Re: Write barriers on MD RAID1

Re: Write barriers on MD RAID1

[Neil Brown]

On Sunday June 21, ken.milmore@googlemail.com wrote:
> I thought I had better bump my previous post as this regression is still 
> present in 2.6.29.5.

Thanks Ken.

> 
> To recap, commit cec0707e40ae25794b5a2de7b7f03c51961f80d9 has broken 
> write barriers on md raid1 block devices in 2.6.29 and later kernels. 
> Reversing this commit appears to fix the problem.
> 
> Please let me know if I'm harassing the wrong maintainers here!

Jens,
  have you had a chance to look at this?

I think the following patch is appropriate and should go in to
-stable.

Thanks,
NeilBrown


From addd8b129835a63d6df9a38eae20caaa15de5988 Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Wed, 24 Jun 2009 13:39:15 +1000
Subject: [PATCH] Restore barrier support for md and probably other virtual devices.

The next_ordered flag is only meaningful for devices that use __make_request.
So move the test against next_ordered out of generic code and in to
__make_request

Since this test was added, barriers have not worked on md, and (I
think) dm and similar devices that don't use __make_request and so
don't bother to set next_ordered.

Cc: stable@kernel.org
Cc: Ken Milmore <ken.milmore@googlemail.com>
Signed-off-by: NeilBrown <neilb@suse.de>
---
 block/blk-core.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index b06cf5c..fc221aa 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1172,6 +1172,11 @@ static int __make_request(struct request_queue *q, struct bio *bio)
 	const int unplug = bio_unplug(bio);
 	int rw_flags;
 
+	if (bio_barrier(bio) && bio_has_data(bio) &&
+	    (q->next_ordered == QUEUE_ORDERED_NONE)) {
+		bio_endio(bio, -EOPNOTSUPP)
+			return 0;
+	}
 	/*
 	 * low level driver can indicate that it wants pages above a
 	 * certain limit bounced to low memory (ie for highmem, or even
@@ -1472,11 +1477,6 @@ static inline void __generic_make_request(struct bio *bio)
 			err = -EOPNOTSUPP;
 			goto end_io;
 		}
-		if (bio_barrier(bio) && bio_has_data(bio) &&
-		    (q->next_ordered == QUEUE_ORDERED_NONE)) {
-			err = -EOPNOTSUPP;
-			goto end_io;
-		}
 
 		ret = q->make_request_fn(q, bio);
 	} while (ret);
-- 
1.6.3.1

Re: Re: Write barriers on MD RAID1

[Alasdair G Kergon]

On Wed, Jun 24, 2009 at 01:43:35PM +1000, Neil Brown wrote:
> Since this test was added, barriers have not worked on md, and (I
> think) dm and similar devices that don't use __make_request and so
> don't bother to set next_ordered.
 
In dm, we added this:

+       blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN, NULL);

Alasdair

Re: Re: Write barriers on MD RAID1

[NeilBrown]

On Wed, June 24, 2009 5:09 pm, Alasdair G Kergon wrote:
> On Wed, Jun 24, 2009 at 01:43:35PM +1000, Neil Brown wrote:
>> Since this test was added, barriers have not worked on md, and (I
>> think) dm and similar devices that don't use __make_request and so
>> don't bother to set next_ordered.
>
> In dm, we added this:
>
> +       blk_queue_ordered(md->queue, QUEUE_ORDERED_DRAIN, NULL);
>

I obviously didn't grep for the right thing.

This will obviously work, but I can't help thinking it is in the wrong
place.  I don't even have a queue in md/raid1, so making a statement
about how it is ordered just doesn't make sense.

Jens?

NeilBrown

Re: Write barriers on MD RAID1

[Jens Axboe]

On Wed, Jun 24 2009, Neil Brown wrote:
> On Sunday June 21, ken.milmore@googlemail.com wrote:
> > I thought I had better bump my previous post as this regression is still 
> > present in 2.6.29.5.
> 
> Thanks Ken.
> 
> > 
> > To recap, commit cec0707e40ae25794b5a2de7b7f03c51961f80d9 has broken 
> > write barriers on md raid1 block devices in 2.6.29 and later kernels. 
> > Reversing this commit appears to fix the problem.
> > 
> > Please let me know if I'm harassing the wrong maintainers here!
> 
> Jens,
>   have you had a chance to look at this?

Yeah, I think it's the right way to go. I'll queue it up for .31 and we
should put in in -stable as well.

> 
> I think the following patch is appropriate and should go in to
> -stable.
> 
> Thanks,
> NeilBrown
> 
> 
> From addd8b129835a63d6df9a38eae20caaa15de5988 Mon Sep 17 00:00:00 2001
> From: NeilBrown <neilb@suse.de>
> Date: Wed, 24 Jun 2009 13:39:15 +1000
> Subject: [PATCH] Restore barrier support for md and probably other virtual devices.
> 
> The next_ordered flag is only meaningful for devices that use __make_request.
> So move the test against next_ordered out of generic code and in to
> __make_request
> 
> Since this test was added, barriers have not worked on md, and (I
> think) dm and similar devices that don't use __make_request and so
> don't bother to set next_ordered.
> 
> Cc: stable@kernel.org
> Cc: Ken Milmore <ken.milmore@googlemail.com>
> Signed-off-by: NeilBrown <neilb@suse.de>
> ---
>  block/blk-core.c |   10 +++++-----
>  1 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index b06cf5c..fc221aa 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1172,6 +1172,11 @@ static int __make_request(struct request_queue *q, struct bio *bio)
>  	const int unplug = bio_unplug(bio);
>  	int rw_flags;
>  
> +	if (bio_barrier(bio) && bio_has_data(bio) &&
> +	    (q->next_ordered == QUEUE_ORDERED_NONE)) {
> +		bio_endio(bio, -EOPNOTSUPP)
> +			return 0;
> +	}
>  	/*
>  	 * low level driver can indicate that it wants pages above a
>  	 * certain limit bounced to low memory (ie for highmem, or even
> @@ -1472,11 +1477,6 @@ static inline void __generic_make_request(struct bio *bio)
>  			err = -EOPNOTSUPP;
>  			goto end_io;
>  		}
> -		if (bio_barrier(bio) && bio_has_data(bio) &&
> -		    (q->next_ordered == QUEUE_ORDERED_NONE)) {
> -			err = -EOPNOTSUPP;
> -			goto end_io;
> -		}
>  
>  		ret = q->make_request_fn(q, bio);
>  	} while (ret);
> -- 
> 1.6.3.1
> 

-- 
Jens Axboe

Re: Write barriers on MD RAID1

[Neil Brown]

On Wednesday June 24, jens.axboe@oracle.com wrote:
> On Wed, Jun 24 2009, Neil Brown wrote:
> > On Sunday June 21, ken.milmore@googlemail.com wrote:
> > > I thought I had better bump my previous post as this regression is still 
> > > present in 2.6.29.5.
> > 
> > Thanks Ken.
> > 
> > > 
> > > To recap, commit cec0707e40ae25794b5a2de7b7f03c51961f80d9 has broken 
> > > write barriers on md raid1 block devices in 2.6.29 and later kernels. 
> > > Reversing this commit appears to fix the problem.
> > > 
> > > Please let me know if I'm harassing the wrong maintainers here!
> > 
> > Jens,
> >   have you had a chance to look at this?
> 
> Yeah, I think it's the right way to go. I'll queue it up for .31 and we
> should put in in -stable as well.

Great, thanks.

NeilBrown


> 
> > 
> > I think the following patch is appropriate and should go in to
> > -stable.
> > 
> > Thanks,
> > NeilBrown
> > 
> > 
> > From addd8b129835a63d6df9a38eae20caaa15de5988 Mon Sep 17 00:00:00 2001
> > From: NeilBrown <neilb@suse.de>
> > Date: Wed, 24 Jun 2009 13:39:15 +1000
> > Subject: [PATCH] Restore barrier support for md and probably other virtual devices.
> > 
> > The next_ordered flag is only meaningful for devices that use __make_request.
> > So move the test against next_ordered out of generic code and in to
> > __make_request
> > 
> > Since this test was added, barriers have not worked on md, and (I
> > think) dm and similar devices that don't use __make_request and so
> > don't bother to set next_ordered.
> > 
> > Cc: stable@kernel.org
> > Cc: Ken Milmore <ken.milmore@googlemail.com>
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > ---
> >  block/blk-core.c |   10 +++++-----
> >  1 files changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index b06cf5c..fc221aa 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -1172,6 +1172,11 @@ static int __make_request(struct request_queue *q, struct bio *bio)
> >  	const int unplug = bio_unplug(bio);
> >  	int rw_flags;
> >  
> > +	if (bio_barrier(bio) && bio_has_data(bio) &&
> > +	    (q->next_ordered == QUEUE_ORDERED_NONE)) {
> > +		bio_endio(bio, -EOPNOTSUPP)
> > +			return 0;
> > +	}
> >  	/*
> >  	 * low level driver can indicate that it wants pages above a
> >  	 * certain limit bounced to low memory (ie for highmem, or even
> > @@ -1472,11 +1477,6 @@ static inline void __generic_make_request(struct bio *bio)
> >  			err = -EOPNOTSUPP;
> >  			goto end_io;
> >  		}
> > -		if (bio_barrier(bio) && bio_has_data(bio) &&
> > -		    (q->next_ordered == QUEUE_ORDERED_NONE)) {
> > -			err = -EOPNOTSUPP;
> > -			goto end_io;
> > -		}
> >  
> >  		ret = q->make_request_fn(q, bio);
> >  	} while (ret);
> > -- 
> > 1.6.3.1
> > 
> 
> -- 
> Jens Axboe