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Tue, 7 Apr 2020 14:26:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1586269604; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=w1oyqq+zCvCh6mTLn6BonctyU5iY9vpQjAPS0QgDUmI=; b=FZ1q05W9nrDwWNa8+vxE5BMKPNdSIU3zGI8RKkJwqVEfiF8IyYqilGT3pVcUYkxGcfQnPh Cut9pms1cIk13t+AtedW61j31UorRwG6O2eBnNulnuOu87kRz4Xkh5n+VgoCtNV87exdHC 3zM923Gt/unwhMQzNvSPlqzou99eLSk= X-MC-Unique: ILjn3mooOjmMSa722qjq4w-1 From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 6/7] block: Fix blk->in_flight during blk_wait_while_drained() Date: Tue, 7 Apr 2020 16:26:15 +0200 Message-Id: <20200407142616.7961-7-kwolf@redhat.com> In-Reply-To: <20200407142616.7961-1-kwolf@redhat.com> References: <20200407142616.7961-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" Waiting in blk_wait_while_drained() while blk->in_flight is increased for the current request is wrong because it will cause the drain operation to deadlock. This patch makes sure that blk_wait_while_drained() is called with blk->in_flight increased exactly once for the current request, and that it temporarily decreases the counter while it waits. Fixes: cf3129323f900ef5ddbccbe86e4fa801e88c566e Signed-off-by: Kevin Wolf Reviewed-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Max Reitz Message-Id: <20200407121259.21350-4-kwolf@redhat.com> Signed-off-by: Kevin Wolf --- block/block-backend.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index 610dbfa0b2..38ae413826 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1140,10 +1140,15 @@ static int blk_check_byte_request(BlockBackend *blk= , int64_t offset, return 0; } =20 +/* To be called between exactly one pair of blk_inc/dec_in_flight() */ static void coroutine_fn blk_wait_while_drained(BlockBackend *blk) { + assert(blk->in_flight > 0); + if (blk->quiesce_counter && !blk->disable_request_queuing) { + blk_dec_in_flight(blk); qemu_co_queue_wait(&blk->queued_requests, NULL); + blk_inc_in_flight(blk); } } =20 @@ -1418,12 +1423,6 @@ static void blk_aio_read_entry(void *opaque) BlkRwCo *rwco =3D &acb->rwco; QEMUIOVector *qiov =3D rwco->iobuf; =20 - if (rwco->blk->quiesce_counter) { - blk_dec_in_flight(rwco->blk); - blk_wait_while_drained(rwco->blk); - blk_inc_in_flight(rwco->blk); - } - assert(qiov->size =3D=3D acb->bytes); rwco->ret =3D blk_do_preadv(rwco->blk, rwco->offset, acb->bytes, qiov, rwco->flags); @@ -1436,12 +1435,6 @@ static void blk_aio_write_entry(void *opaque) BlkRwCo *rwco =3D &acb->rwco; QEMUIOVector *qiov =3D rwco->iobuf; =20 - if (rwco->blk->quiesce_counter) { - blk_dec_in_flight(rwco->blk); - blk_wait_while_drained(rwco->blk); - blk_inc_in_flight(rwco->blk); - } - assert(!qiov || qiov->size =3D=3D acb->bytes); rwco->ret =3D blk_do_pwritev_part(rwco->blk, rwco->offset, acb->bytes, qiov, 0, rwco->flags); --=20 2.20.1