dm-flakey.c revision 1212268fd9816e3b8801e57b896fceaec71969ad 
1/*
2 * Copyright (C) 2003 Sistina Software (UK) Limited.
3 * Copyright (C) 2004, 2010-2011 Red Hat, Inc. All rights reserved.
4 *
5 * This file is released under the GPL.
6 */
7
8#include <linux/device-mapper.h>
9
10#include <linux/module.h>
11#include <linux/init.h>
12#include <linux/blkdev.h>
13#include <linux/bio.h>
14#include <linux/slab.h>
15
16#define DM_MSG_PREFIX "flakey"
17
18#define all_corrupt_bio_flags_match(bio, fc)	\
19	(((bio)->bi_rw & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
20
21/*
22 * Flakey: Used for testing only, simulates intermittent,
23 * catastrophic device failure.
24 */
25struct flakey_c {
26	struct dm_dev *dev;
27	unsigned long start_time;
28	sector_t start;
29	unsigned up_interval;
30	unsigned down_interval;
31	unsigned long flags;
32	unsigned corrupt_bio_byte;
33	unsigned corrupt_bio_rw;
34	unsigned corrupt_bio_value;
35	unsigned corrupt_bio_flags;
36};
37
38enum feature_flag_bits {
39	DROP_WRITES
40};
41
42static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
43			  struct dm_target *ti)
44{
45	int r;
46	unsigned argc;
47	const char *arg_name;
48
49	static struct dm_arg _args[] = {
50		{0, 6, "Invalid number of feature args"},
51		{1, UINT_MAX, "Invalid corrupt bio byte"},
52		{0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
53		{0, UINT_MAX, "Invalid corrupt bio flags mask"},
54	};
55
56	/* No feature arguments supplied. */
57	if (!as->argc)
58		return 0;
59
60	r = dm_read_arg_group(_args, as, &argc, &ti->error);
61	if (r)
62		return r;
63
64	while (argc) {
65		arg_name = dm_shift_arg(as);
66		argc--;
67
68		/*
69		 * drop_writes
70		 */
71		if (!strcasecmp(arg_name, "drop_writes")) {
72			if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
73				ti->error = "Feature drop_writes duplicated";
74				return -EINVAL;
75			}
76
77			continue;
78		}
79
80		/*
81		 * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
82		 */
83		if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
84			if (!argc) {
85				ti->error = "Feature corrupt_bio_byte requires parameters";
86				return -EINVAL;
87			}
88
89			r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
90			if (r)
91				return r;
92			argc--;
93
94			/*
95			 * Direction r or w?
96			 */
97			arg_name = dm_shift_arg(as);
98			if (!strcasecmp(arg_name, "w"))
99				fc->corrupt_bio_rw = WRITE;
100			else if (!strcasecmp(arg_name, "r"))
101				fc->corrupt_bio_rw = READ;
102			else {
103				ti->error = "Invalid corrupt bio direction (r or w)";
104				return -EINVAL;
105			}
106			argc--;
107
108			/*
109			 * Value of byte (0-255) to write in place of correct one.
110			 */
111			r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
112			if (r)
113				return r;
114			argc--;
115
116			/*
117			 * Only corrupt bios with these flags set.
118			 */
119			r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
120			if (r)
121				return r;
122			argc--;
123
124			continue;
125		}
126
127		ti->error = "Unrecognised flakey feature requested";
128		return -EINVAL;
129	}
130
131	if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
132		ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
133		return -EINVAL;
134	}
135
136	return 0;
137}
138
139/*
140 * Construct a flakey mapping:
141 * <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
142 *
143 *   Feature args:
144 *     [drop_writes]
145 *     [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
146 *
147 *   Nth_byte starts from 1 for the first byte.
148 *   Direction is r for READ or w for WRITE.
149 *   bio_flags is ignored if 0.
150 */
151static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
152{
153	static struct dm_arg _args[] = {
154		{0, UINT_MAX, "Invalid up interval"},
155		{0, UINT_MAX, "Invalid down interval"},
156	};
157
158	int r;
159	struct flakey_c *fc;
160	unsigned long long tmpll;
161	struct dm_arg_set as;
162	const char *devname;
163
164	as.argc = argc;
165	as.argv = argv;
166
167	if (argc < 4) {
168		ti->error = "Invalid argument count";
169		return -EINVAL;
170	}
171
172	fc = kzalloc(sizeof(*fc), GFP_KERNEL);
173	if (!fc) {
174		ti->error = "Cannot allocate linear context";
175		return -ENOMEM;
176	}
177	fc->start_time = jiffies;
178
179	devname = dm_shift_arg(&as);
180
181	if (sscanf(dm_shift_arg(&as), "%llu", &tmpll) != 1) {
182		ti->error = "Invalid device sector";
183		goto bad;
184	}
185	fc->start = tmpll;
186
187	r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
188	if (r)
189		goto bad;
190
191	r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
192	if (r)
193		goto bad;
194
195	if (!(fc->up_interval + fc->down_interval)) {
196		ti->error = "Total (up + down) interval is zero";
197		goto bad;
198	}
199
200	if (fc->up_interval + fc->down_interval < fc->up_interval) {
201		ti->error = "Interval overflow";
202		goto bad;
203	}
204
205	r = parse_features(&as, fc, ti);
206	if (r)
207		goto bad;
208
209	if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev)) {
210		ti->error = "Device lookup failed";
211		goto bad;
212	}
213
214	ti->num_flush_requests = 1;
215	ti->num_discard_requests = 1;
216	ti->private = fc;
217	return 0;
218
219bad:
220	kfree(fc);
221	return -EINVAL;
222}
223
224static void flakey_dtr(struct dm_target *ti)
225{
226	struct flakey_c *fc = ti->private;
227
228	dm_put_device(ti, fc->dev);
229	kfree(fc);
230}
231
232static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
233{
234	struct flakey_c *fc = ti->private;
235
236	return fc->start + dm_target_offset(ti, bi_sector);
237}
238
239static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
240{
241	struct flakey_c *fc = ti->private;
242
243	bio->bi_bdev = fc->dev->bdev;
244	if (bio_sectors(bio))
245		bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
246}
247
248static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
249{
250	unsigned bio_bytes = bio_cur_bytes(bio);
251	char *data = bio_data(bio);
252
253	/*
254	 * Overwrite the Nth byte of the data returned.
255	 */
256	if (data && bio_bytes >= fc->corrupt_bio_byte) {
257		data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
258
259		DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
260			"(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
261			bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
262			(bio_data_dir(bio) == WRITE) ? 'w' : 'r',
263			bio->bi_rw, (unsigned long long)bio->bi_sector, bio_bytes);
264	}
265}
266
267static int flakey_map(struct dm_target *ti, struct bio *bio,
268		      union map_info *map_context)
269{
270	struct flakey_c *fc = ti->private;
271	unsigned elapsed;
272
273	/* Are we alive ? */
274	elapsed = (jiffies - fc->start_time) / HZ;
275	if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
276		/*
277		 * Flag this bio as submitted while down.
278		 */
279		map_context->ll = 1;
280
281		/*
282		 * Map reads as normal.
283		 */
284		if (bio_data_dir(bio) == READ)
285			goto map_bio;
286
287		/*
288		 * Drop writes?
289		 */
290		if (test_bit(DROP_WRITES, &fc->flags)) {
291			bio_endio(bio, 0);
292			return DM_MAPIO_SUBMITTED;
293		}
294
295		/*
296		 * Corrupt matching writes.
297		 */
298		if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
299			if (all_corrupt_bio_flags_match(bio, fc))
300				corrupt_bio_data(bio, fc);
301			goto map_bio;
302		}
303
304		/*
305		 * By default, error all I/O.
306		 */
307		return -EIO;
308	}
309
310map_bio:
311	flakey_map_bio(ti, bio);
312
313	return DM_MAPIO_REMAPPED;
314}
315
316static int flakey_end_io(struct dm_target *ti, struct bio *bio,
317			 int error, union map_info *map_context)
318{
319	struct flakey_c *fc = ti->private;
320	unsigned bio_submitted_while_down = map_context->ll;
321
322	/*
323	 * Corrupt successful READs while in down state.
324	 * If flags were specified, only corrupt those that match.
325	 */
326	if (fc->corrupt_bio_byte && !error && bio_submitted_while_down &&
327	    (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
328	    all_corrupt_bio_flags_match(bio, fc))
329		corrupt_bio_data(bio, fc);
330
331	return error;
332}
333
334static int flakey_status(struct dm_target *ti, status_type_t type,
335			 char *result, unsigned int maxlen)
336{
337	unsigned sz = 0;
338	struct flakey_c *fc = ti->private;
339	unsigned drop_writes;
340
341	switch (type) {
342	case STATUSTYPE_INFO:
343		result[0] = '\0';
344		break;
345
346	case STATUSTYPE_TABLE:
347		DMEMIT("%s %llu %u %u ", fc->dev->name,
348		       (unsigned long long)fc->start, fc->up_interval,
349		       fc->down_interval);
350
351		drop_writes = test_bit(DROP_WRITES, &fc->flags);
352		DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
353
354		if (drop_writes)
355			DMEMIT("drop_writes ");
356
357		if (fc->corrupt_bio_byte)
358			DMEMIT("corrupt_bio_byte %u %c %u %u ",
359			       fc->corrupt_bio_byte,
360			       (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
361			       fc->corrupt_bio_value, fc->corrupt_bio_flags);
362
363		break;
364	}
365	return 0;
366}
367
368static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
369{
370	struct flakey_c *fc = ti->private;
371	struct dm_dev *dev = fc->dev;
372	int r = 0;
373
374	/*
375	 * Only pass ioctls through if the device sizes match exactly.
376	 */
377	if (fc->start ||
378	    ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
379		r = scsi_verify_blk_ioctl(NULL, cmd);
380
381	return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
382}
383
384static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
385			struct bio_vec *biovec, int max_size)
386{
387	struct flakey_c *fc = ti->private;
388	struct request_queue *q = bdev_get_queue(fc->dev->bdev);
389
390	if (!q->merge_bvec_fn)
391		return max_size;
392
393	bvm->bi_bdev = fc->dev->bdev;
394	bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
395
396	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
397}
398
399static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
400{
401	struct flakey_c *fc = ti->private;
402
403	return fn(ti, fc->dev, fc->start, ti->len, data);
404}
405
406static struct target_type flakey_target = {
407	.name   = "flakey",
408	.version = {1, 2, 0},
409	.module = THIS_MODULE,
410	.ctr    = flakey_ctr,
411	.dtr    = flakey_dtr,
412	.map    = flakey_map,
413	.end_io = flakey_end_io,
414	.status = flakey_status,
415	.ioctl	= flakey_ioctl,
416	.merge	= flakey_merge,
417	.iterate_devices = flakey_iterate_devices,
418};
419
420static int __init dm_flakey_init(void)
421{
422	int r = dm_register_target(&flakey_target);
423
424	if (r < 0)
425		DMERR("register failed %d", r);
426
427	return r;
428}
429
430static void __exit dm_flakey_exit(void)
431{
432	dm_unregister_target(&flakey_target);
433}
434
435/* Module hooks */
436module_init(dm_flakey_init);
437module_exit(dm_flakey_exit);
438
439MODULE_DESCRIPTION(DM_NAME " flakey target");
440MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
441MODULE_LICENSE("GPL");
442