[RFC] [PATCH 2/7] [net/9p] Adds supporting functions for zero copy.

["Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>]

On 2/6/2011 11:21 PM, Venkateswararao Jujjuri (JV) wrote:
> Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
> ---
>  net/9p/Makefile       |    1 +
>  net/9p/trans_common.c |   88 +++++++++++++++++++++++++++++++++++++++++++++++++
>  net/9p/trans_common.h |   26 ++++++++++++++
>  3 files changed, 115 insertions(+), 0 deletions(-)
>  create mode 100644 net/9p/trans_common.c
>  create mode 100644 net/9p/trans_common.h
> 
> diff --git a/net/9p/Makefile b/net/9p/Makefile
> index 198a640..a0874cc 100644
> --- a/net/9p/Makefile
> +++ b/net/9p/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_NET_9P_RDMA) += 9pnet_rdma.o
>  	util.o \
>  	protocol.o \
>  	trans_fd.o \
> +	trans_common.o \
> 
>  9pnet_virtio-objs := \
>  	trans_virtio.o \
> diff --git a/net/9p/trans_common.c b/net/9p/trans_common.c
> new file mode 100644
> index 0000000..dad57d2
> --- /dev/null
> +++ b/net/9p/trans_common.c
> @@ -0,0 +1,88 @@
> +/*
> + * Copyright IBM Corporation, 2010
> + * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of version 2.1 of the GNU Lesser General Public License
> + * as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it would be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> + *
> + */
> +
> +#include <linux/slab.h>
> +#include <net/9p/9p.h>
> +#include <net/9p/client.h>
> +#include <linux/scatterlist.h>
> +#include "trans_common.h"
> +
> +/**
> + *  p9_release_req_pages - Release pages after the transaction.
> + *  @*private: PDU's private page of type virtio_rpage_info_t
> + */
> +void
> +p9_release_req_pages(void *private)
> +{
> +	virtio_rpage_info_t *vpinfo = private;
> +	int i = 0;
> +
> +	while (vpinfo->vp_data[i] && vpinfo->vp_nr_pages--) {
> +		put_page(vpinfo->vp_data[i]);
> +		i++;
> +	}
> +}
> +
> +/**
> + * payload_gup - Calculates number of pages that needs to be pinned and
> + * pins them ehter for read/write through get_user_pages_fast().
> + */
> +int
> +payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len, u8 rw)
> +{
> +	int nr_pages;
> +	uint32_t first_page_bytes = 0;
> +	uint32_t pdata_mapped_pages;
> +	virtio_rpage_info_t  *rpinfo;
> +
> +	nr_pages = req->tc->pbuf_size >> PAGE_SHIFT;
> +	*pdata_off = (size_t)req->tc->pbuf & (PAGE_SIZE-1);
> +
> +	if (*pdata_off)
> +		first_page_bytes = min((PAGE_SIZE - *pdata_off),
> +				req->tc->pbuf_size);
> +
> +	if (req->tc->pbuf_size - (first_page_bytes + (nr_pages << PAGE_SHIFT))){
> +		/* trailing partial page */
> +		nr_pages++;
> +	}       
> +	if (first_page_bytes) {
> +		/* leading partial page */
> +		nr_pages++;
> +	}
> +	/* TODO: Use buffer on PDU instead of allocating */
> +	rpinfo = kmalloc(sizeof(virtio_rpage_info_t) +
> +			sizeof(struct page *) * nr_pages, GFP_KERNEL);
> +	req->tc->private = (void *)rpinfo;
> +	pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pbuf,
> +			nr_pages, rw, &rpinfo->vp_data[0]);
> +
> +	if (pdata_mapped_pages < 0) {
> +		printk("get_user_pages_fast failed:%d udata:%p" "nr_pages:%d\n",
> +				pdata_mapped_pages, req->tc->pbuf, nr_pages);
> +		pdata_mapped_pages = 0;
> +		kfree(rpinfo);
> +		return -EIO;
> +	}
> +	rpinfo->vp_nr_pages = pdata_mapped_pages;
> +	if (*pdata_off) {
> +		*pdata_len = first_page_bytes;
> +		*pdata_len += min((req->tc->pbuf_size - *pdata_len),
> +				((size_t)pdata_mapped_pages - 1) << PAGE_SHIFT);
> +	} else {
> +		*pdata_len = min (req->tc->pbuf_size,
> +				(size_t)pdata_mapped_pages << PAGE_SHIFT);
> +	}
> +	return 0;
> +}
> diff --git a/net/9p/trans_common.h b/net/9p/trans_common.h
> new file mode 100644
> index 0000000..8c85392
> --- /dev/null
> +++ b/net/9p/trans_common.h
> @@ -0,0 +1,26 @@
> +/*
> + * Copyright IBM Corporation, 2010
> + * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of version 2.1 of the GNU Lesser General Public License
> + * as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it would be useful, but
> + * WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> + *
> + */
> +
> +/**
> + * struct virtio_rpage_info - To store mapped page information in PDU.
> + * @vp_nr_pages: Number of mapped pages
> + * @vp_data: Array of page pointers
> + */
> +typedef struct virtio_rpage_info {
> +       int vp_nr_pages;
> +       struct page *vp_data[0];
> +} virtio_rpage_info_t;
> +
> +void p9_release_req_pages(void *);
> +int payload_gup(struct p9_req_t *, size_t *, int *, u8);