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Date: Tue, 19 Sep 2006 22:20:29 +0200 From: Willy Tarreau <w@....eu> To: Nick Piggin <nickpiggin@...oo.com.au> Cc: Linux Kernel <linux-kernel@...r.kernel.org>, Marcelo Tosatti <mtosatti@...hat.com> Subject: Re: Linux 2.4.34-pre3 On Wed, Sep 20, 2006 at 04:55:25AM +1000, Nick Piggin wrote: > Willy Tarreau wrote: > >Hi Nick, > > > >On Wed, Sep 20, 2006 at 03:42:06AM +1000, Nick Piggin wrote: > > > >[cut -pre3 advertisement] > > > > > >>I wonder if 2.4 doesn't need the memory ordering fix to prevent pagecache > >>corruption in reclaim? (http://www.gatago.com/linux/kernel/14682626.html) > >> > >>What would need to be done is to test page_count before testing PageDirty, > >>and putting an smp_rmb between the two. > > > > > >I've read the thread, and Linus proposed to add an smp_wmb() in > >set_page_dirty() too. > > I think that isn't needed because put_page is a RMW, which is defined > to order memory. And presumably you wouldn't set the page dirty without > a reference to the page. OK, thanks for the explanation. > >I see that an smp_rmb() is already present > >in shrink_cache() with the adequate comment. > > So there is! My mistake then, I was confused and looking at > try_to_swap_out, but I see that doesn't actually free the page. Fine, > I think 2.4 is OK then. Perfect ! Thanks, Willy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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