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>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 540347c538f9..f43ff2962b2b 100644
--- 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;