md/bitmap: remove rcu annotation from pointer arithmetic.

Evaluating  "&mddev->disks" is simple pointer arithmetic, so
it does not need 'rcu' annotations - no dereferencing is happening.

Also enhance the comment to explain that 'rdev' in that case
is not actually a pointer to an rdev.

Reported-by: Patrick Marlier <patrick.marlier@gmail.com>
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 2bc56e2a35262141859f8da21d09a54dec852e52..135a0907e9de413d140e9fb9b793a91b638a1606 100644 (file)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -177,11 +177,16 @@ static struct md_rdev *next_active_rdev(struct md_rdev *rdev, struct mddev *mdde
         * nr_pending is 0 and In_sync is clear, the entries we return will
         * still be in the same position on the list when we re-enter
         * list_for_each_entry_continue_rcu.
+        *
+        * Note that if entered with 'rdev == NULL' to start at the
+        * beginning, we temporarily assign 'rdev' to an address which
+        * isn't really an rdev, but which can be used by
+        * list_for_each_entry_continue_rcu() to find the first entry.
         */
        rcu_read_lock();
        if (rdev == NULL)
                /* start at the beginning */
-               rdev = list_entry_rcu(&mddev->disks, struct md_rdev, same_set);
+               rdev = list_entry(&mddev->disks, struct md_rdev, same_set);
        else {
                /* release the previous rdev and start from there. */
                rdev_dec_pending(rdev, mddev);