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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: linux-mm@kvack.org, lsf10-pc@lists.linuxfoundation.org
Cc: kosaki.motohiro@jp.fujitsu.com, Nick Piggin <npiggin@suse.de>
Subject: [LSF/MM TOPIC][ATTEND] How to fix direct-io vs fork issue
Date: Thu,  1 Apr 2010 16:41:21 +0900 (JST)	[thread overview]
Message-ID: <20100401154419.BE4C.A69D9226@jp.fujitsu.com> (raw)

Hi

I would like to ask about one difficult problem about people.
currently, direct-io implementation has big sick about VM interaction.
it assume get_user_pages() can pin the target pages in page's mm. but 
it doesn't. fork and cow might replace the relationship between task's mm
and pages. therefore cuncurrent directio and fork can corrupt the process's
data.

There was two proposal in past day. 1) introduce new page flags 2)
introduce new lock. unfortunately both proposal got strong complaint
from other developers. then, we still have this issue.

I don't have clever idea. I hope discuss how to fix or give it up.


thanks to linus. his recent read_pagemap discussion restre my memory that
I need post this mail.



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             reply	other threads:[~2010-04-01  7:41 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-04-01  7:41 KOSAKI Motohiro [this message]
2010-04-01 17:23 ` [Lsf10-pc] " Andrea Arcangeli

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