Ack: [PATCH 1/1] UBUNTU: SAUCE: md: fix possible corruption of array metadata on shutdown.

[Seth Forshee]

On Mon, Apr 30, 2012 at 05:46:26PM +0100, Luis Henriques wrote:
> From: NeilBrown <neilb at suse.de>
> 
> BugLink: http://bugs.launchpad.net/bugs/992038
> 
> commit c744a65c1e2d59acc54333ce8
>   md: don't set md arrays to readonly on shutdown.
> 
> removed the possibility of a 'BUG' when data is written to an array
> that has just been switched to read-only, but also introduced the
> possibility that the array metadata could be corrupted.
> 
> If, when md_notify_reboot gets the mddev lock, the array is
> in a state where it is assembled but hasn't been started (as can
> happen if the personality module is not available, or in other unusual
> situations), then incorrect metadata will be written out making it
> impossible to re-assemble the array.
> 
> So only call __md_stop_writes() if the array has actually been
> activated.
> 
> This patch is needed for any stable kernel which has had the above
> commit applied.
> 
> Cc: stable at vger.kernel.org
> Reported-by: Christoph Nelles <evilazrael at evilazrael.de>
> Signed-off-by: NeilBrown <neilb at suse.de>
> (cherry picked from commit 30b8aa9172dfeaac6d77897c67ee9f9fc574cdbb)
> 
> Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
> ---
>  drivers/md/md.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 6f37aa4..065ab4f 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8100,7 +8100,8 @@ static int md_notify_reboot(struct notifier_block *this,
>  
>  	for_each_mddev(mddev, tmp) {
>  		if (mddev_trylock(mddev)) {
> -			__md_stop_writes(mddev);
> +			if (mddev->pers)
> +				__md_stop_writes(mddev);
>  			mddev->safemode = 2;
>  			mddev_unlock(mddev);
>  		}
> -- 
> 1.7.9.5
> 
> 
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