Re: [Xen-devel][PATCH]: Support dynamic resizing of vbds

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Jul 20, 2010 at 09:00:39PM +0200, J. Roeleveld wrote:
> > >
> > > Hmm.. I don't seem to be able to find them.
> > > Care to send them again?
> > >
> > > -- Pasi
> > 
> > I will dig this up and send it out.
> > 
> > Regards,
> > 
> > K. Y
> > 
> 
> 
> found this in my archives:
> 

Thanks, but unfortunately this is not the patch that adds useful 
status/resize information printing..

The patch you attached is already merged into Jeremy's xen.git kernel trees.

-- Pasi

> 
> The attached patch supports dynamic resizing of vbds. This patch fixes a bug 
> in 
> the previous version of this patch that was sent out. With this patch you can 
> perform "online" resizing of  file systems that support online resizing.
> 
> Signed-off-by: K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>

> Subject: Propagate changed size of VBDs
> References: bnc#583677
> Patch-mainline: n/a
> 
> Support dynamic resizing of virtual block devices. This patch supports
> both file backed block devices as well as physical devices that can be
> dynamically resized on the host side.
> 
> Signed-off-by: K. Y. Srinivasan <ksrinivasan@xxxxxxxxxx>
> 
> Index: linux/drivers/xen/blkback/blkback.c
> ===================================================================
> --- linux.orig/drivers/xen/blkback/blkback.c  2010-03-18 14:17:28.000000000 
> -0600
> +++ linux/drivers/xen/blkback/blkback.c       2010-03-18 14:17:33.000000000 
> -0600
> @@ -209,6 +209,7 @@ static void print_stats(blkif_t *blkif)
>  int blkif_schedule(void *arg)
>  {
>       blkif_t *blkif = arg;
> +     struct vbd *vbd = &blkif->vbd;
>  
>       blkif_get(blkif);
>  
> @@ -218,6 +219,8 @@ int blkif_schedule(void *arg)
>       while (!kthread_should_stop()) {
>               if (try_to_freeze())
>                       continue;
> +             if (unlikely(vbd->size != vbd_size(vbd)))
> +                     vbd_resize(blkif);
>  
>               wait_event_interruptible(
>                       blkif->wq,
> Index: linux/drivers/xen/blkback/vbd.c
> ===================================================================
> --- linux.orig/drivers/xen/blkback/vbd.c      2010-03-18 14:17:28.000000000 
> -0600
> +++ linux/drivers/xen/blkback/vbd.c   2010-03-18 14:17:33.000000000 -0600
> @@ -73,6 +73,7 @@ int vbd_create(blkif_t *blkif, blkif_vde
>       }
>  
>       vbd->bdev = bdev;
> +     vbd->size = vbd_size(vbd);
>  
>       if (vbd->bdev->bd_disk == NULL) {
>               DPRINTK("vbd_creat: device %08x doesn't exist.\n",
> @@ -120,3 +121,45 @@ int vbd_translate(struct phys_req *req,
>   out:
>       return rc;
>  }
> +
> +void vbd_resize(blkif_t *blkif)
> +{
> +     struct vbd *vbd = &blkif->vbd;
> +     struct xenbus_transaction xbt;
> +     int err;
> +     struct xenbus_device *dev = blkif->be->dev;
> +     unsigned long long new_size = vbd_size(vbd);
> +
> +     printk(KERN_INFO "VBD Resize: new size %Lu\n", new_size);
> +     vbd->size = new_size;
> +again:
> +     err = xenbus_transaction_start(&xbt);
> +     if (err) {
> +             printk(KERN_WARNING "Error starting transaction");
> +             return;
> +     }
> +     err = xenbus_printf(xbt, dev->nodename, "sectors", "%Lu",
> +                         vbd_size(vbd));
> +     if (err) {
> +             printk(KERN_WARNING "Error writing new size");
> +             goto abort;
> +     }
> +     /*
> +      * Write the current state; we will use this to synchronize
> +      * the front-end. If the current state is "connected" the
> +      * front-end will get the new size information online.
> +      */
> +     err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
> +     if (err) {
> +             printk(KERN_WARNING "Error writing the state");
> +             goto abort;
> +     }
> +
> +     err = xenbus_transaction_end(xbt, 0);
> +     if (err == -EAGAIN)
> +             goto again;
> +     if (err)
> +             printk(KERN_WARNING "Error ending transaction");
> +abort:
> +     xenbus_transaction_end(xbt, 1);
> +}
> Index: linux/drivers/xen/blkback/common.h
> ===================================================================
> --- linux.orig/drivers/xen/blkback/common.h   2010-03-18 14:17:28.000000000 
> -0600
> +++ linux/drivers/xen/blkback/common.h        2010-03-18 14:17:33.000000000 
> -0600
> @@ -56,6 +56,7 @@ struct vbd {
>       unsigned char  type;        /* VDISK_xxx */
>       u32            pdevice;     /* phys device that this vbd maps to */
>       struct block_device *bdev;
> +     sector_t       size;        /* Cached size parameter */
>  };
>  
>  struct backend_info;
> @@ -116,6 +117,7 @@ blkif_t *blkif_alloc(domid_t domid);
>  void blkif_disconnect(blkif_t *blkif);
>  void blkif_free(blkif_t *blkif);
>  int blkif_map(blkif_t *blkif, unsigned long shared_page, unsigned int 
> evtchn);
> +void vbd_resize(blkif_t *blkif);
>  
>  #define blkif_get(_b) (atomic_inc(&(_b)->refcnt))
>  #define blkif_put(_b)                                        \
> Index: linux/drivers/xen/blkfront/blkfront.c
> ===================================================================
> --- linux.orig/drivers/xen/blkfront/blkfront.c        2010-03-18 
> 14:17:28.000000000 -0600
> +++ linux/drivers/xen/blkfront/blkfront.c     2010-03-18 14:17:33.000000000 
> -0600
> @@ -328,9 +328,25 @@ static void connect(struct blkfront_info
>       unsigned int binfo;
>       int err;
>  
> -     if ((info->connected == BLKIF_STATE_CONNECTED) ||
> -         (info->connected == BLKIF_STATE_SUSPENDED) )
> +     switch (info->connected) {
> +     case BLKIF_STATE_CONNECTED:
> +             /*
> +              * Potentially, the back-end may be signalling
> +              * a capacity change; update the capacity.
> +              */
> +             err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
> +                                "sectors", "%Lu", &sectors);
> +             if (XENBUS_EXIST_ERR(err))
> +                     return;
> +             printk(KERN_INFO "Setting capacity to %Lu\n",
> +                    sectors);
> +             set_capacity(info->gd, sectors);
> +             revalidate_disk(info->gd);
> +
> +             /* fall through */
> +     case BLKIF_STATE_SUSPENDED:
>               return;
> +     }
>  
>       DPRINTK("blkfront.c:connect:%s.\n", info->xbdev->otherend);
>  

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