From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: [PATCH v1] scsi: Don't select SCSI_PROC_FS by default Date: Wed, 19 Jun 2019 10:34:42 -0400 Message-ID: <48912bc0-8c79-408d-7ed2-c127b99b8bcc@interlog.com> References: <2de15293-b9be-4d41-bc67-a69417f27f7a@free.fr> <621306ee-7ab6-9cd2-e934-94b3d6d731fc@acm.org> <017cf3cf-ecd8-19c2-3bbd-7e7c28042c3c@free.fr> Reply-To: dgilbert@interlog.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-CA Sender: linux-kernel-owner@vger.kernel.org To: Marc Gonzalez Cc: Finn Thain , Bart Van Assche , James Bottomley , Martin Petersen , SCSI , LKML , Christoph Hellwig List-Id: linux-scsi@vger.kernel.org On 2019-06-19 5:42 a.m., Marc Gonzalez wrote: > On 18/06/2019 17:31, Douglas Gilbert wrote: > >> On 2019-06-18 3:29 a.m., Marc Gonzalez wrote: >> >>> Please note that I am _in no way_ suggesting that we remove any code. >>> >>> I just think it might be time to stop forcing CONFIG_SCSI_PROC_FS into >>> every config, and instead require one to explicitly request the aging >>> feature (which makes CONFIG_SCSI_PROC_FS show up in a defconfig). >>> >>> Maybe we could add CONFIG_SCSI_PROC_FS to arch/x86/configs/foo ? >>> (For which foo? In a separate patch or squashed with this one?) >> >> Since current sg driver usage seems to depend more on SCSI_PROC_FS >> being "y" than other parts of the SCSI subsystem then if >> SCSI_PROC_FS is to default to "n" in the future then a new >> CONFIG_SG_PROC_FS variable could be added. >> >> If CONFIG_CHR_DEV_SG is "*" or "m" then default CONFIG_SG_PROC_FS >> to "y"; if CONFIG_SCSI_PROC_FS is "y" then default CONFIG_SG_PROC_FS >> to "y"; else default CONFIG_SG_PROC_FS to "n". Obviously the >> sg driver would need to be changed to use CONFIG_SG_PROC_FS instead >> of CONFIG_SCSI_PROC_FS . > > I like your idea, and I think it might even be made slightly simpler. > > I assume sg3_utils requires CHR_DEV_SG. Is it the case? > > If so, we would just need to enable SCSI_PROC_FS when CHR_DEV_SG is enabled. > > diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig > index 73bce9b6d037..642ca0e7d363 100644 > --- a/drivers/scsi/Kconfig > +++ b/drivers/scsi/Kconfig > @@ -54,14 +54,12 @@ config SCSI_NETLINK > config SCSI_PROC_FS > bool "legacy /proc/scsi/ support" > depends on SCSI && PROC_FS > - default y > + default CHR_DEV_SG > ---help--- > This option enables support for the various files in > /proc/scsi. In Linux 2.6 this has been superseded by > files in sysfs but many legacy applications rely on this. > > - If unsure say Y. > - > comment "SCSI support type (disk, tape, CD-ROM)" > depends on SCSI > > > Would that work for you? > I checked that SCSI_PROC_FS=y whether CHR_DEV_SG=y or m > I can spin a v2, with a blurb about how sg3_utils relies on SCSI_PROC_FS. Yes, but (see below) ... >> Does that defeat the whole purpose of your proposal or could it be >> seen as a partial step in that direction? What is the motivation >> for this proposal? > > The rationale was just to look for "special-purpose" options that are > enabled by default, and change the default wherever possible, as a > matter of uniformity. > >> BTW We still have the non-sg related 'cat /proc/scsi/scsi' usage >> and 'cat /proc/scsi/device_info'. And I believe the latter one is >> writable even though its permissions say otherwise. > > Any relation between SG and BSG? Only in the sense that writing to /proc/scsi/device_info changes the way the SCSI mid-level handles the identified device. So that is in common with, and hence the same relation as, sd, sr, st, ses, etc have with the identified device (e.g. a specialized USB dongle). Example of use of /proc/scsi/scsi $ cat /proc/scsi/scsi Attached devices: Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: Linux Model: scsi_debug Rev: 0188 Type: Direct-Access ANSI SCSI revision: 07 Host: scsi0 Channel: 00 Id: 00 Lun: 01 Vendor: Linux Model: scsi_debug Rev: 0188 Type: Direct-Access ANSI SCSI revision: 07 Host: scsi0 Channel: 00 Id: 00 Lun: 02 Vendor: Linux Model: scsi_debug Rev: 0188 Type: Direct-Access ANSI SCSI revision: 07 Which can be replaced by: $ lsscsi [0:0:0:0] disk Linux scsi_debug 0188 /dev/sda [0:0:0:1] disk Linux scsi_debug 0188 /dev/sdb [0:0:0:2] disk Linux scsi_debug 0188 /dev/sdc [N:0:1:1] disk INTEL SSDPEKKF256G7L__1 /dev/nvme0n1 Or if one really likes the "classic" look: $ lsscsi -c Attached devices: Host: scsi0 Channel: 00 Target: 00 Lun: 00 Vendor: Linux Model: scsi_debug Rev: 0188 Type: Direct-Access ANSI SCSI revision: 07 Host: scsi0 Channel: 00 Target: 00 Lun: 01 Vendor: Linux Model: scsi_debug Rev: 0188 Type: Direct-Access ANSI SCSI revision: 07 Host: scsi0 Channel: 00 Target: 00 Lun: 02 Vendor: Linux Model: scsi_debug Rev: 0188 Type: Direct-Access ANSI SCSI revision: 07 Now looking at /proc/scsi/device_info IMO unless there is a replacement for /proc/scsi/device_info then your patch should not go ahead . If it does, any reasonable distro should override it. $ cat /proc/scsi/device_info 'Aashima' 'IMAGERY 2400SP' 0x1 'CHINON' 'CD-ROM CDS-431' 0x1 'CHINON' 'CD-ROM CDS-535' 0x1 'DENON' 'DRD-25X' 0x1 ... 'XYRATEX' 'RS' 0x240 'Zzyzx' 'RocketStor 500S' 0x40 'Zzyzx' 'RocketStor 2000' 0x40 That is a black (or quirks) list that can be added to by writing an entry to /proc/scsi/device_info . So if a user has a device that needs one of those quirks defined to stop their system locking up when a device of that type is plugged in, and the distro or some app (say, that needs that device) knows about that, then it would be sad if /proc/scsi/device_info was missing due to the changed default that is being proposed. The word "legacy" *** is thrown around a bit too often. It is not legacy if there is no replacement for that functionality. Doug Gilbert *** I'm assuming "aging feature" is a softer form of "legacy feature". "Classic" may be going too far the other way from "aged" and "legacy".