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vfs: make the string hashes salt the hash

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We always mixed in the parent pointer into the dentry name hash, but we
did it late at lookup time.  It turns out that we can simplify that
lookup-time action by salting the hash with the parent pointer early
instead of late.

A few other users of our string hashes also wanted to mix in their own
pointers into the hash, and those are updated to use the same mechanism.

Hash users that don't have any particular initial salt can just use the
NULL pointer as a no-salt.

Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds
2016-06-10 07:51:30 -07:00
parent 147d9e7bca
commit 8387ff2577
38 changed files with 99 additions and 89 deletions
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4
fs/kernfs/dir.c
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@@ -336,11 +336,11 @@ struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
*/
static unsigned int kernfs_name_hash(const char *name, const void *ns)
{
unsigned long hash = init_name_hash();
unsigned long hash = init_name_hash(ns);
unsigned int len = strlen(name);
while (len--)
hash = partial_name_hash(*name++, hash);
hash = (end_name_hash(hash) ^ hash_ptr((void *)ns, 31));
hash = end_name_hash(hash);
hash &= 0x7fffffffU;
/* Reserve hash numbers 0, 1 and INT_MAX for magic directory entries */
if (hash < 2)