1 /*
2 * faulty.c : Multiple Devices driver for Linux
3 *
4 * Copyright (C) 2004 Neil Brown
5 *
6 * fautly-device-simulator personality for md
7 *
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2, or (at your option)
12 * any later version.
13 *
14 * You should have received a copy of the GNU General Public License
15 * (for example /usr/src/linux/COPYING); if not, write to the Free
16 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19
20 /*
21 * The "faulty" personality causes some requests to fail.
22 *
23 * Possible failure modes are:
24 * reads fail "randomly" but succeed on retry
25 * writes fail "randomly" but succeed on retry
26 * reads for some address fail and then persist until a write
27 * reads for some address fail and then persist irrespective of write
28 * writes for some address fail and persist
29 * all writes fail
30 *
31 * Different modes can be active at a time, but only
32 * one can be set at array creation. Others can be added later.
33 * A mode can be one-shot or recurrent with the recurrance being
34 * once in every N requests.
35 * The bottom 5 bits of the "layout" indicate the mode. The
36 * remainder indicate a period, or 0 for one-shot.
37 *
38 * There is an implementation limit on the number of concurrently
39 * persisting-faulty blocks. When a new fault is requested that would
40 * exceed the limit, it is ignored.
41 * All current faults can be clear using a layout of "".
42 *
43 * Requests are always sent to the device. If they are to fail,
44 * we clone the bio and insert a new b_end_io into the chain.
45 */
46
47 #define WriteTransient 0
48 #define ReadTransient 1
49 #define WritePersistent 2
50 #define ReadPersistent 3
51 #define WriteAll 4 /* doesn't go to device */
52 #define ReadFixable 5
53 #define Modes 6
54
55 #define ClearErrors 31
56 #define ClearFaults 30
57
58 #define AllPersist 100 /* internal use only */
59 #define NoPersist 101
60
61 #define ModeMask 0x1f
62 #define ModeShift 5
63
64 #define MaxFault 50
65 #include <linux/raid/md.h>
66
67
68 static int faulty_fail(struct bio *bio, unsigned int bytes_done, int error)
69 {
70 struct bio *b = bio->bi_private;
71
72 b->bi_size = bio->bi_size;
73 b->bi_sector = bio->bi_sector;
74
75 if (bio->bi_size == 0)
76 bio_put(bio);
77
78 clear_bit(BIO_UPTODATE, &b->bi_flags);
79 return (b->bi_end_io)(b, bytes_done, -EIO);
80 }
81
82 typedef struct faulty_conf {
83 int period[Modes];
84 atomic_t counters[Modes];
85 sector_t faults[MaxFault];
86 int modes[MaxFault];
87 int nfaults;
88 mdk_rdev_t *rdev;
89 } conf_t;
90
91 static int check_mode(conf_t *conf, int mode)
92 {
93 if (conf->period[mode] == 0 &&
94 atomic_read(&conf->counters[mode]) <= 0)
95 return 0; /* no failure, no decrement */
96
97
98 if (atomic_dec_and_test(&conf->counters[mode])) {
99 if (conf->period[mode])
100 atomic_set(&conf->counters[mode], conf->period[mode]);
101 return 1;
102 }
103 return 0;
104 }
105
106 static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
107 {
108 /* If we find a ReadFixable sector, we fix it ... */
109 int i;
110 for (i=0; i<conf->nfaults; i++)
111 if (conf->faults[i] >= start &&
112 conf->faults[i] < end) {
113 /* found it ... */
114 switch (conf->modes[i] * 2 + dir) {
115 case WritePersistent*2+WRITE: return 1;
116 case ReadPersistent*2+READ: return 1;
117 case ReadFixable*2+READ: return 1;
118 case ReadFixable*2+WRITE:
119 conf->modes[i] = NoPersist;
120 return 0;
121 case AllPersist*2+READ:
122 case AllPersist*2+WRITE: return 1;
123 default:
124 return 0;
125 }
126 }
127 return 0;
128 }
129
130 static void add_sector(conf_t *conf, sector_t start, int mode)
131 {
132 int i;
133 int n = conf->nfaults;
134 for (i=0; i<conf->nfaults; i++)
135 if (conf->faults[i] == start) {
136 switch(mode) {
137 case NoPersist: conf->modes[i] = mode; return;
138 case WritePersistent:
139 if (conf->modes[i] == ReadPersistent ||
140 conf->modes[i] == ReadFixable)
141 conf->modes[i] = AllPersist;
142 else
143 conf->modes[i] = WritePersistent;
144 return;
145 case ReadPersistent:
146 if (conf->modes[i] == WritePersistent)
147 conf->modes[i] = AllPersist;
148 else
149 conf->modes[i] = ReadPersistent;
150 return;
151 case ReadFixable:
152 if (conf->modes[i] == WritePersistent ||
153 conf->modes[i] == ReadPersistent)
154 conf->modes[i] = AllPersist;
155 else
156 conf->modes[i] = ReadFixable;
157 return;
158 }
159 } else if (conf->modes[i] == NoPersist)
160 n = i;
161
162 if (n >= MaxFault)
163 return;
164 conf->faults[n] = start;
165 conf->modes[n] = mode;
166 if (conf->nfaults == n)
167 conf->nfaults = n+1;
168 }
169
170 static int make_request(request_queue_t *q, struct bio *bio)
171 {
172 mddev_t *mddev = q->queuedata;
173 conf_t *conf = (conf_t*)mddev->private;
174 int failit = 0;
175
176 if (bio->bi_rw & 1) {
177 /* write request */
178 if (atomic_read(&conf->counters[WriteAll])) {
179 /* special case - don't decrement, don't generic_make_request,
180 * just fail immediately
181 */
182 bio_endio(bio, bio->bi_size, -EIO);
183 return 0;
184 }
185
186 if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
187 WRITE))
188 failit = 1;
189 if (check_mode(conf, WritePersistent)) {
190 add_sector(conf, bio->bi_sector, WritePersistent);
191 failit = 1;
192 }
193 if (check_mode(conf, WriteTransient))
194 failit = 1;
195 } else {
196 /* read request */
197 if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
198 READ))
199 failit = 1;
200 if (check_mode(conf, ReadTransient))
201 failit = 1;
202 if (check_mode(conf, ReadPersistent)) {
203 add_sector(conf, bio->bi_sector, ReadPersistent);
204 failit = 1;
205 }
206 if (check_mode(conf, ReadFixable)) {
207 add_sector(conf, bio->bi_sector, ReadFixable);
208 failit = 1;
209 }
210 }
211 if (failit) {
212 struct bio *b = bio_clone(bio, GFP_NOIO);
213 b->bi_bdev = conf->rdev->bdev;
214 b->bi_private = bio;
215 b->bi_end_io = faulty_fail;
216 generic_make_request(b);
217 return 0;
218 } else {
219 bio->bi_bdev = conf->rdev->bdev;
220 return 1;
221 }
222 }
223
224 static void status(struct seq_file *seq, mddev_t *mddev)
225 {
226 conf_t *conf = (conf_t*)mddev->private;
227 int n;
228
229 if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
230 seq_printf(seq, " WriteTransient=%d(%d)",
231 n, conf->period[WriteTransient]);
232
233 if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
234 seq_printf(seq, " ReadTransient=%d(%d)",
235 n, conf->period[ReadTransient]);
236
237 if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
238 seq_printf(seq, " WritePersistent=%d(%d)",
239 n, conf->period[WritePersistent]);
240
241 if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
242 seq_printf(seq, " ReadPersistent=%d(%d)",
243 n, conf->period[ReadPersistent]);
244
245
246 if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
247 seq_printf(seq, " ReadFixable=%d(%d)",
248 n, conf->period[ReadFixable]);
249
250 if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
251 seq_printf(seq, " WriteAll");
252
253 seq_printf(seq, " nfaults=%d", conf->nfaults);
254 }
255
256
257 static int reconfig(mddev_t *mddev, int layout, int chunk_size)
258 {
259 int mode = layout & ModeMask;
260 int count = layout >> ModeShift;
261 conf_t *conf = mddev->private;
262
263 if (chunk_size != -1)
264 return -EINVAL;
265
266 /* new layout */
267 if (mode == ClearFaults)
268 conf->nfaults = 0;
269 else if (mode == ClearErrors) {
270 int i;
271 for (i=0 ; i < Modes ; i++) {
272 conf->period[i] = 0;
273 atomic_set(&conf->counters[i], 0);
274 }
275 } else if (mode < Modes) {
276 conf->period[mode] = count;
277 if (!count) count++;
278 atomic_set(&conf->counters[mode], count);
279 } else
280 return -EINVAL;
281 mddev->layout = -1; /* makes sure further changes come through */
282 return 0;
283 }
284
285 static int run(mddev_t *mddev)
286 {
287 mdk_rdev_t *rdev;
288 struct list_head *tmp;
289 int i;
290
291 conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
292
293 for (i=0; i<Modes; i++) {
294 atomic_set(&conf->counters[i], 0);
295 conf->period[i] = 0;
296 }
297 conf->nfaults = 0;
298
299 ITERATE_RDEV(mddev, rdev, tmp)
300 conf->rdev = rdev;
301
302 mddev->array_size = mddev->size;
303 mddev->private = conf;
304
305 reconfig(mddev, mddev->layout, -1);
306
307 return 0;
308 }
309
310 static int stop(mddev_t *mddev)
311 {
312 conf_t *conf = (conf_t *)mddev->private;
313
314 kfree(conf);
315 mddev->private = NULL;
316 return 0;
317 }
318
319 static struct mdk_personality faulty_personality =
320 {
321 .name = "faulty",
322 .level = LEVEL_FAULTY,
323 .owner = THIS_MODULE,
324 .make_request = make_request,
325 .run = run,
326 .stop = stop,
327 .status = status,
328 .reconfig = reconfig,
329 };
330
331 static int __init raid_init(void)
332 {
333 return register_md_personality(&faulty_personality);
334 }
335
336 static void raid_exit(void)
337 {
338 unregister_md_personality(&faulty_personality);
339 }
340
341 module_init(raid_init);
342 module_exit(raid_exit);
343 MODULE_LICENSE("GPL");
344 MODULE_ALIAS("md-personality-10"); /* faulty */
345 MODULE_ALIAS("md-faulty");
346 MODULE_ALIAS("md-level--5");
347
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