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block: Defer .bdrv_drain_begin callback to polling phase 

We cannot allow aio_poll() in bdrv_drain_invoke(begin=true) until we're
done with propagating the drain through the graph and are doing the
single final BDRV_POLL_WHILE().

Just schedule the coroutine with the callback and increase bs->in_flight
to make sure that the polling phase will wait for it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2018-03-23 20:29:24 +01:00
parent 231281ab42
commit 0109e7e6f8
1 changed files with 23 additions and 5 deletions
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28
block/io.c
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@ -182,22 +182,40 @@ static void coroutine_fn bdrv_drain_invoke_entry(void *opaque)
/* Set data->done before reading bs->wakeup. */ /* Set data->done before reading bs->wakeup. */
atomic_mb_set(&data->done, true); atomic_mb_set(&data->done, true);
bdrv_wakeup(bs); bdrv_dec_in_flight(bs);
if (data->begin) {
g_free(data);
}
} }
/* Recursively call BlockDriver.bdrv_co_drain_begin/end callbacks */ /* Recursively call BlockDriver.bdrv_co_drain_begin/end callbacks */
static void bdrv_drain_invoke(BlockDriverState *bs, bool begin) static void bdrv_drain_invoke(BlockDriverState *bs, bool begin)
{ {
BdrvCoDrainData data = { .bs = bs, .done = false, .begin = begin}; BdrvCoDrainData *data;
if (!bs->drv || (begin && !bs->drv->bdrv_co_drain_begin) || if (!bs->drv || (begin && !bs->drv->bdrv_co_drain_begin) ||
(!begin && !bs->drv->bdrv_co_drain_end)) { (!begin && !bs->drv->bdrv_co_drain_end)) {
return; return;
} }
data.co = qemu_coroutine_create(bdrv_drain_invoke_entry, &data); data = g_new(BdrvCoDrainData, 1);
bdrv_coroutine_enter(bs, data.co); *data = (BdrvCoDrainData) {
BDRV_POLL_WHILE(bs, !data.done); .bs = bs,
.done = false,
.begin = begin
};
/* Make sure the driver callback completes during the polling phase for
* drain_begin. */
bdrv_inc_in_flight(bs);
data->co = qemu_coroutine_create(bdrv_drain_invoke_entry, data);
aio_co_schedule(bdrv_get_aio_context(bs), data->co);
if (!begin) {
BDRV_POLL_WHILE(bs, !data->done);
g_free(data);
}
} }
/* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */ /* Returns true if BDRV_POLL_WHILE() should go into a blocking aio_poll() */