From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755669AbbDGNSp (ORCPT ); Tue, 7 Apr 2015 09:18:45 -0400 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:54477 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754099AbbDGMwH (ORCPT ); Tue, 7 Apr 2015 08:52:07 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Roger Pau Monne , Konrad Rzeszutek Wilk , David Vrabel , Jens Axboe , Jiri Slaby Subject: [PATCH 3.12 085/155] xen-blkfront: revoke foreign access for grants not mapped by the backend Date: Tue, 7 Apr 2015 14:50:54 +0200 Message-Id: <381480fa7175e5990ff5c6903ac1e1ed9bb31917.1428411004.git.jslaby@suse.cz> X-Mailer: git-send-email 2.3.4 In-Reply-To: <9a548862b8a26cbccc14f2c6c9c3688813d8d14b.1428411003.git.jslaby@suse.cz> References: <9a548862b8a26cbccc14f2c6c9c3688813d8d14b.1428411003.git.jslaby@suse.cz> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Roger Pau Monne 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit fbe363c476afe8ec992d3baf682670a4bd1b6ce6 upstream. There's no need to keep the foreign access in a grant if it is not persistently mapped by the backend. This allows us to free grants that are not mapped by the backend, thus preventing blkfront from hoarding all grants. The main effect of this is that blkfront will only persistently map the same grants as the backend, and it will always try to use grants that are already mapped by the backend. Also the number of persistent grants in blkfront is the same as in blkback (and is controlled by the value in blkback). Signed-off-by: Roger Pau Monné Reviewed-by: David Vrabel Acked-by: Matt Wilson Cc: Konrad Rzeszutek Wilk Cc: David Vrabel Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Jens Axboe Signed-off-by: Jiri Slaby --- drivers/block/xen-blkfront.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index e85bc358e052..7b0500b020e8 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1013,13 +1013,38 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info, } /* Add the persistent grant into the list of free grants */ for (i = 0; i < nseg; i++) { - list_add(&s->grants_used[i]->node, &info->persistent_gnts); - info->persistent_gnts_c++; + if (gnttab_query_foreign_access(s->grants_used[i]->gref)) { + /* + * If the grant is still mapped by the backend (the + * backend has chosen to make this grant persistent) + * we add it at the head of the list, so it will be + * reused first. + */ + list_add(&s->grants_used[i]->node, &info->persistent_gnts); + info->persistent_gnts_c++; + } else { + /* + * If the grant is not mapped by the backend we end the + * foreign access and add it to the tail of the list, + * so it will not be picked again unless we run out of + * persistent grants. + */ + gnttab_end_foreign_access(s->grants_used[i]->gref, 0, 0UL); + s->grants_used[i]->gref = GRANT_INVALID_REF; + list_add_tail(&s->grants_used[i]->node, &info->persistent_gnts); + } } if (s->req.operation == BLKIF_OP_INDIRECT) { for (i = 0; i < INDIRECT_GREFS(nseg); i++) { - list_add(&s->indirect_grants[i]->node, &info->persistent_gnts); - info->persistent_gnts_c++; + if (gnttab_query_foreign_access(s->indirect_grants[i]->gref)) { + list_add(&s->indirect_grants[i]->node, &info->persistent_gnts); + info->persistent_gnts_c++; + } else { + gnttab_end_foreign_access(s->indirect_grants[i]->gref, 0, 0UL); + s->indirect_grants[i]->gref = GRANT_INVALID_REF; + list_add_tail(&s->indirect_grants[i]->node, + &info->persistent_gnts); + } } } } -- 2.3.4