1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Network filesystem read subrequest retrying.
3 *
4 * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/fs.h>
9 #include <linux/slab.h>
10 #include "internal.h"
11
12 static void netfs_reissue_read(struct netfs_io_request *rreq,
13 struct netfs_io_subrequest *subreq)
14 {
15 struct iov_iter *io_iter = &subreq->io_iter;
16
17 if (iov_iter_is_folioq(io_iter)) {
18 subreq->curr_folioq = (struct folio_queue *)io_iter->folioq;
19 subreq->curr_folioq_slot = io_iter->folioq_slot;
20 subreq->curr_folio_order = subreq->curr_folioq->orders[subreq->curr_folioq_slot];
21 }
22
23 atomic_inc(&rreq->nr_outstanding);
24 __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
25 netfs_get_subrequest(subreq, netfs_sreq_trace_get_resubmit);
26 subreq->rreq->netfs_ops->issue_read(subreq);
27 }
28
29 /*
30 * Go through the list of failed/short reads, retrying all retryable ones. We
31 * need to switch failed cache reads to network downloads.
32 */
33 static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
34 {
35 struct netfs_io_subrequest *subreq;
36 struct netfs_io_stream *stream0 = &rreq->io_streams[0];
37 LIST_HEAD(sublist);
38 LIST_HEAD(queue);
39
40 _enter("R=%x", rreq->debug_id);
41
42 if (list_empty(&rreq->subrequests))
43 return;
44
45 if (rreq->netfs_ops->retry_request)
46 rreq->netfs_ops->retry_request(rreq, NULL);
47
48 /* If there's no renegotiation to do, just resend each retryable subreq
49 * up to the first permanently failed one.
50 */
51 if (!rreq->netfs_ops->prepare_read &&
52 !test_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags)) {
53 struct netfs_io_subrequest *subreq;
54
55 list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
56 if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
57 break;
58 if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) {
59 netfs_reset_iter(subreq);
60 netfs_reissue_read(rreq, subreq);
61 }
62 }
63 return;
64 }
65
66 /* Okay, we need to renegotiate all the download requests and flip any
67 * failed cache reads over to being download requests and negotiate
68 * those also. All fully successful subreqs have been removed from the
69 * list and any spare data from those has been donated.
70 *
71 * What we do is decant the list and rebuild it one subreq at a time so
72 * that we don't end up with donations jumping over a gap we're busy
73 * populating with smaller subrequests. In the event that the subreq
74 * we just launched finishes before we insert the next subreq, it'll
75 * fill in rreq->prev_donated instead.
76
77 * Note: Alternatively, we could split the tail subrequest right before
78 * we reissue it and fix up the donations under lock.
79 */
80 list_splice_init(&rreq->subrequests, &queue);
81
82 do {
83 struct netfs_io_subrequest *from;
84 struct iov_iter source;
85 unsigned long long start, len;
86 size_t part, deferred_next_donated = 0;
87 bool boundary = false;
88
89 /* Go through the subreqs and find the next span of contiguous
90 * buffer that we then rejig (cifs, for example, needs the
91 * rsize renegotiating) and reissue.
92 */
93 from = list_first_entry(&queue, struct netfs_io_subrequest, rreq_link);
94 list_move_tail(&from->rreq_link, &sublist);
95 start = from->start + from->transferred;
96 len = from->len - from->transferred;
97
98 _debug("from R=%08x[%x] s=%llx ctl=%zx/%zx/%zx",
99 rreq->debug_id, from->debug_index,
100 from->start, from->consumed, from->transferred, from->len);
101
102 if (test_bit(NETFS_SREQ_FAILED, &from->flags) ||
103 !test_bit(NETFS_SREQ_NEED_RETRY, &from->flags))
104 goto abandon;
105
106 deferred_next_donated = from->next_donated;
107 while ((subreq = list_first_entry_or_null(
108 &queue, struct netfs_io_subrequest, rreq_link))) {
109 if (subreq->start != start + len ||
110 subreq->transferred > 0 ||
111 !test_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags))
112 break;
113 list_move_tail(&subreq->rreq_link, &sublist);
114 len += subreq->len;
115 deferred_next_donated = subreq->next_donated;
116 if (test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags))
117 break;
118 }
119
120 _debug(" - range: %llx-%llx %llx", start, start + len - 1, len);
121
122 /* Determine the set of buffers we're going to use. Each
123 * subreq gets a subset of a single overall contiguous buffer.
124 */
125 netfs_reset_iter(from);
126 source = from->io_iter;
127 source.count = len;
128
129 /* Work through the sublist. */
130 while ((subreq = list_first_entry_or_null(
131 &sublist, struct netfs_io_subrequest, rreq_link))) {
132 list_del(&subreq->rreq_link);
133
134 subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
135 subreq->start = start - subreq->transferred;
136 subreq->len = len + subreq->transferred;
137 stream0->sreq_max_len = subreq->len;
138
139 __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
140 __set_bit(NETFS_SREQ_RETRYING, &subreq->flags);
141
142 spin_lock_bh(&rreq->lock);
143 list_add_tail(&subreq->rreq_link, &rreq->subrequests);
144 subreq->prev_donated += rreq->prev_donated;
145 rreq->prev_donated = 0;
146 trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
147 spin_unlock_bh(&rreq->lock);
148
149 BUG_ON(!len);
150
151 /* Renegotiate max_len (rsize) */
152 if (rreq->netfs_ops->prepare_read(subreq) < 0) {
153 trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed);
154 __set_bit(NETFS_SREQ_FAILED, &subreq->flags);
155 }
156
157 part = umin(len, stream0->sreq_max_len);
158 if (unlikely(rreq->io_streams[0].sreq_max_segs))
159 part = netfs_limit_iter(&source, 0, part, stream0->sreq_max_segs);
160 subreq->len = subreq->transferred + part;
161 subreq->io_iter = source;
162 iov_iter_truncate(&subreq->io_iter, part);
163 iov_iter_advance(&source, part);
164 len -= part;
165 start += part;
166 if (!len) {
167 if (boundary)
168 __set_bit(NETFS_SREQ_BOUNDARY, &subreq->flags);
169 subreq->next_donated = deferred_next_donated;
170 } else {
171 __clear_bit(NETFS_SREQ_BOUNDARY, &subreq->flags);
172 subreq->next_donated = 0;
173 }
174
175 netfs_reissue_read(rreq, subreq);
176 if (!len)
177 break;
178
179 /* If we ran out of subrequests, allocate another. */
180 if (list_empty(&sublist)) {
181 subreq = netfs_alloc_subrequest(rreq);
182 if (!subreq)
183 goto abandon;
184 subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
185 subreq->start = start;
186
187 /* We get two refs, but need just one. */
188 netfs_put_subrequest(subreq, false, netfs_sreq_trace_new);
189 trace_netfs_sreq(subreq, netfs_sreq_trace_split);
190 list_add_tail(&subreq->rreq_link, &sublist);
191 }
192 }
193
194 /* If we managed to use fewer subreqs, we can discard the
195 * excess.
196 */
197 while ((subreq = list_first_entry_or_null(
198 &sublist, struct netfs_io_subrequest, rreq_link))) {
199 trace_netfs_sreq(subreq, netfs_sreq_trace_discard);
200 list_del(&subreq->rreq_link);
201 netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_done);
202 }
203
204 } while (!list_empty(&queue));
205
206 return;
207
208 /* If we hit ENOMEM, fail all remaining subrequests */
209 abandon:
210 list_splice_init(&sublist, &queue);
211 list_for_each_entry(subreq, &queue, rreq_link) {
212 if (!subreq->error)
213 subreq->error = -ENOMEM;
214 __clear_bit(NETFS_SREQ_FAILED, &subreq->flags);
215 __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
216 __clear_bit(NETFS_SREQ_RETRYING, &subreq->flags);
217 }
218 spin_lock_bh(&rreq->lock);
219 list_splice_tail_init(&queue, &rreq->subrequests);
220 spin_unlock_bh(&rreq->lock);
221 }
222
223 /*
224 * Retry reads.
225 */
226 void netfs_retry_reads(struct netfs_io_request *rreq)
227 {
228 trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
229
230 atomic_inc(&rreq->nr_outstanding);
231
232 netfs_retry_read_subrequests(rreq);
233
234 if (atomic_dec_and_test(&rreq->nr_outstanding))
235 netfs_rreq_terminated(rreq, false);
236 }
237
238 /*
239 * Unlock any the pages that haven't been unlocked yet due to abandoned
240 * subrequests.
241 */
242 void netfs_unlock_abandoned_read_pages(struct netfs_io_request *rreq)
243 {
244 struct folio_queue *p;
245
246 for (p = rreq->buffer; p; p = p->next) {
247 for (int slot = 0; slot < folioq_count(p); slot++) {
248 struct folio *folio = folioq_folio(p, slot);
249
250 if (folio && !folioq_is_marked2(p, slot)) {
251 trace_netfs_folio(folio, netfs_folio_trace_abandon);
252 folio_unlock(folio);
253 }
254 }
255 }
256 }
257
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