Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753992AbdF1EnE (ORCPT ); Wed, 28 Jun 2017 00:43:04 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:20385 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751693AbdF1Em6 (ORCPT ); Wed, 28 Jun 2017 00:42:58 -0400 From: Dongli Zhang To: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: konrad.wilk@oracle.com, roger.pau@citrix.com, boris.ostrovsky@oracle.com, jgross@suse.com Subject: [PATCH 1/1] xen/blkfront: always allocate grants first from per-queue persistent grants Date: Wed, 28 Jun 2017 12:43:03 +0800 Message-Id: <1498624983-6293-1-git-send-email-dongli.zhang@oracle.com> X-Mailer: git-send-email 2.7.4 X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2397 Lines: 65 This patch partially reverts 3df0e50 ("xen/blkfront: pseudo support for multi hardware queues/rings"). The xen-blkfront queue/ring might hang due to grants allocation failure in the situation when gnttab_free_head is almost empty while many persistent grants are reserved for this queue/ring. As persistent grants management was per-queue since 73716df ("xen/blkfront: make persistent grants pool per-queue"), we should always allocate from persistent grants first. Signed-off-by: Dongli Zhang --- drivers/block/xen-blkfront.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 3945963..d2b759f 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -713,6 +713,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri * existing persistent grants, or if we have to get new grants, * as there are not sufficiently many free. */ + bool new_persistent_gnts = false; struct scatterlist *sg; int num_sg, max_grefs, num_grant; @@ -724,12 +725,13 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri */ max_grefs += INDIRECT_GREFS(max_grefs); - /* - * We have to reserve 'max_grefs' grants because persistent - * grants are shared by all rings. - */ - if (max_grefs > 0) - if (gnttab_alloc_grant_references(max_grefs, &setup.gref_head) < 0) { + /* Check if we have enough persistent grants to allocate a requests */ + if (rinfo->persistent_gnts_c < max_grefs) { + new_persistent_gnts = true; + + if (gnttab_alloc_grant_references( + max_grefs - rinfo->persistent_gnts_c, + &setup.gref_head) < 0) { gnttab_request_free_callback( &rinfo->callback, blkif_restart_queue_callback, @@ -737,6 +739,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri max_grefs); return 1; } + } /* Fill out a communications ring structure. */ id = blkif_ring_get_request(rinfo, req, &ring_req); @@ -837,7 +840,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri if (unlikely(require_extra_req)) rinfo->shadow[extra_id].req = *extra_ring_req; - if (max_grefs > 0) + if (new_persistent_gnts) gnttab_free_grant_references(setup.gref_head); return 0; -- 2.7.4