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/*
* Linux native AIO support.
*
* Copyright (C) 2009 IBM, Corp.
* Copyright (C) 2009 Red Hat, Inc.
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu-common.h"
#include "qemu-aio.h"
#include "block_int.h"
#include "block/raw-posix-aio.h"
#include <sys/eventfd.h>
#include <libaio.h>
/*
* Queue size (per-device).
*
* XXX: eventually we need to communicate this to the guest and/or make it
* tunable by the guest. If we get more outstanding requests at a time
* than this we will get EAGAIN from io_submit which is communicated to
* the guest as an I/O error.
*/
#define MAX_EVENTS 128
struct qemu_laiocb {
BlockDriverAIOCB common;
struct qemu_laio_state *ctx;
struct iocb iocb;
ssize_t ret;
size_t nbytes;
int async_context_id;
QLIST_ENTRY(qemu_laiocb) node;
};
struct qemu_laio_state {
io_context_t ctx;
int efd;
int count;
QLIST_HEAD(, qemu_laiocb) completed_reqs;
};
static inline ssize_t io_event_ret(struct io_event *ev)
{
return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
}
/*
* Completes an AIO request (calls the callback and frees the ACB).
* Be sure to be in the right AsyncContext before calling this function.
*/
static void qemu_laio_process_completion(struct qemu_laio_state *s,
struct qemu_laiocb *laiocb)
{
int ret;
s->count--;
ret = laiocb->ret;
if (ret != -ECANCELED) {
if (ret == laiocb->nbytes)
ret = 0;
else if (ret >= 0)
ret = -EINVAL;
laiocb->common.cb(laiocb->common.opaque, ret);
}
qemu_aio_release(laiocb);
}
/*
* Processes all queued AIO requests, i.e. requests that have return from OS
* but their callback was not called yet. Requests that cannot have their
* callback called in the current AsyncContext, remain in the queue.
*
* Returns 1 if at least one request could be completed, 0 otherwise.
*/
static int qemu_laio_process_requests(void *opaque)
{
struct qemu_laio_state *s = opaque;
struct qemu_laiocb *laiocb, *next;
int res = 0;
QLIST_FOREACH_SAFE (laiocb, &s->completed_reqs, node, next) {
if (laiocb->async_context_id == get_async_context_id()) {
qemu_laio_process_completion(s, laiocb);
QLIST_REMOVE(laiocb, node);
res = 1;
}
}
return res;
}
/*
* Puts a request in the completion queue so that its callback is called the
* next time when it's possible. If we already are in the right AsyncContext,
* the request is completed immediately instead.
*/
static void qemu_laio_enqueue_completed(struct qemu_laio_state *s,
struct qemu_laiocb* laiocb)
{
if (laiocb->async_context_id == get_async_context_id()) {
qemu_laio_process_completion(s, laiocb);
} else {
QLIST_INSERT_HEAD(&s->completed_reqs, laiocb, node);
}
}
static void qemu_laio_completion_cb(void *opaque)
{
struct qemu_laio_state *s = opaque;
while (1) {
struct io_event events[MAX_EVENTS];
uint64_t val;
ssize_t ret;
struct timespec ts = { 0 };
int nevents, i;
do {
ret = read(s->efd, &val, sizeof(val));
} while (ret == -1 && errno == EINTR);
if (ret == -1 && errno == EAGAIN)
break;
if (ret != 8)
break;
do {
nevents = io_getevents(s->ctx, val, MAX_EVENTS, events, &ts);
} while (nevents == -EINTR);
for (i = 0; i < nevents; i++) {
struct iocb *iocb = events[i].obj;
struct qemu_laiocb *laiocb =
container_of(iocb, struct qemu_laiocb, iocb);
laiocb->ret = io_event_ret(&events[i]);
qemu_laio_enqueue_completed(s, laiocb);
}
}
}
static int qemu_laio_flush_cb(void *opaque)
{
struct qemu_laio_state *s = opaque;
return (s->count > 0) ? 1 : 0;
}
static void laio_cancel(BlockDriverAIOCB *blockacb)
{
struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb;
struct io_event event;
int ret;
if (laiocb->ret != -EINPROGRESS)
return;
/*
* Note that as of Linux 2.6.31 neither the block device code nor any
* filesystem implements cancellation of AIO request.
* Thus the polling loop below is the normal code path.
*/
ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
if (ret == 0) {
laiocb->ret = -ECANCELED;
return;
}
/*
* We have to wait for the iocb to finish.
*
* The only way to get the iocb status update is by polling the io context.
* We might be able to do this slightly more optimal by removing the
* O_NONBLOCK flag.
*/
while (laiocb->ret == -EINPROGRESS)
qemu_laio_completion_cb(laiocb->ctx);
}
static AIOPool laio_pool = {
.aiocb_size = sizeof(struct qemu_laiocb),
.cancel = laio_cancel,
};
BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque, int type)
{
struct qemu_laio_state *s = aio_ctx;
struct qemu_laiocb *laiocb;
struct iocb *iocbs;
off_t offset = sector_num * 512;
laiocb = qemu_aio_get(&laio_pool, bs, cb, opaque);
if (!laiocb)
return NULL;
laiocb->nbytes = nb_sectors * 512;
laiocb->ctx = s;
laiocb->ret = -EINPROGRESS;
laiocb->async_context_id = get_async_context_id();
iocbs = &laiocb->iocb;
switch (type) {
case QEMU_AIO_WRITE:
io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset);
break;
case QEMU_AIO_READ:
io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset);
break;
default:
fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
__func__, type);
goto out_free_aiocb;
}
io_set_eventfd(&laiocb->iocb, s->efd);
s->count++;
if (io_submit(s->ctx, 1, &iocbs) < 0)
goto out_dec_count;
return &laiocb->common;
out_free_aiocb:
qemu_aio_release(laiocb);
out_dec_count:
s->count--;
return NULL;
}
void *laio_init(void)
{
struct qemu_laio_state *s;
s = qemu_mallocz(sizeof(*s));
QLIST_INIT(&s->completed_reqs);
s->efd = eventfd(0, 0);
if (s->efd == -1)
goto out_free_state;
fcntl(s->efd, F_SETFL, O_NONBLOCK);
if (io_setup(MAX_EVENTS, &s->ctx) != 0)
goto out_close_efd;
qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
qemu_laio_flush_cb, qemu_laio_process_requests, s);
return s;
out_close_efd:
close(s->efd);
out_free_state:
qemu_free(s);
return NULL;
}
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