[PATCH] md: Allow stripes to be expanded in preparation for expanding an array

Before a RAID-5 can be expanded, we need to be able to expand the stripe-cache
data structure.

This requires allocating new stripes in a new kmem_cache.  If this succeeds,
we copy cache pages over and release the old stripes and kmem_cache.

We then allocate new pages.  If that fails, we leave the stripe cache at it's
new size.  It isn't worth the effort to shrink it back again.

Unfortuanately this means we need two kmem_cache names as we, for a short
period of time, we have two kmem_caches.  So they are raid5/%s and
raid5/%s-alt

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 94dbdd406f12..b7b2653af7bb 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -216,7 +216,11 @@ struct raid5_private_data {
         struct list_head        bitmap_list; /* stripes delaying awaiting bitmap update */
         atomic_t                preread_active_stripes; /* stripes with scheduled io */
 
-        char                    cache_name[20];
+        /* unfortunately we need two cache names as we temporarily have
+         * two caches.
+         */
+        int                     active_name;
+        char                    cache_name[2][20];
         kmem_cache_t            *slab_cache; /* for allocating stripes */
 
         int                     seq_flush, seq_write;
@@ -238,7 +242,8 @@ struct raid5_private_data {
         wait_queue_head_t       wait_for_overlap;
         int                     inactive_blocked;       /* release of inactive stripes blocked,
                                                          * waiting for 25% to be free
-                                                         */        
+                                                         */
+        int                     pool_size; /* number of disks in stripeheads in pool */
         spinlock_t              device_lock;
         struct disk_info        *disks;
 };