md: Change active_io to percpu

Now the type of active_io is atomic. It's used to count how many ios are
in the submitting process and it's added and decreased very time. But it
only needs to check if it's zero when suspending the raid. So we can
switch atomic to percpu to improve the performance.

After switching active_io to percpu type, we use the state of active_io
to judge if the raid device is suspended. And we don't need to wake up
->sb_wait in md_handle_request anymore. It's done in the callback function
which is registered when initing active_io. The argument mddev->suspended
is only used to count how many users are trying to set raid to suspend
state.

Signed-off-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/md/md.h b/drivers/md/md.h
index 554a9026669a..6335cb86e52e 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -315,7 +315,7 @@ struct mddev {
 	unsigned long			sb_flags;
 
 	int				suspended;
-	atomic_t			active_io;
+	struct percpu_ref		active_io;
 	int				ro;
 	int				sysfs_active; /* set when sysfs deletes
 						       * are happening, so run/