linux-kernel - Re: [ 024/167] [PATCH] md: dont call ->add

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Date:	Wed, 9 May 2012 01:57:17 -0500
From:	Jonathan Nieder <jrnieder@...il.com>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, NeilBrown <neilb@...e.de>,
	Jan Ceuleers <jan.ceuleers@...puter.org>
Subject: Re: [ 024/167] [PATCH] md: dont call ->add_disk unless there is good
 reason.

Hi,

Ben Hutchings wrote:

> 3.2-stable review patch.  If anyone has any objections, please let me know.
[...]
> 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.

Does 3.2.y need this?  Commit 7bfec5f35c68121e7b18 (aka v3.3-rc3~3^2~22)
does not seem to be part of the 3.2-stable tree.

Jonathan

> 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: Ben Hutchings <ben@...adent.org.uk>
> ---
>  drivers/md/md.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index b572e1e..8beb19c 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
--
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