f2fs: fix to drop all dirty pages during umount() if cp_error is set

xfstest generic/361 reports a bug as below:

f2fs_bug_on(sbi, sbi->fsync_node_num);

kernel BUG at fs/f2fs/super.c:1627!
RIP: 0010:f2fs_put_super+0x3a8/0x3b0
Call Trace:
 generic_shutdown_super+0x8c/0x1b0
 kill_block_super+0x2b/0x60
 kill_f2fs_super+0x87/0x110
 deactivate_locked_super+0x39/0x80
 deactivate_super+0x46/0x50
 cleanup_mnt+0x109/0x170
 __cleanup_mnt+0x16/0x20
 task_work_run+0x65/0xa0
 exit_to_user_mode_prepare+0x175/0x190
 syscall_exit_to_user_mode+0x25/0x50
 do_syscall_64+0x4c/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc

During umount(), if cp_error is set, f2fs_wait_on_all_pages() should
not stop waiting all F2FS_WB_CP_DATA pages to be writebacked, otherwise,
fsync_node_num can be non-zero after f2fs_wait_on_all_pages() causing
this bug.

In this case, to avoid deadloop in f2fs_wait_on_all_pages(), it needs
to drop all dirty pages rather than redirtying them.
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/checkpoint.c

@@ -325,8 +325,15 @@ static int __f2fs_write_meta_page(struct page *page,
 
 	trace_f2fs_writepage(page, META);
 
-	if (unlikely(f2fs_cp_error(sbi)))
+	if (unlikely(f2fs_cp_error(sbi))) {
+		if (is_sbi_flag_set(sbi, SBI_IS_CLOSE)) {
+			ClearPageUptodate(page);
+			dec_page_count(sbi, F2FS_DIRTY_META);
+			unlock_page(page);
+			return 0;
+		}
 		goto redirty_out;
+	}
 	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
 		goto redirty_out;
 	if (wbc->for_reclaim && page->index < GET_SUM_BLOCK(sbi, 0))
@@ -1306,7 +1313,8 @@ void f2fs_wait_on_all_pages(struct f2fs_sb_info *sbi, int type)
 		if (!get_pages(sbi, type))
 			break;
 
-		if (unlikely(f2fs_cp_error(sbi)))
+		if (unlikely(f2fs_cp_error(sbi) &&
+			!is_sbi_flag_set(sbi, SBI_IS_CLOSE)))
 			break;
 
 		if (type == F2FS_DIRTY_META)

fs/f2fs/data.c

@@ -2800,7 +2800,8 @@ int f2fs_write_single_data_page(struct page *page, int *submitted,
 		 * don't drop any dirty dentry pages for keeping lastest
 		 * directory structure.
 		 */
-		if (S_ISDIR(inode->i_mode))
+		if (S_ISDIR(inode->i_mode) &&
+				!is_sbi_flag_set(sbi, SBI_IS_CLOSE))
 			goto redirty_out;
 		goto out;
 	}