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From: Robin Holt <holt@sgi.com>
To: Al Viro <viro@ftp.linux.org.uk>
Cc: Dean Nelson <dcn@sgi.com>,
	akpm@linux-foundation.org, linux-ia64@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	tony.luck@intel.com, jes@sgi.com
Subject: Re: [PATCH 1/4] export __put_task_struct for XPMEM
Date: Mon, 27 Aug 2007 15:24:20 -0500	[thread overview]
Message-ID: <20070827202420.GE22922@lnx-holt.americas.sgi.com> (raw)
In-Reply-To: <20070827193510.GJ21089@ftp.linux.org.uk>

On Mon, Aug 27, 2007 at 08:35:10PM +0100, Al Viro wrote:
> On Mon, Aug 27, 2007 at 02:19:06PM -0500, Dean Nelson wrote:
> 
> > No operations can be done once it's closed, only while it's opened.
> 
> What the hell do you mean, can't be done?
> 
> 	fd = open(...);
> 	fp = popen("/bin/date", "r");
> 	/* read from fp */
> 	fclose(fp);

But this will operate on the dup'd fd.  We detect that in the flush
(ignore) and ioctl (return errors) operations.  All other operations
are not handled by xpmem.

If you look at the fourth patch, at the beginning of the xpmem_flush
function, we have:

+       tg = xpmem_tg_ref_by_tgid(xpmem_my_part, current->tgid);
+       if (IS_ERR(tg))
+               return 0;  /* probably child process who inherited fd */

This will protect the xpmem structures of the parent from closes by
the child.

Thanks,
Robin

  reply	other threads:[~2007-08-27 20:30 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-27 15:56 [PATCH 0/4] SGI Altix cross partition memory (XPMEM) Dean Nelson
2007-08-27 15:59 ` [PATCH 1/4] export __put_task_struct for XPMEM Dean Nelson
2007-08-27 16:13   ` Al Viro
2007-08-27 18:10     ` Dean Nelson
2007-08-27 18:15       ` Al Viro
2007-08-27 19:19         ` Dean Nelson
2007-08-27 19:35           ` Al Viro
2007-08-27 20:24             ` Robin Holt [this message]
2007-08-27 20:47               ` Al Viro
2007-08-28 18:01       ` Christoph Hellwig
2007-08-27 16:01 ` [PATCH 2/4] export zap_page_range " Dean Nelson
2007-08-27 16:02 ` [PATCH 3/4] add new lock ordering rule to mm/filemap.c Dean Nelson
2007-08-27 16:41 ` [PATCH 4/4] add SGI Altix cross partition memory (XPMEM) driver Dean Nelson
2007-08-27 20:00   ` Adrian Bunk
2007-08-28 18:02   ` Christoph Hellwig
2007-08-28 19:00     ` Robin Holt
2007-08-28 19:05       ` Christoph Hellwig

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