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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
23struct vboxsf_handle *vboxsf_create_sf_handle(struct inode *inode,
24 u64 handle, u32 access_flags)
25{
26 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
27 struct vboxsf_handle *sf_handle;
28
29 sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL);
30 if (!sf_handle)
31 return ERR_PTR(-ENOMEM);
32
33 /* the host may have given us different attr then requested */
34 sf_i->force_restat = 1;
35
36 /* init our handle struct and add it to the inode's handles list */
37 sf_handle->handle = handle;
38 sf_handle->root = VBOXSF_SBI(inode->i_sb)->root;
39 sf_handle->access_flags = access_flags;
40 kref_init(&sf_handle->refcount);
41
42 mutex_lock(&sf_i->handle_list_mutex);
43 list_add(&sf_handle->head, &sf_i->handle_list);
44 mutex_unlock(&sf_i->handle_list_mutex);
45
46 return sf_handle;
47}
48
49static int vboxsf_file_open(struct inode *inode, struct file *file)
50{
51 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
52 struct shfl_createparms params = {};
53 struct vboxsf_handle *sf_handle;
54 u32 access_flags = 0;
55 int err;
56
57 /*
58 * We check the value of params.handle afterwards to find out if
59 * the call succeeded or failed, as the API does not seem to cleanly
60 * distinguish error and informational messages.
61 *
62 * Furthermore, we must set params.handle to SHFL_HANDLE_NIL to
63 * make the shared folders host service use our mode parameter.
64 */
65 params.handle = SHFL_HANDLE_NIL;
66 if (file->f_flags & O_CREAT) {
67 params.create_flags |= SHFL_CF_ACT_CREATE_IF_NEW;
68 /*
69 * We ignore O_EXCL, as the Linux kernel seems to call create
70 * beforehand itself, so O_EXCL should always fail.
71 */
72 if (file->f_flags & O_TRUNC)
73 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
74 else
75 params.create_flags |= SHFL_CF_ACT_OPEN_IF_EXISTS;
76 } else {
77 params.create_flags |= SHFL_CF_ACT_FAIL_IF_NEW;
78 if (file->f_flags & O_TRUNC)
79 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
80 }
81
82 switch (file->f_flags & O_ACCMODE) {
83 case O_RDONLY:
84 access_flags |= SHFL_CF_ACCESS_READ;
85 break;
86
87 case O_WRONLY:
88 access_flags |= SHFL_CF_ACCESS_WRITE;
89 break;
90
91 case O_RDWR:
92 access_flags |= SHFL_CF_ACCESS_READWRITE;
93 break;
94
95 default:
96 WARN_ON(1);
97 }
98
99 if (file->f_flags & O_APPEND)
100 access_flags |= SHFL_CF_ACCESS_APPEND;
101
102 params.create_flags |= access_flags;
103 params.info.attr.mode = inode->i_mode;
104
105 err = vboxsf_create_at_dentry(file_dentry(file), ¶ms);
106 if (err == 0 && params.handle == SHFL_HANDLE_NIL)
107 err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT;
108 if (err)
109 return err;
110
111 sf_handle = vboxsf_create_sf_handle(inode, params.handle, access_flags);
112 if (IS_ERR(sf_handle)) {
113 vboxsf_close(sbi->root, params.handle);
114 return PTR_ERR(sf_handle);
115 }
116
117 file->private_data = sf_handle;
118 return 0;
119}
120
121static void vboxsf_handle_release(struct kref *refcount)
122{
123 struct vboxsf_handle *sf_handle =
124 container_of(refcount, struct vboxsf_handle, refcount);
125
126 vboxsf_close(sf_handle->root, sf_handle->handle);
127 kfree(sf_handle);
128}
129
130void vboxsf_release_sf_handle(struct inode *inode, struct vboxsf_handle *sf_handle)
131{
132 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
133
134 mutex_lock(&sf_i->handle_list_mutex);
135 list_del(&sf_handle->head);
136 mutex_unlock(&sf_i->handle_list_mutex);
137
138 kref_put(&sf_handle->refcount, vboxsf_handle_release);
139}
140
141static int vboxsf_file_release(struct inode *inode, struct file *file)
142{
143 /*
144 * When a file is closed on our (the guest) side, we want any subsequent
145 * accesses done on the host side to see all changes done from our side.
146 */
147 filemap_write_and_wait(inode->i_mapping);
148
149 vboxsf_release_sf_handle(inode, file->private_data);
150 return 0;
151}
152
153/*
154 * Write back dirty pages now, because there may not be any suitable
155 * open files later
156 */
157static void vboxsf_vma_close(struct vm_area_struct *vma)
158{
159 filemap_write_and_wait(vma->vm_file->f_mapping);
160}
161
162static const struct vm_operations_struct vboxsf_file_vm_ops = {
163 .close = vboxsf_vma_close,
164 .fault = filemap_fault,
165 .map_pages = filemap_map_pages,
166};
167
168static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)
169{
170 int err;
171
172 err = generic_file_mmap(file, vma);
173 if (!err)
174 vma->vm_ops = &vboxsf_file_vm_ops;
175
176 return err;
177}
178
179/*
180 * Note that since we are accessing files on the host's filesystem, files
181 * may always be changed underneath us by the host!
182 *
183 * The vboxsf API between the guest and the host does not offer any functions
184 * to deal with this. There is no inode-generation to check for changes, no
185 * events / callback on changes and no way to lock files.
186 *
187 * To avoid returning stale data when a file gets *opened* on our (the guest)
188 * side, we do a "stat" on the host side, then compare the mtime with the
189 * last known mtime and invalidate the page-cache if they differ.
190 * This is done from vboxsf_inode_revalidate().
191 *
192 * When reads are done through the read_iter fop, it is possible to do
193 * further cache revalidation then, there are 3 options to deal with this:
194 *
195 * 1) Rely solely on the revalidation done at open time
196 * 2) Do another "stat" and compare mtime again. Unfortunately the vboxsf
197 * host API does not allow stat on handles, so we would need to use
198 * file->f_path.dentry and the stat will then fail if the file was unlinked
199 * or renamed (and there is no thing like NFS' silly-rename). So we get:
200 * 2a) "stat" and compare mtime, on stat failure invalidate the cache
201 * 2b) "stat" and compare mtime, on stat failure do nothing
202 * 3) Simply always call invalidate_inode_pages2_range on the range of the read
203 *
204 * Currently we are keeping things KISS and using option 1. this allows
205 * directly using generic_file_read_iter without wrapping it.
206 *
207 * This means that only data written on the host side before open() on
208 * the guest side is guaranteed to be seen by the guest. If necessary
209 * we may provide other read-cache strategies in the future and make this
210 * configurable through a mount option.
211 */
212const struct file_operations vboxsf_reg_fops = {
213 .llseek = generic_file_llseek,
214 .read_iter = generic_file_read_iter,
215 .write_iter = generic_file_write_iter,
216 .mmap = vboxsf_file_mmap,
217 .open = vboxsf_file_open,
218 .release = vboxsf_file_release,
219 .fsync = noop_fsync,
220 .splice_read = generic_file_splice_read,
221};
222
223const struct inode_operations vboxsf_reg_iops = {
224 .getattr = vboxsf_getattr,
225 .setattr = vboxsf_setattr
226};
227
228static int vboxsf_readpage(struct file *file, struct page *page)
229{
230 struct vboxsf_handle *sf_handle = file->private_data;
231 loff_t off = page_offset(page);
232 u32 nread = PAGE_SIZE;
233 u8 *buf;
234 int err;
235
236 buf = kmap(page);
237
238 err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf);
239 if (err == 0) {
240 memset(&buf[nread], 0, PAGE_SIZE - nread);
241 flush_dcache_page(page);
242 SetPageUptodate(page);
243 } else {
244 SetPageError(page);
245 }
246
247 kunmap(page);
248 unlock_page(page);
249 return err;
250}
251
252static struct vboxsf_handle *vboxsf_get_write_handle(struct vboxsf_inode *sf_i)
253{
254 struct vboxsf_handle *h, *sf_handle = NULL;
255
256 mutex_lock(&sf_i->handle_list_mutex);
257 list_for_each_entry(h, &sf_i->handle_list, head) {
258 if (h->access_flags == SHFL_CF_ACCESS_WRITE ||
259 h->access_flags == SHFL_CF_ACCESS_READWRITE) {
260 kref_get(&h->refcount);
261 sf_handle = h;
262 break;
263 }
264 }
265 mutex_unlock(&sf_i->handle_list_mutex);
266
267 return sf_handle;
268}
269
270static int vboxsf_writepage(struct page *page, struct writeback_control *wbc)
271{
272 struct inode *inode = page->mapping->host;
273 struct vboxsf_inode *sf_i = VBOXSF_I(inode);
274 struct vboxsf_handle *sf_handle;
275 loff_t off = page_offset(page);
276 loff_t size = i_size_read(inode);
277 u32 nwrite = PAGE_SIZE;
278 u8 *buf;
279 int err;
280
281 if (off + PAGE_SIZE > size)
282 nwrite = size & ~PAGE_MASK;
283
284 sf_handle = vboxsf_get_write_handle(sf_i);
285 if (!sf_handle)
286 return -EBADF;
287
288 buf = kmap(page);
289 err = vboxsf_write(sf_handle->root, sf_handle->handle,
290 off, &nwrite, buf);
291 kunmap(page);
292
293 kref_put(&sf_handle->refcount, vboxsf_handle_release);
294
295 if (err == 0) {
296 ClearPageError(page);
297 /* mtime changed */
298 sf_i->force_restat = 1;
299 } else {
300 ClearPageUptodate(page);
301 }
302
303 unlock_page(page);
304 return err;
305}
306
307static int vboxsf_write_end(struct file *file, struct address_space *mapping,
308 loff_t pos, unsigned int len, unsigned int copied,
309 struct page *page, void *fsdata)
310{
311 struct inode *inode = mapping->host;
312 struct vboxsf_handle *sf_handle = file->private_data;
313 unsigned int from = pos & ~PAGE_MASK;
314 u32 nwritten = len;
315 u8 *buf;
316 int err;
317
318 /* zero the stale part of the page if we did a short copy */
319 if (!PageUptodate(page) && copied < len)
320 zero_user(page, from + copied, len - copied);
321
322 buf = kmap(page);
323 err = vboxsf_write(sf_handle->root, sf_handle->handle,
324 pos, &nwritten, buf + from);
325 kunmap(page);
326
327 if (err) {
328 nwritten = 0;
329 goto out;
330 }
331
332 /* mtime changed */
333 VBOXSF_I(inode)->force_restat = 1;
334
335 if (!PageUptodate(page) && nwritten == PAGE_SIZE)
336 SetPageUptodate(page);
337
338 pos += nwritten;
339 if (pos > inode->i_size)
340 i_size_write(inode, pos);
341
342out:
343 unlock_page(page);
344 put_page(page);
345
346 return nwritten;
347}
348
349/*
350 * Note simple_write_begin does not read the page from disk on partial writes
351 * this is ok since vboxsf_write_end only writes the written parts of the
352 * page and it does not call SetPageUptodate for partial writes.
353 */
354const struct address_space_operations vboxsf_reg_aops = {
355 .readpage = vboxsf_readpage,
356 .writepage = vboxsf_writepage,
357 .set_page_dirty = __set_page_dirty_nobuffers,
358 .write_begin = simple_write_begin,
359 .write_end = vboxsf_write_end,
360};
361
362static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,
363 struct delayed_call *done)
364{
365 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
366 struct shfl_string *path;
367 char *link;
368 int err;
369
370 if (!dentry)
371 return ERR_PTR(-ECHILD);
372
373 path = vboxsf_path_from_dentry(sbi, dentry);
374 if (IS_ERR(path))
375 return ERR_CAST(path);
376
377 link = kzalloc(PATH_MAX, GFP_KERNEL);
378 if (!link) {
379 __putname(path);
380 return ERR_PTR(-ENOMEM);
381 }
382
383 err = vboxsf_readlink(sbi->root, path, PATH_MAX, link);
384 __putname(path);
385 if (err) {
386 kfree(link);
387 return ERR_PTR(err);
388 }
389
390 set_delayed_call(done, kfree_link, link);
391 return link;
392}
393
394const struct inode_operations vboxsf_lnk_iops = {
395 .get_link = vboxsf_get_link
396};