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OpenCloudOS-Kernel/drivers/block/xen-blkback/blkback.c

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/******************************************************************************
*
* 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 "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(pos, rbtree, node) \
for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node); \
&(pos)->node != NULL; \
(pos) = container_of(rb_next(&(pos)->node), typeof(*(pos)), node))
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;
int ret = 0;
int segs_to_unmap = 0;
foreach_grant(persistent_gnt, 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;
rb_erase(&persistent_gnt->node, root);
kfree(persistent_gnt);
num--;
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);
segs_to_unmap = 0;
}
}
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;
persistent_gnt->page = alloc_page(GFP_KERNEL);
if (!persistent_gnt->page) {
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.dev = req->u.rw.handle;
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");
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