linux-kernel - Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content corruption on ext3)

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Date:	Sun, 24 Dec 2006 22:10:54 +0200
From:	Andrei Popa <andrei.popa@...eo.ro>
To:	Linus Torvalds <torvalds@...l.org>
Cc:	Gordon Farquharson <gordonfarquharson@...il.com>,
	Andrew Morton <akpm@...l.org>,
	Martin Michlmayr <tbm@...ius.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hugh Dickins <hugh@...itas.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Arjan van de Ven <arjan@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: fix page_mkclean_one (was: 2.6.19 file content
	corruption on ext3)

On Sun, 2006-12-24 at 11:35 -0800, Linus Torvalds wrote:
> 
> On Sun, 24 Dec 2006, Gordon Farquharson wrote:
> > 
> > The apt cache files (/var/cache/apt/*.bin) still get corrupted with
> > this patch and 2.6.19.
> 
> Yeah, if my guess about do_no_page() is right, _none_ of the previous 
> patches should have ANY effect what-so-ever. In fact, I'd say that even 
> the "ext3 works in writeback mode" thing that Andrei reports is probably a 
> total fluke brought on by timing changes rather than anything else.
> 
> So please try the latest patch instead (on top of anything that shows 
> corruption reliably - the patch should be _totally_ independent of all the 
> other issues, and I think it will apply cleanly on top of 2.6.18.3 and 
> 2.6.19 too, so anything that shows corruption is a fine target - but try 
> to choose something that has been the "best" at corrupting things for you, 
> to make the testing as good as possible).
> 
> Patch included here again (although I think you were cc'd on my previous 
> email too, so you should already have it, and our emails just crossed)
> 
> And if this doesn't fix it, I don't know what will..

With latest git and patches:
http://lkml.org/lkml/diff/2006/12/24/56/1
http://lkml.org/lkml/diff/2006/12/24/61/1

Hash check on download completion found bad chunks, consider using
"safe_sync".

> 
> 		Linus
> 
> ---
> diff --git a/mm/memory.c b/mm/memory.c
> index 563792f..cf429c4 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2247,21 +2249,23 @@ retry:
>  	if (pte_none(*page_table)) {
>  		flush_icache_page(vma, new_page);
>  		entry = mk_pte(new_page, vma->vm_page_prot);
> -		if (write_access)
> -			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> -		set_pte_at(mm, address, page_table, entry);
>  		if (anon) {
>  			inc_mm_counter(mm, anon_rss);
>  			lru_cache_add_active(new_page);
>  			page_add_new_anon_rmap(new_page, vma, address);
> +			if (write_access)
> +				entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>  		} else {
>  			inc_mm_counter(mm, file_rss);
>  			page_add_file_rmap(new_page);
> +			entry = pte_wrprotect(entry);
>  			if (write_access) {
>  				dirty_page = new_page;
>  				get_page(dirty_page);
> +				entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>  			}
>  		}
> +		set_pte_at(mm, address, page_table, entry);
>  	} else {
>  		/* One of our sibling threads was faster, back out. */
>  		page_cache_release(new_page);

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