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
42struct per_bio_data {
43	bool bio_submitted;
44};
45
46static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
47			  struct dm_target *ti)
48{
49	int r;
50	unsigned argc;
51	const char *arg_name;
52
53	static struct dm_arg _args[] = {
54		{0, 6, "Invalid number of feature args"},
55		{1, UINT_MAX, "Invalid corrupt bio byte"},
56		{0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
57		{0, UINT_MAX, "Invalid corrupt bio flags mask"},
58	};
59
60	/* No feature arguments supplied. */
61	if (!as->argc)
62		return 0;
63
64	r = dm_read_arg_group(_args, as, &argc, &ti->error);
65	if (r)
66		return r;
67
68	while (argc) {
69		arg_name = dm_shift_arg(as);
70		argc--;
71
72		/*
73		 * drop_writes
74		 */
75		if (!strcasecmp(arg_name, "drop_writes")) {
76			if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
77				ti->error = "Feature drop_writes duplicated";
78				return -EINVAL;
79			}
80
81			continue;
82		}
83
84		/*
85		 * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
86		 */
87		if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
88			if (!argc) {
89				ti->error = "Feature corrupt_bio_byte requires parameters";
90				return -EINVAL;
91			}
92
93			r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
94			if (r)
95				return r;
96			argc--;
97
98			/*
99			 * Direction r or w?
100			 */
101			arg_name = dm_shift_arg(as);
102			if (!strcasecmp(arg_name, "w"))
103				fc->corrupt_bio_rw = WRITE;
104			else if (!strcasecmp(arg_name, "r"))
105				fc->corrupt_bio_rw = READ;
106			else {
107				ti->error = "Invalid corrupt bio direction (r or w)";
108				return -EINVAL;
109			}
110			argc--;
111
112			/*
113			 * Value of byte (0-255) to write in place of correct one.
114			 */
115			r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
116			if (r)
117				return r;
118			argc--;
119
120			/*
121			 * Only corrupt bios with these flags set.
122			 */
123			r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
124			if (r)
125				return r;
126			argc--;
127
128			continue;
129		}
130
131		ti->error = "Unrecognised flakey feature requested";
132		return -EINVAL;
133	}
134
135	if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
136		ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
137		return -EINVAL;
138	}
139
140	return 0;
141}
142
143/*
144 * Construct a flakey mapping:
145 * <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
146 *
147 *   Feature args:
148 *     [drop_writes]
149 *     [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
150 *
151 *   Nth_byte starts from 1 for the first byte.
152 *   Direction is r for READ or w for WRITE.
153 *   bio_flags is ignored if 0.
154 */
155static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
156{
157	static struct dm_arg _args[] = {
158		{0, UINT_MAX, "Invalid up interval"},
159		{0, UINT_MAX, "Invalid down interval"},
160	};
161
162	int r;
163	struct flakey_c *fc;
164	unsigned long long tmpll;
165	struct dm_arg_set as;
166	const char *devname;
167	char dummy;
168
169	as.argc = argc;
170	as.argv = argv;
171
172	if (argc < 4) {
173		ti->error = "Invalid argument count";
174		return -EINVAL;
175	}
176
177	fc = kzalloc(sizeof(*fc), GFP_KERNEL);
178	if (!fc) {
179		ti->error = "Cannot allocate context";
180		return -ENOMEM;
181	}
182	fc->start_time = jiffies;
183
184	devname = dm_shift_arg(&as);
185
186	if (sscanf(dm_shift_arg(&as), "%llu%c", &tmpll, &dummy) != 1) {
187		ti->error = "Invalid device sector";
188		goto bad;
189	}
190	fc->start = tmpll;
191
192	r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
193	if (r)
194		goto bad;
195
196	r = dm_read_arg(_args, &as, &fc->down_interval, &ti->error);
197	if (r)
198		goto bad;
199
200	if (!(fc->up_interval + fc->down_interval)) {
201		ti->error = "Total (up + down) interval is zero";
202		goto bad;
203	}
204
205	if (fc->up_interval + fc->down_interval < fc->up_interval) {
206		ti->error = "Interval overflow";
207		goto bad;
208	}
209
210	r = parse_features(&as, fc, ti);
211	if (r)
212		goto bad;
213
214	if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev)) {
215		ti->error = "Device lookup failed";
216		goto bad;
217	}
218
219	ti->num_flush_bios = 1;
220	ti->num_discard_bios = 1;
221	ti->per_bio_data_size = sizeof(struct per_bio_data);
222	ti->private = fc;
223	return 0;
224
225bad:
226	kfree(fc);
227	return -EINVAL;
228}
229
230static void flakey_dtr(struct dm_target *ti)
231{
232	struct flakey_c *fc = ti->private;
233
234	dm_put_device(ti, fc->dev);
235	kfree(fc);
236}
237
238static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
239{
240	struct flakey_c *fc = ti->private;
241
242	return fc->start + dm_target_offset(ti, bi_sector);
243}
244
245static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
246{
247	struct flakey_c *fc = ti->private;
248
249	bio->bi_bdev = fc->dev->bdev;
250	if (bio_sectors(bio))
251		bio->bi_iter.bi_sector =
252			flakey_map_sector(ti, bio->bi_iter.bi_sector);
253}
254
255static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
256{
257	unsigned bio_bytes = bio_cur_bytes(bio);
258	char *data = bio_data(bio);
259
260	/*
261	 * Overwrite the Nth byte of the data returned.
262	 */
263	if (data && bio_bytes >= fc->corrupt_bio_byte) {
264		data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
265
266		DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
267			"(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
268			bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
269			(bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_rw,
270			(unsigned long long)bio->bi_iter.bi_sector, bio_bytes);
271	}
272}
273
274static int flakey_map(struct dm_target *ti, struct bio *bio)
275{
276	struct flakey_c *fc = ti->private;
277	unsigned elapsed;
278	struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
279	pb->bio_submitted = false;
280
281	/* Are we alive ? */
282	elapsed = (jiffies - fc->start_time) / HZ;
283	if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
284		/*
285		 * Flag this bio as submitted while down.
286		 */
287		pb->bio_submitted = true;
288
289		/*
290		 * Map reads as normal.
291		 */
292		if (bio_data_dir(bio) == READ)
293			goto map_bio;
294
295		/*
296		 * Drop writes?
297		 */
298		if (test_bit(DROP_WRITES, &fc->flags)) {
299			bio_endio(bio, 0);
300			return DM_MAPIO_SUBMITTED;
301		}
302
303		/*
304		 * Corrupt matching writes.
305		 */
306		if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
307			if (all_corrupt_bio_flags_match(bio, fc))
308				corrupt_bio_data(bio, fc);
309			goto map_bio;
310		}
311
312		/*
313		 * By default, error all I/O.
314		 */
315		return -EIO;
316	}
317
318map_bio:
319	flakey_map_bio(ti, bio);
320
321	return DM_MAPIO_REMAPPED;
322}
323
324static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
325{
326	struct flakey_c *fc = ti->private;
327	struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
328
329	/*
330	 * Corrupt successful READs while in down state.
331	 * If flags were specified, only corrupt those that match.
332	 */
333	if (fc->corrupt_bio_byte && !error && pb->bio_submitted &&
334	    (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
335	    all_corrupt_bio_flags_match(bio, fc))
336		corrupt_bio_data(bio, fc);
337
338	return error;
339}
340
341static void flakey_status(struct dm_target *ti, status_type_t type,
342			  unsigned status_flags, char *result, unsigned maxlen)
343{
344	unsigned sz = 0;
345	struct flakey_c *fc = ti->private;
346	unsigned drop_writes;
347
348	switch (type) {
349	case STATUSTYPE_INFO:
350		result[0] = '\0';
351		break;
352
353	case STATUSTYPE_TABLE:
354		DMEMIT("%s %llu %u %u ", fc->dev->name,
355		       (unsigned long long)fc->start, fc->up_interval,
356		       fc->down_interval);
357
358		drop_writes = test_bit(DROP_WRITES, &fc->flags);
359		DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
360
361		if (drop_writes)
362			DMEMIT("drop_writes ");
363
364		if (fc->corrupt_bio_byte)
365			DMEMIT("corrupt_bio_byte %u %c %u %u ",
366			       fc->corrupt_bio_byte,
367			       (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
368			       fc->corrupt_bio_value, fc->corrupt_bio_flags);
369
370		break;
371	}
372}
373
374static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
375{
376	struct flakey_c *fc = ti->private;
377	struct dm_dev *dev = fc->dev;
378	int r = 0;
379
380	/*
381	 * Only pass ioctls through if the device sizes match exactly.
382	 */
383	if (fc->start ||
384	    ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
385		r = scsi_verify_blk_ioctl(NULL, cmd);
386
387	return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
388}
389
390static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
391			struct bio_vec *biovec, int max_size)
392{
393	struct flakey_c *fc = ti->private;
394	struct request_queue *q = bdev_get_queue(fc->dev->bdev);
395
396	if (!q->merge_bvec_fn)
397		return max_size;
398
399	bvm->bi_bdev = fc->dev->bdev;
400	bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
401
402	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
403}
404
405static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
406{
407	struct flakey_c *fc = ti->private;
408
409	return fn(ti, fc->dev, fc->start, ti->len, data);
410}
411
412static struct target_type flakey_target = {
413	.name   = "flakey",
414	.version = {1, 3, 1},
415	.module = THIS_MODULE,
416	.ctr    = flakey_ctr,
417	.dtr    = flakey_dtr,
418	.map    = flakey_map,
419	.end_io = flakey_end_io,
420	.status = flakey_status,
421	.ioctl	= flakey_ioctl,
422	.merge	= flakey_merge,
423	.iterate_devices = flakey_iterate_devices,
424};
425
426static int __init dm_flakey_init(void)
427{
428	int r = dm_register_target(&flakey_target);
429
430	if (r < 0)
431		DMERR("register failed %d", r);
432
433	return r;
434}
435
436static void __exit dm_flakey_exit(void)
437{
438	dm_unregister_target(&flakey_target);
439}
440
441/* Module hooks */
442module_init(dm_flakey_init);
443module_exit(dm_flakey_exit);
444
445MODULE_DESCRIPTION(DM_NAME " flakey target");
446MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
447MODULE_LICENSE("GPL");
448