1 files changed, 36 insertions, 2 deletions

diff --git a/fs/xfs/xfs_bmap_btree.c b/fs/xfs/xfs_bmap_btree.c
index bd18987326a3..93470b728dd0 100644
--- a/fs/xfs/xfs_bmap_btree.c
+++ b/fs/xfs/xfs_bmap_btree.c
@@ -2027,6 +2027,24 @@ xfs_bmbt_increment(
 
 /*
  * Insert the current record at the point referenced by cur.
+ *
+ * A multi-level split of the tree on insert will invalidate the original
+ * cursor. It appears, however, that some callers assume that the cursor is
+ * always valid. Hence if we do a multi-level split we need to revalidate the
+ * cursor.
+ *
+ * When a split occurs, we will see a new cursor returned. Use that as a
+ * trigger to determine if we need to revalidate the original cursor. If we get
+ * a split, then use the original irec to lookup up the path of the record we
+ * just inserted.
+ *
+ * Note that the fact that the btree root is in the inode means that we can
+ * have the level of the tree change without a "split" occurring at the root
+ * level. What happens is that the root is migrated to an allocated block and
+ * the inode root is pointed to it. This means a single split can change the
+ * level of the tree (level 2 -> level 3) and invalidate the old cursor. Hence
+ * the level change should be accounted as a split so as to correctly trigger a
+ * revalidation of the old cursor.
  */
 int                                     /* error */
 xfs_bmbt_insert(
@@ -2039,11 +2057,14 @@ xfs_bmbt_insert(
         xfs_fsblock_t   nbno;
         xfs_btree_cur_t *ncur;
         xfs_bmbt_rec_t  nrec;
+        xfs_bmbt_irec_t oirec;          /* original irec */
         xfs_btree_cur_t *pcur;
+        int             splits = 0;
 
         XFS_BMBT_TRACE_CURSOR(cur, ENTRY);
         level = 0;
         nbno = NULLFSBLOCK;
+        oirec = cur->bc_rec.b;
         xfs_bmbt_disk_set_all(&nrec, &cur->bc_rec.b);
         ncur = NULL;
         pcur = cur;
@@ -2052,11 +2073,13 @@ xfs_bmbt_insert(
                                 &i))) {
                         if (pcur != cur)
                                 xfs_btree_del_cursor(pcur, XFS_BTREE_ERROR);
-                        XFS_BMBT_TRACE_CURSOR(cur, ERROR);
-                        return error;
+                        goto error0;
                 }
                 XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                 if (pcur != cur && (ncur || nbno == NULLFSBLOCK)) {
+                        /* allocating a new root is effectively a split */
+                        if (cur->bc_nlevels != pcur->bc_nlevels)
+                                splits++;
                         cur->bc_nlevels = pcur->bc_nlevels;
                         cur->bc_private.b.allocated +=
                                 pcur->bc_private.b.allocated;
@@ -2070,10 +2093,21 @@ xfs_bmbt_insert(
                         xfs_btree_del_cursor(pcur, XFS_BTREE_NOERROR);
                 }
                 if (ncur) {
+                        splits++;
                         pcur = ncur;
                         ncur = NULL;
                 }
         } while (nbno != NULLFSBLOCK);
+
+        if (splits > 1) {
+                /* revalidate the old cursor as we had a multi-level split */
+                error = xfs_bmbt_lookup_eq(cur, oirec.br_startoff,
+                                oirec.br_startblock, oirec.br_blockcount, &i);
+                if (error)
+                        goto error0;
+                ASSERT(i == 1);
+        }
+
         XFS_BMBT_TRACE_CURSOR(cur, EXIT);
         *stat = i;
         return 0;