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| author | Baokun Li <libaokun1@huawei.com> | 2025-08-21 21:38:57 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2025-09-25 14:36:54 -0400 |
| commit | d8b90e6387a74bcb1714c8d1e6a782ff709de9a9 (patch) | |
| tree | 41d1845306f7700362ef282638e46dacad8ec717 /fs | |
| parent | ext4: replace min/max nesting with clamp() (diff) | |
| download | linux-d8b90e6387a74bcb1714c8d1e6a782ff709de9a9.tar.gz linux-d8b90e6387a74bcb1714c8d1e6a782ff709de9a9.zip | |
ext4: add ext4_sb_bread_nofail() helper function for ext4_free_branches()
The implicit __GFP_NOFAIL flag in ext4_sb_bread() was removed in commit
8a83ac54940d ("ext4: call bdev_getblk() from sb_getblk_gfp()"), meaning
the function can now fail under memory pressure.
Most callers of ext4_sb_bread() propagate the error to userspace and do not
remount the filesystem read-only. However, ext4_free_branches() handles
ext4_sb_bread() failure by remounting the filesystem read-only.
This implies that an ext3 filesystem (mounted via the ext4 driver) could be
forcibly remounted read-only due to a transient page allocation failure,
which is unacceptable.
To mitigate this, introduce a new helper function, ext4_sb_bread_nofail(),
which explicitly uses __GFP_NOFAIL, and use it in ext4_free_branches().
Fixes: 8a83ac54940d ("ext4: call bdev_getblk() from sb_getblk_gfp()")
Cc: stable@kernel.org
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/ext4/ext4.h | 2 | ||||
| -rw-r--r-- | fs/ext4/indirect.c | 2 | ||||
| -rw-r--r-- | fs/ext4/super.c | 9 |
3 files changed, 12 insertions, 1 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 01a6e2de7fc3..95b99a916ed8 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -3134,6 +3134,8 @@ extern struct buffer_head *ext4_sb_bread(struct super_block *sb, sector_t block, blk_opf_t op_flags); extern struct buffer_head *ext4_sb_bread_unmovable(struct super_block *sb, sector_t block); +extern struct buffer_head *ext4_sb_bread_nofail(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, bool simu_fail); extern int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags, diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index d45124318200..da76353b3a57 100644 --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -1025,7 +1025,7 @@ static void ext4_free_branches(handle_t *handle, struct inode *inode, } /* Go read the buffer for the next level down */ - bh = ext4_sb_bread(inode->i_sb, nr, 0); + bh = ext4_sb_bread_nofail(inode->i_sb, nr); /* * A read failure? Report error and clear slot diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 699c15db28a8..d26e5c0731e5 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -265,6 +265,15 @@ struct buffer_head *ext4_sb_bread_unmovable(struct super_block *sb, return __ext4_sb_bread_gfp(sb, block, 0, gfp); } +struct buffer_head *ext4_sb_bread_nofail(struct super_block *sb, + sector_t block) +{ + gfp_t gfp = mapping_gfp_constraint(sb->s_bdev->bd_mapping, + ~__GFP_FS) | __GFP_MOVABLE | __GFP_NOFAIL; + + return __ext4_sb_bread_gfp(sb, block, 0, gfp); +} + void ext4_sb_breadahead_unmovable(struct super_block *sb, sector_t block) { struct buffer_head *bh = bdev_getblk(sb->s_bdev, block, |