xref: /openbmc/linux/fs/9p/vfs_addr.c (revision f35e839a)
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 long offset)
152 {
153 	/*
154 	 * If called with zero offset, we should release
155 	 * the private state assocated with the page
156 	 */
157 	if (offset == 0)
158 		v9fs_fscache_invalidate_page(page);
159 }
160 
161 static int v9fs_vfs_writepage_locked(struct page *page)
162 {
163 	char *buffer;
164 	int retval, len;
165 	loff_t offset, size;
166 	mm_segment_t old_fs;
167 	struct v9fs_inode *v9inode;
168 	struct inode *inode = page->mapping->host;
169 
170 	v9inode = V9FS_I(inode);
171 	size = i_size_read(inode);
172 	if (page->index == size >> PAGE_CACHE_SHIFT)
173 		len = size & ~PAGE_CACHE_MASK;
174 	else
175 		len = PAGE_CACHE_SIZE;
176 
177 	set_page_writeback(page);
178 
179 	buffer = kmap(page);
180 	offset = page_offset(page);
181 
182 	old_fs = get_fs();
183 	set_fs(get_ds());
184 	/* We should have writeback_fid always set */
185 	BUG_ON(!v9inode->writeback_fid);
186 
187 	retval = v9fs_file_write_internal(inode,
188 					  v9inode->writeback_fid,
189 					  (__force const char __user *)buffer,
190 					  len, &offset, 0);
191 	if (retval > 0)
192 		retval = 0;
193 
194 	set_fs(old_fs);
195 	kunmap(page);
196 	end_page_writeback(page);
197 	return retval;
198 }
199 
200 static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
201 {
202 	int retval;
203 
204 	retval = v9fs_vfs_writepage_locked(page);
205 	if (retval < 0) {
206 		if (retval == -EAGAIN) {
207 			redirty_page_for_writepage(wbc, page);
208 			retval = 0;
209 		} else {
210 			SetPageError(page);
211 			mapping_set_error(page->mapping, retval);
212 		}
213 	} else
214 		retval = 0;
215 
216 	unlock_page(page);
217 	return retval;
218 }
219 
220 /**
221  * v9fs_launder_page - Writeback a dirty page
222  * Returns 0 on success.
223  */
224 
225 static int v9fs_launder_page(struct page *page)
226 {
227 	int retval;
228 	struct inode *inode = page->mapping->host;
229 
230 	v9fs_fscache_wait_on_page_write(inode, page);
231 	if (clear_page_dirty_for_io(page)) {
232 		retval = v9fs_vfs_writepage_locked(page);
233 		if (retval)
234 			return retval;
235 	}
236 	return 0;
237 }
238 
239 /**
240  * v9fs_direct_IO - 9P address space operation for direct I/O
241  * @rw: direction (read or write)
242  * @iocb: target I/O control block
243  * @iov: array of vectors that define I/O buffer
244  * @pos: offset in file to begin the operation
245  * @nr_segs: size of iovec array
246  *
247  * The presence of v9fs_direct_IO() in the address space ops vector
248  * allowes open() O_DIRECT flags which would have failed otherwise.
249  *
250  * In the non-cached mode, we shunt off direct read and write requests before
251  * the VFS gets them, so this method should never be called.
252  *
253  * Direct IO is not 'yet' supported in the cached mode. Hence when
254  * this routine is called through generic_file_aio_read(), the read/write fails
255  * with an error.
256  *
257  */
258 static ssize_t
259 v9fs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
260 	       loff_t pos, unsigned long nr_segs)
261 {
262 	/*
263 	 * FIXME
264 	 * Now that we do caching with cache mode enabled, We need
265 	 * to support direct IO
266 	 */
267 	p9_debug(P9_DEBUG_VFS, "v9fs_direct_IO: v9fs_direct_IO (%s) off/no(%lld/%lu) EINVAL\n",
268 		 iocb->ki_filp->f_path.dentry->d_name.name,
269 		 (long long)pos, nr_segs);
270 
271 	return -EINVAL;
272 }
273 
274 static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
275 			    loff_t pos, unsigned len, unsigned flags,
276 			    struct page **pagep, void **fsdata)
277 {
278 	int retval = 0;
279 	struct page *page;
280 	struct v9fs_inode *v9inode;
281 	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
282 	struct inode *inode = mapping->host;
283 
284 	v9inode = V9FS_I(inode);
285 start:
286 	page = grab_cache_page_write_begin(mapping, index, flags);
287 	if (!page) {
288 		retval = -ENOMEM;
289 		goto out;
290 	}
291 	BUG_ON(!v9inode->writeback_fid);
292 	if (PageUptodate(page))
293 		goto out;
294 
295 	if (len == PAGE_CACHE_SIZE)
296 		goto out;
297 
298 	retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
299 	page_cache_release(page);
300 	if (!retval)
301 		goto start;
302 out:
303 	*pagep = page;
304 	return retval;
305 }
306 
307 static int v9fs_write_end(struct file *filp, struct address_space *mapping,
308 			  loff_t pos, unsigned len, unsigned copied,
309 			  struct page *page, void *fsdata)
310 {
311 	loff_t last_pos = pos + copied;
312 	struct inode *inode = page->mapping->host;
313 
314 	if (unlikely(copied < len)) {
315 		/*
316 		 * zero out the rest of the area
317 		 */
318 		unsigned from = pos & (PAGE_CACHE_SIZE - 1);
319 
320 		zero_user(page, from + copied, len - copied);
321 		flush_dcache_page(page);
322 	}
323 
324 	if (!PageUptodate(page))
325 		SetPageUptodate(page);
326 	/*
327 	 * No need to use i_size_read() here, the i_size
328 	 * cannot change under us because we hold the i_mutex.
329 	 */
330 	if (last_pos > inode->i_size) {
331 		inode_add_bytes(inode, last_pos - inode->i_size);
332 		i_size_write(inode, last_pos);
333 	}
334 	set_page_dirty(page);
335 	unlock_page(page);
336 	page_cache_release(page);
337 
338 	return copied;
339 }
340 
341 
342 const struct address_space_operations v9fs_addr_operations = {
343 	.readpage = v9fs_vfs_readpage,
344 	.readpages = v9fs_vfs_readpages,
345 	.set_page_dirty = __set_page_dirty_nobuffers,
346 	.writepage = v9fs_vfs_writepage,
347 	.write_begin = v9fs_write_begin,
348 	.write_end = v9fs_write_end,
349 	.releasepage = v9fs_release_page,
350 	.invalidatepage = v9fs_invalidate_page,
351 	.launder_page = v9fs_launder_page,
352 	.direct_IO = v9fs_direct_IO,
353 };
354