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 <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 */
52static int v9fs_fid_readpage(struct p9_fid *fid, struct page *page)
53{
54	struct inode *inode = page->mapping->host;
55	struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
56	struct iov_iter to;
57	int retval, err;
58
59	p9_debug(P9_DEBUG_VFS, "\n");
60
61	BUG_ON(!PageLocked(page));
62
63	retval = v9fs_readpage_from_fscache(inode, page);
64	if (retval == 0)
65		return retval;
66
67	iov_iter_bvec(&to, ITER_BVEC | READ, &bvec, 1, PAGE_SIZE);
68
69	retval = p9_client_read(fid, page_offset(page), &to, &err);
70	if (err) {
71		v9fs_uncache_page(inode, page);
72		retval = err;
73		goto done;
74	}
75
76	zero_user(page, retval, PAGE_SIZE - retval);
77	flush_dcache_page(page);
78	SetPageUptodate(page);
79
80	v9fs_readpage_to_fscache(inode, page);
81	retval = 0;
82
83done:
84	unlock_page(page);
85	return retval;
86}
87
88/**
89 * v9fs_vfs_readpage - read an entire page in from 9P
90 *
91 * @filp: file being read
92 * @page: structure to page
93 *
94 */
95
96static int v9fs_vfs_readpage(struct file *filp, struct page *page)
97{
98	return v9fs_fid_readpage(filp->private_data, page);
99}
100
101/**
102 * v9fs_vfs_readpages - read a set of pages from 9P
103 *
104 * @filp: file being read
105 * @mapping: the address space
106 * @pages: list of pages to read
107 * @nr_pages: count of pages to read
108 *
109 */
110
111static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
112			     struct list_head *pages, unsigned nr_pages)
113{
114	int ret = 0;
115	struct inode *inode;
116
117	inode = mapping->host;
118	p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
119
120	ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
121	if (ret == 0)
122		return ret;
123
124	ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
125	p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
126	return ret;
127}
128
129/**
130 * v9fs_release_page - release the private state associated with a page
131 *
132 * Returns 1 if the page can be released, false otherwise.
133 */
134
135static int v9fs_release_page(struct page *page, gfp_t gfp)
136{
137	if (PagePrivate(page))
138		return 0;
139	return v9fs_fscache_release_page(page, gfp);
140}
141
142/**
143 * v9fs_invalidate_page - Invalidate a page completely or partially
144 *
145 * @page: structure to page
146 * @offset: offset in the page
147 */
148
149static void v9fs_invalidate_page(struct page *page, unsigned int offset,
150				 unsigned int length)
151{
152	/*
153	 * If called with zero offset, we should release
154	 * the private state assocated with the page
155	 */
156	if (offset == 0 && length == PAGE_CACHE_SIZE)
157		v9fs_fscache_invalidate_page(page);
158}
159
160static int v9fs_vfs_writepage_locked(struct page *page)
161{
162	struct inode *inode = page->mapping->host;
163	struct v9fs_inode *v9inode = V9FS_I(inode);
164	loff_t size = i_size_read(inode);
165	struct iov_iter from;
166	struct bio_vec bvec;
167	int err, len;
168
169	if (page->index == size >> PAGE_CACHE_SHIFT)
170		len = size & ~PAGE_CACHE_MASK;
171	else
172		len = PAGE_CACHE_SIZE;
173
174	bvec.bv_page = page;
175	bvec.bv_offset = 0;
176	bvec.bv_len = len;
177	iov_iter_bvec(&from, ITER_BVEC | WRITE, &bvec, 1, len);
178
179	/* We should have writeback_fid always set */
180	BUG_ON(!v9inode->writeback_fid);
181
182	set_page_writeback(page);
183
184	p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
185
186	end_page_writeback(page);
187	return err;
188}
189
190static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
191{
192	int retval;
193
194	p9_debug(P9_DEBUG_VFS, "page %p\n", page);
195
196	retval = v9fs_vfs_writepage_locked(page);
197	if (retval < 0) {
198		if (retval == -EAGAIN) {
199			redirty_page_for_writepage(wbc, page);
200			retval = 0;
201		} else {
202			SetPageError(page);
203			mapping_set_error(page->mapping, retval);
204		}
205	} else
206		retval = 0;
207
208	unlock_page(page);
209	return retval;
210}
211
212/**
213 * v9fs_launder_page - Writeback a dirty page
214 * Returns 0 on success.
215 */
216
217static int v9fs_launder_page(struct page *page)
218{
219	int retval;
220	struct inode *inode = page->mapping->host;
221
222	v9fs_fscache_wait_on_page_write(inode, page);
223	if (clear_page_dirty_for_io(page)) {
224		retval = v9fs_vfs_writepage_locked(page);
225		if (retval)
226			return retval;
227	}
228	return 0;
229}
230
231/**
232 * v9fs_direct_IO - 9P address space operation for direct I/O
233 * @iocb: target I/O control block
234 * @pos: offset in file to begin the operation
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 */
247static ssize_t
248v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
249{
250	struct file *file = iocb->ki_filp;
251	ssize_t n;
252	int err = 0;
253	if (iov_iter_rw(iter) == WRITE) {
254		n = p9_client_write(file->private_data, pos, iter, &err);
255		if (n) {
256			struct inode *inode = file_inode(file);
257			loff_t i_size = i_size_read(inode);
258			if (pos + n > i_size)
259				inode_add_bytes(inode, pos + n - i_size);
260		}
261	} else {
262		n = p9_client_read(file->private_data, pos, iter, &err);
263	}
264	return n ? n : err;
265}
266
267static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
268			    loff_t pos, unsigned len, unsigned flags,
269			    struct page **pagep, void **fsdata)
270{
271	int retval = 0;
272	struct page *page;
273	struct v9fs_inode *v9inode;
274	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
275	struct inode *inode = mapping->host;
276
277
278	p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
279
280	v9inode = V9FS_I(inode);
281start:
282	page = grab_cache_page_write_begin(mapping, index, flags);
283	if (!page) {
284		retval = -ENOMEM;
285		goto out;
286	}
287	BUG_ON(!v9inode->writeback_fid);
288	if (PageUptodate(page))
289		goto out;
290
291	if (len == PAGE_CACHE_SIZE)
292		goto out;
293
294	retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
295	page_cache_release(page);
296	if (!retval)
297		goto start;
298out:
299	*pagep = page;
300	return retval;
301}
302
303static int v9fs_write_end(struct file *filp, struct address_space *mapping,
304			  loff_t pos, unsigned len, unsigned copied,
305			  struct page *page, void *fsdata)
306{
307	loff_t last_pos = pos + copied;
308	struct inode *inode = page->mapping->host;
309
310	p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
311
312	if (unlikely(copied < len)) {
313		/*
314		 * zero out the rest of the area
315		 */
316		unsigned from = pos & (PAGE_CACHE_SIZE - 1);
317
318		zero_user(page, from + copied, len - copied);
319		flush_dcache_page(page);
320	}
321
322	if (!PageUptodate(page))
323		SetPageUptodate(page);
324	/*
325	 * No need to use i_size_read() here, the i_size
326	 * cannot change under us because we hold the i_mutex.
327	 */
328	if (last_pos > inode->i_size) {
329		inode_add_bytes(inode, last_pos - inode->i_size);
330		i_size_write(inode, last_pos);
331	}
332	set_page_dirty(page);
333	unlock_page(page);
334	page_cache_release(page);
335
336	return copied;
337}
338
339
340const 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};
352