[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>
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 94dbdd4..b7b2653 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -216,7 +216,11 @@
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 @@
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;
};