Re: [PATCH RFC 27/28] xfs: allow remounting read-only after a shutdown

[sashiko-bot@kernel.org]

> A shut down xfs can't be remounted read-only. xfs_remount_ro() starts
> with sync_filesystem() and xfs_fs_sync_fs() fails with -EIO because the
> log can't be forced anymore. So "mount -o remount,ro" fails with EIO and
> the filesystem stays read-write. And emergency remount (sysrq u) asks
> every read-write superblock on a block device to go read-only with
> SB_FORCE. xfs refuses that too and reconfigure_super() warns before it
> sets SB_RDONLY anyway:
> 
>   sysrq: Emergency Remount R/O
>   forced remount of a xfs fs returned -5
>   WARNING: fs/super.c:1133 at reconfigure_super+0x498/0xb20, CPU#0: kworker/0:1/11
> 
> With panic_on_warn that's a panic from sysrq u. ext4 had the same
> problem in its emergency state.
> 
> [ ... ]
>   echo u > /proc/sysrq-trigger   # WARNING: forced remount of a xfs fs returned -5
> 
> Fixes: b97cca3ba909 ("xfs: only bother with sync_filesystem during readonly remount")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261012-work-fs-sb_rdonly-v1-0-60743a3dc326@kernel.org?part=27