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>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ecd016f7dab15caf1a5894479c094fc0734d9bbe..e490cfd70bbaab0b15876b6ac5a502a66108bb02 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3378,6 +3378,7 @@ void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
                              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,

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index ba39f6969a7232251cc077a264f79075c53a4ddd..0238801e6408af1d4e3aa7ce1923dac2f533f902 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -9,6 +9,7 @@
 #include <linux/blkdev.h>
 #include <linux/rbtree.h>
 #include <linux/slab.h>
+#include <linux/error-injection.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -3314,6 +3315,15 @@ int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
        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);
+}
+ALLOW_ERROR_INJECTION(btrfs_should_cancel_balance, TRUE);
+
 static int relocate_file_extent_cluster(struct inode *inode,
                                        struct file_extent_cluster *cluster)
 {

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 74c34c388098d523274f9acd98066d6bbef081e3..c1909e5f4506835f7741c5003c51ac65982a3a29 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3994,7 +3994,7 @@ int btrfs_balance(struct btrfs_fs_info *fs_info,
 
        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;
        }