Re: [PATCH RFC 21/28] gfs2: don't set SB_RDONLY on withdraw

[sashiko-bot@kernel.org]

> do_withdraw() sets SB_RDONLY from the withdraw work item without holding
> sb->s_umount. gfs2_withdraw() sets SDF_WITHDRAWN right away and queues
> gfs2_withdraw_func() which runs do_withdraw(). That also happens on a
> frozen filesystem. SDF_JOURNAL_LIVE is still set then because the
> freeze log flush doesn't clear it.
> 
> freeze_super() and thaw_super() both look at sb_rdonly() to figure out
> whether the s_writers rwsems need to be taken or released. gfs2 doesn't
> even get that far. FITHAW goes through gfs2_thaw_super() to
> gfs2_do_thaw() whose gfs2_freeze_lock_shared() fails with -EIO for a
> withdrawn filesystem. So FITHAW never gets to thaw_super() and the
> filesystem stays frozen. The only ways out are emergency thaw, which
> calls thaw_super_locked() directly, and writing 0 to the gfs2 "freeze"
> sysfs file, which calls thaw_super() directly. Both see SB_RDONLY and
> skip sb_freeze_unlock(). The rwsems stay write-locked, writes through
> [ ... ]
> 
> Fixes: 601ef0d52e96 ("gfs2: Force withdraw to replay journals and wait for it to finish")
> Fixes: b77b4a4815a9 ("gfs2: Rework freeze / thaw logic")
> 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!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261012-work-fs-sb_rdonly-v1-0-60743a3dc326@kernel.org?part=21