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block/mirror: Convert to coroutines

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In order to talk to the source BDS (and maybe in the future to the
target BDS as well) directly, we need to convert our existing AIO
requests into coroutine I/O requests.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20180613181823.13618-3-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2018-06-13 20:18:11 +02:00
parent 4295c5fc61
commit 2e1990b26e
1 changed files with 90 additions and 62 deletions
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152
block/mirror.c
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@ -78,6 +78,10 @@ typedef struct MirrorOp {
QEMUIOVector qiov;
int64_t offset;
uint64_t bytes;
/* The pointee is set by mirror_co_read(), mirror_co_zero(), and
* mirror_co_discard() before yielding for the first time */
int64_t *bytes_handled;
} MirrorOp;
typedef enum MirrorMethod {
@ -99,7 +103,7 @@ static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
}
}
static void mirror_iteration_done(MirrorOp *op, int ret)
static void coroutine_fn mirror_iteration_done(MirrorOp *op, int ret)
{
MirrorBlockJob *s = op->s;
struct iovec *iov;
@ -136,9 +140,8 @@ static void mirror_iteration_done(MirrorOp *op, int ret)
}
}
static void mirror_write_complete(void *opaque, int ret)
static void coroutine_fn mirror_write_complete(MirrorOp *op, int ret)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
aio_context_acquire(blk_get_aio_context(s->common.blk));
@ -155,9 +158,8 @@ static void mirror_write_complete(void *opaque, int ret)
aio_context_release(blk_get_aio_context(s->common.blk));
}
static void mirror_read_complete(void *opaque, int ret)
static void coroutine_fn mirror_read_complete(MirrorOp *op, int ret)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
aio_context_acquire(blk_get_aio_context(s->common.blk));
@ -172,8 +174,9 @@ static void mirror_read_complete(void *opaque, int ret)
mirror_iteration_done(op, ret);
} else {
blk_aio_pwritev(s->target, op->offset, &op->qiov,
0, mirror_write_complete, op);
ret = blk_co_pwritev(s->target, op->offset,
op->qiov.size, &op->qiov, 0);
mirror_write_complete(op, ret);
}
aio_context_release(blk_get_aio_context(s->common.blk));
}
@ -230,60 +233,57 @@ static inline void mirror_wait_for_io(MirrorBlockJob *s)
s->waiting_for_io = false;
}
/* Submit async read while handling COW.
* Returns: The number of bytes copied after and including offset,
* excluding any bytes copied prior to offset due to alignment.
* This will be @bytes if no alignment is necessary, or
* (new_end - offset) if tail is rounded up or down due to
* alignment or buffer limit.
/* Perform a mirror copy operation.
*
* *op->bytes_handled is set to the number of bytes copied after and
* including offset, excluding any bytes copied prior to offset due
* to alignment. This will be op->bytes if no alignment is necessary,
* or (new_end - op->offset) if the tail is rounded up or down due to
* alignment or buffer limit.
*/
static uint64_t mirror_do_read(MirrorBlockJob *s, int64_t offset,
uint64_t bytes)
static void coroutine_fn mirror_co_read(void *opaque)
{
MirrorOp *op = opaque;
MirrorBlockJob *s = op->s;
BlockBackend *source = s->common.blk;
int nb_chunks;
uint64_t ret;
MirrorOp *op;
uint64_t max_bytes;
max_bytes = s->granularity * s->max_iov;
/* We can only handle as much as buf_size at a time. */
bytes = MIN(s->buf_size, MIN(max_bytes, bytes));
assert(bytes);
assert(bytes < BDRV_REQUEST_MAX_BYTES);
ret = bytes;
op->bytes = MIN(s->buf_size, MIN(max_bytes, op->bytes));
assert(op->bytes);
assert(op->bytes < BDRV_REQUEST_MAX_BYTES);
*op->bytes_handled = op->bytes;
if (s->cow_bitmap) {
ret += mirror_cow_align(s, &offset, &bytes);
*op->bytes_handled += mirror_cow_align(s, &op->offset, &op->bytes);
}
assert(bytes <= s->buf_size);
/* Cannot exceed BDRV_REQUEST_MAX_BYTES + INT_MAX */
assert(*op->bytes_handled <= UINT_MAX);
assert(op->bytes <= s->buf_size);
/* The offset is granularity-aligned because:
* 1) Caller passes in aligned values;
* 2) mirror_cow_align is used only when target cluster is larger. */
assert(QEMU_IS_ALIGNED(offset, s->granularity));
assert(QEMU_IS_ALIGNED(op->offset, s->granularity));
/* The range is sector-aligned, since bdrv_getlength() rounds up. */
assert(QEMU_IS_ALIGNED(bytes, BDRV_SECTOR_SIZE));
nb_chunks = DIV_ROUND_UP(bytes, s->granularity);
assert(QEMU_IS_ALIGNED(op->bytes, BDRV_SECTOR_SIZE));
nb_chunks = DIV_ROUND_UP(op->bytes, s->granularity);
while (s->buf_free_count < nb_chunks) {
trace_mirror_yield_in_flight(s, offset, s->in_flight);
trace_mirror_yield_in_flight(s, op->offset, s->in_flight);
mirror_wait_for_io(s);
}
/* Allocate a MirrorOp that is used as an AIO callback. */
op = g_new(MirrorOp, 1);
op->s = s;
op->offset = offset;
op->bytes = bytes;
/* Now make a QEMUIOVector taking enough granularity-sized chunks
* from s->buf_free.
*/
qemu_iovec_init(&op->qiov, nb_chunks);
while (nb_chunks-- > 0) {
MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
size_t remaining = bytes - op->qiov.size;
size_t remaining = op->bytes - op->qiov.size;
QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
s->buf_free_count--;
@ -292,53 +292,81 @@ static uint64_t mirror_do_read(MirrorBlockJob *s, int64_t offset,
/* Copy the dirty cluster. */
s->in_flight++;
s->bytes_in_flight += bytes;
trace_mirror_one_iteration(s, offset, bytes);
s->bytes_in_flight += op->bytes;
trace_mirror_one_iteration(s, op->offset, op->bytes);
blk_aio_preadv(source, offset, &op->qiov, 0, mirror_read_complete, op);
return ret;
ret = blk_co_preadv(source, op->offset, op->bytes, &op->qiov, 0);
mirror_read_complete(op, ret);
}
static void mirror_do_zero_or_discard(MirrorBlockJob *s,
int64_t offset,
uint64_t bytes,
bool is_discard)
static void coroutine_fn mirror_co_zero(void *opaque)
{
MirrorOp *op;
MirrorOp *op = opaque;
int ret;
/* Allocate a MirrorOp that is used as an AIO callback. The qiov is zeroed
* so the freeing in mirror_iteration_done is nop. */
op = g_new0(MirrorOp, 1);
op->s = s;
op->offset = offset;
op->bytes = bytes;
op->s->in_flight++;
op->s->bytes_in_flight += op->bytes;
*op->bytes_handled = op->bytes;
s->in_flight++;
s->bytes_in_flight += bytes;
if (is_discard) {
blk_aio_pdiscard(s->target, offset,
op->bytes, mirror_write_complete, op);
} else {
blk_aio_pwrite_zeroes(s->target, offset,
op->bytes, s->unmap ? BDRV_REQ_MAY_UNMAP : 0,
mirror_write_complete, op);
}
ret = blk_co_pwrite_zeroes(op->s->target, op->offset, op->bytes,
op->s->unmap ? BDRV_REQ_MAY_UNMAP : 0);
mirror_write_complete(op, ret);
}
static void coroutine_fn mirror_co_discard(void *opaque)
{
MirrorOp *op = opaque;
int ret;
op->s->in_flight++;
op->s->bytes_in_flight += op->bytes;
*op->bytes_handled = op->bytes;
ret = blk_co_pdiscard(op->s->target, op->offset, op->bytes);
mirror_write_complete(op, ret);
}
static unsigned mirror_perform(MirrorBlockJob *s, int64_t offset,
unsigned bytes, MirrorMethod mirror_method)
{
MirrorOp *op;
Coroutine *co;
int64_t bytes_handled = -1;
op = g_new(MirrorOp, 1);
*op = (MirrorOp){
.s = s,
.offset = offset,
.bytes = bytes,
.bytes_handled = &bytes_handled,
};
switch (mirror_method) {
case MIRROR_METHOD_COPY:
return mirror_do_read(s, offset, bytes);
co = qemu_coroutine_create(mirror_co_read, op);
break;
case MIRROR_METHOD_ZERO:
co = qemu_coroutine_create(mirror_co_zero, op);
break;
case MIRROR_METHOD_DISCARD:
mirror_do_zero_or_discard(s, offset, bytes,
mirror_method == MIRROR_METHOD_DISCARD);
return bytes;
co = qemu_coroutine_create(mirror_co_discard, op);
break;
default:
abort();
}
qemu_coroutine_enter(co);
/* At this point, ownership of op has been moved to the coroutine
* and the object may already be freed */
/* Assert that this value has been set */
assert(bytes_handled >= 0);
/* Same assertion as in mirror_co_read() (and for mirror_co_read()
* and mirror_co_discard(), bytes_handled == op->bytes, which
* is the @bytes parameter given to this function) */
assert(bytes_handled <= UINT_MAX);
return bytes_handled;
}
static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)