bufferhead: revert constructor removal

The constructor for buffer_head slabs was removed recently.  We need the
constructor back in slab defrag in order to insure that slab objects always
have a definite state even before we allocated them.

I think we mistakenly merged the removal of the constuctor into a cleanup
patch.  You (ie: akpm) had a test that showed that the removal of the
constructor led to a small regression.  The prior state makes things easier
for slab defrag.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 3 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 1de921484eac..826baf4f04bc 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3153,7 +3153,7 @@ static void recalc_bh_state(void)
         
 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
 {
-        struct buffer_head *ret = kmem_cache_zalloc(bh_cachep,
+        struct buffer_head *ret = kmem_cache_alloc(bh_cachep,
                                 set_migrateflags(gfp_flags, __GFP_RECLAIMABLE));
         if (ret) {
                 INIT_LIST_HEAD(&ret->b_assoc_buffers);
@@ -3241,12 +3241,24 @@ int bh_submit_read(struct buffer_head *bh)
 }
 EXPORT_SYMBOL(bh_submit_read);
 
+static void
+init_buffer_head(struct kmem_cache *cachep, void *data)
+{
+        struct buffer_head *bh = data;
+
+        memset(bh, 0, sizeof(*bh));
+        INIT_LIST_HEAD(&bh->b_assoc_buffers);
+}
+
 void __init buffer_init(void)
 {
         int nrpages;
 
-        bh_cachep = KMEM_CACHE(buffer_head,
-                        SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
+        bh_cachep = kmem_cache_create("buffer_head",
+                        sizeof(struct buffer_head), 0,
+                                (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
+                                SLAB_MEM_SPREAD),
+                                init_buffer_head);
 
         /*
          * Limit the bh occupancy to 10% of ZONE_NORMAL