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authorWill Deacon <will.deacon@arm.com>2013-12-12 17:40:21 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2013-12-12 10:39:01 -0800
commita5c21dcefa1c3d759457a604b3cfc4af29c8713f (patch)
tree6832dfcb836f8d5043ba70f17a0ea9c2c428bc4d /fs
parent319720f534d88039615bceb88d4bc094a7cd4ce9 (diff)
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>
Diffstat (limited to 'fs')
-rw-r--r--fs/dcache.c2
-rw-r--r--fs/namei.c7
2 files changed, 2 insertions, 7 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 4bdb300b16e2..6055d61811d3 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));
}
diff --git a/fs/namei.c b/fs/namei.c
index c53d3a9547f9..3531deebad30 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -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);