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dcache: allow word-at-a-time name hashing with big-endian CPUs

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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>
This commit is contained in:
Will Deacon 2013-12-12 17:40:21 +00:00 • committed by Linus Torvalds
parent 319720f534
commit a5c21dcefa
3 changed files with 4 additions and 7 deletions
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2
include/linux/dcache.h
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@ -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
/*