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1// SPDX-License-Identifier: MIT
2/*
3 * VirtualBox Guest Shared Folders support: Regular file inode and file ops.
4 *
5 * Copyright (C) 2006-2018 Oracle Corporation
6 */
7
8#include <linux/mm.h>
9#include <linux/page-flags.h>
10#include <linux/pagemap.h>
11#include <linux/highmem.h>
12#include <linux/sizes.h>
13#include "vfsmod.h"
14
15struct vboxsf_handle {
16 u64 handle;
17 u32 root;
18 u32 access_flags;
19 struct kref refcount;
20 struct list_head head;
21};
22
23static int vboxsf_file_open(struct inode *inode, struct file *file)
24{
25 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
26 struct shfl_createparms params = {};
27 struct vboxsf_handle *sf_handle;
28 u32 access_flags = 0;
29 int err;
30
31 sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL);
32 if (!sf_handle)
33 return -ENOMEM;
34
35 /*
36 * We check the value of params.handle afterwards to find out if
37 * the call succeeded or failed, as the API does not seem to cleanly
38 * distinguish error and informational messages.
39 *
40 * Furthermore, we must set params.handle to SHFL_HANDLE_NIL to
41 * make the shared folders host service use our mode parameter.
42 */
43 params.handle = SHFL_HANDLE_NIL;
44 if (file->f_flags & O_CREAT) {
45 params.create_flags |= SHFL_CF_ACT_CREATE_IF_NEW;
46 /*
47 * We ignore O_EXCL, as the Linux kernel seems to call create
48 * beforehand itself, so O_EXCL should always fail.
49 */
50 if (file->f_flags & O_TRUNC)
51 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
52 else
53 params.create_flags |= SHFL_CF_ACT_OPEN_IF_EXISTS;
54 } else {
55 params.create_flags |= SHFL_CF_ACT_FAIL_IF_NEW;
56 if (file->f_flags & O_TRUNC)
57 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
58 }
59
60 switch (file->f_flags & O_ACCMODE) {
61 case O_RDONLY:
62 access_flags |= SHFL_CF_ACCESS_READ;
63 break;
64
65 case O_WRONLY:
66 access_flags |= SHFL_CF_ACCESS_WRITE;
67 break;
68
69 case O_RDWR:
70 access_flags |= SHFL_CF_ACCESS_READWRITE;
71 break;
72
73 default:
74 WARN_ON(1);
75 }
76
77 if (file->f_flags & O_APPEND)
78 access_flags |= SHFL_CF_ACCESS_APPEND;
79
80 params.create_flags |= access_flags;
81 params.info.attr.mode = inode->i_mode;
82
83 err = vboxsf_create_at_dentry(file_dentry(file), ¶ms);
84 if (err == 0 && params.handle == SHFL_HANDLE_NIL)
85 err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT;
86 if (err) {
87 kfree(sf_handle);
88 return err;
89 }
90
91 /* the host may have given us different attr then requested */
92 sf_i->force_restat = 1;
93
94 /* init our handle struct and add it to the inode's handles list */
95 sf_handle->handle = params.handle;
96 sf_handle->root = VBOXSF_SBI(inode->i_sb)->root;
97 sf_handle->access_flags = access_flags;
98 kref_init(&sf_handle->refcount);
99
100 mutex_lock(&sf_i->handle_list_mutex);
101 list_add(&sf_handle->head, &sf_i->handle_list);
102 mutex_unlock(&sf_i->handle_list_mutex);
103
104 file->private_data = sf_handle;
105 return 0;
106}
107
108static void vboxsf_handle_release(struct kref *refcount)
109{
110 struct vboxsf_handle *sf_handle =
111 container_of(refcount, struct vboxsf_handle, refcount);
112
113 vboxsf_close(sf_handle->root, sf_handle->handle);
114 kfree(sf_handle);
115}
116
117static int vboxsf_file_release(struct inode *inode, struct file *file)
118{
119 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
120 struct vboxsf_handle *sf_handle = file->private_data;
121
122 /*
123 * When a file is closed on our (the guest) side, we want any subsequent
124 * accesses done on the host side to see all changes done from our side.
125 */
126 filemap_write_and_wait(inode->i_mapping);
127
128 mutex_lock(&sf_i->handle_list_mutex);
129 list_del(&sf_handle->head);
130 mutex_unlock(&sf_i->handle_list_mutex);
131
132 kref_put(&sf_handle->refcount, vboxsf_handle_release);
133 return 0;
134}
135
136/*
137 * Write back dirty pages now, because there may not be any suitable
138 * open files later
139 */
140static void vboxsf_vma_close(struct vm_area_struct *vma)
141{
142 filemap_write_and_wait(vma->vm_file->f_mapping);
143}
144
145static const struct vm_operations_struct vboxsf_file_vm_ops = {
146 .close = vboxsf_vma_close,
147 .fault = filemap_fault,
148 .map_pages = filemap_map_pages,
149};
150
151static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)
152{
153 int err;
154
155 err = generic_file_mmap(file, vma);
156 if (!err)
157 vma->vm_ops = &vboxsf_file_vm_ops;
158
159 return err;
160}
161
162/*
163 * Note that since we are accessing files on the host's filesystem, files
164 * may always be changed underneath us by the host!
165 *
166 * The vboxsf API between the guest and the host does not offer any functions
167 * to deal with this. There is no inode-generation to check for changes, no
168 * events / callback on changes and no way to lock files.
169 *
170 * To avoid returning stale data when a file gets *opened* on our (the guest)
171 * side, we do a "stat" on the host side, then compare the mtime with the
172 * last known mtime and invalidate the page-cache if they differ.
173 * This is done from vboxsf_inode_revalidate().
174 *
175 * When reads are done through the read_iter fop, it is possible to do
176 * further cache revalidation then, there are 3 options to deal with this:
177 *
178 * 1) Rely solely on the revalidation done at open time
179 * 2) Do another "stat" and compare mtime again. Unfortunately the vboxsf
180 * host API does not allow stat on handles, so we would need to use
181 * file->f_path.dentry and the stat will then fail if the file was unlinked
182 * or renamed (and there is no thing like NFS' silly-rename). So we get:
183 * 2a) "stat" and compare mtime, on stat failure invalidate the cache
184 * 2b) "stat" and compare mtime, on stat failure do nothing
185 * 3) Simply always call invalidate_inode_pages2_range on the range of the read
186 *
187 * Currently we are keeping things KISS and using option 1. this allows
188 * directly using generic_file_read_iter without wrapping it.
189 *
190 * This means that only data written on the host side before open() on
191 * the guest side is guaranteed to be seen by the guest. If necessary
192 * we may provide other read-cache strategies in the future and make this
193 * configurable through a mount option.
194 */
195const struct file_operations vboxsf_reg_fops = {
196 .llseek = generic_file_llseek,
197 .read_iter = generic_file_read_iter,
198 .write_iter = generic_file_write_iter,
199 .mmap = vboxsf_file_mmap,
200 .open = vboxsf_file_open,
201 .release = vboxsf_file_release,
202 .fsync = noop_fsync,
203 .splice_read = generic_file_splice_read,
204};
205
206const struct inode_operations vboxsf_reg_iops = {
207 .getattr = vboxsf_getattr,
208 .setattr = vboxsf_setattr
209};
210
211static int vboxsf_readpage(struct file *file, struct page *page)
212{
213 struct vboxsf_handle *sf_handle = file->private_data;
214 loff_t off = page_offset(page);
215 u32 nread = PAGE_SIZE;
216 u8 *buf;
217 int err;
218
219 buf = kmap(page);
220
221 err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf);
222 if (err == 0) {
223 memset(&buf[nread], 0, PAGE_SIZE - nread);
224 flush_dcache_page(page);
225 SetPageUptodate(page);
226 } else {
227 SetPageError(page);
228 }
229
230 kunmap(page);
231 unlock_page(page);
232 return err;
233}
234
235static struct vboxsf_handle *vboxsf_get_write_handle(struct vboxsf_inode *sf_i)
236{
237 struct vboxsf_handle *h, *sf_handle = NULL;
238
239 mutex_lock(&sf_i->handle_list_mutex);
240 list_for_each_entry(h, &sf_i->handle_list, head) {
241 if (h->access_flags == SHFL_CF_ACCESS_WRITE ||
242 h->access_flags == SHFL_CF_ACCESS_READWRITE) {
243 kref_get(&h->refcount);
244 sf_handle = h;
245 break;
246 }
247 }
248 mutex_unlock(&sf_i->handle_list_mutex);
249
250 return sf_handle;
251}
252
253static int vboxsf_writepage(struct page *page, struct writeback_control *wbc)
254{
255 struct inode *inode = page->mapping->host;
256 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
257 struct vboxsf_handle *sf_handle;
258 loff_t off = page_offset(page);
259 loff_t size = i_size_read(inode);
260 u32 nwrite = PAGE_SIZE;
261 u8 *buf;
262 int err;
263
264 if (off + PAGE_SIZE > size)
265 nwrite = size & ~PAGE_MASK;
266
267 sf_handle = vboxsf_get_write_handle(sf_i);
268 if (!sf_handle)
269 return -EBADF;
270
271 buf = kmap(page);
272 err = vboxsf_write(sf_handle->root, sf_handle->handle,
273 off, &nwrite, buf);
274 kunmap(page);
275
276 kref_put(&sf_handle->refcount, vboxsf_handle_release);
277
278 if (err == 0) {
279 ClearPageError(page);
280 /* mtime changed */
281 sf_i->force_restat = 1;
282 } else {
283 ClearPageUptodate(page);
284 }
285
286 unlock_page(page);
287 return err;
288}
289
290static int vboxsf_write_end(struct file *file, struct address_space *mapping,
291 loff_t pos, unsigned int len, unsigned int copied,
292 struct page *page, void *fsdata)
293{
294 struct inode *inode = mapping->host;
295 struct vboxsf_handle *sf_handle = file->private_data;
296 unsigned int from = pos & ~PAGE_MASK;
297 u32 nwritten = len;
298 u8 *buf;
299 int err;
300
301 /* zero the stale part of the page if we did a short copy */
302 if (!PageUptodate(page) && copied < len)
303 zero_user(page, from + copied, len - copied);
304
305 buf = kmap(page);
306 err = vboxsf_write(sf_handle->root, sf_handle->handle,
307 pos, &nwritten, buf + from);
308 kunmap(page);
309
310 if (err) {
311 nwritten = 0;
312 goto out;
313 }
314
315 /* mtime changed */
316 VBOXSF_I(inode)->force_restat = 1;
317
318 if (!PageUptodate(page) && nwritten == PAGE_SIZE)
319 SetPageUptodate(page);
320
321 pos += nwritten;
322 if (pos > inode->i_size)
323 i_size_write(inode, pos);
324
325out:
326 unlock_page(page);
327 put_page(page);
328
329 return nwritten;
330}
331
332/*
333 * Note simple_write_begin does not read the page from disk on partial writes
334 * this is ok since vboxsf_write_end only writes the written parts of the
335 * page and it does not call SetPageUptodate for partial writes.
336 */
337const struct address_space_operations vboxsf_reg_aops = {
338 .readpage = vboxsf_readpage,
339 .writepage = vboxsf_writepage,
340 .set_page_dirty = __set_page_dirty_nobuffers,
341 .write_begin = simple_write_begin,
342 .write_end = vboxsf_write_end,
343};
344
345static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,
346 struct delayed_call *done)
347{
348 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
349 struct shfl_string *path;
350 char *link;
351 int err;
352
353 if (!dentry)
354 return ERR_PTR(-ECHILD);
355
356 path = vboxsf_path_from_dentry(sbi, dentry);
357 if (IS_ERR(path))
358 return ERR_CAST(path);
359
360 link = kzalloc(PATH_MAX, GFP_KERNEL);
361 if (!link) {
362 __putname(path);
363 return ERR_PTR(-ENOMEM);
364 }
365
366 err = vboxsf_readlink(sbi->root, path, PATH_MAX, link);
367 __putname(path);
368 if (err) {
369 kfree(link);
370 return ERR_PTR(err);
371 }
372
373 set_delayed_call(done, kfree_link, link);
374 return link;
375}
376
377const struct inode_operations vboxsf_lnk_iops = {
378 .get_link = vboxsf_get_link
379};