linux-kernel - Re: [PATCH 0/3] SG_IO command filtering via sysfs

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Date:   Fri, 16 Nov 2018 12:35:51 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Bart Van Assche <bvanassche@....org>, linux-kernel@...r.kernel.org,
        linux-scsi@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 0/3] SG_IO command filtering via sysfs

On Fri, Nov 16, 2018 at 08:01:29AM +0100, Paolo Bonzini wrote:
> On 16/11/18 01:37, Bart Van Assche wrote:
> > All user space interfaces in the Linux kernel for storage that I'm familiar
> > with not only allow configuration of parameters but also make it easy to
> > query which parameters have been configured. The existing sysfs and configfs
> > interfaces demonstrate this. Using BPF to configure SG/IO access has a
> > significant disadvantage, namely that it is very hard to figure out what has
> > been configured. Figuring out what has been configured namely requires
> > disassembling BPF. I'm not sure anyone will be enthusiast about this.
> 
> Well, that's a problem with BPF in general.  With great power comes
> great obscurability.

You can also make the same complaint about kernel modules; that it's
impossible to figure exactly what a kernel modules does without
disassembling them.  However, you can a one-line description of what
it does using modinfo:

% modinfo async_pq
filename:       /lib/modules/4.19.0-00022-g831156939ae8/kernel/crypto/async_tx/async_pq.ko
license:        GPL
description:    asynchronous raid6 syndrome generation/validation
srcversion:     529102C736C4FED181C15A8
depends:        raid6_pq,async_tx,async_xor
retpoline:      Y
intree:         Y
name:           async_pq
vermagic:       4.19.0-00022-g831156939ae8 SMP mod_unload modversions 

					       - Ted