6.17-stable review patch. If anyone has any objections, please let me know.
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From: Baokun Li libaokun1@huawei.com
commit d8b90e6387a74bcb1714c8d1e6a782ff709de9a9 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ext4/ext4.h | 2 ++ fs/ext4/indirect.c | 2 +- fs/ext4/super.c | 9 +++++++++ 3 files changed, 12 insertions(+), 1 deletion(-)
--- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -3144,6 +3144,8 @@ extern struct buffer_head *ext4_sb_bread 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, --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -1025,7 +1025,7 @@ static void ext4_free_branches(handle_t }
/* 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 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -265,6 +265,15 @@ struct buffer_head *ext4_sb_bread_unmova 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,