[PATCH] afs: Fix double add page to memcg when afs_readpages

[Zhang Xiaoxu]

Since commit 3fea5a499d57 ("mm: memcontrol: convert page cache to a new
mem_cgroup_charge() API") not uncharge the page, the page maybe double
add to memcg, then VM_BUG_ON_PAGE in commit_charge because the page's
memcg not NULL.

So, if add page cache failed, stop the read pages and let caller to
free the pages.

Reported-by: Hulk Robot <hulkci at huawei.com>
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5 at huawei.com>
---
 fs/afs/file.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 6f6ed1605cfe..aea73e9520d1 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -448,7 +448,7 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 	struct page *first, *page;
 	struct key *key = afs_file_key(file);
 	pgoff_t index;
-	int ret, n, i;
+	int ret, n, i, err;
 
 	/* Count the number of contiguous pages at the front of the list.  Note
 	 * that the list goes prev-wards rather than next-wards.
@@ -488,8 +488,9 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 		page = lru_to_page(pages);
 		list_del(&page->lru);
 		index = page->index;
-		if (add_to_page_cache_lru(page, mapping, index,
-					  readahead_gfp_mask(mapping))) {
+		err = add_to_page_cache_lru(page, mapping, index,
+					    readahead_gfp_mask(mapping));
+		if (err) {
 #ifdef CONFIG_AFS_FSCACHE
 			fscache_uncache_page(vnode->cache, page);
 #endif
@@ -503,7 +504,7 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 
 	if (req->nr_pages == 0) {
 		kfree(req);
-		return 0;
+		return err;
 	}
 
 	ret = afs_fetch_data(vnode, key, req);
@@ -512,7 +513,7 @@ static int afs_readpages_one(struct file *file, struct address_space *mapping,
 
 	task_io_account_read(PAGE_SIZE * req->nr_pages);
 	afs_put_read(req);
-	return 0;
+	return err;
 
 error:
 	if (ret == -ENOENT) {
-- 
2.25.4