Re: [Xen-devel] [PATCH] libxl: don't launch more than one tapdisk process for each disk

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Mar 05, 2013 at 05:56:42PM +0100, Roger Pau Monne wrote:
> When adding a disk don't launch multiple tapdisk instances for the
> same disk, if transaction fails in device_disk_add reuse the same
> tapdisk for further tries instead of creating a new instance each
> time a transaction fails.
>

So this patch should be backported to Xen 4.2 after it has passed xen-unstable 
tests.
See Darren's reply with a Xen 4.2.1 backport included.

-- Pasi
 
> Reported-by: Darren Shepherd <darren.s.shepherd@xxxxxxxxx>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
>  tools/libxl/libxl.c |   17 ++++++++++-------
>  1 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index 73e0dc3..345d88b 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -2032,7 +2032,7 @@ static void device_disk_add(libxl__egc *egc, uint32_t 
> domid,
>      STATE_AO_GC(aodev->ao);
>      flexarray_t *front = NULL;
>      flexarray_t *back = NULL;
> -    char *dev, *script;
> +    char *dev = NULL, *script;
>      libxl__device *device;
>      int rc;
>      libxl_ctx *ctx = gc->owner;
> @@ -2095,12 +2095,15 @@ static void device_disk_add(libxl__egc *egc, uint32_t 
> domid,
>                  break;
>  
>              case LIBXL_DISK_BACKEND_TAP:
> -                dev = libxl__blktap_devpath(gc, disk->pdev_path, 
> disk->format);
> -                if (!dev) {
> -                    LOG(ERROR, "failed to get blktap devpath for %p\n",
> -                        disk->pdev_path);
> -                    rc = ERROR_FAIL;
> -                    goto out;
> +                if (dev == NULL) {
> +                    dev = libxl__blktap_devpath(gc, disk->pdev_path,
> +                                                disk->format);
> +                    if (!dev) {
> +                        LOG(ERROR, "failed to get blktap devpath for %p\n",
> +                            disk->pdev_path);
> +                        rc = ERROR_FAIL;
> +                        goto out;
> +                    }
>                  }
>                  flexarray_append(back, "tapdisk-params");
>                  flexarray_append(back, libxl__sprintf(gc, "%s:%s",
> -- 
> 1.7.7.5 (Apple Git-26)
> 
> 
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