Merge branch 'parisc' from /home/kyle/repos/parisc-2.6.git
[linux-2.6] / drivers / md / faulty.c
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 "0".
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_data_dir(bio) == WRITE) {
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");