linux-kernel - Re: [PATCH v7 07/16] net,9p: use new hashtable implementation

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Date:	Mon, 29 Oct 2012 08:15:06 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	torvalds@...ux-foundation.org, tj@...nel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, paul.gortmaker@...driver.com,
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	netdev@...r.kernel.org, josh@...htriplett.org,
	eric.dumazet@...il.com, axboe@...nel.dk, agk@...hat.com,
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Subject: Re: [PATCH v7 07/16] net,9p: use new hashtable implementation

* Sasha Levin (levinsasha928@...il.com) 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@...il.com>
> ---
>  net/9p/error.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/net/9p/error.c b/net/9p/error.c
> index 2ab2de7..a5cc7dd 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>

missing newline.

>  /**
>   * 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 ERR_HASH_BITS 5
> +static DEFINE_HASHTABLE(hash_errmap, ERR_HASH_BITS);
>  
>  /* FixMe - reduce to a reasonable size */
>  static struct errormap errmap[] = {
> @@ -193,18 +193,17 @@ static struct errormap errmap[] = {
>  int p9_error_init(void)
>  {
>  	struct errormap *c;
> -	int bucket;
> +	u32 hash;
>  
>  	/* initialize hash table */
> -	for (bucket = 0; bucket < ERRHASHSZ; bucket++)
> -		INIT_HLIST_HEAD(&hash_errmap[bucket]);
> +	hash_init(hash_errmap);

As for most of the other patches in this series, the hash_init is
redundant for a statically defined hash table.

Thanks,

Mathieu

>  
>  	/* 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;
> +		hash = jhash(c->name, c->namelen, 0);
>  		INIT_HLIST_NODE(&c->list);
> -		hlist_add_head(&c->list, &hash_errmap[bucket]);
> +		hash_add(hash_errmap, &c->list, hash);
>  	}
>  
>  	return 1;
> @@ -223,13 +222,13 @@ int p9_errstr2errno(char *errstr, int len)
>  	int errno;
>  	struct hlist_node *p;
>  	struct errormap *c;
> -	int bucket;
> +	u32 hash;
>  
>  	errno = 0;
>  	p = NULL;
>  	c = NULL;
> -	bucket = jhash(errstr, len, 0) % ERRHASHSZ;
> -	hlist_for_each_entry(c, p, &hash_errmap[bucket], list) {
> +	hash = jhash(errstr, len, 0);
> +	hash_for_each_possible(hash_errmap, c, p, list, hash) {
>  		if (c->namelen == len && !memcmp(c->name, errstr, len)) {
>  			errno = c->val;
>  			break;
> -- 
> 1.7.12.4
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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