linux/fs/ext4/page-io.c
Jan Kara 5c27088b3b ext4: drop pointless IO submission from ext4_bio_write_page()
We submit outstanding IO in ext4_bio_write_page() if we find a buffer we
are not going to write. This is however pointless because we already
handle submission of previous IO in case we detect newly added buffer
head is discontiguous. So just delete the pointless IO submission call.

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221207112722.22220-4-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2022-12-08 21:49:25 -05:00

571 lines
15 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/ext4/page-io.c
*
* This contains the new page_io functions for ext4
*
* Written by Theodore Ts'o, 2010.
*/
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/mpage.h>
#include <linux/namei.h>
#include <linux/uio.h>
#include <linux/bio.h>
#include <linux/workqueue.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"
static struct kmem_cache *io_end_cachep;
static struct kmem_cache *io_end_vec_cachep;
int __init ext4_init_pageio(void)
{
io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
if (io_end_cachep == NULL)
return -ENOMEM;
io_end_vec_cachep = KMEM_CACHE(ext4_io_end_vec, 0);
if (io_end_vec_cachep == NULL) {
kmem_cache_destroy(io_end_cachep);
return -ENOMEM;
}
return 0;
}
void ext4_exit_pageio(void)
{
kmem_cache_destroy(io_end_cachep);
kmem_cache_destroy(io_end_vec_cachep);
}
struct ext4_io_end_vec *ext4_alloc_io_end_vec(ext4_io_end_t *io_end)
{
struct ext4_io_end_vec *io_end_vec;
io_end_vec = kmem_cache_zalloc(io_end_vec_cachep, GFP_NOFS);
if (!io_end_vec)
return ERR_PTR(-ENOMEM);
INIT_LIST_HEAD(&io_end_vec->list);
list_add_tail(&io_end_vec->list, &io_end->list_vec);
return io_end_vec;
}
static void ext4_free_io_end_vec(ext4_io_end_t *io_end)
{
struct ext4_io_end_vec *io_end_vec, *tmp;
if (list_empty(&io_end->list_vec))
return;
list_for_each_entry_safe(io_end_vec, tmp, &io_end->list_vec, list) {
list_del(&io_end_vec->list);
kmem_cache_free(io_end_vec_cachep, io_end_vec);
}
}
struct ext4_io_end_vec *ext4_last_io_end_vec(ext4_io_end_t *io_end)
{
BUG_ON(list_empty(&io_end->list_vec));
return list_last_entry(&io_end->list_vec, struct ext4_io_end_vec, list);
}
/*
* Print an buffer I/O error compatible with the fs/buffer.c. This
* provides compatibility with dmesg scrapers that look for a specific
* buffer I/O error message. We really need a unified error reporting
* structure to userspace ala Digital Unix's uerf system, but it's
* probably not going to happen in my lifetime, due to LKML politics...
*/
static void buffer_io_error(struct buffer_head *bh)
{
printk_ratelimited(KERN_ERR "Buffer I/O error on device %pg, logical block %llu\n",
bh->b_bdev,
(unsigned long long)bh->b_blocknr);
}
static void ext4_finish_bio(struct bio *bio)
{
struct bio_vec *bvec;
struct bvec_iter_all iter_all;
bio_for_each_segment_all(bvec, bio, iter_all) {
struct page *page = bvec->bv_page;
struct page *bounce_page = NULL;
struct buffer_head *bh, *head;
unsigned bio_start = bvec->bv_offset;
unsigned bio_end = bio_start + bvec->bv_len;
unsigned under_io = 0;
unsigned long flags;
if (fscrypt_is_bounce_page(page)) {
bounce_page = page;
page = fscrypt_pagecache_page(bounce_page);
}
if (bio->bi_status) {
SetPageError(page);
mapping_set_error(page->mapping, -EIO);
}
bh = head = page_buffers(page);
/*
* We check all buffers in the page under b_uptodate_lock
* to avoid races with other end io clearing async_write flags
*/
spin_lock_irqsave(&head->b_uptodate_lock, flags);
do {
if (bh_offset(bh) < bio_start ||
bh_offset(bh) + bh->b_size > bio_end) {
if (buffer_async_write(bh))
under_io++;
continue;
}
clear_buffer_async_write(bh);
if (bio->bi_status) {
set_buffer_write_io_error(bh);
buffer_io_error(bh);
}
} while ((bh = bh->b_this_page) != head);
spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
if (!under_io) {
fscrypt_free_bounce_page(bounce_page);
end_page_writeback(page);
}
}
}
static void ext4_release_io_end(ext4_io_end_t *io_end)
{
struct bio *bio, *next_bio;
BUG_ON(!list_empty(&io_end->list));
BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
WARN_ON(io_end->handle);
for (bio = io_end->bio; bio; bio = next_bio) {
next_bio = bio->bi_private;
ext4_finish_bio(bio);
bio_put(bio);
}
ext4_free_io_end_vec(io_end);
kmem_cache_free(io_end_cachep, io_end);
}
/*
* Check a range of space and convert unwritten extents to written. Note that
* we are protected from truncate touching same part of extent tree by the
* fact that truncate code waits for all DIO to finish (thus exclusion from
* direct IO is achieved) and also waits for PageWriteback bits. Thus we
* cannot get to ext4_ext_truncate() before all IOs overlapping that range are
* completed (happens from ext4_free_ioend()).
*/
static int ext4_end_io_end(ext4_io_end_t *io_end)
{
struct inode *inode = io_end->inode;
handle_t *handle = io_end->handle;
int ret = 0;
ext4_debug("ext4_end_io_nolock: io_end 0x%p from inode %lu,list->next 0x%p,"
"list->prev 0x%p\n",
io_end, inode->i_ino, io_end->list.next, io_end->list.prev);
io_end->handle = NULL; /* Following call will use up the handle */
ret = ext4_convert_unwritten_io_end_vec(handle, io_end);
if (ret < 0 && !ext4_forced_shutdown(EXT4_SB(inode->i_sb))) {
ext4_msg(inode->i_sb, KERN_EMERG,
"failed to convert unwritten extents to written "
"extents -- potential data loss! "
"(inode %lu, error %d)", inode->i_ino, ret);
}
ext4_clear_io_unwritten_flag(io_end);
ext4_release_io_end(io_end);
return ret;
}
static void dump_completed_IO(struct inode *inode, struct list_head *head)
{
#ifdef EXT4FS_DEBUG
struct list_head *cur, *before, *after;
ext4_io_end_t *io_end, *io_end0, *io_end1;
if (list_empty(head))
return;
ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
list_for_each_entry(io_end, head, list) {
cur = &io_end->list;
before = cur->prev;
io_end0 = container_of(before, ext4_io_end_t, list);
after = cur->next;
io_end1 = container_of(after, ext4_io_end_t, list);
ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
io_end, inode->i_ino, io_end0, io_end1);
}
#endif
}
/* Add the io_end to per-inode completed end_io list. */
static void ext4_add_complete_io(ext4_io_end_t *io_end)
{
struct ext4_inode_info *ei = EXT4_I(io_end->inode);
struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);
struct workqueue_struct *wq;
unsigned long flags;
/* Only reserved conversions from writeback should enter here */
WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
WARN_ON(!io_end->handle && sbi->s_journal);
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
wq = sbi->rsv_conversion_wq;
if (list_empty(&ei->i_rsv_conversion_list))
queue_work(wq, &ei->i_rsv_conversion_work);
list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
}
static int ext4_do_flush_completed_IO(struct inode *inode,
struct list_head *head)
{
ext4_io_end_t *io_end;
struct list_head unwritten;
unsigned long flags;
struct ext4_inode_info *ei = EXT4_I(inode);
int err, ret = 0;
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
dump_completed_IO(inode, head);
list_replace_init(head, &unwritten);
spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
while (!list_empty(&unwritten)) {
io_end = list_entry(unwritten.next, ext4_io_end_t, list);
BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
list_del_init(&io_end->list);
err = ext4_end_io_end(io_end);
if (unlikely(!ret && err))
ret = err;
}
return ret;
}
/*
* work on completed IO, to convert unwritten extents to extents
*/
void ext4_end_io_rsv_work(struct work_struct *work)
{
struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
i_rsv_conversion_work);
ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
}
ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
{
ext4_io_end_t *io_end = kmem_cache_zalloc(io_end_cachep, flags);
if (io_end) {
io_end->inode = inode;
INIT_LIST_HEAD(&io_end->list);
INIT_LIST_HEAD(&io_end->list_vec);
refcount_set(&io_end->count, 1);
}
return io_end;
}
void ext4_put_io_end_defer(ext4_io_end_t *io_end)
{
if (refcount_dec_and_test(&io_end->count)) {
if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) ||
list_empty(&io_end->list_vec)) {
ext4_release_io_end(io_end);
return;
}
ext4_add_complete_io(io_end);
}
}
int ext4_put_io_end(ext4_io_end_t *io_end)
{
int err = 0;
if (refcount_dec_and_test(&io_end->count)) {
if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
err = ext4_convert_unwritten_io_end_vec(io_end->handle,
io_end);
io_end->handle = NULL;
ext4_clear_io_unwritten_flag(io_end);
}
ext4_release_io_end(io_end);
}
return err;
}
ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
{
refcount_inc(&io_end->count);
return io_end;
}
/* BIO completion function for page writeback */
static void ext4_end_bio(struct bio *bio)
{
ext4_io_end_t *io_end = bio->bi_private;
sector_t bi_sector = bio->bi_iter.bi_sector;
if (WARN_ONCE(!io_end, "io_end is NULL: %pg: sector %Lu len %u err %d\n",
bio->bi_bdev,
(long long) bio->bi_iter.bi_sector,
(unsigned) bio_sectors(bio),
bio->bi_status)) {
ext4_finish_bio(bio);
bio_put(bio);
return;
}
bio->bi_end_io = NULL;
if (bio->bi_status) {
struct inode *inode = io_end->inode;
ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
"starting block %llu)",
bio->bi_status, inode->i_ino,
(unsigned long long)
bi_sector >> (inode->i_blkbits - 9));
mapping_set_error(inode->i_mapping,
blk_status_to_errno(bio->bi_status));
}
if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
/*
* Link bio into list hanging from io_end. We have to do it
* atomically as bio completions can be racing against each
* other.
*/
bio->bi_private = xchg(&io_end->bio, bio);
ext4_put_io_end_defer(io_end);
} else {
/*
* Drop io_end reference early. Inode can get freed once
* we finish the bio.
*/
ext4_put_io_end_defer(io_end);
ext4_finish_bio(bio);
bio_put(bio);
}
}
void ext4_io_submit(struct ext4_io_submit *io)
{
struct bio *bio = io->io_bio;
if (bio) {
if (io->io_wbc->sync_mode == WB_SYNC_ALL)
io->io_bio->bi_opf |= REQ_SYNC;
submit_bio(io->io_bio);
}
io->io_bio = NULL;
}
void ext4_io_submit_init(struct ext4_io_submit *io,
struct writeback_control *wbc)
{
io->io_wbc = wbc;
io->io_bio = NULL;
io->io_end = NULL;
}
static void io_submit_init_bio(struct ext4_io_submit *io,
struct buffer_head *bh)
{
struct bio *bio;
/*
* bio_alloc will _always_ be able to allocate a bio if
* __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
*/
bio = bio_alloc(bh->b_bdev, BIO_MAX_VECS, REQ_OP_WRITE, GFP_NOIO);
fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
bio->bi_end_io = ext4_end_bio;
bio->bi_private = ext4_get_io_end(io->io_end);
io->io_bio = bio;
io->io_next_block = bh->b_blocknr;
wbc_init_bio(io->io_wbc, bio);
}
static void io_submit_add_bh(struct ext4_io_submit *io,
struct inode *inode,
struct page *page,
struct buffer_head *bh)
{
int ret;
if (io->io_bio && (bh->b_blocknr != io->io_next_block ||
!fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
submit_and_retry:
ext4_io_submit(io);
}
if (io->io_bio == NULL)
io_submit_init_bio(io, bh);
ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh));
if (ret != bh->b_size)
goto submit_and_retry;
wbc_account_cgroup_owner(io->io_wbc, page, bh->b_size);
io->io_next_block++;
}
int ext4_bio_write_page(struct ext4_io_submit *io,
struct page *page,
int len)
{
struct page *bounce_page = NULL;
struct inode *inode = page->mapping->host;
unsigned block_start;
struct buffer_head *bh, *head;
int ret = 0;
int nr_to_submit = 0;
struct writeback_control *wbc = io->io_wbc;
bool keep_towrite = false;
BUG_ON(!PageLocked(page));
BUG_ON(PageWriteback(page));
ClearPageError(page);
/*
* Comments copied from block_write_full_page:
*
* The page straddles i_size. It must be zeroed out on each and every
* writepage invocation because it may be mmapped. "A file is mapped
* in multiples of the page size. For a file that is not a multiple of
* the page size, the remaining memory is zeroed when mapped, and
* writes to that region are not written out to the file."
*/
if (len < PAGE_SIZE)
zero_user_segment(page, len, PAGE_SIZE);
/*
* In the first loop we prepare and mark buffers to submit. We have to
* mark all buffers in the page before submitting so that
* end_page_writeback() cannot be called from ext4_end_bio() when IO
* on the first buffer finishes and we are still working on submitting
* the second buffer.
*/
bh = head = page_buffers(page);
do {
block_start = bh_offset(bh);
if (block_start >= len) {
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
continue;
}
if (!buffer_dirty(bh) || buffer_delay(bh) ||
!buffer_mapped(bh) || buffer_unwritten(bh)) {
/* A hole? We can safely clear the dirty bit */
if (!buffer_mapped(bh))
clear_buffer_dirty(bh);
/*
* Keeping dirty some buffer we cannot write? Make sure
* to redirty the page and keep TOWRITE tag so that
* racing WB_SYNC_ALL writeback does not skip the page.
* This happens e.g. when doing writeout for
* transaction commit.
*/
if (buffer_dirty(bh)) {
if (!PageDirty(page))
redirty_page_for_writepage(wbc, page);
keep_towrite = true;
}
continue;
}
if (buffer_new(bh))
clear_buffer_new(bh);
set_buffer_async_write(bh);
clear_buffer_dirty(bh);
nr_to_submit++;
} while ((bh = bh->b_this_page) != head);
/* Nothing to submit? Just unlock the page... */
if (!nr_to_submit)
goto unlock;
bh = head = page_buffers(page);
/*
* If any blocks are being written to an encrypted file, encrypt them
* into a bounce page. For simplicity, just encrypt until the last
* block which might be needed. This may cause some unneeded blocks
* (e.g. holes) to be unnecessarily encrypted, but this is rare and
* can't happen in the common case of blocksize == PAGE_SIZE.
*/
if (fscrypt_inode_uses_fs_layer_crypto(inode) && nr_to_submit) {
gfp_t gfp_flags = GFP_NOFS;
unsigned int enc_bytes = round_up(len, i_blocksize(inode));
/*
* Since bounce page allocation uses a mempool, we can only use
* a waiting mask (i.e. request guaranteed allocation) on the
* first page of the bio. Otherwise it can deadlock.
*/
if (io->io_bio)
gfp_flags = GFP_NOWAIT | __GFP_NOWARN;
retry_encrypt:
bounce_page = fscrypt_encrypt_pagecache_blocks(page, enc_bytes,
0, gfp_flags);
if (IS_ERR(bounce_page)) {
ret = PTR_ERR(bounce_page);
if (ret == -ENOMEM &&
(io->io_bio || wbc->sync_mode == WB_SYNC_ALL)) {
gfp_t new_gfp_flags = GFP_NOFS;
if (io->io_bio)
ext4_io_submit(io);
else
new_gfp_flags |= __GFP_NOFAIL;
memalloc_retry_wait(gfp_flags);
gfp_flags = new_gfp_flags;
goto retry_encrypt;
}
printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
redirty_page_for_writepage(wbc, page);
do {
if (buffer_async_write(bh)) {
clear_buffer_async_write(bh);
set_buffer_dirty(bh);
}
bh = bh->b_this_page;
} while (bh != head);
goto unlock;
}
}
if (keep_towrite)
set_page_writeback_keepwrite(page);
else
set_page_writeback(page);
/* Now submit buffers to write */
do {
if (!buffer_async_write(bh))
continue;
io_submit_add_bh(io, inode,
bounce_page ? bounce_page : page, bh);
} while ((bh = bh->b_this_page) != head);
unlock:
unlock_page(page);
return ret;
}