linux-kernel - [PATCH 5/5] sbitmap: add sbitmap_find_bit to remove repeat code in __sbitmap_get/__sbitmap_get

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20221201045408.21908-6-shikemeng@huawei.com>
Date:   Thu, 1 Dec 2022 12:54:08 +0800
From:   Kemeng Shi <shikemeng@...wei.com>
To:     <axboe@...nel.dk>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <shikemeng@...weicloud.com>, <linfeilong@...wei.com>,
        <liuzhiqiang@...wei.com>
Subject: [PATCH 5/5] sbitmap: add sbitmap_find_bit to remove repeat code in __sbitmap_get/__sbitmap_get_shallow

There are three differences between __sbitmap_get and
__sbitmap_get_shallow when searching free bit:
1. __sbitmap_get_shallow limit number of bit to search per word.
__sbitmap_get has no such limit.
2. __sbitmap_get_shallow always searches with wrap set. __sbitmap_get set
wrap according to round_robin.
3. __sbitmap_get_shallow always searches from first bit in first word.
__sbitmap_get searches from first bit when round_robin is not set
otherwise searches from SB_NR_TO_BIT(sb, alloc_hint).

Add helper function sbitmap_find_bit function to do common search while
accept "limit depth per word", "wrap flag" and "first bit to
search" from caller to support the need of both __sbitmap_get and
__sbitmap_get_shallow.

Signed-off-by: Kemeng Shi <shikemeng@...wei.com>
---
 lib/sbitmap.c | 72 +++++++++++++++++++++++++--------------------------
 1 file changed, 35 insertions(+), 37 deletions(-)

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index b6a2cdb9bdaf..93e7db484b96 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -186,26 +186,22 @@ static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
 	return nr;
 }
 
-static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
+static int sbitmap_find_bit(struct sbitmap *sb,
+			    unsigned int depth,
+			    unsigned int index,
+			    unsigned int alloc_hint,
+			    bool wrap)
 {
-	unsigned int i, index;
+	unsigned int i;
 	int nr = -1;
 
-	index = SB_NR_TO_INDEX(sb, alloc_hint);
-
-	/*
-	 * Unless we're doing round robin tag allocation, just use the
-	 * alloc_hint to find the right word index. No point in looping
-	 * twice in find_next_zero_bit() for that case.
-	 */
-	if (sb->round_robin)
-		alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
-	else
-		alloc_hint = 0;
-
 	for (i = 0; i < sb->map_nr; i++) {
-		nr = sbitmap_find_bit_in_word(&sb->map[index], __map_depth(sb, index),
-					      alloc_hint, !sb->round_robin);
+		nr = sbitmap_find_bit_in_word(&sb->map[index],
+					      min_t(unsigned int,
+						    __map_depth(sb, index),
+						    depth),
+					      alloc_hint, wrap);
+
 		if (nr != -1) {
 			nr += index << sb->shift;
 			break;
@@ -215,11 +211,32 @@ static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
 		alloc_hint = 0;
 		if (++index >= sb->map_nr)
 			index = 0;
+
 	}
 
 	return nr;
 }
 
+static int __sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint)
+{
+	unsigned int index;
+
+	index = SB_NR_TO_INDEX(sb, alloc_hint);
+
+	/*
+	 * Unless we're doing round robin tag allocation, just use the
+	 * alloc_hint to find the right word index. No point in looping
+	 * twice in find_next_zero_bit() for that case.
+	 */
+	if (sb->round_robin)
+		alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
+	else
+		alloc_hint = 0;
+
+	return sbitmap_find_bit(sb, UINT_MAX, index, alloc_hint,
+				!sb->round_robin);
+}
+
 int sbitmap_get(struct sbitmap *sb)
 {
 	int nr;
@@ -241,31 +258,12 @@ static int __sbitmap_get_shallow(struct sbitmap *sb,
 				 unsigned int alloc_hint,
 				 unsigned long shallow_depth)
 {
-	unsigned int i, index;
-	int nr = -1;
+	unsigned int index;
 
 	index = SB_NR_TO_INDEX(sb, alloc_hint);
 	alloc_hint = SB_NR_TO_BIT(sb, alloc_hint);
 
-	for (i = 0; i < sb->map_nr; i++) {
-		nr = sbitmap_find_bit_in_word(&sb->map[index],
-					      min_t(unsigned int,
-						    __map_depth(sb, index),
-						    shallow_depth),
-					      alloc_hint, true);
-
-		if (nr != -1) {
-			nr += index << sb->shift;
-			break;
-		}
-
-		/* Jump to next index. */
-		alloc_hint = 0;
-		if (++index >= sb->map_nr)
-			index = 0;
-	}
-
-	return nr;
+	return sbitmap_find_bit(sb, shallow_depth, index, alloc_hint, true);
 }
 
 int sbitmap_get_shallow(struct sbitmap *sb, unsigned long shallow_depth)
-- 
2.30.0