xfs: count the blocks in a btree

Provide a helper method to count the number of blocks in a short form
btree.  The refcount and rmap btrees need to know the number of blocks
already in use to set up their per-AG block reservations during mount.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

2 files changed, 25 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 50cfb98719dd..aa1752f918b8 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -4821,3 +4821,26 @@ xfs_btree_calc_size(
         }
         return rval;
 }
+
+int
+xfs_btree_count_blocks_helper(
+        struct xfs_btree_cur    *cur,
+        int                     level,
+        void                    *data)
+{
+        xfs_extlen_t            *blocks = data;
+        (*blocks)++;
+
+        return 0;
+}
+
+/* Count the blocks in a btree and return the result in *blocks. */
+int
+xfs_btree_count_blocks(
+        struct xfs_btree_cur    *cur,
+        xfs_extlen_t            *blocks)
+{
+        *blocks = 0;
+        return xfs_btree_visit_blocks(cur, xfs_btree_count_blocks_helper,
+                        blocks);
+}
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 1c148f5c5675..3f8556a5c2ad 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -519,4 +519,6 @@ typedef int (*xfs_btree_visit_blocks_fn)(struct xfs_btree_cur *cur, int level,
 int xfs_btree_visit_blocks(struct xfs_btree_cur *cur,
                 xfs_btree_visit_blocks_fn fn, void *data);
 
+int xfs_btree_count_blocks(struct xfs_btree_cur *cur, xfs_extlen_t *blocks);
+
 #endif  /* __XFS_BTREE_H__ */