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block: add bdrv_drain()

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Now that op blockers are in use, we can ensure that no other sources are
generating I/O on a BlockDriverState.  Therefore it is possible to drain
requests for a single BDS.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 1413889440-32577-7-git-send-email-stefanha@redhat.com
This commit is contained in:
Stefan Hajnoczi 2014-10-21 12:03:55 +01:00
parent dec7d421f8
commit 5b98db0ad3
2 changed files with 30 additions and 7 deletions
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36
block.c
View File

@ -1904,6 +1904,34 @@ static bool bdrv_requests_pending(BlockDriverState *bs)
return false;
}
static bool bdrv_drain_one(BlockDriverState *bs)
{
bool bs_busy;
bdrv_flush_io_queue(bs);
bdrv_start_throttled_reqs(bs);
bs_busy = bdrv_requests_pending(bs);
bs_busy |= aio_poll(bdrv_get_aio_context(bs), bs_busy);
return bs_busy;
}
/*
* Wait for pending requests to complete on a single BlockDriverState subtree
*
* See the warning in bdrv_drain_all(). This function can only be called if
* you are sure nothing can generate I/O because you have op blockers
* installed.
*
* Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
* AioContext.
*/
void bdrv_drain(BlockDriverState *bs)
{
while (bdrv_drain_one(bs)) {
/* Keep iterating */
}
}
/*
* Wait for pending requests to complete across all BlockDriverStates
*
@ -1927,16 +1955,10 @@ void bdrv_drain_all(void)
QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
AioContext *aio_context = bdrv_get_aio_context(bs);
bool bs_busy;
aio_context_acquire(aio_context);
bdrv_flush_io_queue(bs);
bdrv_start_throttled_reqs(bs);
bs_busy = bdrv_requests_pending(bs);
bs_busy |= aio_poll(aio_context, bs_busy);
busy |= bdrv_drain_one(bs);
aio_context_release(aio_context);
busy |= bs_busy;
}
}
}

1
include/block/block.h
View File

@ -334,6 +334,7 @@ int bdrv_flush(BlockDriverState *bs);
int coroutine_fn bdrv_co_flush(BlockDriverState *bs);
int bdrv_flush_all(void);
void bdrv_close_all(void);
void bdrv_drain(BlockDriverState *bs);
void bdrv_drain_all(void);
int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);