From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63A91C48BD5 for ; Tue, 25 Jun 2019 10:51:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2EECD215EA for ; Tue, 25 Jun 2019 10:51:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730040AbfFYKvR (ORCPT ); Tue, 25 Jun 2019 06:51:17 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:7318 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727924AbfFYKvQ (ORCPT ); Tue, 25 Jun 2019 06:51:16 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5PAghCp111969 for ; Tue, 25 Jun 2019 06:51:14 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 2tbguvm225-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 25 Jun 2019 06:51:14 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 25 Jun 2019 11:51:06 +0100 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5PAp5ij59441256 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 25 Jun 2019 10:51:05 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2D2F542047; Tue, 25 Jun 2019 10:51:05 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5960A4204B; Tue, 25 Jun 2019 10:51:04 +0000 (GMT) Received: from oc4120165700.ibm.com (unknown [9.152.97.9]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 25 Jun 2019 10:51:04 +0000 (GMT) Subject: Re: [PATCH V5 10/16] s390: zfcp_fc: use sg helper to operate scatterlist To: Ming Lei Cc: linux-scsi@vger.kernel.org, "Martin K . Petersen" , James Bottomley , Bart Van Assche , Hannes Reinecke , Christoph Hellwig , Jim Gill , Cathy Avery , "Ewan D . Milne" , Brian King , James Smart , "Juergen E . Fischer" , Michael Schmitz , Finn Thain , Greg Kroah-Hartman , devel@driverdev.osuosl.org, linux-usb@vger.kernel.org, Dan Carpenter , Benjamin Block , Martin Schwidefsky , Heiko Carstens , linux-s390@vger.kernel.org References: <20190618013757.22401-1-ming.lei@redhat.com> <20190618013757.22401-11-ming.lei@redhat.com> <95bfa1fb-d0eb-fc61-ecc0-001ae52a326f@linux.ibm.com> <20190625011902.GA23777@ming.t460p> From: Steffen Maier Date: Tue, 25 Jun 2019 12:51:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190625011902.GA23777@ming.t460p> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19062510-0012-0000-0000-0000032C35CD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19062510-0013-0000-0000-000021656A97 Message-Id: <93d3d89e-a9ae-691f-d1f8-0463f714957d@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-25_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906250087 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Hi Ming, I don't mind doing this change for zfcp. However, I'm having doubts regarding the rationale in the commit description. If I understood your patch series correctly from its cover letter (would have been nice to copy the SCSI MQ detail part of its core statement in (one of) the patches so it would make its way into git log), you plan to make a change to scatterlist allocations *in SCSI MQ*. All zfcp changes in this patch set only refer to zfcp-internal remote port discovery, i.e. they neither come from SCSI (internally) nor from block(mq). zfcp_fc.h: /** * struct zfcp_fc_req - Container for FC ELS and CT requests sent from zfcp * @ct_els: data required for issuing fsf command * @sg_req: scatterlist entry for request data, refers to embedded @u submember * @sg_rsp: scatterlist entry for response data, refers to embedded @u submember * @u: request and response specific data * @u.gpn_ft: GPN_FT specific data * @u.gpn_ft.sg_rsp2: GPN_FT response, not embedded here, allocated elsewhere * @u.gpn_ft.req: GPN_FT request */ struct zfcp_fc_req { struct zfcp_fsf_ct_els ct_els; struct scatterlist sg_req; struct scatterlist sg_rsp; union { struct { struct scatterlist sg_rsp2[ZFCP_FC_GPN_FT_NUM_BUFS - 1]; struct zfcp_fc_gpn_ft_req req; } gpn_ft; } u; }; So this should be guaranteed to be a linear unchained scatterlist, independently of your SCSI (or block) changes. Note: Only remote port discovery also uses u.gpn_ft.sg_rsp2 instead of just sg_rsp. zfcp_fc_scan_ports(work) zfcp_fc_alloc_sg_env(buf_num) zfcp_fc_sg_setup_table(&fc_req->sg_rsp, buf_num) (In fact it's somewhat intricate, because it actually uses sg_rsp and seems to rely on the fact that the subsequent sg_rsp2[] gives enough contiguous memory to hold buf_num linear scatterlist entries starting with field offset sg_rsp.) The other cases use single element and thus linear unchained scatterlist with sg_rsp (and all cases use sg_req): Finding symbol: sg_init_one Database directory: /home/maier/docs/zfcp/tuxmaker/linux/drivers/s390/scsi/ ------------------------------------------------------------------------------- *** zfcp_dbf.c: zfcp_dbf_san_in_els[601] sg_init_one(&sg, srb->payload.data, length); // above tracing part is unrelated to all of scsi/block/zfcp-internal-ct/els *** zfcp_fc.c: zfcp_fc_ns_gid_pn_request[388] sg_init_one(&fc_req->sg_req, gid_pn_req, sizeof(*gid_pn_req)); zfcp_fc_ns_gid_pn_request[389] sg_init_one(&fc_req->sg_rsp, gid_pn_rsp, sizeof(*gid_pn_rsp)); zfcp_fc_adisc[546] sg_init_one(&fc_req->sg_req, &fc_req->u.adisc.req, zfcp_fc_adisc[548] sg_init_one(&fc_req->sg_rsp, &fc_req->u.adisc.rsp, zfcp_fc_alloc_sg_env[668] sg_init_one(&fc_req->sg_req, &fc_req->u.gpn_ft.req, zfcp_fc_gspn[841] sg_init_one(&fc_req->sg_req, gspn_req, sizeof(*gspn_req)); zfcp_fc_gspn[842] sg_init_one(&fc_req->sg_rsp, gspn_rsp, sizeof(*gspn_rsp)); zfcp_fc_rspn[889] sg_init_one(&fc_req->sg_req, rspn_req, sizeof(*rspn_req)); zfcp_fc_rspn[890] sg_init_one(&fc_req->sg_rsp, rspn_rsp, sizeof(*rspn_rsp)); ------------------------------------------------------------------------------- I/O requests from SCSI (MQ) coming through queuecommand have already been safe for non-linear chained scatterlists in zfcp: zfcp_scsi_queuecommand() zfcp_fsf_fcp_cmnd() zfcp_qdio_sbals_from_sg(qdio, &req->qdio_req, scsi_sglist(scsi_cmnd)) for (; sg; sg = sg_next(sg)) { I/O requests from the block layer coming through BSG should also have already been safe for non-linear chained scatterlists in zfcp: zfcp_fc_exec_bsg_job() zfcp_fc_exec_els_job() zfcp_fsf_send_els() zfcp_fsf_setup_ct_els() zfcp_fsf_setup_ct_els_sbals(req, sg_req, sg_resp) //depending on hardware features, translate sg into HW control blocks if (zfcp_adapter_multi_buffer_active()) zfcp_qdio_sbals_from_sg() //for req&resp, see above return 0 /* use single, unchained SBAL if it can hold the request */ if (zfcp_qdio_sg_one_sbale(sg_req) && zfcp_qdio_sg_one_sbale(sg_resp)) zfcp_fsf_setup_ct_els_unchained() //single element for req&resp return 0 if (!(feat & FSF_FEATURE_ELS_CT_CHAINED_SBALS)) return -EOPNOTSUPP; zfcp_qdio_sbals_from_sg() for req&resp, see above OR zfcp_fc_exec_ct_job() zfcp_fsf_send_ct() zfcp_fsf_setup_ct_els() //see above If I was not mistaken above, the following could be more descriptive parts of a patch/commit description, with hopefully less confusion for anyone having to look at zfcp git history a few weeks/months/years from now: "While not required for this SCSI MQ change regarding scatterlist allocation, change all other scatterlist iterators in zfcp to the safe sg_next() even if not necessary as these changed zfcp-internal scatterlists are linear and unchained. This may avoid confusion about a potential need for conversions in the future." On 6/25/19 3:19 AM, Ming Lei wrote: > On Mon, Jun 24, 2019 at 05:13:24PM +0200, Steffen Maier wrote: >> On 6/18/19 3:37 AM, Ming Lei wrote: >>> Use the scatterlist iterators and remove direct indexing of the >>> scatterlist array. >>> >>> This way allows us to pre-allocate one small scatterlist, which can be >>> chained with one runtime allocated scatterlist if the pre-allocated one >>> isn't enough for the whole request. >>> Acked-by: Benjamin Block >>> Reviewed-by: Christoph Hellwig >>> Reviewed-by: Bart Van Assche >>> Signed-off-by: Ming Lei >>> --- >>> drivers/s390/scsi/zfcp_fc.c | 4 ++-- >>> 1 file changed, 2 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c >>> index 33eddb02ee30..b018b61bd168 100644 >>> --- a/drivers/s390/scsi/zfcp_fc.c >>> +++ b/drivers/s390/scsi/zfcp_fc.c >>> @@ -620,7 +620,7 @@ static void zfcp_fc_sg_free_table(struct scatterlist *sg, int count) >>> { >>> int i; >>> - for (i = 0; i < count; i++, sg++) >>> + for (i = 0; i < count; i++, sg = sg_next(sg)) >>> if (sg) >>> free_page((unsigned long) sg_virt(sg)); >>> else >>> @@ -641,7 +641,7 @@ static int zfcp_fc_sg_setup_table(struct scatterlist *sg, int count) >>> int i; >>> sg_init_table(sg, count); >>> - for (i = 0; i < count; i++, sg++) { >>> + for (i = 0; i < count; i++, sg = sg_next(sg)) { >>> addr = (void *) get_zeroed_page(GFP_KERNEL); >>> if (!addr) { >>> zfcp_fc_sg_free_table(sg, i); >>> >> >> I'm still catching up with emails that came during my vacation, so I'm not >> fully up-to-date on the current state of this and how to bring in potential >> fixups on top. >> >> I think, we also have two more (not so obvious) places in the corresponding >> response/completion code path, where we might need to introduce the proper >> iterator helper: >> >> zfcp_fsf.c: >> >> static int zfcp_fc_eval_gpn_ft(struct zfcp_fc_req *fc_req, >> struct zfcp_adapter *adapter, int max_entries) >> { >> struct scatterlist *sg = &fc_req->sg_rsp; >> ... >> /* first entry is the header */ >> for (x = 1; x < max_entries && !last; x++) { >> ... >> if (x % (ZFCP_FC_GPN_FT_ENT_PAGE + 1)) >> ... >> else >> acc = sg_virt(++sg); >> ^^^^ >> >> zfcp_dbf.c: >> >> static u16 zfcp_dbf_san_res_cap_len_if_gpn_ft(char *tag, >> struct zfcp_fsf_req *fsf, >> u16 len) >> { >> struct scatterlist *resp_entry = ct_els->resp; >> ... >> /* the basic CT_IU preamble is the same size as one entry in the GPN_FT >> * response, allowing us to skip special handling for it - just skip it >> */ >> for (x = 1; x < max_entries && !last; x++) { >> if (x % (ZFCP_FC_GPN_FT_ENT_PAGE + 1)) >> ... >> else >> acc = sg_virt(++resp_entry); >> ^^^^^^^^^^^^ >> >> >> What do you think? > > Yeah, looks this one is missed, so we need the following patch: > > From c9c368308fefbf034d670984fe9746a4181fe514 Mon Sep 17 00:00:00 2001 > From: Ming Lei > Date: Tue, 25 Jun 2019 09:15:34 +0800 > Subject: [PATCH] s390: scsi: use sg helper to iterate over scatterlist > > Unlike the legacy I/O path, scsi-mq preallocates a large array to hold > the scatterlist for each request. This static allocation can consume > substantial amounts of memory on modern controllers which support a > large number of concurrently outstanding requests. Very nice, as it disambiguates which scatterlist allocation this patch set is about. > To facilitate a switch to a smaller static allocation combined with a > dynamic allocation for requests that need it, we need to make sure all > SCSI drivers handle chained scatterlists correctly. > > Convert remaining drivers that directly dereference the scatterlist > array to using the iterator functions. > > Cc: Steffen Maier > Cc: Benjamin Block > Cc: Martin Schwidefsky > Cc: Heiko Carstens > Cc: linux-s390@vger.kernel.org > Cc: Benjamin Block Minor: duplicate Cc ? > Signed-off-by: Ming Lei > --- > drivers/s390/scsi/zfcp_dbf.c | 2 +- > drivers/s390/scsi/zfcp_fc.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/s390/scsi/zfcp_dbf.c b/drivers/s390/scsi/zfcp_dbf.c > index dccdb41bed8c..c7129f5234f0 100644 > --- a/drivers/s390/scsi/zfcp_dbf.c > +++ b/drivers/s390/scsi/zfcp_dbf.c > @@ -552,7 +552,7 @@ static u16 zfcp_dbf_san_res_cap_len_if_gpn_ft(char *tag, > if (x % (ZFCP_FC_GPN_FT_ENT_PAGE + 1)) > acc++; > else > - acc = sg_virt(++resp_entry); > + acc = sg_virt(resp_entry = sg_next(resp_entry)); > > last = acc->fp_flags & FC_NS_FID_LAST; > } > diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c > index b018b61bd168..5048812ce660 100644 > --- a/drivers/s390/scsi/zfcp_fc.c > +++ b/drivers/s390/scsi/zfcp_fc.c > @@ -742,7 +742,7 @@ static int zfcp_fc_eval_gpn_ft(struct zfcp_fc_req *fc_req, > if (x % (ZFCP_FC_GPN_FT_ENT_PAGE + 1)) > acc++; > else > - acc = sg_virt(++sg); > + acc = sg_virt(sg = sg_next(sg)); > > last = acc->fp_flags & FC_NS_FID_LAST; > d_id = ntoh24(acc->fp_fid); > Apart from above rationale discussion, the code change looks good. -- Mit freundlichen Gruessen / Kind regards Steffen Maier Linux on IBM Z Development https://www.ibm.com/privacy/us/en/ IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Matthias Hartmann Geschaeftsfuehrung: Dirk Wittkopp Sitz der Gesellschaft: Boeblingen Registergericht: Amtsgericht Stuttgart, HRB 243294