Re: [PATCH v3 08/33] nilfs2: don't set SB_RDONLY after filesystem errors

[sashiko-bot@kernel.org]

> With errors=remount-ro, the nilfs2 default, __nilfs_error() sets
> SB_RDONLY from whatever context hit the error and without holding
> s_umount. If that happens while the filesystem is frozen thaw_super()
> sees a read-only superblock and leaves the s_writers rwsems locked so
> every writer hangs.
> 
> nilfs2 already treats a runtime SB_RDONLY as "degraded because of
> corruption" in a lot of places and that can stay. So call
> sb_set_emergency_ro() instead and use sb_rdonly_any() for every
> sb_rdonly() check that guards a write. FITRIM is refused and a remount
> to read-only doesn't write anything anymore. The VFS doesn't call
> nilfs_sync_fs() in that state.
> 
> nilfs2 explicitly supported "mount -o remount,rw" after an error so far.
> Now the state lasts until umount like on ext4. That includes a mount
> that reconfigures a superblock only snapshots kept alive.
> nilfs_get_tree() does that without reconfigure_super() so
> nilfs_reconfigure() refuses going read-write itself. Writes through file
> descriptors opened before the error fail with EROFS now instead of being
> dropped.
> 
> Reported-by: Karl Mehltretter <kmehltretter@gmail.com>
> Link: https://lore.kernel.org/r/20260903060855.4610-1-kmehltretter@gmail.com
> Acked-by: Ryusuke Konishi <konishi.ryusuke@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/20261113-work-fs-sb_rdonly-v3-0-0be92bb73709@kernel.org?part=8