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block: Unify order in drain functions

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Drain requests are propagated to child nodes, parent nodes and directly
to the AioContext. The order in which this happened was different
between all combinations of drain/drain_all and begin/end.

The correct order is to keep children only drained when their parents
are also drained. This means that at the start of a drained section, the
AioContext needs to be drained first, the parents second and only then
the children. The correct order for the end of a drained section is the
opposite.

This patch changes the three other functions to follow the example of
bdrv_drained_begin(), which is the only one that got it right.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2017-12-06 11:00:59 +01:00
parent 5280aa32e1
commit 60369b86c4
1 changed files with 8 additions and 4 deletions
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12
block/io.c
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@ -277,6 +277,7 @@ void bdrv_drained_begin(BlockDriverState *bs)
return;
}
/* Stop things in parent-to-child order */
if (atomic_fetch_inc(&bs->quiesce_counter) == 0) {
aio_disable_external(bdrv_get_aio_context(bs));
bdrv_parent_drained_begin(bs);
@ -297,8 +298,9 @@ void bdrv_drained_end(BlockDriverState *bs)
return;
}
bdrv_parent_drained_end(bs);
/* Re-enable things in child-to-parent order */
bdrv_drain_invoke(bs, false);
bdrv_parent_drained_end(bs);
aio_enable_external(bdrv_get_aio_context(bs));
}
@ -351,9 +353,10 @@ void bdrv_drain_all_begin(void)
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
/* Stop things in parent-to-child order */
aio_context_acquire(aio_context);
bdrv_parent_drained_begin(bs);
aio_disable_external(aio_context);
bdrv_parent_drained_begin(bs);
bdrv_drain_invoke(bs, true);
aio_context_release(aio_context);
@ -395,10 +398,11 @@ void bdrv_drain_all_end(void)
for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
AioContext *aio_context = bdrv_get_aio_context(bs);
/* Re-enable things in child-to-parent order */
aio_context_acquire(aio_context);
aio_enable_external(aio_context);
bdrv_parent_drained_end(bs);
bdrv_drain_invoke(bs, false);
bdrv_parent_drained_end(bs);
aio_enable_external(aio_context);
aio_context_release(aio_context);
}