md: remove mddev_lock() from md_attr_show()

Most attributes can be read safely without any locking.
A race might lead to a slightly out-dated value, but nothing wrong.

We already have locking in some places where needed.
All that remains is can_clear_show(), behind_writes_used_show()
and action_show() which are easily fixed.

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

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 3424b1915fc4..3a5767968ba0 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -2211,11 +2211,13 @@ __ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store);
 static ssize_t can_clear_show(struct mddev *mddev, char *page)
 {
         int len;
+        spin_lock(&mddev->lock);
         if (mddev->bitmap)
                 len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?
                                              "false" : "true"));
         else
                 len = sprintf(page, "\n");
+        spin_unlock(&mddev->lock);
         return len;
 }
 
@@ -2240,10 +2242,15 @@ __ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store);
 static ssize_t
 behind_writes_used_show(struct mddev *mddev, char *page)
 {
+        ssize_t ret;
+        spin_lock(&mddev->lock);
         if (mddev->bitmap == NULL)
-                return sprintf(page, "0\n");
-        return sprintf(page, "%lu\n",
-                       mddev->bitmap->behind_writes_used);
+                ret = sprintf(page, "0\n");
+        else
+                ret = sprintf(page, "%lu\n",
+                              mddev->bitmap->behind_writes_used);
+        spin_unlock(&mddev->lock);
+        return ret;
 }
 
 static ssize_t