linux-kernel - Re: [PATCH v2 3/3] NFS: Fix a memory leak in nfs

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Message-Id: <20101201123341.d12ef362.akpm@linux-foundation.org>
Date:	Wed, 1 Dec 2010 12:33:41 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Bowler <nbowler@...iptictech.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-nfs@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Christoph Hellwig <hch@....de>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 3/3] NFS: Fix a memory leak in nfs_readdir

On Wed, 01 Dec 2010 15:10:50 -0500
Trond Myklebust <Trond.Myklebust@...app.com> wrote:

> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -602,6 +602,7 @@ struct address_space_operations {
>  	sector_t (*bmap)(struct address_space *, sector_t);
>  	void (*invalidatepage) (struct page *, unsigned long);
>  	int (*releasepage) (struct page *, gfp_t);
> +	void (*freepage)(struct page *);
>  	ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
>  			loff_t offset, unsigned long nr_segs);
>  	int (*get_xip_mem)(struct address_space *, pgoff_t, int,

It would be good to think about and then clearly spell out exactly what
state the page is in here.  It is locked, and I assume clean and not
under writeback.  What about its refcount, freezedness status and
eligibility for lookups?

And as Hugh pointed out, some callees might needs the address_space*
although we can perhaps defer that until such a callee turns up. 
If/when that happens we might have a problem though: if this locked
page is no longer attached to the address_space then what now pins the
address_space, protecting it from inode reclaim?
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