Define the hash functions used for placing dentries in directories and for mapping objects into placement groups. Signed-off-by: Sage Weil <sage@xxxxxxxxxxxx> --- fs/ceph/ceph_hash.c | 118 +++++++++++++++++++++++++++++++++++++++++++++++++++ fs/ceph/ceph_hash.h | 13 ++++++ 2 files changed, 131 insertions(+), 0 deletions(-) create mode 100644 fs/ceph/ceph_hash.c create mode 100644 fs/ceph/ceph_hash.h diff --git a/fs/ceph/ceph_hash.c b/fs/ceph/ceph_hash.c new file mode 100644 index 0000000..bd57001 --- /dev/null +++ b/fs/ceph/ceph_hash.c @@ -0,0 +1,118 @@ + +#include "types.h" + +/* + * Robert Jenkin's hash function. + * http://burtleburtle.net/bob/hash/evahash.html + * This is in the public domain. + */ +#define mix(a, b, c) \ + do { \ + a = a - b; a = a - c; a = a ^ (c >> 13); \ + b = b - c; b = b - a; b = b ^ (a << 8); \ + c = c - a; c = c - b; c = c ^ (b >> 13); \ + a = a - b; a = a - c; a = a ^ (c >> 12); \ + b = b - c; b = b - a; b = b ^ (a << 16); \ + c = c - a; c = c - b; c = c ^ (b >> 5); \ + a = a - b; a = a - c; a = a ^ (c >> 3); \ + b = b - c; b = b - a; b = b ^ (a << 10); \ + c = c - a; c = c - b; c = c ^ (b >> 15); \ + } while (0) + +unsigned ceph_str_hash_rjenkins(const char *str, unsigned length) +{ + const unsigned char *k = (const unsigned char *)str; + __u32 a, b, c; /* the internal state */ + __u32 len; /* how many key bytes still need mixing */ + + /* Set up the internal state */ + len = length; + a = 0x9e3779b9; /* the golden ratio; an arbitrary value */ + b = a; + c = 0; /* variable initialization of internal state */ + + /* handle most of the key */ + while (len >= 12) { + a = a + (k[0] + ((__u32)k[1] << 8) + ((__u32)k[2] << 16) + + ((__u32)k[3] << 24)); + b = b + (k[4] + ((__u32)k[5] << 8) + ((__u32)k[6] << 16) + + ((__u32)k[7] << 24)); + c = c + (k[8] + ((__u32)k[9] << 8) + ((__u32)k[10] << 16) + + ((__u32)k[11] << 24)); + mix(a, b, c); + k = k + 12; + len = len - 12; + } + + /* handle the last 11 bytes */ + c = c + length; + switch (len) { /* all the case statements fall through */ + case 11: + c = c + ((__u32)k[10] << 24); + case 10: + c = c + ((__u32)k[9] << 16); + case 9: + c = c + ((__u32)k[8] << 8); + /* the first byte of c is reserved for the length */ + case 8: + b = b + ((__u32)k[7] << 24); + case 7: + b = b + ((__u32)k[6] << 16); + case 6: + b = b + ((__u32)k[5] << 8); + case 5: + b = b + k[4]; + case 4: + a = a + ((__u32)k[3] << 24); + case 3: + a = a + ((__u32)k[2] << 16); + case 2: + a = a + ((__u32)k[1] << 8); + case 1: + a = a + k[0]; + /* case 0: nothing left to add */ + } + mix(a, b, c); + + return c; +} + +/* + * linux dcache hash + */ +unsigned ceph_str_hash_linux(const char *str, unsigned length) +{ + unsigned long hash = 0; + unsigned char c; + + while (length--) { + c = *str++; + hash = (hash + (c << 4) + (c >> 4)) * 11; + } + return hash; +} + + +unsigned ceph_str_hash(int type, const char *s, unsigned len) +{ + switch (type) { + case CEPH_STR_HASH_LINUX: + return ceph_str_hash_linux(s, len); + case CEPH_STR_HASH_RJENKINS: + return ceph_str_hash_rjenkins(s, len); + default: + return -1; + } +} + +const char *ceph_str_hash_name(int type) +{ + switch (type) { + case CEPH_STR_HASH_LINUX: + return "linux"; + case CEPH_STR_HASH_RJENKINS: + return "rjenkins"; + default: + return "unknown"; + } +} diff --git a/fs/ceph/ceph_hash.h b/fs/ceph/ceph_hash.h new file mode 100644 index 0000000..5ac470c --- /dev/null +++ b/fs/ceph/ceph_hash.h @@ -0,0 +1,13 @@ +#ifndef _FS_CEPH_HASH_H +#define _FS_CEPH_HASH_H + +#define CEPH_STR_HASH_LINUX 0x1 /* linux dcache hash */ +#define CEPH_STR_HASH_RJENKINS 0x2 /* robert jenkins' */ + +extern unsigned ceph_str_hash_linux(const char *s, unsigned len); +extern unsigned ceph_str_hash_rjenkins(const char *s, unsigned len); + +extern unsigned ceph_str_hash(int type, const char *s, unsigned len); +extern const char *ceph_str_hash_name(int type); + +#endif -- 1.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
