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/uio.h>
  37 #include <linux/bvec.h>
  38 #include <net/9p/9p.h>
  39 #include <net/9p/client.h>
  40
  41 #include "v9fs.h"
  42 #include "v9fs_vfs.h"
  43 #include "cache.h"
  44 #include "fid.h"
  45
  46 /**
  47  * v9fs_fid_readpage - read an entire page in from 9P
  48  *
  49  * @fid: fid being read
  50  * @page: structure to page
  51  *
  52  */
  53 static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page)
  54 {
  55         struct inode *inode = page->mapping->host;
  56         struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
  57         struct iov_iter to;
  58         int retval, err;
  59
  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         iov_iter_bvec(&to, ITER_BVEC | READ, &bvec, 1, PAGE_SIZE);
  69
  70         retval = p9_client_read(fid, page_offset(page), &to, &err);
  71         if (err) {
  72                 v9fs_uncache_page(inode, page);
  73                 retval = err;
  74                 goto done;
  75         }
  76
  77         zero_user(page, retval, PAGE_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         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
  97 static 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
 112 static 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
 136 static 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
 150 static void v9fs_invalidate_page(struct page *page, unsigned int offset,
 151                                  unsigned int length)
 152 {
 153         /*
 154          * If called with zero offset, we should release
 155          * the private state assocated with the page
 156          */
 157         if (offset == 0 && length == PAGE_SIZE)
 158                 v9fs_fscache_invalidate_page(page);
 159 }
 160
 161 static int v9fs_vfs_writepage_locked(struct page *page)
 162 {
 163         struct inode *inode = page->mapping->host;
 164         struct v9fs_inode *v9inode = V9FS_I(inode);
 165         loff_t size = i_size_read(inode);
 166         struct iov_iter from;
 167         struct bio_vec bvec;
 168         int err, len;
 169
 170         if (page->index == size >> PAGE_SHIFT)
 171                 len = size & ~PAGE_MASK;
 172         else
 173                 len = PAGE_SIZE;
 174
 175         bvec.bv_page = page;
 176         bvec.bv_offset = 0;
 177         bvec.bv_len = len;
 178         iov_iter_bvec(&from, ITER_BVEC | WRITE, &bvec, 1, len);
 179
 180         /* We should have writeback_fid always set */
 181         BUG_ON(!v9inode->writeback_fid);
 182
 183         set_page_writeback(page);
 184
 185         p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
 186
 187         end_page_writeback(page);
 188         return err;
 189 }
 190
 191 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 192 {
 193         int retval;
 194
 195         p9_debug(P9_DEBUG_VFS, "page %p\n", page);
 196
 197         retval = v9fs_vfs_writepage_locked(page);
 198         if (retval < 0) {
 199                 if (retval == -EAGAIN) {
 200                         redirty_page_for_writepage(wbc, page);
 201                         retval = 0;
 202                 } else {
 203                         SetPageError(page);
 204                         mapping_set_error(page->mapping, retval);
 205                 }
 206         } else
 207                 retval = 0;
 208
 209         unlock_page(page);
 210         return retval;
 211 }
 212
 213 /**
 214  * v9fs_launder_page - Writeback a dirty page
 215  * Returns 0 on success.
 216  */
 217
 218 static int v9fs_launder_page(struct page *page)
 219 {
 220         int retval;
 221         struct inode *inode = page->mapping->host;
 222
 223         v9fs_fscache_wait_on_page_write(inode, page);
 224         if (clear_page_dirty_for_io(page)) {
 225                 retval = v9fs_vfs_writepage_locked(page);
 226                 if (retval)
 227                         return retval;
 228         }
 229         return 0;
 230 }
 231
 232 /**
 233  * v9fs_direct_IO - 9P address space operation for direct I/O
 234  * @iocb: target I/O control block
 235  *
 236  * The presence of v9fs_direct_IO() in the address space ops vector
 237  * allowes open() O_DIRECT flags which would have failed otherwise.
 238  *
 239  * In the non-cached mode, we shunt off direct read and write requests before
 240  * the VFS gets them, so this method should never be called.
 241  *
 242  * Direct IO is not 'yet' supported in the cached mode. Hence when
 243  * this routine is called through generic_file_aio_read(), the read/write fails
 244  * with an error.
 245  *
 246  */
 247 static ssize_t
 248 v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 249 {
 250         struct file *file = iocb->ki_filp;
 251         loff_t pos = iocb->ki_pos;
 252         ssize_t n;
 253         int err = 0;
 254         if (iov_iter_rw(iter) == WRITE) {
 255                 n = p9_client_write(file->private_data, pos, iter, &err);
 256                 if (n) {
 257                         struct inode *inode = file_inode(file);
 258                         loff_t i_size = i_size_read(inode);
 259                         if (pos + n > i_size)
 260                                 inode_add_bytes(inode, pos + n - i_size);
 261                 }
 262         } else {
 263                 n = p9_client_read(file->private_data, pos, iter, &err);
 264         }
 265         return n ? n : err;
 266 }
 267
 268 static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 269                             loff_t pos, unsigned len, unsigned flags,
 270                             struct page **pagep, void **fsdata)
 271 {
 272         int retval = 0;
 273         struct page *page;
 274         struct v9fs_inode *v9inode;
 275         pgoff_t index = pos >> PAGE_SHIFT;
 276         struct inode *inode = mapping->host;
 277
 278
 279         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 280
 281         v9inode = V9FS_I(inode);
 282 start:
 283         page = grab_cache_page_write_begin(mapping, index, flags);
 284         if (!page) {
 285                 retval = -ENOMEM;
 286                 goto out;
 287         }
 288         BUG_ON(!v9inode->writeback_fid);
 289         if (PageUptodate(page))
 290                 goto out;
 291
 292         if (len == PAGE_SIZE)
 293                 goto out;
 294
 295         retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
 296         put_page(page);
 297         if (!retval)
 298                 goto start;
 299 out:
 300         *pagep = page;
 301         return retval;
 302 }
 303
 304 static int v9fs_write_end(struct file *filp, struct address_space *mapping,
 305                           loff_t pos, unsigned len, unsigned copied,
 306                           struct page *page, void *fsdata)
 307 {
 308         loff_t last_pos = pos + copied;
 309         struct inode *inode = page->mapping->host;
 310
 311         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 312
 313         if (unlikely(copied < len && !PageUptodate(page))) {
 314                 copied = 0;
 315                 goto out;
 316         }
 317         /*
 318          * No need to use i_size_read() here, the i_size
 319          * cannot change under us because we hold the i_mutex.
 320          */
 321         if (last_pos > inode->i_size) {
 322                 inode_add_bytes(inode, last_pos - inode->i_size);
 323                 i_size_write(inode, last_pos);
 324         }
 325         set_page_dirty(page);
 326 out:
 327         unlock_page(page);
 328         put_page(page);
 329
 330         return copied;
 331 }
 332
 333
 334 const struct address_space_operations v9fs_addr_operations = {
 335         .readpage = v9fs_vfs_readpage,
 336         .readpages = v9fs_vfs_readpages,
 337         .set_page_dirty = __set_page_dirty_nobuffers,
 338         .writepage = v9fs_vfs_writepage,
 339         .write_begin = v9fs_write_begin,
 340         .write_end = v9fs_write_end,
 341         .releasepage = v9fs_release_page,
 342         .invalidatepage = v9fs_invalidate_page,
 343         .launder_page = v9fs_launder_page,
 344         .direct_IO = v9fs_direct_IO,
 345 };