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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 22 Dec 2017 16:18:14 +0100
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Subject: [Qemu-devel] [PULL v3 03/35] block: Make bdrv_drain_invoke()
recursive
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This change separates bdrv_drain_invoke(), which calls the BlockDriver
drain callbacks, from bdrv_drain_recurse(). Instead, the function
performs its own recursion now.
One reason for this is that bdrv_drain_recurse() can be called multiple
times by bdrv_drain_all_begin(), but the callbacks may only be called
once. The separation is necessary to fix this bug.
The other reason is that we intend to go to a model where we call all
driver callbacks first, and only then start polling. This is not fully
achieved yet with this patch, as bdrv_drain_invoke() contains a
BDRV_POLL_WHILE() loop for the block driver callbacks, which can still
call callbacks for any unrelated event. It's a step in this direction
anyway.
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block/io.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/block/io.c b/block/io.c
index 6773926fc1..096468b761 100644
--- a/block/io.c
+++ b/block/io.c
@@ -175,8 +175,10 @@ static void coroutine_fn bdrv_drain_invoke_entry(void =
*opaque)
bdrv_wakeup(bs);
}
=20
+/* Recursively call BlockDriver.bdrv_co_drain_begin/end callbacks */
static void bdrv_drain_invoke(BlockDriverState *bs, bool begin)
{
+ BdrvChild *child, *tmp;
BdrvCoDrainData data =3D { .bs =3D bs, .done =3D false, .begin =3D beg=
in};
=20
if (!bs->drv || (begin && !bs->drv->bdrv_co_drain_begin) ||
@@ -187,6 +189,10 @@ static void bdrv_drain_invoke(BlockDriverState *bs, bo=
ol begin)
data.co =3D qemu_coroutine_create(bdrv_drain_invoke_entry, &data);
bdrv_coroutine_enter(bs, data.co);
BDRV_POLL_WHILE(bs, !data.done);
+
+ QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {
+ bdrv_drain_invoke(child->bs, begin);
+ }
}
=20
static bool bdrv_drain_recurse(BlockDriverState *bs, bool begin)
@@ -194,9 +200,6 @@ static bool bdrv_drain_recurse(BlockDriverState *bs, bo=
ol begin)
BdrvChild *child, *tmp;
bool waited;
=20
- /* Ensure any pending metadata writes are submitted to bs->file. */
- bdrv_drain_invoke(bs, begin);
-
/* Wait for drained requests to finish */
waited =3D BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
=20
@@ -279,6 +282,7 @@ void bdrv_drained_begin(BlockDriverState *bs)
bdrv_parent_drained_begin(bs);
}
=20
+ bdrv_drain_invoke(bs, true);
bdrv_drain_recurse(bs, true);
}
=20
@@ -294,6 +298,7 @@ void bdrv_drained_end(BlockDriverState *bs)
}
=20
bdrv_parent_drained_end(bs);
+ bdrv_drain_invoke(bs, false);
bdrv_drain_recurse(bs, false);
aio_enable_external(bdrv_get_aio_context(bs));
}
@@ -372,6 +377,8 @@ void bdrv_drain_all_begin(void)
aio_context_acquire(aio_context);
for (bs =3D bdrv_first(&it); bs; bs =3D bdrv_next(&it)) {
if (aio_context =3D=3D bdrv_get_aio_context(bs)) {
+ /* FIXME Calling this multiple times is wrong */
+ bdrv_drain_invoke(bs, true);
waited |=3D bdrv_drain_recurse(bs, true);
}
}
@@ -393,6 +400,7 @@ void bdrv_drain_all_end(void)
aio_context_acquire(aio_context);
aio_enable_external(aio_context);
bdrv_parent_drained_end(bs);
+ bdrv_drain_invoke(bs, false);
bdrv_drain_recurse(bs, false);
aio_context_release(aio_context);
}
--=20
2.13.6