From 726a342120eba8197b3bc5e01af1bd2dbf80f77f Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Mon, 17 Feb 2020 14:16:52 +0800
Patch-mainline: v5.7-rc1
Git-commit: 726a342120eba8197b3bc5e01af1bd2dbf80f77f
References: bsc#1171417
Subject: [PATCH 1/3] btrfs: relocation: add error injection points for
 cancelling balance

Introduce a new error injection point, should_cancel_balance().

It's just a wrapper of atomic_read(&fs_info->balance_cancel_req), but
allows us to override the return value.

Currently there are only one locations using this function:

- btrfs_balance()
  It checks cancel before each block group.

There are other locations checking fs_info->balance_cancel_req, but they
are not used as an indicator to exit, so there is no need to use the
wrapper.

But there will be more locations coming, and some locations can cause
kernel panic if not handled properly.  So introduce this error injection
to provide better test interface.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/ctree.h      |    1 +
 fs/btrfs/relocation.c |    8 ++++++++
 fs/btrfs/volumes.c    |    2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3471,6 +3471,7 @@ void btrfs_reloc_pre_snapshot(struct btr
 			      u64 *bytes_to_reserve);
 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
 			      struct btrfs_pending_snapshot *pending);
+int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info);
 
 /* scrub.c */
 int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3311,6 +3311,14 @@ int setup_extent_mapping(struct inode *i
 	return ret;
 }
 
+/*
+ * Allow error injection to test balance cancellation
+ */
+int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info)
+{
+	return atomic_read(&fs_info->balance_cancel_req);
+}
+
 static int relocate_file_extent_cluster(struct inode *inode,
 					struct file_extent_cluster *cluster)
 {
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3864,7 +3864,7 @@ int btrfs_balance(struct btrfs_balance_c
 
 	if (btrfs_fs_closing(fs_info) ||
 	    atomic_read(&fs_info->balance_pause_req) ||
-	    atomic_read(&fs_info->balance_cancel_req)) {
+	    btrfs_should_cancel_balance(fs_info)) {
 		ret = -EINVAL;
 		goto out;
 	}