[PATCH 1/2] Btrfs: remove unnecessary ref heads rb tree search

[PATCH 1/2] Btrfs: remove unnecessary ref heads rb tree search

[Filipe David Borba Manana]

When we didn't find the exact ref head we were looking for, if
return_bigger != 0 we set a new search key to match either the
next node after the last one we found or the first one in the
ref heads rb tree, and then did another full tree search. For both
cases this ended up being pointless as we would end up returning
an entry we already had before repeating the search.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
---
 fs/btrfs/delayed-ref.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index f3bff89..56cdfe9 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -205,7 +205,6 @@ find_ref_head(struct rb_root *root, u64 bytenr,
 	struct btrfs_delayed_ref_head *entry;
 	int cmp = 0;
 
-again:
 	n = root->rb_node;
 	entry = NULL;
 	while (n) {
@@ -234,9 +233,9 @@ again:
 				n = rb_first(root);
 			entry = rb_entry(n, struct btrfs_delayed_ref_head,
 					 href_node);
-			bytenr = entry->node.bytenr;
-			return_bigger = 0;
-			goto again;
+			if (last)
+				*last = entry;
+			return entry;
 		}
 		return entry;
 	}
-- 
1.7.9.5

[PATCH 2/2] Btrfs: cleanup delayed-ref.c:find_ref_head()

[Filipe David Borba Manana]

The argument last wasn't used, all callers supplied a NULL value
for it. Also removed unnecessary intermediate storage of the result
of key comparisons.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
---
 fs/btrfs/delayed-ref.c |   24 ++++++------------------
 1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index 56cdfe9..2502ba5 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -199,42 +199,30 @@ static struct btrfs_delayed_ref_head *htree_insert(struct rb_root *root,
  */
 static struct btrfs_delayed_ref_head *
 find_ref_head(struct rb_root *root, u64 bytenr,
-	      struct btrfs_delayed_ref_head **last, int return_bigger)
+	      int return_bigger)
 {
 	struct rb_node *n;
 	struct btrfs_delayed_ref_head *entry;
-	int cmp = 0;
 
 	n = root->rb_node;
 	entry = NULL;
 	while (n) {
 		entry = rb_entry(n, struct btrfs_delayed_ref_head, href_node);
-		if (last)
-			*last = entry;
 
 		if (bytenr < entry->node.bytenr)
-			cmp = -1;
-		else if (bytenr > entry->node.bytenr)
-			cmp = 1;
-		else
-			cmp = 0;
-
-		if (cmp < 0)
 			n = n->rb_left;
-		else if (cmp > 0)
+		else if (bytenr > entry->node.bytenr)
 			n = n->rb_right;
 		else
 			return entry;
 	}
 	if (entry && return_bigger) {
-		if (cmp > 0) {
+		if (bytenr > entry->node.bytenr) {
 			n = rb_next(&entry->href_node);
 			if (!n)
 				n = rb_first(root);
 			entry = rb_entry(n, struct btrfs_delayed_ref_head,
 					 href_node);
-			if (last)
-				*last = entry;
 			return entry;
 		}
 		return entry;
@@ -414,12 +402,12 @@ btrfs_select_ref_head(struct btrfs_trans_handle *trans)
 
 again:
 	start = delayed_refs->run_delayed_start;
-	head = find_ref_head(&delayed_refs->href_root, start, NULL, 1);
+	head = find_ref_head(&delayed_refs->href_root, start, 1);
 	if (!head && !loop) {
 		delayed_refs->run_delayed_start = 0;
 		start = 0;
 		loop = true;
-		head = find_ref_head(&delayed_refs->href_root, start, NULL, 1);
+		head = find_ref_head(&delayed_refs->href_root, start, 1);
 		if (!head)
 			return NULL;
 	} else if (!head && loop) {
@@ -897,7 +885,7 @@ btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
 	struct btrfs_delayed_ref_root *delayed_refs;
 
 	delayed_refs = &trans->transaction->delayed_refs;
-	return find_ref_head(&delayed_refs->href_root, bytenr, NULL, 0);
+	return find_ref_head(&delayed_refs->href_root, bytenr, 0);
 }
 
 void btrfs_delayed_ref_exit(void)
-- 
1.7.9.5