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 <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         struct inode *inode = page->mapping->host;
  55         struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
  56         struct iov_iter to;
  57         int retval, err;
  58
  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         iov_iter_bvec(&to, ITER_BVEC | READ, &bvec, 1, PAGE_SIZE);
  68
  69         retval = p9_client_read(fid, page_offset(page), &to, &err);
  70         if (err) {
  71                 v9fs_uncache_page(inode, page);
  72                 retval = err;
  73                 goto done;
  74         }
  75
  76         zero_user(page, retval, PAGE_SIZE - retval);
  77         flush_dcache_page(page);
  78         SetPageUptodate(page);
  79
  80         v9fs_readpage_to_fscache(inode, page);
  81         retval = 0;
  82
  83 done:
  84         unlock_page(page);
  85         return retval;
  86 }
  87
  88 /**
  89  * v9fs_vfs_readpage - read an entire page in from 9P
  90  *
  91  * @filp: file being read
  92  * @page: structure to page
  93  *
  94  */
  95
  96 static int v9fs_vfs_readpage(struct file *filp, struct page *page)
  97 {
  98         return v9fs_fid_readpage(filp->private_data, page);
  99 }
 100
 101 /**
 102  * v9fs_vfs_readpages - read a set of pages from 9P
 103  *
 104  * @filp: file being read
 105  * @mapping: the address space
 106  * @pages: list of pages to read
 107  * @nr_pages: count of pages to read
 108  *
 109  */
 110
 111 static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
 112                              struct list_head *pages, unsigned nr_pages)
 113 {
 114         int ret = 0;
 115         struct inode *inode;
 116
 117         inode = mapping->host;
 118         p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
 119
 120         ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
 121         if (ret == 0)
 122                 return ret;
 123
 124         ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
 125         p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
 126         return ret;
 127 }
 128
 129 /**
 130  * v9fs_release_page - release the private state associated with a page
 131  *
 132  * Returns 1 if the page can be released, false otherwise.
 133  */
 134
 135 static int v9fs_release_page(struct page *page, gfp_t gfp)
 136 {
 137         if (PagePrivate(page))
 138                 return 0;
 139         return v9fs_fscache_release_page(page, gfp);
 140 }
 141
 142 /**
 143  * v9fs_invalidate_page - Invalidate a page completely or partially
 144  *
 145  * @page: structure to page
 146  * @offset: offset in the page
 147  */
 148
 149 static void v9fs_invalidate_page(struct page *page, unsigned int offset,
 150                                  unsigned int length)
 151 {
 152         /*
 153          * If called with zero offset, we should release
 154          * the private state assocated with the page
 155          */
 156         if (offset == 0 && length == PAGE_CACHE_SIZE)
 157                 v9fs_fscache_invalidate_page(page);
 158 }
 159
 160 static int v9fs_vfs_writepage_locked(struct page *page)
 161 {
 162         struct inode *inode = page->mapping->host;
 163         struct v9fs_inode *v9inode = V9FS_I(inode);
 164         loff_t size = i_size_read(inode);
 165         struct iov_iter from;
 166         struct bio_vec bvec;
 167         int err, len;
 168
 169         if (page->index == size >> PAGE_CACHE_SHIFT)
 170                 len = size & ~PAGE_CACHE_MASK;
 171         else
 172                 len = PAGE_CACHE_SIZE;
 173
 174         bvec.bv_page = page;
 175         bvec.bv_offset = 0;
 176         bvec.bv_len = len;
 177         iov_iter_bvec(&from, ITER_BVEC | WRITE, &bvec, 1, len);
 178
 179         /* We should have writeback_fid always set */
 180         BUG_ON(!v9inode->writeback_fid);
 181
 182         set_page_writeback(page);
 183
 184         p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
 185
 186         end_page_writeback(page);
 187         return err;
 188 }
 189
 190 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 191 {
 192         int retval;
 193
 194         p9_debug(P9_DEBUG_VFS, "page %p\n", page);
 195
 196         retval = v9fs_vfs_writepage_locked(page);
 197         if (retval < 0) {
 198                 if (retval == -EAGAIN) {
 199                         redirty_page_for_writepage(wbc, page);
 200                         retval = 0;
 201                 } else {
 202                         SetPageError(page);
 203                         mapping_set_error(page->mapping, retval);
 204                 }
 205         } else
 206                 retval = 0;
 207
 208         unlock_page(page);
 209         return retval;
 210 }
 211
 212 /**
 213  * v9fs_launder_page - Writeback a dirty page
 214  * Returns 0 on success.
 215  */
 216
 217 static int v9fs_launder_page(struct page *page)
 218 {
 219         int retval;
 220         struct inode *inode = page->mapping->host;
 221
 222         v9fs_fscache_wait_on_page_write(inode, page);
 223         if (clear_page_dirty_for_io(page)) {
 224                 retval = v9fs_vfs_writepage_locked(page);
 225                 if (retval)
 226                         return retval;
 227         }
 228         return 0;
 229 }
 230
 231 /**
 232  * v9fs_direct_IO - 9P address space operation for direct I/O
 233  * @rw: direction (read or write)
 234  * @iocb: target I/O control block
 235  * @iov: array of vectors that define I/O buffer
 236  * @pos: offset in file to begin the operation
 237  * @nr_segs: size of iovec array
 238  *
 239  * The presence of v9fs_direct_IO() in the address space ops vector
 240  * allowes open() O_DIRECT flags which would have failed otherwise.
 241  *
 242  * In the non-cached mode, we shunt off direct read and write requests before
 243  * the VFS gets them, so this method should never be called.
 244  *
 245  * Direct IO is not 'yet' supported in the cached mode. Hence when
 246  * this routine is called through generic_file_aio_read(), the read/write fails
 247  * with an error.
 248  *
 249  */
 250 static ssize_t
 251 v9fs_direct_IO(int rw, struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
 252 {
 253         struct file *file = iocb->ki_filp;
 254         ssize_t n;
 255         int err = 0;
 256         if (rw & WRITE) {
 257                 n = p9_client_write(file->private_data, pos, iter, &err);
 258                 if (n) {
 259                         struct inode *inode = file_inode(file);
 260                         loff_t i_size = i_size_read(inode);
 261                         if (pos + n > i_size)
 262                                 inode_add_bytes(inode, pos + n - i_size);
 263                 }
 264         } else {
 265                 n = p9_client_read(file->private_data, pos, iter, &err);
 266         }
 267         return n ? n : err;
 268 }
 269
 270 static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
 271                             loff_t pos, unsigned len, unsigned flags,
 272                             struct page **pagep, void **fsdata)
 273 {
 274         int retval = 0;
 275         struct page *page;
 276         struct v9fs_inode *v9inode;
 277         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 278         struct inode *inode = mapping->host;
 279
 280
 281         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 282
 283         v9inode = V9FS_I(inode);
 284 start:
 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;
 301 out:
 302         *pagep = page;
 303         return retval;
 304 }
 305
 306 static 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         p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
 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
 343 const 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 };