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From 68265b080cec07c5a6ba6b1c6fbd867f4d9cf9ba Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Fri, 14 Sep 2018 10:55:34 +0200
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Subject: [PATCH 43/49] block-backend: Decrease in_flight only after callback
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <20180914105540.18077-37-kwolf@redhat.com>
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Patchwork-id: 82187
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O-Subject: [RHV-7.6 qemu-kvm-rhev PATCH 36/42] block-backend: Decrease in_flight only after callback
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Bugzilla: 1601212
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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Request callbacks can do pretty much anything, including operations that
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will yield from the coroutine (such as draining the backend). In that
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case, a decreased in_flight would be visible to other code and could
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lead to a drain completing while the callback hasn't actually completed
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yet.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Fam Zheng <famz@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/block-backend.c | 10 +++++++++-
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1 file changed, 9 insertions(+), 1 deletion(-)
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diff --git a/block/block-backend.c b/block/block-backend.c
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index 1adf76b..466bc27 100644
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--- a/block/block-backend.c
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+++ b/block/block-backend.c
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@@ -1341,8 +1341,16 @@ static const AIOCBInfo blk_aio_em_aiocb_info = {
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static void blk_aio_complete(BlkAioEmAIOCB *acb)
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{
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if (acb->has_returned) {
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- blk_dec_in_flight(acb->rwco.blk);
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+ if (qemu_get_current_aio_context() == qemu_get_aio_context()) {
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+ /* If we are in the main thread, the callback is allowed to unref
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+ * the BlockBackend, so we have to hold an additional reference */
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+ blk_ref(acb->rwco.blk);
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+ }
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acb->common.cb(acb->common.opaque, acb->rwco.ret);
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+ blk_dec_in_flight(acb->rwco.blk);
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+ if (qemu_get_current_aio_context() == qemu_get_aio_context()) {
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+ blk_unref(acb->rwco.blk);
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+ }
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qemu_aio_unref(acb);
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}
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}
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--
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1.8.3.1
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