linux-kernel - Re: [PATCH] nfs: fix nfs

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Date:	Wed, 17 Oct 2007 11:25:02 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] nfs: fix nfs_writepage()


On Wed, 2007-10-17 at 15:40 +0200, Peter Zijlstra wrote:
> I noticed that ->writepage() didn't actually do anything since it
> doesn't generate a write request for the given page.
> 
> The below is an attempt at fixing it, and it works for me. Although I'm
> not quite sure its the proper fix.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  fs/nfs/write.c |   20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> Index: linux-2.6/fs/nfs/write.c
> ===================================================================
> --- linux-2.6.orig/fs/nfs/write.c
> +++ linux-2.6/fs/nfs/write.c
> @@ -332,10 +332,30 @@ static int nfs_page_async_flush(struct n
>  static int nfs_do_writepage(struct page *page, struct writeback_control *wbc, struct nfs_pageio_descriptor *pgio)
>  {
>  	struct inode *inode = page_file_mapping(page)->host;
> +	struct rpc_cred *cred;
> +	struct nfs_open_context *ctx;
> +	int status;
>  
>  	nfs_inc_stats(inode, NFSIOS_VFSWRITEPAGE);
>  	nfs_add_stats(inode, NFSIOS_WRITEPAGES, 1);
>  
> +	cred = rpcauth_lookupcred(NFS_CLIENT(inode)->cl_auth, 0);
> +	if (IS_ERR(cred))
> +		return PTR_ERR(cred);
> +
> +	ctx = nfs_find_open_context(inode, cred, FMODE_WRITE);
> +	if (!ctx)
> +		return -EBADF;
> +
> +	status = nfs_writepage_setup(ctx, page, 0, nfs_page_length(page));
> +
> +	put_nfs_open_context(ctx);
> +
> +	if (status < 0) {
> +		nfs_set_pageerror(page);
> +		return status;
> +	}
> +
>  	nfs_pageio_cond_complete(pgio, page_file_index(page));
>  	return nfs_page_async_flush(pgio, page);
>  }

NACK. writepage()'s job is simply to start writeout on the page.
nfs_vm_page_mkwrite(), and nfs_commit_write() actually set up the
nfs_page structure before we ever get to writepage().

Cheers
  Trond

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