From 0fbb0c87628bef2cb4d1b7748d67020dde50cdef Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 9 Jun 2022 17:47:11 +0100 Subject: [PATCH 1/2] linux-aio: fix unbalanced plugged counter in laio_io_unplug() RH-Author: Stefan Hajnoczi RH-MergeRequest: 199: linux-aio: fix unbalanced plugged counter in laio_io_unplug() RH-Commit: [1/2] f518df755090289905898a36922992288688e338 RH-Bugzilla: 2105410 RH-Acked-by: Miroslav Rezanina RH-Acked-by: Hanna Reitz RH-Acked-by: Stefano Garzarella 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 Signed-off-by: Stefan Hajnoczi Reviewed-by: Stefano Garzarella Message-id: 20220609164712.1539045-2-stefanha@redhat.com Cc: Stefano Garzarella 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 (cherry picked from commit f387cac5af030a58ac5a0dacf64cab5e5a4fe5c7) Signed-off-by: Stefan Hajnoczi --- block/linux-aio.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/block/linux-aio.c b/block/linux-aio.c index f53ae72e21..77f17ad596 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -360,8 +360,10 @@ void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s, uint64_t dev_max_batch) { assert(s->io_q.plugged); + s->io_q.plugged--; + 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))) { ioq_submit(s); } -- 2.35.3