md: md_stop_writes requires mddev_lock.

As md_stop_writes manipulates the sync_thread and calls md_update_sb,
it need to be called with mddev_lock held.

In all internal cases it is, but the symbol is exported for dm-raid to
call and in that case the lock won't be help.
Do make an exported version which takes the lock, and an internal
version which does not.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 540347c..f43ff29 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4704,7 +4704,7 @@ static void md_clean(mddev_t *mddev)
        mddev->plug = NULL;
 }
 
-void md_stop_writes(mddev_t *mddev)
+static void __md_stop_writes(mddev_t *mddev)
 {
        if (mddev->sync_thread) {
                set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
@@ -4724,6 +4724,13 @@ void md_stop_writes(mddev_t *mddev)
                md_update_sb(mddev, 1);
        }
 }
+
+void md_stop_writes(mddev_t *mddev)
+{
+       mddev_lock(mddev);
+       __md_stop_writes(mddev);
+       mddev_unlock(mddev);
+}
 EXPORT_SYMBOL_GPL(md_stop_writes);
 
 void md_stop(mddev_t *mddev)
@@ -4748,7 +4755,7 @@ static int md_set_readonly(mddev_t *mddev, int is_open)
                goto out;
        }
        if (mddev->pers) {
-               md_stop_writes(mddev);
+               __md_stop_writes(mddev);
 
                err  = -ENXIO;
                if (mddev->ro==1)
@@ -4785,7 +4792,7 @@ static int do_md_stop(mddev_t * mddev, int mode, int is_open)
                if (mddev->ro)
                        set_disk_ro(disk, 0);
 
-               md_stop_writes(mddev);
+               __md_stop_writes(mddev);
                md_stop(mddev);
                mddev->queue->merge_bvec_fn = NULL;
                mddev->queue->unplug_fn = NULL;