Re: [Xen-devel] Unstableness in grant table block drivers

[Christopher Clark <christopher.w.clark@xxxxxxxxx>]

Ryan

Many thanks for taking the traces. I've located a bug in the block
backend that may or may not be the required fix -- it's a move of a
single line, see the patch below.

c.

Signed-off-by: Christopher Clark

diff -Nru a/linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c
b/linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c
--- a/linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c 2005-04-20
11:31:20 -07:00
+++ b/linux-2.6.11-xen-sparse/drivers/xen/blkback/blkback.c 2005-04-20
11:31:20 -07:00
@@ -516,11 +516,11 @@

     for ( i = 0; i < nseg; i++ )
     {
+        fas         = req->frame_and_sects[i];
 #ifdef CONFIG_XEN_BLKDEV_GRANT
         seg[i].buf  = (aop[i].u.map_grant_ref.dev_bus_addr << PAGE_SHIFT) |
                       (blkif_first_sect(fas) << 9);
 #else
-        fas          = req->frame_and_sects[i];
         seg[i].buf  = (fas & PAGE_MASK) | (blkif_first_sect(fas) << 9);
         seg[i].nsec = blkif_last_sect(fas) - blkif_first_sect(fas) + 1;
         if ( seg[i].nsec <= 0 )



On 4/18/05, Ryan Harper <ryanh@xxxxxxxxxx> wrote:
> * Christopher Clark <christopher.w.clark@xxxxxxxxx> [2005-04-18 11:39]:
> > Ryan and Anthony: I've attached a patch that I'd like you to apply to
> > your unstable tree -- it just printk's almost everything so I can get
> > an idea of the code path you're running.
> > Alternatively, the three .c files modified by the patch are also
> > attached - they're taken from 2005-04-14 unstable and you should be
> > able to just replace the files in your tree.
> >
> > After changing your tree and rebuilding, please send the console logs
> > from boot onwards for xen/dom0 and domU, in a uniprocessor
> > configuration, both with and without using grant tables for block
> > transport.
> 
> I've applied the patch and I have a bunch of logs.
> 
> 1) domU boot output when dom0up boots domUup
> 2) domU boot output when dom0up boots domUsmp
> 3) xen console output for 1) and 2)
> 4) domU boot output when dom0smp boots domUup
> 5) domU boot output when dom0smp boots domUsmp
> 6) xen console output for 4) and 5)
> 
> In the above cases, dom0up was simulated with maxcpu=1, as I still don't
> have that UP box setup.  If you can't find anything in these logs then
> I'll go get a real UP box and repeat the dumps.
> 
> --
> Ryan Harper
> Software Engineer; Linux Technology Center
> IBM Corp., Austin, Tx
> (512) 838-9253   T/L: 678-9253
> ryanh@xxxxxxxxxx
> 
> 
>

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