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From 0fbb0c87628bef2cb4d1b7748d67020dde50cdef Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Thu, 9 Jun 2022 17:47:11 +0100
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Subject: [PATCH 1/2] linux-aio: fix unbalanced plugged counter in
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laio_io_unplug()
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 199: linux-aio: fix unbalanced plugged counter in laio_io_unplug()
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RH-Commit: [1/2] f518df755090289905898a36922992288688e338
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RH-Bugzilla: 2105410
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Hanna Reitz <hreitz@redhat.com>
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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Every laio_io_plug() call has a matching laio_io_unplug() call. There is
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a plugged counter that tracks the number of levels of plugging and
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allows for nesting.
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The plugged counter must reflect the balance between laio_io_plug() and
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laio_io_unplug() calls accurately. Otherwise I/O stalls occur since
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io_submit(2) calls are skipped while plugged.
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Reported-by: Nikolay Tenev <nt@storpool.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
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Message-id: 20220609164712.1539045-2-stefanha@redhat.com
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Cc: Stefano Garzarella <sgarzare@redhat.com>
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Fixes: 68d7946648 ("linux-aio: add `dev_max_batch` parameter to laio_io_unplug()")
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[Stefano Garzarella suggested adding a Fixes tag.
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--Stefan]
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit f387cac5af030a58ac5a0dacf64cab5e5a4fe5c7)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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block/linux-aio.c | 4 +++-
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1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/block/linux-aio.c b/block/linux-aio.c
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index f53ae72e21..77f17ad596 100644
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--- a/block/linux-aio.c
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+++ b/block/linux-aio.c
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@@ -360,8 +360,10 @@ void laio_io_unplug(BlockDriverState *bs, LinuxAioState *s,
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uint64_t dev_max_batch)
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{
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assert(s->io_q.plugged);
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+ s->io_q.plugged--;
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+
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if (s->io_q.in_queue >= laio_max_batch(s, dev_max_batch) ||
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- (--s->io_q.plugged == 0 &&
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+ (!s->io_q.plugged &&
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!s->io_q.blocked && !QSIMPLEQ_EMPTY(&s->io_q.pending))) {
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ioq_submit(s);
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}
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--
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2.35.3
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