From 9113868544b1deb7acdd5374a0832886415389fa Mon Sep 17 00:00:00 2001 From: Long Li Date: Tue, 11 Mar 2025 08:51:19 +0900 Subject: [PATCH] ext4: fix race in buffer_head read fault injection BugLink: https://bugs.launchpad.net/bugs/2101915 [ Upstream commit 2f3d93e210b9c2866c8b3662adae427d5bf511ec ] 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() 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 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 Link: https://patch.msgid.link/20240906091746.510163-1-leo.lilong@huawei.com Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin Signed-off-by: Koichiro Den Signed-off-by: Stefan Bader --- 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 d07f5d69d0bd..7cbe70ca215e 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1862,14 +1862,6 @@ 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 * @@ -3086,9 +3078,9 @@ 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 3347b90dc7bc..c30c5d9ff8fd 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -564,7 +564,7 @@ __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 5a3b4bc12414..52f2959d29e6 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -194,8 +194,9 @@ 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 d8ca7f64f952..8480bddde789 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 6911fbd924b8..4d35111c9306 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4488,10 +4488,10 @@ 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; 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 42b52b6491a0..fd3487df360a 100644 --- a/fs/ext4/move_extent.c +++ b/fs/ext4/move_extent.c @@ -212,7 +212,7 @@ 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++; } /* No io required */ diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index 7df8d3742a3b..fd8eaf9435fb 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -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; } diff --git a/fs/ext4/super.c b/fs/ext4/super.c index ac445cca5adb..aee4ee849338 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); } }