xref: /kernel/linux/linux-5.10/fs/9p/vfs_addr.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *  linux/fs/9p/vfs_addr.c
4 *
5 * This file contians vfs address (mmap) ops for 9P2000.
6 *
7 *  Copyright (C) 2005 by Eric Van Hensbergen <ericvh@gmail.com>
8 *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
9 */
10
11#include <linux/module.h>
12#include <linux/errno.h>
13#include <linux/fs.h>
14#include <linux/file.h>
15#include <linux/stat.h>
16#include <linux/string.h>
17#include <linux/inet.h>
18#include <linux/pagemap.h>
19#include <linux/idr.h>
20#include <linux/sched.h>
21#include <linux/uio.h>
22#include <linux/bvec.h>
23#include <net/9p/9p.h>
24#include <net/9p/client.h>
25
26#include "v9fs.h"
27#include "v9fs_vfs.h"
28#include "cache.h"
29#include "fid.h"
30
31/**
32 * v9fs_fid_readpage - read an entire page in from 9P
33 *
34 * @fid: fid being read
35 * @page: structure to page
36 *
37 */
38static int v9fs_fid_readpage(void *data, struct page *page)
39{
40	struct p9_fid *fid = data;
41	struct inode *inode = page->mapping->host;
42	struct bio_vec bvec = {.bv_page = page, .bv_len = PAGE_SIZE};
43	struct iov_iter to;
44	int retval, err;
45
46	p9_debug(P9_DEBUG_VFS, "\n");
47
48	BUG_ON(!PageLocked(page));
49
50	retval = v9fs_readpage_from_fscache(inode, page);
51	if (retval == 0)
52		return retval;
53
54	iov_iter_bvec(&to, READ, &bvec, 1, PAGE_SIZE);
55
56	retval = p9_client_read(fid, page_offset(page), &to, &err);
57	if (err) {
58		v9fs_uncache_page(inode, page);
59		retval = err;
60		goto done;
61	}
62
63	zero_user(page, retval, PAGE_SIZE - retval);
64	flush_dcache_page(page);
65	SetPageUptodate(page);
66
67	v9fs_readpage_to_fscache(inode, page);
68	retval = 0;
69
70done:
71	unlock_page(page);
72	return retval;
73}
74
75/**
76 * v9fs_vfs_readpage - read an entire page in from 9P
77 *
78 * @filp: file being read
79 * @page: structure to page
80 *
81 */
82
83static int v9fs_vfs_readpage(struct file *filp, struct page *page)
84{
85	return v9fs_fid_readpage(filp->private_data, page);
86}
87
88/**
89 * v9fs_vfs_readpages - read a set of pages from 9P
90 *
91 * @filp: file being read
92 * @mapping: the address space
93 * @pages: list of pages to read
94 * @nr_pages: count of pages to read
95 *
96 */
97
98static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
99			     struct list_head *pages, unsigned nr_pages)
100{
101	int ret = 0;
102	struct inode *inode;
103
104	inode = mapping->host;
105	p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
106
107	ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
108	if (ret == 0)
109		return ret;
110
111	ret = read_cache_pages(mapping, pages, v9fs_fid_readpage,
112			filp->private_data);
113	p9_debug(P9_DEBUG_VFS, "  = %d\n", ret);
114	return ret;
115}
116
117/**
118 * v9fs_release_page - release the private state associated with a page
119 *
120 * Returns 1 if the page can be released, false otherwise.
121 */
122
123static int v9fs_release_page(struct page *page, gfp_t gfp)
124{
125	if (PagePrivate(page))
126		return 0;
127	return v9fs_fscache_release_page(page, gfp);
128}
129
130/**
131 * v9fs_invalidate_page - Invalidate a page completely or partially
132 *
133 * @page: structure to page
134 * @offset: offset in the page
135 */
136
137static void v9fs_invalidate_page(struct page *page, unsigned int offset,
138				 unsigned int length)
139{
140	/*
141	 * If called with zero offset, we should release
142	 * the private state assocated with the page
143	 */
144	if (offset == 0 && length == PAGE_SIZE)
145		v9fs_fscache_invalidate_page(page);
146}
147
148static int v9fs_vfs_writepage_locked(struct page *page)
149{
150	struct inode *inode = page->mapping->host;
151	struct v9fs_inode *v9inode = V9FS_I(inode);
152	loff_t size = i_size_read(inode);
153	struct iov_iter from;
154	struct bio_vec bvec;
155	int err, len;
156
157	if (page->index == size >> PAGE_SHIFT)
158		len = size & ~PAGE_MASK;
159	else
160		len = PAGE_SIZE;
161
162	bvec.bv_page = page;
163	bvec.bv_offset = 0;
164	bvec.bv_len = len;
165	iov_iter_bvec(&from, WRITE, &bvec, 1, len);
166
167	/* We should have writeback_fid always set */
168	BUG_ON(!v9inode->writeback_fid);
169
170	set_page_writeback(page);
171
172	p9_client_write(v9inode->writeback_fid, page_offset(page), &from, &err);
173
174	end_page_writeback(page);
175	return err;
176}
177
178static int v9fs_vfs_writepage(struct page *page, struct writeback_control *wbc)
179{
180	int retval;
181
182	p9_debug(P9_DEBUG_VFS, "page %p\n", page);
183
184	retval = v9fs_vfs_writepage_locked(page);
185	if (retval < 0) {
186		if (retval == -EAGAIN) {
187			redirty_page_for_writepage(wbc, page);
188			retval = 0;
189		} else {
190			SetPageError(page);
191			mapping_set_error(page->mapping, retval);
192		}
193	} else
194		retval = 0;
195
196	unlock_page(page);
197	return retval;
198}
199
200/**
201 * v9fs_launder_page - Writeback a dirty page
202 * Returns 0 on success.
203 */
204
205static int v9fs_launder_page(struct page *page)
206{
207	int retval;
208	struct inode *inode = page->mapping->host;
209
210	v9fs_fscache_wait_on_page_write(inode, page);
211	if (clear_page_dirty_for_io(page)) {
212		retval = v9fs_vfs_writepage_locked(page);
213		if (retval)
214			return retval;
215	}
216	return 0;
217}
218
219/**
220 * v9fs_direct_IO - 9P address space operation for direct I/O
221 * @iocb: target I/O control block
222 *
223 * The presence of v9fs_direct_IO() in the address space ops vector
224 * allowes open() O_DIRECT flags which would have failed otherwise.
225 *
226 * In the non-cached mode, we shunt off direct read and write requests before
227 * the VFS gets them, so this method should never be called.
228 *
229 * Direct IO is not 'yet' supported in the cached mode. Hence when
230 * this routine is called through generic_file_aio_read(), the read/write fails
231 * with an error.
232 *
233 */
234static ssize_t
235v9fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
236{
237	struct file *file = iocb->ki_filp;
238	loff_t pos = iocb->ki_pos;
239	ssize_t n;
240	int err = 0;
241	if (iov_iter_rw(iter) == WRITE) {
242		n = p9_client_write(file->private_data, pos, iter, &err);
243		if (n) {
244			struct inode *inode = file_inode(file);
245			loff_t i_size = i_size_read(inode);
246			if (pos + n > i_size)
247				inode_add_bytes(inode, pos + n - i_size);
248		}
249	} else {
250		n = p9_client_read(file->private_data, pos, iter, &err);
251	}
252	return n ? n : err;
253}
254
255static int v9fs_write_begin(struct file *filp, struct address_space *mapping,
256			    loff_t pos, unsigned len, unsigned flags,
257			    struct page **pagep, void **fsdata)
258{
259	int retval = 0;
260	struct page *page;
261	struct v9fs_inode *v9inode;
262	pgoff_t index = pos >> PAGE_SHIFT;
263	struct inode *inode = mapping->host;
264
265
266	p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
267
268	v9inode = V9FS_I(inode);
269start:
270	page = grab_cache_page_write_begin(mapping, index, flags);
271	if (!page) {
272		retval = -ENOMEM;
273		goto out;
274	}
275	BUG_ON(!v9inode->writeback_fid);
276	if (PageUptodate(page))
277		goto out;
278
279	if (len == PAGE_SIZE)
280		goto out;
281
282	retval = v9fs_fid_readpage(v9inode->writeback_fid, page);
283	put_page(page);
284	if (!retval)
285		goto start;
286out:
287	*pagep = page;
288	return retval;
289}
290
291static int v9fs_write_end(struct file *filp, struct address_space *mapping,
292			  loff_t pos, unsigned len, unsigned copied,
293			  struct page *page, void *fsdata)
294{
295	loff_t last_pos = pos + copied;
296	struct inode *inode = page->mapping->host;
297
298	p9_debug(P9_DEBUG_VFS, "filp %p, mapping %p\n", filp, mapping);
299
300	if (!PageUptodate(page)) {
301		if (unlikely(copied < len)) {
302			copied = 0;
303			goto out;
304		} else if (len == PAGE_SIZE) {
305			SetPageUptodate(page);
306		}
307	}
308	/*
309	 * No need to use i_size_read() here, the i_size
310	 * cannot change under us because we hold the i_mutex.
311	 */
312	if (last_pos > inode->i_size) {
313		inode_add_bytes(inode, last_pos - inode->i_size);
314		i_size_write(inode, last_pos);
315	}
316	set_page_dirty(page);
317out:
318	unlock_page(page);
319	put_page(page);
320
321	return copied;
322}
323
324
325const struct address_space_operations v9fs_addr_operations = {
326	.readpage = v9fs_vfs_readpage,
327	.readpages = v9fs_vfs_readpages,
328	.set_page_dirty = __set_page_dirty_nobuffers,
329	.writepage = v9fs_vfs_writepage,
330	.write_begin = v9fs_write_begin,
331	.write_end = v9fs_write_end,
332	.releasepage = v9fs_release_page,
333	.invalidatepage = v9fs_invalidate_page,
334	.launder_page = v9fs_launder_page,
335	.direct_IO = v9fs_direct_IO,
336};
337