LU-1665 libcfs: alignment of hsb_head[0] can be suboptimal

On ia64, hsb_head[0] of struct cfs_hash_bucket could be aligned to a
4-byte boundary.  However, after allocating the hash bucket and
casting, the first member of the struct pointed to by hsb_head[0]
might prefer an 8-byte alignment.  This causes a constant stream
of unaligned access warnings from the kernel.

For other cpus this might waste some small amount of space, but
potentially produces more natural alignments (8 byte objects on 8
byte boundaries).

Signed-off-by: chas williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Change-Id: I4561ab3e6553b5dcef840b8e4e9aa3023b7c3586
Reviewed-on: http://review.whamcloud.com/4965
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Hudson
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>

diff --git a/libcfs/include/libcfs/libcfs_hash.h b/libcfs/include/libcfs/libcfs_hash.h
index 4187d92..ab9d8a8 100644 (file)
--- a/libcfs/include/libcfs/libcfs_hash.h
+++ b/libcfs/include/libcfs/libcfs_hash.h
@@ -149,12 +149,12 @@ typedef union {
  * - some extra bytes (caller can require it while creating hash)
  */
 typedef struct cfs_hash_bucket {
-        cfs_hash_lock_t             hsb_lock;       /**< bucket lock */
-        __u32                       hsb_count;      /**< current entries */
-        __u32                       hsb_version;    /**< change version */
-        unsigned int                hsb_index;      /**< index of bucket */
-        int                         hsb_depmax;     /**< max depth on bucket */
-        char                        hsb_head[0];    /**< hash-head array */
+       cfs_hash_lock_t         hsb_lock;       /**< bucket lock */
+       __u32                   hsb_count;      /**< current entries */
+       __u32                   hsb_version;    /**< change version */
+       unsigned int            hsb_index;      /**< index of bucket */
+       int                     hsb_depmax;     /**< max depth on bucket */
+       long                    hsb_head[0];    /**< hash-head array */
 } cfs_hash_bucket_t;
 
 /**