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/blkdev.h>
20#include <linux/raid/md_u.h>
21#include <linux/seq_file.h>
22#include <linux/module.h>
23#include <linux/slab.h>
24#include "md.h"
25#include "linear.h"
26
27/*
28 * find which device holds a particular offset
29 */
30static inline struct dev_info *which_dev(struct mddev *mddev, sector_t sector)
31{
32	int lo, mid, hi;
33	struct linear_conf *conf;
34
35	lo = 0;
36	hi = mddev->raid_disks - 1;
37	conf = rcu_dereference(mddev->private);
38
39	/*
40	 * Binary Search
41	 */
42
43	while (hi > lo) {
44
45		mid = (hi + lo) / 2;
46		if (sector < conf->disks[mid].end_sector)
47			hi = mid;
48		else
49			lo = mid + 1;
50	}
51
52	return conf->disks + lo;
53}
54
55/**
56 *	linear_mergeable_bvec -- tell bio layer if two requests can be merged
57 *	@q: request queue
58 *	@bvm: properties of new bio
59 *	@biovec: the request that could be merged to it.
60 *
61 *	Return amount of bytes we can take at this offset
62 */
63static int linear_mergeable_bvec(struct request_queue *q,
64				 struct bvec_merge_data *bvm,
65				 struct bio_vec *biovec)
66{
67	struct mddev *mddev = q->queuedata;
68	struct dev_info *dev0;
69	unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
70	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
71	int maxbytes = biovec->bv_len;
72	struct request_queue *subq;
73
74	rcu_read_lock();
75	dev0 = which_dev(mddev, sector);
76	maxsectors = dev0->end_sector - sector;
77	subq = bdev_get_queue(dev0->rdev->bdev);
78	if (subq->merge_bvec_fn) {
79		bvm->bi_bdev = dev0->rdev->bdev;
80		bvm->bi_sector -= dev0->end_sector - dev0->rdev->sectors;
81		maxbytes = min(maxbytes, subq->merge_bvec_fn(subq, bvm,
82							     biovec));
83	}
84	rcu_read_unlock();
85
86	if (maxsectors < bio_sectors)
87		maxsectors = 0;
88	else
89		maxsectors -= bio_sectors;
90
91	if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
92		return maxbytes;
93
94	if (maxsectors > (maxbytes >> 9))
95		return maxbytes;
96	else
97		return maxsectors << 9;
98}
99
100static int linear_congested(void *data, int bits)
101{
102	struct mddev *mddev = data;
103	struct linear_conf *conf;
104	int i, ret = 0;
105
106	if (mddev_congested(mddev, bits))
107		return 1;
108
109	rcu_read_lock();
110	conf = rcu_dereference(mddev->private);
111
112	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
113		struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
114		ret |= bdi_congested(&q->backing_dev_info, bits);
115	}
116
117	rcu_read_unlock();
118	return ret;
119}
120
121static sector_t linear_size(struct mddev *mddev, sector_t sectors, int raid_disks)
122{
123	struct linear_conf *conf;
124	sector_t array_sectors;
125
126	rcu_read_lock();
127	conf = rcu_dereference(mddev->private);
128	WARN_ONCE(sectors || raid_disks,
129		  "%s does not support generic reshape\n", __func__);
130	array_sectors = conf->array_sectors;
131	rcu_read_unlock();
132
133	return array_sectors;
134}
135
136static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
137{
138	struct linear_conf *conf;
139	struct md_rdev *rdev;
140	int i, cnt;
141	bool discard_supported = false;
142
143	conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
144			GFP_KERNEL);
145	if (!conf)
146		return NULL;
147
148	cnt = 0;
149	conf->array_sectors = 0;
150
151	rdev_for_each(rdev, mddev) {
152		int j = rdev->raid_disk;
153		struct dev_info *disk = conf->disks + j;
154		sector_t sectors;
155
156		if (j < 0 || j >= raid_disks || disk->rdev) {
157			printk(KERN_ERR "md/linear:%s: disk numbering problem. Aborting!\n",
158			       mdname(mddev));
159			goto out;
160		}
161
162		disk->rdev = rdev;
163		if (mddev->chunk_sectors) {
164			sectors = rdev->sectors;
165			sector_div(sectors, mddev->chunk_sectors);
166			rdev->sectors = sectors * mddev->chunk_sectors;
167		}
168
169		disk_stack_limits(mddev->gendisk, rdev->bdev,
170				  rdev->data_offset << 9);
171
172		conf->array_sectors += rdev->sectors;
173		cnt++;
174
175		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
176			discard_supported = true;
177	}
178	if (cnt != raid_disks) {
179		printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
180		       mdname(mddev));
181		goto out;
182	}
183
184	if (!discard_supported)
185		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
186	else
187		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
188
189	/*
190	 * Here we calculate the device offsets.
191	 */
192	conf->disks[0].end_sector = conf->disks[0].rdev->sectors;
193
194	for (i = 1; i < raid_disks; i++)
195		conf->disks[i].end_sector =
196			conf->disks[i-1].end_sector +
197			conf->disks[i].rdev->sectors;
198
199	return conf;
200
201out:
202	kfree(conf);
203	return NULL;
204}
205
206static int linear_run (struct mddev *mddev)
207{
208	struct linear_conf *conf;
209	int ret;
210
211	if (md_check_no_bitmap(mddev))
212		return -EINVAL;
213	conf = linear_conf(mddev, mddev->raid_disks);
214
215	if (!conf)
216		return 1;
217	mddev->private = conf;
218	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
219
220	blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
221	mddev->queue->backing_dev_info.congested_fn = linear_congested;
222	mddev->queue->backing_dev_info.congested_data = mddev;
223
224	ret =  md_integrity_register(mddev);
225	if (ret) {
226		kfree(conf);
227		mddev->private = NULL;
228	}
229	return ret;
230}
231
232static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
233{
234	/* Adding a drive to a linear array allows the array to grow.
235	 * It is permitted if the new drive has a matching superblock
236	 * already on it, with raid_disk equal to raid_disks.
237	 * It is achieved by creating a new linear_private_data structure
238	 * and swapping it in in-place of the current one.
239	 * The current one is never freed until the array is stopped.
240	 * This avoids races.
241	 */
242	struct linear_conf *newconf, *oldconf;
243
244	if (rdev->saved_raid_disk != mddev->raid_disks)
245		return -EINVAL;
246
247	rdev->raid_disk = rdev->saved_raid_disk;
248	rdev->saved_raid_disk = -1;
249
250	newconf = linear_conf(mddev,mddev->raid_disks+1);
251
252	if (!newconf)
253		return -ENOMEM;
254
255	oldconf = rcu_dereference_protected(mddev->private,
256					    lockdep_is_held(
257						    &mddev->reconfig_mutex));
258	mddev->raid_disks++;
259	rcu_assign_pointer(mddev->private, newconf);
260	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
261	set_capacity(mddev->gendisk, mddev->array_sectors);
262	revalidate_disk(mddev->gendisk);
263	kfree_rcu(oldconf, rcu);
264	return 0;
265}
266
267static int linear_stop (struct mddev *mddev)
268{
269	struct linear_conf *conf =
270		rcu_dereference_protected(mddev->private,
271					  lockdep_is_held(
272						  &mddev->reconfig_mutex));
273
274	/*
275	 * We do not require rcu protection here since
276	 * we hold reconfig_mutex for both linear_add and
277	 * linear_stop, so they cannot race.
278	 * We should make sure any old 'conf's are properly
279	 * freed though.
280	 */
281	rcu_barrier();
282	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
283	kfree(conf);
284	mddev->private = NULL;
285
286	return 0;
287}
288
289static void linear_make_request(struct mddev *mddev, struct bio *bio)
290{
291	char b[BDEVNAME_SIZE];
292	struct dev_info *tmp_dev;
293	struct bio *split;
294	sector_t start_sector, end_sector, data_offset;
295
296	if (unlikely(bio->bi_rw & REQ_FLUSH)) {
297		md_flush_request(mddev, bio);
298		return;
299	}
300
301	do {
302		rcu_read_lock();
303
304		tmp_dev = which_dev(mddev, bio->bi_iter.bi_sector);
305		start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
306		end_sector = tmp_dev->end_sector;
307		data_offset = tmp_dev->rdev->data_offset;
308		bio->bi_bdev = tmp_dev->rdev->bdev;
309
310		rcu_read_unlock();
311
312		if (unlikely(bio->bi_iter.bi_sector >= end_sector ||
313			     bio->bi_iter.bi_sector < start_sector))
314			goto out_of_bounds;
315
316		if (unlikely(bio_end_sector(bio) > end_sector)) {
317			/* This bio crosses a device boundary, so we have to
318			 * split it.
319			 */
320			split = bio_split(bio, end_sector -
321					  bio->bi_iter.bi_sector,
322					  GFP_NOIO, fs_bio_set);
323			bio_chain(split, bio);
324		} else {
325			split = bio;
326		}
327
328		split->bi_iter.bi_sector = split->bi_iter.bi_sector -
329			start_sector + data_offset;
330
331		if (unlikely((split->bi_rw & REQ_DISCARD) &&
332			 !blk_queue_discard(bdev_get_queue(split->bi_bdev)))) {
333			/* Just ignore it */
334			bio_endio(split, 0);
335		} else
336			generic_make_request(split);
337	} while (split != bio);
338	return;
339
340out_of_bounds:
341	printk(KERN_ERR
342	       "md/linear:%s: make_request: Sector %llu out of bounds on "
343	       "dev %s: %llu sectors, offset %llu\n",
344	       mdname(mddev),
345	       (unsigned long long)bio->bi_iter.bi_sector,
346	       bdevname(tmp_dev->rdev->bdev, b),
347	       (unsigned long long)tmp_dev->rdev->sectors,
348	       (unsigned long long)start_sector);
349	bio_io_error(bio);
350}
351
352static void linear_status (struct seq_file *seq, struct mddev *mddev)
353{
354
355	seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
356}
357
358static struct md_personality linear_personality =
359{
360	.name		= "linear",
361	.level		= LEVEL_LINEAR,
362	.owner		= THIS_MODULE,
363	.make_request	= linear_make_request,
364	.run		= linear_run,
365	.stop		= linear_stop,
366	.status		= linear_status,
367	.hot_add_disk	= linear_add,
368	.size		= linear_size,
369};
370
371static int __init linear_init (void)
372{
373	return register_md_personality (&linear_personality);
374}
375
376static void linear_exit (void)
377{
378	unregister_md_personality (&linear_personality);
379}
380
381module_init(linear_init);
382module_exit(linear_exit);
383MODULE_LICENSE("GPL");
384MODULE_DESCRIPTION("Linear device concatenation personality for MD");
385MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
386MODULE_ALIAS("md-linear");
387MODULE_ALIAS("md-level--1");
388