linux-kernel - Re: linux-next: Tree for Jun 26 [ vfs | block

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Message-ID: <CA+icZUXVuTHH2s2-dbTwUTLwdPiuqr8LKzeGQWwfaJQebFj=Dw@mail.gmail.com>
Date:	Wed, 26 Jun 2013 19:47:24 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Al Viro <viro@...iv.linux.org.uk>,
	Jens Axboe <axboe@...nel.dk>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Miklos Szeredi <miklos@...redi.hu>,
	fuse-devel@...ts.sourceforge.net,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: linux-next: Tree for Jun 26 [ vfs | block | fuse (cpuidle)
 releated? ]

On Wed, Jun 26, 2013 at 7:15 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Wed, Jun 26, 2013 at 05:36:03PM +0200, Sedat Dilek wrote:
>> On Wed, Jun 26, 2013 at 5:32 PM, Greg Kroah-Hartman
>> <gregkh@...uxfoundation.org> wrote:
>> > On Wed, Jun 26, 2013 at 05:24:46PM +0200, Thomas Petazzoni wrote:
>> >> Dear Sedat Dilek,
>> >>
>> >> On Wed, 26 Jun 2013 16:50:55 +0200, Sedat Dilek wrote:
>> >>
>> >> > [ TO/CC char-misc folks ]
>> >> >
>> >> > The CULPRIT commit [1] due to my git-bisecting is:
>> >> >
>> >> > commit 585d98e00ba7a5e2abe65f7a1eff631cb612289b
>> >> > "char: misc: assign file->private_data in all cases"
>> >> >
>> >> > After reverting it, my system boots up fine again.
>> >> >
>> >> > Can someone from the char-misc folks look at that?
>> >>
>> >> Ok. My understanding is that the misc device registered by
>> >> fs/fuse/dev.c:fuse_dev_init() makes the assumption that
>> >> file->private_data == NULL when a misc device is opened. But I'm not
>> >> sure to fully understand the code flow of the FUSE filesystem.
>> >>
>> >> And since it doesn't provide its own implementation of the ->open()
>> >> operation, the misc infrastructure was leaving the file->private_data
>> >> defined to NULL before my patch.
>> >>
>> >> With my patch, the file->private_data gets assigned unconditionally
>> >> (regardless of whether the misc driver provides or does not provide a
>> >> ->open() operation) which modifies the unwritten assumption that fuse
>> >> was making about the initial value of file->private_data. I believe the
>> >> assumption made by fuse over the initial value of this variable is a
>> >> bit fragile.
>> >>
>> >> Maybe the FUSE code needs to be slightly adjusted to not make this
>> >> assumption?
>> >
>> > As the FUSE code was working properly before this change, I think this
>> > misc core change needs to be reverted, so I'll go do that in a bit.
>> >
>>
>> Good, sound reasonable.
>>
>> I was not aware that char-misc and fuse code is so interwoven (hope
>> this is the right word).
>
> The fuse driver is a misc device, so the fuse code depends on the misc
> core to work properly, that's the dependancy here.
>
> I've now reverted this change, thanks again for the report and the quick
> determination of the problem.
>

All this early-testing results sometimes in nice use-cases/test-cases.

If I think of the IPC-MSG issue (fakeroot & 'make deb-pkg') I had in -next...
I have sent a patch to Linux-Testing-Project to enhance the IPC test-suite.
As a goodie I catched a BASHISM bug for dash shell in runltp script :-).

I forgot a bug-report for Debian's fakeroot... The shipped DEBUG
doc-file is outdated.

The harder part is to convince the maintainers that sth. is/went wrong :-).

Personally, I am happy when Friday's Linux-Next is "bug-free" for me.

- Sedat -

> greg k-h
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