linux-kernel - Re: [fuse-devel] [PATCH 14/14] mm: Account for WRITEBACK_TEMP in balance_dirty

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Date:	Thu, 25 Apr 2013 17:49:58 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	"Maxim V. Patlasov" <mpatlasov@...allels.com>
Cc:	Kirill Korotaev <dev@...allels.com>,
	Pavel Emelianov <xemul@...allels.com>,
	"fuse-devel@...ts.sourceforge.net" <fuse-devel@...ts.sourceforge.net>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	James Bottomley <jbottomley@...allels.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>, devel@...nvz.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	fengguang.wu@...el.com
Subject: Re: [fuse-devel] [PATCH 14/14] mm: Account for WRITEBACK_TEMP in balance_dirty_pages

On Thu, Apr 25, 2013 at 4:29 PM, Maxim V. Patlasov
<mpatlasov@...allels.com> wrote:
>> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
>> index 0713bfb..c47bcd4 100644
>> --- a/mm/page-writeback.c
>> +++ b/mm/page-writeback.c
>> @@ -1235,7 +1235,8 @@ static void balance_dirty_pages(struct address_space
>> *mapping,
>>                  */
>>                 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
>>
>> global_page_state(NR_UNSTABLE_NFS);
>> -               nr_dirty = nr_reclaimable +
>> global_page_state(NR_WRITEBACK);
>> +               nr_dirty = nr_reclaimable +
>> global_page_state(NR_WRITEBACK) +
>> +                       global_page_state(NR_WRITEBACK_TEMP);
>>                 global_dirty_limits(&background_thresh, &dirty_thresh);
>
>
> Please drop this patch. As we discussed in LSF/MM, the fix above is correct,
> but it's not enough: we also need to ensure disregard of NR_WRITEBACK_TEMP
> when balance_dirty_pages() is called from fuse daemon. I'll send a separate
> patch-set soon.

Please elaborate.  From a technical perspective "fuse daemon" is very
hard to define, so anything that relies on whether something came from
the fuse daemon or not is conceptually broken.

Thanks,
Miklos
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