@@ -2618,3 +2618,20 @@ void bdrv_flush_io_queue(BlockDriverState *bs)
}
bdrv_start_throttled_reqs(bs);
}
+
+void bdrv_drained_begin(BlockDriverState *bs)
+{
+ if (!bs->quiesce_counter++) {
+ aio_disable_external(bdrv_get_aio_context(bs));
+ }
+ bdrv_drain(bs);
+}
+
+void bdrv_drained_end(BlockDriverState *bs)
+{
+ assert(bs->quiesce_counter > 0);
+ if (--bs->quiesce_counter > 0) {
+ return;
+ }
+ aio_enable_external(bdrv_get_aio_context(bs));
+}
@@ -624,4 +624,23 @@ void bdrv_flush_io_queue(BlockDriverState *bs);
BlockAcctStats *bdrv_get_stats(BlockDriverState *bs);
+/**
+ * bdrv_drained_begin:
+ *
+ * Begin a quiesced section for exclusive access to the BDS, by disabling
+ * external request sources including NBD server and device model. Note that
+ * this doesn't block timers or coroutines from submitting more requests, which
+ * means block_job_pause is still necessary.
+ *
+ * This function can be recursive.
+ */
+void bdrv_drained_begin(BlockDriverState *bs);
+
+/**
+ * bdrv_drained_end:
+ *
+ * End a quiescent section started by bdrv_drained_begin().
+ */
+void bdrv_drained_end(BlockDriverState *bs);
+
#endif
@@ -456,6 +456,8 @@ struct BlockDriverState {
/* threshold limit for writes, in bytes. "High water mark". */
uint64_t write_threshold_offset;
NotifierWithReturn write_threshold_notifier;
+
+ int quiesce_counter;
};
static inline BlockDriverState *backing_bs(BlockDriverState *bs)
The semantics is that after bdrv_drained_begin(bs), bs will not get new external requests until the matching bdrv_drained_end(bs). Signed-off-by: Fam Zheng <famz@redhat.com> --- block/io.c | 17 +++++++++++++++++ include/block/block.h | 19 +++++++++++++++++++ include/block/block_int.h | 2 ++ 3 files changed, 38 insertions(+)