diff options
Diffstat (limited to 'drivers/block/xen-blkback/xenbus.c')
| -rw-r--r-- | drivers/block/xen-blkback/xenbus.c | 1178 |
1 files changed, 1178 insertions, 0 deletions
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c new file mode 100644 index 0000000000..bb66178c43 --- /dev/null +++ b/drivers/block/xen-blkback/xenbus.c @@ -0,0 +1,1178 @@ +// 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 <linux/module.h> +#include <linux/kthread.h> +#include <linux/pagemap.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 = sync_blockdev(blkif->vbd.bdev); + 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); + gnttab_page_cache_init(&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; +} + +/* Enable the persistent grants feature. */ +static bool feature_persistent = true; +module_param(feature_persistent, bool, 0644); +MODULE_PARM_DESC(feature_persistent, "Enables the persistent grants feature"); + +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->be->dev, + 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); + ring->xenblkd = NULL; + 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(ring->free_pages.num_pages != 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, NULL); + 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; + + 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 ? + BLK_OPEN_READ : BLK_OPEN_WRITE, NULL, 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 (cdrom || disk_to_cdi(vbd->bdev->bd_disk)) + vbd->type |= VDISK_CDROM; + if (vbd->bdev->bd_disk->flags & GENHD_FL_REMOVABLE) + vbd->type |= VDISK_REMOVABLE; + + if (bdev_write_cache(bdev)) + vbd->flush_support = true; + if (bdev_max_secure_erase_sectors(bdev)) + vbd->discard_secure = true; + + pr_debug("Successful creation of handle=%04x (dom=%u)\n", + handle, blkif->domid); + return 0; +} + +static void 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); + } +} + +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; + + if (!xenbus_read_unsigned(dev->nodename, "discard-enable", 1)) + return; + + if (bdev_max_discard_sectors(bdev)) { + err = xenbus_printf(xbt, dev->nodename, + "discard-granularity", "%u", + bdev_discard_granularity(bdev)); + if (err) { + dev_warn(&dev->dev, "writing discard-granularity (%d)", err); + return; + } + err = xenbus_printf(xbt, dev->nodename, + "discard-alignment", "%u", + bdev_discard_alignment(bdev)); + 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, NULL, + 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", + be->blkif->vbd.feature_gnt_persistent_parm); + 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]; + + if (blkif->multi_ref) + snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i); + else { + WARN_ON(i != 0); + snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref"); + } + + err = xenbus_scanf(XBT_NIL, dir, ring_ref_name, + "%u", &ring_ref[i]); + + if (err != 1) { + err = -EINVAL; + xenbus_dev_fatal(dev, err, "reading %s/%s", + dir, ring_ref_name); + return err; + } + } + + err = -ENOMEM; + for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) { + req = kzalloc(sizeof(*req), GFP_KERNEL); + if (!req) + goto fail; + list_add_tail(&req->free_list, &ring->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; + } + } + + /* Map the shared frame, irq etc. */ + err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn); + if (err) { + xenbus_dev_fatal(dev, err, "mapping ring-ref port %u", evtchn); + goto fail; + } + + return 0; + +fail: + 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++) { + 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); + } + return err; +} + +static int connect_ring(struct backend_info *be) +{ + struct xenbus_device *dev = be->dev; + struct xen_blkif *blkif = be->blkif; + char protocol[64] = ""; + int err, i; + char *xspath; + size_t xspathsize; + const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */ + unsigned int requested_num_queues = 0; + unsigned int ring_page_order; + + pr_debug("%s %s\n", __func__, dev->otherend); + + blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT; + err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol", + "%63s", protocol); + if (err <= 0) + strcpy(protocol, "unspecified, assuming default"); + else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE)) + blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE; + else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32)) + blkif->blk_protocol = BLKIF_PROTOCOL_X86_32; + else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64)) + blkif->blk_protocol = BLKIF_PROTOCOL_X86_64; + else { + xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol); + return -ENOSYS; + } + + blkif->vbd.feature_gnt_persistent_parm = feature_persistent; + blkif->vbd.feature_gnt_persistent = + blkif->vbd.feature_gnt_persistent_parm && + xenbus_read_unsigned(dev->otherend, "feature-persistent", 0); + + blkif->vbd.overflow_max_grants = 0; + + /* + * Read the number of hardware queues from frontend. + */ + requested_num_queues = xenbus_read_unsigned(dev->otherend, + "multi-queue-num-queues", + 1); + if (requested_num_queues > xenblk_max_queues + || requested_num_queues == 0) { + /* Buggy or malicious guest. */ + xenbus_dev_fatal(dev, err, + "guest requested %u queues, exceeding the maximum of %u.", + requested_num_queues, xenblk_max_queues); + return -ENOSYS; + } + blkif->nr_rings = requested_num_queues; + if (xen_blkif_alloc_rings(blkif)) + return -ENOMEM; + + pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename, + blkif->nr_rings, blkif->blk_protocol, protocol, + blkif->vbd.feature_gnt_persistent ? "persistent grants" : ""); + + err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u", + &ring_page_order); + if (err != 1) { + blkif->nr_ring_pages = 1; + blkif->multi_ref = false; + } else if (ring_page_order <= xen_blkif_max_ring_order) { + blkif->nr_ring_pages = 1 << ring_page_order; + blkif->multi_ref = true; + } else { + err = -EINVAL; + xenbus_dev_fatal(dev, err, + "requested ring page order %d exceed max:%d", + ring_page_order, + xen_blkif_max_ring_order); + return err; + } + + if (blkif->nr_rings == 1) + return read_per_ring_refs(&blkif->rings[0], dev->otherend); + else { + xspathsize = strlen(dev->otherend) + xenstore_path_ext_size; + xspath = kmalloc(xspathsize, GFP_KERNEL); + if (!xspath) { + xenbus_dev_fatal(dev, -ENOMEM, "reading ring references"); + return -ENOMEM; + } + + for (i = 0; i < blkif->nr_rings; i++) { + memset(xspath, 0, xspathsize); + snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i); + err = read_per_ring_refs(&blkif->rings[i], xspath); + if (err) { + kfree(xspath); + return err; + } + } + kfree(xspath); + } + return 0; +} + +static const struct xenbus_device_id xen_blkbk_ids[] = { + { "vbd" }, + { "" } +}; + +static struct xenbus_driver xen_blkbk_driver = { + .ids = xen_blkbk_ids, + .probe = xen_blkbk_probe, + .remove = xen_blkbk_remove, + .otherend_changed = frontend_changed, + .allow_rebind = true, + .reclaim_memory = reclaim_memory, +}; + +int xen_blkif_xenbus_init(void) +{ + return xenbus_register_backend(&xen_blkbk_driver); +} + +void xen_blkif_xenbus_fini(void) +{ + xenbus_unregister_driver(&xen_blkbk_driver); +} |