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authorFam Zheng <famz@redhat.com>2015-11-09 18:16:53 +0800
committerKevin Wolf <kwolf@redhat.com>2015-11-12 16:22:43 +0100
commit67da1dc5ce696c7b309b1db100da7d94292847b7 (patch)
treec28226815e2d495cee3106dcf557667751adec10 /include
parent83c98d7b924eab36a0a2c7813731dbef439a91d3 (diff)
block: Introduce BlockDriver.bdrv_drain callback
Drivers can have internal request sources that generate IO, like the need_check_timer in QED. Since we want quiesced periods that contain nested event loops in block layer, we need to have a way to disable such event sources. Block drivers must implement the "bdrv_drain" callback if it has any internal sources that can generate I/O activity, like a timer or a worker thread (even in a library) that can schedule QEMUBH in an asynchronous callback. Update the comments of bdrv_drain and bdrv_drained_begin accordingly. Like bdrv_requests_pending(), we should consider all the children of bs. Before, the while loop just works, as bdrv_requests_pending() already tracks its children; now we mustn't miss the callback, so recurse down explicitly. Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 1447064214-29930-9-git-send-email-famz@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/block/block_int.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 84991d9973..3a24913a7e 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -295,6 +295,12 @@ struct BlockDriver {
*/
int (*bdrv_probe_geometry)(BlockDriverState *bs, HDGeometry *geo);
+ /**
+ * Drain and stop any internal sources of requests in the driver, and
+ * remain so until next I/O callback (e.g. bdrv_co_writev) is called.
+ */
+ void (*bdrv_drain)(BlockDriverState *bs);
+
QLIST_ENTRY(BlockDriver) list;
};