From: Joel Becker <jlbec@evilplan.org>
To: Allison Henderson <achender@linux.vnet.ibm.com>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>,
Ted Ts'o <tytso@mit.edu>
Subject: Re: i_mutex questions
Date: Tue, 13 Sep 2011 12:02:09 -0700 [thread overview]
Message-ID: <20110913190208.GD4635@noexit.corp.google.com> (raw)
In-Reply-To: <4E6FA1F9.6080802@linux.vnet.ibm.com>
On Tue, Sep 13, 2011 at 11:33:29AM -0700, Allison Henderson wrote:
> Hi All,
>
> I have been trying to find a way to synchronize punch hole with read
> and write operations with out the use of i_mutex. The concern is
> that after punch hole has released the pages inside the hole,
> another process may remap the page to a block before punch has taken
> i_data_sem. I think putting i_mutex around the punch hole operation
> would fix this, but since we are trying to avoid further improper
> use of i_mutex, I am trying to avoid that solution.
Hey Allison,
Actually, i_mutex is the normal way to handle this. ocfs2 takes
i_mutex down under its ->fallocate(). Truncate is in the same boat,
which is why do_truncate() takes i_mutex before calling notify_change().
The read-write paths grab i_mutex for buffered operation. They
don't for O_DIRECT, which doesn't map to the pagecache. This is where
i_data_sem should speed things up.
Joel
--
"Anything that is too stupid to be spoken is sung."
- Voltaire
http://www.jlbec.org/
jlbec@evilplan.org
next prev parent reply other threads:[~2011-09-13 19:02 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-13 18:33 i_mutex questions Allison Henderson
2011-09-13 19:02 ` Joel Becker [this message]
2011-09-13 22:10 ` Allison Henderson
2011-09-14 0:05 ` Joel Becker
2011-09-14 1:29 ` Yongqiang Yang
2011-09-14 4:23 ` Andreas Dilger
2011-09-14 18:36 ` Allison Henderson
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