linux-ext4 - Re: [PATCH] mm: Improve cmtime update on shared writable mmaps

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 2 Nov 2011 11:19:03 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Andreas Dilger <adilger@...ger.ca>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] mm: Improve cmtime update on shared writable mmaps

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
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html