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 <stefa...@redhat.com>
---
block.c | 36 +++++++++++++++++++++++++++++-------
include/block/block.h | 1 +
2 files changed, 30 insertions(+), 7 deletions(-)
diff --git a/block.c b/block.c
index c5a251c..48305c4 100644
--- a/block.c
+++ b/block.c
@@ -1918,6 +1918,34 @@ 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
*
@@ -1941,16 +1969,10 @@ 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;
}
}
}
diff --git a/include/block/block.h b/include/block/block.h
index 3318f0d..61df804 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -372,6 +372,7 @@ 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);
--
1.9.3
