f2fs: fix to commit bio cache after flushing node pages

In sync_node_pages, we won't check and commit last merged pages in private
bio cache of f2fs, as these pages were taged as writeback, someone who is
waiting for writebacking of the page will be blocked until the cache was
committed by someone else.

We need to commit node type bio cache to avoid potential deadlock or long
delay of waiting writeback.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -1312,6 +1312,7 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
 	struct page *last_page = NULL;
 	bool marked = false;
 	nid_t ino = inode->i_ino;
+	int nwritten = 0;
 
 	if (atomic) {
 		last_page = last_fsync_dnode(sbi, ino);
@@ -1385,7 +1386,10 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
 				unlock_page(page);
 				f2fs_put_page(last_page, 0);
 				break;
+			} else {
+				nwritten++;
 			}
+
 			if (page == last_page) {
 				f2fs_put_page(page, 0);
 				marked = true;
@@ -1407,6 +1411,9 @@ int fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
 		unlock_page(last_page);
 		goto retry;
 	}
+
+	if (nwritten)
+		f2fs_submit_merged_bio_cond(sbi, NULL, NULL, ino, NODE, WRITE);
 	return ret ? -EIO: 0;
 }
 
@@ -1416,6 +1423,7 @@ int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc)
 	struct pagevec pvec;
 	int step = 0;
 	int nwritten = 0;
+	int ret = 0;
 
 	pagevec_init(&pvec, 0);
 
@@ -1436,7 +1444,8 @@ int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc)
 
 			if (unlikely(f2fs_cp_error(sbi))) {
 				pagevec_release(&pvec);
-				return -EIO;
+				ret = -EIO;
+				goto out;
 			}
 
 			/*
@@ -1487,6 +1496,8 @@ int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc)
 
 			if (NODE_MAPPING(sbi)->a_ops->writepage(page, wbc))
 				unlock_page(page);
+			else
+				nwritten++;
 
 			if (--wbc->nr_to_write == 0)
 				break;
@@ -1504,7 +1515,10 @@ int sync_node_pages(struct f2fs_sb_info *sbi, struct writeback_control *wbc)
 		step++;
 		goto next_step;
 	}
-	return nwritten;
+out:
+	if (nwritten)
+		f2fs_submit_merged_bio(sbi, NODE, WRITE);
+	return ret;
 }
 
 int wait_on_node_pages_writeback(struct f2fs_sb_info *sbi, nid_t ino)