[net/9p] Preparation and helper functions for zero copy
[linux-2.6.git] / net / 9p / trans_common.c
1 /*
2  * Copyright IBM Corporation, 2010
3  * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms of version 2.1 of the GNU Lesser General Public License
7  * as published by the Free Software Foundation.
8  *
9  * This program is distributed in the hope that it would be useful, but
10  * WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
12  *
13  */
14
15 #include <linux/slab.h>
16 #include <linux/module.h>
17 #include <net/9p/9p.h>
18 #include <net/9p/client.h>
19 #include <linux/scatterlist.h>
20 #include "trans_common.h"
21
22 /**
23  *  p9_release_req_pages - Release pages after the transaction.
24  *  @*private: PDU's private page of struct trans_rpage_info
25  */
26 void
27 p9_release_req_pages(struct trans_rpage_info *rpinfo)
28 {
29         int i = 0;
30
31         while (rpinfo->rp_data[i] && rpinfo->rp_nr_pages--) {
32                 put_page(rpinfo->rp_data[i]);
33                 i++;
34         }
35 }
36 EXPORT_SYMBOL(p9_release_req_pages);
37
38 /**
39  * p9_nr_pages - Return number of pages needed to accomodate the payload.
40  */
41 int
42 p9_nr_pages(struct p9_req_t *req)
43 {
44         int start_page, end_page;
45         start_page =  (unsigned long long)req->tc->pubuf >> PAGE_SHIFT;
46         end_page = ((unsigned long long)req->tc->pubuf + req->tc->pbuf_size +
47                         PAGE_SIZE - 1) >> PAGE_SHIFT;
48         return end_page - start_page;
49 }
50 EXPORT_SYMBOL(p9_nr_pages);
51
52 /**
53  * payload_gup - Translates user buffer into kernel pages and
54  * pins them either for read/write through get_user_pages_fast().
55  * @req: Request to be sent to server.
56  * @pdata_off: data offset into the first page after translation (gup).
57  * @pdata_len: Total length of the IO. gup may not return requested # of pages.
58  * @nr_pages: number of pages to accomodate the payload
59  * @rw: Indicates if the pages are for read or write.
60  */
61 int
62 p9_payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len,
63                 int nr_pages, u8 rw)
64 {
65         uint32_t first_page_bytes = 0;
66         uint32_t pdata_mapped_pages;
67         struct trans_rpage_info  *rpinfo;
68
69         *pdata_off = (size_t)req->tc->pubuf & (PAGE_SIZE-1);
70
71         if (*pdata_off)
72                 first_page_bytes = min((PAGE_SIZE - *pdata_off),
73                                 req->tc->pbuf_size);
74
75         rpinfo = req->tc->private;
76         pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pubuf,
77                         nr_pages, rw, &rpinfo->rp_data[0]);
78
79         if (pdata_mapped_pages < 0) {
80                 printk(KERN_ERR "get_user_pages_fast failed:%d udata:%p"
81                                 "nr_pages:%d\n", pdata_mapped_pages,
82                                 req->tc->pubuf, nr_pages);
83                 pdata_mapped_pages = 0;
84                 return -EIO;
85         }
86         rpinfo->rp_nr_pages = pdata_mapped_pages;
87         if (*pdata_off) {
88                 *pdata_len = first_page_bytes;
89                 *pdata_len += min((req->tc->pbuf_size - *pdata_len),
90                                 ((size_t)pdata_mapped_pages - 1) << PAGE_SHIFT);
91         } else {
92                 *pdata_len = min(req->tc->pbuf_size,
93                                 (size_t)pdata_mapped_pages << PAGE_SHIFT);
94         }
95         return 0;
96 }
97 EXPORT_SYMBOL(p9_payload_gup);