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ext4: fix race in buffer_head read fault injection

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When I enabled ext4 debug for fault injection testing, I encountered the
following warning:

  EXT4-fs error (device sda): ext4_read_inode_bitmap:201: comm fsstress:
         Cannot read inode bitmap - block_group = 8, inode_bitmap = 1051
  WARNING: CPU: 0 PID: 511 at fs/buffer.c:1181 mark_buffer_dirty+0x1b3/0x1d0

The root cause of the issue lies in the improper implementation of ext4's
buffer_head read fault injection. The actual completion of buffer_head
read and the buffer_head fault injection are not atomic, which can lead
to the uptodate flag being cleared on normally used buffer_heads in race
conditions.

[CPU0]           [CPU1]         [CPU2]
ext4_read_inode_bitmap
  ext4_read_bh()
  <bh read complete>
                 ext4_read_inode_bitmap
                   if (buffer_uptodate(bh))
                     return bh
                               jbd2_journal_commit_transaction
                                 __jbd2_journal_refile_buffer
                                   __jbd2_journal_unfile_buffer
                                     __jbd2_journal_temp_unlink_buffer
  ext4_simulate_fail_bh()
    clear_buffer_uptodate
                                      mark_buffer_dirty
                                        <report warning>
                                        WARN_ON_ONCE(!buffer_uptodate(bh))

The best approach would be to perform fault injection in the IO completion
callback function, rather than after IO completion. However, the IO
completion callback function cannot get the fault injection code in sb.

Fix it by passing the result of fault injection into the bh read function,
we simulate faults within the bh read function itself. This requires adding
an extra parameter to the bh read functions that need fault injection.

Fixes: 46f870d690 ("ext4: simulate various I/O and checksum errors when reading metadata")
Signed-off-by: Long Li <leo.lilong@huawei.com>
Link: https://patch.msgid.link/20240906091746.510163-1-leo.lilong@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Long Li 2024-09-06 17:17:46 +08:00 committed by Theodore Ts'o
parent a90825898b
commit 2f3d93e210
10 changed files with 29 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/ext4/balloc.c
View File

@ -550,7 +550,8 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group,
trace_ext4_read_block_bitmap_load(sb, block_group, ignore_locked);
ext4_read_bh_nowait(bh, REQ_META | REQ_PRIO |
(ignore_locked ? REQ_RAHEAD : 0),
ext4_end_bitmap_read);
ext4_end_bitmap_read,
ext4_simulate_fail(sb, EXT4_SIM_BBITMAP_EIO));
return bh;
verify:
err = ext4_validate_block_bitmap(sb, desc, block_group, bh);
@ -577,7 +578,6 @@ int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
if (!desc)
return -EFSCORRUPTED;
wait_on_buffer(bh);
ext4_simulate_fail_bh(sb, bh, EXT4_SIM_BBITMAP_EIO);
if (!buffer_uptodate(bh)) {
ext4_error_err(sb, EIO, "Cannot read block bitmap - "
"block_group = %u, block_bitmap = %llu",

12
fs/ext4/ext4.h
View File

@ -1865,14 +1865,6 @@ static inline bool ext4_simulate_fail(struct super_block *sb,
return false;
}
static inline void ext4_simulate_fail_bh(struct super_block *sb,
struct buffer_head *bh,
unsigned long code)
{
if (!IS_ERR(bh) && ext4_simulate_fail(sb, code))
clear_buffer_uptodate(bh);
}
/*
* Error number codes for s_{first,last}_error_errno
*
@ -3100,9 +3092,9 @@ extern struct buffer_head *ext4_sb_bread(struct super_block *sb,
extern struct buffer_head *ext4_sb_bread_unmovable(struct super_block *sb,
sector_t block);
extern void ext4_read_bh_nowait(struct buffer_head *bh, blk_opf_t op_flags,
bh_end_io_t *end_io);
bh_end_io_t *end_io, bool simu_fail);
extern int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags,
bh_end_io_t *end_io);
bh_end_io_t *end_io, bool simu_fail);
extern int ext4_read_bh_lock(struct buffer_head *bh, blk_opf_t op_flags, bool wait);
extern void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block);
extern int ext4_seq_options_show(struct seq_file *seq, void *offset);

2
fs/ext4/extents.c
View File

@ -568,7 +568,7 @@ __read_extent_tree_block(const char *function, unsigned int line,
if (!bh_uptodate_or_lock(bh)) {
trace_ext4_ext_load_extent(inode, pblk, _RET_IP_);
err = ext4_read_bh(bh, 0, NULL);
err = ext4_read_bh(bh, 0, NULL, false);
if (err < 0)
goto errout;
}

5
fs/ext4/ialloc.c
View File

@ -193,8 +193,9 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
* submit the buffer_head for reading
*/
trace_ext4_load_inode_bitmap(sb, block_group);
ext4_read_bh(bh, REQ_META | REQ_PRIO, ext4_end_bitmap_read);
ext4_simulate_fail_bh(sb, bh, EXT4_SIM_IBITMAP_EIO);
ext4_read_bh(bh, REQ_META | REQ_PRIO,
ext4_end_bitmap_read,
ext4_simulate_fail(sb, EXT4_SIM_IBITMAP_EIO));
if (!buffer_uptodate(bh)) {
put_bh(bh);
ext4_error_err(sb, EIO, "Cannot read inode bitmap - "

2
fs/ext4/indirect.c
View File

@ -170,7 +170,7 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth,
}
if (!bh_uptodate_or_lock(bh)) {
if (ext4_read_bh(bh, 0, NULL) < 0) {
if (ext4_read_bh(bh, 0, NULL, false) < 0) {
put_bh(bh);
goto failure;
}

4
fs/ext4/inode.c
View File

@ -4504,10 +4504,10 @@ make_io:
* Read the block from disk.
*/
trace_ext4_load_inode(sb, ino);
ext4_read_bh_nowait(bh, REQ_META | REQ_PRIO, NULL);
ext4_read_bh_nowait(bh, REQ_META | REQ_PRIO, NULL,
ext4_simulate_fail(sb, EXT4_SIM_INODE_EIO));
blk_finish_plug(&plug);
wait_on_buffer(bh);
ext4_simulate_fail_bh(sb, bh, EXT4_SIM_INODE_EIO);
if (!buffer_uptodate(bh)) {
if (ret_block)
*ret_block = block;

2
fs/ext4/mmp.c
View File

@ -94,7 +94,7 @@ static int read_mmp_block(struct super_block *sb, struct buffer_head **bh,
}
lock_buffer(*bh);
ret = ext4_read_bh(*bh, REQ_META | REQ_PRIO, NULL);
ret = ext4_read_bh(*bh, REQ_META | REQ_PRIO, NULL, false);
if (ret)
goto warn_exit;

2
fs/ext4/move_extent.c
View File

@ -213,7 +213,7 @@ static int mext_page_mkuptodate(struct folio *folio, size_t from, size_t to)
unlock_buffer(bh);
continue;
}
ext4_read_bh_nowait(bh, 0, NULL);
ext4_read_bh_nowait(bh, 0, NULL, false);
nr++;
} while (block++, (bh = bh->b_this_page) != head);

2
fs/ext4/resize.c
View File

@ -1300,7 +1300,7 @@ static struct buffer_head *ext4_get_bitmap(struct super_block *sb, __u64 block)
if (unlikely(!bh))
return NULL;
if (!bh_uptodate_or_lock(bh)) {
if (ext4_read_bh(bh, 0, NULL) < 0) {
if (ext4_read_bh(bh, 0, NULL, false) < 0) {
brelse(bh);
return NULL;
}

23
fs/ext4/super.c
View File

@ -161,8 +161,14 @@ MODULE_ALIAS("ext3");
static inline void __ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags,
bh_end_io_t *end_io)
bh_end_io_t *end_io, bool simu_fail)
{
if (simu_fail) {
clear_buffer_uptodate(bh);
unlock_buffer(bh);
return;
}
/*
* buffer's verified bit is no longer valid after reading from
* disk again due to write out error, clear it to make sure we
@ -176,7 +182,7 @@ static inline void __ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags,
}
void ext4_read_bh_nowait(struct buffer_head *bh, blk_opf_t op_flags,
bh_end_io_t *end_io)
bh_end_io_t *end_io, bool simu_fail)
{
BUG_ON(!buffer_locked(bh));
@ -184,10 +190,11 @@ void ext4_read_bh_nowait(struct buffer_head *bh, blk_opf_t op_flags,
unlock_buffer(bh);
return;
}
__ext4_read_bh(bh, op_flags, end_io);
__ext4_read_bh(bh, op_flags, end_io, simu_fail);
}
int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags, bh_end_io_t *end_io)
int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags,
bh_end_io_t *end_io, bool simu_fail)
{
BUG_ON(!buffer_locked(bh));
@ -196,7 +203,7 @@ int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags, bh_end_io_t *end_io
return 0;
}
__ext4_read_bh(bh, op_flags, end_io);
__ext4_read_bh(bh, op_flags, end_io, simu_fail);
wait_on_buffer(bh);
if (buffer_uptodate(bh))
@ -208,10 +215,10 @@ int ext4_read_bh_lock(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
{
lock_buffer(bh);
if (!wait) {
ext4_read_bh_nowait(bh, op_flags, NULL);
ext4_read_bh_nowait(bh, op_flags, NULL, false);
return 0;
}
return ext4_read_bh(bh, op_flags, NULL);
return ext4_read_bh(bh, op_flags, NULL, false);
}
/*
@ -266,7 +273,7 @@ void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block)
if (likely(bh)) {
if (trylock_buffer(bh))
ext4_read_bh_nowait(bh, REQ_RAHEAD, NULL);
ext4_read_bh_nowait(bh, REQ_RAHEAD, NULL, false);
brelse(bh);
}
}