linux-kernel - Re: [PATCH v2 3/5] nfs: don't dirty ITER

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Date:	Mon, 5 Jan 2015 09:41:00 -0500
From:	Anna Schumaker <Anna.Schumaker@...app.com>
To:	Omar Sandoval <osandov@...ndov.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Christoph Hellwig <hch@...radead.org>,
	<linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
	<linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] nfs: don't dirty ITER_BVEC pages read through
 direct I/O

Hi Omar,

On 12/19/2014 10:18 PM, Omar Sandoval wrote:
> As with the generic blockdev code, kernel pages shouldn't be dirtied by
> the direct I/O path.
> 
> Signed-off-by: Omar Sandoval <osandov@...ndov.com>
> ---
>  fs/nfs/direct.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index 10bf072..b6ca65c 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -88,6 +88,7 @@ struct nfs_direct_req {
>  	struct pnfs_ds_commit_info ds_cinfo;	/* Storage for cinfo */
>  	struct work_struct	work;
>  	int			flags;
> +	int			should_dirty;	/* should we mark read pages dirty? */
>  #define NFS_ODIRECT_DO_COMMIT		(1)	/* an unstable reply was received */
>  #define NFS_ODIRECT_RESCHED_WRITES	(2)	/* write verification failed */
>  	struct nfs_writeverf	verf;		/* unstable write verifier */

Can you add should_dirty after the NFS_ODIRECT_* flags?

Thanks,
Anna

> @@ -370,7 +371,8 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr)
>  		struct nfs_page *req = nfs_list_entry(hdr->pages.next);
>  		struct page *page = req->wb_page;
>  
> -		if (!PageCompound(page) && bytes < hdr->good_bytes)
> +		if (!PageCompound(page) && bytes < hdr->good_bytes &&
> +		    dreq->should_dirty)
>  			set_page_dirty(page);
>  		bytes += req->wb_bytes;
>  		nfs_list_remove_request(req);
> @@ -542,6 +544,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
>  	dreq->inode = inode;
>  	dreq->bytes_left = count;
>  	dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
> +	dreq->should_dirty = !iov_iter_is_bvec(iter);
>  	l_ctx = nfs_get_lock_context(dreq->ctx);
>  	if (IS_ERR(l_ctx)) {
>  		result = PTR_ERR(l_ctx);
> 

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