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8e3f875554
linux/drivers/block/xen-blkback/xenbus.c
Konrad Rzeszutek Wilk 8e3f875554 xen/blkback: Check for insane amounts of request on the ring (v6). 
Check that the ring does not have an insane amount of requests
(more than there could fit on the ring).

If we detect this case we will stop processing the requests
and wait until the XenBus disconnects the ring.

The existing check RING_REQUEST_CONS_OVERFLOW which checks for how
many responses we have created in the past (rsp_prod_pvt) vs
requests consumed (req_cons) and whether said difference is greater or
equal to the size of the ring, does not catch this case.

Wha the condition does check if there is a need to process more
as we still have a backlog of responses to finish. Note that both
of those values (rsp_prod_pvt and req_cons) are not exposed on the
shared ring.

To understand this problem a mini crash course in ring protocol
response/request updates is in place.

There are four entries: req_prod and rsp_prod; req_event and rsp_event
to track the ring entries. We are only concerned about the first two -
which set the tone of this bug.

The req_prod is a value incremented by frontend for each request put
on the ring. Conversely the rsp_prod is a value incremented by the backend
for each response put on the ring (rsp_prod gets set by rsp_prod_pvt when
pushing the responses on the ring).  Both values can
wrap and are modulo the size of the ring (in block case that is 32).
Please see RING_GET_REQUEST and RING_GET_RESPONSE for the more details.

The culprit here is that if the difference between the
req_prod and req_cons is greater than the ring size we have a problem.
Fortunately for us, the '__do_block_io_op' loop:

	rc = blk_rings->common.req_cons;
	rp = blk_rings->common.sring->req_prod;

	while (rc != rp) {

		..
		blk_rings->common.req_cons = ++rc; /* before make_response() */

	}

will loop up to the point when rc == rp. The macros inside of the
loop (RING_GET_REQUEST) is smart and is indexing based on the modulo
of the ring size. If the frontend has provided a bogus req_prod value
we will loop until the 'rc == rp' - which means we could be processing
already processed requests (or responses) often.

The reason the RING_REQUEST_CONS_OVERFLOW is not helping here is
b/c it only tracks how many responses we have internally produced
and whether we would should process more. The astute reader will
notice that the macro RING_REQUEST_CONS_OVERFLOW provides two
arguments - more on this later.

For example, if we were to enter this function with these values:

       	blk_rings->common.sring->req_prod =  X+31415 (X is the value from
		the last time __do_block_io_op was called).
        blk_rings->common.req_cons = X
        blk_rings->common.rsp_prod_pvt = X

The RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, blk_rings->common.req_cons)
is doing:

	req_cons - rsp_prod_pvt >= 32

Which is,
	X - X >= 32 or 0 >= 32

And that is false, so we continue on looping (this bug).

If we re-use said macro RING_REQUEST_CONS_OVERFLOW and pass in the rp
instead (sring->req_prod) of rc, the this macro can do the check:

     req_prod - rsp_prov_pvt >= 32

Which is,
       X + 31415 - X >= 32 , or 31415 >= 32

which is true, so we can error out and break out of the function.

Unfortunatly the difference between rsp_prov_pvt and req_prod can be
at 32 (which would error out in the macro). This condition exists when
the backend is lagging behind with the responses and still has not finished
responding to all of them (so make_response has not been called), and
the rsp_prov_pvt + 32 == req_cons. This ends up with us not being able
to use said macro.

Hence introducing a new macro called RING_REQUEST_PROD_OVERFLOW which does
a simple check of:

    req_prod - rsp_prod_pvt > RING_SIZE

And with the X values from above:

   X + 31415 - X > 32

Returns true. Also not that if the ring is full (which is where
the RING_REQUEST_CONS_OVERFLOW triggered), we would not hit the
same condition:

   X + 32 - X > 32

Which is false.

Lets use that macro.
Note that in v5 of this patchset the macro was different - we used an
earlier version.

Cc: stable@vger.kernel.org
[v1: Move the check outside the loop]
[v2: Add a pr_warn as suggested by David]
[v3: Use RING_REQUEST_CONS_OVERFLOW as suggested by Jan]
[v4: Move wake_up after kthread_stop as suggested by Jan]
[v5: Use RING_REQUEST_PROD_OVERFLOW instead]
[v6: Use RING_REQUEST_PROD_OVERFLOW - Jan's version]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

gadsa
2013-06-17 15:17:16 -04:00

890 lines
22 KiB
C
Raw Blame History

/* Xenbus code for blkif backend
Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
Copyright (C) 2005 XenSource Ltd
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
*/
#include <stdarg.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <xen/events.h>
#include <xen/grant_table.h>
#include "common.h"
struct backend_info {
struct xenbus_device *dev;
struct xen_blkif *blkif;
struct xenbus_watch backend_watch;
unsigned major;
unsigned minor;
char *mode;
};
static struct kmem_cache *xen_blkif_cachep;
static void connect(struct backend_info *);
static int connect_ring(struct backend_info *);
static void backend_changed(struct xenbus_watch *, const char **,
unsigned int);
struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
{
return be->dev;
}
static int blkback_name(struct xen_blkif *blkif, char *buf)
{
char *devpath, *devname;
struct xenbus_device *dev = blkif->be->dev;
devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
if (IS_ERR(devpath))
return PTR_ERR(devpath);
devname = strstr(devpath, "/dev/");
if (devname != NULL)
devname += strlen("/dev/");
else
devname = devpath;
snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
kfree(devpath);
return 0;
}
static void xen_update_blkif_status(struct xen_blkif *blkif)
{
int err;
char name[TASK_COMM_LEN];
/* Not ready to connect? */
if (!blkif->irq || !blkif->vbd.bdev)
return;
/* Already connected? */
if (blkif->be->dev->state == XenbusStateConnected)
return;
/* Attempt to connect: exit if we fail to. */
connect(blkif->be);
if (blkif->be->dev->state != XenbusStateConnected)
return;
err = blkback_name(blkif, name);
if (err) {
xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
return;
}
err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
if (err) {
xenbus_dev_error(blkif->be->dev, err, "block flush");
return;
}
invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, name);
if (IS_ERR(blkif->xenblkd)) {
err = PTR_ERR(blkif->xenblkd);
blkif->xenblkd = NULL;
xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
return;
}
}
static struct xen_blkif *xen_blkif_alloc(domid_t domid)
{
struct xen_blkif *blkif;
struct pending_req *req, *n;
int i, j;
BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
if (!blkif)
return ERR_PTR(-ENOMEM);
blkif->domid = domid;
spin_lock_init(&blkif->blk_ring_lock);
atomic_set(&blkif->refcnt, 1);
init_waitqueue_head(&blkif->wq);
init_completion(&blkif->drain_complete);
atomic_set(&blkif->drain, 0);
blkif->st_print = jiffies;
init_waitqueue_head(&blkif->waiting_to_free);
blkif->persistent_gnts.rb_node = NULL;
spin_lock_init(&blkif->free_pages_lock);
INIT_LIST_HEAD(&blkif->free_pages);
blkif->free_pages_num = 0;
atomic_set(&blkif->persistent_gnt_in_use, 0);
INIT_LIST_HEAD(&blkif->pending_free);
for (i = 0; i < XEN_BLKIF_REQS; i++) {
req = kzalloc(sizeof(*req), GFP_KERNEL);
if (!req)
goto fail;
list_add_tail(&req->free_list,
&blkif->pending_free);
for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
req->segments[j] = kzalloc(sizeof(*req->segments[0]),
GFP_KERNEL);
if (!req->segments[j])
goto fail;
}
for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
req->indirect_pages[j] = kzalloc(sizeof(*req->indirect_pages[0]),
GFP_KERNEL);
if (!req->indirect_pages[j])
goto fail;
}
}
spin_lock_init(&blkif->pending_free_lock);
init_waitqueue_head(&blkif->pending_free_wq);
init_waitqueue_head(&blkif->shutdown_wq);
return blkif;
fail:
list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
list_del(&req->free_list);
for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
if (!req->segments[j])
break;
kfree(req->segments[j]);
}
for (j = 0; j < MAX_INDIRECT_PAGES; j++) {
if (!req->indirect_pages[j])
break;
kfree(req->indirect_pages[j]);
}
kfree(req);
}
kmem_cache_free(xen_blkif_cachep, blkif);
return ERR_PTR(-ENOMEM);
}
static int xen_blkif_map(struct xen_blkif *blkif, unsigned long shared_page,
unsigned int evtchn)
{
int err;
/* Already connected through? */
if (blkif->irq)
return 0;
err = xenbus_map_ring_valloc(blkif->be->dev, shared_page, &blkif->blk_ring);
if (err < 0)
return err;
switch (blkif->blk_protocol) {
case BLKIF_PROTOCOL_NATIVE:
{
struct blkif_sring *sring;
sring = (struct blkif_sring *)blkif->blk_ring;
BACK_RING_INIT(&blkif->blk_rings.native, sring, PAGE_SIZE);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
struct blkif_x86_32_sring *sring_x86_32;
sring_x86_32 = (struct blkif_x86_32_sring *)blkif->blk_ring;
BACK_RING_INIT(&blkif->blk_rings.x86_32, sring_x86_32, PAGE_SIZE);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
struct blkif_x86_64_sring *sring_x86_64;
sring_x86_64 = (struct blkif_x86_64_sring *)blkif->blk_ring;
BACK_RING_INIT(&blkif->blk_rings.x86_64, sring_x86_64, PAGE_SIZE);
break;
}
default:
BUG();
}
err = bind_interdomain_evtchn_to_irqhandler(blkif->domid, evtchn,
xen_blkif_be_int, 0,
"blkif-backend", blkif);
if (err < 0) {
xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
blkif->blk_rings.common.sring = NULL;
return err;
}
blkif->irq = err;
return 0;
}
static void xen_blkif_disconnect(struct xen_blkif *blkif)
{
if (blkif->xenblkd) {
kthread_stop(blkif->xenblkd);
wake_up(&blkif->shutdown_wq);
blkif->xenblkd = NULL;
}
atomic_dec(&blkif->refcnt);
wait_event(blkif->waiting_to_free, atomic_read(&blkif->refcnt) == 0);
atomic_inc(&blkif->refcnt);
if (blkif->irq) {
unbind_from_irqhandler(blkif->irq, blkif);
blkif->irq = 0;
}
if (blkif->blk_rings.common.sring) {
xenbus_unmap_ring_vfree(blkif->be->dev, blkif->blk_ring);
blkif->blk_rings.common.sring = NULL;
}
}
static void xen_blkif_free(struct xen_blkif *blkif)
{
struct pending_req *req, *n;
int i = 0, j;
if (!atomic_dec_and_test(&blkif->refcnt))
BUG();
/* Check that there is no request in use */
list_for_each_entry_safe(req, n, &blkif->pending_free, free_list) {
list_del(&req->free_list);
for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++)
kfree(req->segments[j]);
for (j = 0; j < MAX_INDIRECT_PAGES; j++)
kfree(req->indirect_pages[j]);
kfree(req);
i++;
}
WARN_ON(i != XEN_BLKIF_REQS);
kmem_cache_free(xen_blkif_cachep, blkif);
}
int __init xen_blkif_interface_init(void)
{
xen_blkif_cachep = kmem_cache_create("blkif_cache",
sizeof(struct xen_blkif),
0, 0, NULL);
if (!xen_blkif_cachep)
return -ENOMEM;
return 0;
}
/*
* sysfs interface for VBD I/O requests
*/
#define VBD_SHOW(name, format, args...) \
static ssize_t show_##name(struct device *_dev, \
struct device_attribute *attr, \
char *buf) \
{ \
struct xenbus_device *dev = to_xenbus_device(_dev); \
struct backend_info *be = dev_get_drvdata(&dev->dev); \
\
return sprintf(buf, format, ##args); \
} \
static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
VBD_SHOW(oo_req, "%llu\n", be->blkif->st_oo_req);
VBD_SHOW(rd_req, "%llu\n", be->blkif->st_rd_req);
VBD_SHOW(wr_req, "%llu\n", be->blkif->st_wr_req);
VBD_SHOW(f_req, "%llu\n", be->blkif->st_f_req);
VBD_SHOW(ds_req, "%llu\n", be->blkif->st_ds_req);
VBD_SHOW(rd_sect, "%llu\n", be->blkif->st_rd_sect);
VBD_SHOW(wr_sect, "%llu\n", be->blkif->st_wr_sect);
static struct attribute *xen_vbdstat_attrs[] = {
&dev_attr_oo_req.attr,
&dev_attr_rd_req.attr,
&dev_attr_wr_req.attr,
&dev_attr_f_req.attr,
&dev_attr_ds_req.attr,
&dev_attr_rd_sect.attr,
&dev_attr_wr_sect.attr,
NULL
};
static struct attribute_group xen_vbdstat_group = {
.name = "statistics",
.attrs = xen_vbdstat_attrs,
};
VBD_SHOW(physical_device, "%x:%x\n", be->major, be->minor);
VBD_SHOW(mode, "%s\n", be->mode);
static int xenvbd_sysfs_addif(struct xenbus_device *dev)
{
int error;
error = device_create_file(&dev->dev, &dev_attr_physical_device);
if (error)
goto fail1;
error = device_create_file(&dev->dev, &dev_attr_mode);
if (error)
goto fail2;
error = sysfs_create_group(&dev->dev.kobj, &xen_vbdstat_group);
if (error)
goto fail3;
return 0;
fail3: sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
fail2: device_remove_file(&dev->dev, &dev_attr_mode);
fail1: device_remove_file(&dev->dev, &dev_attr_physical_device);
return error;
}
static void xenvbd_sysfs_delif(struct xenbus_device *dev)
{
sysfs_remove_group(&dev->dev.kobj, &xen_vbdstat_group);
device_remove_file(&dev->dev, &dev_attr_mode);
device_remove_file(&dev->dev, &dev_attr_physical_device);
}
static void xen_vbd_free(struct xen_vbd *vbd)
{
if (vbd->bdev)
blkdev_put(vbd->bdev, vbd->readonly ? FMODE_READ : FMODE_WRITE);
vbd->bdev = NULL;
}
static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle,
unsigned major, unsigned minor, int readonly,
int cdrom)
{
struct xen_vbd *vbd;
struct block_device *bdev;
struct request_queue *q;
vbd = &blkif->vbd;
vbd->handle = handle;
vbd->readonly = readonly;
vbd->type = 0;
vbd->pdevice = MKDEV(major, minor);
bdev = blkdev_get_by_dev(vbd->pdevice, vbd->readonly ?
FMODE_READ : FMODE_WRITE, NULL);
if (IS_ERR(bdev)) {
DPRINTK("xen_vbd_create: device %08x could not be opened.\n",
vbd->pdevice);
return -ENOENT;
}
vbd->bdev = bdev;
if (vbd->bdev->bd_disk == NULL) {
DPRINTK("xen_vbd_create: device %08x doesn't exist.\n",
vbd->pdevice);
xen_vbd_free(vbd);
return -ENOENT;
}
vbd->size = vbd_sz(vbd);
if (vbd->bdev->bd_disk->flags & GENHD_FL_CD || cdrom)
vbd->type |= VDISK_CDROM;
if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE)
vbd->type |= VDISK_REMOVABLE;
q = bdev_get_queue(bdev);
if (q && q->flush_flags)
vbd->flush_support = true;
if (q && blk_queue_secdiscard(q))
vbd->discard_secure = true;
DPRINTK("Successful creation of handle=%04x (dom=%u)\n",
handle, blkif->domid);
return 0;
}
static int xen_blkbk_remove(struct xenbus_device *dev)
{
struct backend_info *be = dev_get_drvdata(&dev->dev);
DPRINTK("");
if (be->major || be->minor)
xenvbd_sysfs_delif(dev);
if (be->backend_watch.node) {
unregister_xenbus_watch(&be->backend_watch);
kfree(be->backend_watch.node);
be->backend_watch.node = NULL;
}
if (be->blkif) {
xen_blkif_disconnect(be->blkif);
xen_vbd_free(&be->blkif->vbd);
xen_blkif_free(be->blkif);
be->blkif = NULL;
}
kfree(be->mode);
kfree(be);
dev_set_drvdata(&dev->dev, NULL);
return 0;
}
int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
struct backend_info *be, int state)
{
struct xenbus_device *dev = be->dev;
int err;
err = xenbus_printf(xbt, dev->nodename, "feature-flush-cache",
"%d", state);
if (err)
dev_warn(&dev->dev, "writing feature-flush-cache (%d)", err);
return err;
}
static void xen_blkbk_discard(struct xenbus_transaction xbt, struct backend_info *be)
{
struct xenbus_device *dev = be->dev;
struct xen_blkif *blkif = be->blkif;
int err;
int state = 0;
struct block_device *bdev = be->blkif->vbd.bdev;
struct request_queue *q = bdev_get_queue(bdev);
if (blk_queue_discard(q)) {
err = xenbus_printf(xbt, dev->nodename,
"discard-granularity", "%u",
q->limits.discard_granularity);
if (err) {
dev_warn(&dev->dev, "writing discard-granularity (%d)", err);
return;
}
err = xenbus_printf(xbt, dev->nodename,
"discard-alignment", "%u",
q->limits.discard_alignment);
if (err) {
dev_warn(&dev->dev, "writing discard-alignment (%d)", err);
return;
}
state = 1;
/* Optional. */
err = xenbus_printf(xbt, dev->nodename,
"discard-secure", "%d",
blkif->vbd.discard_secure);
if (err) {
dev_warn(&dev->dev, "writing discard-secure (%d)", err);
return;
}
}
err = xenbus_printf(xbt, dev->nodename, "feature-discard",
"%d", state);
if (err)
dev_warn(&dev->dev, "writing feature-discard (%d)", err);
}
int xen_blkbk_barrier(struct xenbus_transaction xbt,
struct backend_info *be, int state)
{
struct xenbus_device *dev = be->dev;
int err;
err = xenbus_printf(xbt, dev->nodename, "feature-barrier",
"%d", state);
if (err)
dev_warn(&dev->dev, "writing feature-barrier (%d)", err);
return err;
}
/*
* Entry point to this code when a new device is created. Allocate the basic
* structures, and watch the store waiting for the hotplug scripts to tell us
* the device's physical major and minor numbers. Switch to InitWait.
*/
static int xen_blkbk_probe(struct xenbus_device *dev,
const struct xenbus_device_id *id)
{
int err;
struct backend_info *be = kzalloc(sizeof(struct backend_info),
GFP_KERNEL);
if (!be) {
xenbus_dev_fatal(dev, -ENOMEM,
"allocating backend structure");
return -ENOMEM;
}
be->dev = dev;
dev_set_drvdata(&dev->dev, be);
be->blkif = xen_blkif_alloc(dev->otherend_id);
if (IS_ERR(be->blkif)) {
err = PTR_ERR(be->blkif);
be->blkif = NULL;
xenbus_dev_fatal(dev, err, "creating block interface");
goto fail;
}
/* setup back pointer */
be->blkif->be = be;
err = xenbus_watch_pathfmt(dev, &be->backend_watch, backend_changed,
"%s/%s", dev->nodename, "physical-device");
if (err)
goto fail;
err = xenbus_switch_state(dev, XenbusStateInitWait);
if (err)
goto fail;
return 0;
fail:
DPRINTK("failed");
xen_blkbk_remove(dev);
return err;
}
/*
* Callback received when the hotplug scripts have placed the physical-device
* node. Read it and the mode node, and create a vbd. If the frontend is
* ready, connect.
*/
static void backend_changed(struct xenbus_watch *watch,
const char **vec, unsigned int len)
{
int err;
unsigned major;
unsigned minor;
struct backend_info *be
= container_of(watch, struct backend_info, backend_watch);
struct xenbus_device *dev = be->dev;
int cdrom = 0;
unsigned long handle;
char *device_type;
DPRINTK("");
err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x",
&major, &minor);
if (XENBUS_EXIST_ERR(err)) {
/*
* Since this watch will fire once immediately after it is
* registered, we expect this. Ignore it, and wait for the
* hotplug scripts.
*/
return;
}
if (err != 2) {
xenbus_dev_fatal(dev, err, "reading physical-device");
return;
}
if (be->major | be->minor) {
if (be->major != major || be->minor != minor)
pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not supported.\n",
be->major, be->minor, major, minor);
return;
}
be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL);
if (IS_ERR(be->mode)) {
err = PTR_ERR(be->mode);
be->mode = NULL;
xenbus_dev_fatal(dev, err, "reading mode");
return;
}
device_type = xenbus_read(XBT_NIL, dev->otherend, "device-type", NULL);
if (!IS_ERR(device_type)) {
cdrom = strcmp(device_type, "cdrom") == 0;
kfree(device_type);
}
/* Front end dir is a number, which is used as the handle. */
err = strict_strtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
if (err)
return;
be->major = major;
be->minor = minor;
err = xen_vbd_create(be->blkif, handle, major, minor,
!strchr(be->mode, 'w'), cdrom);
if (err)
xenbus_dev_fatal(dev, err, "creating vbd structure");
else {
err = xenvbd_sysfs_addif(dev);
if (err) {
xen_vbd_free(&be->blkif->vbd);
xenbus_dev_fatal(dev, err, "creating sysfs entries");
}
}
if (err) {
kfree(be->mode);
be->mode = NULL;
be->major = 0;
be->minor = 0;
} else {
/* We're potentially connected now */
xen_update_blkif_status(be->blkif);
}
}
/*
* Callback received when the frontend's state changes.
*/
static void frontend_changed(struct xenbus_device *dev,
enum xenbus_state frontend_state)
{
struct backend_info *be = dev_get_drvdata(&dev->dev);
int err;
DPRINTK("%s", xenbus_strstate(frontend_state));
switch (frontend_state) {
case XenbusStateInitialising:
if (dev->state == XenbusStateClosed) {
pr_info(DRV_PFX "%s: prepare for reconnect\n",
dev->nodename);
xenbus_switch_state(dev, XenbusStateInitWait);
}
break;
case XenbusStateInitialised:
case XenbusStateConnected:
/*
* Ensure we connect even when two watches fire in
* close succession and we miss the intermediate value
* of frontend_state.
*/
if (dev->state == XenbusStateConnected)
break;
/*
* Enforce precondition before potential leak point.
* xen_blkif_disconnect() is idempotent.
*/
xen_blkif_disconnect(be->blkif);
err = connect_ring(be);
if (err)
break;
xen_update_blkif_status(be->blkif);
break;
case XenbusStateClosing:
xenbus_switch_state(dev, XenbusStateClosing);
break;
case XenbusStateClosed:
xen_blkif_disconnect(be->blkif);
xenbus_switch_state(dev, XenbusStateClosed);
if (xenbus_dev_is_online(dev))
break;
/* fall through if not online */
case XenbusStateUnknown:
/* implies xen_blkif_disconnect() via xen_blkbk_remove() */
device_unregister(&dev->dev);
break;
default:
xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
frontend_state);
break;
}
}
/* ** Connection ** */
/*
* Write the physical details regarding the block device to the store, and
* switch to Connected state.
*/
static void connect(struct backend_info *be)
{
struct xenbus_transaction xbt;
int err;
struct xenbus_device *dev = be->dev;
DPRINTK("%s", dev->otherend);
/* Supply the information about the device the frontend needs */
again:
err = xenbus_transaction_start(&xbt);
if (err) {
xenbus_dev_fatal(dev, err, "starting transaction");
return;
}
/* If we can't advertise it is OK. */
xen_blkbk_flush_diskcache(xbt, be, be->blkif->vbd.flush_support);
xen_blkbk_discard(xbt, be);
xen_blkbk_barrier(xbt, be, be->blkif->vbd.flush_support);
err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u", 1);
if (err) {
xenbus_dev_fatal(dev, err, "writing %s/feature-persistent",
dev->nodename);
goto abort;
}
err = xenbus_printf(xbt, dev->nodename, "feature-max-indirect-segments", "%u",
MAX_INDIRECT_SEGMENTS);
if (err)
dev_warn(&dev->dev, "writing %s/feature-max-indirect-segments (%d)",
dev->nodename, err);
err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
(unsigned long long)vbd_sz(&be->blkif->vbd));
if (err) {
xenbus_dev_fatal(dev, err, "writing %s/sectors",
dev->nodename);
goto abort;
}
/* FIXME: use a typename instead */
err = xenbus_printf(xbt, dev->nodename, "info", "%u",
be->blkif->vbd.type |
(be->blkif->vbd.readonly ? VDISK_READONLY : 0));
if (err) {
xenbus_dev_fatal(dev, err, "writing %s/info",
dev->nodename);
goto abort;
}
err = xenbus_printf(xbt, dev->nodename, "sector-size", "%lu",
(unsigned long)
bdev_logical_block_size(be->blkif->vbd.bdev));
if (err) {
xenbus_dev_fatal(dev, err, "writing %s/sector-size",
dev->nodename);
goto abort;
}
err = xenbus_printf(xbt, dev->nodename, "physical-sector-size", "%u",
bdev_physical_block_size(be->blkif->vbd.bdev));
if (err)
xenbus_dev_error(dev, err, "writing %s/physical-sector-size",
dev->nodename);
err = xenbus_transaction_end(xbt, 0);
if (err == -EAGAIN)
goto again;
if (err)
xenbus_dev_fatal(dev, err, "ending transaction");
err = xenbus_switch_state(dev, XenbusStateConnected);
if (err)
xenbus_dev_fatal(dev, err, "%s: switching to Connected state",
dev->nodename);
return;
abort:
xenbus_transaction_end(xbt, 1);
}
static int connect_ring(struct backend_info *be)
{
struct xenbus_device *dev = be->dev;
unsigned long ring_ref;
unsigned int evtchn;
unsigned int pers_grants;
char protocol[64] = "";
int err;
DPRINTK("%s", dev->otherend);
err = xenbus_gather(XBT_NIL, dev->otherend, "ring-ref", "%lu",
&ring_ref, "event-channel", "%u", &evtchn, NULL);
if (err) {
xenbus_dev_fatal(dev, err,
"reading %s/ring-ref and event-channel",
dev->otherend);
return err;
}
be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
err = xenbus_gather(XBT_NIL, dev->otherend, "protocol",
"%63s", protocol, NULL);
if (err)
strcpy(protocol, "unspecified, assuming native");
else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
else {
xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
return -1;
}
err = xenbus_gather(XBT_NIL, dev->otherend,
"feature-persistent", "%u",
&pers_grants, NULL);
if (err)
pers_grants = 0;
be->blkif->vbd.feature_gnt_persistent = pers_grants;
be->blkif->vbd.overflow_max_grants = 0;
pr_info(DRV_PFX "ring-ref %ld, event-channel %d, protocol %d (%s) %s\n",
ring_ref, evtchn, be->blkif->blk_protocol, protocol,
pers_grants ? "persistent grants" : "");
/* Map the shared frame, irq etc. */
err = xen_blkif_map(be->blkif, ring_ref, evtchn);
if (err) {
xenbus_dev_fatal(dev, err, "mapping ring-ref %lu port %u",
ring_ref, evtchn);
return err;
}
return 0;
}
/* ** Driver Registration ** */
static const struct xenbus_device_id xen_blkbk_ids[] = {
{ "vbd" },
{ "" }
};
static DEFINE_XENBUS_DRIVER(xen_blkbk, ,
.probe = xen_blkbk_probe,
.remove = xen_blkbk_remove,
.otherend_changed = frontend_changed
);
int xen_blkif_xenbus_init(void)
{
return xenbus_register_backend(&xen_blkbk_driver);
}
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