xref: /openbmc/linux/fs/9p/vfs_addr.c (revision 09c434b8)
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, 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, 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 (!PageUptodate(page)) {
314  		if (unlikely(copied < len)) {
315  			copied = 0;
316  			goto out;
317  		} else if (len == PAGE_SIZE) {
318  			SetPageUptodate(page);
319  		}
320  	}
321  	/*
322  	 * No need to use i_size_read() here, the i_size
323  	 * cannot change under us because we hold the i_mutex.
324  	 */
325  	if (last_pos > inode->i_size) {
326  		inode_add_bytes(inode, last_pos - inode->i_size);
327  		i_size_write(inode, last_pos);
328  	}
329  	set_page_dirty(page);
330  out:
331  	unlock_page(page);
332  	put_page(page);
333  
334  	return copied;
335  }
336  
337  
338  const struct address_space_operations v9fs_addr_operations = {
339  	.readpage = v9fs_vfs_readpage,
340  	.readpages = v9fs_vfs_readpages,
341  	.set_page_dirty = __set_page_dirty_nobuffers,
342  	.writepage = v9fs_vfs_writepage,
343  	.write_begin = v9fs_write_begin,
344  	.write_end = v9fs_write_end,
345  	.releasepage = v9fs_release_page,
346  	.invalidatepage = v9fs_invalidate_page,
347  	.launder_page = v9fs_launder_page,
348  	.direct_IO = v9fs_direct_IO,
349  };
350