Re: Fatal crash on xen4.2 HVM + qemu-xen dm + NFS

[Alex Bligh <alex@alex.org.uk>]

Konrad / Stefano,

Any movement / ideas on this one?

Alex

--On 25 January 2013 11:28:31 +0000 Alex Bligh <alex@alex.org.uk> wrote:

> Konrad,
>
> --On 23 January 2013 16:29:20 +0000 Stefano Stabellini
> <stefano.stabellini@eu.citrix.com> wrote:
>
>>> diff --git a/hw/xen_disk.c b/hw/xen_disk.c
>>> index a402ac8..1c3a6f5 100644
>>> --- a/hw/xen_disk.c
>>> +++ b/hw/xen_disk.c
>>> @@ -603,7 +603,7 @@ static int blk_init(struct XenDevice *xendev)
>>>      }
>>>
>>>      /* read-only ? */
>>> -    qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
>>> +    qflags = /* BDRV_O_NOCACHE | */ BDRV_O_CACHE_WB |
>>> BDRV_O_NATIVE_AIO; if (strcmp(blkdev->mode, "w") == 0) {
>>>          qflags |= BDRV_O_RDWR;
>>>      } else {
>>
>> Before going for something like that I would like a confirmation from
>> Konrad about blkfront behavior regarding barriers and
>> BLKIF_OP_FLUSH_DISKCACHE. I certainly don't want to risk data
>> corruptions.
>
> Any ideas?
>
>
> A slightly prettier patch would look like the one pasted
> below (not sent with git-sendemail so beware whitespace issues).
>
> --
> Alex Bligh
>
> commit a7d7296aebc21af15074f3bf64c5c6795ca05f16
> Author: Alex Bligh <alex@alex.org.uk>
> Date:   Thu Jan 24 09:41:34 2013 +0000
>
>     Disable use of O_DIRECT by default as it results in crashes.
>
>     See:
>       http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html
>     for more details.
>
> diff --git a/hw/xen_disk.c b/hw/xen_disk.c
> index a402ac8..a618d8d 100644
> --- a/hw/xen_disk.c
> +++ b/hw/xen_disk.c
> @@ -45,6 +45,8 @@ static int batch_maps   = 0;
>
>  static int max_requests = 32;
>
> +static int use_o_direct = 0;
> +
>  /* ------------------------------------------------------------- */
>
>  #define BLOCK_SIZE  512
> @@ -603,7 +605,7 @@ static int blk_init(struct XenDevice *xendev)
>      }
>
>      /* read-only ? */
> -    qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO;
> +    qflags = (use_o_direct?BDRV_O_NOCACHE:0) | BDRV_O_CACHE_WB |
> BDRV_O_NATIVE_AIO;
>      if (strcmp(blkdev->mode, "w") == 0) {
>          qflags |= BDRV_O_RDWR;
>      } else {
>
>
>



-- 
Alex Bligh