From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB7B310E9 for ; Tue, 19 Jul 2022 09:57:15 +0000 (UTC) Received: from fraeml744-chm.china.huawei.com (unknown [172.18.147.206]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4LnDf149Xbz67T9q; Tue, 19 Jul 2022 17:52:41 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml744-chm.china.huawei.com (10.206.15.225) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 19 Jul 2022 11:57:12 +0200 Received: from localhost.localdomain (10.69.192.58) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 19 Jul 2022 10:57:10 +0100 From: John Garry To: , , , CC: , , , John Garry Subject: [PATCH] scsi: sd: Add a comment about limiting max_sectors to shost optimal limit Date: Tue, 19 Jul 2022 17:51:04 +0800 Message-ID: <1658224264-49972-1-git-send-email-john.garry@huawei.com> X-Mailer: git-send-email 2.8.1 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.69.192.58] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Add a comment about limiting the default the SCSI disk request_queue max_sectors initial value to that of the SCSI host optimal sectors limit. Suggested-by: Damien Le Moal Signed-off-by: John Garry diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 3eaee1f7aaca..ed9f43f9512e 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -3296,6 +3296,11 @@ static int sd_revalidate_disk(struct gendisk *disk) (sector_t)BLK_DEF_MAX_SECTORS); } + /* + * Limit default to SCSI host optimal sector limit if set. There may be + * an impact on performance for when the size of a request exceeds this + * host limit. + */ rw_max = min_not_zero(rw_max, sdp->host->opt_sectors); /* Do not exceed controller limit */ -- 2.35.3