Re: [RFC] fs: add userspace critical mounts event support

From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	"Herbert, Marc" <marc.herbert@intel.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Jacek Anaszewski <j.anaszewski@samsung.com>,
	David Woodhouse <dwmw2@infradead.org>,
	Christian Lamparter <chunkeey@googlemail.com>,
	Julia Lawall <Julia.Lawall@lip6.fr>,
	Andrew Morton <akpm@linux-foundation.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
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	Andy Lutomirski <luto@amacapital.net>,
	Richard Purdie <rpurdie@rpsys.net>,
	Wu Fengguang <fengguang.wu@intel.com>,
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	Michal Marek <mmarek@suse.com>, Hauke Mehrtens <hauke@hauke-m.de>,
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	Felix Fietkau <nbd@nbd.name>, Roman Pen <r.peniaev@gmail.com>,
	Greg KH <gregkh@linuxfoundation.org>,
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	Takashi Iwai <tiwai@suse.de>, Jeff Mahoney <jeffm@suse.com>,
	Hariprasad S <hariprasad@chelsio.com>,
	Benjamin Poirier <bpoirier@suse.de>,
	Josh Triplett <josh@joshtriplett.org>
Subject: Re: [RFC] fs: add userspace critical mounts event support
Date: Tue, 4 Oct 2016 17:24:14 -0700	[thread overview]
Message-ID: <CAB=NE6UXX+=nnJcOgO7NWudmDR3bESVO-mQrqG26Gpd4z71xqA@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFx=hzXhrHQO4-0Jnd1ML4dismQ8qggvSp0yccSRW6qH3A@mail.gmail.com>

On Tue, Oct 4, 2016 at 5:12 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Tue, Oct 4, 2016 at 5:00 PM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
>>
>> I am not sure how/why a firmware loading daemon would be a better
>> idea now. What Marc describes that Josh proposed with signals for
>> userspcae seems more aligned with what we likely need
>
> Quite frankly, I doubt you want a signal.
>
> You will want to have some way to specify where the firmware files
> are. Right now we have "fw_path[]" which is hardcoded except for the
> first entry that can be set as a module parameter. But you'd probably
> want to expand on that, which implies some /sys or /proc interface.
>
> And once you do that, wouldn't it make more sense to just make the
> "update the firmware path /proc/sys/kernel/fw_path file" make things
> re-search for firmware?

We can, but re-searching for firmware assumes we cache pending
firmware, we currently don't, we just either process sync or async
firmware requests.

> In other words, the interface has to be something *sensible*. Not some
> idiotic ad-hoc "send a signal" (of which that stupid original patch
> was just a very odd example).

Note that the races are beyond firmware, so all
kernel_read_file_from_path() users, as such re-using such old /sys/
interafeces for firmware will not suffice to cover all ground now for
the same race for other possible users.

 Luis