The block device frontend driver allows the kernel to access block
devices exported exported by a virtual machine containing a physical
block device driver.
Signed-off-by: Ian Pratt <[email protected]>
Signed-off-by: Christian Limpach <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
---
drivers/block/Kconfig | 1
drivers/block/Makefile | 1
drivers/block/xen/Kconfig | 14
drivers/block/xen/Makefile | 5
drivers/block/xen/blkfront.c | 812 +++++++++++++++++++++++++++++++++++++++++++ drivers/block/xen/block.h | 155 ++++++++
drivers/block/xen/vbd.c | 214 +++++++++++
7 files changed, 1202 insertions(+)
===================================================================
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -461,6 +461,7 @@ config CDROM_PKTCDVD_WCACHE
don't do deferred write error handling yet.
source "drivers/s390/block/Kconfig"
+source "drivers/block/xen/Kconfig"
config ATA_OVER_ETH
tristate "ATA over Ethernet support"
===================================================================
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -30,3 +30,4 @@ obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_SX8) += sx8.o
obj-$(CONFIG_BLK_DEV_UB) += ub.o
+obj-$(CONFIG_XEN) += xen/
===================================================================
--- a/include/linux/major.h
+++ b/include/linux/major.h
@@ -156,6 +156,8 @@
#define VXSPEC_MAJOR 200 /* VERITAS volume config driver */
#define VXDMP_MAJOR 201 /* VERITAS volume multipath driver */
+#define XENVBD_MAJOR 202 /* Xen virtual block device */
+
#define MSR_MAJOR 202
#define CPUID_MAJOR 203
===================================================================
--- /dev/null
+++ b/drivers/block/xen/Kconfig
@@ -0,0 +1,14 @@
+menu "Xen block device drivers"
+ depends on XEN
+
+config XEN_BLKDEV_FRONTEND
+ tristate "Block device frontend driver"
+ depends on XEN
+ default y
+ help
+ The block device frontend driver allows the kernel to access block
+ devices exported from a device driver virtual machine. Unless you
+ are building a dedicated device driver virtual machine, then you
+ almost certainly want to say Y here.
+
+endmenu
===================================================================
--- /dev/null
+++ b/drivers/block/xen/Makefile
@@ -0,0 +1,5 @@
+
+obj-$(CONFIG_XEN_BLKDEV_FRONTEND) := xenblk.o
+
+xenblk-objs := blkfront.o vbd.o
+
===================================================================
--- /dev/null
+++ b/drivers/block/xen/blkfront.c
@@ -0,0 +1,870 @@
+/******************************************************************************
+ * blkfront.c
+ *
+ * XenLinux virtual block device driver.
+ *
+ * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
+ * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
+ * Copyright (c) 2004, Christian Limpach
+ * Copyright (c) 2004, Andrew Warfield
+ * Copyright (c) 2005, Christopher Clark
+ * 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 version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <linux/version.h>
+#include "block.h"
+#include <linux/cdrom.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <scsi/scsi.h>
+#include <xen/xenbus.h>
+#include <xen/interface/grant_table.h>
+#include <xen/grant_table.h>
+#include "../../../arch/i386/paravirt-xen/events.h"
+#include "../../../arch/i386/paravirt-xen/xen-page.h"
+#include <asm/hypervisor.h>
+
+#define BLKIF_STATE_DISCONNECTED 0
+#define BLKIF_STATE_CONNECTED 1
+#define BLKIF_STATE_SUSPENDED 2
+
+#define MAXIMUM_OUTSTANDING_BLOCK_REQS \
+ (BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
+#define GRANT_INVALID_REF 0
+
+static void connect(struct blkfront_info *);
+static void blkfront_closing(struct xenbus_device *);
+static int blkfront_remove(struct xenbus_device *);
+static int talk_to_backend(struct xenbus_device *, struct blkfront_info *);
+static int setup_blkring(struct xenbus_device *, struct blkfront_info *);
+
+static void kick_pending_request_queues(struct blkfront_info *);
+
+static irqreturn_t blkif_int(int irq, void *dev_id);
+static void blkif_restart_queue(struct work_struct *work);
+static void blkif_recover(struct blkfront_info *);
+static void blkif_completion(struct blk_shadow *);
+static void blkif_free(struct blkfront_info *, int);
+
+
+/**
+ * Entry point to this code when a new device is created. Allocate the basic
+ * structures and the ring buffer for communication with the backend, and
+ * inform the backend of the appropriate details for those. Switch to
+ * Initialised state.
+ */
+static int blkfront_probe(struct xenbus_device *dev,
+ const struct xenbus_device_id *id)
+{
+ int err, vdevice, i;
+ struct blkfront_info *info;
+
+ /* FIXME: Use dynamic device id if this is not set. */
+ err = xenbus_scanf(XBT_NIL, dev->nodename,
+ "virtual-device", "%i", &vdevice);
+ if (err != 1) {
+ xenbus_dev_fatal(dev, err, "reading virtual-device");
+ return err;
+ }
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info) {
+ xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
+ return -ENOMEM;
+ }
+
+ info->xbdev = dev;
+ info->vdevice = vdevice;
+ info->connected = BLKIF_STATE_DISCONNECTED;
+ INIT_WORK(&info->work, blkif_restart_queue);
+
+ for (i = 0; i < BLK_RING_SIZE; i++)
+ info->shadow[i].req.id = i+1;
+ info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+
+ /* Front end dir is a number, which is used as the id. */
+ info->handle = simple_strtoul(strrchr(dev->nodename,'/')+1, NULL, 0);
+ dev->dev.driver_data = info;
+
+ err = talk_to_backend(dev, info);
+ if (err) {
+ kfree(info);
+ dev->dev.driver_data = NULL;
+ return err;
+ }
+
+ return 0;
+}
+
+
+/**
+ * We are reconnecting to the backend, due to a suspend/resume, or a backend
+ * driver restart. We tear down our blkif structure and recreate it, but
+ * leave the device-layer structures intact so that this is transparent to the
+ * rest of the kernel.
+ */
+static int blkfront_resume(struct xenbus_device *dev)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+ int err;
+
+ DPRINTK("blkfront_resume: %s\n", dev->nodename);
+
+ blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
+
+ err = talk_to_backend(dev, info);
+ if (info->connected == BLKIF_STATE_SUSPENDED && !err)
+ blkif_recover(info);
+
+ return err;
+}
+
+
+/* Common code used when first setting up, and when resuming. */
+static int talk_to_backend(struct xenbus_device *dev,
+ struct blkfront_info *info)
+{
+ const char *message = NULL;
+ struct xenbus_transaction xbt;
+ int err;
+
+ /* Create shared ring, alloc event channel. */
+ err = setup_blkring(dev, info);
+ if (err)
+ goto out;
+
+again:
+ err = xenbus_transaction_start(&xbt);
+ if (err) {
+ xenbus_dev_fatal(dev, err, "starting transaction");
+ goto destroy_blkring;
+ }
+
+ err = xenbus_printf(xbt, dev->nodename,
+ "ring-ref","%u", info->ring_ref);
+ if (err) {
+ message = "writing ring-ref";
+ goto abort_transaction;
+ }
+ err = xenbus_printf(xbt, dev->nodename,
+ "event-channel", "%u", info->evtchn);
+ if (err) {
+ message = "writing event-channel";
+ goto abort_transaction;
+ }
+
+ err = xenbus_transaction_end(xbt, 0);
+ if (err) {
+ if (err == -EAGAIN)
+ goto again;
+ xenbus_dev_fatal(dev, err, "completing transaction");
+ goto destroy_blkring;
+ }
+
+ xenbus_switch_state(dev, XenbusStateInitialised);
+
+ return 0;
+
+ abort_transaction:
+ xenbus_transaction_end(xbt, 1);
+ if (message)
+ xenbus_dev_fatal(dev, err, "%s", message);
+ destroy_blkring:
+ blkif_free(info, 0);
+ out:
+ return err;
+}
+
+
+static int setup_blkring(struct xenbus_device *dev,
+ struct blkfront_info *info)
+{
+ struct blkif_sring *sring;
+ int err;
+
+ info->ring_ref = GRANT_INVALID_REF;
+
+ sring = (struct blkif_sring *)__get_free_page(GFP_KERNEL);
+ if (!sring) {
+ xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
+ return -ENOMEM;
+ }
+ SHARED_RING_INIT(sring);
+ FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+
+ err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
+ if (err < 0) {
+ free_page((unsigned long)sring);
+ info->ring.sring = NULL;
+ goto fail;
+ }
+ info->ring_ref = err;
+
+ err = xenbus_alloc_evtchn(dev, &info->evtchn);
+ if (err)
+ goto fail;
+
+ err = bind_evtchn_to_irqhandler(
+ info->evtchn, blkif_int, SA_SAMPLE_RANDOM, "blkif", info);
+ if (err <= 0) {
+ xenbus_dev_fatal(dev, err,
+ "bind_evtchn_to_irqhandler failed");
+ goto fail;
+ }
+ info->irq = err;
+
+ return 0;
+fail:
+ blkif_free(info, 0);
+ return err;
+}
+
+
+/**
+ * Callback received when the backend's state changes.
+ */
+static void backend_changed(struct xenbus_device *dev,
+ enum xenbus_state backend_state)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+ struct block_device *bd;
+
+ DPRINTK("blkfront:backend_changed.\n");
+
+ switch (backend_state) {
+ case XenbusStateInitialising:
+ case XenbusStateInitWait:
+ case XenbusStateInitialised:
+ case XenbusStateUnknown:
+ case XenbusStateClosed:
+ break;
+
+ case XenbusStateConnected:
+ connect(info);
+ break;
+
+ case XenbusStateClosing:
+ bd = bdget(info->dev);
+ if (bd == NULL)
+ xenbus_dev_fatal(dev, -ENODEV, "bdget failed");
+
+ mutex_lock(&bd->bd_mutex);
+ if (info->users > 0)
+ xenbus_dev_error(dev, -EBUSY,
+ "Device in use; refusing to close");
+ else
+ blkfront_closing(dev);
+ mutex_unlock(&bd->bd_mutex);
+ bdput(bd);
+ break;
+ }
+}
+
+
+/* ** Connection ** */
+
+
+/*
+ * Invoked when the backend is finally 'ready' (and has told produced
+ * the details about the physical device - #sectors, size, etc).
+ */
+static void connect(struct blkfront_info *info)
+{
+ unsigned long long sectors;
+ unsigned long sector_size;
+ unsigned int binfo;
+ int err;
+
+ if ((info->connected == BLKIF_STATE_CONNECTED) ||
+ (info->connected == BLKIF_STATE_SUSPENDED) )
+ return;
+
+ DPRINTK("blkfront.c:connect:%s.\n", info->xbdev->otherend);
+
+ err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+ "sectors", "%llu", §ors,
+ "info", "%u", &binfo,
+ "sector-size", "%lu", §or_size,
+ NULL);
+ if (err) {
+ xenbus_dev_fatal(info->xbdev, err,
+ "reading backend fields at %s",
+ info->xbdev->otherend);
+ return;
+ }
+
+ err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+ "feature-barrier", "%lu", &info->feature_barrier,
+ NULL);
+ if (err)
+ info->feature_barrier = 0;
+
+ err = xlvbd_add(sectors, info->vdevice, binfo, sector_size, info);
+ if (err) {
+ xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
+ info->xbdev->otherend);
+ return;
+ }
+
+ (void)xenbus_switch_state(info->xbdev, XenbusStateConnected);
+
+ /* Kick pending requests. */
+ spin_lock_irq(&blkif_io_lock);
+ info->connected = BLKIF_STATE_CONNECTED;
+ kick_pending_request_queues(info);
+ spin_unlock_irq(&blkif_io_lock);
+
+ add_disk(info->gd);
+}
+
+/**
+ * Handle the change of state of the backend to Closing. We must delete our
+ * device-layer structures now, to ensure that writes are flushed through to
+ * the backend. Once is this done, we can switch to Closed in
+ * acknowledgement.
+ */
+static void blkfront_closing(struct xenbus_device *dev)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+ unsigned long flags;
+
+ DPRINTK("blkfront_closing: %s removed\n", dev->nodename);
+
+ if (info->rq == NULL)
+ goto out;
+
+ spin_lock_irqsave(&blkif_io_lock, flags);
+ /* No more blkif_request(). */
+ blk_stop_queue(info->rq);
+ /* No more gnttab callback work. */
+ gnttab_cancel_free_callback(&info->callback);
+ spin_unlock_irqrestore(&blkif_io_lock, flags);
+
+ /* Flush gnttab callback work. Must be done with no locks held. */
+ flush_scheduled_work();
+
+ xlvbd_del(info);
+
+ out:
+ xenbus_frontend_closed(dev);
+}
+
+
+static int blkfront_remove(struct xenbus_device *dev)
+{
+ struct blkfront_info *info = dev->dev.driver_data;
+
+ DPRINTK("blkfront_remove: %s removed\n", dev->nodename);
+
+ blkif_free(info, 0);
+
+ kfree(info);
+
+ return 0;
+}
+
+
+static inline int GET_ID_FROM_FREELIST(
+ struct blkfront_info *info)
+{
+ unsigned long free = info->shadow_free;
+ BUG_ON(free > BLK_RING_SIZE);
+ info->shadow_free = info->shadow[free].req.id;
+ info->shadow[free].req.id = 0x0fffffee; /* debug */
+ return free;
+}
+
+static inline void ADD_ID_TO_FREELIST(
+ struct blkfront_info *info, unsigned long id)
+{
+ info->shadow[id].req.id = info->shadow_free;
+ info->shadow[id].request = 0;
+ info->shadow_free = id;
+}
+
+static inline void flush_requests(struct blkfront_info *info)
+{
+ int notify;
+
+ RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->ring, notify);
+
+ if (notify)
+ notify_remote_via_irq(info->irq);
+}
+
+static void kick_pending_request_queues(struct blkfront_info *info)
+{
+ if (!RING_FULL(&info->ring)) {
+ /* Re-enable calldowns. */
+ blk_start_queue(info->rq);
+ /* Kick things off immediately. */
+ do_blkif_request(info->rq);
+ }
+}
+
+static void blkif_restart_queue(struct work_struct *work)
+{
+ struct blkfront_info *info = container_of(work, struct blkfront_info, work);
+
+ spin_lock_irq(&blkif_io_lock);
+ if (info->connected == BLKIF_STATE_CONNECTED)
+ kick_pending_request_queues(info);
+ spin_unlock_irq(&blkif_io_lock);
+}
+
+static void blkif_restart_queue_callback(void *arg)
+{
+ struct blkfront_info *info = (struct blkfront_info *)arg;
+ schedule_work(&info->work);
+}
+
+int blkif_open(struct inode *inode, struct file *filep)
+{
+ struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
+ info->users++;
+ return 0;
+}
+
+
+int blkif_release(struct inode *inode, struct file *filep)
+{
+ struct blkfront_info *info = inode->i_bdev->bd_disk->private_data;
+ info->users--;
+ if (info->users == 0) {
+ /* Check whether we have been instructed to close. We will
+ have ignored this request initially, as the device was
+ still mounted. */
+ struct xenbus_device * dev = info->xbdev;
+ enum xenbus_state state = xenbus_read_driver_state(dev->otherend);
+
+ if (state == XenbusStateClosing)
+ blkfront_closing(dev);
+ }
+ return 0;
+}
+
+
+int blkif_ioctl(struct inode *inode, struct file *filep,
+ unsigned command, unsigned long argument)
+{
+ int i;
+
+ DPRINTK_IOCTL("command: 0x%x, argument: 0x%lx, dev: 0x%04x\n",
+ command, (long)argument, inode->i_rdev);
+
+ switch (command) {
+ case CDROMMULTISESSION:
+ DPRINTK("FIXME: support multisession CDs later\n");
+ for (i = 0; i < sizeof(struct cdrom_multisession); i++)
+ if (put_user(0, (char __user *)(argument + i)))
+ return -EFAULT;
+ return 0;
+
+ default:
+ /*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
+ command);*/
+ return -EINVAL; /* same return as native Linux */
+ }
+
+ return 0;
+}
+
+
+int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
+{
+ /* We don't have real geometry info, but let's at least return
+ values consistent with the size of the device */
+ sector_t nsect = get_capacity(bd->bd_disk);
+ sector_t cylinders = nsect;
+
+ hg->heads = 0xff;
+ hg->sectors = 0x3f;
+ sector_div(cylinders, hg->heads * hg->sectors);
+ hg->cylinders = cylinders;
+ if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
+ hg->cylinders = 0xffff;
+ return 0;
+}
+
+/*
+ * blkif_queue_request
+ *
+ * request block io
+ *
+ * id: for guest use only.
+ * operation: BLKIF_OP_{READ,WRITE,PROBE}
+ * buffer: buffer to read/write into. this should be a
+ * virtual address in the guest os.
+ */
+static int blkif_queue_request(struct request *req)
+{
+ struct blkfront_info *info = req->rq_disk->private_data;
+ unsigned long buffer_mfn;
+ struct blkif_request *ring_req;
+ struct bio *bio;
+ struct bio_vec *bvec;
+ int idx;
+ unsigned long id;
+ unsigned int fsect, lsect;
+ int ref;
+ grant_ref_t gref_head;
+
+ if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
+ return 1;
+
+ if (gnttab_alloc_grant_references(
+ BLKIF_MAX_SEGMENTS_PER_REQUEST, &gref_head) < 0) {
+ gnttab_request_free_callback(
+ &info->callback,
+ blkif_restart_queue_callback,
+ info,
+ BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ return 1;
+ }
+
+ /* Fill out a communications ring structure. */
+ ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
+ id = GET_ID_FROM_FREELIST(info);
+ info->shadow[id].request = (unsigned long)req;
+
+ ring_req->id = id;
+ ring_req->sector_number = (blkif_sector_t)req->sector;
+ ring_req->handle = info->handle;
+
+ ring_req->operation = rq_data_dir(req) ?
+ BLKIF_OP_WRITE : BLKIF_OP_READ;
+ if (blk_barrier_rq(req))
+ ring_req->operation = BLKIF_OP_WRITE_BARRIER;
+
+ ring_req->nr_segments = 0;
+ rq_for_each_bio (bio, req) {
+ bio_for_each_segment (bvec, bio, idx) {
+ BUG_ON(ring_req->nr_segments
+ == BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ buffer_mfn = pfn_to_mfn(page_to_pfn(bvec->bv_page));
+ fsect = bvec->bv_offset >> 9;
+ lsect = fsect + (bvec->bv_len >> 9) - 1;
+ /* install a grant reference. */
+ ref = gnttab_claim_grant_reference(&gref_head);
+ BUG_ON(ref == -ENOSPC);
+
+ gnttab_grant_foreign_access_ref(
+ ref,
+ info->xbdev->otherend_id,
+ buffer_mfn,
+ rq_data_dir(req) );
+
+ info->shadow[id].frame[ring_req->nr_segments] =
+ mfn_to_pfn(buffer_mfn);
+
+ ring_req->seg[ring_req->nr_segments] =
+ (struct blkif_request_segment) {
+ .gref = ref,
+ .first_sect = fsect,
+ .last_sect = lsect };
+
+ ring_req->nr_segments++;
+ }
+ }
+
+ info->ring.req_prod_pvt++;
+
+ /* Keep a private copy so we can reissue requests when recovering. */
+ info->shadow[id].req = *ring_req;
+
+ gnttab_free_grant_references(gref_head);
+
+ return 0;
+}
+
+/*
+ * do_blkif_request
+ * read a block; request is in a request queue
+ */
+void do_blkif_request(request_queue_t *rq)
+{
+ struct blkfront_info *info = NULL;
+ struct request *req;
+ int queued;
+
+ DPRINTK("Entered do_blkif_request\n");
+
+ queued = 0;
+
+ while ((req = elv_next_request(rq)) != NULL) {
+ info = req->rq_disk->private_data;
+ if (!blk_fs_request(req)) {
+ end_request(req, 0);
+ continue;
+ }
+
+ if (RING_FULL(&info->ring))
+ goto wait;
+
+ DPRINTK("do_blk_req %p: cmd %p, sec %lx, "
+ "(%u/%li) buffer:%p [%s]\n",
+ req, req->cmd, (unsigned long)req->sector,
+ req->current_nr_sectors,
+ req->nr_sectors, req->buffer,
+ rq_data_dir(req) ? "write" : "read");
+
+
+ blkdev_dequeue_request(req);
+ if (blkif_queue_request(req)) {
+ blk_requeue_request(rq, req);
+ wait:
+ /* Avoid pointless unplugs. */
+ blk_stop_queue(rq);
+ break;
+ }
+
+ queued++;
+ }
+
+ if (queued != 0)
+ flush_requests(info);
+}
+
+
+static irqreturn_t blkif_int(int irq, void *dev_id)
+{
+ struct request *req;
+ struct blkif_response *bret;
+ RING_IDX i, rp;
+ unsigned long flags;
+ struct blkfront_info *info = (struct blkfront_info *)dev_id;
+ int uptodate;
+
+ spin_lock_irqsave(&blkif_io_lock, flags);
+
+ if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
+ spin_unlock_irqrestore(&blkif_io_lock, flags);
+ return IRQ_HANDLED;
+ }
+
+ again:
+ rp = info->ring.sring->rsp_prod;
+ rmb(); /* Ensure we see queued responses up to 'rp'. */
+
+ for (i = info->ring.rsp_cons; i != rp; i++) {
+ unsigned long id;
+ int ret;
+
+ bret = RING_GET_RESPONSE(&info->ring, i);
+ id = bret->id;
+ req = (struct request *)info->shadow[id].request;
+
+ blkif_completion(&info->shadow[id]);
+
+ ADD_ID_TO_FREELIST(info, id);
+
+ uptodate = (bret->status == BLKIF_RSP_OKAY);
+ switch (bret->operation) {
+ case BLKIF_OP_WRITE_BARRIER:
+ if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
+ printk("blkfront: %s: write barrier op failed\n",
+ info->gd->disk_name);
+ uptodate = -EOPNOTSUPP;
+ info->feature_barrier = 0;
+ xlvbd_barrier(info);
+ }
+ /* fall through */
+ case BLKIF_OP_READ:
+ case BLKIF_OP_WRITE:
+ if (unlikely(bret->status != BLKIF_RSP_OKAY))
+ DPRINTK("Bad return from blkdev data "
+ "request: %x\n", bret->status);
+
+ ret = end_that_request_first(req, uptodate,
+ req->hard_nr_sectors);
+ BUG_ON(ret);
+ end_that_request_last(req, uptodate);
+ break;
+ default:
+ BUG();
+ }
+ }
+
+ info->ring.rsp_cons = i;
+
+ if (i != info->ring.req_prod_pvt) {
+ int more_to_do;
+ RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
+ if (more_to_do)
+ goto again;
+ } else
+ info->ring.sring->rsp_event = i + 1;
+
+ kick_pending_request_queues(info);
+
+ spin_unlock_irqrestore(&blkif_io_lock, flags);
+
+ return IRQ_HANDLED;
+}
+
+static void blkif_free(struct blkfront_info *info, int suspend)
+{
+ /* Prevent new requests being issued until we fix things up. */
+ spin_lock_irq(&blkif_io_lock);
+ info->connected = suspend ?
+ BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
+ /* No more blkif_request(). */
+ if (info->rq)
+ blk_stop_queue(info->rq);
+ /* No more gnttab callback work. */
+ gnttab_cancel_free_callback(&info->callback);
+ spin_unlock_irq(&blkif_io_lock);
+
+ /* Flush gnttab callback work. Must be done with no locks held. */
+ flush_scheduled_work();
+
+ /* Free resources associated with old device channel. */
+ if (info->ring_ref != GRANT_INVALID_REF) {
+ gnttab_end_foreign_access(info->ring_ref, 0,
+ (unsigned long)info->ring.sring);
+ info->ring_ref = GRANT_INVALID_REF;
+ info->ring.sring = NULL;
+ }
+ if (info->irq)
+ unbind_from_irqhandler(info->irq, info);
+ info->evtchn = info->irq = 0;
+
+}
+
+static void blkif_completion(struct blk_shadow *s)
+{
+ int i;
+ for (i = 0; i < s->req.nr_segments; i++)
+ gnttab_end_foreign_access(s->req.seg[i].gref, 0, 0UL);
+}
+
+static void blkif_recover(struct blkfront_info *info)
+{
+ int i;
+ struct blkif_request *req;
+ struct blk_shadow *copy;
+ int j;
+
+ /* Stage 1: Make a safe copy of the shadow state. */
+ copy = kmalloc(sizeof(info->shadow), GFP_KERNEL | __GFP_NOFAIL);
+ memcpy(copy, info->shadow, sizeof(info->shadow));
+
+ /* Stage 2: Set up free list. */
+ memset(&info->shadow, 0, sizeof(info->shadow));
+ for (i = 0; i < BLK_RING_SIZE; i++)
+ info->shadow[i].req.id = i+1;
+ info->shadow_free = info->ring.req_prod_pvt;
+ info->shadow[BLK_RING_SIZE-1].req.id = 0x0fffffff;
+
+ /* Stage 3: Find pending requests and requeue them. */
+ for (i = 0; i < BLK_RING_SIZE; i++) {
+ /* Not in use? */
+ if (copy[i].request == 0)
+ continue;
+
+ /* Grab a request slot and copy shadow state into it. */
+ req = RING_GET_REQUEST(
+ &info->ring, info->ring.req_prod_pvt);
+ *req = copy[i].req;
+
+ /* We get a new request id, and must reset the shadow state. */
+ req->id = GET_ID_FROM_FREELIST(info);
+ memcpy(&info->shadow[req->id], ©[i], sizeof(copy[i]));
+
+ /* Rewrite any grant references invalidated by susp/resume. */
+ for (j = 0; j < req->nr_segments; j++)
+ gnttab_grant_foreign_access_ref(
+ req->seg[j].gref,
+ info->xbdev->otherend_id,
+ pfn_to_mfn(info->shadow[req->id].frame[j]),
+ rq_data_dir(
+ (struct request *)
+ info->shadow[req->id].request));
+ info->shadow[req->id].req = *req;
+
+ info->ring.req_prod_pvt++;
+ }
+
+ kfree(copy);
+
+ (void)xenbus_switch_state(info->xbdev, XenbusStateConnected);
+
+ spin_lock_irq(&blkif_io_lock);
+
+ /* Now safe for us to use the shared ring */
+ info->connected = BLKIF_STATE_CONNECTED;
+
+ /* Send off requeued requests */
+ flush_requests(info);
+
+ /* Kick any other new requests queued since we resumed */
+ kick_pending_request_queues(info);
+
+ spin_unlock_irq(&blkif_io_lock);
+}
+
+
+/* ** Driver Registration ** */
+
+
+static struct xenbus_device_id blkfront_ids[] = {
+ { "vbd" },
+ { "" }
+};
+
+
+static struct xenbus_driver blkfront = {
+ .name = "vbd",
+ .owner = THIS_MODULE,
+ .ids = blkfront_ids,
+ .probe = blkfront_probe,
+ .remove = blkfront_remove,
+ .resume = blkfront_resume,
+ .otherend_changed = backend_changed,
+};
+
+
+static int __init xlblk_init(void)
+{
+ if (!is_running_on_xen())
+ return -ENODEV;
+
+ if (xlvbd_alloc_major() < 0)
+ return -ENODEV;
+
+ return xenbus_register_frontend(&blkfront);
+}
+module_init(xlblk_init);
+
+
+static void xlblk_exit(void)
+{
+ return xenbus_unregister_driver(&blkfront);
+}
+module_exit(xlblk_exit);
+
+MODULE_LICENSE("Dual BSD/GPL");
===================================================================
--- /dev/null
+++ b/drivers/block/xen/block.h
@@ -0,0 +1,157 @@
+/******************************************************************************
+ * block.h
+ *
+ * Shared definitions between all levels of XenLinux Virtual block devices.
+ *
+ * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
+ * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
+ * Copyright (c) 2004-2005, Christian Limpach
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef __XEN_DRIVERS_BLOCK_H__
+#define __XEN_DRIVERS_BLOCK_H__
+
+#include <linux/version.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/hdreg.h>
+#include <linux/blkdev.h>
+#include <linux/major.h>
+#include <asm/hypervisor.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/io/blkif.h>
+#include <xen/interface/io/ring.h>
+#include <asm/io.h>
+#include <asm/atomic.h>
+#include <asm/uaccess.h>
+
+#if 1
+#define IPRINTK(fmt, args...) \
+ printk(KERN_INFO "xen_blk: " fmt, ##args)
+#else
+#define IPRINTK(fmt, args...) ((void)0)
+#endif
+
+#if 1
+#define WPRINTK(fmt, args...) \
+ printk(KERN_WARNING "xen_blk: " fmt, ##args)
+#else
+#define WPRINTK(fmt, args...) ((void)0)
+#endif
+
+#define DPRINTK(_f, _a...) pr_debug(_f, ## _a)
+
+#if 0
+#define DPRINTK_IOCTL(_f, _a...) printk(KERN_ALERT _f, ## _a)
+#else
+#define DPRINTK_IOCTL(_f, _a...) ((void)0)
+#endif
+
+struct xlbd_type_info
+{
+ int partn_shift;
+ int disks_per_major;
+ char *devname;
+ char *diskname;
+};
+
+struct xlbd_major_info
+{
+ int major;
+ int index;
+ int usage;
+ struct xlbd_type_info *type;
+};
+
+struct blk_shadow {
+ struct blkif_request req;
+ unsigned long request;
+ unsigned long frame[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+};
+
+#define BLK_RING_SIZE __RING_SIZE((struct blkif_sring *)0, PAGE_SIZE)
+
+/*
+ * We have one of these per vbd, whether ide, scsi or 'other'. They
+ * hang in private_data off the gendisk structure. We may end up
+ * putting all kinds of interesting stuff here :-)
+ */
+struct blkfront_info
+{
+ struct xenbus_device *xbdev;
+ dev_t dev;
+ struct gendisk *gd;
+ int vdevice;
+ blkif_vdev_t handle;
+ int connected;
+ int ring_ref;
+ struct blkif_front_ring ring;
+ unsigned int evtchn, irq;
+ struct xlbd_major_info *mi;
+ request_queue_t *rq;
+ struct work_struct work;
+ struct gnttab_free_callback callback;
+ struct blk_shadow shadow[BLK_RING_SIZE];
+ unsigned long shadow_free;
+ int feature_barrier;
+
+ /**
+ * The number of people holding this device open. We won't allow a
+ * hot-unplug unless this is 0.
+ */
+ int users;
+};
+
+extern spinlock_t blkif_io_lock;
+
+extern int blkif_open(struct inode *inode, struct file *filep);
+extern int blkif_release(struct inode *inode, struct file *filep);
+extern int blkif_ioctl(struct inode *inode, struct file *filep,
+ unsigned command, unsigned long argument);
+extern int blkif_getgeo(struct block_device *, struct hd_geometry *);
+extern int blkif_check(dev_t dev);
+extern int blkif_revalidate(dev_t dev);
+extern void do_blkif_request (request_queue_t *rq);
+
+/* Virtual block device subsystem. */
+int xlvbd_alloc_major(void);
+/* Note that xlvbd_add doesn't call add_disk for you: you're expected
+ to call add_disk on info->gd once the disk is properly connected
+ up. */
+int xlvbd_add(blkif_sector_t capacity, int device,
+ u16 vdisk_info, u16 sector_size, struct blkfront_info *info);
+void xlvbd_del(struct blkfront_info *info);
+int xlvbd_barrier(struct blkfront_info *info);
+
+#endif /* __XEN_DRIVERS_BLOCK_H__ */
===================================================================
--- /dev/null
+++ b/drivers/block/xen/vbd.c
@@ -0,0 +1,231 @@
+/******************************************************************************
+ * vbd.c
+ *
+ * XenLinux virtual block device driver (xvd).
+ *
+ * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
+ * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
+ * Copyright (c) 2004-2005, Christian Limpach
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "block.h"
+#include <linux/blkdev.h>
+#include <linux/list.h>
+
+#define BLKIF_MAJOR(dev) ((dev)>>8)
+#define BLKIF_MINOR(dev) ((dev) & 0xff)
+
+static struct xlbd_type_info xvd_type_info = {
+ .partn_shift = 4,
+ .disks_per_major = 16,
+ .devname = "xvd",
+ .diskname = "xvd"
+};
+
+static struct xlbd_major_info xvd_major_info = {
+ .major = XENVBD_MAJOR,
+ .type = &xvd_type_info
+};
+
+/* Information about our VBDs. */
+#define MAX_VBDS 64
+static LIST_HEAD(vbds_list);
+
+static struct block_device_operations xlvbd_block_fops =
+{
+ .owner = THIS_MODULE,
+ .open = blkif_open,
+ .release = blkif_release,
+ .ioctl = blkif_ioctl,
+ .getgeo = blkif_getgeo
+};
+
+DEFINE_SPINLOCK(blkif_io_lock);
+
+int
+xlvbd_alloc_major(void)
+{
+ printk("Registering block device major %i\n", xvd_major_info.major);
+ if (register_blkdev(xvd_major_info.major,
+ xvd_major_info.type->devname)) {
+ WPRINTK("can't get major %d with name %s\n",
+ xvd_major_info.major, xvd_major_info.type->devname);
+ return -1;
+ }
+ return 0;
+}
+
+static int
+xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
+{
+ request_queue_t *rq;
+
+ rq = blk_init_queue(do_blkif_request, &blkif_io_lock);
+ if (rq == NULL)
+ return -1;
+
+ elevator_init(rq, "noop");
+
+ /* Hard sector size and max sectors impersonate the equiv. hardware. */
+ blk_queue_hardsect_size(rq, sector_size);
+ blk_queue_max_sectors(rq, 512);
+
+ /* Each segment in a request is up to an aligned page in size. */
+ blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
+ blk_queue_max_segment_size(rq, PAGE_SIZE);
+
+ /* Ensure a merged request will fit in a single I/O ring slot. */
+ blk_queue_max_phys_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+ blk_queue_max_hw_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
+
+ /* Make sure buffer addresses are sector-aligned. */
+ blk_queue_dma_alignment(rq, 511);
+
+ gd->queue = rq;
+
+ return 0;
+}
+
+static int
+xlvbd_alloc_gendisk(int minor, blkif_sector_t capacity, int vdevice,
+ u16 vdisk_info, u16 sector_size,
+ struct blkfront_info *info)
+{
+ struct gendisk *gd;
+ struct xlbd_major_info *mi;
+ int nr_minors = 1;
+ int err = -ENODEV;
+
+ BUG_ON(info->gd != NULL);
+ BUG_ON(info->mi != NULL);
+ BUG_ON(info->rq != NULL);
+
+ mi = &xvd_major_info;
+ info->mi = mi;
+
+ if ((minor & ((1 << mi->type->partn_shift) - 1)) == 0)
+ nr_minors = 1 << mi->type->partn_shift;
+
+ gd = alloc_disk(nr_minors);
+ if (gd == NULL)
+ goto out;
+
+ if (nr_minors > 1)
+ sprintf(gd->disk_name, "%s%c", mi->type->diskname,
+ 'a' + mi->index * mi->type->disks_per_major +
+ (minor >> mi->type->partn_shift));
+ else
+ sprintf(gd->disk_name, "%s%c%d", mi->type->diskname,
+ 'a' + mi->index * mi->type->disks_per_major +
+ (minor >> mi->type->partn_shift),
+ minor & ((1 << mi->type->partn_shift) - 1));
+
+ gd->major = mi->major;
+ gd->first_minor = minor;
+ gd->fops = &xlvbd_block_fops;
+ gd->private_data = info;
+ gd->driverfs_dev = &(info->xbdev->dev);
+ set_capacity(gd, capacity);
+
+ if (xlvbd_init_blk_queue(gd, sector_size)) {
+ del_gendisk(gd);
+ goto out;
+ }
+
+ info->rq = gd->queue;
+ info->gd = gd;
+
+ if (info->feature_barrier)
+ xlvbd_barrier(info);
+
+ if (vdisk_info & VDISK_READONLY)
+ set_disk_ro(gd, 1);
+
+ if (vdisk_info & VDISK_REMOVABLE)
+ gd->flags |= GENHD_FL_REMOVABLE;
+
+ if (vdisk_info & VDISK_CDROM)
+ gd->flags |= GENHD_FL_CD;
+
+ return 0;
+
+ out:
+ info->mi = NULL;
+ return err;
+}
+
+int
+xlvbd_add(blkif_sector_t capacity, int vdevice, u16 vdisk_info,
+ u16 sector_size, struct blkfront_info *info)
+{
+ struct block_device *bd;
+ int err = 0;
+
+ info->dev = MKDEV(BLKIF_MAJOR(vdevice), BLKIF_MINOR(vdevice));
+
+ bd = bdget(info->dev);
+ if (bd == NULL)
+ return -ENODEV;
+
+ err = xlvbd_alloc_gendisk(BLKIF_MINOR(vdevice), capacity, vdevice,
+ vdisk_info, sector_size, info);
+
+ bdput(bd);
+ return err;
+}
+
+void
+xlvbd_del(struct blkfront_info *info)
+{
+ if (info->mi == NULL)
+ return;
+
+ BUG_ON(info->gd == NULL);
+ del_gendisk(info->gd);
+ put_disk(info->gd);
+ info->gd = NULL;
+
+ info->mi = NULL;
+
+ BUG_ON(info->rq == NULL);
+ blk_cleanup_queue(info->rq);
+ info->rq = NULL;
+}
+
+int
+xlvbd_barrier(struct blkfront_info *info)
+{
+ int err;
+
+ err = blk_queue_ordered(info->rq,
+ info->feature_barrier ? QUEUE_ORDERED_DRAIN : QUEUE_ORDERED_NONE, NULL);
+ if (err)
+ return err;
+ printk("blkfront: %s: barriers %s\n",
+ info->gd->disk_name, info->feature_barrier ? "enabled" : "disabled");
+ return 0;
+}
--
> +#include "../../../arch/i386/paravirt-xen/events.h"
> +#include "../../../arch/i386/paravirt-xen/xen-page.h"
this shows the headers are clearly in the wrong place...
> +
> + err = xenbus_printf(xbt, dev->nodename,
> + "ring-ref","%u", info->ring_ref);
why do you need your own printf?
> +static inline int GET_ID_FROM_FREELIST(
does this really need screaming?
> +
> +int blkif_ioctl(struct inode *inode, struct file *filep,
> + unsigned command, unsigned long argument)
> +{
> + int i;
> +
> + DPRINTK_IOCTL("command: 0x%x, argument: 0x%lx, dev: 0x%04x\n",
> + command, (long)argument, inode->i_rdev);
> +
> + switch (command) {
> + case CDROMMULTISESSION:
> + DPRINTK("FIXME: support multisession CDs later\n");
> + for (i = 0; i < sizeof(struct cdrom_multisession); i++)
> + if (put_user(0, (char __user *)(argument + i)))
> + return -EFAULT;
> + return 0;
> +
> + default:
> + /*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
> + command);*/
> + return -EINVAL; /* same return as native Linux */
> + }
eh so you implement no ioctls.. why then implement the ioctl method at
all?
> +static struct xenbus_driver blkfront = {
> + .name = "vbd",
> + .owner = THIS_MODULE,
> + .ids = blkfront_ids,
> + .probe = blkfront_probe,
> + .remove = blkfront_remove,
> + .resume = blkfront_resume,
> + .otherend_changed = backend_changed,
> +};
this can be const
> +
> +#define DPRINTK(_f, _a...) pr_debug(_f, ## _a)
why this silly abstraction? Just use pr_debug in the code directly
On Sat, Jan 13, 2007 at 05:07:28PM -0800, Arjan van de Ven wrote:
> > +
> > +#define DPRINTK(_f, _a...) pr_debug(_f, ## _a)
>
> why this silly abstraction? Just use pr_debug in the code directly
Actually, for drivers, like this one, you should use the dev_printk()
and friends (dev_dbg, dev_err, etc.) instead so that userspace knows
exactly which device and driver the message comes from.
thanks,
greg k-h
On Jan 12 2007 17:45, Jeremy Fitzhardinge wrote:
>
>The block device frontend driver allows the kernel to access block
>devices exported exported by a virtual machine containing a physical
>block device driver.
Is this significantly different from ubd/hostfs that it actually warrants a
reinvention?
>+ (void)xenbus_switch_state(info->xbdev, XenbusStateConnected);
Cast remove, if xenbus_switch_state does not have __must_check.
Also elsewhere.
-`J'
--
On Sun, Jan 14, 2007 at 12:05:13PM +0100, Jan Engelhardt wrote:
> >+ (void)xenbus_switch_state(info->xbdev, XenbusStateConnected);
>
> Cast remove, if xenbus_switch_state does not have __must_check.
> Also elsewhere.
Hmm, why? this way you know that the programmer isn't checking the
return value *on purpose*. More information is good.
Cheers,
Muli
On Jan 14 2007 13:24, Muli Ben-Yehuda wrote:
>On Sun, Jan 14, 2007 at 12:05:13PM +0100, Jan Engelhardt wrote:
>
>> >+ (void)xenbus_switch_state(info->xbdev, XenbusStateConnected);
>>
>> Cast remove, if xenbus_switch_state does not have __must_check.
>> Also elsewhere.
>
>Hmm, why? this way you know that the programmer isn't checking the
>return value *on purpose*. More information is good.
Then I'd prefer a comment. Plus, you don't do (void) on every
xenbus_switch_state, so I have to assume (1) you either forgot to check the
return value or (2) you don't follow your own "on purpose" policy. If you
really want to enforce to use the return value and explicitly not in some
places, then please tag it __must_check. http://lkml.org/lkml/2006/12/21/282
might be something to read.
-`J'
--
On 14/1/07 11:05 am, "Jan Engelhardt" <[email protected]> wrote:
>> The block device frontend driver allows the kernel to access block
>> devices exported exported by a virtual machine containing a physical
>> block device driver.
>
> Is this significantly different from ubd/hostfs that it actually warrants a
> reinvention?
It is certainly unlike hostfs because hostfs provides file-level access to
host storage, not block-level. It's unlike both ubd and hostfs in that both
of those (I believe) make significant use of the syscall interface (and so
assume they run in a process on a Linux host). Also our driver appears to be
lower level, pushing more responsibility for features like CoW into the VMM.
Arguably that's a more generically reusable and flexible strategy although
it requires more VMM run-time support (which a Xen system provides).
>> + (void)xenbus_switch_state(info->xbdev, XenbusStateConnected);
>
> Cast remove, if xenbus_switch_state does not have __must_check.
> Also elsewhere.
Okay, we should certainly follow the general rule here.
Thanks,
Keir
> > +
> > + err = xenbus_printf(xbt, dev->nodename,
> > + "ring-ref","%u", info->ring_ref);
>
> why do you need your own printf?
xenbus_printf isn't a printf replacement - it is used for writing a formatted
string into XenStore (which contains VM configuration data in a
human-readable form).
Internally it does a vsnprintf into a buffer and writes the resulting string
to the XenStore.
Cheers,
Mark
> > +static inline int GET_ID_FROM_FREELIST(
>
> does this really need screaming?
>
> > +
> > +int blkif_ioctl(struct inode *inode, struct file *filep,
> > + unsigned command, unsigned long argument)
> > +{
> > + int i;
> > +
> > + DPRINTK_IOCTL("command: 0x%x, argument: 0x%lx, dev: 0x%04x\n",
> > + command, (long)argument, inode->i_rdev);
> > +
> > + switch (command) {
> > + case CDROMMULTISESSION:
> > + DPRINTK("FIXME: support multisession CDs later\n");
> > + for (i = 0; i < sizeof(struct cdrom_multisession); i++)
> > + if (put_user(0, (char __user *)(argument + i)))
> > + return -EFAULT;
> > + return 0;
> > +
> > + default:
> > + /*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
> > + command);*/
> > + return -EINVAL; /* same return as native Linux */
> > + }
>
> eh so you implement no ioctls.. why then implement the ioctl method at
> all?
I'm not familiar with this code... but perhaps the (fake) multisession
handling is to keep userspace that queries this happy? I can't really think
of anywhere this would apply off the top of my head, though.
Cheers,
Mark
> > +static struct xenbus_driver blkfront = {
> > + .name = "vbd",
> > + .owner = THIS_MODULE,
> > + .ids = blkfront_ids,
> > + .probe = blkfront_probe,
> > + .remove = blkfront_remove,
> > + .resume = blkfront_resume,
> > + .otherend_changed = backend_changed,
> > +};
>
> this can be const
>
> > +
> > +#define DPRINTK(_f, _a...) pr_debug(_f, ## _a)
>
> why this silly abstraction? Just use pr_debug in the code directly
>
>
>
>
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--
Dave: Just a question. What use is a unicyle with no seat? And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!