linear.c revision 159ec1fc060ab22b157a62364045f5e98749c4d3 
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 */
24static 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
29	/*
30	 * sector_div(a,b) returns the remainer and sets a to a/b
31	 */
32	sector >>= conf->sector_shift;
33	(void)sector_div(sector, conf->spacing);
34	hash = conf->hash_table[sector];
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 */
49static 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
75static 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
87static 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
100static 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
237out:
238	kfree(conf);
239	return NULL;
240}
241
242static 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
261static 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
291static 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
306static 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
367static 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
374static 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
386static int __init linear_init (void)
387{
388	return register_md_personality (&linear_personality);
389}
390
391static void linear_exit (void)
392{
393	unregister_md_personality (&linear_personality);
394}
395
396
397module_init(linear_init);
398module_exit(linear_exit);
399MODULE_LICENSE("GPL");
400MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
401MODULE_ALIAS("md-linear");
402MODULE_ALIAS("md-level--1");
403