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block: Quiesce old aio context during bdrv_set_aio_context
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The fact that the bs->aio_context is changing can confuse the dataplane
iothread, because of the now fine granularity aio context lock.
bdrv_drain should rather be a bdrv_drained_begin/end pair, but since
bs->aio_context is changing, we can just use aio_disable_external and
bdrv_parent_drained_begin.

Reported-by: Ed Swierk <[email protected]>
Signed-off-by: Fam Zheng <[email protected]>
Acked-by: Stefan Hajnoczi <[email protected]>
Reviewed-by: Stefan Hajnoczi <[email protected]>
Reviewed-by: Kevin Wolf <[email protected]>
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Fam Zheng committed Apr 11, 2017
1 parent 14e9559 commit aabf591
Showing 1 changed file with 5 additions and 2 deletions.
7 changes: 5 additions & 2 deletions block.c
Original file line number Diff line number Diff line change
Expand Up @@ -4396,11 +4396,12 @@ void bdrv_attach_aio_context(BlockDriverState *bs,

void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
{
AioContext *ctx;
AioContext *ctx = bdrv_get_aio_context(bs);

aio_disable_external(ctx);
bdrv_parent_drained_begin(bs);
bdrv_drain(bs); /* ensure there are no in-flight requests */

ctx = bdrv_get_aio_context(bs);
while (aio_poll(ctx, false)) {
/* wait for all bottom halves to execute */
}
Expand All @@ -4412,6 +4413,8 @@ void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
*/
aio_context_acquire(new_context);
bdrv_attach_aio_context(bs, new_context);
bdrv_parent_drained_end(bs);
aio_enable_external(ctx);
aio_context_release(new_context);
}

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