ceph: use strong hash function for mapping objects to pgs (cfbbcd24) · Commits · 戴 / test

fs/ceph/ceph_fs.c

+70 −23

Original line number	Diff line number	Diff line
		@@ -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
		/*
		* 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)

		/* partial hash update function. Assume roughly 4 bits per character */
		static unsigned long ceph_partial_name_hash(unsigned long c,
		unsigned long prevhash)
		unsigned int ceph_full_name_hash(const char *str, unsigned int length)
		{
		return (prevhash + (c << 4) + (c >> 4)) * 11;
		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;
		}

		/*
		* Finally: cut down the number of bits to a int value (and try to avoid
		* losing bits)
		*/
		static unsigned long ceph_end_name_hash(unsigned long hash)
		{
		return hash & 0xffffffff;
		/* 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);

		/* Compute the hash for a name string. */
		unsigned int ceph_full_name_hash(const char *name, unsigned int len)
		{
		unsigned long hash = ceph_init_name_hash();
		while (len--)
		hash = ceph_partial_name_hash(*name++, hash);
		return ceph_end_name_hash(hash);
		return c;
		}

fs/ceph/ceph_fs.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -38,7 +38,7 @@
		#define CEPH_OSD_PROTOCOL 7 /* cluster internal */
		#define CEPH_MDS_PROTOCOL 9 /* cluster internal */
		#define CEPH_MON_PROTOCOL 5 /* cluster internal */
		#define CEPH_OSDC_PROTOCOL 21 /* server/client */
		#define CEPH_OSDC_PROTOCOL 22 /* server/client */
		#define CEPH_MDSC_PROTOCOL 29 /* server/client */
		#define CEPH_MONC_PROTOCOL 15 /* server/client */

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