xen: add blkback support
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Conflicts:
drivers/xen/Makefile
diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
new file mode 100644
index 0000000..5b8d50e
--- /dev/null
+++ b/drivers/xen/blkback/blkback.c
@@ -0,0 +1,656 @@
+/******************************************************************************
+ * arch/xen/drivers/blkif/backend/main.c
+ *
+ * Back-end of the driver for virtual block devices. This portion of the
+ * driver exports a 'unified' block-device interface that can be accessed
+ * by any operating system that implements a compatible front end. A
+ * reference front-end implementation can be found in:
+ * arch/xen/drivers/blkif/frontend
+ *
+ * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
+ * Copyright (c) 2005, Christopher Clark
+ *
+ * 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/spinlock.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/delay.h>
+#include <xen/balloon.h>
+#include <asm/hypervisor.h>
+#include "common.h"
+
+/*
+ * These are rather arbitrary. They are fairly large because adjacent requests
+ * pulled from a communication ring are quite likely to end up being part of
+ * the same scatter/gather request at the disc.
+ *
+ * ** TRY INCREASING 'blkif_reqs' IF WRITE SPEEDS SEEM TOO LOW **
+ *
+ * This will increase the chances of being able to write whole tracks.
+ * 64 should be enough to keep us competitive with Linux.
+ */
+static int blkif_reqs = 64;
+module_param_named(reqs, blkif_reqs, int, 0);
+MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate");
+
+/* Run-time switchable: /sys/module/blkback/parameters/ */
+static unsigned int log_stats = 0;
+static unsigned int debug_lvl = 0;
+module_param(log_stats, int, 0644);
+module_param(debug_lvl, int, 0644);
+
+/*
+ * Each outstanding request that we've passed to the lower device layers has a
+ * 'pending_req' allocated to it. Each buffer_head that completes decrements
+ * the pendcnt towards zero. When it hits zero, the specified domain has a
+ * response queued for it, with the saved 'id' passed back.
+ */
+typedef struct {
+ blkif_t *blkif;
+ u64 id;
+ int nr_pages;
+ atomic_t pendcnt;
+ unsigned short operation;
+ int status;
+ struct list_head free_list;
+} pending_req_t;
+
+static pending_req_t *pending_reqs;
+static struct list_head pending_free;
+static DEFINE_SPINLOCK(pending_free_lock);
+static DECLARE_WAIT_QUEUE_HEAD(pending_free_wq);
+
+#define BLKBACK_INVALID_HANDLE (~0)
+
+static struct page **pending_pages;
+static grant_handle_t *pending_grant_handles;
+
+static inline int vaddr_pagenr(pending_req_t *req, int seg)
+{
+ return (req - pending_reqs) * BLKIF_MAX_SEGMENTS_PER_REQUEST + seg;
+}
+
+static inline unsigned long vaddr(pending_req_t *req, int seg)
+{
+ unsigned long pfn = page_to_pfn(pending_pages[vaddr_pagenr(req, seg)]);
+ return (unsigned long)pfn_to_kaddr(pfn);
+}
+
+#define pending_handle(_req, _seg) \
+ (pending_grant_handles[vaddr_pagenr(_req, _seg)])
+
+
+static int do_block_io_op(blkif_t *blkif);
+static void dispatch_rw_block_io(blkif_t *blkif,
+ blkif_request_t *req,
+ pending_req_t *pending_req);
+static void make_response(blkif_t *blkif, u64 id,
+ unsigned short op, int st);
+
+/******************************************************************
+ * misc small helpers
+ */
+static pending_req_t* alloc_req(void)
+{
+ pending_req_t *req = NULL;
+ unsigned long flags;
+
+ spin_lock_irqsave(&pending_free_lock, flags);
+ if (!list_empty(&pending_free)) {
+ req = list_entry(pending_free.next, pending_req_t, free_list);
+ list_del(&req->free_list);
+ }
+ spin_unlock_irqrestore(&pending_free_lock, flags);
+ return req;
+}
+
+static void free_req(pending_req_t *req)
+{
+ unsigned long flags;
+ int was_empty;
+
+ spin_lock_irqsave(&pending_free_lock, flags);
+ was_empty = list_empty(&pending_free);
+ list_add(&req->free_list, &pending_free);
+ spin_unlock_irqrestore(&pending_free_lock, flags);
+ if (was_empty)
+ wake_up(&pending_free_wq);
+}
+
+static void unplug_queue(blkif_t *blkif)
+{
+ if (blkif->plug == NULL)
+ return;
+ if (blkif->plug->unplug_fn)
+ blkif->plug->unplug_fn(blkif->plug);
+ blk_put_queue(blkif->plug);
+ blkif->plug = NULL;
+}
+
+static void plug_queue(blkif_t *blkif, struct block_device *bdev)
+{
+ request_queue_t *q = bdev_get_queue(bdev);
+
+ if (q == blkif->plug)
+ return;
+ unplug_queue(blkif);
+ blk_get_queue(q);
+ blkif->plug = q;
+}
+
+static void fast_flush_area(pending_req_t *req)
+{
+ struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+ unsigned int i, invcount = 0;
+ grant_handle_t handle;
+ int ret;
+
+ for (i = 0; i < req->nr_pages; i++) {
+ handle = pending_handle(req, i);
+ if (handle == BLKBACK_INVALID_HANDLE)
+ continue;
+ gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
+ GNTMAP_host_map, handle);
+ pending_handle(req, i) = BLKBACK_INVALID_HANDLE;
+ invcount++;
+ }
+
+ ret = HYPERVISOR_grant_table_op(
+ GNTTABOP_unmap_grant_ref, unmap, invcount);
+ BUG_ON(ret);
+}
+
+/******************************************************************
+ * SCHEDULER FUNCTIONS
+ */
+
+static void print_stats(blkif_t *blkif)
+{
+ printk(KERN_DEBUG "%s: oo %3d | rd %4d | wr %4d | br %4d\n",
+ current->comm, blkif->st_oo_req,
+ blkif->st_rd_req, blkif->st_wr_req, blkif->st_br_req);
+ blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
+ blkif->st_rd_req = 0;
+ blkif->st_wr_req = 0;
+ blkif->st_oo_req = 0;
+}
+
+int blkif_schedule(void *arg)
+{
+ blkif_t *blkif = arg;
+
+ blkif_get(blkif);
+
+ if (debug_lvl)
+ printk(KERN_DEBUG "%s: started\n", current->comm);
+
+ while (!kthread_should_stop()) {
+ if (try_to_freeze())
+ continue;
+
+ wait_event_interruptible(
+ blkif->wq,
+ blkif->waiting_reqs || kthread_should_stop());
+ wait_event_interruptible(
+ pending_free_wq,
+ !list_empty(&pending_free) || kthread_should_stop());
+
+ blkif->waiting_reqs = 0;
+ smp_mb(); /* clear flag *before* checking for work */
+
+ if (do_block_io_op(blkif))
+ blkif->waiting_reqs = 1;
+ unplug_queue(blkif);
+
+ if (log_stats && time_after(jiffies, blkif->st_print))
+ print_stats(blkif);
+ }
+
+ if (log_stats)
+ print_stats(blkif);
+ if (debug_lvl)
+ printk(KERN_DEBUG "%s: exiting\n", current->comm);
+
+ blkif->xenblkd = NULL;
+ blkif_put(blkif);
+
+ return 0;
+}
+
+/******************************************************************
+ * COMPLETION CALLBACK -- Called as bh->b_end_io()
+ */
+
+static void __end_block_io_op(pending_req_t *pending_req, int error)
+{
+ /* An error fails the entire request. */
+ if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
+ (error == -EOPNOTSUPP)) {
+ DPRINTK("blkback: write barrier op failed, not supported\n");
+ blkback_barrier(XBT_NIL, pending_req->blkif->be, 0);
+ pending_req->status = BLKIF_RSP_EOPNOTSUPP;
+ } else if (error) {
+ DPRINTK("Buffer not up-to-date at end of operation, "
+ "error=%d\n", error);
+ pending_req->status = BLKIF_RSP_ERROR;
+ }
+
+ if (atomic_dec_and_test(&pending_req->pendcnt)) {
+ fast_flush_area(pending_req);
+ make_response(pending_req->blkif, pending_req->id,
+ pending_req->operation, pending_req->status);
+ blkif_put(pending_req->blkif);
+ free_req(pending_req);
+ }
+}
+
+static int end_block_io_op(struct bio *bio, unsigned int done, int error)
+{
+ if (bio->bi_size != 0)
+ return 1;
+ __end_block_io_op(bio->bi_private, error);
+ bio_put(bio);
+ return error;
+}
+
+
+/******************************************************************************
+ * NOTIFICATION FROM GUEST OS.
+ */
+
+static void blkif_notify_work(blkif_t *blkif)
+{
+ blkif->waiting_reqs = 1;
+ wake_up(&blkif->wq);
+}
+
+irqreturn_t blkif_be_int(int irq, void *dev_id, struct pt_regs *regs)
+{
+ blkif_notify_work(dev_id);
+ return IRQ_HANDLED;
+}
+
+
+
+/******************************************************************
+ * DOWNWARD CALLS -- These interface with the block-device layer proper.
+ */
+
+static int do_block_io_op(blkif_t *blkif)
+{
+ blkif_back_rings_t *blk_rings = &blkif->blk_rings;
+ blkif_request_t req;
+ pending_req_t *pending_req;
+ RING_IDX rc, rp;
+ int more_to_do = 0;
+
+ rc = blk_rings->common.req_cons;
+ rp = blk_rings->common.sring->req_prod;
+ rmb(); /* Ensure we see queued requests up to 'rp'. */
+
+ while (rc != rp) {
+
+ if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
+ break;
+
+ pending_req = alloc_req();
+ if (NULL == pending_req) {
+ blkif->st_oo_req++;
+ more_to_do = 1;
+ break;
+ }
+
+ if (kthread_should_stop()) {
+ more_to_do = 1;
+ break;
+ }
+
+ switch (blkif->blk_protocol) {
+ case BLKIF_PROTOCOL_NATIVE:
+ memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
+ break;
+ case BLKIF_PROTOCOL_X86_32:
+ blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
+ break;
+ case BLKIF_PROTOCOL_X86_64:
+ blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
+ break;
+ default:
+ BUG();
+ }
+ blk_rings->common.req_cons = ++rc; /* before make_response() */
+
+ /* Apply all sanity checks to /private copy/ of request. */
+ barrier();
+
+ switch (req.operation) {
+ case BLKIF_OP_READ:
+ blkif->st_rd_req++;
+ dispatch_rw_block_io(blkif, &req, pending_req);
+ break;
+ case BLKIF_OP_WRITE_BARRIER:
+ blkif->st_br_req++;
+ /* fall through */
+ case BLKIF_OP_WRITE:
+ blkif->st_wr_req++;
+ dispatch_rw_block_io(blkif, &req, pending_req);
+ break;
+ default:
+ /* A good sign something is wrong: sleep for a while to
+ * avoid excessive CPU consumption by a bad guest. */
+ msleep(1);
+ DPRINTK("error: unknown block io operation [%d]\n",
+ req.operation);
+ make_response(blkif, req.id, req.operation,
+ BLKIF_RSP_ERROR);
+ free_req(pending_req);
+ break;
+ }
+
+ /* Yield point for this unbounded loop. */
+ cond_resched();
+ }
+
+ return more_to_do;
+}
+
+static void dispatch_rw_block_io(blkif_t *blkif,
+ blkif_request_t *req,
+ pending_req_t *pending_req)
+{
+ extern void ll_rw_block(int rw, int nr, struct buffer_head * bhs[]);
+ struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+ struct phys_req preq;
+ struct {
+ unsigned long buf; unsigned int nsec;
+ } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
+ unsigned int nseg;
+ struct bio *bio = NULL;
+ int ret, i;
+ int operation;
+
+ switch (req->operation) {
+ case BLKIF_OP_READ:
+ operation = READ;
+ break;
+ case BLKIF_OP_WRITE:
+ operation = WRITE;
+ break;
+ case BLKIF_OP_WRITE_BARRIER:
+ operation = WRITE_BARRIER;
+ break;
+ default:
+ operation = 0; /* make gcc happy */
+ BUG();
+ }
+
+ /* Check that number of segments is sane. */
+ nseg = req->nr_segments;
+ if (unlikely(nseg == 0 && operation != WRITE_BARRIER) ||
+ unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
+ DPRINTK("Bad number of segments in request (%d)\n", nseg);
+ goto fail_response;
+ }
+
+ preq.dev = req->handle;
+ preq.sector_number = req->sector_number;
+ preq.nr_sects = 0;
+
+ pending_req->blkif = blkif;
+ pending_req->id = req->id;
+ pending_req->operation = req->operation;
+ pending_req->status = BLKIF_RSP_OKAY;
+ pending_req->nr_pages = nseg;
+
+ for (i = 0; i < nseg; i++) {
+ uint32_t flags;
+
+ seg[i].nsec = req->seg[i].last_sect -
+ req->seg[i].first_sect + 1;
+
+ if ((req->seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
+ (req->seg[i].last_sect < req->seg[i].first_sect))
+ goto fail_response;
+ preq.nr_sects += seg[i].nsec;
+
+ flags = GNTMAP_host_map;
+ if (operation != READ)
+ flags |= GNTMAP_readonly;
+ gnttab_set_map_op(&map[i], vaddr(pending_req, i), flags,
+ req->seg[i].gref, blkif->domid);
+ }
+
+ ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, nseg);
+ BUG_ON(ret);
+
+ for (i = 0; i < nseg; i++) {
+ if (unlikely(map[i].status != 0)) {
+ DPRINTK("invalid buffer -- could not remap it\n");
+ map[i].handle = BLKBACK_INVALID_HANDLE;
+ ret |= 1;
+ }
+
+ pending_handle(pending_req, i) = map[i].handle;
+
+ if (ret)
+ continue;
+
+ set_phys_to_machine(__pa(vaddr(
+ pending_req, i)) >> PAGE_SHIFT,
+ FOREIGN_FRAME(map[i].dev_bus_addr >> PAGE_SHIFT));
+ seg[i].buf = map[i].dev_bus_addr |
+ (req->seg[i].first_sect << 9);
+ }
+
+ if (ret)
+ goto fail_flush;
+
+ if (vbd_translate(&preq, blkif, operation) != 0) {
+ DPRINTK("access denied: %s of [%llu,%llu] on dev=%04x\n",
+ operation == READ ? "read" : "write",
+ preq.sector_number,
+ preq.sector_number + preq.nr_sects, preq.dev);
+ goto fail_flush;
+ }
+
+ plug_queue(blkif, preq.bdev);
+ atomic_set(&pending_req->pendcnt, 1);
+ blkif_get(blkif);
+
+ for (i = 0; i < nseg; i++) {
+ if (((int)preq.sector_number|(int)seg[i].nsec) &
+ ((bdev_hardsect_size(preq.bdev) >> 9) - 1)) {
+ DPRINTK("Misaligned I/O request from domain %d",
+ blkif->domid);
+ goto fail_put_bio;
+ }
+
+ while ((bio == NULL) ||
+ (bio_add_page(bio,
+ virt_to_page(vaddr(pending_req, i)),
+ seg[i].nsec << 9,
+ seg[i].buf & ~PAGE_MASK) == 0)) {
+ if (bio) {
+ atomic_inc(&pending_req->pendcnt);
+ submit_bio(operation, bio);
+ }
+
+ bio = bio_alloc(GFP_KERNEL, nseg-i);
+ if (unlikely(bio == NULL))
+ goto fail_put_bio;
+
+ bio->bi_bdev = preq.bdev;
+ bio->bi_private = pending_req;
+ bio->bi_end_io = end_block_io_op;
+ bio->bi_sector = preq.sector_number;
+ }
+
+ preq.sector_number += seg[i].nsec;
+ }
+
+ if (!bio) {
+ BUG_ON(operation != WRITE_BARRIER);
+ bio = bio_alloc(GFP_KERNEL, 0);
+ if (unlikely(bio == NULL))
+ goto fail_put_bio;
+
+ bio->bi_bdev = preq.bdev;
+ bio->bi_private = pending_req;
+ bio->bi_end_io = end_block_io_op;
+ bio->bi_sector = -1;
+ }
+
+ submit_bio(operation, bio);
+
+ if (operation == READ)
+ blkif->st_rd_sect += preq.nr_sects;
+ else if (operation == WRITE || operation == WRITE_BARRIER)
+ blkif->st_wr_sect += preq.nr_sects;
+
+ return;
+
+ fail_flush:
+ fast_flush_area(pending_req);
+ fail_response:
+ make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
+ free_req(pending_req);
+ msleep(1); /* back off a bit */
+ return;
+
+ fail_put_bio:
+ __end_block_io_op(pending_req, -EINVAL);
+ if (bio)
+ bio_put(bio);
+ unplug_queue(blkif);
+ msleep(1); /* back off a bit */
+ return;
+}
+
+
+
+/******************************************************************
+ * MISCELLANEOUS SETUP / TEARDOWN / DEBUGGING
+ */
+
+
+static void make_response(blkif_t *blkif, u64 id,
+ unsigned short op, int st)
+{
+ blkif_response_t resp;
+ unsigned long flags;
+ blkif_back_rings_t *blk_rings = &blkif->blk_rings;
+ int more_to_do = 0;
+ int notify;
+
+ resp.id = id;
+ resp.operation = op;
+ resp.status = st;
+
+ spin_lock_irqsave(&blkif->blk_ring_lock, flags);
+ /* Place on the response ring for the relevant domain. */
+ switch (blkif->blk_protocol) {
+ case BLKIF_PROTOCOL_NATIVE:
+ memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
+ &resp, sizeof(resp));
+ break;
+ case BLKIF_PROTOCOL_X86_32:
+ memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
+ &resp, sizeof(resp));
+ break;
+ case BLKIF_PROTOCOL_X86_64:
+ memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
+ &resp, sizeof(resp));
+ break;
+ default:
+ BUG();
+ }
+ blk_rings->common.rsp_prod_pvt++;
+ RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
+ if (blk_rings->common.rsp_prod_pvt == blk_rings->common.req_cons) {
+ /*
+ * Tail check for pending requests. Allows frontend to avoid
+ * notifications if requests are already in flight (lower
+ * overheads and promotes batching).
+ */
+ RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
+
+ } else if (RING_HAS_UNCONSUMED_REQUESTS(&blk_rings->common)) {
+ more_to_do = 1;
+ }
+
+ spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
+
+ if (more_to_do)
+ blkif_notify_work(blkif);
+ if (notify)
+ notify_remote_via_irq(blkif->irq);
+}
+
+static int __init blkif_init(void)
+{
+ int i, mmap_pages;
+
+ if (!is_running_on_xen())
+ return -ENODEV;
+
+ mmap_pages = blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST;
+
+ pending_reqs = kmalloc(sizeof(pending_reqs[0]) *
+ blkif_reqs, GFP_KERNEL);
+ pending_grant_handles = kmalloc(sizeof(pending_grant_handles[0]) *
+ mmap_pages, GFP_KERNEL);
+ pending_pages = alloc_empty_pages_and_pagevec(mmap_pages);
+
+ if (!pending_reqs || !pending_grant_handles || !pending_pages)
+ goto out_of_memory;
+
+ for (i = 0; i < mmap_pages; i++)
+ pending_grant_handles[i] = BLKBACK_INVALID_HANDLE;
+
+ blkif_interface_init();
+
+ memset(pending_reqs, 0, sizeof(pending_reqs));
+ INIT_LIST_HEAD(&pending_free);
+
+ for (i = 0; i < blkif_reqs; i++)
+ list_add_tail(&pending_reqs[i].free_list, &pending_free);
+
+ blkif_xenbus_init();
+
+ return 0;
+
+ out_of_memory:
+ kfree(pending_reqs);
+ kfree(pending_grant_handles);
+ free_empty_pages_and_pagevec(pending_pages, mmap_pages);
+ printk("%s: out of memory\n", __FUNCTION__);
+ return -ENOMEM;
+}
+
+module_init(blkif_init);
+
+MODULE_LICENSE("Dual BSD/GPL");