Root/drivers/md/dm-flakey.c

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 linear 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_sector = flakey_map_sector(ti, bio->bi_sector);
252}
253
254static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
255{
256    unsigned bio_bytes = bio_cur_bytes(bio);
257    char *data = bio_data(bio);
258
259    /*
260     * Overwrite the Nth byte of the data returned.
261     */
262    if (data && bio_bytes >= fc->corrupt_bio_byte) {
263        data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
264
265        DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
266            "(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
267            bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
268            (bio_data_dir(bio) == WRITE) ? 'w' : 'r',
269            bio->bi_rw, (unsigned long long)bio->bi_sector, bio_bytes);
270    }
271}
272
273static int flakey_map(struct dm_target *ti, struct bio *bio)
274{
275    struct flakey_c *fc = ti->private;
276    unsigned elapsed;
277    struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
278    pb->bio_submitted = false;
279
280    /* Are we alive ? */
281    elapsed = (jiffies - fc->start_time) / HZ;
282    if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
283        /*
284         * Flag this bio as submitted while down.
285         */
286        pb->bio_submitted = true;
287
288        /*
289         * Map reads as normal.
290         */
291        if (bio_data_dir(bio) == READ)
292            goto map_bio;
293
294        /*
295         * Drop writes?
296         */
297        if (test_bit(DROP_WRITES, &fc->flags)) {
298            bio_endio(bio, 0);
299            return DM_MAPIO_SUBMITTED;
300        }
301
302        /*
303         * Corrupt matching writes.
304         */
305        if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
306            if (all_corrupt_bio_flags_match(bio, fc))
307                corrupt_bio_data(bio, fc);
308            goto map_bio;
309        }
310
311        /*
312         * By default, error all I/O.
313         */
314        return -EIO;
315    }
316
317map_bio:
318    flakey_map_bio(ti, bio);
319
320    return DM_MAPIO_REMAPPED;
321}
322
323static int flakey_end_io(struct dm_target *ti, struct bio *bio, int error)
324{
325    struct flakey_c *fc = ti->private;
326    struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
327
328    /*
329     * Corrupt successful READs while in down state.
330     * If flags were specified, only corrupt those that match.
331     */
332    if (fc->corrupt_bio_byte && !error && pb->bio_submitted &&
333        (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
334        all_corrupt_bio_flags_match(bio, fc))
335        corrupt_bio_data(bio, fc);
336
337    return error;
338}
339
340static void flakey_status(struct dm_target *ti, status_type_t type,
341              unsigned status_flags, char *result, unsigned maxlen)
342{
343    unsigned sz = 0;
344    struct flakey_c *fc = ti->private;
345    unsigned drop_writes;
346
347    switch (type) {
348    case STATUSTYPE_INFO:
349        result[0] = '\0';
350        break;
351
352    case STATUSTYPE_TABLE:
353        DMEMIT("%s %llu %u %u ", fc->dev->name,
354               (unsigned long long)fc->start, fc->up_interval,
355               fc->down_interval);
356
357        drop_writes = test_bit(DROP_WRITES, &fc->flags);
358        DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
359
360        if (drop_writes)
361            DMEMIT("drop_writes ");
362
363        if (fc->corrupt_bio_byte)
364            DMEMIT("corrupt_bio_byte %u %c %u %u ",
365                   fc->corrupt_bio_byte,
366                   (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
367                   fc->corrupt_bio_value, fc->corrupt_bio_flags);
368
369        break;
370    }
371}
372
373static int flakey_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg)
374{
375    struct flakey_c *fc = ti->private;
376    struct dm_dev *dev = fc->dev;
377    int r = 0;
378
379    /*
380     * Only pass ioctls through if the device sizes match exactly.
381     */
382    if (fc->start ||
383        ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
384        r = scsi_verify_blk_ioctl(NULL, cmd);
385
386    return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
387}
388
389static int flakey_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
390            struct bio_vec *biovec, int max_size)
391{
392    struct flakey_c *fc = ti->private;
393    struct request_queue *q = bdev_get_queue(fc->dev->bdev);
394
395    if (!q->merge_bvec_fn)
396        return max_size;
397
398    bvm->bi_bdev = fc->dev->bdev;
399    bvm->bi_sector = flakey_map_sector(ti, bvm->bi_sector);
400
401    return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
402}
403
404static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
405{
406    struct flakey_c *fc = ti->private;
407
408    return fn(ti, fc->dev, fc->start, ti->len, data);
409}
410
411static struct target_type flakey_target = {
412    .name = "flakey",
413    .version = {1, 3, 1},
414    .module = THIS_MODULE,
415    .ctr = flakey_ctr,
416    .dtr = flakey_dtr,
417    .map = flakey_map,
418    .end_io = flakey_end_io,
419    .status = flakey_status,
420    .ioctl = flakey_ioctl,
421    .merge = flakey_merge,
422    .iterate_devices = flakey_iterate_devices,
423};
424
425static int __init dm_flakey_init(void)
426{
427    int r = dm_register_target(&flakey_target);
428
429    if (r < 0)
430        DMERR("register failed %d", r);
431
432    return r;
433}
434
435static void __exit dm_flakey_exit(void)
436{
437    dm_unregister_target(&flakey_target);
438}
439
440/* Module hooks */
441module_init(dm_flakey_init);
442module_exit(dm_flakey_exit);
443
444MODULE_DESCRIPTION(DM_NAME " flakey target");
445MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
446MODULE_LICENSE("GPL");
447

Archive Download this file



interactive