From: Ted Ts'o <tytso@mit.edu>
To: Jan Kara <jack@suse.cz>
Cc: Andy Lutomirski <luto@amacapital.net>,
Andreas Dilger <adilger@dilger.ca>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH] mm: Improve cmtime update on shared writable mmaps
Date: Wed, 2 Nov 2011 11:19:03 -0400 [thread overview]
Message-ID: <20111102151903.GA15045@thunk.org> (raw)
In-Reply-To: <20111102150200.GC31575@quack.suse.cz>
On Wed, Nov 02, 2011 at 04:02:00PM +0100, Jan Kara wrote:
> That's a good question. Locking of i_flags was always kind of unclear to
> me. They are certainly read without any locks and in the couple of places
> where setting can actually race VFS uses i_mutex for serialization which is
> kind of overkill (and unusable from page fault due to locking constraints).
> Probably using atomic bitops for setting i_flags would be needed.
Adding a set of inode_{test,set,clear}_flag() inline functions, and
then converting accesses of i_flags to use them would be a great
cleanup task. It's been on my mental todo list for a while, but it's
a pretty invasive change. What we have right now is definitely racy,
though, and we only get away with it because i_flags changes happen
relatively rarely. Fixing this would be definitely be a Good Thing.
- Ted
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prev parent reply other threads:[~2011-11-02 15:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CALCETrWoZeFpznU5Nv=+PvL9QRkTnS4atiGXx0jqZP_E3TJPqw@mail.gmail.com>
2011-10-28 23:39 ` [PATCH] mm: Improve cmtime update on shared writable mmaps Andy Lutomirski
2011-11-01 22:53 ` Jan Kara
2011-11-01 23:02 ` Andy Lutomirski
2011-11-02 7:38 ` Christoph Hellwig
2011-11-02 15:02 ` Jan Kara
2011-11-02 15:19 ` Ted Ts'o [this message]
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