ceph: switch to use cap_delay_lock for the unlink delay list

The same list item will be used in both cap_delay_list and
cap_unlink_delay_list, so it's buggy to use two different locks
to protect them.

Cc: stable@vger.kernel.org
Fixes: dbc347ef ("ceph: add ceph_cap_unlink_work to fire check_caps() immediately")
Link: https://lists.ceph.io/hyperkitty/list/ceph-users@ceph.io/thread/AODC76VXRAMXKLFDCTK4TKFDDPWUSCN5Reported-by: Marc Ruhmann <ruhmann@luis.uni-hannover.de>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Marc Ruhmann <ruhmann@luis.uni-hannover.de>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/caps.c

@@ -4783,13 +4783,13 @@ int ceph_drop_caps_for_unlink(struct inode *inode)
 
 			doutc(mdsc->fsc->client, "%p %llx.%llx\n", inode,
 			      ceph_vinop(inode));
-			spin_lock(&mdsc->cap_unlink_delay_lock);
+			spin_lock(&mdsc->cap_delay_lock);
 			ci->i_ceph_flags |= CEPH_I_FLUSH;
 			if (!list_empty(&ci->i_cap_delay_list))
 				list_del_init(&ci->i_cap_delay_list);
 			list_add_tail(&ci->i_cap_delay_list,
 				      &mdsc->cap_unlink_delay_list);
-			spin_unlock(&mdsc->cap_unlink_delay_lock);
+			spin_unlock(&mdsc->cap_delay_lock);
 
 			/*
 			 * Fire the work immediately, because the MDS maybe

fs/ceph/mds_client.c

@@ -2504,7 +2504,7 @@ static void ceph_cap_unlink_work(struct work_struct *work)
 	struct ceph_client *cl = mdsc->fsc->client;
 
 	doutc(cl, "begin\n");
-	spin_lock(&mdsc->cap_unlink_delay_lock);
+	spin_lock(&mdsc->cap_delay_lock);
 	while (!list_empty(&mdsc->cap_unlink_delay_list)) {
 		struct ceph_inode_info *ci;
 		struct inode *inode;
@@ -2516,15 +2516,15 @@ static void ceph_cap_unlink_work(struct work_struct *work)
 
 		inode = igrab(&ci->netfs.inode);
 		if (inode) {
-			spin_unlock(&mdsc->cap_unlink_delay_lock);
+			spin_unlock(&mdsc->cap_delay_lock);
 			doutc(cl, "on %p %llx.%llx\n", inode,
 			      ceph_vinop(inode));
 			ceph_check_caps(ci, CHECK_CAPS_FLUSH);
 			iput(inode);
-			spin_lock(&mdsc->cap_unlink_delay_lock);
+			spin_lock(&mdsc->cap_delay_lock);
 		}
 	}
-	spin_unlock(&mdsc->cap_unlink_delay_lock);
+	spin_unlock(&mdsc->cap_delay_lock);
 	doutc(cl, "done\n");
 }
 
@@ -5404,7 +5404,6 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
 	INIT_LIST_HEAD(&mdsc->cap_wait_list);
 	spin_lock_init(&mdsc->cap_delay_lock);
 	INIT_LIST_HEAD(&mdsc->cap_unlink_delay_list);
-	spin_lock_init(&mdsc->cap_unlink_delay_lock);
 	INIT_LIST_HEAD(&mdsc->snap_flush_list);
 	spin_lock_init(&mdsc->snap_flush_lock);
 	mdsc->last_cap_flush_tid = 1;

fs/ceph/mds_client.h

@@ -461,9 +461,8 @@ struct ceph_mds_client {
 	struct delayed_work    delayed_work;  /* delayed work */
 	unsigned long    last_renew_caps;  /* last time we renewed our caps */
 	struct list_head cap_delay_list;   /* caps with delayed release */
-	spinlock_t       cap_delay_lock;   /* protects cap_delay_list */
 	struct list_head cap_unlink_delay_list;  /* caps with delayed release for unlink */
-	spinlock_t       cap_unlink_delay_lock;  /* protects cap_unlink_delay_list */
+	spinlock_t       cap_delay_lock;   /* protects cap_delay_list and cap_unlink_delay_list */
 	struct list_head snap_flush_list;  /* cap_snaps ready to flush */
 	spinlock_t       snap_flush_lock;