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qed: Use CoQueue for serialising allocations 

Now that we're running in coroutine context, the ad-hoc serialisation
code (which drops a request that has to wait out of coroutine context)
can be replaced by a CoQueue.

This means that when we resume a serialised request, it is running in
coroutine context again and its I/O isn't blocking any more.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2016-11-18 15:32:17 +01:00
parent 89f89709c7
commit 0806c3b5dd
2 changed files with 19 additions and 33 deletions
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49
block/qed.c
View File

@ -269,16 +269,10 @@ static void qed_plug_allocating_write_reqs(BDRVQEDState *s)
static void qed_unplug_allocating_write_reqs(BDRVQEDState *s)
{
QEDAIOCB *acb;
assert(s->allocating_write_reqs_plugged);
s->allocating_write_reqs_plugged = false;
acb = QSIMPLEQ_FIRST(&s->allocating_write_reqs);
if (acb) {
qed_aio_start_io(acb);
}
qemu_co_enter_next(&s->allocating_write_reqs);
}
static void qed_clear_need_check(void *opaque, int ret)
@ -305,7 +299,7 @@ static void qed_need_check_timer_cb(void *opaque)
BDRVQEDState *s = opaque;
/* The timer should only fire when allocating writes have drained */
assert(!QSIMPLEQ_FIRST(&s->allocating_write_reqs));
assert(!s->allocating_acb);
trace_qed_need_check_timer_cb(s);
@ -388,7 +382,7 @@ static int bdrv_qed_do_open(BlockDriverState *bs, QDict *options, int flags,
int ret;
s->bs = bs;
QSIMPLEQ_INIT(&s->allocating_write_reqs);
qemu_co_queue_init(&s->allocating_write_reqs);
ret = bdrv_pread(bs->file, 0, &le_header, sizeof(le_header));
if (ret < 0) {
@ -910,11 +904,6 @@ static void qed_aio_complete_bh(void *opaque)
qed_release(s);
}
static void qed_resume_alloc_bh(void *opaque)
{
qed_aio_start_io(opaque);
}
static void qed_aio_complete(QEDAIOCB *acb, int ret)
{
BDRVQEDState *s = acb_to_s(acb);
@ -942,13 +931,10 @@ static void qed_aio_complete(QEDAIOCB *acb, int ret)
* next request in the queue. This ensures that we don't cycle through
* requests multiple times but rather finish one at a time completely.
*/
if (acb == QSIMPLEQ_FIRST(&s->allocating_write_reqs)) {
QEDAIOCB *next_acb;
QSIMPLEQ_REMOVE_HEAD(&s->allocating_write_reqs, next);
next_acb = QSIMPLEQ_FIRST(&s->allocating_write_reqs);
if (next_acb) {
aio_bh_schedule_oneshot(bdrv_get_aio_context(acb->common.bs),
qed_resume_alloc_bh, next_acb);
if (acb == s->allocating_acb) {
s->allocating_acb = NULL;
if (!qemu_co_queue_empty(&s->allocating_write_reqs)) {
qemu_co_enter_next(&s->allocating_write_reqs);
} else if (s->header.features & QED_F_NEED_CHECK) {
qed_start_need_check_timer(s);
}
@ -1124,17 +1110,18 @@ static int qed_aio_write_alloc(QEDAIOCB *acb, size_t len)
int ret;
/* Cancel timer when the first allocating request comes in */
if (QSIMPLEQ_EMPTY(&s->allocating_write_reqs)) {
if (s->allocating_acb == NULL) {
qed_cancel_need_check_timer(s);
}
/* Freeze this request if another allocating write is in progress */
if (acb != QSIMPLEQ_FIRST(&s->allocating_write_reqs)) {
QSIMPLEQ_INSERT_TAIL(&s->allocating_write_reqs, acb, next);
}
if (acb != QSIMPLEQ_FIRST(&s->allocating_write_reqs) ||
s->allocating_write_reqs_plugged) {
return -EINPROGRESS; /* wait for existing request to finish */
if (s->allocating_acb != acb || s->allocating_write_reqs_plugged) {
if (s->allocating_acb != NULL) {
qemu_co_queue_wait(&s->allocating_write_reqs, NULL);
assert(s->allocating_acb == NULL);
}
s->allocating_acb = acb;
return -EAGAIN; /* start over with looking up table entries */
}
acb->cur_nclusters = qed_bytes_to_clusters(s,
@ -1313,10 +1300,8 @@ static void qed_aio_next_io(QEDAIOCB *acb)
ret = qed_aio_read_data(acb, ret, offset, len);
}
if (ret < 0) {
if (ret != -EINPROGRESS) {
qed_aio_complete(acb, ret);
}
if (ret < 0 && ret != -EAGAIN) {
qed_aio_complete(acb, ret);
return;
}
}

3
block/qed.h
View File

@ -163,7 +163,8 @@ typedef struct {
uint32_t l2_mask;
/* Allocating write request queue */
QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;
QEDAIOCB *allocating_acb;
CoQueue allocating_write_reqs;
bool allocating_write_reqs_plugged;
/* Periodic flush and clear need check flag */