linux-kernel - [PATCH AUTOSEL 5.10 02/22] gfs2: Flag a withdraw if init

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Date:   Mon,  5 Apr 2021 12:04:11 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Andrew Price <anprice@...hat.com>,
        Alexander Aring <aahringo@...hat.com>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Sasha Levin <sashal@...nel.org>, cluster-devel@...hat.com
Subject: [PATCH AUTOSEL 5.10 02/22] gfs2: Flag a withdraw if init_threads() fails

From: Andrew Price <anprice@...hat.com>

[ Upstream commit 62dd0f98a0e5668424270b47a0c2e973795faba7 ]

Interrupting mount with ^C quickly enough can cause the kthread_run()
calls in gfs2's init_threads() to fail and the error path leads to a
deadlock on the s_umount rwsem. The abridged chain of events is:

  [mount path]
  get_tree_bdev()
    sget_fc()
      alloc_super()
        down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING); [acquired]
    gfs2_fill_super()
      gfs2_make_fs_rw()
        init_threads()
          kthread_run()
            ( Interrupted )
      [Error path]
      gfs2_gl_hash_clear()
        flush_workqueue(glock_workqueue)
          wait_for_completion()

  [workqueue context]
  glock_work_func()
    run_queue()
      do_xmote()
        freeze_go_sync()
          freeze_super()
            down_write(&sb->s_umount) [deadlock]

In freeze_go_sync() there is a gfs2_withdrawn() check that we can use to
make sure freeze_super() is not called in the error path, so add a
gfs2_withdraw_delayed() call when init_threads() fails.

Ref: https://bugzilla.kernel.org/show_bug.cgi?id=212231

Reported-by: Alexander Aring <aahringo@...hat.com>
Signed-off-by: Andrew Price <anprice@...hat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/gfs2/super.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index ddd40c96f7a2..0581612dd91e 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -169,8 +169,10 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
 	int error;
 
 	error = init_threads(sdp);
-	if (error)
+	if (error) {
+		gfs2_withdraw_delayed(sdp);
 		return error;
+	}
 
 	j_gl->gl_ops->go_inval(j_gl, DIO_METADATA);
 	if (gfs2_withdrawn(sdp)) {
-- 
2.30.2