xen/blkback: Propagate changed size of VBDs

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@novell.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index a2ac7189cc0acc19aa523d63830e371393f09554..6d897664802d92257caa3c1443cbd9adc71b7a81 100644 (file)
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -207,6 +207,7 @@ static void print_stats(blkif_t *blkif)
 int blkif_schedule(void *arg)
 {
        blkif_t *blkif = arg;
+       struct vbd *vbd = &blkif->vbd;
 
        blkif_get(blkif);
 
@@ -216,6 +217,8 @@ 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,

diff --git a/drivers/xen/blkback/common.h b/drivers/xen/blkback/common.h
index aaf36485bc019a8234fde172767117a2f42d5842..cebcc2b7e9f63a46f21882b7665106b0c36f488e 100644 (file)
--- a/drivers/xen/blkback/common.h
+++ b/drivers/xen/blkback/common.h
@@ -52,6 +52,7 @@ 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;
@@ -98,6 +99,7 @@ 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)                                  \

diff --git a/drivers/xen/blkback/vbd.c b/drivers/xen/blkback/vbd.c
index 410c2eac5ad7f819c2ab7c8762523914f1693eb5..0635c54079f84a9fbce43647f5c64617fb9a79e0 100644 (file)
--- a/drivers/xen/blkback/vbd.c
+++ b/drivers/xen/blkback/vbd.c
@@ -73,6 +73,7 @@ int vbd_create(blkif_t *blkif, blkif_vdev_t handle, unsigned major,
        }
 
        vbd->bdev = bdev;
+       vbd->size = vbd_size(vbd);
 
        if (vbd->bdev->bd_disk == NULL) {
                DPRINTK("vbd_creat: device %08x doesn't exist.\n",
@@ -116,3 +117,45 @@ int vbd_translate(struct phys_req *req, blkif_t *blkif, int operation)
  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);
+}