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  */
  25 void p9_release_pages(struct page **pages, int nr_pages)
  26 {
  27         int i = 0;
  28         while (pages[i] && nr_pages--) {
  29                 put_page(pages[i]);
  30                 i++;
  31         }
  32 }
  33 EXPORT_SYMBOL(p9_release_pages);
  34
  35 /**
  36  * p9_nr_pages - Return number of pages needed to accommodate the payload.
  37  */
  38 int p9_nr_pages(char *data, int len)
  39 {
  40         unsigned long start_page, end_page;
  41         start_page =  (unsigned long)data >> PAGE_SHIFT;
  42         end_page = ((unsigned long)data + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
  43         return end_page - start_page;
  44 }
  45 EXPORT_SYMBOL(p9_nr_pages);
  46
  47 /**
  48  * payload_gup - Translates user buffer into kernel pages and
  49  * pins them either for read/write through get_user_pages_fast().
  50  * @req: Request to be sent to server.
  51  * @pdata_off: data offset into the first page after translation (gup).
  52  * @pdata_len: Total length of the IO. gup may not return requested # of pages.
  53  * @nr_pages: number of pages to accommodate the payload
  54  * @rw: Indicates if the pages are for read or write.
  55  */
  56
  57 int p9_payload_gup(char *data, int *nr_pages, struct page **pages, int write)
  58 {
  59         int nr_mapped_pages;
  60
  61         nr_mapped_pages = get_user_pages_fast((unsigned long)data,
  62                                               *nr_pages, write, pages);
  63         if (nr_mapped_pages <= 0)
  64                 return nr_mapped_pages;
  65
  66         *nr_pages = nr_mapped_pages;
  67         return 0;
  68 }
  69 EXPORT_SYMBOL(p9_payload_gup);