Pull out string hash to <linux/stringhash.h>

... so they can be used without the rest of <linux/dcache.h> The hashlen_* macros will make sense next patch.

George Spelvin committed 10 years ago

Commit f4bcbe71 parent 0fed3ac2 files · +73 −26Browse files

Unified · Split

2 files

include/linux/dcache.h +1 −26
include/linux/stringhash.h +72 −0

@@ -10,6 +10,7 @@ · 9 unmodified lines
10	#include <linux/cache.h>	10	#include <linux/cache.h>
11	#include <linux/rcupdate.h>	11	#include <linux/rcupdate.h>
12	#include <linux/lockref.h>	12	#include <linux/lockref.h>
		13	#include <linux/stringhash.h>
13		14
14	struct path;	15	struct path;
15	struct vfsmount;	16	struct vfsmount;
@@ -52,9 +53,6 @@ struct qstr { · 36 unmodified lines
52	};	53	};
53		54
54	#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }	55	#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
55	#define hashlen_hash(hashlen) ((u32) (hashlen))
56	#define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
57	#define hashlen_create(hash,len) (((u64)(len)<<32)\|(u32)(hash))
58		56
59	struct dentry_stat_t {	57	struct dentry_stat_t {
60	long nr_dentry;	58	long nr_dentry;
@@ -65,29 +63,6 @@ struct dentry_stat_t { · 4 unmodified lines
65	};	63	};
66	extern struct dentry_stat_t dentry_stat;	64	extern struct dentry_stat_t dentry_stat;
67		65
68	/* Name hashing routines. Initial hash value */
69	/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
70	#define init_name_hash() 0
71
72	/* partial hash update function. Assume roughly 4 bits per character */
73	static inline unsigned long
74	partial_name_hash(unsigned long c, unsigned long prevhash)
75	{
76	return (prevhash + (c << 4) + (c >> 4)) * 11;
77	}
78
79	/*
80	* Finally: cut down the number of bits to a int value (and try to avoid
81	* losing bits)
82	*/
83	static inline unsigned long end_name_hash(unsigned long hash)
84	{
85	return (unsigned int) hash;
86	}
87
88	/* Compute the hash for a name string. */
89	extern unsigned int full_name_hash(const unsigned char *, unsigned int);
90
91	/*	66	/*
92	* Try to keep struct dentry aligned on 64 byte cachelines (this will	67	* Try to keep struct dentry aligned on 64 byte cachelines (this will
93	* give reasonable cacheline footprint with larger lines without the	68	* give reasonable cacheline footprint with larger lines without the

include/linux/stringhash.h+72−0

@@ -0,0 +1,72 @@
	1	#ifndef __LINUX_STRINGHASH_H
	2	#define __LINUX_STRINGHASH_H
	3
	4	#include <linux/types.h>
	5
	6	/*
	7	* Routines for hashing strings of bytes to a 32-bit hash value.
	8	*
	9	* These hash functions are NOT GUARANTEED STABLE between kernel
	10	* versions, architectures, or even repeated boots of the same kernel.
	11	* (E.g. they may depend on boot-time hardware detection or be
	12	* deliberately randomized.)
	13	*
	14	* They are also not intended to be secure against collisions caused by
	15	* malicious inputs; much slower hash functions are required for that.
	16	*
	17	* They are optimized for pathname components, meaning short strings.
	18	* Even if a majority of files have longer names, the dynamic profile of
	19	* pathname components skews short due to short directory names.
	20	* (E.g. /usr/lib/libsesquipedalianism.so.3.141.)
	21	*/
	22
	23	/*
	24	* Version 1: one byte at a time. Example of use:
	25	*
	26	* unsigned long hash = init_name_hash;
	27	* while (*p)
	28	* hash = partial_name_hash(tolower(*p++), hash);
	29	* hash = end_name_hash(hash);
	30	*
	31	* Although this is designed for bytes, fs/hfsplus/unicode.c
	32	* abuses it to hash 16-bit values.
	33	*/
	34
	35	/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
	36	#define init_name_hash() 0
	37
	38	/* partial hash update function. Assume roughly 4 bits per character */
	39	static inline unsigned long
	40	partial_name_hash(unsigned long c, unsigned long prevhash)
	41	{
	42	return (prevhash + (c << 4) + (c >> 4)) * 11;
	43	}
	44
	45	/*
	46	* Finally: cut down the number of bits to a int value (and try to avoid
	47	* losing bits)
	48	*/
	49	static inline unsigned long end_name_hash(unsigned long hash)
	50	{
	51	return (unsigned int)hash;
	52	}
	53
	54	/*
	55	* Version 2: One word (32 or 64 bits) at a time.
	56	* If CONFIG_DCACHE_WORD_ACCESS is defined (meaning <asm/word-at-a-time.h>
	57	* exists, which describes major Linux platforms like x86 and ARM), then
	58	* this computes a different hash function much faster.
	59	*
	60	* If not set, this falls back to a wrapper around the preceding.
	61	*/
	62	extern unsigned int full_name_hash(const unsigned char *, unsigned int);
	63
	64	/*
	65	* A hash_len is a u64 with the hash of a string in the low
	66	* half and the length in the high half.
	67	*/
	68	#define hashlen_hash(hashlen) ((u32)(hashlen))
	69	#define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
	70	#define hashlen_create(hash, len) ((u64)(len)<<32 \| (u32)(hash))
	71
	72	#endif /* __LINUX_STRINGHASH_H */