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authorLinus Torvalds <torvalds@linux-foundation.org>2016-05-28 16:15:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-28 16:15:25 -0700
commit7e0fb73c52c4037b4d5ef9ff56c7296a3151bd92 (patch)
tree9ab023505d388563d937b3c3ac26ef3c2045dba2 /fs/dcache.c
parent4e8440b3b6b801953b2e53c55491cf98fc8f6c01 (diff)
parent4684fe95300c071983f77653e354c040fe80a265 (diff)
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Merge branch 'hash' of git://ftp.sciencehorizons.net/linux
Pull string hash improvements from George Spelvin: "This series does several related things: - Makes the dcache hash (fs/namei.c) useful for general kernel use. (Thanks to Bruce for noticing the zero-length corner case) - Converts the string hashes in <linux/sunrpc/svcauth.h> to use the above. - Avoids 64-bit multiplies in hash_64() on 32-bit platforms. Two 32-bit multiplies will do well enough. - Rids the world of the bad hash multipliers in hash_32. This finishes the job started in commit 689de1d6ca95 ("Minimal fix-up of bad hashing behavior of hash_64()") The vast majority of Linux architectures have hardware support for 32x32-bit multiply and so derive no benefit from "simplified" multipliers. The few processors that do not (68000, h8/300 and some models of Microblaze) have arch-specific implementations added. Those patches are last in the series. - Overhauls the dcache hash mixing. The patch in commit 0fed3ac866ea ("namei: Improve hash mixing if CONFIG_DCACHE_WORD_ACCESS") was an off-the-cuff suggestion. Replaced with a much more careful design that's simultaneously faster and better. (My own invention, as there was noting suitable in the literature I could find. Comments welcome!) - Modify the hash_name() loop to skip the initial HASH_MIX(). This would let us salt the hash if we ever wanted to. - Sort out partial_name_hash(). The hash function is declared as using a long state, even though it's truncated to 32 bits at the end and the extra internal state contributes nothing to the result. And some callers do odd things: - fs/hfs/string.c only allocates 32 bits of state - fs/hfsplus/unicode.c uses it to hash 16-bit unicode symbols not bytes - Modify bytemask_from_count to handle inputs of 1..sizeof(long) rather than 0..sizeof(long)-1. This would simplify users other than full_name_hash" Special thanks to Bruce Fields for testing and finding bugs in v1. (I learned some humbling lessons about "obviously correct" code.) On the arch-specific front, the m68k assembly has been tested in a standalone test harness, I've been in contact with the Microblaze maintainers who mostly don't care, as the hardware multiplier is never omitted in real-world applications, and I haven't heard anything from the H8/300 world" * 'hash' of git://ftp.sciencehorizons.net/linux: h8300: Add <asm/hash.h> microblaze: Add <asm/hash.h> m68k: Add <asm/hash.h> <linux/hash.h>: Add support for architecture-specific functions fs/namei.c: Improve dcache hash function Eliminate bad hash multipliers from hash_32() and hash_64() Change hash_64() return value to 32 bits <linux/sunrpc/svcauth.h>: Define hash_str() in terms of hashlen_string() fs/namei.c: Add hashlen_string() function Pull out string hash to <linux/stringhash.h>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index c622872c12c5..ad4a542e9bab 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1670,8 +1670,7 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
struct qstr q;
q.name = name;
- q.len = strlen(name);
- q.hash = full_name_hash(q.name, q.len);
+ q.hash_len = hashlen_string(name);
return d_alloc(parent, &q);
}
EXPORT_SYMBOL(d_alloc_name);