1 files changed, 70 insertions, 23 deletions

diff --git a/fs/ceph/ceph_fs.c b/fs/ceph/ceph_fs.c
index a950b4083577..b3ecf1b07521 100644
--- a/fs/ceph/ceph_fs.c
+++ b/fs/ceph/ceph_fs.c
@@ -73,32 +73,79 @@ int ceph_caps_for_mode(int mode)
         return 0;
 }
 
-/* Name hashing routines. Initial hash value */
-/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
-#define ceph_init_name_hash()           0
-
-/* partial hash update function. Assume roughly 4 bits per character */
-static unsigned long ceph_partial_name_hash(unsigned long c,
-                                            unsigned long prevhash)
-{
-        return (prevhash + (c << 4) + (c >> 4)) * 11;
-}
-
 /*
- * Finally: cut down the number of bits to a int value (and try to avoid
- * losing bits)
+ * Robert Jenkin's hash function.
+ * http://burtleburtle.net/bob/hash/evahash.html
+ * This is in the public domain.
  */
-static unsigned long ceph_end_name_hash(unsigned long hash)
-{
-        return hash & 0xffffffff;
-}
+#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)
 
-/* Compute the hash for a name string. */
-unsigned int ceph_full_name_hash(const char *name, unsigned int len)
+unsigned int ceph_full_name_hash(const char *str, unsigned int length)
 {
-        unsigned long hash = ceph_init_name_hash();
-        while (len--)
-                hash = ceph_partial_name_hash(*name++, hash);
-        return ceph_end_name_hash(hash);
+        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;
 }