fs/9p/vfs_addr.c

   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  */
  52 static 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
  84 done:
  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
  98 static 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
 113 static 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
 137 static 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
 151 static 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
 162 static 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
 201 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 202 {
 203         int retval;
 204
 205         p9_debug(P9_DEBUG_VFS, "page %p\n", page);
 206
 207         retval = v9fs_vfs_writepage_locked(page);
 208         if (retval < 0) {
 209                 if (retval == -EAGAIN) {
 210                         redirty_page_for_writepage(wbc, page);
 211                         retval = 0;
 212                 } else {
 213                         SetPageError(page);
 214                         mapping_set_error(page->mapping, retval);
 215                 }
 216         } else
 217                 retval = 0;
 218
 219         unlock_page(page);
 220         return retval;
 221 }
 222
 223 /**
 224  * v9fs_launder_page - Writeback a dirty page
 225  * Returns 0 on success.
 226  */
 227
 228 static int v9fs_launder_page(struct page *page)
 229 {
 230         int retval;
 231         struct inode *inode = page->mapping->host;
 232
 233         v9fs_fscache_wait_on_page_write(inode, page);
 234         if (clear_page_dirty_for_io(page)) {
 235                 retval = v9fs_vfs_writepage_locked(page);
 236                 if (retval)
 237                         return retval;
 238         }
 239         return 0;
 240 }
 241
 242 /**
 243  * v9fs_direct_IO - 9P address space operation for direct I/O
 244  * @rw: direction (read or write)
 245  * @iocb: target I/O control block
 246  * @iov: array of vectors that define I/O buffer
 247  * @pos: offset in file to begin the operation
 248  * @nr_segs: size of iovec array
 249  *
 250  * The presence of v9fs_direct_IO() in the address space ops vector
 251  * allowes open() O_DIRECT flags which would have failed otherwise.
 252  *
 253  * In the non-cached mode, we shunt off direct read and write requests before
 254  * the VFS gets them, so this method should never be called.
 255  *
 256  * Direct IO is not 'yet' supported in the cached mode. Hence when
 257  * this routine is called through generic_file_aio_read(), the read/write fails
 258  * with an error.
 259  *
 260  */
 261 static ssize_t
 262 v9fs_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
 263 {
 264         /*
 265          * FIXME
 266          * Now that we do caching with cache mode enabled, We need
 267          * to support direct IO
 268          */
 269         p9_debug(P9_DEBUG_VFS, "v9fs_direct_IO: v9fs_direct_IO (%s) off/no(%lld/%lu) EINVAL\n",
 270                  iocb->ki_filp->f_path.dentry->d_name.name,
 271                  (long long)pos, iter->nr_segs);
 272
 273         return -EINVAL;
 274 }
 275
 276 static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 277                             loff_t pos, unsigned len, unsigned flags,
 278                             struct page **pagep, void **fsdata)
 279 {
 280         int retval = 0;
 281         struct page *page;
 282         struct v9fs_inode *v9inode;
 283         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 284         struct inode *inode = mapping->host;
 285
 286
 287         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 288
 289         v9inode = V9FS_I(inode);
 290 start:
 291         page = grab_cache_page_write_begin(mapping, index, flags);
 292         if (!page) {
 293                 retval = -ENOMEM;
 294                 goto out;
 295         }
 296         BUG_ON(!v9inode->writeback_fid);
 297         if (PageUptodate(page))
 298                 goto out;
 299
 300         if (len == PAGE_CACHE_SIZE)
 301                 goto out;
 302
 303         retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
 304         page_cache_release(page);
 305         if (!retval)
 306                 goto start;
 307 out:
 308         *pagep = page;
 309         return retval;
 310 }
 311
 312 static int v9fs_write_end(struct file *filp, struct address_space *mapping,
 313                           loff_t pos, unsigned len, unsigned copied,
 314                           struct page *page, void *fsdata)
 315 {
 316         loff_t last_pos = pos + copied;
 317         struct inode *inode = page->mapping->host;
 318
 319         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 320
 321         if (unlikely(copied < len)) {
 322                 /*
 323                  * zero out the rest of the area
 324                  */
 325                 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 326
 327                 zero_user(page, from + copied, len - copied);
 328                 flush_dcache_page(page);
 329         }
 330
 331         if (!PageUptodate(page))
 332                 SetPageUptodate(page);
 333         /*
 334          * No need to use i_size_read() here, the i_size
 335          * cannot change under us because we hold the i_mutex.
 336          */
 337         if (last_pos > inode->i_size) {
 338                 inode_add_bytes(inode, last_pos - inode->i_size);
 339                 i_size_write(inode, last_pos);
 340         }
 341         set_page_dirty(page);
 342         unlock_page(page);
 343         page_cache_release(page);
 344
 345         return copied;
 346 }
 347
 348
 349 const struct address_space_operations v9fs_addr_operations = {
 350         .readpage = v9fs_vfs_readpage,
 351         .readpages = v9fs_vfs_readpages,
 352         .set_page_dirty = __set_page_dirty_nobuffers,
 353         .writepage = v9fs_vfs_writepage,
 354         .write_begin = v9fs_write_begin,
 355         .write_end = v9fs_write_end,
 356         .releasepage = v9fs_release_page,
 357         .invalidatepage = v9fs_invalidate_page,
 358         .launder_page = v9fs_launder_page,
 359         .direct_IO = v9fs_direct_IO,
 360 };