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
21static int afs_readpage(struct file *file, struct page *page);
22static void afs_invalidatepage(struct page *page, unsigned long offset);
23static int afs_releasepage(struct page *page, gfp_t gfp_flags);
24static int afs_launder_page(struct page *page);
25
26static int afs_readpages(struct file *filp, struct address_space *mapping,
27			 struct list_head *pages, unsigned nr_pages);
28
29const 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
44const struct inode_operations afs_file_inode_operations = {
45	.getattr	= afs_getattr,
46	.setattr	= afs_setattr,
47	.permission	= afs_permission,
48};
49
50const 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 */
66int 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 */
94int 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 */
109static 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 */
126int 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
205error:
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 */
216static 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 */
241static 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 (vnode->flags & AFS_VNODE_DELETED) {
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 */
301static 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 */
313static 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 */
349static 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