linux-kernel - Re: [PATCH] raid0: Set discard_granularity to correct value after reshape.

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Message-ID: <20131107133838.742d83b1@notabene.brown>
Date:	Thu, 7 Nov 2013 13:38:38 +1100
From:	NeilBrown <neilb@...e.de>
To:	"Baldysiak, Pawel" <pawel.baldysiak@...el.com>
Cc:	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
	"shli@...nel.org" <shli@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] raid0: Set discard_granularity to correct value after
 reshape.

On Tue, 5 Nov 2013 14:25:19 +0000 "Baldysiak, Pawel"
<pawel.baldysiak@...el.com> wrote:

> On Thursday, October 31, 2013 1:16 AM NeilBrown <neilb@...e.de> wrote:
> > On Wed, 30 Oct 2013 13:20:22 +0100 Pawel Baldysiak
> > <pawel.baldysiak@...el.com> wrote:
> > 
> > > In case of reshape of raid0 through raid4 a value of
> > > discard_granularity will be set to stripe size. MD driver should
> > > re-set this value to correct one when migration will be finished.
> > > Otherwise array will be left with wrong value and discard operations will not
> > work properly.
> > >
> > > Signed-off-by: Pawel Baldysiak <pawel.baldysiak@...el.com>
> > > Cc: Shaohua Li <shli@...nel.org>
> > > ---
> > >  drivers/md/raid0.c |    2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c index
> > > c4d420b..807ca3a 100644
> > > --- a/drivers/md/raid0.c
> > > +++ b/drivers/md/raid0.c
> > > @@ -266,6 +266,8 @@ static int create_strip_zones(struct mddev *mddev,
> > struct r0conf **private_conf)
> > >  	}
> > >  	mddev->queue->backing_dev_info.congested_fn = raid0_congested;
> > >  	mddev->queue->backing_dev_info.congested_data = mddev;
> > > +	mddev->queue->limits.discard_granularity =
> > > +			queue_logical_block_size(mddev->queue);
> > >
> > >  	/*
> > >  	 * now since we have the hard sector sizes, we can make sure
> > 
> > Thanks, but this doesn't seem like the right sort of fix.  It is to specific to the
> > symptom rather than trying to address the underlying problem.
> > 
> > Maybe something like this?  Can you review and test?
> > 
> > Thanks,
> > NeilBrown
> > 
> > 
> > diff --git a/drivers/md/md.c b/drivers/md/md.c index
> > 628cd529343f..740b6340f980 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -3620,6 +3620,7 @@ level_store(struct mddev *mddev, const char
> > *buf, size_t len)
> >  		mddev->in_sync = 1;
> >  		del_timer_sync(&mddev->safemode_timer);
> >  	}
> > +	blk_set_stacking_limit(&mddev->queue->limits);
> >  	pers->run(mddev);
> >  	set_bit(MD_CHANGE_DEVS, &mddev->flags);
> >  	mddev_resume(mddev);
> Hi Neil,
> I have tested Yours patch, and everything works well.
> TRIM operation are made correctly.
> Could You apply it to upstream? 
> 
> BTW. Correct name of this function is blk_set_stacking_limits();
> 
> Thanks,
> Paweł Baldysiak

Thanks for testing.  I've queue the following up for submission soonish.

NeilBrown

From 3d2b31bb23ccb8170fafdf358098bb3cb0836080 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@...e.de>
Date: Thu, 7 Nov 2013 13:36:36 +1100
Subject: [PATCH] md: fix calculation of stacking limits on level change.

The various ->run routines of md personalities assume that the 'queue'
has been initialised by the blk_set_stacking_limits() call in
md_alloc().

However when the level is changed (by level_store()) the ->run routine
for the new level is called for an array which has already had the
stacking limits modified.  This can result in incorrect final
settings.

So call blk_set_stacking_limits() before ->run in level_store().

A specific consequence of this bug is that it causes
discard_granularity to be set incorrectly when reshaping a RAID4 to a
RAID0.

This is suitable for any -stable kernel since 3.3 in which
blk_set_stacking_limits() was introduced.

Cc: stable@...r.kernel.org (3.3+)
Reported-by: "Baldysiak, Pawel" <pawel.baldysiak@...el.com>
Signed-off-by: NeilBrown <neilb@...e.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 628cd529343f..b3a75afee560 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3620,6 +3620,7 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
 		mddev->in_sync = 1;
 		del_timer_sync(&mddev->safemode_timer);
 	}
+	blk_set_stacking_limits(&mddev->queue->limits);
 	pers->run(mddev);
 	set_bit(MD_CHANGE_DEVS, &mddev->flags);
 	mddev_resume(mddev);

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