From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx102.postini.com [74.125.245.102]) by kanga.kvack.org (Postfix) with SMTP id 4AD3A6B0031 for ; Sat, 27 Jul 2013 15:29:56 -0400 (EDT) Message-ID: <51F41FA0.6060205@parallels.com> Date: Sat, 27 Jul 2013 23:29:36 +0400 From: Pavel Emelyanov MIME-Version: 1.0 Subject: Re: [PATCH] mm: Save soft-dirty bits on file pages References: <20130726201807.GJ8661@moon> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andy Lutomirski Cc: Cyrill Gorcunov , Linux MM , LKML , Andrew Morton , Matt Mackall , Xiao Guangrong , Marcelo Tosatti , KOSAKI Motohiro , Stephen Rothwell On 07/27/2013 12:55 AM, Andy Lutomirski wrote: > On Fri, Jul 26, 2013 at 1:18 PM, Cyrill Gorcunov wrote: >> Andy reported that if file page get reclaimed we loose soft-dirty bit >> if it was there, so save _PAGE_BIT_SOFT_DIRTY bit when page address >> get encoded into pte entry. Thus when #pf happens on such non-present >> pte we can restore it back. >> > > Unless I'm misunderstanding this, it's saving the bit in the > non-present PTE. This sounds wrong -- what happens if the entire pmd > (or whatever the next level is called) gets zapped? (Also, what > happens if you unmap a file and map a different file there?) The whole pte gets zapped on vma unmap, and in this case forgetting the soft-dirty bit completely is OK. > --Andy > . > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org