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[Qemu-devel] [PATCH v3 11/12] block: Block "device IO" during bdrv_drain
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [PATCH v3 11/12] block: Block "device IO" during bdrv_drain and bdrv_drain_all |
Date: |
Fri, 15 May 2015 14:04:27 +0800 |
We don't want new requests from guest, so block the operation around the
nested poll.
It also avoids looping forever when iothread is submitting a lot of requests.
Signed-off-by: Fam Zheng <address@hidden>
---
block/io.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/block/io.c b/block/io.c
index 1ce62c4..b23a83f 100644
--- a/block/io.c
+++ b/block/io.c
@@ -286,12 +286,21 @@ static bool bdrv_drain_one(BlockDriverState *bs)
*
* Note that unlike bdrv_drain_all(), the caller must hold the BlockDriverState
* AioContext.
+ *
+ * Devices are paused to avoid looping forever because otherwise they could
+ * keep submitting more requests.
*/
void bdrv_drain(BlockDriverState *bs)
{
+ Error *blocker = NULL;
+
+ error_setg(&blocker, "bdrv_drain in progress");
+ bdrv_op_block(bs, BLOCK_OP_TYPE_DEVICE_IO, blocker);
while (bdrv_drain_one(bs)) {
/* Keep iterating */
}
+ bdrv_op_unblock(bs, BLOCK_OP_TYPE_DEVICE_IO, blocker);
+ error_free(blocker);
}
/*
@@ -303,14 +312,20 @@ void bdrv_drain(BlockDriverState *bs)
* Note that completion of an asynchronous I/O operation can trigger any
* number of other I/O operations on other devices---for example a coroutine
* can be arbitrarily complex and a constant flow of I/O can come until the
- * coroutine is complete. Because of this, it is not possible to have a
- * function to drain a single device's I/O queue.
+ * coroutine is complete. Because of this, we must call bdrv_drain_one in a
+ * loop.
+ *
+ * We explicitly pause block jobs and devices to prevent them from submitting
+ * more requests.
*/
void bdrv_drain_all(void)
{
/* Always run first iteration so any pending completion BHs run */
bool busy = true;
BlockDriverState *bs = NULL;
+ Error *blocker = NULL;
+
+ error_setg(&blocker, "bdrv_drain_all in progress");
while ((bs = bdrv_next(bs))) {
AioContext *aio_context = bdrv_get_aio_context(bs);
@@ -319,6 +334,7 @@ void bdrv_drain_all(void)
if (bs->job) {
block_job_pause(bs->job);
}
+ bdrv_op_block(bs, BLOCK_OP_TYPE_DEVICE_IO, blocker);
aio_context_release(aio_context);
}
@@ -343,8 +359,10 @@ void bdrv_drain_all(void)
if (bs->job) {
block_job_resume(bs->job);
}
+ bdrv_op_unblock(bs, BLOCK_OP_TYPE_DEVICE_IO, blocker);
aio_context_release(aio_context);
}
+ error_free(blocker);
}
/**
--
2.4.0
- Re: [Qemu-devel] [PATCH v3 01/12] block: Add op blocker type "device IO", (continued)
- [Qemu-devel] [PATCH v3 02/12] block: Add op blocker notifier list, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 03/12] block-backend: Add blk_op_blocker_add_notifier, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 06/12] nbd-server: Clear "can_read" when "device io" blocker is set, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 05/12] virtio-blk: Don't handle output when there is "device IO" op blocker, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 08/12] blockdev: Block device IO during external snapshot transaction, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 09/12] blockdev: Block device IO during drive-backup transaction, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 07/12] blockdev: Block device IO during internal snapshot transaction, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 11/12] block: Block "device IO" during bdrv_drain and bdrv_drain_all,
Fam Zheng <=
- [Qemu-devel] [PATCH v3 10/12] blockdev: Block device IO during blockdev-backup transaction, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 04/12] virtio-blk: Move complete_request to 'ops' structure, Fam Zheng, 2015/05/15
- [Qemu-devel] [PATCH v3 12/12] virtio-scsi-dataplane: Add "device IO" op blocker listener, Fam Zheng, 2015/05/15