Re: [RFC v2 7/7] net,9p: use new hashtable implementation

Eric Dumazet
2012-08-03T18:00:51Z

On Fri, 2012-08-03 at 16:23 +0200, Sasha Levin wrote:
> Switch 9p error table to use the new hashtable implementation. This reduces the amount of
> generic unrelated code in 9p.
>
> Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
> ---
> net/9p/error.c | 17 ++++++++---------
> 1 files changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/net/9p/error.c b/net/9p/error.c
> index 2ab2de7..f1037db 100644
> --- a/net/9p/error.c
> +++ b/net/9p/error.c
> @@ -34,7 +34,7 @@
> #include <linux/jhash.h>
> #include <linux/errno.h>
> #include <net/9p/9p.h>
> -
> +#include <linux/hashtable.h>
> /**
> * struct errormap - map string errors from Plan 9 to Linux numeric ids
> * @name: string sent over 9P
> @@ -50,8 +50,8 @@ struct errormap {
> struct hlist_node list;
> };
>
> -#define ERRHASHSZ 32
> -static struct hlist_head hash_errmap[ERRHASHSZ];

> +#define ERRHASHSZ 5

This name is confusing, it should mention SHIFT or BITS maybe...

> +DEFINE_STATIC_HASHTABLE(hash_errmap, ERRHASHSZ);
>
> /* FixMe - reduce to a reasonable size */
> static struct errormap errmap[] = {
> @@ -196,15 +196,14 @@ int p9_error_init(void)
> int bucket;

remove "int bucket" and use :

u32 hash;

>
> /* initialize hash table */
> - for (bucket = 0; bucket < ERRHASHSZ; bucket++)
> - INIT_HLIST_HEAD(&hash_errmap[bucket]);
> + hash_init(&hash_errmap, ERRHASHSZ);

Why is hash_init() even needed ?

If hash is "DEFINE_STATIC_HASHTABLE(...)", its already ready for use !

>
> /* load initial error map into hash table */
> for (c = errmap; c->name != NULL; c++) {
> c->namelen = strlen(c->name);
> - bucket = jhash(c->name, c->namelen, 0) % ERRHASHSZ;
> + bucket = jhash(c->name, c->namelen, 0);

bucket is a wrong name here, its more like "key" or "hash"

> INIT_HLIST_NODE(&c->list);
> - hlist_add_head(&c->list, &hash_errmap[bucket]);
> + hash_add(&hash_errmap, &c->list, bucket);
> }
>
> return 1;
> @@ -228,8 +227,8 @@ int p9_errstr2errno(char *errstr, int len)
> errno = 0;
> p = NULL;
> c = NULL;
> - bucket = jhash(errstr, len, 0) % ERRHASHSZ;
> - hlist_for_each_entry(c, p, &hash_errmap[bucket], list) {
> + bucket = jhash(errstr, len, 0);

hash = jhash(errstr, len, 0);

> + hash_for_each_possible(&hash_errmap, p, c, list, bucket) {
> if (c->namelen == len && !memcmp(c->name, errstr, len)) {
> errno = c->val;
> break;