linux-kernel - Re: [PATCH 0/2] Updating ctime and mtime for memory-mapped files [try #4]

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Date:	Wed, 16 Jan 2008 01:15:59 +0300
From:	"Anton Salikhmetov" <salikhmetov@...il.com>
To:	"Miklos Szeredi" <miklos@...redi.hu>
Cc:	linux-mm@...ck.org, jakob@...hought.net,
	linux-kernel@...r.kernel.org, valdis.kletnieks@...edu,
	riel@...hat.com, ksm@...dk, staubach@...hat.com,
	jesper.juhl@...il.com, torvalds@...ux-foundation.org,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	protasnb@...il.com
Subject: Re: [PATCH 0/2] Updating ctime and mtime for memory-mapped files [try #4]

2008/1/15, Miklos Szeredi <miklos@...redi.hu>:
> > 1. Introduction
> >
> > This is the fourth version of my solution for the bug #2645:
> >
> > http://bugzilla.kernel.org/show_bug.cgi?id=2645
> >
> > Changes since the previous version:
> >
> > 1) the case of retouching an already-dirty page pointed out
> >   by Miklos Szeredi has been addressed;
>
> I'm a bit sceptical, as we've also pointed out, that this is not
> possible without messing with the page tables.
>
> Did you try my test program on the patched kernel?

I just tried your test program. Alas, my assumption appears to be wrong.

Thank you for your comment!

Now I start thinking that it is better not to care about
the MS_ASYNC case whatsoever.

>
> I've refreshed the patch, where we left this issue last time.  It
> should basically have equivalent functionality to your patch, and is a
> lot simpler.  There might be performance issues with it, but it's a
> good starting point.
>
> Miklos
> ----
>
> Index: linux/mm/memory.c
> ===================================================================
> --- linux.orig/mm/memory.c      2008-01-09 21:16:30.000000000 +0100
> +++ linux/mm/memory.c   2008-01-15 21:16:14.000000000 +0100
> @@ -1680,6 +1680,8 @@ gotten:
>  unlock:
>         pte_unmap_unlock(page_table, ptl);
>         if (dirty_page) {
> +               if (vma->vm_file)
> +                       file_update_time(vma->vm_file);
>                 /*
>                  * Yes, Virginia, this is actually required to prevent a race
>                  * with clear_page_dirty_for_io() from clearing the page dirty
> @@ -2313,6 +2315,8 @@ out_unlocked:
>         if (anon)
>                 page_cache_release(vmf.page);
>         else if (dirty_page) {
> +               if (vma->vm_file)
> +                       file_update_time(vma->vm_file);
>                 set_page_dirty_balance(dirty_page, page_mkwrite);
>                 put_page(dirty_page);
>         }
>
>
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