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block: add aio_flush operation
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Instead stalling the VCPU while serving a cache flush try to do it
asynchronously.  Use our good old helper thread pool to issue an
asynchronous fdatasync for raw-posix.  Note that while Linux AIO
implements a fdatasync operation it is not useful for us because
it isn't actually implement in asynchronous fashion.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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Christoph Hellwig authored and Anthony Liguori committed Sep 11, 2009
1 parent 6f1953c commit b2e12bc
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Showing 6 changed files with 80 additions and 3 deletions.
40 changes: 40 additions & 0 deletions block.c
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,8 @@ static BlockDriverAIOCB *bdrv_aio_readv_em(BlockDriverState *bs,
static BlockDriverAIOCB *bdrv_aio_writev_em(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque);
static BlockDriverAIOCB *bdrv_aio_flush_em(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque);
static int bdrv_read_em(BlockDriverState *bs, int64_t sector_num,
uint8_t *buf, int nb_sectors);
static int bdrv_write_em(BlockDriverState *bs, int64_t sector_num,
Expand Down Expand Up @@ -138,6 +140,10 @@ void bdrv_register(BlockDriver *bdrv)
bdrv->bdrv_read = bdrv_read_em;
bdrv->bdrv_write = bdrv_write_em;
}

if (!bdrv->bdrv_aio_flush)
bdrv->bdrv_aio_flush = bdrv_aio_flush_em;

bdrv->next = first_drv;
first_drv = bdrv;
}
Expand Down Expand Up @@ -1552,6 +1558,21 @@ int bdrv_aio_multiwrite(BlockDriverState *bs, BlockRequest *reqs, int num_reqs)
return -1;
}

BlockDriverAIOCB *bdrv_aio_flush(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque)
{
BlockDriver *drv = bs->drv;

if (!drv)
return NULL;

/*
* Note that unlike bdrv_flush the driver is reponsible for flushing a
* backing image if it exists.
*/
return drv->bdrv_aio_flush(bs, cb, opaque);
}

void bdrv_aio_cancel(BlockDriverAIOCB *acb)
{
acb->pool->cancel(acb);
Expand Down Expand Up @@ -1642,6 +1663,25 @@ static BlockDriverAIOCB *bdrv_aio_writev_em(BlockDriverState *bs,
return bdrv_aio_rw_vector(bs, sector_num, qiov, nb_sectors, cb, opaque, 1);
}

static BlockDriverAIOCB *bdrv_aio_flush_em(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque)
{
BlockDriverAIOCBSync *acb;

acb = qemu_aio_get(&bdrv_em_aio_pool, bs, cb, opaque);
acb->is_write = 1; /* don't bounce in the completion hadler */
acb->qiov = NULL;
acb->bounce = NULL;
acb->ret = 0;

if (!acb->bh)
acb->bh = qemu_bh_new(bdrv_aio_bh_cb, acb);

bdrv_flush(bs);
qemu_bh_schedule(acb->bh);
return &acb->common;
}

/**************************************************************/
/* sync block device emulation */

Expand Down
2 changes: 2 additions & 0 deletions block.h
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,8 @@ BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState *bs, int64_t sector_num,
BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, int64_t sector_num,
QEMUIOVector *iov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque);
BlockDriverAIOCB *bdrv_aio_flush(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque);
void bdrv_aio_cancel(BlockDriverAIOCB *acb);

typedef struct BlockRequest {
Expand Down
3 changes: 2 additions & 1 deletion block/raw-posix-aio.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,8 +17,9 @@
#define QEMU_AIO_READ 0x0001
#define QEMU_AIO_WRITE 0x0002
#define QEMU_AIO_IOCTL 0x0004
#define QEMU_AIO_FLUSH 0x0008
#define QEMU_AIO_TYPE_MASK \
(QEMU_AIO_READ|QEMU_AIO_WRITE|QEMU_AIO_IOCTL)
(QEMU_AIO_READ|QEMU_AIO_WRITE|QEMU_AIO_IOCTL|QEMU_AIO_FLUSH)

/* AIO flags */
#define QEMU_AIO_MISALIGNED 0x1000
Expand Down
17 changes: 17 additions & 0 deletions block/raw-posix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -574,6 +574,18 @@ static BlockDriverAIOCB *raw_aio_writev(BlockDriverState *bs,
cb, opaque, QEMU_AIO_WRITE);
}

static BlockDriverAIOCB *raw_aio_flush(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque)
{
BDRVRawState *s = bs->opaque;

if (fd_open(bs) < 0)
return NULL;

return paio_submit(bs, s->aio_ctx, s->fd, 0, NULL, 0,
cb, opaque, QEMU_AIO_FLUSH);
}

static void raw_close(BlockDriverState *bs)
{
BDRVRawState *s = bs->opaque;
Expand Down Expand Up @@ -749,6 +761,7 @@ static BlockDriver bdrv_raw = {

.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,

.bdrv_truncate = raw_truncate,
.bdrv_getlength = raw_getlength,
Expand Down Expand Up @@ -1002,6 +1015,7 @@ static BlockDriver bdrv_host_device = {

.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,

.bdrv_read = raw_read,
.bdrv_write = raw_write,
Expand Down Expand Up @@ -1096,6 +1110,7 @@ static BlockDriver bdrv_host_floppy = {

.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,

.bdrv_read = raw_read,
.bdrv_write = raw_write,
Expand Down Expand Up @@ -1176,6 +1191,7 @@ static BlockDriver bdrv_host_cdrom = {

.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,

.bdrv_read = raw_read,
.bdrv_write = raw_write,
Expand Down Expand Up @@ -1295,6 +1311,7 @@ static BlockDriver bdrv_host_cdrom = {

.bdrv_aio_readv = raw_aio_readv,
.bdrv_aio_writev = raw_aio_writev,
.bdrv_aio_flush = raw_aio_flush,

.bdrv_read = raw_read,
.bdrv_write = raw_write,
Expand Down
2 changes: 2 additions & 0 deletions block_int.h
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,8 @@ struct BlockDriver {
BlockDriverAIOCB *(*bdrv_aio_writev)(BlockDriverState *bs,
int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
BlockDriverCompletionFunc *cb, void *opaque);
BlockDriverAIOCB *(*bdrv_aio_flush)(BlockDriverState *bs,
BlockDriverCompletionFunc *cb, void *opaque);

int (*bdrv_aio_multiwrite)(BlockDriverState *bs, BlockRequest *reqs,
int num_reqs);
Expand Down
19 changes: 17 additions & 2 deletions posix-aio-compat.c
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,16 @@ static size_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)
return aiocb->aio_nbytes;
}

static size_t handle_aiocb_flush(struct qemu_paiocb *aiocb)
{
int ret;

ret = fdatasync(aiocb->aio_fildes);
if (ret == -1)
return -errno;
return 0;
}

#ifdef CONFIG_PREADV

static ssize_t
Expand Down Expand Up @@ -330,6 +340,9 @@ static void *aio_thread(void *unused)
case QEMU_AIO_WRITE:
ret = handle_aiocb_rw(aiocb);
break;
case QEMU_AIO_FLUSH:
ret = handle_aiocb_flush(aiocb);
break;
case QEMU_AIO_IOCTL:
ret = handle_aiocb_ioctl(aiocb);
break;
Expand Down Expand Up @@ -530,8 +543,10 @@ BlockDriverAIOCB *paio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
acb->aio_type = type;
acb->aio_fildes = fd;
acb->ev_signo = SIGUSR2;
acb->aio_iov = qiov->iov;
acb->aio_niov = qiov->niov;
if (qiov) {
acb->aio_iov = qiov->iov;
acb->aio_niov = qiov->niov;
}
acb->aio_nbytes = nb_sectors * 512;
acb->aio_offset = sector_num * 512;

Expand Down

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