1 /*-
2 * SPDX-License-Identifier: Beerware
3 *
4 * ----------------------------------------------------------------------------
5 * "THE BEER-WARE LICENSE" (Revision 42):
6 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
7 * can do whatever you want with this stuff. If we meet some day, and you think
8 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
9 * ----------------------------------------------------------------------------
10 *
11 * The bioq_disksort() (and the specification of the bioq API)
12 * have been written by Luigi Rizzo and Fabio Checconi under the same
13 * license as above.
14 */
15
16 #include <sys/cdefs.h>
17 #include "opt_geom.h"
18
19 #include <sys/param.h>
20 #include <sys/systm.h>
21 #include <sys/bio.h>
22 #include <sys/conf.h>
23 #include <sys/disk.h>
24 #include <sys/sysctl.h>
25 #include <geom/geom_disk.h>
26
27 static int bioq_batchsize = 128;
28 SYSCTL_INT(_debug, OID_AUTO, bioq_batchsize, CTLFLAG_RW,
29 &bioq_batchsize, 0, "BIOQ batch size");
30
31 /*-
32 * Disk error is the preface to plaintive error messages
33 * about failing disk transfers. It prints messages of the form
34 * "hp0g: BLABLABLA cmd=read fsbn 12345 of 12344-12347"
35 * blkdone should be -1 if the position of the error is unknown.
36 * The message is printed with printf.
37 */
38 void
disk_err(struct bio * bp,const char * what,int blkdone,int nl)39 disk_err(struct bio *bp, const char *what, int blkdone, int nl)
40 {
41 daddr_t sn;
42
43 if (bp->bio_dev != NULL)
44 printf("%s: %s ", devtoname(bp->bio_dev), what);
45 else if (bp->bio_disk != NULL)
46 printf("%s%d: %s ",
47 bp->bio_disk->d_name, bp->bio_disk->d_unit, what);
48 else
49 printf("disk??: %s ", what);
50 switch(bp->bio_cmd) {
51 case BIO_READ: printf("cmd=read "); break;
52 case BIO_WRITE: printf("cmd=write "); break;
53 case BIO_DELETE: printf("cmd=delete "); break;
54 case BIO_GETATTR: printf("cmd=getattr "); break;
55 case BIO_FLUSH: printf("cmd=flush "); break;
56 default: printf("cmd=%x ", bp->bio_cmd); break;
57 }
58 sn = bp->bio_pblkno;
59 if (bp->bio_bcount <= DEV_BSIZE) {
60 printf("fsbn %jd%s", (intmax_t)sn, nl ? "\n" : "");
61 return;
62 }
63 if (blkdone >= 0) {
64 sn += blkdone;
65 printf("fsbn %jd of ", (intmax_t)sn);
66 }
67 printf("%jd-%jd", (intmax_t)bp->bio_pblkno,
68 (intmax_t)(bp->bio_pblkno + (bp->bio_bcount - 1) / DEV_BSIZE));
69 if (nl)
70 printf("\n");
71 }
72
73 /*
74 * BIO queue implementation
75 *
76 * Please read carefully the description below before making any change
77 * to the code, or you might change the behaviour of the data structure
78 * in undesirable ways.
79 *
80 * A bioq stores disk I/O request (bio), normally sorted according to
81 * the distance of the requested position (bio->bio_offset) from the
82 * current head position (bioq->last_offset) in the scan direction, i.e.
83 *
84 * (uoff_t)(bio_offset - last_offset)
85 *
86 * Note that the cast to unsigned (uoff_t) is fundamental to insure
87 * that the distance is computed in the scan direction.
88 *
89 * The main methods for manipulating the bioq are:
90 *
91 * bioq_disksort() performs an ordered insertion;
92 *
93 * bioq_first() return the head of the queue, without removing;
94 *
95 * bioq_takefirst() return and remove the head of the queue,
96 * updating the 'current head position' as
97 * bioq->last_offset = bio->bio_offset + bio->bio_length;
98 *
99 * When updating the 'current head position', we assume that the result of
100 * bioq_takefirst() is dispatched to the device, so bioq->last_offset
101 * represents the head position once the request is complete.
102 *
103 * If the bioq is manipulated using only the above calls, it starts
104 * with a sorted sequence of requests with bio_offset >= last_offset,
105 * possibly followed by another sorted sequence of requests with
106 * 0 <= bio_offset < bioq->last_offset
107 *
108 * NOTE: historical behaviour was to ignore bio->bio_length in the
109 * update, but its use tracks the head position in a better way.
110 * Historical behaviour was also to update the head position when
111 * the request under service is complete, rather than when the
112 * request is extracted from the queue. However, the current API
113 * has no method to update the head position; secondly, once
114 * a request has been submitted to the disk, we have no idea of
115 * the actual head position, so the final one is our best guess.
116 *
117 * --- Direct queue manipulation ---
118 *
119 * A bioq uses an underlying TAILQ to store requests, so we also
120 * export methods to manipulate the TAILQ, in particular:
121 *
122 * bioq_insert_tail() insert an entry at the end.
123 * It also creates a 'barrier' so all subsequent
124 * insertions through bioq_disksort() will end up
125 * after this entry;
126 *
127 * bioq_insert_head() insert an entry at the head, update
128 * bioq->last_offset = bio->bio_offset so that
129 * all subsequent insertions through bioq_disksort()
130 * will end up after this entry;
131 *
132 * bioq_remove() remove a generic element from the queue, act as
133 * bioq_takefirst() if invoked on the head of the queue.
134 *
135 * The semantic of these methods is the same as the operations
136 * on the underlying TAILQ, but with additional guarantees on
137 * subsequent bioq_disksort() calls. E.g. bioq_insert_tail()
138 * can be useful for making sure that all previous ops are flushed
139 * to disk before continuing.
140 *
141 * Updating bioq->last_offset on a bioq_insert_head() guarantees
142 * that the bio inserted with the last bioq_insert_head() will stay
143 * at the head of the queue even after subsequent bioq_disksort().
144 *
145 * Note that when the direct queue manipulation functions are used,
146 * the queue may contain multiple inversion points (i.e. more than
147 * two sorted sequences of requests).
148 *
149 */
150
151 void
bioq_init(struct bio_queue_head * head)152 bioq_init(struct bio_queue_head *head)
153 {
154
155 TAILQ_INIT(&head->queue);
156 head->last_offset = 0;
157 head->insert_point = NULL;
158 head->total = 0;
159 head->batched = 0;
160 }
161
162 void
bioq_remove(struct bio_queue_head * head,struct bio * bp)163 bioq_remove(struct bio_queue_head *head, struct bio *bp)
164 {
165
166 if (head->insert_point == NULL) {
167 if (bp == TAILQ_FIRST(&head->queue))
168 head->last_offset = bp->bio_offset + bp->bio_length;
169 } else if (bp == head->insert_point)
170 head->insert_point = NULL;
171
172 TAILQ_REMOVE(&head->queue, bp, bio_queue);
173 if (TAILQ_EMPTY(&head->queue))
174 head->batched = 0;
175 head->total--;
176 }
177
178 void
bioq_flush(struct bio_queue_head * head,struct devstat * stp,int error)179 bioq_flush(struct bio_queue_head *head, struct devstat *stp, int error)
180 {
181 struct bio *bp;
182
183 while ((bp = bioq_takefirst(head)) != NULL)
184 biofinish(bp, stp, error);
185 }
186
187 void
bioq_insert_head(struct bio_queue_head * head,struct bio * bp)188 bioq_insert_head(struct bio_queue_head *head, struct bio *bp)
189 {
190
191 if (head->insert_point == NULL)
192 head->last_offset = bp->bio_offset;
193 TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
194 head->total++;
195 head->batched = 0;
196 }
197
198 void
bioq_insert_tail(struct bio_queue_head * head,struct bio * bp)199 bioq_insert_tail(struct bio_queue_head *head, struct bio *bp)
200 {
201
202 TAILQ_INSERT_TAIL(&head->queue, bp, bio_queue);
203 head->total++;
204 head->batched = 0;
205 head->insert_point = bp;
206 head->last_offset = bp->bio_offset;
207 }
208
209 struct bio *
bioq_first(struct bio_queue_head * head)210 bioq_first(struct bio_queue_head *head)
211 {
212
213 return (TAILQ_FIRST(&head->queue));
214 }
215
216 struct bio *
bioq_takefirst(struct bio_queue_head * head)217 bioq_takefirst(struct bio_queue_head *head)
218 {
219 struct bio *bp;
220
221 bp = TAILQ_FIRST(&head->queue);
222 if (bp != NULL)
223 bioq_remove(head, bp);
224 return (bp);
225 }
226
227 /*
228 * Compute the sorting key. The cast to unsigned is
229 * fundamental for correctness, see the description
230 * near the beginning of the file.
231 */
232 static inline uoff_t
bioq_bio_key(struct bio_queue_head * head,struct bio * bp)233 bioq_bio_key(struct bio_queue_head *head, struct bio *bp)
234 {
235
236 return ((uoff_t)(bp->bio_offset - head->last_offset));
237 }
238
239 /*
240 * Seek sort for disks.
241 *
242 * Sort all requests in a single queue while keeping
243 * track of the current position of the disk with last_offset.
244 * See above for details.
245 */
246 void
bioq_disksort(struct bio_queue_head * head,struct bio * bp)247 bioq_disksort(struct bio_queue_head *head, struct bio *bp)
248 {
249 struct bio *cur, *prev;
250 uoff_t key;
251
252 if ((bp->bio_flags & BIO_ORDERED) != 0) {
253 /*
254 * Ordered transactions can only be dispatched
255 * after any currently queued transactions. They
256 * also have barrier semantics - no transactions
257 * queued in the future can pass them.
258 */
259 bioq_insert_tail(head, bp);
260 return;
261 }
262
263 /*
264 * We should only sort requests of types that have concept of offset.
265 * Other types, such as BIO_FLUSH or BIO_ZONE, may imply some degree
266 * of ordering even if strict ordering is not requested explicitly.
267 */
268 if (bp->bio_cmd != BIO_READ && bp->bio_cmd != BIO_WRITE &&
269 bp->bio_cmd != BIO_DELETE) {
270 bioq_insert_tail(head, bp);
271 return;
272 }
273
274 if (bioq_batchsize > 0 && head->batched > bioq_batchsize) {
275 bioq_insert_tail(head, bp);
276 return;
277 }
278
279 prev = NULL;
280 key = bioq_bio_key(head, bp);
281 cur = TAILQ_FIRST(&head->queue);
282
283 if (head->insert_point) {
284 prev = head->insert_point;
285 cur = TAILQ_NEXT(head->insert_point, bio_queue);
286 }
287
288 while (cur != NULL && key >= bioq_bio_key(head, cur)) {
289 prev = cur;
290 cur = TAILQ_NEXT(cur, bio_queue);
291 }
292
293 if (prev == NULL)
294 TAILQ_INSERT_HEAD(&head->queue, bp, bio_queue);
295 else
296 TAILQ_INSERT_AFTER(&head->queue, prev, bp, bio_queue);
297 head->total++;
298 head->batched++;
299 }
300