1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
|
// SPDX-License-Identifier: GPL-2.0-or-later
/* Network filesystem high-level buffered read support.
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/export.h>
#include <linux/task_io_accounting_ops.h>
#include "internal.h"
/*
* Unlock the folios in a read operation. We need to set PG_fscache on any
* folios we're going to write back before we unlock them.
*/
void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
{
struct netfs_io_subrequest *subreq;
struct netfs_folio *finfo;
struct folio *folio;
pgoff_t start_page = rreq->start / PAGE_SIZE;
pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
size_t account = 0;
bool subreq_failed = false;
XA_STATE(xas, &rreq->mapping->i_pages, start_page);
if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) {
__clear_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags);
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
__clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
}
}
/* Walk through the pagecache and the I/O request lists simultaneously.
* We may have a mixture of cached and uncached sections and we only
* really want to write out the uncached sections. This is slightly
* complicated by the possibility that we might have huge pages with a
* mixture inside.
*/
subreq = list_first_entry(&rreq->subrequests,
struct netfs_io_subrequest, rreq_link);
subreq_failed = (subreq->error < 0);
trace_netfs_rreq(rreq, netfs_rreq_trace_unlock);
rcu_read_lock();
xas_for_each(&xas, folio, last_page) {
loff_t pg_end;
bool pg_failed = false;
bool folio_started;
if (xas_retry(&xas, folio))
continue;
pg_end = folio_pos(folio) + folio_size(folio) - 1;
folio_started = false;
for (;;) {
loff_t sreq_end;
if (!subreq) {
pg_failed = true;
break;
}
if (!folio_started && test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags)) {
trace_netfs_folio(folio, netfs_folio_trace_copy_to_cache);
folio_start_fscache(folio);
folio_started = true;
}
pg_failed |= subreq_failed;
sreq_end = subreq->start + subreq->len - 1;
if (pg_end < sreq_end)
break;
account += subreq->transferred;
if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
subreq = list_next_entry(subreq, rreq_link);
subreq_failed = (subreq->error < 0);
} else {
subreq = NULL;
subreq_failed = false;
}
if (pg_end == sreq_end)
break;
}
if (!pg_failed) {
flush_dcache_folio(folio);
finfo = netfs_folio_info(folio);
if (finfo) {
trace_netfs_folio(folio, netfs_folio_trace_filled_gaps);
if (finfo->netfs_group)
folio_change_private(folio, finfo->netfs_group);
else
folio_detach_private(folio);
kfree(finfo);
}
folio_mark_uptodate(folio);
}
if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) {
if (folio_index(folio) == rreq->no_unlock_folio &&
test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags))
_debug("no unlock");
else
folio_unlock(folio);
}
}
rcu_read_unlock();
task_io_account_read(account);
if (rreq->netfs_ops->done)
rreq->netfs_ops->done(rreq);
}
static void netfs_cache_expand_readahead(struct netfs_io_request *rreq,
loff_t *_start, size_t *_len, loff_t i_size)
{
struct netfs_cache_resources *cres = &rreq->cache_resources;
if (cres->ops && cres->ops->expand_readahead)
cres->ops->expand_readahead(cres, _start, _len, i_size);
}
static void netfs_rreq_expand(struct netfs_io_request *rreq,
struct readahead_control *ractl)
{
/* Give the cache a chance to change the request parameters. The
* resultant request must contain the original region.
*/
netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size);
/* Give the netfs a chance to change the request parameters. The
* resultant request must contain the original region.
*/
if (rreq->netfs_ops->expand_readahead)
rreq->netfs_ops->expand_readahead(rreq);
/* Expand the request if the cache wants it to start earlier. Note
* that the expansion may get further extended if the VM wishes to
* insert THPs and the preferred start and/or end wind up in the middle
* of THPs.
*
* If this is the case, however, the THP size should be an integer
* multiple of the cache granule size, so we get a whole number of
* granules to deal with.
*/
if (rreq->start != readahead_pos(ractl) ||
rreq->len != readahead_length(ractl)) {
readahead_expand(ractl, rreq->start, rreq->len);
rreq->start = readahead_pos(ractl);
rreq->len = readahead_length(ractl);
trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
netfs_read_trace_expanded);
}
}
/*
* Begin an operation, and fetch the stored zero point value from the cookie if
* available.
*/
static int netfs_begin_cache_read(struct netfs_io_request *rreq, struct netfs_inode *ctx)
{
return fscache_begin_read_operation(&rreq->cache_resources, netfs_i_cookie(ctx));
}
/**
* netfs_readahead - Helper to manage a read request
* @ractl: The description of the readahead request
*
* Fulfil a readahead request by drawing data from the cache if possible, or
* the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O
* requests from different sources will get munged together. If necessary, the
* readahead window can be expanded in either direction to a more convenient
* alighment for RPC efficiency or to make storage in the cache feasible.
*
* The calling netfs must initialise a netfs context contiguous to the vfs
* inode before calling this.
*
* This is usable whether or not caching is enabled.
*/
void netfs_readahead(struct readahead_control *ractl)
{
struct netfs_io_request *rreq;
struct netfs_inode *ctx = netfs_inode(ractl->mapping->host);
int ret;
_enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
if (readahead_count(ractl) == 0)
return;
rreq = netfs_alloc_request(ractl->mapping, ractl->file,
readahead_pos(ractl),
readahead_length(ractl),
NETFS_READAHEAD);
if (IS_ERR(rreq))
return;
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto cleanup_free;
netfs_stat(&netfs_n_rh_readahead);
trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
netfs_read_trace_readahead);
netfs_rreq_expand(rreq, ractl);
/* Set up the output buffer */
iov_iter_xarray(&rreq->iter, ITER_DEST, &ractl->mapping->i_pages,
rreq->start, rreq->len);
/* Drop the refs on the folios here rather than in the cache or
* filesystem. The locks will be dropped in netfs_rreq_unlock().
*/
while (readahead_folio(ractl))
;
netfs_begin_read(rreq, false);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
return;
cleanup_free:
netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
return;
}
EXPORT_SYMBOL(netfs_readahead);
/**
* netfs_read_folio - Helper to manage a read_folio request
* @file: The file to read from
* @folio: The folio to read
*
* Fulfil a read_folio request by drawing data from the cache if
* possible, or the netfs if not. Space beyond the EOF is zero-filled.
* Multiple I/O requests from different sources will get munged together.
*
* The calling netfs must initialise a netfs context contiguous to the vfs
* inode before calling this.
*
* This is usable whether or not caching is enabled.
*/
int netfs_read_folio(struct file *file, struct folio *folio)
{
struct address_space *mapping = folio_file_mapping(folio);
struct netfs_io_request *rreq;
struct netfs_inode *ctx = netfs_inode(mapping->host);
struct folio *sink = NULL;
int ret;
_enter("%lx", folio_index(folio));
rreq = netfs_alloc_request(mapping, file,
folio_file_pos(folio), folio_size(folio),
NETFS_READPAGE);
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto alloc_error;
}
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto discard;
netfs_stat(&netfs_n_rh_readpage);
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
/* Set up the output buffer */
if (folio_test_dirty(folio)) {
/* Handle someone trying to read from an unflushed streaming
* write. We fiddle the buffer so that a gap at the beginning
* and/or a gap at the end get copied to, but the middle is
* discarded.
*/
struct netfs_folio *finfo = netfs_folio_info(folio);
struct bio_vec *bvec;
unsigned int from = finfo->dirty_offset;
unsigned int to = from + finfo->dirty_len;
unsigned int off = 0, i = 0;
size_t flen = folio_size(folio);
size_t nr_bvec = flen / PAGE_SIZE + 2;
size_t part;
ret = -ENOMEM;
bvec = kmalloc_array(nr_bvec, sizeof(*bvec), GFP_KERNEL);
if (!bvec)
goto discard;
sink = folio_alloc(GFP_KERNEL, 0);
if (!sink)
goto discard;
trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
rreq->direct_bv = bvec;
rreq->direct_bv_count = nr_bvec;
if (from > 0) {
bvec_set_folio(&bvec[i++], folio, from, 0);
off = from;
}
while (off < to) {
part = min_t(size_t, to - off, PAGE_SIZE);
bvec_set_folio(&bvec[i++], sink, part, 0);
off += part;
}
if (to < flen)
bvec_set_folio(&bvec[i++], folio, flen - to, to);
iov_iter_bvec(&rreq->iter, ITER_DEST, bvec, i, rreq->len);
} else {
iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages,
rreq->start, rreq->len);
}
ret = netfs_begin_read(rreq, true);
if (sink)
folio_put(sink);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
return ret < 0 ? ret : 0;
discard:
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
alloc_error:
folio_unlock(folio);
return ret;
}
EXPORT_SYMBOL(netfs_read_folio);
/*
* Prepare a folio for writing without reading first
* @folio: The folio being prepared
* @pos: starting position for the write
* @len: length of write
* @always_fill: T if the folio should always be completely filled/cleared
*
* In some cases, write_begin doesn't need to read at all:
* - full folio write
* - write that lies in a folio that is completely beyond EOF
* - write that covers the folio from start to EOF or beyond it
*
* If any of these criteria are met, then zero out the unwritten parts
* of the folio and return true. Otherwise, return false.
*/
static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
bool always_fill)
{
struct inode *inode = folio_inode(folio);
loff_t i_size = i_size_read(inode);
size_t offset = offset_in_folio(folio, pos);
size_t plen = folio_size(folio);
if (unlikely(always_fill)) {
if (pos - offset + len <= i_size)
return false; /* Page entirely before EOF */
zero_user_segment(&folio->page, 0, plen);
folio_mark_uptodate(folio);
return true;
}
/* Full folio write */
if (offset == 0 && len >= plen)
return true;
/* Page entirely beyond the end of the file */
if (pos - offset >= i_size)
goto zero_out;
/* Write that covers from the start of the folio to EOF or beyond */
if (offset == 0 && (pos + len) >= i_size)
goto zero_out;
return false;
zero_out:
zero_user_segments(&folio->page, 0, offset, offset + len, plen);
return true;
}
/**
* netfs_write_begin - Helper to prepare for writing
* @ctx: The netfs context
* @file: The file to read from
* @mapping: The mapping to read from
* @pos: File position at which the write will begin
* @len: The length of the write (may extend beyond the end of the folio chosen)
* @_folio: Where to put the resultant folio
* @_fsdata: Place for the netfs to store a cookie
*
* Pre-read data for a write-begin request by drawing data from the cache if
* possible, or the netfs if not. Space beyond the EOF is zero-filled.
* Multiple I/O requests from different sources will get munged together. If
* necessary, the readahead window can be expanded in either direction to a
* more convenient alighment for RPC efficiency or to make storage in the cache
* feasible.
*
* The calling netfs must provide a table of operations, only one of which,
* issue_op, is mandatory.
*
* The check_write_begin() operation can be provided to check for and flush
* conflicting writes once the folio is grabbed and locked. It is passed a
* pointer to the fsdata cookie that gets returned to the VM to be passed to
* write_end. It is permitted to sleep. It should return 0 if the request
* should go ahead or it may return an error. It may also unlock and put the
* folio, provided it sets ``*foliop`` to NULL, in which case a return of 0
* will cause the folio to be re-got and the process to be retried.
*
* The calling netfs must initialise a netfs context contiguous to the vfs
* inode before calling this.
*
* This is usable whether or not caching is enabled.
*/
int 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)
{
struct netfs_io_request *rreq;
struct folio *folio;
pgoff_t index = pos >> PAGE_SHIFT;
int ret;
DEFINE_READAHEAD(ractl, file, NULL, mapping, index);
retry:
folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
mapping_gfp_mask(mapping));
if (IS_ERR(folio))
return PTR_ERR(folio);
if (ctx->ops->check_write_begin) {
/* Allow the netfs (eg. ceph) to flush conflicts. */
ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata);
if (ret < 0) {
trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
goto error;
}
if (!folio)
goto retry;
}
if (folio_test_uptodate(folio))
goto have_folio;
/* If the page is beyond the EOF, we want to clear it - unless it's
* within the cache granule containing the EOF, in which case we need
* to preload the granule.
*/
if (!netfs_is_cache_enabled(ctx) &&
netfs_skip_folio_read(folio, pos, len, false)) {
netfs_stat(&netfs_n_rh_write_zskip);
goto have_folio_no_wait;
}
rreq = netfs_alloc_request(mapping, file,
folio_file_pos(folio), folio_size(folio),
NETFS_READ_FOR_WRITE);
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto error;
}
rreq->no_unlock_folio = folio_index(folio);
__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto error_put;
netfs_stat(&netfs_n_rh_write_begin);
trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
/* Expand the request to meet caching requirements and download
* preferences.
*/
ractl._nr_pages = folio_nr_pages(folio);
netfs_rreq_expand(rreq, &ractl);
/* Set up the output buffer */
iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages,
rreq->start, rreq->len);
/* We hold the folio locks, so we can drop the references */
folio_get(folio);
while (readahead_folio(&ractl))
;
ret = netfs_begin_read(rreq, true);
if (ret < 0)
goto error;
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
have_folio:
ret = folio_wait_fscache_killable(folio);
if (ret < 0)
goto error;
have_folio_no_wait:
*_folio = folio;
_leave(" = 0");
return 0;
error_put:
netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
error:
if (folio) {
folio_unlock(folio);
folio_put(folio);
}
_leave(" = %d", ret);
return ret;
}
EXPORT_SYMBOL(netfs_write_begin);
/*
* Preload the data into a page we're proposing to write into.
*/
int netfs_prefetch_for_write(struct file *file, struct folio *folio,
size_t offset, size_t len)
{
struct netfs_io_request *rreq;
struct address_space *mapping = folio_file_mapping(folio);
struct netfs_inode *ctx = netfs_inode(mapping->host);
unsigned long long start = folio_pos(folio);
size_t flen = folio_size(folio);
int ret;
_enter("%zx @%llx", flen, start);
ret = -ENOMEM;
rreq = netfs_alloc_request(mapping, file, start, flen,
NETFS_READ_FOR_WRITE);
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto error;
}
rreq->no_unlock_folio = folio_index(folio);
__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto error_put;
netfs_stat(&netfs_n_rh_write_begin);
trace_netfs_read(rreq, start, flen, netfs_read_trace_prefetch_for_write);
/* Set up the output buffer */
iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages,
rreq->start, rreq->len);
ret = netfs_begin_read(rreq, true);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
return ret;
error_put:
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
error:
_leave(" = %d", ret);
return ret;
}
/**
* netfs_buffered_read_iter - Filesystem buffered I/O read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the ->read_iter() routine for all filesystems that can use the page
* cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
* returned when no data can be read without waiting for I/O requests to
* complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
* shall be made for the read or for readahead. When no data can be read,
* -EAGAIN shall be returned. When readahead would be triggered, a partial,
* possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct netfs_inode *ictx = netfs_inode(inode);
ssize_t ret;
if (WARN_ON_ONCE((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)))
return -EINVAL;
ret = netfs_start_io_read(inode);
if (ret == 0) {
ret = filemap_read(iocb, iter, 0);
netfs_end_io_read(inode);
}
return ret;
}
EXPORT_SYMBOL(netfs_buffered_read_iter);
/**
* netfs_file_read_iter - Generic filesystem read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the ->read_iter() routine for all filesystems that can use the page
* cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
* returned when no data can be read without waiting for I/O requests to
* complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
* shall be made for the read or for readahead. When no data can be read,
* -EAGAIN shall be returned. When readahead would be triggered, a partial,
* possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct netfs_inode *ictx = netfs_inode(iocb->ki_filp->f_mapping->host);
if ((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))
return netfs_unbuffered_read_iter(iocb, iter);
return netfs_buffered_read_iter(iocb, iter);
}
EXPORT_SYMBOL(netfs_file_read_iter);
|