Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756132Ab3HLK4Q (ORCPT ); Mon, 12 Aug 2013 06:56:16 -0400 Received: from smtp.eu.citrix.com ([46.33.159.39]:30697 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755579Ab3HLKz7 (ORCPT ); Mon, 12 Aug 2013 06:55:59 -0400 X-IronPort-AV: E=Sophos;i="4.89,861,1367971200"; d="scan'208";a="7708589" From: Roger Pau Monne To: , CC: Roger Pau Monne , Konrad Rzeszutek Wilk , David Vrabel Subject: [PATCH v2 2/2] xen-blkfront: revoke foreign access for grants not mapped by the backend Date: Mon, 12 Aug 2013 12:53:44 +0200 Message-ID: <1376304824-1967-3-git-send-email-roger.pau@citrix.com> X-Mailer: git-send-email 1.7.7.5 (Apple Git-26) In-Reply-To: <1376304824-1967-1-git-send-email-roger.pau@citrix.com> References: <1376304824-1967-1-git-send-email-roger.pau@citrix.com> 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 Content-Length: 3019 Lines: 75 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 --- drivers/block/xen-blkfront.c | 33 +++++++++++++++++++++++++++++---- 1 files changed, 29 insertions(+), 4 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index 187a437..bc9fc7d 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1016,13 +1016,38 @@ 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); + } } } } -- 1.7.7.5 (Apple Git-26) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/