md: remove mddev_lock from rdev_attr_show()

No rdev attributes need locking for 'show', though
state_show() might benefit from ensuring it sees a
consistent set of flags.

None even use rdev->mddev, so testing for it isn't really
needed and it certainly doesn't need to be held constant.

So improve state_show() and remove the locking.

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

diff --git a/drivers/md/md.c b/drivers/md/md.c
index dbbe5e6df24cc5235b13d6829a9fdd5e6fba19c7..5438834bf54dc56da84222793a1f723f9afab2f5 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2419,40 +2419,41 @@ state_show(struct md_rdev *rdev, char *page)
 {
        char *sep = "";
        size_t len = 0;
+       unsigned long flags = ACCESS_ONCE(rdev->flags);
 
-       if (test_bit(Faulty, &rdev->flags) ||
+       if (test_bit(Faulty, &flags) ||
            rdev->badblocks.unacked_exist) {
                len+= sprintf(page+len, "%sfaulty",sep);
                sep = ",";
        }
-       if (test_bit(In_sync, &rdev->flags)) {
+       if (test_bit(In_sync, &flags)) {
                len += sprintf(page+len, "%sin_sync",sep);
                sep = ",";
        }
-       if (test_bit(WriteMostly, &rdev->flags)) {
+       if (test_bit(WriteMostly, &flags)) {
                len += sprintf(page+len, "%swrite_mostly",sep);
                sep = ",";
        }
-       if (test_bit(Blocked, &rdev->flags) ||
+       if (test_bit(Blocked, &flags) ||
            (rdev->badblocks.unacked_exist
-            && !test_bit(Faulty, &rdev->flags))) {
+            && !test_bit(Faulty, &flags))) {
                len += sprintf(page+len, "%sblocked", sep);
                sep = ",";
        }
-       if (!test_bit(Faulty, &rdev->flags) &&
-           !test_bit(In_sync, &rdev->flags)) {
+       if (!test_bit(Faulty, &flags) &&
+           !test_bit(In_sync, &flags)) {
                len += sprintf(page+len, "%sspare", sep);
                sep = ",";
        }
-       if (test_bit(WriteErrorSeen, &rdev->flags)) {
+       if (test_bit(WriteErrorSeen, &flags)) {
                len += sprintf(page+len, "%swrite_error", sep);
                sep = ",";
        }
-       if (test_bit(WantReplacement, &rdev->flags)) {
+       if (test_bit(WantReplacement, &flags)) {
                len += sprintf(page+len, "%swant_replacement", sep);
                sep = ",";
        }
-       if (test_bit(Replacement, &rdev->flags)) {
+       if (test_bit(Replacement, &flags)) {
                len += sprintf(page+len, "%sreplacement", sep);
                sep = ",";
        }
@@ -2965,21 +2966,12 @@ rdev_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
 {
        struct rdev_sysfs_entry *entry = container_of(attr, struct rdev_sysfs_entry, attr);
        struct md_rdev *rdev = container_of(kobj, struct md_rdev, kobj);
-       struct mddev *mddev = rdev->mddev;
-       ssize_t rv;
 
        if (!entry->show)
                return -EIO;
-
-       rv = mddev ? mddev_lock(mddev) : -EBUSY;
-       if (!rv) {
-               if (rdev->mddev == NULL)
-                       rv = -EBUSY;
-               else
-                       rv = entry->show(rdev, page);
-               mddev_unlock(mddev);
-       }
-       return rv;
+       if (!rdev->mddev)
+               return -EBUSY;
+       return entry->show(rdev, page);
 }
 
 static ssize_t