gfs2: Don't call cancel_delayed_work_sync from within delete work function

commit 6bd1c7b upstream.

Right now, we can end up calling cancel_delayed_work_sync from within
delete_work_func via gfs2_lookup_by_inum -> gfs2_inode_lookup ->
gfs2_cancel_delete_work.  When that happens, it will result in a
deadlock.  Instead, gfs2_inode_lookup should skip the call to
gfs2_cancel_delete_work when called from delete_work_func (blktype ==
GFS2_BLKST_UNLINKED).

Reported-by: Alexander Ahring Oder Aring <aahringo@redhat.com>
Fixes: a0e3cc6 ("gfs2: Turn gl_delete into a delayed work")
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Andreas Gruenbacher

fs/gfs2/inode.c

@@ -180,7 +180,8 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 		error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT, &ip->i_iopen_gh);
 		if (unlikely(error))
 			goto fail;
-		gfs2_cancel_delete_work(ip->i_iopen_gh.gh_gl);
+		if (blktype != GFS2_BLKST_UNLINKED)
+			gfs2_cancel_delete_work(ip->i_iopen_gh.gh_gl);
 		glock_set_object(ip->i_iopen_gh.gh_gl, ip);
 		gfs2_glock_put(io_gl);
 		io_gl = NULL;