1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Network filesystem high-level buffered read support.
3 *
4 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/export.h>
9 #include <linux/task_io_accounting_ops.h>
10 #include "internal.h"
11
netfs_cache_expand_readahead(struct netfs_io_request * rreq,unsigned long long * _start,unsigned long long * _len,unsigned long long i_size)12 static void netfs_cache_expand_readahead(struct netfs_io_request *rreq,
13 unsigned long long *_start,
14 unsigned long long *_len,
15 unsigned long long i_size)
16 {
17 struct netfs_cache_resources *cres = &rreq->cache_resources;
18
19 if (cres->ops && cres->ops->expand_readahead)
20 cres->ops->expand_readahead(cres, _start, _len, i_size);
21 }
22
netfs_rreq_expand(struct netfs_io_request * rreq,struct readahead_control * ractl)23 static void netfs_rreq_expand(struct netfs_io_request *rreq,
24 struct readahead_control *ractl)
25 {
26 /* Give the cache a chance to change the request parameters. The
27 * resultant request must contain the original region.
28 */
29 netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size);
30
31 /* Give the netfs a chance to change the request parameters. The
32 * resultant request must contain the original region.
33 */
34 if (rreq->netfs_ops->expand_readahead)
35 rreq->netfs_ops->expand_readahead(rreq);
36
37 /* Expand the request if the cache wants it to start earlier. Note
38 * that the expansion may get further extended if the VM wishes to
39 * insert THPs and the preferred start and/or end wind up in the middle
40 * of THPs.
41 *
42 * If this is the case, however, the THP size should be an integer
43 * multiple of the cache granule size, so we get a whole number of
44 * granules to deal with.
45 */
46 if (rreq->start != readahead_pos(ractl) ||
47 rreq->len != readahead_length(ractl)) {
48 readahead_expand(ractl, rreq->start, rreq->len);
49 rreq->start = readahead_pos(ractl);
50 rreq->len = readahead_length(ractl);
51
52 trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
53 netfs_read_trace_expanded);
54 }
55 }
56
57 /*
58 * Begin an operation, and fetch the stored zero point value from the cookie if
59 * available.
60 */
netfs_begin_cache_read(struct netfs_io_request * rreq,struct netfs_inode * ctx)61 static int netfs_begin_cache_read(struct netfs_io_request *rreq, struct netfs_inode *ctx)
62 {
63 return fscache_begin_read_operation(&rreq->cache_resources, netfs_i_cookie(ctx));
64 }
65
66 /*
67 * netfs_prepare_read_iterator - Prepare the subreq iterator for I/O
68 * @subreq: The subrequest to be set up
69 *
70 * Prepare the I/O iterator representing the read buffer on a subrequest for
71 * the filesystem to use for I/O (it can be passed directly to a socket). This
72 * is intended to be called from the ->issue_read() method once the filesystem
73 * has trimmed the request to the size it wants.
74 *
75 * Returns the limited size if successful and -ENOMEM if insufficient memory
76 * available.
77 *
78 * [!] NOTE: This must be run in the same thread as ->issue_read() was called
79 * in as we access the readahead_control struct.
80 */
netfs_prepare_read_iterator(struct netfs_io_subrequest * subreq)81 static ssize_t netfs_prepare_read_iterator(struct netfs_io_subrequest *subreq)
82 {
83 struct netfs_io_request *rreq = subreq->rreq;
84 size_t rsize = subreq->len;
85
86 if (subreq->source == NETFS_DOWNLOAD_FROM_SERVER)
87 rsize = umin(rsize, rreq->io_streams[0].sreq_max_len);
88
89 if (rreq->ractl) {
90 /* If we don't have sufficient folios in the rolling buffer,
91 * extract a folioq's worth from the readahead region at a time
92 * into the buffer. Note that this acquires a ref on each page
93 * that we will need to release later - but we don't want to do
94 * that until after we've started the I/O.
95 */
96 struct folio_batch put_batch;
97
98 folio_batch_init(&put_batch);
99 while (rreq->submitted < subreq->start + rsize) {
100 ssize_t added;
101
102 added = rolling_buffer_load_from_ra(&rreq->buffer, rreq->ractl,
103 &put_batch);
104 if (added < 0)
105 return added;
106 rreq->submitted += added;
107 }
108 folio_batch_release(&put_batch);
109 }
110
111 subreq->len = rsize;
112 if (unlikely(rreq->io_streams[0].sreq_max_segs)) {
113 size_t limit = netfs_limit_iter(&rreq->buffer.iter, 0, rsize,
114 rreq->io_streams[0].sreq_max_segs);
115
116 if (limit < rsize) {
117 subreq->len = limit;
118 trace_netfs_sreq(subreq, netfs_sreq_trace_limited);
119 }
120 }
121
122 subreq->io_iter = rreq->buffer.iter;
123
124 iov_iter_truncate(&subreq->io_iter, subreq->len);
125 rolling_buffer_advance(&rreq->buffer, subreq->len);
126 return subreq->len;
127 }
128
netfs_cache_prepare_read(struct netfs_io_request * rreq,struct netfs_io_subrequest * subreq,loff_t i_size)129 static enum netfs_io_source netfs_cache_prepare_read(struct netfs_io_request *rreq,
130 struct netfs_io_subrequest *subreq,
131 loff_t i_size)
132 {
133 struct netfs_cache_resources *cres = &rreq->cache_resources;
134 enum netfs_io_source source;
135
136 if (!cres->ops)
137 return NETFS_DOWNLOAD_FROM_SERVER;
138 source = cres->ops->prepare_read(subreq, i_size);
139 trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
140 return source;
141
142 }
143
144 /*
145 * Issue a read against the cache.
146 * - Eats the caller's ref on subreq.
147 */
netfs_read_cache_to_pagecache(struct netfs_io_request * rreq,struct netfs_io_subrequest * subreq)148 static void netfs_read_cache_to_pagecache(struct netfs_io_request *rreq,
149 struct netfs_io_subrequest *subreq)
150 {
151 struct netfs_cache_resources *cres = &rreq->cache_resources;
152
153 netfs_stat(&netfs_n_rh_read);
154 cres->ops->read(cres, subreq->start, &subreq->io_iter, NETFS_READ_HOLE_IGNORE,
155 netfs_cache_read_terminated, subreq);
156 }
157
netfs_queue_read(struct netfs_io_request * rreq,struct netfs_io_subrequest * subreq,bool last_subreq)158 static void netfs_queue_read(struct netfs_io_request *rreq,
159 struct netfs_io_subrequest *subreq,
160 bool last_subreq)
161 {
162 struct netfs_io_stream *stream = &rreq->io_streams[0];
163
164 __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
165
166 /* We add to the end of the list whilst the collector may be walking
167 * the list. The collector only goes nextwards and uses the lock to
168 * remove entries off of the front.
169 */
170 spin_lock(&rreq->lock);
171 list_add_tail(&subreq->rreq_link, &stream->subrequests);
172 if (list_is_first(&subreq->rreq_link, &stream->subrequests)) {
173 stream->front = subreq;
174 if (!stream->active) {
175 stream->collected_to = stream->front->start;
176 /* Store list pointers before active flag */
177 smp_store_release(&stream->active, true);
178 }
179 }
180
181 if (last_subreq) {
182 smp_wmb(); /* Write lists before ALL_QUEUED. */
183 set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags);
184 }
185
186 spin_unlock(&rreq->lock);
187 }
188
netfs_issue_read(struct netfs_io_request * rreq,struct netfs_io_subrequest * subreq)189 static void netfs_issue_read(struct netfs_io_request *rreq,
190 struct netfs_io_subrequest *subreq)
191 {
192 switch (subreq->source) {
193 case NETFS_DOWNLOAD_FROM_SERVER:
194 rreq->netfs_ops->issue_read(subreq);
195 break;
196 case NETFS_READ_FROM_CACHE:
197 netfs_read_cache_to_pagecache(rreq, subreq);
198 break;
199 default:
200 __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
201 subreq->error = 0;
202 iov_iter_zero(subreq->len, &subreq->io_iter);
203 subreq->transferred = subreq->len;
204 netfs_read_subreq_terminated(subreq);
205 break;
206 }
207 }
208
209 /*
210 * Perform a read to the pagecache from a series of sources of different types,
211 * slicing up the region to be read according to available cache blocks and
212 * network rsize.
213 */
netfs_read_to_pagecache(struct netfs_io_request * rreq)214 static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
215 {
216 struct netfs_inode *ictx = netfs_inode(rreq->inode);
217 unsigned long long start = rreq->start;
218 ssize_t size = rreq->len;
219 int ret = 0;
220
221 do {
222 struct netfs_io_subrequest *subreq;
223 enum netfs_io_source source = NETFS_SOURCE_UNKNOWN;
224 ssize_t slice;
225
226 subreq = netfs_alloc_subrequest(rreq);
227 if (!subreq) {
228 ret = -ENOMEM;
229 break;
230 }
231
232 subreq->start = start;
233 subreq->len = size;
234
235 source = netfs_cache_prepare_read(rreq, subreq, rreq->i_size);
236 subreq->source = source;
237 if (source == NETFS_DOWNLOAD_FROM_SERVER) {
238 unsigned long long zp = umin(ictx->zero_point, rreq->i_size);
239 size_t len = subreq->len;
240
241 if (unlikely(rreq->origin == NETFS_READ_SINGLE))
242 zp = rreq->i_size;
243 if (subreq->start >= zp) {
244 subreq->source = source = NETFS_FILL_WITH_ZEROES;
245 goto fill_with_zeroes;
246 }
247
248 if (len > zp - subreq->start)
249 len = zp - subreq->start;
250 if (len == 0) {
251 pr_err("ZERO-LEN READ: R=%08x[%x] l=%zx/%zx s=%llx z=%llx i=%llx",
252 rreq->debug_id, subreq->debug_index,
253 subreq->len, size,
254 subreq->start, ictx->zero_point, rreq->i_size);
255 break;
256 }
257 subreq->len = len;
258
259 netfs_stat(&netfs_n_rh_download);
260 if (rreq->netfs_ops->prepare_read) {
261 ret = rreq->netfs_ops->prepare_read(subreq);
262 if (ret < 0) {
263 subreq->error = ret;
264 /* Not queued - release both refs. */
265 netfs_put_subrequest(subreq, false,
266 netfs_sreq_trace_put_cancel);
267 netfs_put_subrequest(subreq, false,
268 netfs_sreq_trace_put_cancel);
269 break;
270 }
271 trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
272 }
273 goto issue;
274 }
275
276 fill_with_zeroes:
277 if (source == NETFS_FILL_WITH_ZEROES) {
278 subreq->source = NETFS_FILL_WITH_ZEROES;
279 trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
280 netfs_stat(&netfs_n_rh_zero);
281 goto issue;
282 }
283
284 if (source == NETFS_READ_FROM_CACHE) {
285 trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
286 goto issue;
287 }
288
289 pr_err("Unexpected read source %u\n", source);
290 WARN_ON_ONCE(1);
291 break;
292
293 issue:
294 slice = netfs_prepare_read_iterator(subreq);
295 if (slice < 0) {
296 ret = slice;
297 subreq->error = ret;
298 trace_netfs_sreq(subreq, netfs_sreq_trace_cancel);
299 /* Not queued - release both refs. */
300 netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
301 netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
302 break;
303 }
304 size -= slice;
305 start += slice;
306
307 netfs_queue_read(rreq, subreq, size <= 0);
308 netfs_issue_read(rreq, subreq);
309 cond_resched();
310 } while (size > 0);
311
312 if (unlikely(size > 0)) {
313 smp_wmb(); /* Write lists before ALL_QUEUED. */
314 set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags);
315 netfs_wake_read_collector(rreq);
316 }
317
318 /* Defer error return as we may need to wait for outstanding I/O. */
319 cmpxchg(&rreq->error, 0, ret);
320 }
321
322 /**
323 * netfs_readahead - Helper to manage a read request
324 * @ractl: The description of the readahead request
325 *
326 * Fulfil a readahead request by drawing data from the cache if possible, or
327 * the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O
328 * requests from different sources will get munged together. If necessary, the
329 * readahead window can be expanded in either direction to a more convenient
330 * alighment for RPC efficiency or to make storage in the cache feasible.
331 *
332 * The calling netfs must initialise a netfs context contiguous to the vfs
333 * inode before calling this.
334 *
335 * This is usable whether or not caching is enabled.
336 */
netfs_readahead(struct readahead_control * ractl)337 void netfs_readahead(struct readahead_control *ractl)
338 {
339 struct netfs_io_request *rreq;
340 struct netfs_inode *ictx = netfs_inode(ractl->mapping->host);
341 unsigned long long start = readahead_pos(ractl);
342 size_t size = readahead_length(ractl);
343 int ret;
344
345 rreq = netfs_alloc_request(ractl->mapping, ractl->file, start, size,
346 NETFS_READAHEAD);
347 if (IS_ERR(rreq))
348 return;
349
350 __set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags);
351
352 ret = netfs_begin_cache_read(rreq, ictx);
353 if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
354 goto cleanup_free;
355
356 netfs_stat(&netfs_n_rh_readahead);
357 trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
358 netfs_read_trace_readahead);
359
360 netfs_rreq_expand(rreq, ractl);
361
362 rreq->ractl = ractl;
363 rreq->submitted = rreq->start;
364 if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST) < 0)
365 goto cleanup_free;
366 netfs_read_to_pagecache(rreq);
367
368 netfs_put_request(rreq, true, netfs_rreq_trace_put_return);
369 return;
370
371 cleanup_free:
372 netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
373 return;
374 }
375 EXPORT_SYMBOL(netfs_readahead);
376
377 /*
378 * Create a rolling buffer with a single occupying folio.
379 */
netfs_create_singular_buffer(struct netfs_io_request * rreq,struct folio * folio,unsigned int rollbuf_flags)380 static int netfs_create_singular_buffer(struct netfs_io_request *rreq, struct folio *folio,
381 unsigned int rollbuf_flags)
382 {
383 ssize_t added;
384
385 if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST) < 0)
386 return -ENOMEM;
387
388 added = rolling_buffer_append(&rreq->buffer, folio, rollbuf_flags);
389 if (added < 0)
390 return added;
391 rreq->submitted = rreq->start + added;
392 rreq->ractl = (struct readahead_control *)1UL;
393 return 0;
394 }
395
396 /*
397 * Read into gaps in a folio partially filled by a streaming write.
398 */
netfs_read_gaps(struct file * file,struct folio * folio)399 static int netfs_read_gaps(struct file *file, struct folio *folio)
400 {
401 struct netfs_io_request *rreq;
402 struct address_space *mapping = folio->mapping;
403 struct netfs_folio *finfo = netfs_folio_info(folio);
404 struct netfs_inode *ctx = netfs_inode(mapping->host);
405 struct folio *sink = NULL;
406 struct bio_vec *bvec;
407 unsigned int from = finfo->dirty_offset;
408 unsigned int to = from + finfo->dirty_len;
409 unsigned int off = 0, i = 0;
410 size_t flen = folio_size(folio);
411 size_t nr_bvec = flen / PAGE_SIZE + 2;
412 size_t part;
413 int ret;
414
415 _enter("%lx", folio->index);
416
417 rreq = netfs_alloc_request(mapping, file, folio_pos(folio), flen, NETFS_READ_GAPS);
418 if (IS_ERR(rreq)) {
419 ret = PTR_ERR(rreq);
420 goto alloc_error;
421 }
422
423 ret = netfs_begin_cache_read(rreq, ctx);
424 if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
425 goto discard;
426
427 netfs_stat(&netfs_n_rh_read_folio);
428 trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_read_gaps);
429
430 /* Fiddle the buffer so that a gap at the beginning and/or a gap at the
431 * end get copied to, but the middle is discarded.
432 */
433 ret = -ENOMEM;
434 bvec = kmalloc_array(nr_bvec, sizeof(*bvec), GFP_KERNEL);
435 if (!bvec)
436 goto discard;
437
438 sink = folio_alloc(GFP_KERNEL, 0);
439 if (!sink) {
440 kfree(bvec);
441 goto discard;
442 }
443
444 trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
445
446 rreq->direct_bv = bvec;
447 rreq->direct_bv_count = nr_bvec;
448 if (from > 0) {
449 bvec_set_folio(&bvec[i++], folio, from, 0);
450 off = from;
451 }
452 while (off < to) {
453 part = min_t(size_t, to - off, PAGE_SIZE);
454 bvec_set_folio(&bvec[i++], sink, part, 0);
455 off += part;
456 }
457 if (to < flen)
458 bvec_set_folio(&bvec[i++], folio, flen - to, to);
459 iov_iter_bvec(&rreq->buffer.iter, ITER_DEST, bvec, i, rreq->len);
460 rreq->submitted = rreq->start + flen;
461
462 netfs_read_to_pagecache(rreq);
463
464 if (sink)
465 folio_put(sink);
466
467 ret = netfs_wait_for_read(rreq);
468 if (ret >= 0) {
469 flush_dcache_folio(folio);
470 folio_mark_uptodate(folio);
471 }
472 folio_unlock(folio);
473 netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
474 return ret < 0 ? ret : 0;
475
476 discard:
477 netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
478 alloc_error:
479 folio_unlock(folio);
480 return ret;
481 }
482
483 /**
484 * netfs_read_folio - Helper to manage a read_folio request
485 * @file: The file to read from
486 * @folio: The folio to read
487 *
488 * Fulfil a read_folio request by drawing data from the cache if
489 * possible, or the netfs if not. Space beyond the EOF is zero-filled.
490 * Multiple I/O requests from different sources will get munged together.
491 *
492 * The calling netfs must initialise a netfs context contiguous to the vfs
493 * inode before calling this.
494 *
495 * This is usable whether or not caching is enabled.
496 */
netfs_read_folio(struct file * file,struct folio * folio)497 int netfs_read_folio(struct file *file, struct folio *folio)
498 {
499 struct address_space *mapping = folio->mapping;
500 struct netfs_io_request *rreq;
501 struct netfs_inode *ctx = netfs_inode(mapping->host);
502 int ret;
503
504 if (folio_test_dirty(folio)) {
505 trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
506 return netfs_read_gaps(file, folio);
507 }
508
509 _enter("%lx", folio->index);
510
511 rreq = netfs_alloc_request(mapping, file,
512 folio_pos(folio), folio_size(folio),
513 NETFS_READPAGE);
514 if (IS_ERR(rreq)) {
515 ret = PTR_ERR(rreq);
516 goto alloc_error;
517 }
518
519 ret = netfs_begin_cache_read(rreq, ctx);
520 if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
521 goto discard;
522
523 netfs_stat(&netfs_n_rh_read_folio);
524 trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
525
526 /* Set up the output buffer */
527 ret = netfs_create_singular_buffer(rreq, folio, 0);
528 if (ret < 0)
529 goto discard;
530
531 netfs_read_to_pagecache(rreq);
532 ret = netfs_wait_for_read(rreq);
533 netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
534 return ret < 0 ? ret : 0;
535
536 discard:
537 netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
538 alloc_error:
539 folio_unlock(folio);
540 return ret;
541 }
542 EXPORT_SYMBOL(netfs_read_folio);
543
544 /*
545 * Prepare a folio for writing without reading first
546 * @folio: The folio being prepared
547 * @pos: starting position for the write
548 * @len: length of write
549 * @always_fill: T if the folio should always be completely filled/cleared
550 *
551 * In some cases, write_begin doesn't need to read at all:
552 * - full folio write
553 * - write that lies in a folio that is completely beyond EOF
554 * - write that covers the folio from start to EOF or beyond it
555 *
556 * If any of these criteria are met, then zero out the unwritten parts
557 * of the folio and return true. Otherwise, return false.
558 */
netfs_skip_folio_read(struct folio * folio,loff_t pos,size_t len,bool always_fill)559 static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
560 bool always_fill)
561 {
562 struct inode *inode = folio_inode(folio);
563 loff_t i_size = i_size_read(inode);
564 size_t offset = offset_in_folio(folio, pos);
565 size_t plen = folio_size(folio);
566
567 if (unlikely(always_fill)) {
568 if (pos - offset + len <= i_size)
569 return false; /* Page entirely before EOF */
570 folio_zero_segment(folio, 0, plen);
571 folio_mark_uptodate(folio);
572 return true;
573 }
574
575 /* Full folio write */
576 if (offset == 0 && len >= plen)
577 return true;
578
579 /* Page entirely beyond the end of the file */
580 if (pos - offset >= i_size)
581 goto zero_out;
582
583 /* Write that covers from the start of the folio to EOF or beyond */
584 if (offset == 0 && (pos + len) >= i_size)
585 goto zero_out;
586
587 return false;
588 zero_out:
589 folio_zero_segments(folio, 0, offset, offset + len, plen);
590 return true;
591 }
592
593 /**
594 * netfs_write_begin - Helper to prepare for writing [DEPRECATED]
595 * @ctx: The netfs context
596 * @file: The file to read from
597 * @mapping: The mapping to read from
598 * @pos: File position at which the write will begin
599 * @len: The length of the write (may extend beyond the end of the folio chosen)
600 * @_folio: Where to put the resultant folio
601 * @_fsdata: Place for the netfs to store a cookie
602 *
603 * Pre-read data for a write-begin request by drawing data from the cache if
604 * possible, or the netfs if not. Space beyond the EOF is zero-filled.
605 * Multiple I/O requests from different sources will get munged together.
606 *
607 * The calling netfs must provide a table of operations, only one of which,
608 * issue_read, is mandatory.
609 *
610 * The check_write_begin() operation can be provided to check for and flush
611 * conflicting writes once the folio is grabbed and locked. It is passed a
612 * pointer to the fsdata cookie that gets returned to the VM to be passed to
613 * write_end. It is permitted to sleep. It should return 0 if the request
614 * should go ahead or it may return an error. It may also unlock and put the
615 * folio, provided it sets ``*foliop`` to NULL, in which case a return of 0
616 * will cause the folio to be re-got and the process to be retried.
617 *
618 * The calling netfs must initialise a netfs context contiguous to the vfs
619 * inode before calling this.
620 *
621 * This is usable whether or not caching is enabled.
622 *
623 * Note that this should be considered deprecated and netfs_perform_write()
624 * used instead.
625 */
netfs_write_begin(struct netfs_inode * ctx,struct file * file,struct address_space * mapping,loff_t pos,unsigned int len,struct folio ** _folio,void ** _fsdata)626 int netfs_write_begin(struct netfs_inode *ctx,
627 struct file *file, struct address_space *mapping,
628 loff_t pos, unsigned int len, struct folio **_folio,
629 void **_fsdata)
630 {
631 struct netfs_io_request *rreq;
632 struct folio *folio;
633 pgoff_t index = pos >> PAGE_SHIFT;
634 int ret;
635
636 retry:
637 folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
638 mapping_gfp_mask(mapping));
639 if (IS_ERR(folio))
640 return PTR_ERR(folio);
641
642 if (ctx->ops->check_write_begin) {
643 /* Allow the netfs (eg. ceph) to flush conflicts. */
644 ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata);
645 if (ret < 0) {
646 trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
647 goto error;
648 }
649 if (!folio)
650 goto retry;
651 }
652
653 if (folio_test_uptodate(folio))
654 goto have_folio;
655
656 /* If the folio is beyond the EOF, we want to clear it - unless it's
657 * within the cache granule containing the EOF, in which case we need
658 * to preload the granule.
659 */
660 if (!netfs_is_cache_enabled(ctx) &&
661 netfs_skip_folio_read(folio, pos, len, false)) {
662 netfs_stat(&netfs_n_rh_write_zskip);
663 goto have_folio_no_wait;
664 }
665
666 rreq = netfs_alloc_request(mapping, file,
667 folio_pos(folio), folio_size(folio),
668 NETFS_READ_FOR_WRITE);
669 if (IS_ERR(rreq)) {
670 ret = PTR_ERR(rreq);
671 goto error;
672 }
673 rreq->no_unlock_folio = folio->index;
674 __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
675
676 ret = netfs_begin_cache_read(rreq, ctx);
677 if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
678 goto error_put;
679
680 netfs_stat(&netfs_n_rh_write_begin);
681 trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
682
683 /* Set up the output buffer */
684 ret = netfs_create_singular_buffer(rreq, folio, 0);
685 if (ret < 0)
686 goto error_put;
687
688 netfs_read_to_pagecache(rreq);
689 ret = netfs_wait_for_read(rreq);
690 if (ret < 0)
691 goto error;
692 netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
693
694 have_folio:
695 ret = folio_wait_private_2_killable(folio);
696 if (ret < 0)
697 goto error;
698 have_folio_no_wait:
699 *_folio = folio;
700 _leave(" = 0");
701 return 0;
702
703 error_put:
704 netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
705 error:
706 if (folio) {
707 folio_unlock(folio);
708 folio_put(folio);
709 }
710 _leave(" = %d", ret);
711 return ret;
712 }
713 EXPORT_SYMBOL(netfs_write_begin);
714
715 /*
716 * Preload the data into a folio we're proposing to write into.
717 */
netfs_prefetch_for_write(struct file * file,struct folio * folio,size_t offset,size_t len)718 int netfs_prefetch_for_write(struct file *file, struct folio *folio,
719 size_t offset, size_t len)
720 {
721 struct netfs_io_request *rreq;
722 struct address_space *mapping = folio->mapping;
723 struct netfs_inode *ctx = netfs_inode(mapping->host);
724 unsigned long long start = folio_pos(folio);
725 size_t flen = folio_size(folio);
726 int ret;
727
728 _enter("%zx @%llx", flen, start);
729
730 ret = -ENOMEM;
731
732 rreq = netfs_alloc_request(mapping, file, start, flen,
733 NETFS_READ_FOR_WRITE);
734 if (IS_ERR(rreq)) {
735 ret = PTR_ERR(rreq);
736 goto error;
737 }
738
739 rreq->no_unlock_folio = folio->index;
740 __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
741 ret = netfs_begin_cache_read(rreq, ctx);
742 if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
743 goto error_put;
744
745 netfs_stat(&netfs_n_rh_write_begin);
746 trace_netfs_read(rreq, start, flen, netfs_read_trace_prefetch_for_write);
747
748 /* Set up the output buffer */
749 ret = netfs_create_singular_buffer(rreq, folio, NETFS_ROLLBUF_PAGECACHE_MARK);
750 if (ret < 0)
751 goto error_put;
752
753 netfs_read_to_pagecache(rreq);
754 ret = netfs_wait_for_read(rreq);
755 netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
756 return ret < 0 ? ret : 0;
757
758 error_put:
759 netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
760 error:
761 _leave(" = %d", ret);
762 return ret;
763 }
764
765 /**
766 * netfs_buffered_read_iter - Filesystem buffered I/O read routine
767 * @iocb: kernel I/O control block
768 * @iter: destination for the data read
769 *
770 * This is the ->read_iter() routine for all filesystems that can use the page
771 * cache directly.
772 *
773 * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
774 * returned when no data can be read without waiting for I/O requests to
775 * complete; it doesn't prevent readahead.
776 *
777 * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
778 * shall be made for the read or for readahead. When no data can be read,
779 * -EAGAIN shall be returned. When readahead would be triggered, a partial,
780 * possibly empty read shall be returned.
781 *
782 * Return:
783 * * number of bytes copied, even for partial reads
784 * * negative error code (or 0 if IOCB_NOIO) if nothing was read
785 */
netfs_buffered_read_iter(struct kiocb * iocb,struct iov_iter * iter)786 ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter)
787 {
788 struct inode *inode = file_inode(iocb->ki_filp);
789 struct netfs_inode *ictx = netfs_inode(inode);
790 ssize_t ret;
791
792 if (WARN_ON_ONCE((iocb->ki_flags & IOCB_DIRECT) ||
793 test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)))
794 return -EINVAL;
795
796 ret = netfs_start_io_read(inode);
797 if (ret == 0) {
798 ret = filemap_read(iocb, iter, 0);
799 netfs_end_io_read(inode);
800 }
801 return ret;
802 }
803 EXPORT_SYMBOL(netfs_buffered_read_iter);
804
805 /**
806 * netfs_file_read_iter - Generic filesystem read routine
807 * @iocb: kernel I/O control block
808 * @iter: destination for the data read
809 *
810 * This is the ->read_iter() routine for all filesystems that can use the page
811 * cache directly.
812 *
813 * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
814 * returned when no data can be read without waiting for I/O requests to
815 * complete; it doesn't prevent readahead.
816 *
817 * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
818 * shall be made for the read or for readahead. When no data can be read,
819 * -EAGAIN shall be returned. When readahead would be triggered, a partial,
820 * possibly empty read shall be returned.
821 *
822 * Return:
823 * * number of bytes copied, even for partial reads
824 * * negative error code (or 0 if IOCB_NOIO) if nothing was read
825 */
netfs_file_read_iter(struct kiocb * iocb,struct iov_iter * iter)826 ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
827 {
828 struct netfs_inode *ictx = netfs_inode(iocb->ki_filp->f_mapping->host);
829
830 if ((iocb->ki_flags & IOCB_DIRECT) ||
831 test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))
832 return netfs_unbuffered_read_iter(iocb, iter);
833
834 return netfs_buffered_read_iter(iocb, iter);
835 }
836 EXPORT_SYMBOL(netfs_file_read_iter);
837