linux-kernel - [PATCH v2] lib/btree.c: optimise the code by previously getpos function

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Message-Id: <1494495741-30760-1-git-send-email-lenohou@gmail.com>
Date:   Thu, 11 May 2017 17:42:21 +0800
From:   Leno Hou <lenohou@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     andy.shevchenko@...il.com, hch@...radead.org,
        Leno Hou <lenohou@...il.com>
Subject: [PATCH v2] lib/btree.c: optimise the code by previously getpos function

This patch optimized the code by previously getpos function call.
Therefore, It's takes the convenience to understand logic of code.

v2:
  - getpos() returns errorno if not found the key

v1:
  - cleanup code by using getpos()

Signed-off-by: Leno Hou <lenohou@...il.com>
---
 lib/btree.c | 50 +++++++++++++++++++++-----------------------------
 1 file changed, 21 insertions(+), 29 deletions(-)

diff --git a/lib/btree.c b/lib/btree.c
index f93a945..8604773 100644
--- a/lib/btree.c
+++ b/lib/btree.c
@@ -238,6 +238,18 @@ static int keyzero(struct btree_geo *geo, unsigned long *key)
 	return 1;
 }
 
+static int getpos(struct btree_geo *geo, unsigned long *node,
+		unsigned long *key)
+{
+	unsigned int i;
+
+	for (i = 0; i < geo->no_pairs; i++) {
+		if (keycmp(geo, node, i, key) <= 0)
+			return i;
+	}
+	return -ENOENT;
+}
+
 void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
 		unsigned long *key)
 {
@@ -248,10 +260,8 @@ void *btree_lookup(struct btree_head *head, struct btree_geo *geo,
 		return NULL;
 
 	for ( ; height > 1; height--) {
-		for (i = 0; i < geo->no_pairs; i++)
-			if (keycmp(geo, node, i, key) <= 0)
-				break;
-		if (i == geo->no_pairs)
+		i = getpos(geo, node, key);
+		if (i < 0)
 			return NULL;
 		node = bval(geo, node, i);
 		if (!node)
@@ -278,10 +288,8 @@ int btree_update(struct btree_head *head, struct btree_geo *geo,
 		return -ENOENT;
 
 	for ( ; height > 1; height--) {
-		for (i = 0; i < geo->no_pairs; i++)
-			if (keycmp(geo, node, i, key) <= 0)
-				break;
-		if (i == geo->no_pairs)
+		i = getpos(geo, node, key);
+		if (i < 0)
 			return -ENOENT;
 		node = bval(geo, node, i);
 		if (!node)
@@ -326,10 +334,8 @@ void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
 
 	node = head->node;
 	for (height = head->height ; height > 1; height--) {
-		for (i = 0; i < geo->no_pairs; i++)
-			if (keycmp(geo, node, i, key) <= 0)
-				break;
-		if (i == geo->no_pairs)
+		i = getpos(geo, node, key);
+		if (i < 0)
 			goto miss;
 		oldnode = node;
 		node = bval(geo, node, i);
@@ -360,18 +366,6 @@ void *btree_get_prev(struct btree_head *head, struct btree_geo *geo,
 }
 EXPORT_SYMBOL_GPL(btree_get_prev);
 
-static int getpos(struct btree_geo *geo, unsigned long *node,
-		unsigned long *key)
-{
-	int i;
-
-	for (i = 0; i < geo->no_pairs; i++) {
-		if (keycmp(geo, node, i, key) <= 0)
-			break;
-	}
-	return i;
-}
-
 static int getfill(struct btree_geo *geo, unsigned long *node, int start)
 {
 	int i;
@@ -392,11 +386,9 @@ static unsigned long *find_level(struct btree_head *head, struct btree_geo *geo,
 	int i, height;
 
 	for (height = head->height; height > level; height--) {
-		for (i = 0; i < geo->no_pairs; i++)
-			if (keycmp(geo, node, i, key) <= 0)
-				break;
+		i = getpos(geo, node, key);
 
-		if ((i == geo->no_pairs) || !bval(geo, node, i)) {
+		if ((i < 0) || !bval(geo, node, i)) {
 			/* right-most key is too large, update it */
 			/* FIXME: If the right-most key on higher levels is
 			 * always zero, this wouldn't be necessary. */
@@ -466,7 +458,7 @@ static int btree_insert_level(struct btree_head *head, struct btree_geo *geo,
 	/* two identical keys are not allowed */
 	BUG_ON(pos < fill && keycmp(geo, node, pos, key) == 0);
 
-	if (fill == geo->no_pairs) {
+	if (fill < 0) {
 		/* need to split node */
 		unsigned long *new;
 
-- 
2.7.4