Commit fcfd2fbf authored by George Spelvin's avatar George Spelvin

fs/namei.c: Add hashlen_string() function

We'd like to make more use of the highly-optimized dcache hash functions
throughout the kernel, rather than have every subsystem create its own,
and a function that hashes basic null-terminated strings is required
for that.

(The name is to emphasize that it returns both hash and length.)

It's actually useful in the dcache itself, specifically d_alloc_name().
Other uses in the next patch.

full_name_hash() is also tweaked to make it more generally useful:
1) Take a "char *" rather than "unsigned char *" argument, to
   be consistent with hash_name().
2) Handle zero-length inputs.  If we want more callers, we don't want
   to make them worry about corner cases.
Signed-off-by: default avatarGeorge Spelvin <linux@sciencehorizons.net>
parent f4bcbe79
......@@ -1653,8 +1653,7 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
struct qstr q;
q.name = name;
q.len = strlen(name);
q.hash = full_name_hash(q.name, q.len);
q.hash_len = hashlen_string(name);
return d_alloc(parent, &q);
}
EXPORT_SYMBOL(d_alloc_name);
......
......@@ -1822,19 +1822,20 @@ static inline unsigned long mix_hash(unsigned long hash)
#endif
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
/* Return the hash of a string of known length */
unsigned int full_name_hash(const char *name, unsigned int len)
{
unsigned long a, hash = 0;
for (;;) {
if (!len)
goto done;
a = load_unaligned_zeropad(name);
if (len < sizeof(unsigned long))
break;
hash = mix_hash(hash + a);
name += sizeof(unsigned long);
len -= sizeof(unsigned long);
if (!len)
goto done;
}
hash += a & bytemask_from_count(len);
done:
......@@ -1842,6 +1843,29 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len)
}
EXPORT_SYMBOL(full_name_hash);
/* Return the "hash_len" (hash and length) of a null-terminated string */
u64 hashlen_string(const char *name)
{
unsigned long a, adata, mask, hash, len;
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
hash = a = 0;
len = -sizeof(unsigned long);
do {
hash = mix_hash(hash + a);
len += sizeof(unsigned long);
a = load_unaligned_zeropad(name+len);
} while (!has_zero(a, &adata, &constants));
adata = prep_zero_mask(a, adata, &constants);
mask = create_zero_mask(adata);
hash += a & zero_bytemask(mask);
len += find_zero(mask);
return hashlen_create(fold_hash(hash), len);
}
EXPORT_SYMBOL(hashlen_string);
/*
* Calculate the length and hash of the path component, and
* return the "hash_len" as the result.
......@@ -1872,15 +1896,32 @@ static inline u64 hash_name(const char *name)
#else
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
/* Return the hash of a string of known length */
unsigned int full_name_hash(const char *name, unsigned int len)
{
unsigned long hash = init_name_hash();
while (len--)
hash = partial_name_hash(*name++, hash);
hash = partial_name_hash((unsigned char)*name++, hash);
return end_name_hash(hash);
}
EXPORT_SYMBOL(full_name_hash);
/* Return the "hash_len" (hash and length) of a null-terminated string */
u64 hash_string(const char *name)
{
unsigned long hash = init_name_hash();
unsigned long len = 0, c;
c = (unsigned char)*name;
do {
len++;
hash = partial_name_hash(c, hash);
c = (unsigned char)name[len];
} while (c);
return hashlen_create(end_name_hash(hash), len);
}
EXPORT_SYMBOL(hash_string);
/*
* We know there's a real path component here of at least
* one character.
......
#ifndef __LINUX_STRINGHASH_H
#define __LINUX_STRINGHASH_H
#include <linux/types.h>
#include <linux/compiler.h> /* For __pure */
#include <linux/types.h> /* For u32, u64 */
/*
* Routines for hashing strings of bytes to a 32-bit hash value.
......@@ -59,7 +60,7 @@ static inline unsigned long end_name_hash(unsigned long hash)
*
* If not set, this falls back to a wrapper around the preceding.
*/
extern unsigned int full_name_hash(const unsigned char *, unsigned int);
extern unsigned int __pure full_name_hash(const char *, unsigned int);
/*
* A hash_len is a u64 with the hash of a string in the low
......@@ -69,4 +70,7 @@ extern unsigned int full_name_hash(const unsigned char *, unsigned int);
#define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
#define hashlen_create(hash, len) ((u64)(len)<<32 | (u32)(hash))
/* Return the "hash_len" (hash and length) of a null-terminated string */
extern u64 __pure hashlen_string(const char *name);
#endif /* __LINUX_STRINGHASH_H */
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