Finally, the first use of previous two patches: Eliminate the
separate ad-hoc string hash functions in the sunrpc code.
This also eliminates the only caller of hash_long which asks for
more than 32 bits of output.
sunrpc guys: Is it okay if I send this to Linus directly?
Signed-off-by: George Spelvin <linux@xxxxxxxxxxxxxxxxxxx>
Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Cc: linux-nfs@xxxxxxxxxxxxxxx
---
I have't heard anything from the linix-NFS crowd, so this is a re-ping.
I've been having some e-mail troubles leading to increased spam scores
due to a recent domain name change, so this is a resend from a different
address in case the previous copy got binned.
I'll happily send along the entire patch series, but the tl;dr is this
is part of a patch series that improves the <linux/hash.h> and fs/namei.c
hash functions, implementing Linus's suggestion:
On Mon, 02 May 2016 at 09:24:21, Linus Torvalds wrote:
> That said, I actually think hash_str() should be killed entirely.
> Better just use what we use for pathnames: full_name_hash() (which
> gets a pointer and length) and hash_name (which gets the string).
>
> Those functions do the "word-at-a-time" optimization, and they should
> do a good enough job. If they aren't, we should fix them, because they
> are a hell of a lot more important than anything that the svcauth code
> does.
He had a typically fulminating comment about the hard-to-predict if()
branch in the inner loop.
include/linux/sunrpc/svcauth.h | 36 +++++-------------------------------
1 file changed, 5 insertions(+), 31 deletions(-)
diff --git a/include/linux/sunrpc/svcauth.h b/include/linux/sunrpc/svcauth.h
index c00f53a4..ef2b2552 100644
--- a/include/linux/sunrpc/svcauth.h
+++ b/include/linux/sunrpc/svcauth.h
@@ -16,6 +16,7 @@
#include <linux/sunrpc/cache.h>
#include <linux/sunrpc/gss_api.h>
#include <linux/hash.h>
+#include <linux/stringhash.h>
#include <linux/cred.h>
struct svc_cred {
@@ -165,41 +166,14 @@ extern int svcauth_unix_set_client(struct svc_rqst *rqstp);
extern int unix_gid_cache_create(struct net *net);
extern void unix_gid_cache_destroy(struct net *net);
-static inline unsigned long hash_str(char *name, int bits)
+static inline unsigned long hash_str(char const *name, int bits)
{
- unsigned long hash = 0;
- unsigned long l = 0;
- int len = 0;
- unsigned char c;
- do {
- if (unlikely(!(c = *name++))) {
- c = (char)len; len = -1;
- }
- l = (l << 8) | c;
- len++;
- if ((len & (BITS_PER_LONG/8-1))==0)
- hash = hash_long(hash^l, BITS_PER_LONG);
- } while (len);
- return hash >> (BITS_PER_LONG - bits);
+ return hash_32(hashlen_hash(hash_string(name)), bits);
}
-static inline unsigned long hash_mem(char *buf, int length, int bits)
+static inline unsigned long hash_mem(char const *buf, int length, int bits)
{
- unsigned long hash = 0;
- unsigned long l = 0;
- int len = 0;
- unsigned char c;
- do {
- if (len == length) {
- c = (char)len; len = -1;
- } else
- c = *buf++;
- l = (l << 8) | c;
- len++;
- if ((len & (BITS_PER_LONG/8-1))==0)
- hash = hash_long(hash^l, BITS_PER_LONG);
- } while (len);
- return hash >> (BITS_PER_LONG - bits);
+ return hash_32(full_name_hash(buf, length), bits);
}
#endif /* __KERNEL__ */
--
2.8.1
--
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