2 linear.c : Multiple Devices driver for Linux
3 Copyright (C) 1994-96 Marc ZYNGIER
4 <zyngier@ufr-info-p7.ibp.fr> or
7 Linear mode management functions.
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)
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.
19 #include <linux/module.h>
21 #include <linux/raid/md.h>
22 #include <linux/slab.h>
23 #include <linux/raid/linear.h>
25 #define MAJOR_NR MD_MAJOR
27 #define MD_PERSONALITY
30 * find which device holds a particular offset
32 static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
35 linear_conf_t *conf = mddev_to_conf(mddev);
36 sector_t block = sector >> 1;
39 * sector_div(a,b) returns the remainer and sets a to a/b
41 block >>= conf->preshift;
42 (void)sector_div(block, conf->hash_spacing);
43 hash = conf->hash_table[block];
45 while ((sector>>1) >= (hash->size + hash->offset))
51 * linear_mergeable_bvec -- tell bio layer if two requests can be merged
53 * @bvm: properties of new bio
54 * @biovec: the request that could be merged to it.
56 * Return amount of bytes we can take at this offset
58 static int linear_mergeable_bvec(struct request_queue *q,
59 struct bvec_merge_data *bvm,
60 struct bio_vec *biovec)
62 mddev_t *mddev = q->queuedata;
64 unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
65 sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
67 dev0 = which_dev(mddev, sector);
68 maxsectors = (dev0->size << 1) - (sector - (dev0->offset<<1));
70 if (maxsectors < bio_sectors)
73 maxsectors -= bio_sectors;
75 if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
76 return biovec->bv_len;
77 /* The bytes available at this offset could be really big,
78 * so we cap at 2^31 to avoid overflow */
79 if (maxsectors > (1 << (31-9)))
81 return maxsectors << 9;
84 static void linear_unplug(struct request_queue *q)
86 mddev_t *mddev = q->queuedata;
87 linear_conf_t *conf = mddev_to_conf(mddev);
90 for (i=0; i < mddev->raid_disks; i++) {
91 struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
96 static int linear_congested(void *data, int bits)
98 mddev_t *mddev = data;
99 linear_conf_t *conf = mddev_to_conf(mddev);
102 for (i = 0; i < mddev->raid_disks && !ret ; i++) {
103 struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
104 ret |= bdi_congested(&q->backing_dev_info, bits);
109 static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
115 sector_t min_spacing;
116 sector_t curr_offset;
117 struct list_head *tmp;
119 conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
125 conf->array_sectors = 0;
127 rdev_for_each(rdev, tmp, mddev) {
128 int j = rdev->raid_disk;
129 dev_info_t *disk = conf->disks + j;
131 if (j < 0 || j >= raid_disks || disk->rdev) {
132 printk("linear: disk numbering problem. Aborting!\n");
138 blk_queue_stack_limits(mddev->queue,
139 rdev->bdev->bd_disk->queue);
140 /* as we don't honour merge_bvec_fn, we must never risk
141 * violating it, so limit ->max_sector to one PAGE, as
142 * a one page request is never in violation.
144 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
145 mddev->queue->max_sectors > (PAGE_SIZE>>9))
146 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
148 disk->size = rdev->size;
149 conf->array_sectors += rdev->size * 2;
153 if (cnt != raid_disks) {
154 printk("linear: not enough drives present. Aborting!\n");
158 min_spacing = conf->array_sectors / 2;
159 sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
161 /* min_spacing is the minimum spacing that will fit the hash
162 * table in one PAGE. This may be much smaller than needed.
163 * We find the smallest non-terminal set of consecutive devices
164 * that is larger than min_spacing and use the size of that as
167 conf->hash_spacing = conf->array_sectors / 2;
168 for (i=0; i < cnt-1 ; i++) {
171 for (j = i; j < cnt - 1 && sz < min_spacing; j++)
172 sz += conf->disks[j].size;
173 if (sz >= min_spacing && sz < conf->hash_spacing)
174 conf->hash_spacing = sz;
177 /* hash_spacing may be too large for sector_div to work with,
178 * so we might need to pre-shift
181 if (sizeof(sector_t) > sizeof(u32)) {
182 sector_t space = conf->hash_spacing;
183 while (space > (sector_t)(~(u32)0)) {
189 * This code was restructured to work around a gcc-2.95.3 internal
190 * compiler error. Alter it with care.
197 sz = conf->array_sectors >> (conf->preshift + 1);
198 sz += 1; /* force round-up */
199 base = conf->hash_spacing >> conf->preshift;
200 round = sector_div(sz, base);
201 nb_zone = sz + (round ? 1 : 0);
203 BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
205 conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
207 if (!conf->hash_table)
211 * Here we generate the linear hash table
212 * First calculate the device offsets.
214 conf->disks[0].offset = 0;
215 for (i = 1; i < raid_disks; i++)
216 conf->disks[i].offset =
217 conf->disks[i-1].offset +
218 conf->disks[i-1].size;
220 table = conf->hash_table;
222 for (curr_offset = 0;
223 curr_offset < conf->array_sectors / 2;
224 curr_offset += conf->hash_spacing) {
226 while (i < raid_disks-1 &&
227 curr_offset >= conf->disks[i+1].offset)
230 *table ++ = conf->disks + i;
233 if (conf->preshift) {
234 conf->hash_spacing >>= conf->preshift;
235 /* round hash_spacing up so that when we divide by it,
236 * we err on the side of "too-low", which is safest.
238 conf->hash_spacing++;
241 BUG_ON(table - conf->hash_table > nb_zone);
250 static int linear_run (mddev_t *mddev)
254 mddev->queue->queue_lock = &mddev->queue->__queue_lock;
255 conf = linear_conf(mddev, mddev->raid_disks);
259 mddev->private = conf;
260 mddev->array_sectors = conf->array_sectors;
262 blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
263 mddev->queue->unplug_fn = linear_unplug;
264 mddev->queue->backing_dev_info.congested_fn = linear_congested;
265 mddev->queue->backing_dev_info.congested_data = mddev;
269 static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
271 /* Adding a drive to a linear array allows the array to grow.
272 * It is permitted if the new drive has a matching superblock
273 * already on it, with raid_disk equal to raid_disks.
274 * It is achieved by creating a new linear_private_data structure
275 * and swapping it in in-place of the current one.
276 * The current one is never freed until the array is stopped.
279 linear_conf_t *newconf;
281 if (rdev->saved_raid_disk != mddev->raid_disks)
284 rdev->raid_disk = rdev->saved_raid_disk;
286 newconf = linear_conf(mddev,mddev->raid_disks+1);
291 newconf->prev = mddev_to_conf(mddev);
292 mddev->private = newconf;
294 mddev->array_sectors = newconf->array_sectors;
295 set_capacity(mddev->gendisk, mddev->array_sectors);
299 static int linear_stop (mddev_t *mddev)
301 linear_conf_t *conf = mddev_to_conf(mddev);
303 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
305 linear_conf_t *t = conf->prev;
306 kfree(conf->hash_table);
314 static int linear_make_request (struct request_queue *q, struct bio *bio)
316 const int rw = bio_data_dir(bio);
317 mddev_t *mddev = q->queuedata;
322 if (unlikely(bio_barrier(bio))) {
323 bio_endio(bio, -EOPNOTSUPP);
327 cpu = part_stat_lock();
328 part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
329 part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
333 tmp_dev = which_dev(mddev, bio->bi_sector);
334 block = bio->bi_sector >> 1;
336 if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
337 || block < tmp_dev->offset)) {
338 char b[BDEVNAME_SIZE];
340 printk("linear_make_request: Block %llu out of bounds on "
341 "dev %s size %llu offset %llu\n",
342 (unsigned long long)block,
343 bdevname(tmp_dev->rdev->bdev, b),
344 (unsigned long long)tmp_dev->size,
345 (unsigned long long)tmp_dev->offset);
349 if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
350 (tmp_dev->offset + tmp_dev->size)<<1)) {
351 /* This bio crosses a device boundary, so we have to
356 ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
357 if (linear_make_request(q, &bp->bio1))
358 generic_make_request(&bp->bio1);
359 if (linear_make_request(q, &bp->bio2))
360 generic_make_request(&bp->bio2);
361 bio_pair_release(bp);
365 bio->bi_bdev = tmp_dev->rdev->bdev;
366 bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;
371 static void linear_status (struct seq_file *seq, mddev_t *mddev)
377 linear_conf_t *conf = mddev_to_conf(mddev);
380 seq_printf(seq, " ");
381 for (j = 0; j < mddev->raid_disks; j++)
383 char b[BDEVNAME_SIZE];
384 s += conf->smallest_size;
385 seq_printf(seq, "[%s",
386 bdevname(conf->hash_table[j][0].rdev->bdev,b));
388 while (s > conf->hash_table[j][0].offset +
389 conf->hash_table[j][0].size)
390 seq_printf(seq, "/%s] ",
391 bdevname(conf->hash_table[j][1].rdev->bdev,b));
393 seq_printf(seq, "] ");
395 seq_printf(seq, "\n");
397 seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
401 static struct mdk_personality linear_personality =
404 .level = LEVEL_LINEAR,
405 .owner = THIS_MODULE,
406 .make_request = linear_make_request,
409 .status = linear_status,
410 .hot_add_disk = linear_add,
413 static int __init linear_init (void)
415 return register_md_personality (&linear_personality);
418 static void linear_exit (void)
420 unregister_md_personality (&linear_personality);
424 module_init(linear_init);
425 module_exit(linear_exit);
426 MODULE_LICENSE("GPL");
427 MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
428 MODULE_ALIAS("md-linear");
429 MODULE_ALIAS("md-level--1");