2 * faulty.c : Multiple Devices driver for Linux
4 * Copyright (C) 2004 Neil Brown
6 * fautly-device-simulator personality for md
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)
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.
21 * The "faulty" personality causes some requests to fail.
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
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.
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 "0".
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.
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 */
55 #define ClearErrors 31
56 #define ClearFaults 30
58 #define AllPersist 100 /* internal use only */
65 #include <linux/raid/md.h>
68 static int faulty_fail(struct bio *bio, unsigned int bytes_done, int error)
70 struct bio *b = bio->bi_private;
72 b->bi_size = bio->bi_size;
73 b->bi_sector = bio->bi_sector;
75 if (bio->bi_size == 0)
78 clear_bit(BIO_UPTODATE, &b->bi_flags);
79 return (b->bi_end_io)(b, bytes_done, -EIO);
82 typedef struct faulty_conf {
84 atomic_t counters[Modes];
85 sector_t faults[MaxFault];
91 static int check_mode(conf_t *conf, int mode)
93 if (conf->period[mode] == 0 &&
94 atomic_read(&conf->counters[mode]) <= 0)
95 return 0; /* no failure, no decrement */
98 if (atomic_dec_and_test(&conf->counters[mode])) {
99 if (conf->period[mode])
100 atomic_set(&conf->counters[mode], conf->period[mode]);
106 static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
108 /* If we find a ReadFixable sector, we fix it ... */
110 for (i=0; i<conf->nfaults; i++)
111 if (conf->faults[i] >= start &&
112 conf->faults[i] < end) {
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;
121 case AllPersist*2+READ:
122 case AllPersist*2+WRITE: return 1;
130 static void add_sector(conf_t *conf, sector_t start, int mode)
133 int n = conf->nfaults;
134 for (i=0; i<conf->nfaults; i++)
135 if (conf->faults[i] == start) {
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;
143 conf->modes[i] = WritePersistent;
146 if (conf->modes[i] == WritePersistent)
147 conf->modes[i] = AllPersist;
149 conf->modes[i] = ReadPersistent;
152 if (conf->modes[i] == WritePersistent ||
153 conf->modes[i] == ReadPersistent)
154 conf->modes[i] = AllPersist;
156 conf->modes[i] = ReadFixable;
159 } else if (conf->modes[i] == NoPersist)
164 conf->faults[n] = start;
165 conf->modes[n] = mode;
166 if (conf->nfaults == n)
170 static int make_request(request_queue_t *q, struct bio *bio)
172 mddev_t *mddev = q->queuedata;
173 conf_t *conf = (conf_t*)mddev->private;
176 if (bio->bi_rw & 1) {
178 if (atomic_read(&conf->counters[WriteAll])) {
179 /* special case - don't decrement, don't generic_make_request,
180 * just fail immediately
182 bio_endio(bio, bio->bi_size, -EIO);
186 if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
189 if (check_mode(conf, WritePersistent)) {
190 add_sector(conf, bio->bi_sector, WritePersistent);
193 if (check_mode(conf, WriteTransient))
197 if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
200 if (check_mode(conf, ReadTransient))
202 if (check_mode(conf, ReadPersistent)) {
203 add_sector(conf, bio->bi_sector, ReadPersistent);
206 if (check_mode(conf, ReadFixable)) {
207 add_sector(conf, bio->bi_sector, ReadFixable);
212 struct bio *b = bio_clone(bio, GFP_NOIO);
213 b->bi_bdev = conf->rdev->bdev;
215 b->bi_end_io = faulty_fail;
216 generic_make_request(b);
219 bio->bi_bdev = conf->rdev->bdev;
224 static void status(struct seq_file *seq, mddev_t *mddev)
226 conf_t *conf = (conf_t*)mddev->private;
229 if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
230 seq_printf(seq, " WriteTransient=%d(%d)",
231 n, conf->period[WriteTransient]);
233 if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
234 seq_printf(seq, " ReadTransient=%d(%d)",
235 n, conf->period[ReadTransient]);
237 if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
238 seq_printf(seq, " WritePersistent=%d(%d)",
239 n, conf->period[WritePersistent]);
241 if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
242 seq_printf(seq, " ReadPersistent=%d(%d)",
243 n, conf->period[ReadPersistent]);
246 if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
247 seq_printf(seq, " ReadFixable=%d(%d)",
248 n, conf->period[ReadFixable]);
250 if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
251 seq_printf(seq, " WriteAll");
253 seq_printf(seq, " nfaults=%d", conf->nfaults);
257 static int reconfig(mddev_t *mddev, int layout, int chunk_size)
259 int mode = layout & ModeMask;
260 int count = layout >> ModeShift;
261 conf_t *conf = mddev->private;
263 if (chunk_size != -1)
267 if (mode == ClearFaults)
269 else if (mode == ClearErrors) {
271 for (i=0 ; i < Modes ; i++) {
273 atomic_set(&conf->counters[i], 0);
275 } else if (mode < Modes) {
276 conf->period[mode] = count;
278 atomic_set(&conf->counters[mode], count);
281 mddev->layout = -1; /* makes sure further changes come through */
285 static int run(mddev_t *mddev)
288 struct list_head *tmp;
291 conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
293 for (i=0; i<Modes; i++) {
294 atomic_set(&conf->counters[i], 0);
299 ITERATE_RDEV(mddev, rdev, tmp)
302 mddev->array_size = mddev->size;
303 mddev->private = conf;
305 reconfig(mddev, mddev->layout, -1);
310 static int stop(mddev_t *mddev)
312 conf_t *conf = (conf_t *)mddev->private;
315 mddev->private = NULL;
319 static mdk_personality_t faulty_personality =
322 .owner = THIS_MODULE,
323 .make_request = make_request,
327 .reconfig = reconfig,
330 static int __init raid_init(void)
332 return register_md_personality(FAULTY, &faulty_personality);
335 static void raid_exit(void)
337 unregister_md_personality(FAULTY);
340 module_init(raid_init);
341 module_exit(raid_exit);
342 MODULE_LICENSE("GPL");
343 MODULE_ALIAS("md-personality-10"); /* faulty */