6c0f3af72c
Add a ceph_dir_layout to the inode, and calculate dentry hash values based on the parent directory's specified dir_hash function. This is needed because the old default Linux dcache hash function is extremely week and leads to a poor distribution of files among dir fragments. Signed-off-by: Sage Weil <sage@newdream.net>
122 lines
2.8 KiB
C
122 lines
2.8 KiB
C
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#include <linux/ceph/types.h>
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#include <linux/module.h>
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/*
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* Robert Jenkin's hash function.
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* http://burtleburtle.net/bob/hash/evahash.html
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* This is in the public domain.
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*/
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#define mix(a, b, c) \
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do { \
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a = a - b; a = a - c; a = a ^ (c >> 13); \
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b = b - c; b = b - a; b = b ^ (a << 8); \
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c = c - a; c = c - b; c = c ^ (b >> 13); \
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a = a - b; a = a - c; a = a ^ (c >> 12); \
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b = b - c; b = b - a; b = b ^ (a << 16); \
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c = c - a; c = c - b; c = c ^ (b >> 5); \
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a = a - b; a = a - c; a = a ^ (c >> 3); \
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b = b - c; b = b - a; b = b ^ (a << 10); \
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c = c - a; c = c - b; c = c ^ (b >> 15); \
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} while (0)
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unsigned ceph_str_hash_rjenkins(const char *str, unsigned length)
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{
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const unsigned char *k = (const unsigned char *)str;
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__u32 a, b, c; /* the internal state */
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__u32 len; /* how many key bytes still need mixing */
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/* Set up the internal state */
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len = length;
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a = 0x9e3779b9; /* the golden ratio; an arbitrary value */
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b = a;
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c = 0; /* variable initialization of internal state */
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/* handle most of the key */
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while (len >= 12) {
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a = a + (k[0] + ((__u32)k[1] << 8) + ((__u32)k[2] << 16) +
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((__u32)k[3] << 24));
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b = b + (k[4] + ((__u32)k[5] << 8) + ((__u32)k[6] << 16) +
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((__u32)k[7] << 24));
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c = c + (k[8] + ((__u32)k[9] << 8) + ((__u32)k[10] << 16) +
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((__u32)k[11] << 24));
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mix(a, b, c);
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k = k + 12;
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len = len - 12;
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}
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/* handle the last 11 bytes */
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c = c + length;
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switch (len) { /* all the case statements fall through */
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case 11:
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c = c + ((__u32)k[10] << 24);
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case 10:
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c = c + ((__u32)k[9] << 16);
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case 9:
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c = c + ((__u32)k[8] << 8);
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/* the first byte of c is reserved for the length */
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case 8:
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b = b + ((__u32)k[7] << 24);
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case 7:
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b = b + ((__u32)k[6] << 16);
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case 6:
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b = b + ((__u32)k[5] << 8);
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case 5:
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b = b + k[4];
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case 4:
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a = a + ((__u32)k[3] << 24);
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case 3:
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a = a + ((__u32)k[2] << 16);
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case 2:
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a = a + ((__u32)k[1] << 8);
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case 1:
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a = a + k[0];
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/* case 0: nothing left to add */
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}
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mix(a, b, c);
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return c;
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}
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/*
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* linux dcache hash
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*/
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unsigned ceph_str_hash_linux(const char *str, unsigned length)
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{
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unsigned long hash = 0;
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unsigned char c;
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while (length--) {
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c = *str++;
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hash = (hash + (c << 4) + (c >> 4)) * 11;
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}
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return hash;
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}
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unsigned ceph_str_hash(int type, const char *s, unsigned len)
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{
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switch (type) {
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case CEPH_STR_HASH_LINUX:
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return ceph_str_hash_linux(s, len);
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case CEPH_STR_HASH_RJENKINS:
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return ceph_str_hash_rjenkins(s, len);
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default:
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return -1;
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}
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}
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EXPORT_SYMBOL(ceph_str_hash);
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const char *ceph_str_hash_name(int type)
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{
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switch (type) {
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case CEPH_STR_HASH_LINUX:
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return "linux";
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case CEPH_STR_HASH_RJENKINS:
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return "rjenkins";
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default:
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return "unknown";
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}
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}
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EXPORT_SYMBOL(ceph_str_hash_name);
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