linux/drivers/block/xen-blkback/blkback.c
Roger Pau Monne 087ffecdaa xen-blkback: use balloon pages for persistent grants
With current persistent grants implementation we are not freeing the
persistent grants after we disconnect the device. Since grant map
operations change the mfn of the allocated page, and we can no longer
pass it to __free_page without setting the mfn to a sane value, use
balloon grant pages instead, as the gntdev device does.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: stable@vger.kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2013-02-19 15:17:21 -05:00

1136 lines
30 KiB
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:
* drivers/block/xen-blkfront.c
*
* 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 <linux/freezer.h>
#include <linux/bitmap.h>
#include <xen/events.h>
#include <xen/page.h>
#include <xen/xen.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <xen/balloon.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 'xen_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 xen_blkif_reqs = 64;
module_param_named(reqs, xen_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;
module_param(log_stats, 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.
*/
struct pending_req {
struct xen_blkif *blkif;
u64 id;
int nr_pages;
atomic_t pendcnt;
unsigned short operation;
int status;
struct list_head free_list;
DECLARE_BITMAP(unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
};
#define BLKBACK_INVALID_HANDLE (~0)
struct xen_blkbk {
struct pending_req *pending_reqs;
/* List of all 'pending_req' available */
struct list_head pending_free;
/* And its spinlock. */
spinlock_t pending_free_lock;
wait_queue_head_t pending_free_wq;
/* The list of all pages that are available. */
struct page **pending_pages;
/* And the grant handles that are available. */
grant_handle_t *pending_grant_handles;
};
static struct xen_blkbk *blkbk;
/*
* Maximum number of grant pages that can be mapped in blkback.
* BLKIF_MAX_SEGMENTS_PER_REQUEST * RING_SIZE is the maximum number of
* pages that blkback will persistently map.
* Currently, this is:
* RING_SIZE = 32 (for all known ring types)
* BLKIF_MAX_SEGMENTS_PER_REQUEST = 11
* sizeof(struct persistent_gnt) = 48
* So the maximum memory used to store the grants is:
* 32 * 11 * 48 = 16896 bytes
*/
static inline unsigned int max_mapped_grant_pages(enum blkif_protocol protocol)
{
switch (protocol) {
case BLKIF_PROTOCOL_NATIVE:
return __CONST_RING_SIZE(blkif, PAGE_SIZE) *
BLKIF_MAX_SEGMENTS_PER_REQUEST;
case BLKIF_PROTOCOL_X86_32:
return __CONST_RING_SIZE(blkif_x86_32, PAGE_SIZE) *
BLKIF_MAX_SEGMENTS_PER_REQUEST;
case BLKIF_PROTOCOL_X86_64:
return __CONST_RING_SIZE(blkif_x86_64, PAGE_SIZE) *
BLKIF_MAX_SEGMENTS_PER_REQUEST;
default:
BUG();
}
return 0;
}
/*
* Little helpful macro to figure out the index and virtual address of the
* pending_pages[..]. For each 'pending_req' we have have up to
* BLKIF_MAX_SEGMENTS_PER_REQUEST (11) pages. The seg would be from 0 through
* 10 and would index in the pending_pages[..].
*/
static inline int vaddr_pagenr(struct pending_req *req, int seg)
{
return (req - blkbk->pending_reqs) *
BLKIF_MAX_SEGMENTS_PER_REQUEST + seg;
}
#define pending_page(req, seg) pending_pages[vaddr_pagenr(req, seg)]
static inline unsigned long vaddr(struct pending_req *req, int seg)
{
unsigned long pfn = page_to_pfn(blkbk->pending_page(req, seg));
return (unsigned long)pfn_to_kaddr(pfn);
}
#define pending_handle(_req, _seg) \
(blkbk->pending_grant_handles[vaddr_pagenr(_req, _seg)])
static int do_block_io_op(struct xen_blkif *blkif);
static int dispatch_rw_block_io(struct xen_blkif *blkif,
struct blkif_request *req,
struct pending_req *pending_req);
static void make_response(struct xen_blkif *blkif, u64 id,
unsigned short op, int st);
#define foreach_grant_safe(pos, n, rbtree, node) \
for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
(n) = rb_next(&(pos)->node); \
&(pos)->node != NULL; \
(pos) = container_of(n, typeof(*(pos)), node), \
(n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
static void add_persistent_gnt(struct rb_root *root,
struct persistent_gnt *persistent_gnt)
{
struct rb_node **new = &(root->rb_node), *parent = NULL;
struct persistent_gnt *this;
/* Figure out where to put new node */
while (*new) {
this = container_of(*new, struct persistent_gnt, node);
parent = *new;
if (persistent_gnt->gnt < this->gnt)
new = &((*new)->rb_left);
else if (persistent_gnt->gnt > this->gnt)
new = &((*new)->rb_right);
else {
pr_alert(DRV_PFX " trying to add a gref that's already in the tree\n");
BUG();
}
}
/* Add new node and rebalance tree. */
rb_link_node(&(persistent_gnt->node), parent, new);
rb_insert_color(&(persistent_gnt->node), root);
}
static struct persistent_gnt *get_persistent_gnt(struct rb_root *root,
grant_ref_t gref)
{
struct persistent_gnt *data;
struct rb_node *node = root->rb_node;
while (node) {
data = container_of(node, struct persistent_gnt, node);
if (gref < data->gnt)
node = node->rb_left;
else if (gref > data->gnt)
node = node->rb_right;
else
return data;
}
return NULL;
}
static void free_persistent_gnts(struct rb_root *root, unsigned int num)
{
struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct persistent_gnt *persistent_gnt;
struct rb_node *n;
int ret = 0;
int segs_to_unmap = 0;
foreach_grant_safe(persistent_gnt, n, root, node) {
BUG_ON(persistent_gnt->handle ==
BLKBACK_INVALID_HANDLE);
gnttab_set_unmap_op(&unmap[segs_to_unmap],
(unsigned long) pfn_to_kaddr(page_to_pfn(
persistent_gnt->page)),
GNTMAP_host_map,
persistent_gnt->handle);
pages[segs_to_unmap] = persistent_gnt->page;
if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
!rb_next(&persistent_gnt->node)) {
ret = gnttab_unmap_refs(unmap, NULL, pages,
segs_to_unmap);
BUG_ON(ret);
free_xenballooned_pages(segs_to_unmap, pages);
segs_to_unmap = 0;
}
rb_erase(&persistent_gnt->node, root);
kfree(persistent_gnt);
num--;
}
BUG_ON(num != 0);
}
/*
* Retrieve from the 'pending_reqs' a free pending_req structure to be used.
*/
static struct pending_req *alloc_req(void)
{
struct pending_req *req = NULL;
unsigned long flags;
spin_lock_irqsave(&blkbk->pending_free_lock, flags);
if (!list_empty(&blkbk->pending_free)) {
req = list_entry(blkbk->pending_free.next, struct pending_req,
free_list);
list_del(&req->free_list);
}
spin_unlock_irqrestore(&blkbk->pending_free_lock, flags);
return req;
}
/*
* Return the 'pending_req' structure back to the freepool. We also
* wake up the thread if it was waiting for a free page.
*/
static void free_req(struct pending_req *req)
{
unsigned long flags;
int was_empty;
spin_lock_irqsave(&blkbk->pending_free_lock, flags);
was_empty = list_empty(&blkbk->pending_free);
list_add(&req->free_list, &blkbk->pending_free);
spin_unlock_irqrestore(&blkbk->pending_free_lock, flags);
if (was_empty)
wake_up(&blkbk->pending_free_wq);
}
/*
* Routines for managing virtual block devices (vbds).
*/
static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
int operation)
{
struct xen_vbd *vbd = &blkif->vbd;
int rc = -EACCES;
if ((operation != READ) && vbd->readonly)
goto out;
if (likely(req->nr_sects)) {
blkif_sector_t end = req->sector_number + req->nr_sects;
if (unlikely(end < req->sector_number))
goto out;
if (unlikely(end > vbd_sz(vbd)))
goto out;
}
req->dev = vbd->pdevice;
req->bdev = vbd->bdev;
rc = 0;
out:
return rc;
}
static void xen_vbd_resize(struct xen_blkif *blkif)
{
struct xen_vbd *vbd = &blkif->vbd;
struct xenbus_transaction xbt;
int err;
struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
unsigned long long new_size = vbd_sz(vbd);
pr_info(DRV_PFX "VBD Resize: Domid: %d, Device: (%d, %d)\n",
blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
pr_info(DRV_PFX "VBD Resize: new size %llu\n", new_size);
vbd->size = new_size;
again:
err = xenbus_transaction_start(&xbt);
if (err) {
pr_warn(DRV_PFX "Error starting transaction");
return;
}
err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
(unsigned long long)vbd_sz(vbd));
if (err) {
pr_warn(DRV_PFX "Error writing new size");
goto abort;
}
/*
* Write the current state; we will use this to synchronize
* the front-end. If the current state is "connected" the
* front-end will get the new size information online.
*/
err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
if (err) {
pr_warn(DRV_PFX "Error writing the state");
goto abort;
}
err = xenbus_transaction_end(xbt, 0);
if (err == -EAGAIN)
goto again;
if (err)
pr_warn(DRV_PFX "Error ending transaction");
return;
abort:
xenbus_transaction_end(xbt, 1);
}
/*
* Notification from the guest OS.
*/
static void blkif_notify_work(struct xen_blkif *blkif)
{
blkif->waiting_reqs = 1;
wake_up(&blkif->wq);
}
irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
{
blkif_notify_work(dev_id);
return IRQ_HANDLED;
}
/*
* SCHEDULER FUNCTIONS
*/
static void print_stats(struct xen_blkif *blkif)
{
pr_info("xen-blkback (%s): oo %3d | rd %4d | wr %4d | f %4d"
" | ds %4d\n",
current->comm, blkif->st_oo_req,
blkif->st_rd_req, blkif->st_wr_req,
blkif->st_f_req, blkif->st_ds_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;
blkif->st_ds_req = 0;
}
int xen_blkif_schedule(void *arg)
{
struct xen_blkif *blkif = arg;
struct xen_vbd *vbd = &blkif->vbd;
xen_blkif_get(blkif);
while (!kthread_should_stop()) {
if (try_to_freeze())
continue;
if (unlikely(vbd->size != vbd_sz(vbd)))
xen_vbd_resize(blkif);
wait_event_interruptible(
blkif->wq,
blkif->waiting_reqs || kthread_should_stop());
wait_event_interruptible(
blkbk->pending_free_wq,
!list_empty(&blkbk->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;
if (log_stats && time_after(jiffies, blkif->st_print))
print_stats(blkif);
}
/* Free all persistent grant pages */
if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
free_persistent_gnts(&blkif->persistent_gnts,
blkif->persistent_gnt_c);
BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
blkif->persistent_gnt_c = 0;
if (log_stats)
print_stats(blkif);
blkif->xenblkd = NULL;
xen_blkif_put(blkif);
return 0;
}
struct seg_buf {
unsigned long buf;
unsigned int nsec;
};
/*
* Unmap the grant references, and also remove the M2P over-rides
* used in the 'pending_req'.
*/
static void xen_blkbk_unmap(struct pending_req *req)
{
struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
unsigned int i, invcount = 0;
grant_handle_t handle;
int ret;
for (i = 0; i < req->nr_pages; i++) {
if (!test_bit(i, req->unmap_seg))
continue;
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;
pages[invcount] = virt_to_page(vaddr(req, i));
invcount++;
}
ret = gnttab_unmap_refs(unmap, NULL, pages, invcount);
BUG_ON(ret);
}
static int xen_blkbk_map(struct blkif_request *req,
struct pending_req *pending_req,
struct seg_buf seg[],
struct page *pages[])
{
struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct persistent_gnt *persistent_gnts[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
struct persistent_gnt *persistent_gnt = NULL;
struct xen_blkif *blkif = pending_req->blkif;
phys_addr_t addr = 0;
int i, j;
bool new_map;
int nseg = req->u.rw.nr_segments;
int segs_to_map = 0;
int ret = 0;
int use_persistent_gnts;
use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
BUG_ON(blkif->persistent_gnt_c >
max_mapped_grant_pages(pending_req->blkif->blk_protocol));
/*
* Fill out preq.nr_sects with proper amount of sectors, and setup
* assign map[..] with the PFN of the page in our domain with the
* corresponding grant reference for each page.
*/
for (i = 0; i < nseg; i++) {
uint32_t flags;
if (use_persistent_gnts)
persistent_gnt = get_persistent_gnt(
&blkif->persistent_gnts,
req->u.rw.seg[i].gref);
if (persistent_gnt) {
/*
* We are using persistent grants and
* the grant is already mapped
*/
new_map = false;
} else if (use_persistent_gnts &&
blkif->persistent_gnt_c <
max_mapped_grant_pages(blkif->blk_protocol)) {
/*
* We are using persistent grants, the grant is
* not mapped but we have room for it
*/
new_map = true;
persistent_gnt = kmalloc(
sizeof(struct persistent_gnt),
GFP_KERNEL);
if (!persistent_gnt)
return -ENOMEM;
if (alloc_xenballooned_pages(1, &persistent_gnt->page,
false)) {
kfree(persistent_gnt);
return -ENOMEM;
}
persistent_gnt->gnt = req->u.rw.seg[i].gref;
persistent_gnt->handle = BLKBACK_INVALID_HANDLE;
pages_to_gnt[segs_to_map] =
persistent_gnt->page;
addr = (unsigned long) pfn_to_kaddr(
page_to_pfn(persistent_gnt->page));
add_persistent_gnt(&blkif->persistent_gnts,
persistent_gnt);
blkif->persistent_gnt_c++;
pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n",
persistent_gnt->gnt, blkif->persistent_gnt_c,
max_mapped_grant_pages(blkif->blk_protocol));
} else {
/*
* We are either using persistent grants and
* hit the maximum limit of grants mapped,
* or we are not using persistent grants.
*/
if (use_persistent_gnts &&
!blkif->vbd.overflow_max_grants) {
blkif->vbd.overflow_max_grants = 1;
pr_alert(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n",
blkif->domid, blkif->vbd.handle);
}
new_map = true;
pages[i] = blkbk->pending_page(pending_req, i);
addr = vaddr(pending_req, i);
pages_to_gnt[segs_to_map] =
blkbk->pending_page(pending_req, i);
}
if (persistent_gnt) {
pages[i] = persistent_gnt->page;
persistent_gnts[i] = persistent_gnt;
} else {
persistent_gnts[i] = NULL;
}
if (new_map) {
flags = GNTMAP_host_map;
if (!persistent_gnt &&
(pending_req->operation != BLKIF_OP_READ))
flags |= GNTMAP_readonly;
gnttab_set_map_op(&map[segs_to_map++], addr,
flags, req->u.rw.seg[i].gref,
blkif->domid);
}
}
if (segs_to_map) {
ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
BUG_ON(ret);
}
/*
* Now swizzle the MFN in our domain with the MFN from the other domain
* so that when we access vaddr(pending_req,i) it has the contents of
* the page from the other domain.
*/
bitmap_zero(pending_req->unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
for (i = 0, j = 0; i < nseg; i++) {
if (!persistent_gnts[i] ||
persistent_gnts[i]->handle == BLKBACK_INVALID_HANDLE) {
/* This is a newly mapped grant */
BUG_ON(j >= segs_to_map);
if (unlikely(map[j].status != 0)) {
pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
map[j].handle = BLKBACK_INVALID_HANDLE;
ret |= 1;
if (persistent_gnts[i]) {
rb_erase(&persistent_gnts[i]->node,
&blkif->persistent_gnts);
blkif->persistent_gnt_c--;
kfree(persistent_gnts[i]);
persistent_gnts[i] = NULL;
}
}
}
if (persistent_gnts[i]) {
if (persistent_gnts[i]->handle ==
BLKBACK_INVALID_HANDLE) {
/*
* If this is a new persistent grant
* save the handler
*/
persistent_gnts[i]->handle = map[j].handle;
persistent_gnts[i]->dev_bus_addr =
map[j++].dev_bus_addr;
}
pending_handle(pending_req, i) =
persistent_gnts[i]->handle;
if (ret)
continue;
seg[i].buf = persistent_gnts[i]->dev_bus_addr |
(req->u.rw.seg[i].first_sect << 9);
} else {
pending_handle(pending_req, i) = map[j].handle;
bitmap_set(pending_req->unmap_seg, i, 1);
if (ret) {
j++;
continue;
}
seg[i].buf = map[j++].dev_bus_addr |
(req->u.rw.seg[i].first_sect << 9);
}
}
return ret;
}
static int dispatch_discard_io(struct xen_blkif *blkif,
struct blkif_request *req)
{
int err = 0;
int status = BLKIF_RSP_OKAY;
struct block_device *bdev = blkif->vbd.bdev;
unsigned long secure;
blkif->st_ds_req++;
xen_blkif_get(blkif);
secure = (blkif->vbd.discard_secure &&
(req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
BLKDEV_DISCARD_SECURE : 0;
err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
req->u.discard.nr_sectors,
GFP_KERNEL, secure);
if (err == -EOPNOTSUPP) {
pr_debug(DRV_PFX "discard op failed, not supported\n");
status = BLKIF_RSP_EOPNOTSUPP;
} else if (err)
status = BLKIF_RSP_ERROR;
make_response(blkif, req->u.discard.id, req->operation, status);
xen_blkif_put(blkif);
return err;
}
static void xen_blk_drain_io(struct xen_blkif *blkif)
{
atomic_set(&blkif->drain, 1);
do {
/* The initial value is one, and one refcnt taken at the
* start of the xen_blkif_schedule thread. */
if (atomic_read(&blkif->refcnt) <= 2)
break;
wait_for_completion_interruptible_timeout(
&blkif->drain_complete, HZ);
if (!atomic_read(&blkif->drain))
break;
} while (!kthread_should_stop());
atomic_set(&blkif->drain, 0);
}
/*
* Completion callback on the bio's. Called as bh->b_end_io()
*/
static void __end_block_io_op(struct pending_req *pending_req, int error)
{
/* An error fails the entire request. */
if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
(error == -EOPNOTSUPP)) {
pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
pending_req->status = BLKIF_RSP_EOPNOTSUPP;
} else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
(error == -EOPNOTSUPP)) {
pr_debug(DRV_PFX "write barrier op failed, not supported\n");
xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
pending_req->status = BLKIF_RSP_EOPNOTSUPP;
} else if (error) {
pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
" error=%d\n", error);
pending_req->status = BLKIF_RSP_ERROR;
}
/*
* If all of the bio's have completed it is time to unmap
* the grant references associated with 'request' and provide
* the proper response on the ring.
*/
if (atomic_dec_and_test(&pending_req->pendcnt)) {
xen_blkbk_unmap(pending_req);
make_response(pending_req->blkif, pending_req->id,
pending_req->operation, pending_req->status);
xen_blkif_put(pending_req->blkif);
if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
if (atomic_read(&pending_req->blkif->drain))
complete(&pending_req->blkif->drain_complete);
}
free_req(pending_req);
}
}
/*
* bio callback.
*/
static void end_block_io_op(struct bio *bio, int error)
{
__end_block_io_op(bio->bi_private, error);
bio_put(bio);
}
/*
* Function to copy the from the ring buffer the 'struct blkif_request'
* (which has the sectors we want, number of them, grant references, etc),
* and transmute it to the block API to hand it over to the proper block disk.
*/
static int
__do_block_io_op(struct xen_blkif *blkif)
{
union blkif_back_rings *blk_rings = &blkif->blk_rings;
struct blkif_request req;
struct pending_req *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;
if (kthread_should_stop()) {
more_to_do = 1;
break;
}
pending_req = alloc_req();
if (NULL == pending_req) {
blkif->st_oo_req++;
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();
if (unlikely(req.operation == BLKIF_OP_DISCARD)) {
free_req(pending_req);
if (dispatch_discard_io(blkif, &req))
break;
} else if (dispatch_rw_block_io(blkif, &req, pending_req))
break;
/* Yield point for this unbounded loop. */
cond_resched();
}
return more_to_do;
}
static int
do_block_io_op(struct xen_blkif *blkif)
{
union blkif_back_rings *blk_rings = &blkif->blk_rings;
int more_to_do;
do {
more_to_do = __do_block_io_op(blkif);
if (more_to_do)
break;
RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
} while (more_to_do);
return more_to_do;
}
/*
* Transmutation of the 'struct blkif_request' to a proper 'struct bio'
* and call the 'submit_bio' to pass it to the underlying storage.
*/
static int dispatch_rw_block_io(struct xen_blkif *blkif,
struct blkif_request *req,
struct pending_req *pending_req)
{
struct phys_req preq;
struct seg_buf seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
unsigned int nseg;
struct bio *bio = NULL;
struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
int i, nbio = 0;
int operation;
struct blk_plug plug;
bool drain = false;
struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
switch (req->operation) {
case BLKIF_OP_READ:
blkif->st_rd_req++;
operation = READ;
break;
case BLKIF_OP_WRITE:
blkif->st_wr_req++;
operation = WRITE_ODIRECT;
break;
case BLKIF_OP_WRITE_BARRIER:
drain = true;
case BLKIF_OP_FLUSH_DISKCACHE:
blkif->st_f_req++;
operation = WRITE_FLUSH;
break;
default:
operation = 0; /* make gcc happy */
goto fail_response;
break;
}
/* Check that the number of segments is sane. */
nseg = req->u.rw.nr_segments;
if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
nseg);
/* Haven't submitted any bio's yet. */
goto fail_response;
}
preq.sector_number = req->u.rw.sector_number;
preq.nr_sects = 0;
pending_req->blkif = blkif;
pending_req->id = req->u.rw.id;
pending_req->operation = req->operation;
pending_req->status = BLKIF_RSP_OKAY;
pending_req->nr_pages = nseg;
for (i = 0; i < nseg; i++) {
seg[i].nsec = req->u.rw.seg[i].last_sect -
req->u.rw.seg[i].first_sect + 1;
if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
(req->u.rw.seg[i].last_sect < req->u.rw.seg[i].first_sect))
goto fail_response;
preq.nr_sects += seg[i].nsec;
}
if (xen_vbd_translate(&preq, blkif, operation) != 0) {
pr_debug(DRV_PFX "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_response;
}
/*
* This check _MUST_ be done after xen_vbd_translate as the preq.bdev
* is set there.
*/
for (i = 0; i < nseg; i++) {
if (((int)preq.sector_number|(int)seg[i].nsec) &
((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
pr_debug(DRV_PFX "Misaligned I/O request from domain %d",
blkif->domid);
goto fail_response;
}
}
/* Wait on all outstanding I/O's and once that has been completed
* issue the WRITE_FLUSH.
*/
if (drain)
xen_blk_drain_io(pending_req->blkif);
/*
* If we have failed at this point, we need to undo the M2P override,
* set gnttab_set_unmap_op on all of the grant references and perform
* the hypercall to unmap the grants - that is all done in
* xen_blkbk_unmap.
*/
if (xen_blkbk_map(req, pending_req, seg, pages))
goto fail_flush;
/*
* This corresponding xen_blkif_put is done in __end_block_io_op, or
* below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
*/
xen_blkif_get(blkif);
for (i = 0; i < nseg; i++) {
while ((bio == NULL) ||
(bio_add_page(bio,
pages[i],
seg[i].nsec << 9,
seg[i].buf & ~PAGE_MASK) == 0)) {
bio = bio_alloc(GFP_KERNEL, nseg-i);
if (unlikely(bio == NULL))
goto fail_put_bio;
biolist[nbio++] = 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;
}
/* This will be hit if the operation was a flush or discard. */
if (!bio) {
BUG_ON(operation != WRITE_FLUSH);
bio = bio_alloc(GFP_KERNEL, 0);
if (unlikely(bio == NULL))
goto fail_put_bio;
biolist[nbio++] = bio;
bio->bi_bdev = preq.bdev;
bio->bi_private = pending_req;
bio->bi_end_io = end_block_io_op;
}
/*
* We set it one so that the last submit_bio does not have to call
* atomic_inc.
*/
atomic_set(&pending_req->pendcnt, nbio);
/* Get a reference count for the disk queue and start sending I/O */
blk_start_plug(&plug);
for (i = 0; i < nbio; i++)
submit_bio(operation, biolist[i]);
/* Let the I/Os go.. */
blk_finish_plug(&plug);
if (operation == READ)
blkif->st_rd_sect += preq.nr_sects;
else if (operation & WRITE)
blkif->st_wr_sect += preq.nr_sects;
return 0;
fail_flush:
xen_blkbk_unmap(pending_req);
fail_response:
/* Haven't submitted any bio's yet. */
make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
free_req(pending_req);
msleep(1); /* back off a bit */
return -EIO;
fail_put_bio:
for (i = 0; i < nbio; i++)
bio_put(biolist[i]);
__end_block_io_op(pending_req, -EINVAL);
msleep(1); /* back off a bit */
return -EIO;
}
/*
* Put a response on the ring on how the operation fared.
*/
static void make_response(struct xen_blkif *blkif, u64 id,
unsigned short op, int st)
{
struct blkif_response resp;
unsigned long flags;
union blkif_back_rings *blk_rings = &blkif->blk_rings;
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);
spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
if (notify)
notify_remote_via_irq(blkif->irq);
}
static int __init xen_blkif_init(void)
{
int i, mmap_pages;
int rc = 0;
if (!xen_domain())
return -ENODEV;
blkbk = kzalloc(sizeof(struct xen_blkbk), GFP_KERNEL);
if (!blkbk) {
pr_alert(DRV_PFX "%s: out of memory!\n", __func__);
return -ENOMEM;
}
mmap_pages = xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST;
blkbk->pending_reqs = kzalloc(sizeof(blkbk->pending_reqs[0]) *
xen_blkif_reqs, GFP_KERNEL);
blkbk->pending_grant_handles = kmalloc(sizeof(blkbk->pending_grant_handles[0]) *
mmap_pages, GFP_KERNEL);
blkbk->pending_pages = kzalloc(sizeof(blkbk->pending_pages[0]) *
mmap_pages, GFP_KERNEL);
if (!blkbk->pending_reqs || !blkbk->pending_grant_handles ||
!blkbk->pending_pages) {
rc = -ENOMEM;
goto out_of_memory;
}
for (i = 0; i < mmap_pages; i++) {
blkbk->pending_grant_handles[i] = BLKBACK_INVALID_HANDLE;
blkbk->pending_pages[i] = alloc_page(GFP_KERNEL);
if (blkbk->pending_pages[i] == NULL) {
rc = -ENOMEM;
goto out_of_memory;
}
}
rc = xen_blkif_interface_init();
if (rc)
goto failed_init;
INIT_LIST_HEAD(&blkbk->pending_free);
spin_lock_init(&blkbk->pending_free_lock);
init_waitqueue_head(&blkbk->pending_free_wq);
for (i = 0; i < xen_blkif_reqs; i++)
list_add_tail(&blkbk->pending_reqs[i].free_list,
&blkbk->pending_free);
rc = xen_blkif_xenbus_init();
if (rc)
goto failed_init;
return 0;
out_of_memory:
pr_alert(DRV_PFX "%s: out of memory\n", __func__);
failed_init:
kfree(blkbk->pending_reqs);
kfree(blkbk->pending_grant_handles);
if (blkbk->pending_pages) {
for (i = 0; i < mmap_pages; i++) {
if (blkbk->pending_pages[i])
__free_page(blkbk->pending_pages[i]);
}
kfree(blkbk->pending_pages);
}
kfree(blkbk);
blkbk = NULL;
return rc;
}
module_init(xen_blkif_init);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("xen-backend:vbd");