md/raid5: resize stripe_head when reshape array

When reshape array, we try to reuse shared pages of old stripe_head,
and allocate more for the new one if needed.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

drivers/md/raid5.c

@@ -2535,6 +2535,12 @@ static int resize_stripes(struct r5conf *conf, int newsize)
 		osh = get_free_stripe(conf, hash);
 		unlock_device_hash_lock(conf, hash);
 
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+	for (i = 0; i < osh->nr_pages; i++) {
+		nsh->pages[i] = osh->pages[i];
+		osh->pages[i] = NULL;
+	}
+#endif
 		for(i=0; i<conf->pool_size; i++) {
 			nsh->dev[i].page = osh->dev[i].page;
 			nsh->dev[i].orig_page = osh->dev[i].page;
@@ -2589,6 +2595,23 @@ static int resize_stripes(struct r5conf *conf, int newsize)
 		nsh = list_entry(newstripes.next, struct stripe_head, lru);
 		list_del_init(&nsh->lru);
 
+#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
+		for (i = 0; i < nsh->nr_pages; i++) {
+			if (nsh->pages[i])
+				continue;
+			nsh->pages[i] = alloc_page(GFP_NOIO);
+			if (!nsh->pages[i])
+				err = -ENOMEM;
+		}
+
+		for (i = conf->raid_disks; i < newsize; i++) {
+			if (nsh->dev[i].page)
+				continue;
+			nsh->dev[i].page = raid5_get_dev_page(nsh, i);
+			nsh->dev[i].orig_page = nsh->dev[i].page;
+			nsh->dev[i].offset = raid5_get_page_offset(nsh, i);
+		}
+#else
 		for (i=conf->raid_disks; i < newsize; i++)
 			if (nsh->dev[i].page == NULL) {
 				struct page *p = alloc_page(GFP_NOIO);
@@ -2598,6 +2621,7 @@ static int resize_stripes(struct r5conf *conf, int newsize)
 				if (!p)
 					err = -ENOMEM;
 			}
+#endif
 		raid5_release_stripe(nsh);
 	}
 	/* critical section pass, GFP_NOIO no longer needed */