Date: Wed, 1 Dec 2010 15:46:51 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Nick Piggin <npiggin@kernel.dk>,
        Nick Bowler <nbowler@elliptictech.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-nfs@vger.kernel.org, Rik van Riel <riel@redhat.com>,
        Christoph Hellwig <hch@lst.de>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v2 3/3] NFS: Fix a memory leak in nfs_readdir
Message-Id: <20101201154651.958678f6.akpm@linux-foundation.org>
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On Wed, 01 Dec 2010 18:21:16 -0500
Trond Myklebust <Trond.Myklebust@netapp.com> wrote:

> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -108,6 +108,10 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
>  	clear_page_mlock(page);
>  	remove_from_page_cache(page);
>  	ClearPageMappedToDisk(page);
> +
> +	if (mapping->a_ops->freepage)
> +		mapping->a_ops->freepage(page);
> +
>  	page_cache_release(page);	/* pagecache ref */
>  	return 0;
>  }

So here we're assuming that `mapping' was pinned by other means.

Fair enough, although subtle.  Even drop_pagecache_sb() got it right ;)

> @@ -390,6 +394,10 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page)
>  	__remove_from_page_cache(page);
>  	spin_unlock_irq(&mapping->tree_lock);
>  	mem_cgroup_uncharge_cache_page(page);
> +
> +	if (mapping->a_ops->freepage)
> +		mapping->a_ops->freepage(page);
> +
>  	page_cache_release(page);	/* pagecache ref */
>  	return 1;
>  failed:

And here.