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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 714BDC3DA78 for ; Tue, 17 Jan 2023 11:44:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236715AbjAQLog (ORCPT ); Tue, 17 Jan 2023 06:44:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58240 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236580AbjAQLof (ORCPT ); Tue, 17 Jan 2023 06:44:35 -0500 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2FBD29012; Tue, 17 Jan 2023 03:44:34 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id BD4E23453B; Tue, 17 Jan 2023 11:44:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1673955872; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5ole6isE4RExd/uxxeZuPvFlLXIRWIIDWEltEeqOodo=; b=oXCvkkZH8Qh6p/q9dIUf+LvjViezQNXRxe3SQ97YDxKHQJXYUL74TYrqbGkKfZNFm21ihH FQa18NyRudcGHd4tvB7LS+GaSFPfUUwESBQGY0ExF5eRxy3B8T9fkdDz6rbtNthV1We++Z R3btKdeyFOnTkK23A6JdjintVSJpNPw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1673955872; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5ole6isE4RExd/uxxeZuPvFlLXIRWIIDWEltEeqOodo=; b=Flz8OS1zLtVdgcyg24JF30m5Ftf75Ep+rCQyrEdIFB8hMYvjwzN8bKPswfntZ1/Sz+mcbk rAIoXimX7GBnlcCA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id AC04A13357; Tue, 17 Jan 2023 11:44:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id ksW2KSCKxmMnSAAAMHmgww (envelope-from ); Tue, 17 Jan 2023 11:44:32 +0000 Message-ID: Date: Tue, 17 Jan 2023 12:44:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH v2 03/18] scsi: core: allow libata to complete successful commands via EH To: Niklas Cassel Cc: "James E.J. Bottomley" , "Martin K. Petersen" , Damien Le Moal , "linux-scsi@vger.kernel.org" , "linux-ide@vger.kernel.org" , "linux-block@vger.kernel.org" References: <20230112140412.667308-1-niklas.cassel@wdc.com> <20230112140412.667308-4-niklas.cassel@wdc.com> Content-Language: en-US From: Hannes Reinecke In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 1/16/23 13:43, Niklas Cassel wrote: > On Fri, Jan 13, 2023 at 08:57:37AM +0100, Hannes Reinecke wrote: >> On 1/12/23 15:03, Niklas Cassel wrote: >>> In SCSI, we get the sense data as part of the completion, for ATA >>> however, we need to fetch the sense data as an extra step. For an >>> aborted ATA command the sense data is fetched via libata's >>> ->eh_strategy_handler(). >>> >>> For Command Duration Limits policy 0xD: >>> The device shall complete the command without error with the additional >>> sense code set to DATA CURRENTLY UNAVAILABLE. >>> >>> In order to handle this policy in libata, we intend to send a successful >>> command via SCSI EH, and let libata's ->eh_strategy_handler() fetch the >>> sense data for the good command. This is similar to how we handle an >>> aborted ATA command, just that we need to read the Successful NCQ >>> Commands log instead of the NCQ Command Error log. >>> >>> When we get a SATA completion with successful commands, ATA_SENSE will >>> be set, indicating that some commands in the completion have sense data. >>> >>> The sense_valid bitmask in the Sense Data for Successful NCQ Commands >>> log will inform exactly which commands that had sense data, which might >>> be a subset of all the commands that was completed in the same >>> completion. (Yet all will have ATA_SENSE set, since the status is per >>> completion.) >>> >>> The successful commands that have e.g. a "DATA CURRENTLY UNAVAILABLE" >>> sense data will have a SCSI ML byte set, so scsi_eh_flush_done_q() will >>> not set the scmd->result to DID_TIME_OUT for these commands. However, >>> the successful commands that did not have sense data, must not get their >>> result marked as DID_TIME_OUT by SCSI EH. >>> >>> Add a new flag SCMD_EH_SUCCESS_CMD, which tells SCSI EH to not mark a >>> command as DID_TIME_OUT, even if it has scmd->result == SAM_STAT_GOOD. >>> >>> This will be used by libata in a follow-up patch. >>> >>> Signed-off-by: Niklas Cassel >>> --- >>> drivers/scsi/scsi_error.c | 3 ++- >>> include/scsi/scsi_cmnd.h | 5 +++++ >>> 2 files changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c >>> index 2aa2c2aee6e7..51aa5c1e31b5 100644 >>> --- a/drivers/scsi/scsi_error.c >>> +++ b/drivers/scsi/scsi_error.c >>> @@ -2165,7 +2165,8 @@ void scsi_eh_flush_done_q(struct list_head *done_q) >>> * scsi_eh_get_sense), scmd->result is already >>> * set, do not set DID_TIME_OUT. >>> */ >>> - if (!scmd->result) >>> + if (!scmd->result && >>> + !(scmd->flags & SCMD_EH_SUCCESS_CMD)) >>> scmd->result |= (DID_TIME_OUT << 16); >>> SCSI_LOG_ERROR_RECOVERY(3, >>> scmd_printk(KERN_INFO, scmd, >> Wouldn't it be better to use '!scmd->result && !scsi_sense_valid(scmd)' >> instead of a new flag? >> After all, if we have a valid sense code we _have_ been able to communicate >> with the device. And as we did so it's questionable whether it should count >> as a command time out ... > > Hello Hannes, > > Thanks a lot for helping out reviewing this series! > > Unfortunately, your suggestion won't work. > > > Let me explain: > > When you get a FIS, the ACT register will have a bit set for each > command that finished, however, all the commands will share a single > STATUS value (since there is just a shared STATUS field in the FIS). > > So let's say that tags 0-3 got finished (i.e. bits 0-3 are set in the > ACT field) and the STATUS field has the "Sense Data Available" bit set. > > This just tells us that at least one of tags 0-3 has sense data. > > > In order to know which of these tags that actually has sense data, > we need to read the "Sense Data for Successful NCQ Commands log", > which contains a sense_valid bitmask (which contains one bit for > each of the 32 tags). > > So reading the "Sense Data for Successful NCQ Commands log" might > tell us that just tag 0-1 have sense data. > > So, libata calls ata_qc_schedule_eh() on tags 0-3, wait until SCSI calls > libata .eh_strategy_handler(). libata .eh_strategy_handler() will read the > "Sense Data for Successful NCQ Commands log", which will see that there is > sense data for tags 0-1, and will add sense data for those commands, and > call scsi_check_sense() for tags 0-1. > > ata_eh_finish() will finally be called, to determine what to do with the > commands that belonged to EH. > > The code looks like this: > if (qc->flags & ATA_QCFLAG_SENSE_VALID || > qc->flags & ATA_QCFLAG_EH_SUCCESS_CMD) { > ata_eh_qc_complete(qc); > } > > So it will call complete for all 4 tags, regardless is they had sense data > or not. > > > scsi_eh_flush_done_q() will soon be called, and since ata_eh_qc_complete() > sets scmd->retries == scmd->allowed, none of the four commands will be retired. > > if (!scmd->result && > !(scmd->flags & SCMD_EH_SUCCESS_CMD)) > scmd->result |= (DID_TIME_OUT << 16); > > The 2 commands with sense data will not get DID_TIMEOUT, > because scmd->result has the SCSI ML byte set > (which is set by scsi_check_sense()). > > The 2 commands without sense data will have scmd->result == 0, > so they will get DID_TIME_OUT set if we don't have the extra > !(scmd->flags & SCMD_EH_SUCCESS_CMD)) condition. > > > SCSI could add an additional check for: > > if (!scmd->result && !scsi_sense_valid(scmd) && > !(scmd->flags & SCMD_EH_SUCCESS_CMD)) > scmd->result |= (DID_TIME_OUT << 16); > > so that a command with does have sense data, but scsi_check_sense() > did not set any SCSI ML byte, does not get DID_TIME_OUT set. > > However, for CDL policy 0xD, which this patch cares about, > we would still need the "&& !(scmd->flags & SCMD_EH_SUCCESS_CMD))", > so at least from a CDL perspective, I don't see how any benefit of > also adding a check for "&& !scsi_sense_valid(scmd)". > Right, I see. Thanks for the explanation. You can add: Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer