path: root/drivers/block/xen-blkback/xenbus.c

/*  Xenbus code for blkif backend
    Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
    Copyright (C) 2005 XenSource Ltd

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

*/

#include <stdarg.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <xen/events.h>
#include <xen/grant_table.h>
#include "common.h"

struct backend_info {
	struct xenbus_device	*dev;
	struct xen_blkif	*blkif;
	struct xenbus_watch	backend_watch;
	unsigned		major;
	unsigned		minor;
	char			*mode;
};

static struct kmem_cache *xen_blkif_cachep;
static void connect(struct backend_info *);
static int connect_ring(struct backend_info *);
static void backend_changed(struct xenbus_watch *, const char **,
			    unsigned int);

struct xenbus_device *xen_blkbk_xenbus(struct backend_info *be)
{
	return be->dev;
}

static int blkback_name(struct xen_blkif *blkif, char *buf)
{
	char *devpath, *devname;
	struct xenbus_device *dev = blkif->be->dev;

	devpath = xenbus_read(XBT_NIL, dev->nodename, "dev", NULL);
	if (IS_ERR(devpath))
		return PTR_ERR(devpath);

	devname = strstr(devpath, "/dev/");
	if (devname != NULL)
		devname += strlen("/dev/");
	else
		devname  = devpath;

	snprintf(buf, TASK_COMM_LEN, "blkback.%d.%s", blkif->domid, devname);
	kfree(devpath);

	return 0;
}

static void xen_update_blkif_status(struct xen_blkif *blkif)
{
	int err;
	char name[TASK_COMM_LEN];

	/* Not ready to connect? */
	if (!blkif->irq || !blkif->vbd.bdev)
		return;

	/* Already connected? */
	if (blkif->be->dev->state == XenbusStateConnected)
		return;

	/* Attempt to connect: exit if we fail to. */
	connect(blkif->be);
	if (blkif->be->dev->state != XenbusStateConnected)
		return;

	err = blkback_name(blkif, name);
	if (err) {
		xenbus_dev_error(blkif->be->dev, err, "get blkback dev name");
		return;
	}

	err = filemap_write_and_wait(blkif->vbd.bdev->bd_inode->i_mapping);
	if (err) {
		xenbus_dev_error(blkif->be->dev, err, "block flush");
		return;
	}
	invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);

	blkif->xenblkd = kthread_run(xen_blkif_schedule, blkif, "%s", name);
	if (IS_ERR(blkif->xenblkd)) {
		err = PTR_ERR(blkif->xenblkd);
		blkif->xenblkd = NULL;
		xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
		return;
	}
}

static struct xen_blkif *xen_blkif_alloc(domid_t domid)
{
	struct xen_blkif *blkif;
	struct pending_req *req, *n;
	int i, j;

	BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);

	blkif = kmem_cache_zalloc(xen_blkif_cachep, GFP_KERNEL);
	if (!blkif)
		return ERR_PTR(-ENOMEM);

	blkif->domid = domid;
	spin_lock_init(&blkif->blk_ring_lock);
	atomic_set(&blkif->refcnt, 1);
	init_waitqueue_head(&blkif->wq);
	init_completion(&blkif->drain_complete);
	atomic_set(&blkif->drain, 0);
	blkif->st_print = jiffies;
	init_waitqueue_head(&blkif->waiting_to_free);
	blkif->persistent_gnts.rb_node = NULL;
	spin_lock_init(&blkif->free_pages_lock);
	INIT_LIST_HEAD(&blkif->free_pages);
	INIT_LIST_HEAD(&blkif->persistent_purge_list);
	blkif->free_pages_num = 0;
	atomic_set(&blkif->persistent_gnt_in_use, 0);
	atomic_set(&blkif->inflight, 0);
	INIT_WORK(&blkif->persistent_purge_work, xen_blkbk_unmap_purged_grants);

	INIT_LIST_HEAD(&blkif->pending_free);

	for (i = 0; i < XEN_BLKIF_REQS; i++) {
		req = kzalloc(sizeof(*req), GFP_KERNEL);
		if (!req)
			goto fail;
		list_add_tail(&req->free_list,
		              &blkif->pending_free);
		for (j = 0; j < MAX_INDIRECT_SEGMENTS; j++) {
			req->segments[j] = kzalloc(sizeof(*req->segments[0]),
			                           GFP_KERNEL);
			if (!req->segments[j])
				goto fail;
		}
		for (j = 0; j < MAX_INDIRECT_PAGES