xfs: add a xfs_btree_init_ptr_from_cur

Inode-rooted btrees don't need to initialize the root pointer in the
->init_ptr_from_cur method as the root is found by the
xfs_btree_get_iroot method later.  Make ->init_ptr_from_cur option
for inode rooted btrees by providing a helper that does the right
thing for the given btree type and also documents the semantics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 23 insertions, 4 deletions

diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index 5d0b1084cba8..7c4f842c5f91 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -1882,6 +1882,25 @@ xfs_lookup_get_search_key(
 }
 
 /*
+ * Initialize a pointer to the root block.
+ */
+void
+xfs_btree_init_ptr_from_cur(
+	struct xfs_btree_cur	*cur,
+	union xfs_btree_ptr	*ptr)
+{
+	if (cur->bc_ops->type == XFS_BTREE_TYPE_INODE) {
+		/*
+		 * Inode-rooted btrees call xfs_btree_get_iroot to find the root
+		 * in xfs_btree_lookup_get_block and don't need a pointer here.
+		 */
+		ptr->l = 0;
+	} else {
+		cur->bc_ops->init_ptr_from_cur(cur, ptr);
+	}
+}
+
+/*
  * Lookup the record.  The cursor is made to point to it, based on dir.
  * stat is set to 0 if can't find any such record, 1 for success.
  */
@@ -1911,7 +1930,7 @@ xfs_btree_lookup(
 	keyno = 0;
 
 	/* initialise start pointer from cursor */
-	cur->bc_ops->init_ptr_from_cur(cur, &ptr);
+	xfs_btree_init_ptr_from_cur(cur, &ptr);
 	pp = &ptr;
 
 	/*
@@ -3121,7 +3140,7 @@ xfs_btree_new_root(
 	XFS_BTREE_STATS_INC(cur, newroot);
 
 	/* initialise our start point from the cursor */
-	cur->bc_ops->init_ptr_from_cur(cur, &rptr);
+	xfs_btree_init_ptr_from_cur(cur, &rptr);
 
 	/* Allocate the new block. If we can't do it, we're toast. Give up. */
 	error = xfs_btree_alloc_block(cur, &rptr, &lptr, stat);
@@ -4430,7 +4449,7 @@ xfs_btree_visit_blocks(
 	struct xfs_btree_block		*block = NULL;
 	int				error = 0;
 
-	cur->bc_ops->init_ptr_from_cur(cur, &lptr);
+	xfs_btree_init_ptr_from_cur(cur, &lptr);
 
 	/* for each level */
 	for (level = cur->bc_nlevels - 1; level >= 0; level--) {
@@ -4852,7 +4871,7 @@ xfs_btree_overlapped_query_range(
 
 	/* Load the root of the btree. */
 	level = cur->bc_nlevels - 1;
-	cur->bc_ops->init_ptr_from_cur(cur, &ptr);
+	xfs_btree_init_ptr_from_cur(cur, &ptr);
 	error = xfs_btree_lookup_get_block(cur, level, &ptr, &block);
 	if (error)
 		return error;