lib/string.c: introduce memchr_inv()

memchr_inv() is mainly used to check whether the whole buffer is filled
with just a specified byte.

The function name and prototype are stolen from logfs and the
implementation is from SLUB.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Matt Mackall <mpm@selenic.com>
Acked-by: Joern Engel <joern@logfs.org>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 45 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 95215aa..7d2a996 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -655,49 +655,6 @@ static void init_object(struct kmem_cache *s, void *object, u8 val)
 		memset(p + s->objsize, val, s->inuse - s->objsize);
 }
 
-static u8 *check_bytes8(u8 *start, u8 value, unsigned int bytes)
-{
-	while (bytes) {
-		if (*start != value)
-			return start;
-		start++;
-		bytes--;
-	}
-	return NULL;
-}
-
-static u8 *check_bytes(u8 *start, u8 value, unsigned int bytes)
-{
-	u64 value64;
-	unsigned int words, prefix;
-
-	if (bytes <= 16)
-		return check_bytes8(start, value, bytes);
-
-	value64 = value | value << 8 | value << 16 | value << 24;
-	value64 = (value64 & 0xffffffff) | value64 << 32;
-	prefix = 8 - ((unsigned long)start) % 8;
-
-	if (prefix) {
-		u8 *r = check_bytes8(start, value, prefix);
-		if (r)
-			return r;
-		start += prefix;
-		bytes -= prefix;
-	}
-
-	words = bytes / 8;
-
-	while (words) {
-		if (*(u64 *)start != value64)
-			return check_bytes8(start, value, 8);
-		start += 8;
-		words--;
-	}
-
-	return check_bytes8(start, value, bytes % 8);
-}
-
 static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
 						void *from, void *to)
 {
@@ -712,7 +669,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
 	u8 *fault;
 	u8 *end;
 
-	fault = check_bytes(start, value, bytes);
+	fault = memchr_inv(start, value, bytes);
 	if (!fault)
 		return 1;
 
@@ -805,7 +762,7 @@ static int slab_pad_check(struct kmem_cache *s, struct page *page)
 	if (!remainder)
 		return 1;
 
-	fault = check_bytes(end - remainder, POISON_INUSE, remainder);
+	fault = memchr_inv(end - remainder, POISON_INUSE, remainder);
 	if (!fault)
 		return 1;
 	while (end > fault && end[-1] == POISON_INUSE)