1 /* AFS filesystem file handling
2  *
3  * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/fs.h>
16 #include <linux/pagemap.h>
17 #include <linux/writeback.h>
18 #include <linux/gfp.h>
19 #include "internal.h"
20 
21 static int afs_readpage(struct file *file, struct page *page);
22 static void afs_invalidatepage(struct page *page, unsigned long offset);
23 static int afs_releasepage(struct page *page, gfp_t gfp_flags);
24 static int afs_launder_page(struct page *page);
25 
26 static int afs_readpages(struct file *filp, struct address_space *mapping,
27 			 struct list_head *pages, unsigned nr_pages);
28 
29 const struct file_operations afs_file_operations = {
30 	.open		= afs_open,
31 	.release	= afs_release,
32 	.llseek		= generic_file_llseek,
33 	.read		= do_sync_read,
34 	.write		= do_sync_write,
35 	.aio_read	= generic_file_aio_read,
36 	.aio_write	= afs_file_write,
37 	.mmap		= generic_file_readonly_mmap,
38 	.splice_read	= generic_file_splice_read,
39 	.fsync		= afs_fsync,
40 	.lock		= afs_lock,
41 	.flock		= afs_flock,
42 };
43 
44 const struct inode_operations afs_file_inode_operations = {
45 	.getattr	= afs_getattr,
46 	.setattr	= afs_setattr,
47 	.permission	= afs_permission,
48 };
49 
50 const struct address_space_operations afs_fs_aops = {
51 	.readpage	= afs_readpage,
52 	.readpages	= afs_readpages,
53 	.set_page_dirty	= afs_set_page_dirty,
54 	.launder_page	= afs_launder_page,
55 	.releasepage	= afs_releasepage,
56 	.invalidatepage	= afs_invalidatepage,
57 	.write_begin	= afs_write_begin,
58 	.write_end	= afs_write_end,
59 	.writepage	= afs_writepage,
60 	.writepages	= afs_writepages,
61 };
62 
63 /*
64  * open an AFS file or directory and attach a key to it
65  */
afs_open(struct inode * inode,struct file * file)66 int afs_open(struct inode *inode, struct file *file)
67 {
68 	struct afs_vnode *vnode = AFS_FS_I(inode);
69 	struct key *key;
70 	int ret;
71 
72 	_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
73 
74 	key = afs_request_key(vnode->volume->cell);
75 	if (IS_ERR(key)) {
76 		_leave(" = %ld [key]", PTR_ERR(key));
77 		return PTR_ERR(key);
78 	}
79 
80 	ret = afs_validate(vnode, key);
81 	if (ret < 0) {
82 		_leave(" = %d [val]", ret);
83 		return ret;
84 	}
85 
86 	file->private_data = key;
87 	_leave(" = 0");
88 	return 0;
89 }
90 
91 /*
92  * release an AFS file or directory and discard its key
93  */
afs_release(struct inode * inode,struct file * file)94 int afs_release(struct inode *inode, struct file *file)
95 {
96 	struct afs_vnode *vnode = AFS_FS_I(inode);
97 
98 	_enter("{%x:%u},", vnode->fid.vid, vnode->fid.vnode);
99 
100 	key_put(file->private_data);
101 	_leave(" = 0");
102 	return 0;
103 }
104 
105 #ifdef CONFIG_AFS_FSCACHE
106 /*
107  * deal with notification that a page was read from the cache
108  */
afs_file_readpage_read_complete(struct page * page,void * data,int error)109 static void afs_file_readpage_read_complete(struct page *page,
110 					    void *data,
111 					    int error)
112 {
113 	_enter("%p,%p,%d", page, data, error);
114 
115 	/* if the read completes with an error, we just unlock the page and let
116 	 * the VM reissue the readpage */
117 	if (!error)
118 		SetPageUptodate(page);
119 	unlock_page(page);
120 }
121 #endif
122 
123 /*
124  * read page from file, directory or symlink, given a key to use
125  */
afs_page_filler(void * data,struct page * page)126 int afs_page_filler(void *data, struct page *page)
127 {
128 	struct inode *inode = page->mapping->host;
129 	struct afs_vnode *vnode = AFS_FS_I(inode);
130 	struct key *key = data;
131 	size_t len;
132 	off_t offset;
133 	int ret;
134 
135 	_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
136 
137 	BUG_ON(!PageLocked(page));
138 
139 	ret = -ESTALE;
140 	if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
141 		goto error;
142 
143 	/* is it cached? */
144 #ifdef CONFIG_AFS_FSCACHE
145 	ret = fscache_read_or_alloc_page(vnode->cache,
146 					 page,
147 					 afs_file_readpage_read_complete,
148 					 NULL,
149 					 GFP_KERNEL);
150 #else
151 	ret = -ENOBUFS;
152 #endif
153 	switch (ret) {
154 		/* read BIO submitted (page in cache) */
155 	case 0:
156 		break;
157 
158 		/* page not yet cached */
159 	case -ENODATA:
160 		_debug("cache said ENODATA");
161 		goto go_on;
162 
163 		/* page will not be cached */
164 	case -ENOBUFS:
165 		_debug("cache said ENOBUFS");
166 	default:
167 	go_on:
168 		offset = page->index << PAGE_CACHE_SHIFT;
169 		len = min_t(size_t, i_size_read(inode) - offset, PAGE_SIZE);
170 
171 		/* read the contents of the file from the server into the
172 		 * page */
173 		ret = afs_vnode_fetch_data(vnode, key, offset, len, page);
174 		if (ret < 0) {
175 			if (ret == -ENOENT) {
176 				_debug("got NOENT from server"
177 				       " - marking file deleted and stale");
178 				set_bit(AFS_VNODE_DELETED, &vnode->flags);
179 				ret = -ESTALE;
180 			}
181 
182 #ifdef CONFIG_AFS_FSCACHE
183 			fscache_uncache_page(vnode->cache, page);
184 #endif
185 			BUG_ON(PageFsCache(page));
186 			goto error;
187 		}
188 
189 		SetPageUptodate(page);
190 
191 		/* send the page to the cache */
192 #ifdef CONFIG_AFS_FSCACHE
193 		if (PageFsCache(page) &&
194 		    fscache_write_page(vnode->cache, page, GFP_KERNEL) != 0) {
195 			fscache_uncache_page(vnode->cache, page);
196 			BUG_ON(PageFsCache(page));
197 		}
198 #endif
199 		unlock_page(page);
200 	}
201 
202 	_leave(" = 0");
203 	return 0;
204 
205 error:
206 	SetPageError(page);
207 	unlock_page(page);
208 	_leave(" = %d", ret);
209 	return ret;
210 }
211 
212 /*
213  * read page from file, directory or symlink, given a file to nominate the key
214  * to be used
215  */
afs_readpage(struct file * file,struct page * page)216 static int afs_readpage(struct file *file, struct page *page)
217 {
218 	struct key *key;
219 	int ret;
220 
221 	if (file) {
222 		key = file->private_data;
223 		ASSERT(key != NULL);
224 		ret = afs_page_filler(key, page);
225 	} else {
226 		struct inode *inode = page->mapping->host;
227 		key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
228 		if (IS_ERR(key)) {
229 			ret = PTR_ERR(key);
230 		} else {
231 			ret = afs_page_filler(key, page);
232 			key_put(key);
233 		}
234 	}
235 	return ret;
236 }
237 
238 /*
239  * read a set of pages
240  */
afs_readpages(struct file * file,struct address_space * mapping,struct list_head * pages,unsigned nr_pages)241 static int afs_readpages(struct file *file, struct address_space *mapping,
242 			 struct list_head *pages, unsigned nr_pages)
243 {
244 	struct key *key = file->private_data;
245 	struct afs_vnode *vnode;
246 	int ret = 0;
247 
248 	_enter("{%d},{%lu},,%d",
249 	       key_serial(key), mapping->host->i_ino, nr_pages);
250 
251 	ASSERT(key != NULL);
252 
253 	vnode = AFS_FS_I(mapping->host);
254 	if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
255 		_leave(" = -ESTALE");
256 		return -ESTALE;
257 	}
258 
259 	/* attempt to read as many of the pages as possible */
260 #ifdef CONFIG_AFS_FSCACHE
261 	ret = fscache_read_or_alloc_pages(vnode->cache,
262 					  mapping,
263 					  pages,
264 					  &nr_pages,
265 					  afs_file_readpage_read_complete,
266 					  NULL,
267 					  mapping_gfp_mask(mapping));
268 #else
269 	ret = -ENOBUFS;
270 #endif
271 
272 	switch (ret) {
273 		/* all pages are being read from the cache */
274 	case 0:
275 		BUG_ON(!list_empty(pages));
276 		BUG_ON(nr_pages != 0);
277 		_leave(" = 0 [reading all]");
278 		return 0;
279 
280 		/* there were pages that couldn't be read from the cache */
281 	case -ENODATA:
282 	case -ENOBUFS:
283 		break;
284 
285 		/* other error */
286 	default:
287 		_leave(" = %d", ret);
288 		return ret;
289 	}
290 
291 	/* load the missing pages from the network */
292 	ret = read_cache_pages(mapping, pages, afs_page_filler, key);
293 
294 	_leave(" = %d [netting]", ret);
295 	return ret;
296 }
297 
298 /*
299  * write back a dirty page
300  */
afs_launder_page(struct page * page)301 static int afs_launder_page(struct page *page)
302 {
303 	_enter("{%lu}", page->index);
304 
305 	return 0;
306 }
307 
308 /*
309  * invalidate part or all of a page
310  * - release a page and clean up its private data if offset is 0 (indicating
311  *   the entire page)
312  */
afs_invalidatepage(struct page * page,unsigned long offset)313 static void afs_invalidatepage(struct page *page, unsigned long offset)
314 {
315 	struct afs_writeback *wb = (struct afs_writeback *) page_private(page);
316 
317 	_enter("{%lu},%lu", page->index, offset);
318 
319 	BUG_ON(!PageLocked(page));
320 
321 	/* we clean up only if the entire page is being invalidated */
322 	if (offset == 0) {
323 #ifdef CONFIG_AFS_FSCACHE
324 		if (PageFsCache(page)) {
325 			struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
326 			fscache_wait_on_page_write(vnode->cache, page);
327 			fscache_uncache_page(vnode->cache, page);
328 		}
329 #endif
330 
331 		if (PagePrivate(page)) {
332 			if (wb && !PageWriteback(page)) {
333 				set_page_private(page, 0);
334 				afs_put_writeback(wb);
335 			}
336 
337 			if (!page_private(page))
338 				ClearPagePrivate(page);
339 		}
340 	}
341 
342 	_leave("");
343 }
344 
345 /*
346  * release a page and clean up its private state if it's not busy
347  * - return true if the page can now be released, false if not
348  */
afs_releasepage(struct page * page,gfp_t gfp_flags)349 static int afs_releasepage(struct page *page, gfp_t gfp_flags)
350 {
351 	struct afs_writeback *wb = (struct afs_writeback *) page_private(page);
352 	struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
353 
354 	_enter("{{%x:%u}[%lu],%lx},%x",
355 	       vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
356 	       gfp_flags);
357 
358 	/* deny if page is being written to the cache and the caller hasn't
359 	 * elected to wait */
360 #ifdef CONFIG_AFS_FSCACHE
361 	if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
362 		_leave(" = F [cache busy]");
363 		return 0;
364 	}
365 #endif
366 
367 	if (PagePrivate(page)) {
368 		if (wb) {
369 			set_page_private(page, 0);
370 			afs_put_writeback(wb);
371 		}
372 		ClearPagePrivate(page);
373 	}
374 
375 	/* indicate that the page can be released */
376 	_leave(" = T");
377 	return 1;
378 }
379