case -ENOBUFS:
break;
/* other error */
default:
_leave(" = %d", ret);
return ret;
}
while (!list_empty(pages)) {
ret = afs_readpages_one(file, mapping, pages);
if (ret < 0)
break;
}
_leave(" = %d [netting]", ret);
return ret;
}
/*
* invalidate part or all of a page
* - release a page and clean up its private data if offset is 0 (indicating
* the entire page)
*/
static void afs_invalidatepage(struct page *page, unsigned int offset,
unsigned int length)
{
struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
unsigned long priv;
_enter("{%lu},%u,%u", page->index, offset, length);
BUG_ON(!PageLocked(page));
/* we clean up only if the entire page is being invalidated */
if (offset == 0 && length == PAGE_SIZE) {
#ifdef CONFIG_AFS_FSCACHE
if (PageFsCache(page)) {
struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
fscache_wait_on_page_write(vnode->cache, page);
fscache_uncache_page(vnode->cache, page);
}
#endif
if (PagePrivate(page)) {
priv = page_private(page);
trace_afs_page_dirty(vnode, tracepoint_string("inval"),
page->index, priv);
set_page_private(page, 0);
ClearPagePrivate(page);
}
}
_leave("");
}
/*
* release a page and clean up its private state if it's not busy
* - return true if the page can now be released, false if not
*/
static int afs_releasepage(struct page *page, gfp_t gfp_flags)
{
struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
unsigned long priv;
_enter("{{%x:%u}[%lu],%lx},%x",
vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
gfp_flags);
/* deny if page is being written to the cache and the caller hasn't
* elected to wait */
#ifdef CONFIG_AFS_FSCACHE
if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
_leave(" = F [cache busy]");
return 0;
}
#endif
if (PagePrivate(page)) {
priv = page_private(page);
trace_afs_page_dirty(vnode, tracepoint_string("rel"),
page->index, priv);
set_page_private(page, 0);
ClearPagePrivate(page);
}
/* indicate that the page can be released */
_leave(" = T");
return 1;
}
/*
* Handle setting up a memory mapping on an AFS file.
*/
static int afs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
int ret;
ret = generic_file_mmap(file, vma);
if (ret == 0)
vma->vm_ops = &afs_vm_ops;
return ret;
}