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  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Fri, 12 May 2017 11:30:04 +0900
From:   js1304@...il.com
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, kernel-team@....com,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: [PATCH v5 4/4] zram: compare all the entries with same checksum for deduplication

From: Joonsoo Kim <iamjoonsoo.kim@....com>

Until now, we compare just one entry with same checksum when
checking duplication since it is the simplest way to implement.
However, for the completeness, checking all the entries is better
so this patch implement to compare all the entries with same checksum.
Since this event would be rare so there would be no performance loss.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Acked-by: Minchan Kim <minchan@...nel.org>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
---
 drivers/block/zram/zram_dedup.c | 59 ++++++++++++++++++++++++++++++++---------
 1 file changed, 47 insertions(+), 12 deletions(-)

diff --git a/drivers/block/zram/zram_dedup.c b/drivers/block/zram/zram_dedup.c
index 560b1f5..14c4988 100644
--- a/drivers/block/zram/zram_dedup.c
+++ b/drivers/block/zram/zram_dedup.c
@@ -109,6 +109,51 @@ static unsigned long zram_dedup_put(struct zram *zram,
 	return entry->refcount;
 }
 
+static struct zram_entry *__zram_dedup_get(struct zram *zram,
+				struct zram_hash *hash, unsigned char *mem,
+				struct zram_entry *entry)
+{
+	struct zram_entry *tmp, *prev = NULL;
+	struct rb_node *rb_node;
+
+	/* find left-most entry with same checksum */
+	while ((rb_node = rb_prev(&entry->rb_node))) {
+		tmp = rb_entry(rb_node, struct zram_entry, rb_node);
+		if (tmp->checksum != entry->checksum)
+			break;
+
+		entry = tmp;
+	}
+
+again:
+	entry->refcount++;
+	atomic64_add(entry->len, &zram->stats.dup_data_size);
+	spin_unlock(&hash->lock);
+
+	if (prev)
+		zram_entry_free(zram, prev);
+
+	if (zram_dedup_match(zram, entry, mem))
+		return entry;
+
+	spin_lock(&hash->lock);
+	tmp = NULL;
+	rb_node = rb_next(&entry->rb_node);
+	if (rb_node)
+		tmp = rb_entry(rb_node, struct zram_entry, rb_node);
+
+	if (tmp && (tmp->checksum == entry->checksum)) {
+		prev = entry;
+		entry = tmp;
+		goto again;
+	}
+
+	spin_unlock(&hash->lock);
+	zram_entry_free(zram, entry);
+
+	return NULL;
+}
+
 static struct zram_entry *zram_dedup_get(struct zram *zram,
 				unsigned char *mem, u32 checksum)
 {
@@ -122,18 +167,8 @@ static struct zram_entry *zram_dedup_get(struct zram *zram,
 	rb_node = hash->rb_root.rb_node;
 	while (rb_node) {
 		entry = rb_entry(rb_node, struct zram_entry, rb_node);
-		if (checksum == entry->checksum) {
-			entry->refcount++;
-			atomic64_add(entry->len, &zram->stats.dup_data_size);
-			spin_unlock(&hash->lock);
-
-			if (zram_dedup_match(zram, entry, mem))
-				return entry;
-
-			zram_entry_free(zram, entry);
-
-			return NULL;
-		}
+		if (checksum == entry->checksum)
+			return __zram_dedup_get(zram, hash, mem, entry);
 
 		if (checksum < entry->checksum)
 			rb_node = rb_node->rb_left;
-- 
2.7.4

Powered by blists - more mailing lists