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block/mirror: Wait for in-flight op conflicts 

This patch makes the mirror code differentiate between simply waiting
for any operation to complete (mirror_wait_for_free_in_flight_slot())
and specifically waiting for all operations touching a certain range of
the virtual disk to complete (mirror_wait_on_conflicts()).

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20180613181823.13618-5-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2018-06-13 20:18:13 +02:00
parent 12aa40822d
commit 1181e19a6d
1 changed files with 84 additions and 18 deletions
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102
block/mirror.c
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@ -14,6 +14,7 @@
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "qemu/coroutine.h"
#include "qemu/range.h"
#include "trace.h"
#include "block/blockjob_int.h"
#include "block/block_int.h"
@ -86,6 +87,7 @@ struct MirrorOp {
* mirror_co_discard() before yielding for the first time */
int64_t *bytes_handled;
bool is_pseudo_op;
CoQueue waiting_requests;
QTAILQ_ENTRY(MirrorOp) next;
@ -110,6 +112,41 @@ static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
}
}
static void coroutine_fn mirror_wait_on_conflicts(MirrorOp *self,
MirrorBlockJob *s,
uint64_t offset,
uint64_t bytes)
{
uint64_t self_start_chunk = offset / s->granularity;
uint64_t self_end_chunk = DIV_ROUND_UP(offset + bytes, s->granularity);
uint64_t self_nb_chunks = self_end_chunk - self_start_chunk;
while (find_next_bit(s->in_flight_bitmap, self_end_chunk,
self_start_chunk) < self_end_chunk &&
s->ret >= 0)
{
MirrorOp *op;
QTAILQ_FOREACH(op, &s->ops_in_flight, next) {
uint64_t op_start_chunk = op->offset / s->granularity;
uint64_t op_nb_chunks = DIV_ROUND_UP(op->offset + op->bytes,
s->granularity) -
op_start_chunk;
if (op == self) {
continue;
}
if (ranges_overlap(self_start_chunk, self_nb_chunks,
op_start_chunk, op_nb_chunks))
{
qemu_co_queue_wait(&op->waiting_requests, NULL);
break;
}
}
}
}
static void coroutine_fn mirror_iteration_done(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
@ -232,13 +269,22 @@ static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
return ret;
}
static inline void mirror_wait_for_io(MirrorBlockJob *s)
static inline void mirror_wait_for_free_in_flight_slot(MirrorBlockJob *s)
{
MirrorOp *op;
op = QTAILQ_FIRST(&s->ops_in_flight);
assert(op);
qemu_co_queue_wait(&op->waiting_requests, NULL);
QTAILQ_FOREACH(op, &s->ops_in_flight, next) {
/* Do not wait on pseudo ops, because it may in turn wait on
* some other operation to start, which may in fact be the
* caller of this function. Since there is only one pseudo op
* at any given time, we will always find some real operation
* to wait on. */
if (!op->is_pseudo_op) {
qemu_co_queue_wait(&op->waiting_requests, NULL);
return;
}
}
abort();
}
/* Perform a mirror copy operation.
@ -282,7 +328,7 @@ static void coroutine_fn mirror_co_read(void *opaque)
while (s->buf_free_count < nb_chunks) {
trace_mirror_yield_in_flight(s, op->offset, s->in_flight);
mirror_wait_for_io(s);
mirror_wait_for_free_in_flight_slot(s);
}
/* Now make a QEMUIOVector taking enough granularity-sized chunks
@ -382,8 +428,9 @@ static unsigned mirror_perform(MirrorBlockJob *s, int64_t offset,
static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
{
BlockDriverState *source = s->source;
int64_t offset, first_chunk;
uint64_t delay_ns = 0;
MirrorOp *pseudo_op;
int64_t offset;
uint64_t delay_ns = 0, ret = 0;
/* At least the first dirty chunk is mirrored in one iteration. */
int nb_chunks = 1;
bool write_zeroes_ok = bdrv_can_write_zeroes_with_unmap(blk_bs(s->target));
@ -399,11 +446,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
}
bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
first_chunk = offset / s->granularity;
while (test_bit(first_chunk, s->in_flight_bitmap)) {
trace_mirror_yield_in_flight(s, offset, s->in_flight);
mirror_wait_for_io(s);
}
mirror_wait_on_conflicts(NULL, s, offset, 1);
job_pause_point(&s->common.job);
@ -440,6 +483,21 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
nb_chunks * s->granularity);
bdrv_dirty_bitmap_unlock(s->dirty_bitmap);
/* Before claiming an area in the in-flight bitmap, we have to
* create a MirrorOp for it so that conflicting requests can wait
* for it. mirror_perform() will create the real MirrorOps later,
* for now we just create a pseudo operation that will wake up all
* conflicting requests once all real operations have been
* launched. */
pseudo_op = g_new(MirrorOp, 1);
*pseudo_op = (MirrorOp){
.offset = offset,
.bytes = nb_chunks * s->granularity,
.is_pseudo_op = true,
};
qemu_co_queue_init(&pseudo_op->waiting_requests);
QTAILQ_INSERT_TAIL(&s->ops_in_flight, pseudo_op, next);
bitmap_set(s->in_flight_bitmap, offset / s->granularity, nb_chunks);
while (nb_chunks > 0 && offset < s->bdev_length) {
int ret;
@ -475,11 +533,12 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
while (s->in_flight >= MAX_IN_FLIGHT) {
trace_mirror_yield_in_flight(s, offset, s->in_flight);
mirror_wait_for_io(s);
mirror_wait_for_free_in_flight_slot(s);
}
if (s->ret < 0) {
return 0;
ret = 0;
goto fail;
}
io_bytes = mirror_clip_bytes(s, offset, io_bytes);
@ -494,7 +553,14 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
nb_chunks -= DIV_ROUND_UP(io_bytes, s->granularity);
delay_ns = block_job_ratelimit_get_delay(&s->common, io_bytes_acct);
}
return delay_ns;
ret = delay_ns;
fail:
QTAILQ_REMOVE(&s->ops_in_flight, pseudo_op, next);
qemu_co_queue_restart_all(&pseudo_op->waiting_requests);
g_free(pseudo_op);
return ret;
}
static void mirror_free_init(MirrorBlockJob *s)
@ -521,7 +587,7 @@ static void mirror_free_init(MirrorBlockJob *s)
static void mirror_wait_for_all_io(MirrorBlockJob *s)
{
while (s->in_flight > 0) {
mirror_wait_for_io(s);
mirror_wait_for_free_in_flight_slot(s);
}
}
@ -676,7 +742,7 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
if (s->in_flight >= MAX_IN_FLIGHT) {
trace_mirror_yield(s, UINT64_MAX, s->buf_free_count,
s->in_flight);
mirror_wait_for_io(s);
mirror_wait_for_free_in_flight_slot(s);
continue;
}
@ -849,7 +915,7 @@ static void coroutine_fn mirror_run(void *opaque)
if (s->in_flight >= MAX_IN_FLIGHT || s->buf_free_count == 0 ||
(cnt == 0 && s->in_flight > 0)) {
trace_mirror_yield(s, cnt, s->buf_free_count, s->in_flight);
mirror_wait_for_io(s);
mirror_wait_for_free_in_flight_slot(s);
continue;
} else if (cnt != 0) {
delay_ns = mirror_iteration(s);