f2fs: fix to drop all dirty meta/node pages during umount()

For cp error case, there will be dirty meta/node pages remained after
f2fs_write_checkpoint() in f2fs_put_super(), drop them explicitly, and
do sanity check on reference count of dirty pages and inflight IOs.
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/super.c

@@ -1571,6 +1571,7 @@ static void f2fs_put_super(struct super_block *sb)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(sb);
 	int i;
+	int err = 0;
 	bool done;
 
 	/* unregister procfs/sysfs entries in advance to avoid race case */
@@ -1597,7 +1598,7 @@ static void f2fs_put_super(struct super_block *sb)
 		struct cp_control cpc = {
 			.reason = CP_UMOUNT,
 		};
-		f2fs_write_checkpoint(sbi, &cpc);
+		err = f2fs_write_checkpoint(sbi, &cpc);
 	}
 
 	/* be sure to wait for any on-going discard commands */
@@ -1606,7 +1607,7 @@ static void f2fs_put_super(struct super_block *sb)
 		struct cp_control cpc = {
 			.reason = CP_UMOUNT | CP_TRIMMED,
 		};
-		f2fs_write_checkpoint(sbi, &cpc);
+		err = f2fs_write_checkpoint(sbi, &cpc);
 	}
 
 	/*
@@ -1623,6 +1624,19 @@ static void f2fs_put_super(struct super_block *sb)
 
 	f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA);
 
+	if (err) {
+		truncate_inode_pages_final(NODE_MAPPING(sbi));
+		truncate_inode_pages_final(META_MAPPING(sbi));
+	}
+
+	for (i = 0; i < NR_COUNT_TYPE; i++) {
+		if (!get_pages(sbi, i))
+			continue;
+		f2fs_err(sbi, "detect filesystem reference count leak during "
+			"umount, type: %d, count: %lld", i, get_pages(sbi, i));
+		f2fs_bug_on(sbi, 1);
+	}
+
 	f2fs_bug_on(sbi, sbi->fsync_node_num);
 
 	f2fs_destroy_compress_inode(sbi);