xfs: move the zero records logic into xfs_bmap_broot_space_calc

The bmap btree cannot ever have zero records in an incore btree block.
If the number of records drops to zero, that means we're converting the
fork to extents format and are trying to remove the tree.  This logic
won't hold for the future realtime rmap btree, so move the logic into
the bmbt code.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

2 files changed, 9 insertions, 4 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap_btree.h b/fs/xfs/libxfs/xfs_bmap_btree.h
index 3e05e1b22967..76ac80f46783 100644
--- a/fs/xfs/libxfs/xfs_bmap_btree.h
+++ b/fs/xfs/libxfs/xfs_bmap_btree.h
@@ -157,6 +157,13 @@ xfs_bmap_broot_space_calc(
 	struct xfs_mount	*mp,
 	unsigned int		nrecs)
 {
+	/*
+	 * If the bmbt root block is empty, we should be converting the fork
+	 * to extents format.  Hence, the size is zero.
+	 */
+	if (nrecs == 0)
+		return 0;
+
 	return xfs_bmbt_block_len(mp) + \
 	       (nrecs * (sizeof(struct xfs_bmbt_key) + sizeof(xfs_bmbt_ptr_t)));
 }
diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index ebebf6b17e81..ef7a6b861c2d 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -483,10 +483,8 @@ xfs_iroot_realloc(
 	cur_max = xfs_bmbt_maxrecs(mp, old_size, 0);
 	new_max = cur_max + rec_diff;
 	ASSERT(new_max >= 0);
-	if (new_max > 0)
-		new_size = xfs_bmap_broot_space_calc(mp, new_max);
-	else
-		new_size = 0;
+
+	new_size = xfs_bmap_broot_space_calc(mp, new_max);
 	if (new_size == 0) {
 		xfs_iroot_free(ip, whichfork);
 		return;