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=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 2B0E7C433E2 for ; Sun, 6 Sep 2020 01:19:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDCCB2078D for ; Sun, 6 Sep 2020 01:19:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="hHiOERmV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728825AbgIFBTl (ORCPT ); Sat, 5 Sep 2020 21:19:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41260 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728409AbgIFBTj (ORCPT ); Sat, 5 Sep 2020 21:19:39 -0400 Received: from mail-ej1-x642.google.com (mail-ej1-x642.google.com [IPv6:2a00:1450:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3021DC061244 for ; Sat, 5 Sep 2020 18:19:39 -0700 (PDT) Received: by mail-ej1-x642.google.com with SMTP id i22so13340741eja.5 for ; Sat, 05 Sep 2020 18:19:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=DtiH2plxGMa00nhpoF0XIe4LVvDVaWVAkHrDWRd75Lw=; b=hHiOERmVBhszFZmGEn6AQ79DiFMNlCpYN52Gt2ufE9zxvRxhJmCo5lyYOaukAikCu/ OXoIelfyVNbKBOYcljh8D5x28eXN4QzmgPMf3MjJJf9SILfVl9cjTZLr3CjEdSiWzPxC rkFcRs9XBpyfZgDsuHNYTfj55alNdyLFM/XEJ3ILNEOGX3QgoBea7rArSwkFT+iFjoP1 C8KsAFQyJ3BOwRFFA76evDKTw1Z9z9PP6PwJRy/AbUInwu1ZodysPzOFKiIya3TADv3Z Vc+HMU8dVzLP+lezVX311YR3TxP76U8SjMP1AFhiGzeX+SJ6jjVZkNXRwhYeciOZ+IN2 aKBw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=DtiH2plxGMa00nhpoF0XIe4LVvDVaWVAkHrDWRd75Lw=; b=hOPgw+LIAw1U2LzxFscA0WmRWlyn0KLjPq4fKVZdkJPN++/PB+f/VXF3R/UdUAS23f 0acudMehvdu69wqy7Qt10Sfe/tAaVhd7dxGduzhepkO4TBw/fgfHhohzDBx2lL2Im5V0 KqHUZqe+WeTD0NDUIXFpFIuumBXiLeTcIzR4aezrI9Bl/cMTBik3Viq+xT+C0qqtqibL ZsHpBsYY2/SR45y2c+4I4TlVuhAai8hMl4f3HL81RlHLwQ8kDZpUYcn6lfUEqASMNNHT b92bIHukeA+Kk7zkerWhik/9BWm9UhvSww6O+yU4nPfRyMrANdeO11uOMdGJBNyjv0lw CCQw== X-Gm-Message-State: AOAM5300HVhOkvVmX0jCG7BABd3NNtTSA2WWSyVWHR8G0W1bOc9+GLKX k/TIqYS9AWK4w1+BfIyB1XfFIemkkuM/Pzcst2zleAtt X-Google-Smtp-Source: ABdhPJz7PQ4KOnDaLU2yed25XJsRKW34oM+WppPawFmikfUx/3OzWc2DEqNm/oKeQCR47O0/O1M8uj/1TTP+RjyeCEU= X-Received: by 2002:a17:906:2a17:: with SMTP id j23mr3878435eje.146.1599355177495; Sat, 05 Sep 2020 18:19:37 -0700 (PDT) MIME-Version: 1.0 References: <20200904200554.168979-1-tom.ty89@gmail.com> <868195a0-94f2-f009-bfd4-f206f0da7db8@interlog.com> In-Reply-To: <868195a0-94f2-f009-bfd4-f206f0da7db8@interlog.com> From: Tom Yan Date: Sun, 6 Sep 2020 09:19:26 +0800 Message-ID: Subject: Re: [PATCH 1/4] scsi: sg: fix BLKSECTGET ioctl To: dgilbert@interlog.com Cc: Bart Van Assche , linux-scsi@vger.kernel.org, Alan Stern , akinobu.mita@gmail.com, hch@lst.de Content-Type: text/plain; charset="UTF-8" Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org It was my concern as well, that for this sort of "backwards-incompatible reason", it has been kept broken intentionally. I am not sure if queue_max_sectors() or BLKSECTGET has ever been implemented in the block layer to give out the limit in bytes, but it certainly isn't the case anymore. I am not in position to say whether it's "right" or "wrong" to implement BLKSECTGET/BLKSSZGET in the sg driver, but they is definitely useful in some cases (as long as the queue_* functions work for the given underlying device). Is it not okay if they don't ultimately work on *some* devices, even when they aren't named SG_*? Perhaps we can consider having them removed as well (and implement them as e.g. SG_GET_MAX_SECTORS and SG_GET_LBS; but IMHO that only makes a point if they can be made to work on more than block devices). On Sun, 6 Sep 2020 at 04:37, Douglas Gilbert wrote: > > On 2020-09-05 3:32 p.m., Bart Van Assche wrote: > > On 2020-09-04 13:05, Tom Yan wrote: > >> It should give out the maximum number of sectors per request > >> instead of maximum number of bytes. > >> > >> Signed-off-by: Tom Yan > >> --- > >> drivers/scsi/sg.c | 6 ++++-- > >> 1 file changed, 4 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > >> index 20472aaaf630..e57831910228 100644 > >> --- a/drivers/scsi/sg.c > >> +++ b/drivers/scsi/sg.c > >> @@ -922,6 +922,7 @@ sg_ioctl_common(struct file *filp, Sg_device *sdp, Sg_fd *sfp, > >> int result, val, read_only; > >> Sg_request *srp; > >> unsigned long iflags; > >> + unsigned int max_sectors; > >> > >> SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp, > >> "sg_ioctl: cmd=0x%x\n", (int) cmd_in)); > >> @@ -1114,8 +1115,9 @@ sg_ioctl_common(struct file *filp, Sg_device *sdp, Sg_fd *sfp, > >> sdp->sgdebug = (char) val; > >> return 0; > >> case BLKSECTGET: > >> - return put_user(max_sectors_bytes(sdp->device->request_queue), > >> - ip); > >> + max_sectors = min_t(unsigned int, USHRT_MAX, > >> + queue_max_sectors(sdp->device->request_queue)); > >> + return put_user(max_sectors, ip); > >> case BLKTRACESETUP: > >> return blk_trace_setup(sdp->device->request_queue, > >> sdp->disk->disk_name, > > > > Is this perhaps a backwards-incompatible change to the kernel ABI, the > > kind of change Linus totally disagrees with? > > > > Additionally, please Cc linux-api for patches that modify the kernel ABI. > >>From https://www.kernel.org/doc/man-pages/linux-api-ml.html: "The kernel > > source file Documentation/SubmitChecklist notes that all Linux kernel > > patches that change userspace interfaces should be CCed to > > linux-api@vger.kernel.org, so that the various parties who are interested > > in API changes are informed. For further information, see > > https://www.kernel.org/doc/man-pages/linux-api-ml.html" > > Hmm, > The BLK* ioctl()s in the sg driver were an undocumented addition by others. > Plus it is not clear to me why a char device such as the sg driver should > be supporting BLK* ioctl(2)s. For example, how should an enclosure react to > those ioctls or a WLUN? > > If they are going to be supported for storage devices and /dev/sdb and > /dev/sg2 are the same device then if: > blockdev --getmaxsect /dev/sg1 > > gives a different result to: > blockdev --getmaxsect /dev/sdb > > then I would consider that a bug. So fixing it is making the kernel ABI > more consistent :-) That's exactly my point. They should work identically as the ones implemented in the block layer, because of their names. With that said, sg_version needs to be bumped once the fix gets in, so that there's a way to differentiate the "different implementations" in userspace. > > Doug Gilbert > > > Regards, Tom