* 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/osdep.h"
#include "qemu-common.h"
#include "block/aio.h"
#include "qemu/queue.h"
+#include "block/block.h"
#include "block/raw-aio.h"
#include "qemu/event_notifier.h"
+#include "qemu/coroutine.h"
+#include "qapi/error.h"
#include <libaio.h>
*/
#define MAX_EVENTS 128
-#define MAX_QUEUED_IO 128
-
struct qemu_laiocb {
- BlockDriverAIOCB common;
- struct qemu_laio_state *ctx;
+ BlockAIOCB common;
+ Coroutine *co;
+ LinuxAioState *ctx;
struct iocb iocb;
ssize_t ret;
size_t nbytes;
QEMUIOVector *qiov;
bool is_read;
- QLIST_ENTRY(qemu_laiocb) node;
+ QSIMPLEQ_ENTRY(qemu_laiocb) next;
};
typedef struct {
- struct iocb *iocbs[MAX_QUEUED_IO];
int plugged;
- unsigned int size;
- unsigned int idx;
+ unsigned int in_queue;
+ unsigned int in_flight;
+ bool blocked;
+ QSIMPLEQ_HEAD(, qemu_laiocb) pending;
} LaioQueue;
-struct qemu_laio_state {
+struct LinuxAioState {
+ AioContext *aio_context;
+
io_context_t ctx;
EventNotifier e;
- /* io queue for submit at batch */
+ /* io queue for submit at batch. Protected by AioContext lock. */
LaioQueue io_q;
- /* I/O completion processing */
+ /* I/O completion processing. Only runs in I/O thread. */
QEMUBH *completion_bh;
- struct io_event events[MAX_EVENTS];
int event_idx;
int event_max;
};
+static void ioq_submit(LinuxAioState *s);
+
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).
*/
-static void qemu_laio_process_completion(struct qemu_laio_state *s,
- struct qemu_laiocb *laiocb)
+static void qemu_laio_process_completion(struct qemu_laiocb *laiocb)
{
int ret;
qemu_iovec_memset(laiocb->qiov, ret, 0,
laiocb->qiov->size - ret);
} else {
- ret = -EINVAL;
+ ret = -ENOSPC;
}
}
+ }
+ laiocb->ret = ret;
+ if (laiocb->co) {
+ /* If the coroutine is already entered it must be in ioq_submit() and
+ * will notice laio->ret has been filled in when it eventually runs
+ * later. Coroutines cannot be entered recursively so avoid doing
+ * that!
+ */
+ if (!qemu_coroutine_entered(laiocb->co)) {
+ aio_co_wake(laiocb->co);
+ }
+ } else {
laiocb->common.cb(laiocb->common.opaque, ret);
+ qemu_aio_unref(laiocb);
}
+}
+
+/**
+ * aio_ring buffer which is shared between userspace and kernel.
+ *
+ * This copied from linux/fs/aio.c, common header does not exist
+ * but AIO exists for ages so we assume ABI is stable.
+ */
+struct aio_ring {
+ unsigned id; /* kernel internal index number */
+ unsigned nr; /* number of io_events */
+ unsigned head; /* Written to by userland or by kernel. */
+ unsigned tail;
+
+ unsigned magic;
+ unsigned compat_features;
+ unsigned incompat_features;
+ unsigned header_length; /* size of aio_ring */
+
+ struct io_event io_events[0];
+};
+
+/**
+ * io_getevents_peek:
+ * @ctx: AIO context
+ * @events: pointer on events array, output value
+
+ * Returns the number of completed events and sets a pointer
+ * on events array. This function does not update the internal
+ * ring buffer, only reads head and tail. When @events has been
+ * processed io_getevents_commit() must be called.
+ */
+static inline unsigned int io_getevents_peek(io_context_t ctx,
+ struct io_event **events)
+{
+ struct aio_ring *ring = (struct aio_ring *)ctx;
+ unsigned int head = ring->head, tail = ring->tail;
+ unsigned int nr;
- qemu_aio_release(laiocb);
+ nr = tail >= head ? tail - head : ring->nr - head;
+ *events = ring->io_events + head;
+ /* To avoid speculative loads of s->events[i] before observing tail.
+ Paired with smp_wmb() inside linux/fs/aio.c: aio_complete(). */
+ smp_rmb();
+
+ return nr;
+}
+
+/**
+ * io_getevents_commit:
+ * @ctx: AIO context
+ * @nr: the number of events on which head should be advanced
+ *
+ * Advances head of a ring buffer.
+ */
+static inline void io_getevents_commit(io_context_t ctx, unsigned int nr)
+{
+ struct aio_ring *ring = (struct aio_ring *)ctx;
+
+ if (nr) {
+ ring->head = (ring->head + nr) % ring->nr;
+ }
}
-/* The completion BH fetches completed I/O requests and invokes their
- * callbacks.
+/**
+ * io_getevents_advance_and_peek:
+ * @ctx: AIO context
+ * @events: pointer on events array, output value
+ * @nr: the number of events on which head should be advanced
+ *
+ * Advances head of a ring buffer and returns number of elements left.
+ */
+static inline unsigned int
+io_getevents_advance_and_peek(io_context_t ctx,
+ struct io_event **events,
+ unsigned int nr)
+{
+ io_getevents_commit(ctx, nr);
+ return io_getevents_peek(ctx, events);
+}
+
+/**
+ * qemu_laio_process_completions:
+ * @s: AIO state
+ *
+ * Fetches completed I/O requests and invokes their callbacks.
*
* The function is somewhat tricky because it supports nested event loops, for
* example when a request callback invokes aio_poll(). In order to do this,
- * the completion events array and index are kept in qemu_laio_state. The BH
- * reschedules itself as long as there are completions pending so it will
- * either be called again in a nested event loop or will be called after all
- * events have been completed. When there are no events left to complete, the
- * BH returns without rescheduling.
+ * indices are kept in LinuxAioState. Function schedules BH completion so it
+ * can be called again in a nested event loop. When there are no events left
+ * to complete the BH is being canceled.
*/
-static void qemu_laio_completion_bh(void *opaque)
+static void qemu_laio_process_completions(LinuxAioState *s)
{
- struct qemu_laio_state *s = opaque;
-
- /* Fetch more completion events when empty */
- if (s->event_idx == s->event_max) {
- do {
- struct timespec ts = { 0 };
- s->event_max = io_getevents(s->ctx, MAX_EVENTS, MAX_EVENTS,
- s->events, &ts);
- } while (s->event_max == -EINTR);
-
- s->event_idx = 0;
- if (s->event_max <= 0) {
- s->event_max = 0;
- return; /* no more events */
- }
- }
+ struct io_event *events;
/* Reschedule so nested event loops see currently pending completions */
qemu_bh_schedule(s->completion_bh);
- /* Process completion events */
- while (s->event_idx < s->event_max) {
- struct iocb *iocb = s->events[s->event_idx].obj;
- struct qemu_laiocb *laiocb =
+ while ((s->event_max = io_getevents_advance_and_peek(s->ctx, &events,
+ s->event_idx))) {
+ for (s->event_idx = 0; s->event_idx < s->event_max; ) {
+ struct iocb *iocb = events[s->event_idx].obj;
+ struct qemu_laiocb *laiocb =
container_of(iocb, struct qemu_laiocb, iocb);
- laiocb->ret = io_event_ret(&s->events[s->event_idx]);
- s->event_idx++;
+ laiocb->ret = io_event_ret(&events[s->event_idx]);
+
+ /* Change counters one-by-one because we can be nested. */
+ s->io_q.in_flight--;
+ s->event_idx++;
+ qemu_laio_process_completion(laiocb);
+ }
+ }
+
+ qemu_bh_cancel(s->completion_bh);
- qemu_laio_process_completion(s, laiocb);
+ /* If we are nested we have to notify the level above that we are done
+ * by setting event_max to zero, upper level will then jump out of it's
+ * own `for` loop. If we are the last all counters droped to zero. */
+ s->event_max = 0;
+ s->event_idx = 0;
+}
+
+static void qemu_laio_process_completions_and_submit(LinuxAioState *s)
+{
+ qemu_laio_process_completions(s);
+
+ aio_context_acquire(s->aio_context);
+ if (!s->io_q.plugged && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
+ ioq_submit(s);
}
+ aio_context_release(s->aio_context);
+}
+
+static void qemu_laio_completion_bh(void *opaque)
+{
+ LinuxAioState *s = opaque;
+
+ qemu_laio_process_completions_and_submit(s);
}
static void qemu_laio_completion_cb(EventNotifier *e)
{
- struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e);
+ LinuxAioState *s = container_of(e, LinuxAioState, e);
if (event_notifier_test_and_clear(&s->e)) {
- qemu_bh_schedule(s->completion_bh);
+ qemu_laio_process_completions_and_submit(s);
+ }
+}
+
+static bool qemu_laio_poll_cb(void *opaque)
+{
+ EventNotifier *e = opaque;
+ LinuxAioState *s = container_of(e, LinuxAioState, e);
+ struct io_event *events;
+
+ if (!io_getevents_peek(s->ctx, &events)) {
+ return false;
}
+
+ qemu_laio_process_completions_and_submit(s);
+ return true;
}
-static void laio_cancel(BlockDriverAIOCB *blockacb)
+static void laio_cancel(BlockAIOCB *blockacb)
{
struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb;
struct io_event event;
int ret;
- if (laiocb->ret != -EINPROGRESS)
+ 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;
+ laiocb->ret = -ECANCELED;
+ if (ret != 0) {
+ /* iocb is not cancelled, cb will be called by the event loop later */
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->e);
- }
+ laiocb->common.cb(laiocb->common.opaque, laiocb->ret);
}
static const AIOCBInfo laio_aiocb_info = {
.aiocb_size = sizeof(struct qemu_laiocb),
- .cancel = laio_cancel,
+ .cancel_async = laio_cancel,
};
static void ioq_init(LaioQueue *io_q)
{
- io_q->size = MAX_QUEUED_IO;
- io_q->idx = 0;
+ QSIMPLEQ_INIT(&io_q->pending);
io_q->plugged = 0;
+ io_q->in_queue = 0;
+ io_q->in_flight = 0;
+ io_q->blocked = false;
}
-static int ioq_submit(struct qemu_laio_state *s)
+static void ioq_submit(LinuxAioState *s)
{
- int ret, i = 0;
- int len = s->io_q.idx;
+ int ret, len;
+ struct qemu_laiocb *aiocb;
+ struct iocb *iocbs[MAX_EVENTS];
+ QSIMPLEQ_HEAD(, qemu_laiocb) completed;
do {
- ret = io_submit(s->ctx, len, s->io_q.iocbs);
- } while (i++ < 3 && ret == -EAGAIN);
+ if (s->io_q.in_flight >= MAX_EVENTS) {
+ break;
+ }
+ len = 0;
+ QSIMPLEQ_FOREACH(aiocb, &s->io_q.pending, next) {
+ iocbs[len++] = &aiocb->iocb;
+ if (s->io_q.in_flight + len >= MAX_EVENTS) {
+ break;
+ }
+ }
- /* empty io queue */
- s->io_q.idx = 0;
+ ret = io_submit(s->ctx, len, iocbs);
+ if (ret == -EAGAIN) {
+ break;
+ }
+ if (ret < 0) {
+ /* Fail the first request, retry the rest */
+ aiocb = QSIMPLEQ_FIRST(&s->io_q.pending);
+ QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next);
+ s->io_q.in_queue--;
+ aiocb->ret = ret;
+ qemu_laio_process_completion(aiocb);
+ continue;
+ }
- if (ret < 0) {
- i = 0;
- } else {
- i = ret;
+ s->io_q.in_flight += ret;
+ s->io_q.in_queue -= ret;
+ aiocb = container_of(iocbs[ret - 1], struct qemu_laiocb, iocb);
+ QSIMPLEQ_SPLIT_AFTER(&s->io_q.pending, aiocb, next, &completed);
+ } while (ret == len && !QSIMPLEQ_EMPTY(&s->io_q.pending));
+ s->io_q.blocked = (s->io_q.in_queue > 0);
+
+ if (s->io_q.in_flight) {
+ /* We can try to complete something just right away if there are
+ * still requests in-flight. */
+ qemu_laio_process_completions(s);
+ /*
+ * Even we have completed everything (in_flight == 0), the queue can
+ * have still pended requests (in_queue > 0). We do not attempt to
+ * repeat submission to avoid IO hang. The reason is simple: s->e is
+ * still set and completion callback will be called shortly and all
+ * pended requests will be submitted from there.
+ */
}
+}
- for (; i < len; i++) {
- struct qemu_laiocb *laiocb =
- container_of(s->io_q.iocbs[i], struct qemu_laiocb, iocb);
+void laio_io_plug(BlockDriverState *bs, LinuxAioState *s)
+{
+ s->io_q.plugged++;
+}
- laiocb->ret = (ret < 0) ? ret : -EIO;
- qemu_laio_process_completion(s, laiocb);
+void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s)
+{
+ assert(s->io_q.plugged);
+ if (--s->io_q.plugged == 0 &&
+ !s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending)) {
+ ioq_submit(s);
}
- return ret;
}
-static void ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb)
+static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
+ int type)
{
- unsigned int idx = s->io_q.idx;
+ LinuxAioState *s = laiocb->ctx;
+ struct iocb *iocbs = &laiocb->iocb;
+ QEMUIOVector *qiov = laiocb->qiov;
- s->io_q.iocbs[idx++] = iocb;
- s->io_q.idx = idx;
+ 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;
+ /* Currently Linux kernel does not support other operations */
+ default:
+ fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
+ __func__, type);
+ return -EIO;
+ }
+ io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
- /* submit immediately if queue is full */
- if (idx == s->io_q.size) {
+ QSIMPLEQ_INSERT_TAIL(&s->io_q.pending, laiocb, next);
+ s->io_q.in_queue++;
+ if (!s->io_q.blocked &&
+ (!s->io_q.plugged ||
+ s->io_q.in_flight + s->io_q.in_queue >= MAX_EVENTS)) {
ioq_submit(s);
}
-}
-void laio_io_plug(BlockDriverState *bs, void *aio_ctx)
-{
- struct qemu_laio_state *s = aio_ctx;
-
- s->io_q.plugged++;
+ return 0;
}
-int laio_io_unplug(BlockDriverState *bs, void *aio_ctx, bool unplug)
+int coroutine_fn laio_co_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
+ uint64_t offset, QEMUIOVector *qiov, int type)
{
- struct qemu_laio_state *s = aio_ctx;
- int ret = 0;
-
- assert(s->io_q.plugged > 0 || !unplug);
-
- if (unplug && --s->io_q.plugged > 0) {
- return 0;
+ int ret;
+ struct qemu_laiocb laiocb = {
+ .co = qemu_coroutine_self(),
+ .nbytes = qiov->size,
+ .ctx = s,
+ .ret = -EINPROGRESS,
+ .is_read = (type == QEMU_AIO_READ),
+ .qiov = qiov,
+ };
+
+ ret = laio_do_submit(fd, &laiocb, offset, type);
+ if (ret < 0) {
+ return ret;
}
- if (s->io_q.idx > 0) {
- ret = ioq_submit(s);
+ if (laiocb.ret == -EINPROGRESS) {
+ qemu_coroutine_yield();
}
-
- return ret;
+ return laiocb.ret;
}
-BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
+BlockAIOCB *laio_submit(BlockDriverState *bs, LinuxAioState *s, int fd,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
- BlockDriverCompletionFunc *cb, void *opaque, int type)
+ BlockCompletionFunc *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;
+ off_t offset = sector_num * BDRV_SECTOR_SIZE;
+ int ret;
laiocb = qemu_aio_get(&laio_aiocb_info, bs, cb, opaque);
- laiocb->nbytes = nb_sectors * 512;
+ laiocb->nbytes = nb_sectors * BDRV_SECTOR_SIZE;
laiocb->ctx = s;
laiocb->ret = -EINPROGRESS;
laiocb->is_read = (type == QEMU_AIO_READ);
laiocb->qiov = qiov;
- 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;
- /* Currently Linux kernel does not support other operations */
- default:
- fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
- __func__, type);
- goto out_free_aiocb;
+ ret = laio_do_submit(fd, laiocb, offset, type);
+ if (ret < 0) {
+ qemu_aio_unref(laiocb);
+ return NULL;
}
- io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
- if (!s->io_q.plugged) {
- if (io_submit(s->ctx, 1, &iocbs) < 0) {
- goto out_free_aiocb;
- }
- } else {
- ioq_enqueue(s, iocbs);
- }
return &laiocb->common;
-
-out_free_aiocb:
- qemu_aio_release(laiocb);
- return NULL;
}
-void laio_detach_aio_context(void *s_, AioContext *old_context)
+void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context)
{
- struct qemu_laio_state *s = s_;
-
- aio_set_event_notifier(old_context, &s->e, NULL);
+ aio_set_event_notifier(old_context, &s->e, false, NULL, NULL);
qemu_bh_delete(s->completion_bh);
+ s->aio_context = NULL;
}
-void laio_attach_aio_context(void *s_, AioContext *new_context)
+void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context)
{
- struct qemu_laio_state *s = s_;
-
+ s->aio_context = new_context;
s->completion_bh = aio_bh_new(new_context, qemu_laio_completion_bh, s);
- aio_set_event_notifier(new_context, &s->e, qemu_laio_completion_cb);
+ aio_set_event_notifier(new_context, &s->e, false,
+ qemu_laio_completion_cb,
+ qemu_laio_poll_cb);
}
-void *laio_init(void)
+LinuxAioState *laio_init(Error **errp)
{
- struct qemu_laio_state *s;
+ int rc;
+ LinuxAioState *s;
s = g_malloc0(sizeof(*s));
- if (event_notifier_init(&s->e, false) < 0) {
+ rc = event_notifier_init(&s->e, false);
+ if (rc < 0) {
+ error_setg_errno(errp, -rc, "failed to to initialize event notifier");
goto out_free_state;
}
- if (io_setup(MAX_EVENTS, &s->ctx) != 0) {
+ rc = io_setup(MAX_EVENTS, &s->ctx);
+ if (rc < 0) {
+ error_setg_errno(errp, -rc, "failed to create linux AIO context");
goto out_close_efd;
}
return NULL;
}
-void laio_cleanup(void *s_)
+void laio_cleanup(LinuxAioState *s)
{
- struct qemu_laio_state *s = s_;
-
event_notifier_cleanup(&s->e);
if (io_destroy(s->ctx) != 0) {
projects / qemu.git / blobdiff