LU-4974 lod: use common hash function for OST pool

Use the common djb2 hash function for OST pool lookup.  This is used
for string-based hashing in other parts of the code.  It doesn't make
sense to have a custom hash function just for OST pool lookup, since
there aren't expected to be a huge number of pools and there is no
expectation that one of these functions is better than the other.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I501a42bc169243204dfc847c0388240fc2500c1e
Reviewed-on: http://review.whamcloud.com/10243
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/lod/lod_pool.c b/lustre/lod/lod_pool.c
index 6eaa6d7..1404073 100644 (file)
--- a/lustre/lod/lod_pool.c
+++ b/lustre/lod/lod_pool.c
@@ -132,11 +132,7 @@ static void pool_putref_locked(struct pool_desc *pool)
 /**
  * Hash the pool name for use by the cfs_hash handlers.
  *
 /**
  * Hash the pool name for use by the cfs_hash handlers.
  *

- * hash function using a Rotating Hash algorithm
- * Knuth, D. The Art of Computer Programming,
- * Volume 3: Sorting and Searching,
- * Chapter 6.4.
- * Addison Wesley, 1973
+ * Use the standard DJB2 hash function for ASCII strings in Lustre.

  *
  * \param[in] hash_body        hash structure where this key is embedded (unused)
  * \param[in] key      key to be hashed (in this case the pool name)
  *
  * \param[in] hash_body        hash structure where this key is embedded (unused)
  * \param[in] key      key to be hashed (in this case the pool name)


@@ -146,18 +142,7 @@ static void pool_putref_locked(struct pool_desc *pool)
  */
 static __u32 pool_hashfn(cfs_hash_t *hash_body, const void *key, unsigned mask)
 {
  */
 static __u32 pool_hashfn(cfs_hash_t *hash_body, const void *key, unsigned mask)
 {

-       int i;
-       __u32 result;
-       char *poolname;
-
-       result = 0;
-       poolname = (char *)key;
-       for (i = 0; i < LOV_MAXPOOLNAME; i++) {
-               if (poolname[i] == '\0')
-                       break;
-               result = (result << 4) ^ (result >> 28) ^ poolname[i];
-       }
-       return result % mask;
+       return cfs_hash_djb2_hash(key, strnlen(key, LOV_MAXPOOLNAME), mask);

 }
 
 /**
 }
 
 /**