xfs: create individual inode alloc. helper

Inode allocation from sparse inode records must filter the ir_free mask
against ir_holemask.  In preparation for this requirement, create a
helper to allocate an individual inode from an inode record.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 07349a1..a186831 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -732,6 +732,16 @@
 }
 
 /*
+ * Return the offset of the first free inode in the record.
+ */
+STATIC int
+xfs_inobt_first_free_inode(
+	struct xfs_inobt_rec_incore	*rec)
+{
+	return xfs_lowbit64(rec->ir_free);
+}
+
+/*
  * Allocate an inode using the inobt-only algorithm.
  */
 STATIC int
@@ -961,7 +971,7 @@
 	}
 
 alloc_inode:
-	offset = xfs_lowbit64(rec.ir_free);
+	offset = xfs_inobt_first_free_inode(&rec);
 	ASSERT(offset >= 0);
 	ASSERT(offset < XFS_INODES_PER_CHUNK);
 	ASSERT((XFS_AGINO_TO_OFFSET(mp, rec.ir_startino) %
@@ -1210,7 +1220,7 @@
 	if (error)
 		goto error_cur;
 
-	offset = xfs_lowbit64(rec.ir_free);
+	offset = xfs_inobt_first_free_inode(&rec);
 	ASSERT(offset >= 0);
 	ASSERT(offset < XFS_INODES_PER_CHUNK);
 	ASSERT((XFS_AGINO_TO_OFFSET(mp, rec.ir_startino) %