1 // SPDX-License-Identifier: GPL-2.0-only 1
2 /*
3 * Common helpers for stackable filesystems an
4 *
5 * Forked from fs/overlayfs/file.c.
6 *
7 * Copyright (C) 2017 Red Hat, Inc.
8 * Copyright (C) 2023 CTERA Networks.
9 */
10
11 #include <linux/fs.h>
12 #include <linux/backing-file.h>
13 #include <linux/splice.h>
14 #include <linux/mm.h>
15
16 #include "internal.h"
17
18 /**
19 * backing_file_open - open a backing file for
20 * @user_path: path that the user reuqested t
21 * @flags: open flags
22 * @real_path: path of the backing file
23 * @cred: credentials for open
24 *
25 * Open a backing file for a stackable filesys
26 * @user_path may be on the stackable filesyst
27 * underlying filesystem. In this case, we wa
28 * @user_path of the stackable filesystem. Thi
29 * returned file into a container structure th
30 * file's path, which can be retrieved using b
31 */
32 struct file *backing_file_open(const struct pa
33 const struct pa
34 const struct cr
35 {
36 struct file *f;
37 int error;
38
39 f = alloc_empty_backing_file(flags, cr
40 if (IS_ERR(f))
41 return f;
42
43 path_get(user_path);
44 *backing_file_user_path(f) = *user_pat
45 error = vfs_open(real_path, f);
46 if (error) {
47 fput(f);
48 f = ERR_PTR(error);
49 }
50
51 return f;
52 }
53 EXPORT_SYMBOL_GPL(backing_file_open);
54
55 struct file *backing_tmpfile_open(const struct
56 const struct
57 umode_t mode
58 {
59 struct mnt_idmap *real_idmap = mnt_idm
60 struct file *f;
61 int error;
62
63 f = alloc_empty_backing_file(flags, cr
64 if (IS_ERR(f))
65 return f;
66
67 path_get(user_path);
68 *backing_file_user_path(f) = *user_pat
69 error = vfs_tmpfile(real_idmap, real_p
70 if (error) {
71 fput(f);
72 f = ERR_PTR(error);
73 }
74 return f;
75 }
76 EXPORT_SYMBOL(backing_tmpfile_open);
77
78 struct backing_aio {
79 struct kiocb iocb;
80 refcount_t ref;
81 struct kiocb *orig_iocb;
82 /* used for aio completion */
83 void (*end_write)(struct file *);
84 struct work_struct work;
85 long res;
86 };
87
88 static struct kmem_cache *backing_aio_cachep;
89
90 #define BACKING_IOCB_MASK \
91 (IOCB_NOWAIT | IOCB_HIPRI | IOCB_DSYNC
92
93 static rwf_t iocb_to_rw_flags(int flags)
94 {
95 return (__force rwf_t)(flags & BACKING
96 }
97
98 static void backing_aio_put(struct backing_aio
99 {
100 if (refcount_dec_and_test(&aio->ref))
101 fput(aio->iocb.ki_filp);
102 kmem_cache_free(backing_aio_ca
103 }
104 }
105
106 static void backing_aio_cleanup(struct backing
107 {
108 struct kiocb *iocb = &aio->iocb;
109 struct kiocb *orig_iocb = aio->orig_io
110
111 if (aio->end_write)
112 aio->end_write(orig_iocb->ki_f
113
114 orig_iocb->ki_pos = iocb->ki_pos;
115 backing_aio_put(aio);
116 }
117
118 static void backing_aio_rw_complete(struct kio
119 {
120 struct backing_aio *aio = container_of
121 struct kiocb *orig_iocb = aio->orig_io
122
123 if (iocb->ki_flags & IOCB_WRITE)
124 kiocb_end_write(iocb);
125
126 backing_aio_cleanup(aio, res);
127 orig_iocb->ki_complete(orig_iocb, res)
128 }
129
130 static void backing_aio_complete_work(struct w
131 {
132 struct backing_aio *aio = container_of
133
134 backing_aio_rw_complete(&aio->iocb, ai
135 }
136
137 static void backing_aio_queue_completion(struc
138 {
139 struct backing_aio *aio = container_of
140
141 /*
142 * Punt to a work queue to serialize u
143 */
144 aio->res = res;
145 INIT_WORK(&aio->work, backing_aio_comp
146 queue_work(file_inode(aio->orig_iocb->
147 &aio->work);
148 }
149
150 static int backing_aio_init_wq(struct kiocb *i
151 {
152 struct super_block *sb = file_inode(io
153
154 if (sb->s_dio_done_wq)
155 return 0;
156
157 return sb_init_dio_done_wq(sb);
158 }
159
160
161 ssize_t backing_file_read_iter(struct file *fi
162 struct kiocb *i
163 struct backing_
164 {
165 struct backing_aio *aio = NULL;
166 const struct cred *old_cred;
167 ssize_t ret;
168
169 if (WARN_ON_ONCE(!(file->f_mode & FMOD
170 return -EIO;
171
172 if (!iov_iter_count(iter))
173 return 0;
174
175 if (iocb->ki_flags & IOCB_DIRECT &&
176 !(file->f_mode & FMODE_CAN_ODIRECT
177 return -EINVAL;
178
179 old_cred = override_creds(ctx->cred);
180 if (is_sync_kiocb(iocb)) {
181 rwf_t rwf = iocb_to_rw_flags(f
182
183 ret = vfs_iter_read(file, iter
184 } else {
185 ret = -ENOMEM;
186 aio = kmem_cache_zalloc(backin
187 if (!aio)
188 goto out;
189
190 aio->orig_iocb = iocb;
191 kiocb_clone(&aio->iocb, iocb,
192 aio->iocb.ki_complete = backin
193 refcount_set(&aio->ref, 2);
194 ret = vfs_iocb_iter_read(file,
195 backing_aio_put(aio);
196 if (ret != -EIOCBQUEUED)
197 backing_aio_cleanup(ai
198 }
199 out:
200 revert_creds(old_cred);
201
202 if (ctx->accessed)
203 ctx->accessed(ctx->user_file);
204
205 return ret;
206 }
207 EXPORT_SYMBOL_GPL(backing_file_read_iter);
208
209 ssize_t backing_file_write_iter(struct file *f
210 struct kiocb *
211 struct backing
212 {
213 const struct cred *old_cred;
214 ssize_t ret;
215
216 if (WARN_ON_ONCE(!(file->f_mode & FMOD
217 return -EIO;
218
219 if (!iov_iter_count(iter))
220 return 0;
221
222 ret = file_remove_privs(ctx->user_file
223 if (ret)
224 return ret;
225
226 if (iocb->ki_flags & IOCB_DIRECT &&
227 !(file->f_mode & FMODE_CAN_ODIRECT
228 return -EINVAL;
229
230 /*
231 * Stacked filesystems don't support d
232 * this property in case it is set by
233 */
234 flags &= ~IOCB_DIO_CALLER_COMP;
235
236 old_cred = override_creds(ctx->cred);
237 if (is_sync_kiocb(iocb)) {
238 rwf_t rwf = iocb_to_rw_flags(f
239
240 ret = vfs_iter_write(file, ite
241 if (ctx->end_write)
242 ctx->end_write(ctx->us
243 } else {
244 struct backing_aio *aio;
245
246 ret = backing_aio_init_wq(iocb
247 if (ret)
248 goto out;
249
250 ret = -ENOMEM;
251 aio = kmem_cache_zalloc(backin
252 if (!aio)
253 goto out;
254
255 aio->orig_iocb = iocb;
256 aio->end_write = ctx->end_writ
257 kiocb_clone(&aio->iocb, iocb,
258 aio->iocb.ki_flags = flags;
259 aio->iocb.ki_complete = backin
260 refcount_set(&aio->ref, 2);
261 ret = vfs_iocb_iter_write(file
262 backing_aio_put(aio);
263 if (ret != -EIOCBQUEUED)
264 backing_aio_cleanup(ai
265 }
266 out:
267 revert_creds(old_cred);
268
269 return ret;
270 }
271 EXPORT_SYMBOL_GPL(backing_file_write_iter);
272
273 ssize_t backing_file_splice_read(struct file *
274 struct pipe_i
275 unsigned int
276 struct backin
277 {
278 const struct cred *old_cred;
279 ssize_t ret;
280
281 if (WARN_ON_ONCE(!(in->f_mode & FMODE_
282 return -EIO;
283
284 old_cred = override_creds(ctx->cred);
285 ret = vfs_splice_read(in, ppos, pipe,
286 revert_creds(old_cred);
287
288 if (ctx->accessed)
289 ctx->accessed(ctx->user_file);
290
291 return ret;
292 }
293 EXPORT_SYMBOL_GPL(backing_file_splice_read);
294
295 ssize_t backing_file_splice_write(struct pipe_
296 struct file
297 unsigned int
298 struct backi
299 {
300 const struct cred *old_cred;
301 ssize_t ret;
302
303 if (WARN_ON_ONCE(!(out->f_mode & FMODE
304 return -EIO;
305
306 if (!out->f_op->splice_write)
307 return -EINVAL;
308
309 ret = file_remove_privs(ctx->user_file
310 if (ret)
311 return ret;
312
313 old_cred = override_creds(ctx->cred);
314 file_start_write(out);
315 ret = out->f_op->splice_write(pipe, ou
316 file_end_write(out);
317 revert_creds(old_cred);
318
319 if (ctx->end_write)
320 ctx->end_write(ctx->user_file)
321
322 return ret;
323 }
324 EXPORT_SYMBOL_GPL(backing_file_splice_write);
325
326 int backing_file_mmap(struct file *file, struc
327 struct backing_file_ctx
328 {
329 const struct cred *old_cred;
330 int ret;
331
332 if (WARN_ON_ONCE(!(file->f_mode & FMOD
333 WARN_ON_ONCE(ctx->user_file != vma
334 return -EIO;
335
336 if (!file->f_op->mmap)
337 return -ENODEV;
338
339 vma_set_file(vma, file);
340
341 old_cred = override_creds(ctx->cred);
342 ret = call_mmap(vma->vm_file, vma);
343 revert_creds(old_cred);
344
345 if (ctx->accessed)
346 ctx->accessed(ctx->user_file);
347
348 return ret;
349 }
350 EXPORT_SYMBOL_GPL(backing_file_mmap);
351
352 static int __init backing_aio_init(void)
353 {
354 backing_aio_cachep = KMEM_CACHE(backin
355 if (!backing_aio_cachep)
356 return -ENOMEM;
357
358 return 0;
359 }
360 fs_initcall(backing_aio_init);
361
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