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