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Message-ID: <20241008130216.GA661738@ceph-admin>
Date: Tue, 8 Oct 2024 21:02:16 +0800
From: Long Li <leo.lilong@...wei.com>
To: <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>
CC: <linux-ext4@...r.kernel.org>, <yi.zhang@...wei.com>,
<yangerkun@...wei.com>
Subject: Re: [PATCH] ext4: Fix race in buffer_head read fault injection
On Fri, Sep 06, 2024 at 05:17:46PM +0800, Long Li wrote:
Friendly Ping ...
> 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: 46f870d690fe ("ext4: simulate various I/O and checksum errors when reading metadata")
> Signed-off-by: Long Li <leo.lilong@...wei.com>
> ---
> fs/ext4/balloc.c | 4 ++--
> fs/ext4/ext4.h | 12 ++----------
> fs/ext4/extents.c | 2 +-
> fs/ext4/ialloc.c | 5 +++--
> fs/ext4/indirect.c | 2 +-
> fs/ext4/inode.c | 4 ++--
> fs/ext4/mmp.c | 2 +-
> fs/ext4/move_extent.c | 2 +-
> fs/ext4/resize.c | 2 +-
> fs/ext4/super.c | 23 +++++++++++++++--------
> 10 files changed, 29 insertions(+), 29 deletions(-)
>
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index 591fb3f710be..8042ad873808 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -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",
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 75a29b23d858..8083ff8e924c 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -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
> *
> @@ -3098,9 +3090,9 @@ 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);
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 34e25eee6521..88f98dc44027 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -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;
> }
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index 7f1a5f90dbbd..21d228073d79 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -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 - "
> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
> index 7404f0935c90..7de327fa7b1c 100644
> --- a/fs/ext4/indirect.c
> +++ b/fs/ext4/indirect.c
> @@ -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;
> }
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 54bdd4884fe6..99d09cd9c6a3 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4497,10 +4497,10 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
> * 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;
> diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
> index bd946d0c71b7..d64c04ed061a 100644
> --- a/fs/ext4/mmp.c
> +++ b/fs/ext4/mmp.c
> @@ -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;
>
> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
> index b64661ea6e0e..898443e98efc 100644
> --- a/fs/ext4/move_extent.c
> +++ b/fs/ext4/move_extent.c
> @@ -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);
>
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index e04eb08b9060..1d9d14b9d33d 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -1298,7 +1298,7 @@ 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;
> }
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index b77acba4a719..acce6644c1fc 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -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);
> }
> }
> --
> 2.39.2
>
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