xfs: remove the ->kill_root btree operation

The implementation os ->kill_root only differ by either simply
zeroing out the now unused buffer in the btree cursor in the inode
allocation btree or using xfs_btree_setbuf in the allocation btree.

Initially both of them used xfs_btree_setbuf, but the use in the
ialloc btree was removed early on because it interacted badly with
xfs_trans_binval.

In addition to zeroing out the buffer in the cursor xfs_btree_setbuf
updates the bc_ra array in the btree cursor, and calls
xfs_trans_brelse on the buffer previous occupying the slot.

The bc_ra update should be done for the alloc btree updated too,
although the lack of it does not cause serious problems.  The
xfs_trans_brelse call on the other hand is effectively a no-op in
the end - it keeps decrementing the bli_recur refcount until it hits
zero, and then just skips out because the buffer will always be
dirty at this point.  So removing it for the allocation btree is
just fine.

So unify the code and move it to xfs_btree.c.  While we're at it
also replace the call to xfs_btree_setbuf with a NULL bp argument in
xfs_btree_del_cursor with a direct call to xfs_trans_brelse given
that the cursor is beeing freed just after this and the state
updates are superflous.  After this xfs_btree_setbuf is only used
with a non-NULL bp argument and can thus be simplified.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_alloc_btree.c

@@ -280,38 +280,6 @@ xfs_allocbt_key_diff(
 	return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
 }
 
-STATIC int
-xfs_allocbt_kill_root(
-	struct xfs_btree_cur	*cur,
-	struct xfs_buf		*bp,
-	int			level,
-	union xfs_btree_ptr	*newroot)
-{
-	int			error;
-
-	XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
-	XFS_BTREE_STATS_INC(cur, killroot);
-
-	/*
-	 * Update the root pointer, decreasing the level by 1 and then
-	 * free the old root.
-	 */
-	xfs_allocbt_set_root(cur, newroot, -1);
-	error = xfs_allocbt_free_block(cur, bp);
-	if (error) {
-		XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
-		return error;
-	}
-
-	XFS_BTREE_STATS_INC(cur, free);
-
-	xfs_btree_setbuf(cur, level, NULL);
-	cur->bc_nlevels--;
-
-	XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
-	return 0;
-}
-
 #ifdef DEBUG
 STATIC int
 xfs_allocbt_keys_inorder(
@@ -423,7 +391,6 @@ static const struct xfs_btree_ops xfs_allocbt_ops = {
 
 	.dup_cursor		= xfs_allocbt_dup_cursor,
 	.set_root		= xfs_allocbt_set_root,
-	.kill_root		= xfs_allocbt_kill_root,
 	.alloc_block		= xfs_allocbt_alloc_block,
 	.free_block		= xfs_allocbt_free_block,
 	.update_lastrec		= xfs_allocbt_update_lastrec,

fs/xfs/xfs_btree.c

@@ -217,7 +217,7 @@ xfs_btree_del_cursor(
 	 */
 	for (i = 0; i < cur->bc_nlevels; i++) {
 		if (cur->bc_bufs[i])
-			xfs_btree_setbuf(cur, i, NULL);
+			xfs_trans_brelse(cur->bc_tp, cur->bc_bufs[i]);
 		else if (!error)
 			break;
 	}
@@ -763,22 +763,19 @@ xfs_btree_readahead(
  * Set the buffer for level "lev" in the cursor to bp, releasing
  * any previous buffer.
  */
-void
+STATIC void
 xfs_btree_setbuf(
 	xfs_btree_cur_t		*cur,	/* btree cursor */
 	int			lev,	/* level in btree */
 	xfs_buf_t		*bp)	/* new buffer to set */
 {
 	struct xfs_btree_block	*b;	/* btree block */
-	xfs_buf_t		*obp;	/* old buffer pointer */
 
-	obp = cur->bc_bufs[lev];
-	if (obp)
-		xfs_trans_brelse(cur->bc_tp, obp);
+	if (cur->bc_bufs[lev])
+		xfs_trans_brelse(cur->bc_tp, cur->bc_bufs[lev]);
 	cur->bc_bufs[lev] = bp;
 	cur->bc_ra[lev] = 0;
-	if (!bp)
-		return;
+
 	b = XFS_BUF_TO_BLOCK(bp);
 	if (cur->bc_flags & XFS_BTREE_LONG_PTRS) {
 		if (be64_to_cpu(b->bb_u.l.bb_leftsib) == NULLDFSBNO)
@@ -3011,6 +3008,43 @@ xfs_btree_kill_iroot(
 	return 0;
 }
 
+/*
+ * Kill the current root node, and replace it with it's only child node.
+ */
+STATIC int
+xfs_btree_kill_root(
+	struct xfs_btree_cur	*cur,
+	struct xfs_buf		*bp,
+	int			level,
+	union xfs_btree_ptr	*newroot)
+{
+	int			error;
+
+	XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
+	XFS_BTREE_STATS_INC(cur, killroot);
+
+	/*
+	 * Update the root pointer, decreasing the level by 1 and then
+	 * free the old root.
+	 */
+	cur->bc_ops->set_root(cur, newroot, -1);
+
+	error = cur->bc_ops->free_block(cur, bp);
+	if (error) {
+		XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
+		return error;
+	}
+
+	XFS_BTREE_STATS_INC(cur, free);
+
+	cur->bc_bufs[level] = NULL;
+	cur->bc_ra[level] = 0;
+	cur->bc_nlevels--;
+
+	XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
+	return 0;
+}
+
 STATIC int
 xfs_btree_dec_cursor(
 	struct xfs_btree_cur	*cur,
@@ -3195,7 +3229,7 @@ xfs_btree_delrec(
 			 * Make it the new root of the btree.
 			 */
 			pp = xfs_btree_ptr_addr(cur, 1, block);
-			error = cur->bc_ops->kill_root(cur, bp, level, pp);
+			error = xfs_btree_kill_root(cur, bp, level, pp);
 			if (error)
 				goto error0;
 		} else if (level > 0) {

fs/xfs/xfs_btree.h

@@ -152,9 +152,7 @@ struct xfs_btree_ops {
 
 	/* update btree root pointer */
 	void	(*set_root)(struct xfs_btree_cur *cur,
-				union xfs_btree_ptr *nptr, int level_change);
-	int	(*kill_root)(struct xfs_btree_cur *cur, struct xfs_buf *bp,
-				int level, union xfs_btree_ptr *newroot);
+			    union xfs_btree_ptr *nptr, int level_change);
 
 	/* block allocation / freeing */
 	int	(*alloc_block)(struct xfs_btree_cur *cur,
@@ -399,16 +397,6 @@ xfs_btree_reada_bufs(
 	xfs_agblock_t		agbno,	/* allocation group block number */
 	xfs_extlen_t		count);	/* count of filesystem blocks */
 
-/*
- * Set the buffer for level "lev" in the cursor to bp, releasing
- * any previous buffer.
- */
-void
-xfs_btree_setbuf(
-	xfs_btree_cur_t		*cur,	/* btree cursor */
-	int			lev,	/* level in btree */
-	struct xfs_buf		*bp);	/* new buffer to set */
-
 
 /*
  * Common btree core entry points.

fs/xfs/xfs_ialloc_btree.c

@@ -183,38 +183,6 @@ xfs_inobt_key_diff(
 			  cur->bc_rec.i.ir_startino;
 }
 
-STATIC int
-xfs_inobt_kill_root(
-	struct xfs_btree_cur	*cur,
-	struct xfs_buf		*bp,
-	int			level,
-	union xfs_btree_ptr	*newroot)
-{
-	int			error;
-
-	XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
-	XFS_BTREE_STATS_INC(cur, killroot);
-
-	/*
-	 * Update the root pointer, decreasing the level by 1 and then
-	 * free the old root.
-	 */
-	xfs_inobt_set_root(cur, newroot, -1);
-	error = xfs_inobt_free_block(cur, bp);
-	if (error) {
-		XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
-		return error;
-	}
-
-	XFS_BTREE_STATS_INC(cur, free);
-
-	cur->bc_bufs[level] = NULL;
-	cur->bc_nlevels--;
-
-	XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
-	return 0;
-}
-
 #ifdef DEBUG
 STATIC int
 xfs_inobt_keys_inorder(
@@ -309,7 +277,6 @@ static const struct xfs_btree_ops xfs_inobt_ops = {
 
 	.dup_cursor		= xfs_inobt_dup_cursor,
 	.set_root		= xfs_inobt_set_root,
-	.kill_root		= xfs_inobt_kill_root,
 	.alloc_block		= xfs_inobt_alloc_block,
 	.free_block		= xfs_inobt_free_block,
 	.get_minrecs		= xfs_inobt_get_minrecs,