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 recurrence 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/blkdev.h>
66#include <linux/module.h>
67#include <linux/raid/md_u.h>
68#include <linux/slab.h>
69#include "md.h"
70#include <linux/seq_file.h>
71
72
73static void faulty_fail(struct bio *bio, int error)
74{
75	struct bio *b = bio->bi_private;
76
77	b->bi_size = bio->bi_size;
78	b->bi_sector = bio->bi_sector;
79
80	bio_put(bio);
81
82	bio_io_error(b);
83}
84
85struct faulty_conf {
86	int period[Modes];
87	atomic_t counters[Modes];
88	sector_t faults[MaxFault];
89	int	modes[MaxFault];
90	int nfaults;
91	struct md_rdev *rdev;
92};
93
94static int check_mode(struct faulty_conf *conf, int mode)
95{
96	if (conf->period[mode] == 0 &&
97	    atomic_read(&conf->counters[mode]) <= 0)
98		return 0; /* no failure, no decrement */
99
100
101	if (atomic_dec_and_test(&conf->counters[mode])) {
102		if (conf->period[mode])
103			atomic_set(&conf->counters[mode], conf->period[mode]);
104		return 1;
105	}
106	return 0;
107}
108
109static int check_sector(struct faulty_conf *conf, sector_t start, sector_t end, int dir)
110{
111	/* If we find a ReadFixable sector, we fix it ... */
112	int i;
113	for (i=0; i<conf->nfaults; i++)
114		if (conf->faults[i] >= start &&
115		    conf->faults[i] < end) {
116			/* found it ... */
117			switch (conf->modes[i] * 2 + dir) {
118			case WritePersistent*2+WRITE: return 1;
119			case ReadPersistent*2+READ: return 1;
120			case ReadFixable*2+READ: return 1;
121			case ReadFixable*2+WRITE:
122				conf->modes[i] = NoPersist;
123				return 0;
124			case AllPersist*2+READ:
125			case AllPersist*2+WRITE: return 1;
126			default:
127				return 0;
128			}
129		}
130	return 0;
131}
132
133static void add_sector(struct faulty_conf *conf, sector_t start, int mode)
134{
135	int i;
136	int n = conf->nfaults;
137	for (i=0; i<conf->nfaults; i++)
138		if (conf->faults[i] == start) {
139			switch(mode) {
140			case NoPersist: conf->modes[i] = mode; return;
141			case WritePersistent:
142				if (conf->modes[i] == ReadPersistent ||
143				    conf->modes[i] == ReadFixable)
144					conf->modes[i] = AllPersist;
145				else
146					conf->modes[i] = WritePersistent;
147				return;
148			case ReadPersistent:
149				if (conf->modes[i] == WritePersistent)
150					conf->modes[i] = AllPersist;
151				else
152					conf->modes[i] = ReadPersistent;
153				return;
154			case ReadFixable:
155				if (conf->modes[i] == WritePersistent ||
156				    conf->modes[i] == ReadPersistent)
157					conf->modes[i] = AllPersist;
158				else
159					conf->modes[i] = ReadFixable;
160				return;
161			}
162		} else if (conf->modes[i] == NoPersist)
163			n = i;
164
165	if (n >= MaxFault)
166		return;
167	conf->faults[n] = start;
168	conf->modes[n] = mode;
169	if (conf->nfaults == n)
170		conf->nfaults = n+1;
171}
172
173static void make_request(struct mddev *mddev, struct bio *bio)
174{
175	struct faulty_conf *conf = mddev->private;
176	int failit = 0;
177
178	if (bio_data_dir(bio) == WRITE) {
179		/* write request */
180		if (atomic_read(&conf->counters[WriteAll])) {
181			/* special case - don't decrement, don't generic_make_request,
182			 * just fail immediately
183			 */
184			bio_endio(bio, -EIO);
185			return;
186		}
187
188		if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
189				 WRITE))
190			failit = 1;
191		if (check_mode(conf, WritePersistent)) {
192			add_sector(conf, bio->bi_sector, WritePersistent);
193			failit = 1;
194		}
195		if (check_mode(conf, WriteTransient))
196			failit = 1;
197	} else {
198		/* read request */
199		if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
200				 READ))
201			failit = 1;
202		if (check_mode(conf, ReadTransient))
203			failit = 1;
204		if (check_mode(conf, ReadPersistent)) {
205			add_sector(conf, bio->bi_sector, ReadPersistent);
206			failit = 1;
207		}
208		if (check_mode(conf, ReadFixable)) {
209			add_sector(conf, bio->bi_sector, ReadFixable);
210			failit = 1;
211		}
212	}
213	if (failit) {
214		struct bio *b = bio_clone_mddev(bio, GFP_NOIO, mddev);
215
216		b->bi_bdev = conf->rdev->bdev;
217		b->bi_private = bio;
218		b->bi_end_io = faulty_fail;
219		bio = b;
220	} else
221		bio->bi_bdev = conf->rdev->bdev;
222
223	generic_make_request(bio);
224}
225
226static void status(struct seq_file *seq, struct mddev *mddev)
227{
228	struct faulty_conf *conf = mddev->private;
229	int n;
230
231	if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
232		seq_printf(seq, " WriteTransient=%d(%d)",
233			   n, conf->period[WriteTransient]);
234
235	if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
236		seq_printf(seq, " ReadTransient=%d(%d)",
237			   n, conf->period[ReadTransient]);
238
239	if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
240		seq_printf(seq, " WritePersistent=%d(%d)",
241			   n, conf->period[WritePersistent]);
242
243	if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
244		seq_printf(seq, " ReadPersistent=%d(%d)",
245			   n, conf->period[ReadPersistent]);
246
247
248	if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
249		seq_printf(seq, " ReadFixable=%d(%d)",
250			   n, conf->period[ReadFixable]);
251
252	if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
253		seq_printf(seq, " WriteAll");
254
255	seq_printf(seq, " nfaults=%d", conf->nfaults);
256}
257
258
259static int reshape(struct mddev *mddev)
260{
261	int mode = mddev->new_layout & ModeMask;
262	int count = mddev->new_layout >> ModeShift;
263	struct faulty_conf *conf = mddev->private;
264
265	if (mddev->new_layout < 0)
266		return 0;
267
268	/* new layout */
269	if (mode == ClearFaults)
270		conf->nfaults = 0;
271	else if (mode == ClearErrors) {
272		int i;
273		for (i=0 ; i < Modes ; i++) {
274			conf->period[i] = 0;
275			atomic_set(&conf->counters[i], 0);
276		}
277	} else if (mode < Modes) {
278		conf->period[mode] = count;
279		if (!count) count++;
280		atomic_set(&conf->counters[mode], count);
281	} else
282		return -EINVAL;
283	mddev->new_layout = -1;
284	mddev->layout = -1; /* makes sure further changes come through */
285	return 0;
286}
287
288static sector_t faulty_size(struct mddev *mddev, sector_t sectors, int raid_disks)
289{
290	WARN_ONCE(raid_disks,
291		  "%s does not support generic reshape\n", __func__);
292
293	if (sectors == 0)
294		return mddev->dev_sectors;
295
296	return sectors;
297}
298
299static int run(struct mddev *mddev)
300{
301	struct md_rdev *rdev;
302	int i;
303	struct faulty_conf *conf;
304
305	if (md_check_no_bitmap(mddev))
306		return -EINVAL;
307
308	conf = kmalloc(sizeof(*conf), GFP_KERNEL);
309	if (!conf)
310		return -ENOMEM;
311
312	for (i=0; i<Modes; i++) {
313		atomic_set(&conf->counters[i], 0);
314		conf->period[i] = 0;
315	}
316	conf->nfaults = 0;
317
318	rdev_for_each(rdev, mddev)
319		conf->rdev = rdev;
320
321	md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
322	mddev->private = conf;
323
324	reshape(mddev);
325
326	return 0;
327}
328
329static int stop(struct mddev *mddev)
330{
331	struct faulty_conf *conf = mddev->private;
332
333	kfree(conf);
334	mddev->private = NULL;
335	return 0;
336}
337
338static struct md_personality faulty_personality =
339{
340	.name		= "faulty",
341	.level		= LEVEL_FAULTY,
342	.owner		= THIS_MODULE,
343	.make_request	= make_request,
344	.run		= run,
345	.stop		= stop,
346	.status		= status,
347	.check_reshape	= reshape,
348	.size		= faulty_size,
349};
350
351static int __init raid_init(void)
352{
353	return register_md_personality(&faulty_personality);
354}
355
356static void raid_exit(void)
357{
358	unregister_md_personality(&faulty_personality);
359}
360
361module_init(raid_init);
362module_exit(raid_exit);
363MODULE_LICENSE("GPL");
364MODULE_DESCRIPTION("Fault injection personality for MD");
365MODULE_ALIAS("md-personality-10"); /* faulty */
366MODULE_ALIAS("md-faulty");
367MODULE_ALIAS("md-level--5");
368