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| author | Stephen Hemminger <shemminger@vyatta.com> | 2009-10-27 19:24:46 -0700 |
|---|---|---|
| committer | James Morris <jmorris@namei.org> | 2009-10-29 11:17:33 +1100 |
| commit | 024e1a49411a1a7363e65db48edf1b09e9ee68ad (patch) | |
| tree | 628fb392d0230f2e46753c04dded209ef27124d1 /security | |
| parent | d6ba452128178091dab7a04d54f7e66fdc32fb39 (diff) | |
| download | linux-3.10-024e1a49411a1a7363e65db48edf1b09e9ee68ad.tar.gz linux-3.10-024e1a49411a1a7363e65db48edf1b09e9ee68ad.tar.bz2 linux-3.10-024e1a49411a1a7363e65db48edf1b09e9ee68ad.zip | |
tomoyo: improve hash bucket dispersion
When examining the network device name hash, it was discovered that
the low order bits of full_name_hash() are not very well dispersed
across the possible values. When used by filesystem code, this is handled
by folding with the function hash_long().
The only other non-filesystem usage of full_name_hash() at this time
appears to be in TOMOYO. This patch should fix that.
I do not use TOMOYO at this time, so this patch is build tested only.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'security')
| -rw-r--r-- | security/tomoyo/realpath.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c index 5f2e3326337..917f564cdab 100644 --- a/security/tomoyo/realpath.c +++ b/security/tomoyo/realpath.c @@ -13,6 +13,8 @@ #include <linux/mount.h> #include <linux/mnt_namespace.h> #include <linux/fs_struct.h> +#include <linux/hash.h> + #include "common.h" #include "realpath.h" @@ -263,7 +265,8 @@ static unsigned int tomoyo_quota_for_savename; * table. Frequency of appending strings is very low. So we don't need * large (e.g. 64k) hash size. 256 will be sufficient. */ -#define TOMOYO_MAX_HASH 256 +#define TOMOYO_HASH_BITS 8 +#define TOMOYO_MAX_HASH (1u<<TOMOYO_HASH_BITS) /* * tomoyo_name_entry is a structure which is used for linking @@ -315,6 +318,7 @@ const struct tomoyo_path_info *tomoyo_save_name(const char *name) struct tomoyo_free_memory_block_list *fmb; int len; char *cp; + struct list_head *head; if (!name) return NULL; @@ -325,9 +329,10 @@ const struct tomoyo_path_info *tomoyo_save_name(const char *name) return NULL; } hash = full_name_hash((const unsigned char *) name, len - 1); + head = &tomoyo_name_list[hash_long(hash, TOMOYO_HASH_BITS)]; + mutex_lock(&lock); - list_for_each_entry(ptr, &tomoyo_name_list[hash % TOMOYO_MAX_HASH], - list) { + list_for_each_entry(ptr, head, list) { if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name)) goto out; } @@ -365,7 +370,7 @@ const struct tomoyo_path_info *tomoyo_save_name(const char *name) tomoyo_fill_path_info(&ptr->entry); fmb->ptr += len; fmb->len -= len; - list_add_tail(&ptr->list, &tomoyo_name_list[hash % TOMOYO_MAX_HASH]); + list_add_tail(&ptr->list, head); if (fmb->len == 0) { list_del(&fmb->list); kfree(fmb); |