RE: LVM on md0: raid0_make_request bug: can't convert block acros s chunks or bigger than 64k

RE: LVM on md0: raid0_make_request bug: can't convert block acros s chunks or bigger than 64k

[Karl Vogel]

> > Somebody else referred to this posting:
> >   http://marc.theaimsgroup.com/?l=linux-kernel&m=103369952814053&w=2
> > 
> > but that patch doesn't apply cleanly anymore and I'm not 
> familiar with
> > the code to be confident to fix it up myself. (that post 
> was from almost
> > exactly 1 year ago, so alot changed probably :)
> 
> That patch is already included.
> 
> The problem is that dm is not honouring the merge_bvec_fn that
> raid0 has set.
> 
> This patch might fix it, but I'm not very familiar with the dm code,
> so I make no promises.

I will give it a shot when I get home.

> (I wonder why you are running LVM on top of raid0 given that lvm
> contains raid0 functionality).
> 
> NeilBrown

Historical reasons.. but since it worked, I never changed it.. and now it
makes for a good test case :)

Thx,
Karl

Re: LVM on md0: raid0_make_request bug: can't convert block across chunks or bigger than 64k

[Neil Brown]

On Monday October 20, karl.vogel@seagha.com wrote:
> On Mon, 2003-10-20 at 23:06, Kevin Corry wrote:
> > On Monday 20 October 2003 15:35, Karl Vogel wrote:
> > > I'm getting the following kernel messages on V2.6.0-test8-mm1 (I've also
> > > tried plain -test7 and some kernels before that) when copying moderately
> > > sized files from a raid-0/LVM volume:
> > >
> > > --- snip ---
> > > raid0_make_request bug: can't convert block across chunks or bigger than
> > > 64k 24081064 64
> > > raid0_make_request bug: can't convert block across chunks or bigger than
> > > 64k 24080656 64
> > > raid0_make_request bug: can't convert block across chunks or bigger than
> > > 64k 24080784 64
> > > raid0_make_request bug: can't convert block across chunks or bigger than
> > > 64k 24080928 64
> > 
> > Looks like this was just recently fixed on the linux-raid list.
> > 
> > http://marc.theaimsgroup.com/?l=linux-raid&m=106661294929434
> 
> Applied the patch on 2.6.0-test8-mm1 but it made no difference.

no, thats a completely different problem.

> 
> Somebody else referred to this posting:
>   http://marc.theaimsgroup.com/?l=linux-kernel&m=103369952814053&w=2
> 
> but that patch doesn't apply cleanly anymore and I'm not familiar with
> the code to be confident to fix it up myself. (that post was from almost
> exactly 1 year ago, so alot changed probably :)

That patch is already included.

The problem is that dm is not honouring the merge_bvec_fn that
raid0 has set.

This patch might fix it, but I'm not very familiar with the dm code,
so I make no promises.

(I wonder why you are running LVM on top of raid0 given that lvm
contains raid0 functionality).

NeilBrown



 ----------- Diffstat output ------------
 ./drivers/md/dm-table.c |    5 +++++
 1 files changed, 5 insertions(+)

diff ./drivers/md/dm-table.c~current~ ./drivers/md/dm-table.c
--- ./drivers/md/dm-table.c~current~	2003-10-21 10:05:29.000000000 +1000
+++ ./drivers/md/dm-table.c	2003-10-21 10:06:27.000000000 +1000
@@ -489,6 +489,11 @@ int dm_get_device(struct dm_target *ti, 
 		rs->max_sectors =
 			min_not_zero(rs->max_sectors, q->max_sectors);
 
+		if (q->merge_bvec_fn)
+			rs->max_sectors =
+				min_not_zero(rs->max_sectors, PAGE_SIZE>>9);
+			
+
 		rs->max_phys_segments =
 			min_not_zero(rs->max_phys_segments,
 				     q->max_phys_segments);

Re: LVM on md0: raid0_make_request bug: can't convert block acros s chunks or bigger than 64k

[Karl Vogel]

On Tue, 2003-10-21 at 02:09, Neil Brown wrote:

> The problem is that dm is not honouring the merge_bvec_fn that
> raid0 has set.
> 
> This patch might fix it, but I'm not very familiar with the dm code,
> so I make no promises.
> 
> (I wonder why you are running LVM on top of raid0 given that lvm
> contains raid0 functionality).
> 
> NeilBrown
> 
> 
> 
>  ----------- Diffstat output ------------
>  ./drivers/md/dm-table.c |    5 +++++
>  1 files changed, 5 insertions(+)
> 
> diff ./drivers/md/dm-table.c~current~ ./drivers/md/dm-table.c
> --- ./drivers/md/dm-table.c~current~	2003-10-21 10:05:29.000000000
> +1000
> +++ ./drivers/md/dm-table.c	2003-10-21 10:06:27.000000000 +1000
> @@ -489,6 +489,11 @@ int dm_get_device(struct dm_target *ti, 
>  		rs->max_sectors =
>  			min_not_zero(rs->max_sectors, q->max_sectors);
>  
> +		if (q->merge_bvec_fn)
> +			rs->max_sectors =
> +				min_not_zero(rs->max_sectors,
> PAGE_SIZE>>9);
> +			
> +
>  		rs->max_phys_segments =
>  			min_not_zero(rs->max_phys_segments,
>  				     q->max_phys_segments);


I noticed in the 2.6.0-test9 notes the following:

---
Neil Brown:
  o md -  Use sector rather than block numbers when splitting raid0
    requests
---

I'm not sure if this is related to the problem I was experiencing?!
Anyway this doesn't fix the problem I was having. I still get the errors
with -test9. Above patch to dm-table.c works for me.

Just thought I'd mention this..

Re: LVM on md0: raid0_make_request bug: can't convert block acros s chunks or bigger than 64k

[Neil Brown]

On Saturday October 25, karl.vogel@seagha.com wrote:
> 
> 
> I noticed in the 2.6.0-test9 notes the following:
> 
> ---
> Neil Brown:
>   o md -  Use sector rather than block numbers when splitting raid0
>     requests
> ---
> 
> I'm not sure if this is related to the problem I was experiencing?!
> Anyway this doesn't fix the problem I was having. I still get the errors
> with -test9. Above patch to dm-table.c works for me.
> 
> Just thought I'd mention this..
> 
This addresses a different problem: raid0 would not correctly handle
some requests that are not 1K aligned.  XFS does some non-1K-aligned
requests where reading it's journal and caught this bug.
It has nothing to do with LVM or your problem.

NeilBrown