md: don't call ->add_disk unless there is good reason.

Commit 7bfec5f35c68121e7b18

   md/raid5: If there is a spare and a want_replacement device, start replacement.

cause md_check_recovery to call ->add_disk much more often.
Instead of only when the array is degraded, it is now called whenever
md_check_recovery finds anything useful to do, which includes
updating the metadata for clean<->dirty transition.
This causes unnecessary work, and causes info messages from ->add_disk
to be reported much too often.

So refine md_check_recovery to only do any actual recovery checking
(including ->add_disk) if MD_RECOVERY_NEEDED is set.

This fix is suitable for 3.3.y:

Cc: stable@vger.kernel.org
Reported-by: Jan Ceuleers <jan.ceuleers@computer.org>
Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index b572e1e386ce..8beb19c3bb44 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7560,14 +7560,14 @@ void md_check_recovery(struct mddev *mddev)
                  * any transients in the value of "sync_action".
                  */
                 set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
-                clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
                 /* Clear some bits that don't mean anything, but
                  * might be left set
                  */
                 clear_bit(MD_RECOVERY_INTR, &mddev->recovery);
                 clear_bit(MD_RECOVERY_DONE, &mddev->recovery);
 
-                if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
+                if (!test_and_clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery) ||
+                    test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
                         goto unlock;
                 /* no recovery is running.
                  * remove any failed drives, then