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linux-aio: fix unbalanced plugged counter in laio_io_unplug()

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Every laio_io_plug() call has a matching laio_io_unplug() call. There is
a plugged counter that tracks the number of levels of plugging and
allows for nesting.

The plugged counter must reflect the balance between laio_io_plug() and
laio_io_unplug() calls accurately. Otherwise I/O stalls occur since
io_submit(2) calls are skipped while plugged.

Reported-by: Nikolay Tenev <nt@storpool.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20220609164712.1539045-2-stefanha@redhat.com
Cc: Stefano Garzarella <sgarzare@redhat.com>
Fixes: 68d7946648 ("linux-aio: add `dev_max_batch` parameter to laio_io_unplug()")
[Stefano Garzarella suggested adding a Fixes tag.
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2022-06-09 17:47:11 +01:00
parent 78e27dfa8d
commit f387cac5af
1 changed files with 3 additions and 1 deletions
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4
block/linux-aio.c
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@ -363,8 +363,10 @@ void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s,
uint64_t dev_max_batch) uint64_t dev_max_batch)
{ {
assert(s->io_q.plugged); assert(s->io_q.plugged);
s->io_q.plugged--;
if (s->io_q.in_queue >= laio_max_batch(s, dev_max_batch) || if (s->io_q.in_queue >= laio_max_batch(s, dev_max_batch) ||
(--s->io_q.plugged == 0 && (!s->io_q.plugged &&
!s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending))) { !s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending))) {
ioq_submit(s); ioq_submit(s);
} }