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>

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 3424b19..3a57679 100644 (file)
--- 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

diff --git a/drivers/md/md.c b/drivers/md/md.c
index eb0c3b5..dbbe5e6 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4042,20 +4042,21 @@ static ssize_t
 action_show(struct mddev *mddev, char *page)
 {
        char *type = "idle";
-       if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
+       unsigned long recovery = mddev->recovery;
+       if (test_bit(MD_RECOVERY_FROZEN, &recovery))
                type = "frozen";
-       else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
-           (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {
-               if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
+       else if (test_bit(MD_RECOVERY_RUNNING, &recovery) ||
+           (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &recovery))) {
+               if (test_bit(MD_RECOVERY_RESHAPE, &recovery))
                        type = "reshape";
-               else if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
-                       if (!test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
+               else if (test_bit(MD_RECOVERY_SYNC, &recovery)) {
+                       if (!test_bit(MD_RECOVERY_REQUESTED, &recovery))
                                type = "resync";
-                       else if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
+                       else if (test_bit(MD_RECOVERY_CHECK, &recovery))
                                type = "check";
                        else
                                type = "repair";
-               } else if (test_bit(MD_RECOVERY_RECOVER, &mddev->recovery))
+               } else if (test_bit(MD_RECOVERY_RECOVER, &recovery))
                        type = "recover";
        }
        return sprintf(page, "%s\n", type);
@@ -4572,11 +4573,7 @@ md_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
        mddev_get(mddev);
        spin_unlock(&all_mddevs_lock);
 
-       rv = mddev_lock(mddev);
-       if (!rv) {
-               rv = entry->show(mddev, page);
-               mddev_unlock(mddev);
-       }
+       rv = entry->show(mddev, page);
        mddev_put(mddev);
        return rv;
 }