Make the "word-at-a-time" helper functions more commonly usable
I have a new optimized x86 "strncpy_from_user()" that will use these
same helper functions for all the same reasons the name lookup code uses
them. This is preparation for that.
This moves them into an architecture-specific header file. It's
architecture-specific for two reasons:
- some of the functions are likely to want architecture-specific
implementations. Even if the current code happens to be "generic" in
the sense that it should work on any little-endian machine, it's
likely that the "multiply by a big constant and shift" implementation
is less than optimal for an architecture that has a guaranteed fast
bit count instruction, for example.
- I expect that if architectures like sparc want to start playing
around with this, we'll need to abstract out a few more details (in
particular the actual unaligned accesses). So we're likely to have
more architecture-specific stuff if non-x86 architectures start using
this.
(and if it turns out that non-x86 architectures don't start using
this, then having it in an architecture-specific header is still the
right thing to do, of course)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/namei.c b/fs/namei.c
index 1898198..0062dd1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1407,18 +1407,9 @@
*/
#ifdef CONFIG_DCACHE_WORD_ACCESS
-#ifdef CONFIG_64BIT
+#include <asm/word-at-a-time.h>
-/*
- * Jan Achrenius on G+: microoptimized version of
- * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
- * that works for the bytemasks without having to
- * mask them first.
- */
-static inline long count_masked_bytes(unsigned long mask)
-{
- return mask*0x0001020304050608ul >> 56;
-}
+#ifdef CONFIG_64BIT
static inline unsigned int fold_hash(unsigned long hash)
{
@@ -1428,15 +1419,6 @@
#else /* 32-bit case */
-/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
-static inline long count_masked_bytes(long mask)
-{
- /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
- long a = (0x0ff0001+mask) >> 23;
- /* Fix the 1 for 00 case */
- return a & mask;
-}
-
#define fold_hash(x) (x)
#endif
@@ -1464,17 +1446,6 @@
}
EXPORT_SYMBOL(full_name_hash);
-#define REPEAT_BYTE(x) ((~0ul / 0xff) * (x))
-#define ONEBYTES REPEAT_BYTE(0x01)
-#define SLASHBYTES REPEAT_BYTE('/')
-#define HIGHBITS REPEAT_BYTE(0x80)
-
-/* Return the high bit set in the first byte that is a zero */
-static inline unsigned long has_zero(unsigned long a)
-{
- return ((a - ONEBYTES) & ~a) & HIGHBITS;
-}
-
/*
* Calculate the length and hash of the path component, and
* return the length of the component;
@@ -1490,7 +1461,7 @@
len += sizeof(unsigned long);
a = *(unsigned long *)(name+len);
/* Do we have any NUL or '/' bytes in this word? */
- mask = has_zero(a) | has_zero(a ^ SLASHBYTES);
+ mask = has_zero(a) | has_zero(a ^ REPEAT_BYTE('/'));
} while (!mask);
/* The mask *below* the first high bit set */
