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blkback: add support for hotplug scripts

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Hotplug scripts are needed in order to use fancy disk configurations in xl,
like iSCSI disks. The job of hotplug scripts is to locally attach the disk
and present it to blkback as a block device or a regular file.

This change introduces a new xenstore node in the blkback hierarchy, called
"physical-device-path". This is a straigh replacement for the "params" node,
which was used before.

Hotplug scripts will need to read the "params" node, perform whatever
actions are necessary and then write the "physical-device-path" node. The
hotplug script is also in charge of detaching the disk once the domain has
been shutdown.

Sponsored by: Citrix Systems R&D
This commit is contained in:
Roger Pau Monné 2016-06-03 11:38:52 +00:00
parent 477ef5caf6
commit de0bad0001
1 changed files with 127 additions and 79 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

206
sys/dev/xen/blkback/blkback.c
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@ -802,6 +802,9 @@ struct xbb_softc {
/** How many times we have run out of request structures */
uint64_t request_shortages;
/** Watch to wait for hotplug script execution */
struct xs_watch hotplug_watch;
};
/*---------------------------- Request Processing ----------------------------*/
@ -3306,7 +3309,7 @@ xbb_connect(struct xbb_softc *xbb)
{
int error;
if (xenbus_get_state(xbb->dev) == XenbusStateConnected)
if (xenbus_get_state(xbb->dev) != XenbusStateInitialised)
return;
if (xbb_collect_frontend_info(xbb) != 0)
@ -3403,6 +3406,12 @@ xbb_shutdown(struct xbb_softc *xbb)
xbb->flags |= XBBF_IN_SHUTDOWN;
mtx_unlock(&xbb->lock);
if (xbb->hotplug_watch.node != NULL) {
xs_unregister_watch(&xbb->hotplug_watch);
free(xbb->hotplug_watch.node, M_XENBLOCKBACK);
xbb->hotplug_watch.node = NULL;
}
if (xenbus_get_state(xbb->dev) < XenbusStateClosing)
xenbus_set_state(xbb->dev, XenbusStateClosing);
@ -3583,6 +3592,107 @@ xbb_setup_sysctl(struct xbb_softc *xbb)
"communication channel pages (negotiated)");
}
static void
xbb_attach_disk(struct xs_watch *watch, const char **vec, unsigned int len)
{
device_t dev;
struct xbb_softc *xbb;
int error;
dev = (device_t) watch->callback_data;
xbb = device_get_softc(dev);
error = xs_gather(XST_NIL, xenbus_get_node(dev), "physical-device-path",
NULL, &xbb->dev_name, NULL);
if (error != 0)
return;
xs_unregister_watch(watch);
free(watch->node, M_XENBLOCKBACK);
watch->node = NULL;
/* Collect physical device information. */
error = xs_gather(XST_NIL, xenbus_get_otherend_path(xbb->dev),
"device-type", NULL, &xbb->dev_type,
NULL);
if (error != 0)
xbb->dev_type = NULL;
error = xs_gather(XST_NIL, xenbus_get_node(dev),
"mode", NULL, &xbb->dev_mode,
NULL);
if (error != 0) {
xbb_attach_failed(xbb, error, "reading backend fields at %s",
xenbus_get_node(dev));
return;
}
/* Parse fopen style mode flags. */
if (strchr(xbb->dev_mode, 'w') == NULL)
xbb->flags |= XBBF_READ_ONLY;
/*
* Verify the physical device is present and can support
* the desired I/O mode.
*/
error = xbb_open_backend(xbb);
if (error != 0) {
xbb_attach_failed(xbb, error, "Unable to open %s",
xbb->dev_name);
return;
}
/* Use devstat(9) for recording statistics. */
xbb->xbb_stats = devstat_new_entry("xbb", device_get_unit(xbb->dev),
xbb->sector_size,
DEVSTAT_ALL_SUPPORTED,
DEVSTAT_TYPE_DIRECT
| DEVSTAT_TYPE_IF_OTHER,
DEVSTAT_PRIORITY_OTHER);
xbb->xbb_stats_in = devstat_new_entry("xbbi", device_get_unit(xbb->dev),
xbb->sector_size,
DEVSTAT_ALL_SUPPORTED,
DEVSTAT_TYPE_DIRECT
| DEVSTAT_TYPE_IF_OTHER,
DEVSTAT_PRIORITY_OTHER);
/*
* Setup sysctl variables.
*/
xbb_setup_sysctl(xbb);
/*
* Create a taskqueue for doing work that must occur from a
* thread context.
*/
xbb->io_taskqueue = taskqueue_create_fast(device_get_nameunit(dev),
M_NOWAIT,
taskqueue_thread_enqueue,
/*contxt*/&xbb->io_taskqueue);
if (xbb->io_taskqueue == NULL) {
xbb_attach_failed(xbb, error, "Unable to create taskqueue");
return;
}
taskqueue_start_threads(&xbb->io_taskqueue,
/*num threads*/1,
/*priority*/PWAIT,
/*thread name*/
"%s taskq", device_get_nameunit(dev));
/* Update hot-plug status to satisfy xend. */
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"hotplug-status", "connected");
if (error) {
xbb_attach_failed(xbb, error, "writing %s/hotplug-status",
xenbus_get_node(xbb->dev));
return;
}
/* Tell the front end that we are ready to connect. */
xenbus_set_state(dev, XenbusStateInitialised);
}
/**
* Attach to a XenBus device that has been claimed by our probe routine.
*
@ -3596,6 +3706,7 @@ xbb_attach(device_t dev)
struct xbb_softc *xbb;
int error;
u_int max_ring_page_order;
struct sbuf *watch_path;
DPRINTF("Attaching to %s\n", xenbus_get_node(dev));
@ -3639,88 +3750,25 @@ xbb_attach(device_t dev)
return (error);
}
/* Collect physical device information. */
error = xs_gather(XST_NIL, xenbus_get_otherend_path(xbb->dev),
"device-type", NULL, &xbb->dev_type,
NULL);
if (error != 0)
xbb->dev_type = NULL;
error = xs_gather(XST_NIL, xenbus_get_node(dev),
"mode", NULL, &xbb->dev_mode,
"params", NULL, &xbb->dev_name,
NULL);
/*
* We need to wait for hotplug script execution before
* moving forward.
*/
watch_path = xs_join(xenbus_get_node(xbb->dev), "physical-device-path");
xbb->hotplug_watch.callback_data = (uintptr_t)dev;
xbb->hotplug_watch.callback = xbb_attach_disk;
KASSERT(xbb->hotplug_watch.node == NULL, ("watch node already setup"));
xbb->hotplug_watch.node = strdup(sbuf_data(watch_path), M_XENBLOCKBACK);
sbuf_delete(watch_path);
error = xs_register_watch(&xbb->hotplug_watch);
if (error != 0) {
xbb_attach_failed(xbb, error, "reading backend fields at %s",
xenbus_get_node(dev));
return (ENXIO);
}
/* Parse fopen style mode flags. */
if (strchr(xbb->dev_mode, 'w') == NULL)
xbb->flags |= XBBF_READ_ONLY;
/*
* Verify the physical device is present and can support
* the desired I/O mode.
*/
DROP_GIANT();
error = xbb_open_backend(xbb);
PICKUP_GIANT();
if (error != 0) {
xbb_attach_failed(xbb, error, "Unable to open %s",
xbb->dev_name);
return (ENXIO);
}
/* Use devstat(9) for recording statistics. */
xbb->xbb_stats = devstat_new_entry("xbb", device_get_unit(xbb->dev),
xbb->sector_size,
DEVSTAT_ALL_SUPPORTED,
DEVSTAT_TYPE_DIRECT
| DEVSTAT_TYPE_IF_OTHER,
DEVSTAT_PRIORITY_OTHER);
xbb->xbb_stats_in = devstat_new_entry("xbbi", device_get_unit(xbb->dev),
xbb->sector_size,
DEVSTAT_ALL_SUPPORTED,
DEVSTAT_TYPE_DIRECT
| DEVSTAT_TYPE_IF_OTHER,
DEVSTAT_PRIORITY_OTHER);
/*
* Setup sysctl variables.
*/
xbb_setup_sysctl(xbb);
/*
* Create a taskqueue for doing work that must occur from a
* thread context.
*/
xbb->io_taskqueue = taskqueue_create_fast(device_get_nameunit(dev),
M_NOWAIT,
taskqueue_thread_enqueue,
/*contxt*/&xbb->io_taskqueue);
if (xbb->io_taskqueue == NULL) {
xbb_attach_failed(xbb, error, "Unable to create taskqueue");
return (ENOMEM);
}
taskqueue_start_threads(&xbb->io_taskqueue,
/*num threads*/1,
/*priority*/PWAIT,
/*thread name*/
"%s taskq", device_get_nameunit(dev));
/* Update hot-plug status to satisfy xend. */
error = xs_printf(XST_NIL, xenbus_get_node(xbb->dev),
"hotplug-status", "connected");
if (error) {
xbb_attach_failed(xbb, error, "writing %s/hotplug-status",
xenbus_get_node(xbb->dev));
xbb_attach_failed(xbb, error, "failed to create watch on %s",
xbb->hotplug_watch.node);
free(xbb->hotplug_watch.node, M_XENBLOCKBACK);
return (error);
}
/* Tell the front end that we are ready to connect. */
/* Tell the toolstack blkback has attached. */
xenbus_set_state(dev, XenbusStateInitWait);
return (0);