Btrfs, raid56: fix use-after-free problem in the final device replace procedure on raid56

The commit c404e0dc (Btrfs: fix use-after-free in the finishing
procedure of the device replace) fixed a use-after-free problem
which happened when removing the source device at the end of device
replace, but at that time, btrfs didn't support device replace
on raid56, so we didn't fix the problem on the raid56 profile.
Currently, we implemented device replace for raid56, so we need
kick that problem out before we enable that function for raid56.

The fix method is very simple, we just increase the bio per-cpu
counter before we submit a raid56 io, and decrease the counter
when the raid56 io ends.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 6f662b34ba0e..fa27b4e3b6c8 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -920,9 +920,9 @@ void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
         percpu_counter_inc(&fs_info->bio_counter);
 }
 
-void btrfs_bio_counter_dec(struct btrfs_fs_info *fs_info)
+void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
 {
-        percpu_counter_dec(&fs_info->bio_counter);
+        percpu_counter_sub(&fs_info->bio_counter, amount);
 
         if (waitqueue_active(&fs_info->replace_wait))
                 wake_up(&fs_info->replace_wait);