Re: [PATCH v2 04/34] ext2: don't set SB_RDONLY after filesystem errors

[sashiko-bot@kernel.org]

> With errors=remount-ro ext2_error() sets SB_RDONLY from whatever context
> hit the error and without holding s_umount. That races with everyone
> else changing sb->s_flags and it breaks freezing. If it happens while
> the filesystem is frozen thaw_super() sees a read-only superblock and
> leaves the s_writers rwsems locked so every writer hangs. A lookup in a
> corrupted directory is enough. Karl proposed teaching thaw_super() about
> it but Jan preferred fixing the filesystems (cf. [1]) like ext4 and f2fs
> already did.
> 
> So call sb_set_emergency_ro() instead and let the VFS refuse
> modifications. ext2 still refuses allocations, ext2_write_inode(),
> ext2_sync_fs() and ext2_xattr_set() itself. The superblock isn't written
> after the error is recorded and unlinked inodes are left to e2fsck.
> ext2_handle_dirsync() treats EROFS as success in that state because the
> entry was already changed.
> 
> A remount to read-write fails until umount and writes through file
> descriptors opened before the error fail with EROFS.
> 
> [1]: https://lore.kernel.org/r/hyhuckyohsabx2suvq3z7uy3pbgmihva6wgzxr3op7pzcrlu33@p7zzlgp2ehjf
> 
> Reported-by: Karl Mehltretter <kmehltretter@gmail.com>
> Link: https://lore.kernel.org/r/20260903060855.4610-1-kmehltretter@gmail.com
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261029-work-fs-sb_rdonly-v2-0-2f44f64f0b66@kernel.org?part=4