1 /*
2 linear.c : Multiple Devices driver for Linux
3 Copyright (C) 1994-96 Marc ZYNGIER
4 <zyngier@ufr-info-p7.ibp.fr> or
5 <maz@gloups.fdn.fr>
6
7 Linear mode management functions.
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 #include <linux/raid/linear.h>
20
21 /*
22 * find which device holds a particular offset
23 */
which_dev(mddev_t * mddev,sector_t sector)24 static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
25 {
26 dev_info_t *hash;
27 linear_conf_t *conf = mddev_to_conf(mddev);
28 sector_t idx = sector >> conf->sector_shift;
29
30 /*
31 * sector_div(a,b) returns the remainer and sets a to a/b
32 */
33 (void)sector_div(idx, conf->spacing);
34 hash = conf->hash_table[idx];
35
36 while (sector >= hash->num_sectors + hash->start_sector)
37 hash++;
38 return hash;
39 }
40
41 /**
42 * linear_mergeable_bvec -- tell bio layer if two requests can be merged
43 * @q: request queue
44 * @bvm: properties of new bio
45 * @biovec: the request that could be merged to it.
46 *
47 * Return amount of bytes we can take at this offset
48 */
linear_mergeable_bvec(struct request_queue * q,struct bvec_merge_data * bvm,struct bio_vec * biovec)49 static int linear_mergeable_bvec(struct request_queue *q,
50 struct bvec_merge_data *bvm,
51 struct bio_vec *biovec)
52 {
53 mddev_t *mddev = q->queuedata;
54 dev_info_t *dev0;
55 unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
56 sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
57
58 dev0 = which_dev(mddev, sector);
59 maxsectors = dev0->num_sectors - (sector - dev0->start_sector);
60
61 if (maxsectors < bio_sectors)
62 maxsectors = 0;
63 else
64 maxsectors -= bio_sectors;
65
66 if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
67 return biovec->bv_len;
68 /* The bytes available at this offset could be really big,
69 * so we cap at 2^31 to avoid overflow */
70 if (maxsectors > (1 << (31-9)))
71 return 1<<31;
72 return maxsectors << 9;
73 }
74
linear_unplug(struct request_queue * q)75 static void linear_unplug(struct request_queue *q)
76 {
77 mddev_t *mddev = q->queuedata;
78 linear_conf_t *conf = mddev_to_conf(mddev);
79 int i;
80
81 for (i=0; i < mddev->raid_disks; i++) {
82 struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
83 blk_unplug(r_queue);
84 }
85 }
86
linear_congested(void * data,int bits)87 static int linear_congested(void *data, int bits)
88 {
89 mddev_t *mddev = data;
90 linear_conf_t *conf = mddev_to_conf(mddev);
91 int i, ret = 0;
92
93 for (i = 0; i < mddev->raid_disks && !ret ; i++) {
94 struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
95 ret |= bdi_congested(&q->backing_dev_info, bits);
96 }
97 return ret;
98 }
99
linear_conf(mddev_t * mddev,int raid_disks)100 static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
101 {
102 linear_conf_t *conf;
103 dev_info_t **table;
104 mdk_rdev_t *rdev;
105 int i, nb_zone, cnt;
106 sector_t min_sectors;
107 sector_t curr_sector;
108
109 conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
110 GFP_KERNEL);
111 if (!conf)
112 return NULL;
113
114 cnt = 0;
115 conf->array_sectors = 0;
116
117 list_for_each_entry(rdev, &mddev->disks, same_set) {
118 int j = rdev->raid_disk;
119 dev_info_t *disk = conf->disks + j;
120
121 if (j < 0 || j >= raid_disks || disk->rdev) {
122 printk("linear: disk numbering problem. Aborting!\n");
123 goto out;
124 }
125
126 disk->rdev = rdev;
127
128 blk_queue_stack_limits(mddev->queue,
129 rdev->bdev->bd_disk->queue);
130 /* as we don't honour merge_bvec_fn, we must never risk
131 * violating it, so limit ->max_sector to one PAGE, as
132 * a one page request is never in violation.
133 */
134 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
135 mddev->queue->max_sectors > (PAGE_SIZE>>9))
136 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
137
138 disk->num_sectors = rdev->size * 2;
139 conf->array_sectors += rdev->size * 2;
140
141 cnt++;
142 }
143 if (cnt != raid_disks) {
144 printk("linear: not enough drives present. Aborting!\n");
145 goto out;
146 }
147
148 min_sectors = conf->array_sectors;
149 sector_div(min_sectors, PAGE_SIZE/sizeof(struct dev_info *));
150 if (min_sectors == 0)
151 min_sectors = 1;
152
153 /* min_sectors is the minimum spacing that will fit the hash
154 * table in one PAGE. This may be much smaller than needed.
155 * We find the smallest non-terminal set of consecutive devices
156 * that is larger than min_sectors and use the size of that as
157 * the actual spacing
158 */
159 conf->spacing = conf->array_sectors;
160 for (i=0; i < cnt-1 ; i++) {
161 sector_t tmp = 0;
162 int j;
163 for (j = i; j < cnt - 1 && tmp < min_sectors; j++)
164 tmp += conf->disks[j].num_sectors;
165 if (tmp >= min_sectors && tmp < conf->spacing)
166 conf->spacing = tmp;
167 }
168
169 /* spacing may be too large for sector_div to work with,
170 * so we might need to pre-shift
171 */
172 conf->sector_shift = 0;
173 if (sizeof(sector_t) > sizeof(u32)) {
174 sector_t space = conf->spacing;
175 while (space > (sector_t)(~(u32)0)) {
176 space >>= 1;
177 conf->sector_shift++;
178 }
179 }
180 /*
181 * This code was restructured to work around a gcc-2.95.3 internal
182 * compiler error. Alter it with care.
183 */
184 {
185 sector_t sz;
186 unsigned round;
187 unsigned long base;
188
189 sz = conf->array_sectors >> conf->sector_shift;
190 sz += 1; /* force round-up */
191 base = conf->spacing >> conf->sector_shift;
192 round = sector_div(sz, base);
193 nb_zone = sz + (round ? 1 : 0);
194 }
195 BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
196
197 conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
198 GFP_KERNEL);
199 if (!conf->hash_table)
200 goto out;
201
202 /*
203 * Here we generate the linear hash table
204 * First calculate the device offsets.
205 */
206 conf->disks[0].start_sector = 0;
207 for (i = 1; i < raid_disks; i++)
208 conf->disks[i].start_sector =
209 conf->disks[i-1].start_sector +
210 conf->disks[i-1].num_sectors;
211
212 table = conf->hash_table;
213 i = 0;
214 for (curr_sector = 0;
215 curr_sector < conf->array_sectors;
216 curr_sector += conf->spacing) {
217
218 while (i < raid_disks-1 &&
219 curr_sector >= conf->disks[i+1].start_sector)
220 i++;
221
222 *table ++ = conf->disks + i;
223 }
224
225 if (conf->sector_shift) {
226 conf->spacing >>= conf->sector_shift;
227 /* round spacing up so that when we divide by it,
228 * we err on the side of "too-low", which is safest.
229 */
230 conf->spacing++;
231 }
232
233 BUG_ON(table - conf->hash_table > nb_zone);
234
235 return conf;
236
237 out:
238 kfree(conf);
239 return NULL;
240 }
241
linear_run(mddev_t * mddev)242 static int linear_run (mddev_t *mddev)
243 {
244 linear_conf_t *conf;
245
246 mddev->queue->queue_lock = &mddev->queue->__queue_lock;
247 conf = linear_conf(mddev, mddev->raid_disks);
248
249 if (!conf)
250 return 1;
251 mddev->private = conf;
252 mddev->array_sectors = conf->array_sectors;
253
254 blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
255 mddev->queue->unplug_fn = linear_unplug;
256 mddev->queue->backing_dev_info.congested_fn = linear_congested;
257 mddev->queue->backing_dev_info.congested_data = mddev;
258 return 0;
259 }
260
linear_add(mddev_t * mddev,mdk_rdev_t * rdev)261 static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
262 {
263 /* Adding a drive to a linear array allows the array to grow.
264 * It is permitted if the new drive has a matching superblock
265 * already on it, with raid_disk equal to raid_disks.
266 * It is achieved by creating a new linear_private_data structure
267 * and swapping it in in-place of the current one.
268 * The current one is never freed until the array is stopped.
269 * This avoids races.
270 */
271 linear_conf_t *newconf;
272
273 if (rdev->saved_raid_disk != mddev->raid_disks)
274 return -EINVAL;
275
276 rdev->raid_disk = rdev->saved_raid_disk;
277
278 newconf = linear_conf(mddev,mddev->raid_disks+1);
279
280 if (!newconf)
281 return -ENOMEM;
282
283 newconf->prev = mddev_to_conf(mddev);
284 mddev->private = newconf;
285 mddev->raid_disks++;
286 mddev->array_sectors = newconf->array_sectors;
287 set_capacity(mddev->gendisk, mddev->array_sectors);
288 return 0;
289 }
290
linear_stop(mddev_t * mddev)291 static int linear_stop (mddev_t *mddev)
292 {
293 linear_conf_t *conf = mddev_to_conf(mddev);
294
295 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
296 do {
297 linear_conf_t *t = conf->prev;
298 kfree(conf->hash_table);
299 kfree(conf);
300 conf = t;
301 } while (conf);
302
303 return 0;
304 }
305
linear_make_request(struct request_queue * q,struct bio * bio)306 static int linear_make_request (struct request_queue *q, struct bio *bio)
307 {
308 const int rw = bio_data_dir(bio);
309 mddev_t *mddev = q->queuedata;
310 dev_info_t *tmp_dev;
311 int cpu;
312
313 if (unlikely(bio_barrier(bio))) {
314 bio_endio(bio, -EOPNOTSUPP);
315 return 0;
316 }
317
318 cpu = part_stat_lock();
319 part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
320 part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
321 bio_sectors(bio));
322 part_stat_unlock();
323
324 tmp_dev = which_dev(mddev, bio->bi_sector);
325
326 if (unlikely(bio->bi_sector >= (tmp_dev->num_sectors +
327 tmp_dev->start_sector)
328 || (bio->bi_sector <
329 tmp_dev->start_sector))) {
330 char b[BDEVNAME_SIZE];
331
332 printk("linear_make_request: Sector %llu out of bounds on "
333 "dev %s: %llu sectors, offset %llu\n",
334 (unsigned long long)bio->bi_sector,
335 bdevname(tmp_dev->rdev->bdev, b),
336 (unsigned long long)tmp_dev->num_sectors,
337 (unsigned long long)tmp_dev->start_sector);
338 bio_io_error(bio);
339 return 0;
340 }
341 if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
342 tmp_dev->start_sector + tmp_dev->num_sectors)) {
343 /* This bio crosses a device boundary, so we have to
344 * split it.
345 */
346 struct bio_pair *bp;
347
348 bp = bio_split(bio,
349 tmp_dev->start_sector + tmp_dev->num_sectors
350 - bio->bi_sector);
351
352 if (linear_make_request(q, &bp->bio1))
353 generic_make_request(&bp->bio1);
354 if (linear_make_request(q, &bp->bio2))
355 generic_make_request(&bp->bio2);
356 bio_pair_release(bp);
357 return 0;
358 }
359
360 bio->bi_bdev = tmp_dev->rdev->bdev;
361 bio->bi_sector = bio->bi_sector - tmp_dev->start_sector
362 + tmp_dev->rdev->data_offset;
363
364 return 1;
365 }
366
linear_status(struct seq_file * seq,mddev_t * mddev)367 static void linear_status (struct seq_file *seq, mddev_t *mddev)
368 {
369
370 seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
371 }
372
373
374 static struct mdk_personality linear_personality =
375 {
376 .name = "linear",
377 .level = LEVEL_LINEAR,
378 .owner = THIS_MODULE,
379 .make_request = linear_make_request,
380 .run = linear_run,
381 .stop = linear_stop,
382 .status = linear_status,
383 .hot_add_disk = linear_add,
384 };
385
linear_init(void)386 static int __init linear_init (void)
387 {
388 return register_md_personality (&linear_personality);
389 }
390
linear_exit(void)391 static void linear_exit (void)
392 {
393 unregister_md_personality (&linear_personality);
394 }
395
396
397 module_init(linear_init);
398 module_exit(linear_exit);
399 MODULE_LICENSE("GPL");
400 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
401 MODULE_ALIAS("md-linear");
402 MODULE_ALIAS("md-level--1");
403