From mboxrd@z Thu Jan  1 00:00:00 1970
From: Omar Sandoval <osandov-nWWhXC5lh1RBDgjK7y7TUQ@public.gmane.org>
Subject: Re: [PATCH v2 4/5] swapfile: use ->read_iter and ->write_iter
Date: Sun, 21 Dec 2014 23:32:34 -0800
Message-ID: <20141222073234.GA14207@mew>
References: <cover.1419044605.git.osandov@osandov.com>
 <d8819b57849221b3db7c479f070067808912f0d5.1419044605.git.osandov@osandov.com>
 <20141220061337.GB22149@ZenIV.linux.org.uk>
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Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Trond Myklebust <trond.myklebust-7I+n7zu2hftEKMMhf/gKZA@public.gmane.org>,
	Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org>
To: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
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On Sat, Dec 20, 2014 at 06:13:37AM +0000, Al Viro wrote:
> On Fri, Dec 19, 2014 at 07:18:28PM -0800, Omar Sandoval wrote:
> 
> > +		ret = swap_file->f_op->read_iter(&kiocb, &to);
> > +		if (ret == PAGE_SIZE) {
> > +			SetPageUptodate(page);
> >  			count_vm_event(PSWPIN);
> > +			ret = 0;
> > +		} else {
> > +			ClearPageUptodate(page);
> > +			SetPageError(page);
> > +		}
> > +		unlock_page(page);
> 
> Umm...  What's to guarantee that ->read_iter() won't try lock_page() on what
> turns out to be equal to page?

Ergh. I don't see why ->read_iter would be screwing around in the swap
cache or with the pages in the iterator, anything in particular you can
see happening?

-- 
Omar
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