linear.c revision d089c6af10c2be5988f03667d6d22fe6085fbe5e 
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/module.h>
20
21#include <linux/raid/md.h>
22#include <linux/slab.h>
23#include <linux/raid/linear.h>
24
25#define MAJOR_NR MD_MAJOR
26#define MD_DRIVER
27#define MD_PERSONALITY
28
29/*
30 * find which device holds a particular offset
31 */
32static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
33{
34	dev_info_t *hash;
35	linear_conf_t *conf = mddev_to_conf(mddev);
36	sector_t block = sector >> 1;
37
38	/*
39	 * sector_div(a,b) returns the remainer and sets a to a/b
40	 */
41	block >>= conf->preshift;
42	(void)sector_div(block, conf->hash_spacing);
43	hash = conf->hash_table[block];
44
45	while ((sector>>1) >= (hash->size + hash->offset))
46		hash++;
47	return hash;
48}
49
50/**
51 *	linear_mergeable_bvec -- tell bio layer if two requests can be merged
52 *	@q: request queue
53 *	@bio: the buffer head that's been built up so far
54 *	@biovec: the request that could be merged to it.
55 *
56 *	Return amount of bytes we can take at this offset
57 */
58static int linear_mergeable_bvec(struct request_queue *q, struct bio *bio, struct bio_vec *biovec)
59{
60	mddev_t *mddev = q->queuedata;
61	dev_info_t *dev0;
62	unsigned long maxsectors, bio_sectors = bio->bi_size >> 9;
63	sector_t sector = bio->bi_sector + get_start_sect(bio->bi_bdev);
64
65	dev0 = which_dev(mddev, sector);
66	maxsectors = (dev0->size << 1) - (sector - (dev0->offset<<1));
67
68	if (maxsectors < bio_sectors)
69		maxsectors = 0;
70	else
71		maxsectors -= bio_sectors;
72
73	if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
74		return biovec->bv_len;
75	/* The bytes available at this offset could be really big,
76	 * so we cap at 2^31 to avoid overflow */
77	if (maxsectors > (1 << (31-9)))
78		return 1<<31;
79	return maxsectors << 9;
80}
81
82static void linear_unplug(struct request_queue *q)
83{
84	mddev_t *mddev = q->queuedata;
85	linear_conf_t *conf = mddev_to_conf(mddev);
86	int i;
87
88	for (i=0; i < mddev->raid_disks; i++) {
89		struct request_queue *r_queue = bdev_get_queue(conf->disks[i].rdev->bdev);
90		blk_unplug(r_queue);
91	}
92}
93
94static int linear_congested(void *data, int bits)
95{
96	mddev_t *mddev = data;
97	linear_conf_t *conf = mddev_to_conf(mddev);
98	int i, ret = 0;
99
100	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
101		struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
102		ret |= bdi_congested(&q->backing_dev_info, bits);
103	}
104	return ret;
105}
106
107static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
108{
109	linear_conf_t *conf;
110	dev_info_t **table;
111	mdk_rdev_t *rdev;
112	int i, nb_zone, cnt;
113	sector_t min_spacing;
114	sector_t curr_offset;
115	struct list_head *tmp;
116
117	conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
118			GFP_KERNEL);
119	if (!conf)
120		return NULL;
121
122	cnt = 0;
123	conf->array_size = 0;
124
125	rdev_for_each(rdev, tmp, mddev) {
126		int j = rdev->raid_disk;
127		dev_info_t *disk = conf->disks + j;
128
129		if (j < 0 || j > raid_disks || disk->rdev) {
130			printk("linear: disk numbering problem. Aborting!\n");
131			goto out;
132		}
133
134		disk->rdev = rdev;
135
136		blk_queue_stack_limits(mddev->queue,
137				       rdev->bdev->bd_disk->queue);
138		/* as we don't honour merge_bvec_fn, we must never risk
139		 * violating it, so limit ->max_sector to one PAGE, as
140		 * a one page request is never in violation.
141		 */
142		if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
143		    mddev->queue->max_sectors > (PAGE_SIZE>>9))
144			blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
145
146		disk->size = rdev->size;
147		conf->array_size += rdev->size;
148
149		cnt++;
150	}
151	if (cnt != raid_disks) {
152		printk("linear: not enough drives present. Aborting!\n");
153		goto out;
154	}
155
156	min_spacing = conf->array_size;
157	sector_div(min_spacing, PAGE_SIZE/sizeof(struct dev_info *));
158
159	/* min_spacing is the minimum spacing that will fit the hash
160	 * table in one PAGE.  This may be much smaller than needed.
161	 * We find the smallest non-terminal set of consecutive devices
162	 * that is larger than min_spacing as use the size of that as
163	 * the actual spacing
164	 */
165	conf->hash_spacing = conf->array_size;
166	for (i=0; i < cnt-1 ; i++) {
167		sector_t sz = 0;
168		int j;
169		for (j = i; j < cnt - 1 && sz < min_spacing; j++)
170			sz += conf->disks[j].size;
171		if (sz >= min_spacing && sz < conf->hash_spacing)
172			conf->hash_spacing = sz;
173	}
174
175	/* hash_spacing may be too large for sector_div to work with,
176	 * so we might need to pre-shift
177	 */
178	conf->preshift = 0;
179	if (sizeof(sector_t) > sizeof(u32)) {
180		sector_t space = conf->hash_spacing;
181		while (space > (sector_t)(~(u32)0)) {
182			space >>= 1;
183			conf->preshift++;
184		}
185	}
186	/*
187	 * This code was restructured to work around a gcc-2.95.3 internal
188	 * compiler error.  Alter it with care.
189	 */
190	{
191		sector_t sz;
192		unsigned round;
193		unsigned long base;
194
195		sz = conf->array_size >> conf->preshift;
196		sz += 1; /* force round-up */
197		base = conf->hash_spacing >> conf->preshift;
198		round = sector_div(sz, base);
199		nb_zone = sz + (round ? 1 : 0);
200	}
201	BUG_ON(nb_zone > PAGE_SIZE / sizeof(struct dev_info *));
202
203	conf->hash_table = kmalloc (sizeof (struct dev_info *) * nb_zone,
204					GFP_KERNEL);
205	if (!conf->hash_table)
206		goto out;
207
208	/*
209	 * Here we generate the linear hash table
210	 * First calculate the device offsets.
211	 */
212	conf->disks[0].offset = 0;
213	for (i = 1; i < raid_disks; i++)
214		conf->disks[i].offset =
215			conf->disks[i-1].offset +
216			conf->disks[i-1].size;
217
218	table = conf->hash_table;
219	curr_offset = 0;
220	i = 0;
221	for (curr_offset = 0;
222	     curr_offset < conf->array_size;
223	     curr_offset += conf->hash_spacing) {
224
225		while (i < raid_disks-1 &&
226		       curr_offset >= conf->disks[i+1].offset)
227			i++;
228
229		*table ++ = conf->disks + i;
230	}
231
232	if (conf->preshift) {
233		conf->hash_spacing >>= conf->preshift;
234		/* round hash_spacing up so that when we divide by it,
235		 * we err on the side of "too-low", which is safest.
236		 */
237		conf->hash_spacing++;
238	}
239
240	BUG_ON(table - conf->hash_table > nb_zone);
241
242	return conf;
243
244out:
245	kfree(conf);
246	return NULL;
247}
248
249static int linear_run (mddev_t *mddev)
250{
251	linear_conf_t *conf;
252
253	conf = linear_conf(mddev, mddev->raid_disks);
254
255	if (!conf)
256		return 1;
257	mddev->private = conf;
258	mddev->array_size = conf->array_size;
259
260	blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
261	mddev->queue->unplug_fn = linear_unplug;
262	mddev->queue->backing_dev_info.congested_fn = linear_congested;
263	mddev->queue->backing_dev_info.congested_data = mddev;
264	return 0;
265}
266
267static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
268{
269	/* Adding a drive to a linear array allows the array to grow.
270	 * It is permitted if the new drive has a matching superblock
271	 * already on it, with raid_disk equal to raid_disks.
272	 * It is achieved by creating a new linear_private_data structure
273	 * and swapping it in in-place of the current one.
274	 * The current one is never freed until the array is stopped.
275	 * This avoids races.
276	 */
277	linear_conf_t *newconf;
278
279	if (rdev->saved_raid_disk != mddev->raid_disks)
280		return -EINVAL;
281
282	rdev->raid_disk = rdev->saved_raid_disk;
283
284	newconf = linear_conf(mddev,mddev->raid_disks+1);
285
286	if (!newconf)
287		return -ENOMEM;
288
289	newconf->prev = mddev_to_conf(mddev);
290	mddev->private = newconf;
291	mddev->raid_disks++;
292	mddev->array_size = newconf->array_size;
293	set_capacity(mddev->gendisk, mddev->array_size << 1);
294	return 0;
295}
296
297static int linear_stop (mddev_t *mddev)
298{
299	linear_conf_t *conf = mddev_to_conf(mddev);
300
301	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
302	do {
303		linear_conf_t *t = conf->prev;
304		kfree(conf->hash_table);
305		kfree(conf);
306		conf = t;
307	} while (conf);
308
309	return 0;
310}
311
312static int linear_make_request (struct request_queue *q, struct bio *bio)
313{
314	const int rw = bio_data_dir(bio);
315	mddev_t *mddev = q->queuedata;
316	dev_info_t *tmp_dev;
317	sector_t block;
318
319	if (unlikely(bio_barrier(bio))) {
320		bio_endio(bio, -EOPNOTSUPP);
321		return 0;
322	}
323
324	disk_stat_inc(mddev->gendisk, ios[rw]);
325	disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
326
327	tmp_dev = which_dev(mddev, bio->bi_sector);
328	block = bio->bi_sector >> 1;
329
330	if (unlikely(block >= (tmp_dev->size + tmp_dev->offset)
331		     || block < tmp_dev->offset)) {
332		char b[BDEVNAME_SIZE];
333
334		printk("linear_make_request: Block %llu out of bounds on "
335			"dev %s size %llu offset %llu\n",
336			(unsigned long long)block,
337			bdevname(tmp_dev->rdev->bdev, b),
338			(unsigned long long)tmp_dev->size,
339		        (unsigned long long)tmp_dev->offset);
340		bio_io_error(bio);
341		return 0;
342	}
343	if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
344		     (tmp_dev->offset + tmp_dev->size)<<1)) {
345		/* This bio crosses a device boundary, so we have to
346		 * split it.
347		 */
348		struct bio_pair *bp;
349		bp = bio_split(bio, bio_split_pool,
350			       ((tmp_dev->offset + tmp_dev->size)<<1) - bio->bi_sector);
351		if (linear_make_request(q, &bp->bio1))
352			generic_make_request(&bp->bio1);
353		if (linear_make_request(q, &bp->bio2))
354			generic_make_request(&bp->bio2);
355		bio_pair_release(bp);
356		return 0;
357	}
358
359	bio->bi_bdev = tmp_dev->rdev->bdev;
360	bio->bi_sector = bio->bi_sector - (tmp_dev->offset << 1) + tmp_dev->rdev->data_offset;
361
362	return 1;
363}
364
365static void linear_status (struct seq_file *seq, mddev_t *mddev)
366{
367
368#undef MD_DEBUG
369#ifdef MD_DEBUG
370	int j;
371	linear_conf_t *conf = mddev_to_conf(mddev);
372	sector_t s = 0;
373
374	seq_printf(seq, "      ");
375	for (j = 0; j < mddev->raid_disks; j++)
376	{
377		char b[BDEVNAME_SIZE];
378		s += conf->smallest_size;
379		seq_printf(seq, "[%s",
380			   bdevname(conf->hash_table[j][0].rdev->bdev,b));
381
382		while (s > conf->hash_table[j][0].offset +
383		           conf->hash_table[j][0].size)
384			seq_printf(seq, "/%s] ",
385				   bdevname(conf->hash_table[j][1].rdev->bdev,b));
386		else
387			seq_printf(seq, "] ");
388	}
389	seq_printf(seq, "\n");
390#endif
391	seq_printf(seq, " %dk rounding", mddev->chunk_size/1024);
392}
393
394
395static struct mdk_personality linear_personality =
396{
397	.name		= "linear",
398	.level		= LEVEL_LINEAR,
399	.owner		= THIS_MODULE,
400	.make_request	= linear_make_request,
401	.run		= linear_run,
402	.stop		= linear_stop,
403	.status		= linear_status,
404	.hot_add_disk	= linear_add,
405};
406
407static int __init linear_init (void)
408{
409	return register_md_personality (&linear_personality);
410}
411
412static void linear_exit (void)
413{
414	unregister_md_personality (&linear_personality);
415}
416
417
418module_init(linear_init);
419module_exit(linear_exit);
420MODULE_LICENSE("GPL");
421MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
422MODULE_ALIAS("md-linear");
423MODULE_ALIAS("md-level--1");
424