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>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 2bc56e2a3526..135a0907e9de 100644
--- 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);