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  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Wed, 03 Apr 2013 19:09:33 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Jan Kara <jack@...e.cz>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	Jan Kara <jack@...e.cz>
Subject: Re: per inode fsync optimization question

On Wed, 3 Apr 2013 16:50:55 +0200, Jan Kara <jack@...e.cz> wrote:
> On Wed 03-04-13 18:21:46, Dmitry Monakhov wrote:
> > inode store i_sync_tid and i_datasync_tid  in order to optimize journal
> > flushes and wait for commits only when necessary, but
> > fields are declared as tid_t(not atomic_t as it done in ext3) so we
> > have not synchronization between readers and writers, so gcc and cpu
> > is allowed to perform prefetch, cache and other stuff.
> > Looks like a bug, right?
>   Reads and writes to atomic_t aren't guaranteed to be any kind of a
> barrier (if fact they are compiled as simple stores and loads on x86). Only
> arithmetic operations on atomic types are special. So using tid_t is just
> fine.
Ok but what about prefetching?
Compiler is allowed to prefetch on early stage ?
should we use ACCESS_ONCE() or wmb() and rmb() here?


> 
> 								Honza
> -- 
> Jan Kara <jack@...e.cz>
> SUSE Labs, CR
--
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

Powered by blists - more mailing lists