linux-kernel - Re: [GIT PULL] fuse update for 3.19

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Message-ID: <CAB9dFdty+3JXgJqhMNNHuDXivx9_paK2=zd7Vb_D4-suU6OGBg@mail.gmail.com>
Date:	Wed, 24 Dec 2014 12:53:13 -0400
From:	Marc Dionne <marc.c.dionne@...il.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [GIT PULL] fuse update for 3.19

On Wed, Dec 17, 2014 at 6:02 AM, Miklos Szeredi <miklos@...redi.hu> wrote:
> Hi Linus,
>
> Please pull from:
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse.git for-linus
>
> First part makes sure we don't hold up umount with pending async requests.  In
> addition to being a cleanup, this is a small behavioral change (for the better)
> and unlikely to break anything.  Second part prepares for a cleanup of the fuse
> device I/O code by adding a helper for simple request submission, with some
> savings in line numbers already realized.
>
> Thanks,
> Miklos
>
> ---
> Miklos Szeredi (6):
>       fuse: don't wake up reserved req in fuse_conn_kill()
>       fuse: flush requests on umount
>       fuse: hold inode instead of path after release
>       fuse: reduce max out args
>       fuse: introduce fuse_simple_request() helper
>       fuse: use file_inode() in fuse_file_fallocate()
>

Hi Miklos,

Commit 7078187a795f ("fuse: introduce fuse_simple_request() helper")
from the above pull request triggers some EIO errors for me in some
tests that rely on fuse.

Looking at the code changes and a bit of debugging info I think
there's a general problem here that fuse_get_req checks and possibly
waits for fc->initialized, and this was always called first.  But this
commit changes the ordering and in many places fc->minor is now
possibly used before fuse_get_req, and we can't be sure that fc has
been initialized.  In my case fuse_lookup_init sets
req->out.args[0].size to the wrong size because fc->minor at that
point is still 0, leading to the EIO error.

Assuming the analysis makes sense, it wasn't obvious what the best fix
should be.

Thanks,
Marc
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