Re: [PATCH v2 3/3] NFS: Fix a memory leak in nfs_readdir

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 01 Dec 2010 15:10:50 -0500
Trond Myklebust <Trond.Myklebust@netapp.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?