[pnfs] [PATCH 19/28] pnfs: pnfs_write_begin

[Benny Halevy]

On Mar. 11, 2008, 21:32 +0200, Fred Isaman <iisaman at citi.umich.edu> wrote:
> From: Fred <iisaman at citi.umich.edu>
> 
> Add hooks in the nfs_write_begin path, giving a driver the potential
> to read in page data around the data that is about to be copied to the page.
> 
> Signed-off-by: Fred <iisaman at citi.umich.edu>
> ---
>  fs/nfs/file.c             |   20 ++++++++--
>  fs/nfs/pnfs.c             |   88 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/nfs/pnfs.h             |   10 +++++
>  fs/nfs/write.c            |    2 +-
>  include/linux/nfs4_pnfs.h |   15 +++++++-
>  5 files changed, 129 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
> index 6f16772..e870982 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -352,10 +352,19 @@ static int nfs_write_begin(struct file *file, struct address_space *mapping,
>  	*pagep = page;
>  
>  	ret = nfs_flush_incompatible(file, page);
> -	if (ret) {
> -		unlock_page(page);
> -		page_cache_release(page);
> -	}
> +	if (ret)
> +		goto out_err;
> +#ifdef CONFIG_PNFS
> +	ret = pnfs_write_begin(file, page, pos, len, flags, fsdata);
> +	if (ret)
> +		goto out_err;
> +#endif /* CONFIG_PNFS */
> +	return 0;
> +
> + out_err:
> +	unlock_page(page);
> +	page_cache_release(page);
> +	*pagep = NULL;
>  	return ret;
>  }
>  
> @@ -372,6 +381,9 @@ static int nfs_write_end(struct file *file, struct address_space *mapping,
>  
>  	unlock_page(page);
>  	page_cache_release(page);
> +#ifdef CONFIG_PNFS
> +	pnfs_free_fsdata(fsdata);
> +#endif /* CONFIG_PNFS */
>  
>  	return status < 0 ? status : copied;
>  }
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 56aa1bf..a4db86e 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -809,6 +809,28 @@ pnfs_has_layout(struct pnfs_layout_type *lo,
>  	return ret;
>  }
>  
> +static struct pnfs_layout_segment *
> +pnfs_find_get_lseg(struct inode *inode,
> +		   loff_t pos,
> +		   size_t count,
> +		   enum pnfs_iomode iomode)
> +{
> +	struct nfs_inode *nfsi = NFS_I(inode);
> +	struct pnfs_layout_segment *lseg;
> +	struct pnfs_layout_type *lo;
> +	struct nfs4_pnfs_layout_segment range;
> +
> +	lo = get_lock_current_layout(nfsi);
> +	if (!lo)
> +		return NULL;
> +	range.iomode = iomode;
> +	range.offset = pos;
> +	range.length = count;
> +	lseg = pnfs_has_layout(lo, &range, 1);
> +	put_unlock_current_layout(nfsi, lo);
> +	return lseg;
> +}
> +
>  /* Update the file's layout for the given range and iomode.
>   * Layout is retreived from the server if needed.
>   * If lsegpp is given, the appropriate layout segment is referenced and
> @@ -1537,6 +1559,64 @@ int pnfs_try_to_read_data(struct nfs_read_data *data,
>  	}
>  }
>  
> +/*
> + * This gives the layout driver an opportunity to read in page "around"
> + * the data to be written.  It returns 0 on success, otherwise an error code
> + * which will either be passed up to user, or ignored if
> + * some previous part of write succeeded.
> + * Note the range [pos, pos+len-1] is entirely within the page.
> + */
> +/* flags = AOP_FLAG_UNINTERRUPTIBLE or 0 - ??? need this ??? */
> +int pnfs_write_begin(struct file *filp, struct page *page,
> +		     loff_t pos, unsigned len,
> +		     unsigned flags, void **fsdata)
> +{
> +	struct inode *inode = filp->f_dentry->d_inode;
> +	struct nfs_server *nfss = NFS_SERVER(inode);
> +	struct pnfs_layout_segment *lseg;
> +	struct pnfs_fsdata *pnfs_fsdata = NULL;
> +	int status = 0;
> +
> +	if (!nfss->pnfs_curr_ld || !nfss->pnfs_curr_ld->ld_io_ops ||
> +	    !nfss->pnfs_curr_ld->ld_io_ops->write_begin) {
> +		/* If layout driver doesn't define, just do nothing */
> +		goto out;
> +	}
> +	lseg = pnfs_find_get_lseg(inode, pos, len, IOMODE_RW);
> +	status = nfss->pnfs_curr_ld->ld_io_ops->write_begin(lseg, page,
> +							    pos, len,
> +							    &pnfs_fsdata);
> +	put_lseg(lseg);
> +	if (pnfs_fsdata && !pnfs_fsdata->ld_io_ops)
> +		pnfs_fsdata->ld_io_ops = nfss->pnfs_curr_ld->ld_io_ops;
> + out:
> +	*fsdata = pnfs_fsdata;

One more comment. Can fsdata be NULL?

Benny