ceph: make CRUSH hash function a bucket property

Make the integer hash function a property of the bucket it is used on.  This
allows us to gracefully add support for new hash functions without starting
from scatch.

Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/crush/crush.h

@@ -102,7 +102,8 @@ extern const char *crush_bucket_alg_name(int alg);
 struct crush_bucket {
 	__s32 id;        /* this'll be negative */
 	__u16 type;      /* non-zero; type=0 is reserved for devices */
-	__u16 alg;       /* one of CRUSH_BUCKET_* */
+	__u8 alg;        /* one of CRUSH_BUCKET_* */
+	__u8 hash;       /* which hash function to use, CRUSH_HASH_* */
 	__u32 weight;    /* 16-bit fixed point */
 	__u32 size;      /* num items */
 	__s32 *items;

fs/ceph/crush/hash.c

@@ -1,5 +1,6 @@
 
 #include <linux/types.h>
+#include "hash.h"
 
 /*
  * Robert Jenkins' function for mixing 32-bit values
@@ -20,7 +21,7 @@
 
 #define crush_hash_seed 1315423911
 
-__u32 crush_hash32(__u32 a)
+static __u32 crush_hash32_rjenkins1(__u32 a)
 {
 	__u32 hash = crush_hash_seed ^ a;
 	__u32 b = a;
@@ -31,7 +32,7 @@ __u32 crush_hash32(__u32 a)
 	return hash;
 }
 
-__u32 crush_hash32_2(__u32 a, __u32 b)
+static __u32 crush_hash32_rjenkins1_2(__u32 a, __u32 b)
 {
 	__u32 hash = crush_hash_seed ^ a ^ b;
 	__u32 x = 231232;
@@ -42,7 +43,7 @@ __u32 crush_hash32_2(__u32 a, __u32 b)
 	return hash;
 }
 
-__u32 crush_hash32_3(__u32 a, __u32 b, __u32 c)
+static __u32 crush_hash32_rjenkins1_3(__u32 a, __u32 b, __u32 c)
 {
 	__u32 hash = crush_hash_seed ^ a ^ b ^ c;
 	__u32 x = 231232;
@@ -55,7 +56,7 @@ __u32 crush_hash32_3(__u32 a, __u32 b, __u32 c)
 	return hash;
 }
 
-__u32 crush_hash32_4(__u32 a, __u32 b, __u32 c, __u32 d)
+static __u32 crush_hash32_rjenkins1_4(__u32 a, __u32 b, __u32 c, __u32 d)
 {
 	__u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d;
 	__u32 x = 231232;
@@ -69,7 +70,8 @@ __u32 crush_hash32_4(__u32 a, __u32 b, __u32 c, __u32 d)
 	return hash;
 }
 
-__u32 crush_hash32_5(__u32 a, __u32 b, __u32 c, __u32 d, __u32 e)
+static __u32 crush_hash32_rjenkins1_5(__u32 a, __u32 b, __u32 c, __u32 d,
+				      __u32 e)
 {
 	__u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d ^ e;
 	__u32 x = 231232;
@@ -84,3 +86,64 @@ __u32 crush_hash32_5(__u32 a, __u32 b, __u32 c, __u32 d, __u32 e)
 	crush_hashmix(y, e, hash);
 	return hash;
 }
+
+
+__u32 crush_hash32(int type, __u32 a)
+{
+	switch (type) {
+	case CRUSH_HASH_RJENKINS1:
+		return crush_hash32_rjenkins1(a);
+	default:
+		return 0;
+	}
+}
+
+__u32 crush_hash32_2(int type, __u32 a, __u32 b)
+{
+	switch (type) {
+	case CRUSH_HASH_RJENKINS1:
+		return crush_hash32_rjenkins1_2(a, b);
+	default:
+		return 0;
+	}
+}
+
+__u32 crush_hash32_3(int type, __u32 a, __u32 b, __u32 c)
+{
+	switch (type) {
+	case CRUSH_HASH_RJENKINS1:
+		return crush_hash32_rjenkins1_3(a, b, c);
+	default:
+		return 0;
+	}
+}
+
+__u32 crush_hash32_4(int type, __u32 a, __u32 b, __u32 c, __u32 d)
+{
+	switch (type) {
+	case CRUSH_HASH_RJENKINS1:
+		return crush_hash32_rjenkins1_4(a, b, c, d);
+	default:
+		return 0;
+	}
+}
+
+__u32 crush_hash32_5(int type, __u32 a, __u32 b, __u32 c, __u32 d, __u32 e)
+{
+	switch (type) {
+	case CRUSH_HASH_RJENKINS1:
+		return crush_hash32_rjenkins1_5(a, b, c, d, e);
+	default:
+		return 0;
+	}
+}
+
+const char *crush_hash_name(int type)
+{
+	switch (type) {
+	case CRUSH_HASH_RJENKINS1:
+		return "rjenkins1";
+	default:
+		return "unknown";
+	}
+}

fs/ceph/crush/hash.h

@@ -1,12 +1,17 @@
 #ifndef _CRUSH_HASH_H
 #define _CRUSH_HASH_H
 
-extern __u32 crush_hash32(__u32 a);
-extern __u32 crush_hash32_2(__u32 a, __u32 b);
-extern __u32 crush_hash32_3(__u32 a, __u32 b, __u32 c);
-extern __u32 crush_hash32_4(__u32 a, __u32 b, __u32 c,
-			    __u32 d);
-extern __u32 crush_hash32_5(__u32 a, __u32 b, __u32 c,
-			    __u32 d, __u32 e);
+#define CRUSH_HASH_RJENKINS1   0
+
+#define CRUSH_HASH_DEFAULT CRUSH_HASH_RJENKINS1
+
+extern const char *crush_hash_name(int type);
+
+extern __u32 crush_hash32(int type, __u32 a);
+extern __u32 crush_hash32_2(int type, __u32 a, __u32 b);
+extern __u32 crush_hash32_3(int type, __u32 a, __u32 b, __u32 c);
+extern __u32 crush_hash32_4(int type, __u32 a, __u32 b, __u32 c, __u32 d);
+extern __u32 crush_hash32_5(int type, __u32 a, __u32 b, __u32 c, __u32 d,
+			    __u32 e);
 
 #endif

fs/ceph/crush/mapper.c

@@ -78,7 +78,7 @@ static int bucket_perm_choose(struct crush_bucket *bucket,
 
 		/* optimize common r=0 case */
 		if (pr == 0) {
-			s = crush_hash32_3(x, bucket->id, 0) %
+			s = crush_hash32_3(bucket->hash, x, bucket->id, 0) %
 				bucket->size;
 			bucket->perm[0] = s;
 			bucket->perm_n = 0xffff;   /* magic value, see below */
@@ -103,7 +103,7 @@ static int bucket_perm_choose(struct crush_bucket *bucket,
 		unsigned p = bucket->perm_n;
 		/* no point in swapping the final entry */
 		if (p < bucket->size - 1) {
-			i = crush_hash32_3(x, bucket->id, p) %
+			i = crush_hash32_3(bucket->hash, x, bucket->id, p) %
 				(bucket->size - p);
 			if (i) {
 				unsigned t = bucket->perm[p + i];
@@ -138,8 +138,8 @@ static int bucket_list_choose(struct crush_bucket_list *bucket,
 	int i;
 
 	for (i = bucket->h.size-1; i >= 0; i--) {
-		__u64 w = crush_hash32_4(x, bucket->h.items[i], r,
-					 bucket->h.id);
+		__u64 w = crush_hash32_4(bucket->h.hash,x, bucket->h.items[i],
+					 r, bucket->h.id);
 		w &= 0xffff;
 		dprintk("list_choose i=%d x=%d r=%d item %d weight %x "
 			"sw %x rand %llx",
@@ -198,7 +198,8 @@ static int bucket_tree_choose(struct crush_bucket_tree *bucket,
 	while (!terminal(n)) {
 		/* pick point in [0, w) */
 		w = bucket->node_weights[n];
-		t = (__u64)crush_hash32_4(x, n, r, bucket->h.id) * (__u64)w;
+		t = (__u64)crush_hash32_4(bucket->h.hash, x, n, r,
+					  bucket->h.id) * (__u64)w;
 		t = t >> 32;
 
 		/* descend to the left or right? */
@@ -224,7 +225,7 @@ static int bucket_straw_choose(struct crush_bucket_straw *bucket,
 	__u64 draw;
 
 	for (i = 0; i < bucket->h.size; i++) {
-		draw = crush_hash32_3(x, bucket->h.items[i], r);
+		draw = crush_hash32_3(bucket->h.hash, x, bucket->h.items[i], r);
 		draw &= 0xffff;
 		draw *= bucket->straws[i];
 		if (i == 0 || draw > high_draw) {
@@ -267,7 +268,8 @@ static int is_out(struct crush_map *map, __u32 *weight, int item, int x)
 		return 0;
 	if (weight[item] == 0)
 		return 1;
-	if ((crush_hash32_2(x, item) & 0xffff) < weight[item])
+	if ((crush_hash32_2(CRUSH_HASH_RJENKINS1, x, item) & 0xffff)
+	    < weight[item])
 		return 0;
 	return 1;
 }

fs/ceph/osdmap.c

@@ -210,7 +210,8 @@ static struct crush_map *crush_decode(void *pbyval, void *end)
 		ceph_decode_need(p, end, 4*sizeof(u32), bad);
 		b->id = ceph_decode_32(p);
 		b->type = ceph_decode_16(p);
-		b->alg = ceph_decode_16(p);
+		b->alg = ceph_decode_8(p);
+		b->hash = ceph_decode_8(p);
 		b->weight = ceph_decode_32(p);
 		b->size = ceph_decode_32(p);