1 files changed, 127 insertions, 4 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 03f31379cebb..6c20b44509d8 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -313,20 +313,143 @@ static int grow_stripes(raid5_conf_t *conf, int num)
         kmem_cache_t *sc;
         int devs = conf->raid_disks;
 
-        sprintf(conf->cache_name, "raid5/%s", mdname(conf->mddev));
-
-        sc = kmem_cache_create(conf->cache_name, 
+        sprintf(conf->cache_name[0], "raid5/%s", mdname(conf->mddev));
+        sprintf(conf->cache_name[1], "raid5/%s-alt", mdname(conf->mddev));
+        conf->active_name = 0;
+        sc = kmem_cache_create(conf->cache_name[conf->active_name],
                                sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
                                0, 0, NULL, NULL);
         if (!sc)
                 return 1;
         conf->slab_cache = sc;
+        conf->pool_size = devs;
         while (num--) {
                 if (!grow_one_stripe(conf))
                         return 1;
         }
         return 0;
 }
+static int resize_stripes(raid5_conf_t *conf, int newsize)
+{
+        /* Make all the stripes able to hold 'newsize' devices.
+         * New slots in each stripe get 'page' set to a new page.
+         *
+         * This happens in stages:
+         * 1/ create a new kmem_cache and allocate the required number of
+         *    stripe_heads.
+         * 2/ gather all the old stripe_heads and tranfer the pages across
+         *    to the new stripe_heads.  This will have the side effect of
+         *    freezing the array as once all stripe_heads have been collected,
+         *    no IO will be possible.  Old stripe heads are freed once their
+         *    pages have been transferred over, and the old kmem_cache is
+         *    freed when all stripes are done.
+         * 3/ reallocate conf->disks to be suitable bigger.  If this fails,
+         *    we simple return a failre status - no need to clean anything up.
+         * 4/ allocate new pages for the new slots in the new stripe_heads.
+         *    If this fails, we don't bother trying the shrink the
+         *    stripe_heads down again, we just leave them as they are.
+         *    As each stripe_head is processed the new one is released into
+         *    active service.
+         *
+         * Once step2 is started, we cannot afford to wait for a write,
+         * so we use GFP_NOIO allocations.
+         */
+        struct stripe_head *osh, *nsh;
+        LIST_HEAD(newstripes);
+        struct disk_info *ndisks;
+        int err = 0;
+        kmem_cache_t *sc;
+        int i;
+
+        if (newsize <= conf->pool_size)
+                return 0; /* never bother to shrink */
+
+        /* Step 1 */
+        sc = kmem_cache_create(conf->cache_name[1-conf->active_name],
+                               sizeof(struct stripe_head)+(newsize-1)*sizeof(struct r5dev),
+                               0, 0, NULL, NULL);
+        if (!sc)
+                return -ENOMEM;
+
+        for (i = conf->max_nr_stripes; i; i--) {
+                nsh = kmem_cache_alloc(sc, GFP_KERNEL);
+                if (!nsh)
+                        break;
+
+                memset(nsh, 0, sizeof(*nsh) + (newsize-1)*sizeof(struct r5dev));
+
+                nsh->raid_conf = conf;
+                spin_lock_init(&nsh->lock);
+
+                list_add(&nsh->lru, &newstripes);
+        }
+        if (i) {
+                /* didn't get enough, give up */
+                while (!list_empty(&newstripes)) {
+                        nsh = list_entry(newstripes.next, struct stripe_head, lru);
+                        list_del(&nsh->lru);
+                        kmem_cache_free(sc, nsh);
+                }
+                kmem_cache_destroy(sc);
+                return -ENOMEM;
+        }
+        /* Step 2 - Must use GFP_NOIO now.
+         * OK, we have enough stripes, start collecting inactive
+         * stripes and copying them over
+         */
+        list_for_each_entry(nsh, &newstripes, lru) {
+                spin_lock_irq(&conf->device_lock);
+                wait_event_lock_irq(conf->wait_for_stripe,
+                                    !list_empty(&conf->inactive_list),
+                                    conf->device_lock,
+                                    unplug_slaves(conf->mddev);
+                        );
+                osh = get_free_stripe(conf);
+                spin_unlock_irq(&conf->device_lock);
+                atomic_set(&nsh->count, 1);
+                for(i=0; i<conf->pool_size; i++)
+                        nsh->dev[i].page = osh->dev[i].page;
+                for( ; i<newsize; i++)
+                        nsh->dev[i].page = NULL;
+                kmem_cache_free(conf->slab_cache, osh);
+        }
+        kmem_cache_destroy(conf->slab_cache);
+
+        /* Step 3.
+         * At this point, we are holding all the stripes so the array
+         * is completely stalled, so now is a good time to resize
+         * conf->disks.
+         */
+        ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
+        if (ndisks) {
+                for (i=0; i<conf->raid_disks; i++)
+                        ndisks[i] = conf->disks[i];
+                kfree(conf->disks);
+                conf->disks = ndisks;
+        } else
+                err = -ENOMEM;
+
+        /* Step 4, return new stripes to service */
+        while(!list_empty(&newstripes)) {
+                nsh = list_entry(newstripes.next, struct stripe_head, lru);
+                list_del_init(&nsh->lru);
+                for (i=conf->raid_disks; i < newsize; i++)
+                        if (nsh->dev[i].page == NULL) {
+                                struct page *p = alloc_page(GFP_NOIO);
+                                nsh->dev[i].page = p;
+                                if (!p)
+                                        err = -ENOMEM;
+                        }
+                release_stripe(nsh);
+        }
+        /* critical section pass, GFP_NOIO no longer needed */
+
+        conf->slab_cache = sc;
+        conf->active_name = 1-conf->active_name;
+        conf->pool_size = newsize;
+        return err;
+}
+
 
 static int drop_one_stripe(raid5_conf_t *conf)
 {
@@ -339,7 +462,7 @@ static int drop_one_stripe(raid5_conf_t *conf)
                 return 0;
         if (atomic_read(&sh->count))
                 BUG();
-        shrink_buffers(sh, conf->raid_disks);
+        shrink_buffers(sh, conf->pool_size);
         kmem_cache_free(conf->slab_cache, sh);
         atomic_dec(&conf->active_stripes);
         return 1;