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xenbus.c
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xenbus.c
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// SPDX-License-Identifier: GPL-2.0-or-later
/* Xenbus code for blkif backend
Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
Copyright (C) 2005 XenSource Ltd
*/
#define pr_fmt(fmt) "xen-blkback: " fmt
#include <stdarg.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <xen/events.h>
#include <xen/grant_table.h>
#include "common.h"
/* On the XenBus the max length of 'ring-ref%u'. */
#define RINGREF_NAME_LEN (20)
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 *,
const char *);
static void xen_blkif_free(struct xen_blkif *blkif);
static void xen_vbd_free(struct xen_vbd *vbd);
struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
{
return be->dev;
}
/*
* The last request could free the device from softirq context and
* xen_blkif_free() can sleep.
*/
static void xen_blkif_deferred_free(struct work_struct *work)
{
struct xen_blkif *blkif;
blkif = container_of(work, struct xen_blkif, free_work);
xen_blkif_free(blkif);
}
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, "%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];
struct xen_blkif_ring *ring;
int i;
/* Not ready to connect? */
if (!blkif->rings || !blkif->rings[0].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);
for (i = 0; i < blkif->nr_rings; i++) {
ring = &blkif->rings[i];
ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s-%d", name, i);
if (IS_ERR(ring->xenblkd)) {
err = PTR_ERR(ring->xenblkd);
ring->xenblkd = NULL;
xenbus_dev_fatal(blkif->be->dev, err,
"start %s-%d xenblkd", name, i);
goto out;
}
}
return;
out:
while (--i >= 0) {
ring = &blkif->rings[i];
kthread_stop(ring->xenblkd);
}
return;
}
static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
{
unsigned int r;
blkif->rings = kcalloc(blkif->nr_rings, sizeof(struct xen_blkif_ring),
GFP_KERNEL);
if (!blkif->rings)
return -ENOMEM;
for (r = 0; r < blkif->nr_rings; r++) {
struct xen_blkif_ring *ring = &blkif->rings[r];
spin_lock_init(&ring->blk_ring_lock);
init_waitqueue_head(&ring->wq);
INIT_LIST_HEAD(&ring->pending_free);
INIT_LIST_HEAD(&ring->persistent_purge_list);
INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants);
spin_lock_init(&ring->free_pages_lock);
INIT_LIST_HEAD(&ring->free_pages);
spin_lock_init(&ring->pending_free_lock);
init_waitqueue_head(&ring->pending_free_wq);
init_waitqueue_head(&ring->shutdown_wq);
ring->blkif = blkif;
ring->st_print = jiffies;
ring->active = true;
}
return 0;
}
static struct xen_blkif *xen_blkif_alloc(domid_t domid)
{
struct xen_blkif *blkif;
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;
atomic_set(&blkif->refcnt, 1);
init_completion(&blkif->drain_complete);
/*
* Because freeing back to the cache may be deferred, it is not
* safe to unload the module (and hence destroy the cache) until
* this has completed. To prevent premature unloading, take an
* extra module reference here and release only when the object
* has been freed back to the cache.
*/
__module_get(THIS_MODULE);
INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
return blkif;
}
static int xen_blkif_map(struct xen_blkif_ring *ring, grant_ref_t *gref,
unsigned int nr_grefs, unsigned int evtchn)
{
int err;
struct xen_blkif *blkif = ring->blkif;
const struct blkif_common_sring *sring_common;
RING_IDX rsp_prod, req_prod;
unsigned int size;
/* Already connected through? */
if (ring->irq)
return 0;
err = xenbus_map_ring_valloc(blkif->be->dev, gref, nr_grefs,
&ring->blk_ring);
if (err < 0)
return err;
sring_common = (struct blkif_common_sring *)ring->blk_ring;
rsp_prod = READ_ONCE(sring_common->rsp_prod);
req_prod = READ_ONCE(sring_common->req_prod);
switch (blkif->blk_protocol) {
case BLKIF_PROTOCOL_NATIVE:
{
struct blkif_sring *sring_native =
(struct blkif_sring *)ring->blk_ring;
BACK_RING_ATTACH(&ring->blk_rings.native, sring_native,
rsp_prod, XEN_PAGE_SIZE * nr_grefs);
size = __RING_SIZE(sring_native, XEN_PAGE_SIZE * nr_grefs);
break;
}
case BLKIF_PROTOCOL_X86_32:
{
struct blkif_x86_32_sring *sring_x86_32 =
(struct blkif_x86_32_sring *)ring->blk_ring;
BACK_RING_ATTACH(&ring->blk_rings.x86_32, sring_x86_32,
rsp_prod, XEN_PAGE_SIZE * nr_grefs);
size = __RING_SIZE(sring_x86_32, XEN_PAGE_SIZE * nr_grefs);
break;
}
case BLKIF_PROTOCOL_X86_64:
{
struct blkif_x86_64_sring *sring_x86_64 =
(struct blkif_x86_64_sring *)ring->blk_ring;
BACK_RING_ATTACH(&ring->blk_rings.x86_64, sring_x86_64,
rsp_prod, XEN_PAGE_SIZE * nr_grefs);
size = __RING_SIZE(sring_x86_64, XEN_PAGE_SIZE * nr_grefs);
break;
}
default:
BUG();
}
err = -EIO;
if (req_prod - rsp_prod > size)
goto fail;
err = bind_interdomain_evtchn_to_irqhandler_lateeoi(blkif->domid,
evtchn, xen_blkif_be_int, 0, "blkif-backend", ring);
if (err < 0)
goto fail;
ring->irq = err;
return 0;
fail:
xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
ring->blk_rings.common.sring = NULL;
return err;
}
static int xen_blkif_disconnect(struct xen_blkif *blkif)
{
struct pending_req *req, *n;
unsigned int j, r;
bool busy = false;
for (r = 0; r < blkif->nr_rings; r++) {
struct xen_blkif_ring *ring = &blkif->rings[r];
unsigned int i = 0;
if (!ring->active)
continue;
if (ring->xenblkd) {
kthread_stop(ring->xenblkd);
wake_up(&ring->shutdown_wq);
}
/* The above kthread_stop() guarantees that at this point we
* don't have any discard_io or other_io requests. So, checking
* for inflight IO is enough.
*/
if (atomic_read(&ring->inflight) > 0) {
busy = true;
continue;
}
if (ring->irq) {
unbind_from_irqhandler(ring->irq, ring);
ring->irq = 0;
}
if (ring->blk_rings.common.sring) {
xenbus_unmap_ring_vfree(blkif->be->dev, ring->blk_ring);
ring->blk_rings.common.sring = NULL;
}
/* Remove all persistent grants and the cache of ballooned pages. */
xen_blkbk_free_caches(ring);
/* Check that there is no request in use */
list_for_each_entry_safe(req, n, &ring->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++;
}
BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0);
BUG_ON(!list_empty(&ring->persistent_purge_list));
BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
BUG_ON(!list_empty(&ring->free_pages));
BUG_ON(ring->free_pages_num != 0);
BUG_ON(ring->persistent_gnt_c != 0);
WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
ring->active = false;
}
if (busy)
return -EBUSY;
blkif->nr_ring_pages = 0;
/*
* blkif->rings was allocated in connect_ring, so we should free it in
* here.
*/
kfree(blkif->rings);
blkif->rings = NULL;
blkif->nr_rings = 0;
return 0;
}
static void xen_blkif_free(struct xen_blkif *blkif)
{
WARN_ON(xen_blkif_disconnect(blkif));
xen_vbd_free(&blkif->vbd);
kfree(blkif->be->mode);
kfree(blkif->be);
/* Make sure everything is drained before shutting down */
kmem_cache_free(xen_blkif_cachep, blkif);
module_put(THIS_MODULE);
}
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;
}
void xen_blkif_interface_fini(void)
{
kmem_cache_destroy(xen_blkif_cachep);
xen_blkif_cachep = NULL;
}
/*
* sysfs interface for VBD I/O requests
*/
#define VBD_SHOW_ALLRING(name, format) \
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); \
struct xen_blkif *blkif = be->blkif; \
unsigned int i; \
unsigned long long result = 0; \
\
if (!blkif->rings) \
goto out; \
\
for (i = 0; i < blkif->nr_rings; i++) { \
struct xen_blkif_ring *ring = &blkif->rings[i]; \
\
result += ring->st_##name; \
} \
\
out: \
return sprintf(buf, format, result); \
} \
static DEVICE_ATTR(name, 0444, show_##name, NULL)
VBD_SHOW_ALLRING(oo_req, "%llu\n");
VBD_SHOW_ALLRING(rd_req, "%llu\n");
VBD_SHOW_ALLRING(wr_req, "%llu\n");
VBD_SHOW_ALLRING(f_req, "%llu\n");
VBD_SHOW_ALLRING(ds_req, "%llu\n");
VBD_SHOW_ALLRING(rd_sect, "%llu\n");
VBD_SHOW_ALLRING(wr_sect, "%llu\n");
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 const struct attribute_group xen_vbdstat_group = {
.name = "statistics",
.attrs = xen_vbdstat_attrs,
};
#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, 0444, show_##name, NULL)
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)) {
pr_warn("xen_vbd_create: device %08x could not be opened\n",
vbd->pdevice);
return -ENOENT;
}
vbd->bdev = bdev;
if (vbd->bdev->bd_disk == NULL) {
pr_warn("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 && test_bit(QUEUE_FLAG_WC, &q->queue_flags))
vbd->flush_support = true;
if (q && blk_queue_secure_erase(q))
vbd->discard_secure = true;
pr_debug("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);
pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
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;
}
dev_set_drvdata(&dev->dev, NULL);
if (be->blkif) {
xen_blkif_disconnect(be->blkif);
/* Put the reference we set in xen_blkif_alloc(). */
xen_blkif_put(be->blkif);
}
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 (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1))
return;
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);
/* match the pr_debug in xen_blkbk_remove */
pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
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;
}
err = xenbus_printf(XBT_NIL, 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);
/* Multi-queue: advertise how many queues are supported by us.*/
err = xenbus_printf(XBT_NIL, dev->nodename,
"multi-queue-max-queues", "%u", xenblk_max_queues);
if (err)
pr_warn("Error writing multi-queue-max-queues\n");
/* 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_printf(XBT_NIL, dev->nodename, "max-ring-page-order", "%u",
xen_blkif_max_ring_order);
if (err)
pr_warn("%s write out 'max-ring-page-order' failed\n", __func__);
err = xenbus_switch_state(dev, XenbusStateInitWait);
if (err)
goto fail;
return 0;
fail:
pr_warn("%s failed\n", __func__);
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 *path, const char *token)
{
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;
pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id);
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("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 = kstrtoul(strrchr(dev->otherend, '/') + 1, 0, &handle);
if (err) {
kfree(be->mode);
be->mode = NULL;
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;
pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
switch (frontend_state) {
case XenbusStateInitialising:
if (dev->state == XenbusStateClosed) {
pr_info("%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.
*/
err = xen_blkif_disconnect(be->blkif);
if (err) {
xenbus_dev_fatal(dev, err, "pending I/O");
break;
}
err = connect_ring(be);
if (err) {
/*
* Clean up so that memory resources can be used by
* other devices. connect_ring reported already error.
*/
xen_blkif_disconnect(be->blkif);
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;
fallthrough;
/* 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;
}
}
/* Once a memory pressure is detected, squeeze free page pools for a while. */
static unsigned int buffer_squeeze_duration_ms = 10;
module_param_named(buffer_squeeze_duration_ms,
buffer_squeeze_duration_ms, int, 0644);
MODULE_PARM_DESC(buffer_squeeze_duration_ms,
"Duration in ms to squeeze pages buffer when a memory pressure is detected");
/*
* Callback received when the memory pressure is detected.
*/
static void reclaim_memory(struct xenbus_device *dev)
{
struct backend_info *be = dev_get_drvdata(&dev->dev);
if (!be)
return;
be->blkif->buffer_squeeze_end = jiffies +
msecs_to_jiffies(buffer_squeeze_duration_ms);
}
/* ** 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;
pr_debug("%s %s\n", __func__, 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, "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);
}
/*
* Each ring may have multi pages, depends on "ring-page-order".
*/
static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
{
unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
struct pending_req *req, *n;
int err, i, j;
struct xen_blkif *blkif = ring->blkif;
struct xenbus_device *dev = blkif->be->dev;
unsigned int nr_grefs, evtchn;
err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
&evtchn);
if (err != 1) {
err = -EINVAL;
xenbus_dev_fatal(dev, err, "reading %s/event-channel", dir);
return err;
}
nr_grefs = blkif->nr_ring_pages;
if (unlikely(!nr_grefs)) {
WARN_ON(true);
return -EINVAL;
}
for (i = 0; i < nr_grefs; i++) {
char ring_ref_name[RINGREF_NAME_LEN];
snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
"%u", &ring_ref[i]);
if (err != 1) {
if (nr_grefs == 1)
break;
err = -EINVAL;