block: add aio_flush operation
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>
diff --git a/block.c b/block.c
index da0930c..0c6a97b 100644
--- a/block.c
+++ b/block.c
@@ -54,6 +54,8 @@
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,
@@ -138,6 +140,10 @@
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;
}
@@ -1552,6 +1558,21 @@
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);
@@ -1642,6 +1663,25 @@
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 */
