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 95215aa6a75e..7d2a996c307e 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)