linux-kernel - [ 32/62] md: dont call ->add_disk unless there is good reason.

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Message-Id: <20120424223244.701664774@linuxfoundation.org>
Date:	Tue, 24 Apr 2012 15:33:13 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jan Ceuleers <jan.ceuleers@...puter.org>,
	NeilBrown <neilb@...e.de>
Subject: [ 32/62] md: dont call ->add_disk unless there is good reason.

3.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: NeilBrown <neilb@...e.de>

commit ed209584c38fb74b7eecc03e5b1bfe674e591bd8 upstream.

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:

Reported-by: Jan Ceuleers <jan.ceuleers@...puter.org>
Signed-off-by: NeilBrown <neilb@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/md.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7580,14 +7580,14 @@ void md_check_recovery(struct mddev *mdd
 		 * 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


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