linux/fs/9p/vfs_addr.c
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   1/*
   2 *  linux/fs/9p/vfs_addr.c
   3 *
   4 * This file contians vfs address (mmap) ops for 9P2000.
   5 *
   6 *  Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
   7 *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
   8 *
   9 *  This program is free software; you can redistribute it and/or modify
  10 *  it under the terms of the GNU General Public License version 2
  11 *  as published by the Free Software Foundation.
  12 *
  13 *  This program is distributed in the hope that it will be useful,
  14 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 *  GNU General Public License for more details.
  17 *
  18 *  You should have received a copy of the GNU General Public License
  19 *  along with this program; if not, write to:
  20 *  Free Software Foundation
  21 *  51 Franklin Street, Fifth Floor
  22 *  Boston, MA  02111-1301  USA
  23 *
  24 */
  25
  26#include <linux/module.h>
  27#include <linux/errno.h>
  28#include <linux/fs.h>
  29#include <linux/file.h>
  30#include <linux/stat.h>
  31#include <linux/string.h>
  32#include <linux/inet.h>
  33#include <linux/pagemap.h>
  34#include <linux/idr.h>
  35#include <linux/sched.h>
  36#include <linux/aio.h>
  37#include <net/9p/9p.h>
  38#include <net/9p/client.h>
  39
  40#include "v9fs.h"
  41#include "v9fs_vfs.h"
  42#include "cache.h"
  43#include "fid.h"
  44
  45/**
  46 * v9fs_fid_readpage - read an entire page in from 9P
  47 *
  48 * @fid: fid being read
  49 * @page: structure to page
  50 *
  51 */
  52static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page)
  53{
  54        int retval;
  55        loff_t offset;
  56        char *buffer;
  57        struct inode *inode;
  58
  59        inode = page->mapping->host;
  60        p9_debug(P9_DEBUG_VFS, "\n");
  61
  62        BUG_ON(!PageLocked(page));
  63
  64        retval = v9fs_readpage_from_fscache(inode, page);
  65        if (retval == 0)
  66                return retval;
  67
  68        buffer = kmap(page);
  69        offset = page_offset(page);
  70
  71        retval = v9fs_fid_readn(fid, buffer, NULL, PAGE_CACHE_SIZE, offset);
  72        if (retval < 0) {
  73                v9fs_uncache_page(inode, page);
  74                goto done;
  75        }
  76
  77        memset(buffer + retval, 0, PAGE_CACHE_SIZE - retval);
  78        flush_dcache_page(page);
  79        SetPageUptodate(page);
  80
  81        v9fs_readpage_to_fscache(inode, page);
  82        retval = 0;
  83
  84done:
  85        kunmap(page);
  86        unlock_page(page);
  87        return retval;
  88}
  89
  90/**
  91 * v9fs_vfs_readpage - read an entire page in from 9P
  92 *
  93 * @filp: file being read
  94 * @page: structure to page
  95 *
  96 */
  97
  98static int v9fs_vfs_readpage(struct file *filp, struct page *page)
  99{
 100        return v9fs_fid_readpage(filp->private_data, page);
 101}
 102
 103/**
 104 * v9fs_vfs_readpages - read a set of pages from 9P
 105 *
 106 * @filp: file being read
 107 * @mapping: the address space
 108 * @pages: list of pages to read
 109 * @nr_pages: count of pages to read
 110 *
 111 */
 112
 113static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
 114                             struct list_head *pages, unsigned nr_pages)
 115{
 116        int ret = 0;
 117        struct inode *inode;
 118
 119        inode = mapping->host;
 120        p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
 121
 122        ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
 123        if (ret == 0)
 124                return ret;
 125
 126        ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
 127        p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
 128        return ret;
 129}
 130
 131/**
 132 * v9fs_release_page - release the private state associated with a page
 133 *
 134 * Returns 1 if the page can be released, false otherwise.
 135 */
 136
 137static int v9fs_release_page(struct page *page, gfp_t gfp)
 138{
 139        if (PagePrivate(page))
 140                return 0;
 141        return v9fs_fscache_release_page(page, gfp);
 142}
 143
 144/**
 145 * v9fs_invalidate_page - Invalidate a page completely or partially
 146 *
 147 * @page: structure to page
 148 * @offset: offset in the page
 149 */
 150
 151static void v9fs_invalidate_page(struct page *page, unsigned int offset,
 152                                 unsigned int length)
 153{
 154        /*
 155         * If called with zero offset, we should release
 156         * the private state assocated with the page
 157         */
 158        if (offset == 0 && length == PAGE_CACHE_SIZE)
 159                v9fs_fscache_invalidate_page(page);
 160}
 161
 162static int v9fs_vfs_writepage_locked(struct page *page)
 163{
 164        char *buffer;
 165        int retval, len;
 166        loff_t offset, size;
 167        mm_segment_t old_fs;
 168        struct v9fs_inode *v9inode;
 169        struct inode *inode = page->mapping->host;
 170
 171        v9inode = V9FS_I(inode);
 172        size = i_size_read(inode);
 173        if (page->index == size >> PAGE_CACHE_SHIFT)
 174                len = size & ~PAGE_CACHE_MASK;
 175        else
 176                len = PAGE_CACHE_SIZE;
 177
 178        set_page_writeback(page);
 179
 180        buffer = kmap(page);
 181        offset = page_offset(page);
 182
 183        old_fs = get_fs();
 184        set_fs(get_ds());
 185        /* We should have writeback_fid always set */
 186        BUG_ON(!v9inode->writeback_fid);
 187
 188        retval = v9fs_file_write_internal(inode,
 189                                          v9inode->writeback_fid,
 190                                          (__force const char __user *)buffer,
 191                                          len, &offset, 0);
 192        if (retval > 0)
 193                retval = 0;
 194
 195        set_fs(old_fs);
 196        kunmap(page);
 197        end_page_writeback(page);
 198        return retval;
 199}
 200
 201static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 202{
 203        int retval;
 204
 205        retval = v9fs_vfs_writepage_locked(page);
 206        if (retval < 0) {
 207                if (retval == -EAGAIN) {
 208                        redirty_page_for_writepage(wbc, page);
 209                        retval = 0;
 210                } else {
 211                        SetPageError(page);
 212                        mapping_set_error(page->mapping, retval);
 213                }
 214        } else
 215                retval = 0;
 216
 217        unlock_page(page);
 218        return retval;
 219}
 220
 221/**
 222 * v9fs_launder_page - Writeback a dirty page
 223 * Returns 0 on success.
 224 */
 225
 226static int v9fs_launder_page(struct page *page)
 227{
 228        int retval;
 229        struct inode *inode = page->mapping->host;
 230
 231        v9fs_fscache_wait_on_page_write(inode, page);
 232        if (clear_page_dirty_for_io(page)) {
 233                retval = v9fs_vfs_writepage_locked(page);
 234                if (retval)
 235                        return retval;
 236        }
 237        return 0;
 238}
 239
 240/**
 241 * v9fs_direct_IO - 9P address space operation for direct I/O
 242 * @rw: direction (read or write)
 243 * @iocb: target I/O control block
 244 * @iov: array of vectors that define I/O buffer
 245 * @pos: offset in file to begin the operation
 246 * @nr_segs: size of iovec array
 247 *
 248 * The presence of v9fs_direct_IO() in the address space ops vector
 249 * allowes open() O_DIRECT flags which would have failed otherwise.
 250 *
 251 * In the non-cached mode, we shunt off direct read and write requests before
 252 * the VFS gets them, so this method should never be called.
 253 *
 254 * Direct IO is not 'yet' supported in the cached mode. Hence when
 255 * this routine is called through generic_file_aio_read(), the read/write fails
 256 * with an error.
 257 *
 258 */
 259static ssize_t
 260v9fs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 261               loff_t pos, unsigned long nr_segs)
 262{
 263        /*
 264         * FIXME
 265         * Now that we do caching with cache mode enabled, We need
 266         * to support direct IO
 267         */
 268        p9_debug(P9_DEBUG_VFS, "v9fs_direct_IO: v9fs_direct_IO (%s) off/no(%lld/%lu) EINVAL\n",
 269                 iocb->ki_filp->f_path.dentry->d_name.name,
 270                 (long long)pos, nr_segs);
 271
 272        return -EINVAL;
 273}
 274
 275static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 276                            loff_t pos, unsigned len, unsigned flags,
 277                            struct page **pagep, void **fsdata)
 278{
 279        int retval = 0;
 280        struct page *page;
 281        struct v9fs_inode *v9inode;
 282        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 283        struct inode *inode = mapping->host;
 284
 285        v9inode = V9FS_I(inode);
 286start:
 287        page = grab_cache_page_write_begin(mapping, index, flags);
 288        if (!page) {
 289                retval = -ENOMEM;
 290                goto out;
 291        }
 292        BUG_ON(!v9inode->writeback_fid);
 293        if (PageUptodate(page))
 294                goto out;
 295
 296        if (len == PAGE_CACHE_SIZE)
 297                goto out;
 298
 299        retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
 300        page_cache_release(page);
 301        if (!retval)
 302                goto start;
 303out:
 304        *pagep = page;
 305        return retval;
 306}
 307
 308static int v9fs_write_end(struct file *filp, struct address_space *mapping,
 309                          loff_t pos, unsigned len, unsigned copied,
 310                          struct page *page, void *fsdata)
 311{
 312        loff_t last_pos = pos + copied;
 313        struct inode *inode = page->mapping->host;
 314
 315        if (unlikely(copied < len)) {
 316                /*
 317                 * zero out the rest of the area
 318                 */
 319                unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 320
 321                zero_user(page, from + copied, len - copied);
 322                flush_dcache_page(page);
 323        }
 324
 325        if (!PageUptodate(page))
 326                SetPageUptodate(page);
 327        /*
 328         * No need to use i_size_read() here, the i_size
 329         * cannot change under us because we hold the i_mutex.
 330         */
 331        if (last_pos > inode->i_size) {
 332                inode_add_bytes(inode, last_pos - inode->i_size);
 333                i_size_write(inode, last_pos);
 334        }
 335        set_page_dirty(page);
 336        unlock_page(page);
 337        page_cache_release(page);
 338
 339        return copied;
 340}
 341
 342
 343const struct address_space_operations v9fs_addr_operations = {
 344        .readpage = v9fs_vfs_readpage,
 345        .readpages = v9fs_vfs_readpages,
 346        .set_page_dirty = __set_page_dirty_nobuffers,
 347        .writepage = v9fs_vfs_writepage,
 348        .write_begin = v9fs_write_begin,
 349        .write_end = v9fs_write_end,
 350        .releasepage = v9fs_release_page,
 351        .invalidatepage = v9fs_invalidate_page,
 352        .launder_page = v9fs_launder_page,
 353        .direct_IO = v9fs_direct_IO,
 354};
 355
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