[PATCH v5 08/16] md/raid5: resize stripes and set correct offset when reshape array

[Yufen Yu <yuyufen@huawei.com>]

When reshape array, we try to reuse shared pages of old stripe_head,
and allocate more for the new one if needed. At the same time, set
correct offset when call handle_stripe_expansion().

By the way, we call resize_stripes() only when grow raid array disks,
so that don't worry about memleak for old r5pages.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
 drivers/md/raid5.c | 51 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 44 insertions(+), 7 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e554d073113b..689a36c8e723 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2493,10 +2493,20 @@ static int resize_stripes(struct r5conf *conf, int newsize)
 		osh = get_free_stripe(conf, hash);
 		unlock_device_hash_lock(conf, hash);
 
-		for(i=0; i<conf->pool_size; i++) {
+		if (raid5_stripe_pages_shared(conf)) {
+			/* We reuse pages in r5pages of old stripe head */
+			for (i = 0; i < osh->pages.size; i++) {
+				nsh->pages.page[i] = osh->pages.page[i];
+				osh->pages.page[i] = NULL;
+			}
+		}
+
+		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;
+			nsh->dev[i].offset = osh->dev[i].offset;
 		}
+
 		nsh->hash_lock_index = hash;
 		free_stripe(conf->slab_cache, osh);
 		cnt++;
@@ -2543,17 +2553,42 @@ static int resize_stripes(struct r5conf *conf, int newsize)
 
 	/* Step 4, return new stripes to service */
 	while(!list_empty(&newstripes)) {
+		struct page *p;
+		unsigned int offset;
 		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;
-				nsh->dev[i].orig_page = p;
+		/*
+		 * If we use r5pages, means, pages.size is not zero,
+		 * allocate pages it needed for new stripe_head.
+		 */
+		for (i = 0; i < nsh->pages.size; i++) {
+			if (nsh->pages.page[i] == NULL) {
+				p = alloc_page(GFP_NOIO);
+				if (!p)
+					err = -ENOMEM;
+				nsh->pages.page[i] = p;
+			}
+		}
+
+		for (i = conf->raid_disks; i < newsize; i++) {
+			if (nsh->dev[i].page)
+				continue;
+
+			if (raid5_stripe_pages_shared(conf)) {
+				p = raid5_get_dev_page(nsh, i);
+				offset = raid5_get_page_offset(nsh, i);
+			} else {
+				p = alloc_page(GFP_NOIO);
 				if (!p)
 					err = -ENOMEM;
+				offset = 0;
 			}
+
+			nsh->dev[i].page = p;
+			nsh->dev[i].orig_page = p;
+			nsh->dev[i].offset = offset;
+		}
 		raid5_release_stripe(nsh);
 	}
 	/* critical section pass, GFP_NOIO no longer needed */
@@ -4476,7 +4511,9 @@ static void handle_stripe_expansion(struct r5conf *conf, struct stripe_head *sh)
 			/* place all the copies on one channel */
 			init_async_submit(&submit, 0, tx, NULL, NULL, NULL);
 			tx = async_memcpy(sh2->dev[dd_idx].page,
-					  sh->dev[i].page, 0, 0,
+					  sh->dev[i].page,
+					  sh2->dev[dd_idx].offset,
+					  sh->dev[i].offset,
 					  conf->stripe_size,
 					  &submit);
 
-- 
2.25.4