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@xxxxxxxxxxxx
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