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(void *data, struct page *page)
  54 {
  55         struct p9_fid *fid = data;
  56         struct inode *inode = page->mapping->host;
  57         struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
  58         struct iov_iter to;
  59         int retval, err;
  60
  61         p9_debug(P9_DEBUG_VFS, "\n");
  62
  63         BUG_ON(!PageLocked(page));
  64
  65         retval = v9fs_readpage_from_fscache(inode, page);
  66         if (retval == 0)
  67                 return retval;
  68
  69         iov_iter_bvec(&to, ITER_BVEC | READ, &bvec, 1, PAGE_SIZE);
  70
  71         retval = p9_client_read(fid, page_offset(page), &to, &err);
  72         if (err) {
  73                 v9fs_uncache_page(inode, page);
  74                 retval = err;
  75                 goto done;
  76         }
  77
  78         zero_user(page, retval, PAGE_SIZE - retval);
  79         flush_dcache_page(page);
  80         SetPageUptodate(page);
  81
  82         v9fs_readpage_to_fscache(inode, page);
  83         retval = 0;
  84
  85 done:
  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, v9fs_fid_readpage,
 127                         filp->private_data);
 128         p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
 129         return ret;
 130 }
 131
 132 /**
 133  * v9fs_release_page - release the private state associated with a page
 134  *
 135  * Returns 1 if the page can be released, false otherwise.
 136  */
 137
 138 static int v9fs_release_page(struct page *page, gfp_t gfp)
 139 {
 140         if (PagePrivate(page))
 141                 return 0;
 142         return v9fs_fscache_release_page(page, gfp);
 143 }
 144
 145 /**
 146  * v9fs_invalidate_page - Invalidate a page completely or partially
 147  *
 148  * @page: structure to page
 149  * @offset: offset in the page
 150  */
 151
 152 static void v9fs_invalidate_page(struct page *page, unsigned int offset,
 153                                  unsigned int length)
 154 {
 155         /*
 156          * If called with zero offset, we should release
 157          * the private state assocated with the page
 158          */
 159         if (offset == 0 && length == PAGE_SIZE)
 160                 v9fs_fscache_invalidate_page(page);
 161 }
 162
 163 static int v9fs_vfs_writepage_locked(struct page *page)
 164 {
 165         struct inode *inode = page->mapping->host;
 166         struct v9fs_inode *v9inode = V9FS_I(inode);
 167         loff_t size = i_size_read(inode);
 168         struct iov_iter from;
 169         struct bio_vec bvec;
 170         int err, len;
 171
 172         if (page->index == size >> PAGE_SHIFT)
 173                 len = size & ~PAGE_MASK;
 174         else
 175                 len = PAGE_SIZE;
 176
 177         bvec.bv_page = page;
 178         bvec.bv_offset = 0;
 179         bvec.bv_len = len;
 180         iov_iter_bvec(&from, ITER_BVEC | WRITE, &bvec, 1, len);
 181
 182         /* We should have writeback_fid always set */
 183         BUG_ON(!v9inode->writeback_fid);
 184
 185         set_page_writeback(page);
 186
 187         p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
 188
 189         end_page_writeback(page);
 190         return err;
 191 }
 192
 193 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
 194 {
 195         int retval;
 196
 197         p9_debug(P9_DEBUG_VFS, "page %p\n", page);
 198
 199         retval = v9fs_vfs_writepage_locked(page);
 200         if (retval < 0) {
 201                 if (retval == -EAGAIN) {
 202                         redirty_page_for_writepage(wbc, page);
 203                         retval = 0;
 204                 } else {
 205                         SetPageError(page);
 206                         mapping_set_error(page->mapping, retval);
 207                 }
 208         } else
 209                 retval = 0;
 210
 211         unlock_page(page);
 212         return retval;
 213 }
 214
 215 /**
 216  * v9fs_launder_page - Writeback a dirty page
 217  * Returns 0 on success.
 218  */
 219
 220 static int v9fs_launder_page(struct page *page)
 221 {
 222         int retval;
 223         struct inode *inode = page->mapping->host;
 224
 225         v9fs_fscache_wait_on_page_write(inode, page);
 226         if (clear_page_dirty_for_io(page)) {
 227                 retval = v9fs_vfs_writepage_locked(page);
 228                 if (retval)
 229                         return retval;
 230         }
 231         return 0;
 232 }
 233
 234 /**
 235  * v9fs_direct_IO - 9P address space operation for direct I/O
 236  * @iocb: target I/O control block
 237  *
 238  * The presence of v9fs_direct_IO() in the address space ops vector
 239  * allowes open() O_DIRECT flags which would have failed otherwise.
 240  *
 241  * In the non-cached mode, we shunt off direct read and write requests before
 242  * the VFS gets them, so this method should never be called.
 243  *
 244  * Direct IO is not 'yet' supported in the cached mode. Hence when
 245  * this routine is called through generic_file_aio_read(), the read/write fails
 246  * with an error.
 247  *
 248  */
 249 static ssize_t
 250 v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 251 {
 252         struct file *file = iocb->ki_filp;
 253         loff_t pos = iocb->ki_pos;
 254         ssize_t n;
 255         int err = 0;
 256         if (iov_iter_rw(iter) == 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_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_SIZE)
 295                 goto out;
 296
 297         retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
 298         put_page(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 (!PageUptodate(page)) {
 316                 if (unlikely(copied < len)) {
 317                         copied = 0;
 318                         goto out;
 319                 } else if (len == PAGE_SIZE) {
 320                         SetPageUptodate(page);
 321                 }
 322         }
 323         /*
 324          * No need to use i_size_read() here, the i_size
 325          * cannot change under us because we hold the i_mutex.
 326          */
 327         if (last_pos > inode->i_size) {
 328                 inode_add_bytes(inode, last_pos - inode->i_size);
 329                 i_size_write(inode, last_pos);
 330         }
 331         set_page_dirty(page);
 332 out:
 333         unlock_page(page);
 334         put_page(page);
 335
 336         return copied;
 337 }
 338
 339
 340 const struct address_space_operations v9fs_addr_operations = {
 341         .readpage = v9fs_vfs_readpage,
 342         .readpages = v9fs_vfs_readpages,
 343         .set_page_dirty = __set_page_dirty_nobuffers,
 344         .writepage = v9fs_vfs_writepage,
 345         .write_begin = v9fs_write_begin,
 346         .write_end = v9fs_write_end,
 347         .releasepage = v9fs_release_page,
 348         .invalidatepage = v9fs_invalidate_page,
 349         .launder_page = v9fs_launder_page,
 350         .direct_IO = v9fs_direct_IO,
 351 };