linux-kernel - Re: fsnotify_mark

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Message-ID: <CAOQ4uxjXiOddZt19Y60YOiCj-uDC2pA77mtzTYC_htwsmNuL-A@mail.gmail.com>
Date:   Mon, 14 Nov 2016 13:59:44 +0200
From:   Amir Goldstein <amir73il@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Miklos Szeredi <miklos@...redi.hu>, Eric Paris <eparis@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: fsnotify_mark_srcu wtf?

On Sun, Nov 13, 2016 at 8:43 PM, Amir Goldstein <amir73il@...il.com> wrote:
> On Thu, Nov 10, 2016 at 9:46 PM, Jan Kara <jack@...e.cz> wrote:
>
> ...
>
>>
>> Well but how would you like to protect the mark list hanging off the inode
>> / mountpoint with two SRCUs? You'd need two lists hanging off the inode &
>> mountpoint (for different priorities) and that's too big cost to pay to
>> accomodate broken userspace...
>>
>
> This is the plan.
> I have a rough implementation, which still requires some testing:
>

2 patches posted:
 fsnotify: separate fsnotify_mark_srcu for groups with permission events
 fsnotify: handle permission events without holding fsnotify_mark_srcu[0]

Miklos,

Your test program actually passes after the first patch (split to 2 SRCU)
but only because it does not add any inotify mark, so I modified your test
a bit and made it available on my github:
https://github.com/amir73il/fsnotify-utils/blob/master/fanotify_bug.c

Jan,

Please let me know what you think of this version.

Thanks,
Amir.