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| author | Will Deacon <will.deacon@arm.com> | 2013-12-12 17:40:21 +0000 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-12-12 10:39:01 -0800 |
| commit | a5c21dcefa1c3d759457a604b3cfc4af29c8713f (patch) | |
| tree | 6832dfcb836f8d5043ba70f17a0ea9c2c428bc4d | |
| parent | 319720f534d88039615bceb88d4bc094a7cd4ce9 (diff) | |
| download | op-kernel-dev-a5c21dcefa1c3d759457a604b3cfc4af29c8713f.zip op-kernel-dev-a5c21dcefa1c3d759457a604b3cfc4af29c8713f.tar.gz | |
dcache: allow word-at-a-time name hashing with big-endian CPUs
When explicitly hashing the end of a string with the word-at-a-time
interface, we have to be careful which end of the word we pick up.
On big-endian CPUs, the upper-bits will contain the data we're after, so
ensure we generate our masks accordingly (and avoid hashing whatever
random junk may have been sitting after the string).
This patch adds a new dcache helper, bytemask_from_count, which creates
a mask appropriate for the CPU endianness.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/dcache.c | 2 | ||||
| -rw-r--r-- | fs/namei.c | 7 | ||||
| -rw-r--r-- | include/linux/dcache.h | 2 |
3 files changed, 4 insertions, 7 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 4bdb300..6055d61 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -192,7 +192,7 @@ static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char if (!tcount) return 0; } - mask = ~(~0ul << tcount*8); + mask = bytemask_from_count(tcount); return unlikely(!!((a ^ b) & mask)); } @@ -1598,11 +1598,6 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd) * do a "get_unaligned()" if this helps and is sufficiently * fast. * - * - Little-endian machines (so that we can generate the mask - * of low bytes efficiently). Again, we *could* do a byte - * swapping load on big-endian architectures if that is not - * expensive enough to make the optimization worthless. - * * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we * do not trap on the (extremely unlikely) case of a page * crossing operation. @@ -1646,7 +1641,7 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len) if (!len) goto done; } - mask = ~(~0ul << len*8); + mask = bytemask_from_count(len); hash += mask & a; done: return fold_hash(hash); diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 57e87e7..bf72e9a 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -29,8 +29,10 @@ struct vfsmount; /* The hash is always the low bits of hash_len */ #ifdef __LITTLE_ENDIAN #define HASH_LEN_DECLARE u32 hash; u32 len; + #define bytemask_from_count(cnt) (~(~0ul << (cnt)*8)) #else #define HASH_LEN_DECLARE u32 len; u32 hash; + #define bytemask_from_count(cnt) (~(~0ul >> (cnt)*8)) #endif /* |
