xref: /openbmc/linux/fs/cachefiles/io.c (revision 724ba675)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* kiocb-using read/write
3  *
4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  */
7 
8 #include <linux/mount.h>
9 #include <linux/slab.h>
10 #include <linux/file.h>
11 #include <linux/uio.h>
12 #include <linux/falloc.h>
13 #include <linux/sched/mm.h>
14 #include <trace/events/fscache.h>
15 #include "internal.h"
16 
17 struct cachefiles_kiocb {
18 	struct kiocb		iocb;
19 	refcount_t		ki_refcnt;
20 	loff_t			start;
21 	union {
22 		size_t		skipped;
23 		size_t		len;
24 	};
25 	struct cachefiles_object *object;
26 	netfs_io_terminated_t	term_func;
27 	void			*term_func_priv;
28 	bool			was_async;
29 	unsigned int		inval_counter;	/* Copy of cookie->inval_counter */
30 	u64			b_writing;
31 };
32 
33 static inline void cachefiles_put_kiocb(struct cachefiles_kiocb *ki)
34 {
35 	if (refcount_dec_and_test(&ki->ki_refcnt)) {
36 		cachefiles_put_object(ki->object, cachefiles_obj_put_ioreq);
37 		fput(ki->iocb.ki_filp);
38 		kfree(ki);
39 	}
40 }
41 
42 /*
43  * Handle completion of a read from the cache.
44  */
45 static void cachefiles_read_complete(struct kiocb *iocb, long ret)
46 {
47 	struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
48 	struct inode *inode = file_inode(ki->iocb.ki_filp);
49 
50 	_enter("%ld", ret);
51 
52 	if (ret < 0)
53 		trace_cachefiles_io_error(ki->object, inode, ret,
54 					  cachefiles_trace_read_error);
55 
56 	if (ki->term_func) {
57 		if (ret >= 0) {
58 			if (ki->object->cookie->inval_counter == ki->inval_counter)
59 				ki->skipped += ret;
60 			else
61 				ret = -ESTALE;
62 		}
63 
64 		ki->term_func(ki->term_func_priv, ret, ki->was_async);
65 	}
66 
67 	cachefiles_put_kiocb(ki);
68 }
69 
70 /*
71  * Initiate a read from the cache.
72  */
73 static int cachefiles_read(struct netfs_cache_resources *cres,
74 			   loff_t start_pos,
75 			   struct iov_iter *iter,
76 			   enum netfs_read_from_hole read_hole,
77 			   netfs_io_terminated_t term_func,
78 			   void *term_func_priv)
79 {
80 	struct cachefiles_object *object;
81 	struct cachefiles_kiocb *ki;
82 	struct file *file;
83 	unsigned int old_nofs;
84 	ssize_t ret = -ENOBUFS;
85 	size_t len = iov_iter_count(iter), skipped = 0;
86 
87 	if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
88 		goto presubmission_error;
89 
90 	fscache_count_read();
91 	object = cachefiles_cres_object(cres);
92 	file = cachefiles_cres_file(cres);
93 
94 	_enter("%pD,%li,%llx,%zx/%llx",
95 	       file, file_inode(file)->i_ino, start_pos, len,
96 	       i_size_read(file_inode(file)));
97 
98 	/* If the caller asked us to seek for data before doing the read, then
99 	 * we should do that now.  If we find a gap, we fill it with zeros.
100 	 */
101 	if (read_hole != NETFS_READ_HOLE_IGNORE) {
102 		loff_t off = start_pos, off2;
103 
104 		off2 = cachefiles_inject_read_error();
105 		if (off2 == 0)
106 			off2 = vfs_llseek(file, off, SEEK_DATA);
107 		if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) {
108 			skipped = 0;
109 			ret = off2;
110 			goto presubmission_error;
111 		}
112 
113 		if (off2 == -ENXIO || off2 >= start_pos + len) {
114 			/* The region is beyond the EOF or there's no more data
115 			 * in the region, so clear the rest of the buffer and
116 			 * return success.
117 			 */
118 			ret = -ENODATA;
119 			if (read_hole == NETFS_READ_HOLE_FAIL)
120 				goto presubmission_error;
121 
122 			iov_iter_zero(len, iter);
123 			skipped = len;
124 			ret = 0;
125 			goto presubmission_error;
126 		}
127 
128 		skipped = off2 - off;
129 		iov_iter_zero(skipped, iter);
130 	}
131 
132 	ret = -ENOMEM;
133 	ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
134 	if (!ki)
135 		goto presubmission_error;
136 
137 	refcount_set(&ki->ki_refcnt, 2);
138 	ki->iocb.ki_filp	= file;
139 	ki->iocb.ki_pos		= start_pos + skipped;
140 	ki->iocb.ki_flags	= IOCB_DIRECT;
141 	ki->iocb.ki_ioprio	= get_current_ioprio();
142 	ki->skipped		= skipped;
143 	ki->object		= object;
144 	ki->inval_counter	= cres->inval_counter;
145 	ki->term_func		= term_func;
146 	ki->term_func_priv	= term_func_priv;
147 	ki->was_async		= true;
148 
149 	if (ki->term_func)
150 		ki->iocb.ki_complete = cachefiles_read_complete;
151 
152 	get_file(ki->iocb.ki_filp);
153 	cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
154 
155 	trace_cachefiles_read(object, file_inode(file), ki->iocb.ki_pos, len - skipped);
156 	old_nofs = memalloc_nofs_save();
157 	ret = cachefiles_inject_read_error();
158 	if (ret == 0)
159 		ret = vfs_iocb_iter_read(file, &ki->iocb, iter);
160 	memalloc_nofs_restore(old_nofs);
161 	switch (ret) {
162 	case -EIOCBQUEUED:
163 		goto in_progress;
164 
165 	case -ERESTARTSYS:
166 	case -ERESTARTNOINTR:
167 	case -ERESTARTNOHAND:
168 	case -ERESTART_RESTARTBLOCK:
169 		/* There's no easy way to restart the syscall since other AIO's
170 		 * may be already running. Just fail this IO with EINTR.
171 		 */
172 		ret = -EINTR;
173 		fallthrough;
174 	default:
175 		ki->was_async = false;
176 		cachefiles_read_complete(&ki->iocb, ret);
177 		if (ret > 0)
178 			ret = 0;
179 		break;
180 	}
181 
182 in_progress:
183 	cachefiles_put_kiocb(ki);
184 	_leave(" = %zd", ret);
185 	return ret;
186 
187 presubmission_error:
188 	if (term_func)
189 		term_func(term_func_priv, ret < 0 ? ret : skipped, false);
190 	return ret;
191 }
192 
193 /*
194  * Query the occupancy of the cache in a region, returning where the next chunk
195  * of data starts and how long it is.
196  */
197 static int cachefiles_query_occupancy(struct netfs_cache_resources *cres,
198 				      loff_t start, size_t len, size_t granularity,
199 				      loff_t *_data_start, size_t *_data_len)
200 {
201 	struct cachefiles_object *object;
202 	struct file *file;
203 	loff_t off, off2;
204 
205 	*_data_start = -1;
206 	*_data_len = 0;
207 
208 	if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
209 		return -ENOBUFS;
210 
211 	object = cachefiles_cres_object(cres);
212 	file = cachefiles_cres_file(cres);
213 	granularity = max_t(size_t, object->volume->cache->bsize, granularity);
214 
215 	_enter("%pD,%li,%llx,%zx/%llx",
216 	       file, file_inode(file)->i_ino, start, len,
217 	       i_size_read(file_inode(file)));
218 
219 	off = cachefiles_inject_read_error();
220 	if (off == 0)
221 		off = vfs_llseek(file, start, SEEK_DATA);
222 	if (off == -ENXIO)
223 		return -ENODATA; /* Beyond EOF */
224 	if (off < 0 && off >= (loff_t)-MAX_ERRNO)
225 		return -ENOBUFS; /* Error. */
226 	if (round_up(off, granularity) >= start + len)
227 		return -ENODATA; /* No data in range */
228 
229 	off2 = cachefiles_inject_read_error();
230 	if (off2 == 0)
231 		off2 = vfs_llseek(file, off, SEEK_HOLE);
232 	if (off2 == -ENXIO)
233 		return -ENODATA; /* Beyond EOF */
234 	if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO)
235 		return -ENOBUFS; /* Error. */
236 
237 	/* Round away partial blocks */
238 	off = round_up(off, granularity);
239 	off2 = round_down(off2, granularity);
240 	if (off2 <= off)
241 		return -ENODATA;
242 
243 	*_data_start = off;
244 	if (off2 > start + len)
245 		*_data_len = len;
246 	else
247 		*_data_len = off2 - off;
248 	return 0;
249 }
250 
251 /*
252  * Handle completion of a write to the cache.
253  */
254 static void cachefiles_write_complete(struct kiocb *iocb, long ret)
255 {
256 	struct cachefiles_kiocb *ki = container_of(iocb, struct cachefiles_kiocb, iocb);
257 	struct cachefiles_object *object = ki->object;
258 	struct inode *inode = file_inode(ki->iocb.ki_filp);
259 
260 	_enter("%ld", ret);
261 
262 	/* Tell lockdep we inherited freeze protection from submission thread */
263 	__sb_writers_acquired(inode->i_sb, SB_FREEZE_WRITE);
264 	__sb_end_write(inode->i_sb, SB_FREEZE_WRITE);
265 
266 	if (ret < 0)
267 		trace_cachefiles_io_error(object, inode, ret,
268 					  cachefiles_trace_write_error);
269 
270 	atomic_long_sub(ki->b_writing, &object->volume->cache->b_writing);
271 	set_bit(FSCACHE_COOKIE_HAVE_DATA, &object->cookie->flags);
272 	if (ki->term_func)
273 		ki->term_func(ki->term_func_priv, ret, ki->was_async);
274 	cachefiles_put_kiocb(ki);
275 }
276 
277 /*
278  * Initiate a write to the cache.
279  */
280 int __cachefiles_write(struct cachefiles_object *object,
281 		       struct file *file,
282 		       loff_t start_pos,
283 		       struct iov_iter *iter,
284 		       netfs_io_terminated_t term_func,
285 		       void *term_func_priv)
286 {
287 	struct cachefiles_cache *cache;
288 	struct cachefiles_kiocb *ki;
289 	struct inode *inode;
290 	unsigned int old_nofs;
291 	ssize_t ret;
292 	size_t len = iov_iter_count(iter);
293 
294 	fscache_count_write();
295 	cache = object->volume->cache;
296 
297 	_enter("%pD,%li,%llx,%zx/%llx",
298 	       file, file_inode(file)->i_ino, start_pos, len,
299 	       i_size_read(file_inode(file)));
300 
301 	ki = kzalloc(sizeof(struct cachefiles_kiocb), GFP_KERNEL);
302 	if (!ki) {
303 		if (term_func)
304 			term_func(term_func_priv, -ENOMEM, false);
305 		return -ENOMEM;
306 	}
307 
308 	refcount_set(&ki->ki_refcnt, 2);
309 	ki->iocb.ki_filp	= file;
310 	ki->iocb.ki_pos		= start_pos;
311 	ki->iocb.ki_flags	= IOCB_DIRECT | IOCB_WRITE;
312 	ki->iocb.ki_ioprio	= get_current_ioprio();
313 	ki->object		= object;
314 	ki->start		= start_pos;
315 	ki->len			= len;
316 	ki->term_func		= term_func;
317 	ki->term_func_priv	= term_func_priv;
318 	ki->was_async		= true;
319 	ki->b_writing		= (len + (1 << cache->bshift) - 1) >> cache->bshift;
320 
321 	if (ki->term_func)
322 		ki->iocb.ki_complete = cachefiles_write_complete;
323 	atomic_long_add(ki->b_writing, &cache->b_writing);
324 
325 	/* Open-code file_start_write here to grab freeze protection, which
326 	 * will be released by another thread in aio_complete_rw().  Fool
327 	 * lockdep by telling it the lock got released so that it doesn't
328 	 * complain about the held lock when we return to userspace.
329 	 */
330 	inode = file_inode(file);
331 	__sb_start_write(inode->i_sb, SB_FREEZE_WRITE);
332 	__sb_writers_release(inode->i_sb, SB_FREEZE_WRITE);
333 
334 	get_file(ki->iocb.ki_filp);
335 	cachefiles_grab_object(object, cachefiles_obj_get_ioreq);
336 
337 	trace_cachefiles_write(object, inode, ki->iocb.ki_pos, len);
338 	old_nofs = memalloc_nofs_save();
339 	ret = cachefiles_inject_write_error();
340 	if (ret == 0)
341 		ret = vfs_iocb_iter_write(file, &ki->iocb, iter);
342 	memalloc_nofs_restore(old_nofs);
343 	switch (ret) {
344 	case -EIOCBQUEUED:
345 		goto in_progress;
346 
347 	case -ERESTARTSYS:
348 	case -ERESTARTNOINTR:
349 	case -ERESTARTNOHAND:
350 	case -ERESTART_RESTARTBLOCK:
351 		/* There's no easy way to restart the syscall since other AIO's
352 		 * may be already running. Just fail this IO with EINTR.
353 		 */
354 		ret = -EINTR;
355 		fallthrough;
356 	default:
357 		ki->was_async = false;
358 		cachefiles_write_complete(&ki->iocb, ret);
359 		if (ret > 0)
360 			ret = 0;
361 		break;
362 	}
363 
364 in_progress:
365 	cachefiles_put_kiocb(ki);
366 	_leave(" = %zd", ret);
367 	return ret;
368 }
369 
370 static int cachefiles_write(struct netfs_cache_resources *cres,
371 			    loff_t start_pos,
372 			    struct iov_iter *iter,
373 			    netfs_io_terminated_t term_func,
374 			    void *term_func_priv)
375 {
376 	if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE)) {
377 		if (term_func)
378 			term_func(term_func_priv, -ENOBUFS, false);
379 		return -ENOBUFS;
380 	}
381 
382 	return __cachefiles_write(cachefiles_cres_object(cres),
383 				  cachefiles_cres_file(cres),
384 				  start_pos, iter,
385 				  term_func, term_func_priv);
386 }
387 
388 static inline enum netfs_io_source
389 cachefiles_do_prepare_read(struct netfs_cache_resources *cres,
390 			   loff_t start, size_t *_len, loff_t i_size,
391 			   unsigned long *_flags, ino_t netfs_ino)
392 {
393 	enum cachefiles_prepare_read_trace why;
394 	struct cachefiles_object *object = NULL;
395 	struct cachefiles_cache *cache;
396 	struct fscache_cookie *cookie = fscache_cres_cookie(cres);
397 	const struct cred *saved_cred;
398 	struct file *file = cachefiles_cres_file(cres);
399 	enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER;
400 	size_t len = *_len;
401 	loff_t off, to;
402 	ino_t ino = file ? file_inode(file)->i_ino : 0;
403 	int rc;
404 
405 	_enter("%zx @%llx/%llx", len, start, i_size);
406 
407 	if (start >= i_size) {
408 		ret = NETFS_FILL_WITH_ZEROES;
409 		why = cachefiles_trace_read_after_eof;
410 		goto out_no_object;
411 	}
412 
413 	if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) {
414 		__set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
415 		why = cachefiles_trace_read_no_data;
416 		if (!test_bit(NETFS_SREQ_ONDEMAND, _flags))
417 			goto out_no_object;
418 	}
419 
420 	/* The object and the file may be being created in the background. */
421 	if (!file) {
422 		why = cachefiles_trace_read_no_file;
423 		if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
424 			goto out_no_object;
425 		file = cachefiles_cres_file(cres);
426 		if (!file)
427 			goto out_no_object;
428 		ino = file_inode(file)->i_ino;
429 	}
430 
431 	object = cachefiles_cres_object(cres);
432 	cache = object->volume->cache;
433 	cachefiles_begin_secure(cache, &saved_cred);
434 retry:
435 	off = cachefiles_inject_read_error();
436 	if (off == 0)
437 		off = vfs_llseek(file, start, SEEK_DATA);
438 	if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
439 		if (off == (loff_t)-ENXIO) {
440 			why = cachefiles_trace_read_seek_nxio;
441 			goto download_and_store;
442 		}
443 		trace_cachefiles_io_error(object, file_inode(file), off,
444 					  cachefiles_trace_seek_error);
445 		why = cachefiles_trace_read_seek_error;
446 		goto out;
447 	}
448 
449 	if (off >= start + len) {
450 		why = cachefiles_trace_read_found_hole;
451 		goto download_and_store;
452 	}
453 
454 	if (off > start) {
455 		off = round_up(off, cache->bsize);
456 		len = off - start;
457 		*_len = len;
458 		why = cachefiles_trace_read_found_part;
459 		goto download_and_store;
460 	}
461 
462 	to = cachefiles_inject_read_error();
463 	if (to == 0)
464 		to = vfs_llseek(file, start, SEEK_HOLE);
465 	if (to < 0 && to >= (loff_t)-MAX_ERRNO) {
466 		trace_cachefiles_io_error(object, file_inode(file), to,
467 					  cachefiles_trace_seek_error);
468 		why = cachefiles_trace_read_seek_error;
469 		goto out;
470 	}
471 
472 	if (to < start + len) {
473 		if (start + len >= i_size)
474 			to = round_up(to, cache->bsize);
475 		else
476 			to = round_down(to, cache->bsize);
477 		len = to - start;
478 		*_len = len;
479 	}
480 
481 	why = cachefiles_trace_read_have_data;
482 	ret = NETFS_READ_FROM_CACHE;
483 	goto out;
484 
485 download_and_store:
486 	__set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
487 	if (test_bit(NETFS_SREQ_ONDEMAND, _flags)) {
488 		rc = cachefiles_ondemand_read(object, start, len);
489 		if (!rc) {
490 			__clear_bit(NETFS_SREQ_ONDEMAND, _flags);
491 			goto retry;
492 		}
493 		ret = NETFS_INVALID_READ;
494 	}
495 out:
496 	cachefiles_end_secure(cache, saved_cred);
497 out_no_object:
498 	trace_cachefiles_prep_read(object, start, len, *_flags, ret, why, ino, netfs_ino);
499 	return ret;
500 }
501 
502 /*
503  * Prepare a read operation, shortening it to a cached/uncached
504  * boundary as appropriate.
505  */
506 static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
507 						    loff_t i_size)
508 {
509 	return cachefiles_do_prepare_read(&subreq->rreq->cache_resources,
510 					  subreq->start, &subreq->len, i_size,
511 					  &subreq->flags, subreq->rreq->inode->i_ino);
512 }
513 
514 /*
515  * Prepare an on-demand read operation, shortening it to a cached/uncached
516  * boundary as appropriate.
517  */
518 static enum netfs_io_source
519 cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
520 				 loff_t start, size_t *_len, loff_t i_size,
521 				 unsigned long *_flags, ino_t ino)
522 {
523 	return cachefiles_do_prepare_read(cres, start, _len, i_size, _flags, ino);
524 }
525 
526 /*
527  * Prepare for a write to occur.
528  */
529 int __cachefiles_prepare_write(struct cachefiles_object *object,
530 			       struct file *file,
531 			       loff_t *_start, size_t *_len,
532 			       bool no_space_allocated_yet)
533 {
534 	struct cachefiles_cache *cache = object->volume->cache;
535 	loff_t start = *_start, pos;
536 	size_t len = *_len, down;
537 	int ret;
538 
539 	/* Round to DIO size */
540 	down = start - round_down(start, PAGE_SIZE);
541 	*_start = start - down;
542 	*_len = round_up(down + len, PAGE_SIZE);
543 
544 	/* We need to work out whether there's sufficient disk space to perform
545 	 * the write - but we can skip that check if we have space already
546 	 * allocated.
547 	 */
548 	if (no_space_allocated_yet)
549 		goto check_space;
550 
551 	pos = cachefiles_inject_read_error();
552 	if (pos == 0)
553 		pos = vfs_llseek(file, *_start, SEEK_DATA);
554 	if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
555 		if (pos == -ENXIO)
556 			goto check_space; /* Unallocated tail */
557 		trace_cachefiles_io_error(object, file_inode(file), pos,
558 					  cachefiles_trace_seek_error);
559 		return pos;
560 	}
561 	if ((u64)pos >= (u64)*_start + *_len)
562 		goto check_space; /* Unallocated region */
563 
564 	/* We have a block that's at least partially filled - if we're low on
565 	 * space, we need to see if it's fully allocated.  If it's not, we may
566 	 * want to cull it.
567 	 */
568 	if (cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
569 				 cachefiles_has_space_check) == 0)
570 		return 0; /* Enough space to simply overwrite the whole block */
571 
572 	pos = cachefiles_inject_read_error();
573 	if (pos == 0)
574 		pos = vfs_llseek(file, *_start, SEEK_HOLE);
575 	if (pos < 0 && pos >= (loff_t)-MAX_ERRNO) {
576 		trace_cachefiles_io_error(object, file_inode(file), pos,
577 					  cachefiles_trace_seek_error);
578 		return pos;
579 	}
580 	if ((u64)pos >= (u64)*_start + *_len)
581 		return 0; /* Fully allocated */
582 
583 	/* Partially allocated, but insufficient space: cull. */
584 	fscache_count_no_write_space();
585 	ret = cachefiles_inject_remove_error();
586 	if (ret == 0)
587 		ret = vfs_fallocate(file, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
588 				    *_start, *_len);
589 	if (ret < 0) {
590 		trace_cachefiles_io_error(object, file_inode(file), ret,
591 					  cachefiles_trace_fallocate_error);
592 		cachefiles_io_error_obj(object,
593 					"CacheFiles: fallocate failed (%d)\n", ret);
594 		ret = -EIO;
595 	}
596 
597 	return ret;
598 
599 check_space:
600 	return cachefiles_has_space(cache, 0, *_len / PAGE_SIZE,
601 				    cachefiles_has_space_for_write);
602 }
603 
604 static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
605 				    loff_t *_start, size_t *_len, loff_t i_size,
606 				    bool no_space_allocated_yet)
607 {
608 	struct cachefiles_object *object = cachefiles_cres_object(cres);
609 	struct cachefiles_cache *cache = object->volume->cache;
610 	const struct cred *saved_cred;
611 	int ret;
612 
613 	if (!cachefiles_cres_file(cres)) {
614 		if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE))
615 			return -ENOBUFS;
616 		if (!cachefiles_cres_file(cres))
617 			return -ENOBUFS;
618 	}
619 
620 	cachefiles_begin_secure(cache, &saved_cred);
621 	ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
622 					 _start, _len,
623 					 no_space_allocated_yet);
624 	cachefiles_end_secure(cache, saved_cred);
625 	return ret;
626 }
627 
628 /*
629  * Clean up an operation.
630  */
631 static void cachefiles_end_operation(struct netfs_cache_resources *cres)
632 {
633 	struct file *file = cachefiles_cres_file(cres);
634 
635 	if (file)
636 		fput(file);
637 	fscache_end_cookie_access(fscache_cres_cookie(cres), fscache_access_io_end);
638 }
639 
640 static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
641 	.end_operation		= cachefiles_end_operation,
642 	.read			= cachefiles_read,
643 	.write			= cachefiles_write,
644 	.prepare_read		= cachefiles_prepare_read,
645 	.prepare_write		= cachefiles_prepare_write,
646 	.prepare_ondemand_read	= cachefiles_prepare_ondemand_read,
647 	.query_occupancy	= cachefiles_query_occupancy,
648 };
649 
650 /*
651  * Open the cache file when beginning a cache operation.
652  */
653 bool cachefiles_begin_operation(struct netfs_cache_resources *cres,
654 				enum fscache_want_state want_state)
655 {
656 	struct cachefiles_object *object = cachefiles_cres_object(cres);
657 
658 	if (!cachefiles_cres_file(cres)) {
659 		cres->ops = &cachefiles_netfs_cache_ops;
660 		if (object->file) {
661 			spin_lock(&object->lock);
662 			if (!cres->cache_priv2 && object->file)
663 				cres->cache_priv2 = get_file(object->file);
664 			spin_unlock(&object->lock);
665 		}
666 	}
667 
668 	if (!cachefiles_cres_file(cres) && want_state != FSCACHE_WANT_PARAMS) {
669 		pr_err("failed to get cres->file\n");
670 		return false;
671 	}
672 
673 	return true;
674 }
675