From patchwork Thu Jan 30 21:30:59 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 11358759 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 631DF139A for ; Thu, 30 Jan 2020 21:33:24 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3924D20674 for ; Thu, 30 Jan 2020 21:33:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SOZCFPqV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3924D20674 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:39318 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixHRD-0000aA-7i for patchwork-qemu-devel@patchwork.kernel.org; Thu, 30 Jan 2020 16:33:23 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55914) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ixHPZ-0006ra-RG for qemu-devel@nongnu.org; Thu, 30 Jan 2020 16:31:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ixHPY-00050T-Dr for qemu-devel@nongnu.org; Thu, 30 Jan 2020 16:31:41 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:28565 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ixHPY-0004z4-96 for qemu-devel@nongnu.org; Thu, 30 Jan 2020 16:31:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580419899; 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=pQP9OA32VCmZvu+nXMW5sTI/63FgkAGA9WupDP5WqyE=; b=SOZCFPqV0y1RrAsuFb4bJpsLUGi6+QGRl/44tZJJduLL0aVJSpFL/fIf/uVxPWgYNfkdtN IzrYXC94jkqsESvJLAYxbutpl7jsbr2qESeohkirN0KgcQmcJdjRoNAlAaELbjYIakqlCY bqZinMTOT+b4jsZvKXVqMacNTf02n4Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-312-4gZiXK0JMAyL8Qb98S8e2g-1; Thu, 30 Jan 2020 16:31:37 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7C9511005513; Thu, 30 Jan 2020 21:31:36 +0000 (UTC) Received: from localhost (unknown [10.36.118.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id CB43B19488; Thu, 30 Jan 2020 21:31:30 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PULL 03/18] block/io: take bs->reqs_lock in bdrv_mark_request_serialising Date: Thu, 30 Jan 2020 21:30:59 +0000 Message-Id: <20200130213114.325157-4-stefanha@redhat.com> In-Reply-To: <20200130213114.325157-1-stefanha@redhat.com> References: <20200130213114.325157-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: 4gZiXK0JMAyL8Qb98S8e2g-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com 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: Kevin Wolf , Peter Maydell , qemu-block@nongnu.org, Peter Lieven , Julia Suvorova , Markus Armbruster , Max Reitz , Stefan Hajnoczi , Paolo Bonzini , Fam Zheng , Aarushi Mehta Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Paolo Bonzini bdrv_mark_request_serialising is writing the overlap_offset and overlap_bytes fields of BdrvTrackedRequest. Take bs->reqs_lock for the whole duration of it, and not just when waiting for serialising requests, so that tracked_request_overlaps does not look at a half-updated request. The new code does not unlock/relock around retries. This is unnecessary because a retry is always preceded by a CoQueue wait, which already releases and reacquires bs->reqs_lock. Reported-by: Peter Lieven Signed-off-by: Paolo Bonzini Message-id: 1578495356-46219-4-git-send-email-pbonzini@redhat.com Message-Id: <1578495356-46219-4-git-send-email-pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi --- block/io.c | 112 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 63 insertions(+), 49 deletions(-) diff --git a/block/io.c b/block/io.c index c466df8ed5..1eb2b2bddc 100644 --- a/block/io.c +++ b/block/io.c @@ -41,7 +41,6 @@ #define MAX_BOUNCE_BUFFER (32768 << BDRV_SECTOR_BITS) static void bdrv_parent_cb_resize(BlockDriverState *bs); -static bool coroutine_fn bdrv_wait_serialising_requests(BdrvTrackedRequest *self); static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes, BdrvRequestFlags flags); @@ -716,12 +715,69 @@ static void tracked_request_begin(BdrvTrackedRequest *req, qemu_co_mutex_unlock(&bs->reqs_lock); } +static bool tracked_request_overlaps(BdrvTrackedRequest *req, + int64_t offset, uint64_t bytes) +{ + /* aaaa bbbb */ + if (offset >= req->overlap_offset + req->overlap_bytes) { + return false; + } + /* bbbb aaaa */ + if (req->overlap_offset >= offset + bytes) { + return false; + } + return true; +} + +static bool coroutine_fn +bdrv_wait_serialising_requests_locked(BlockDriverState *bs, + BdrvTrackedRequest *self) +{ + BdrvTrackedRequest *req; + bool retry; + bool waited = false; + + do { + retry = false; + QLIST_FOREACH(req, &bs->tracked_requests, list) { + if (req == self || (!req->serialising && !self->serialising)) { + continue; + } + if (tracked_request_overlaps(req, self->overlap_offset, + self->overlap_bytes)) + { + /* Hitting this means there was a reentrant request, for + * example, a block driver issuing nested requests. This must + * never happen since it means deadlock. + */ + assert(qemu_coroutine_self() != req->co); + + /* If the request is already (indirectly) waiting for us, or + * will wait for us as soon as it wakes up, then just go on + * (instead of producing a deadlock in the former case). */ + if (!req->waiting_for) { + self->waiting_for = req; + qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock); + self->waiting_for = NULL; + retry = true; + waited = true; + break; + } + } + } + } while (retry); + return waited; +} + bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align) { + BlockDriverState *bs = req->bs; int64_t overlap_offset = req->offset & ~(align - 1); uint64_t overlap_bytes = ROUND_UP(req->offset + req->bytes, align) - overlap_offset; + bool waited; + qemu_co_mutex_lock(&bs->reqs_lock); if (!req->serialising) { atomic_inc(&req->bs->serialising_in_flight); req->serialising = true; @@ -729,7 +785,9 @@ bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align) req->overlap_offset = MIN(req->overlap_offset, overlap_offset); req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes); - return bdrv_wait_serialising_requests(req); + waited = bdrv_wait_serialising_requests_locked(bs, req); + qemu_co_mutex_unlock(&bs->reqs_lock); + return waited; } /** @@ -783,20 +841,6 @@ static int bdrv_get_cluster_size(BlockDriverState *bs) } } -static bool tracked_request_overlaps(BdrvTrackedRequest *req, - int64_t offset, uint64_t bytes) -{ - /* aaaa bbbb */ - if (offset >= req->overlap_offset + req->overlap_bytes) { - return false; - } - /* bbbb aaaa */ - if (req->overlap_offset >= offset + bytes) { - return false; - } - return true; -} - void bdrv_inc_in_flight(BlockDriverState *bs) { atomic_inc(&bs->in_flight); @@ -816,45 +860,15 @@ void bdrv_dec_in_flight(BlockDriverState *bs) static bool coroutine_fn bdrv_wait_serialising_requests(BdrvTrackedRequest *self) { BlockDriverState *bs = self->bs; - BdrvTrackedRequest *req; - bool retry; bool waited = false; if (!atomic_read(&bs->serialising_in_flight)) { return false; } - do { - retry = false; - qemu_co_mutex_lock(&bs->reqs_lock); - QLIST_FOREACH(req, &bs->tracked_requests, list) { - if (req == self || (!req->serialising && !self->serialising)) { - continue; - } - if (tracked_request_overlaps(req, self->overlap_offset, - self->overlap_bytes)) - { - /* Hitting this means there was a reentrant request, for - * example, a block driver issuing nested requests. This must - * never happen since it means deadlock. - */ - assert(qemu_coroutine_self() != req->co); - - /* If the request is already (indirectly) waiting for us, or - * will wait for us as soon as it wakes up, then just go on - * (instead of producing a deadlock in the former case). */ - if (!req->waiting_for) { - self->waiting_for = req; - qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock); - self->waiting_for = NULL; - retry = true; - waited = true; - break; - } - } - } - qemu_co_mutex_unlock(&bs->reqs_lock); - } while (retry); + qemu_co_mutex_lock(&bs->reqs_lock); + waited = bdrv_wait_serialising_requests_locked(bs, self); + qemu_co_mutex_unlock(&bs->reqs_lock); return waited; }