Re: [PATCH v3 06/33] 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 and ext2_xattr_set()
> itself, ecryptfs calls the latter without write access on the lower
> mount. Unlinked inodes are left to e2fsck. ext2_write_inode() keeps
> working because writeback still writes data, bitmaps, indirect and
> directory blocks after the error and they'd be lost without the inode.
> A thaw after an error while frozen still writes the superblock but
> EXT2_ERROR_FS stays set in it.
> 
> After a remount to read-only a remount to read-write fails until umount.
> A plain remount to read-write right after the error succeeds but the
> filesystem stays read-only. 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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