f2fs: retry to revoke atomic commit in -ENOMEM case

During atomic committing, if we encounter -ENOMEM in revoke path, it's
better to give a chance to retry revoking.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -213,9 +213,15 @@ static int __revoke_inmem_pages(struct inode *inode,
 			struct node_info ni;
 
 			trace_f2fs_commit_inmem_page(page, INMEM_REVOKE);
-
+retry:
 			set_new_dnode(&dn, inode, NULL, NULL, 0);
-			if (get_dnode_of_data(&dn, page->index, LOOKUP_NODE)) {
+			err = get_dnode_of_data(&dn, page->index, LOOKUP_NODE);
+			if (err) {
+				if (err == -ENOMEM) {
+					congestion_wait(BLK_RW_ASYNC, HZ/50);
+					cond_resched();
+					goto retry;
+				}
 				err = -EAGAIN;
 				goto next;
 			}