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 = 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 mddev *mddev,
64				 struct bvec_merge_data *bvm,
65				 struct bio_vec *biovec)
66{
67	struct dev_info *dev0;
68	unsigned long maxsectors, bio_sectors = bvm->bi_size >> 9;
69	sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
70	int maxbytes = biovec->bv_len;
71	struct request_queue *subq;
72
73	dev0 = which_dev(mddev, sector);
74	maxsectors = dev0->end_sector - sector;
75	subq = bdev_get_queue(dev0->rdev->bdev);
76	if (subq->merge_bvec_fn) {
77		bvm->bi_bdev = dev0->rdev->bdev;
78		bvm->bi_sector -= dev0->end_sector - dev0->rdev->sectors;
79		maxbytes = min(maxbytes, subq->merge_bvec_fn(subq, bvm,
80							     biovec));
81	}
82
83	if (maxsectors < bio_sectors)
84		maxsectors = 0;
85	else
86		maxsectors -= bio_sectors;
87
88	if (maxsectors <= (PAGE_SIZE >> 9 ) && bio_sectors == 0)
89		return maxbytes;
90
91	if (maxsectors > (maxbytes >> 9))
92		return maxbytes;
93	else
94		return maxsectors << 9;
95}
96
97static int linear_congested(struct mddev *mddev, int bits)
98{
99	struct linear_conf *conf;
100	int i, ret = 0;
101
102	conf = mddev->private;
103
104	for (i = 0; i < mddev->raid_disks && !ret ; i++) {
105		struct request_queue *q = bdev_get_queue(conf->disks[i].rdev->bdev);
106		ret |= bdi_congested(&q->backing_dev_info, bits);
107	}
108
109	return ret;
110}
111
112static sector_t linear_size(struct mddev *mddev, sector_t sectors, int raid_disks)
113{
114	struct linear_conf *conf;
115	sector_t array_sectors;
116
117	conf = mddev->private;
118	WARN_ONCE(sectors || raid_disks,
119		  "%s does not support generic reshape\n", __func__);
120	array_sectors = conf->array_sectors;
121
122	return array_sectors;
123}
124
125static struct linear_conf *linear_conf(struct mddev *mddev, int raid_disks)
126{
127	struct linear_conf *conf;
128	struct md_rdev *rdev;
129	int i, cnt;
130	bool discard_supported = false;
131
132	conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
133			GFP_KERNEL);
134	if (!conf)
135		return NULL;
136
137	cnt = 0;
138	conf->array_sectors = 0;
139
140	rdev_for_each(rdev, mddev) {
141		int j = rdev->raid_disk;
142		struct dev_info *disk = conf->disks + j;
143		sector_t sectors;
144
145		if (j < 0 || j >= raid_disks || disk->rdev) {
146			printk(KERN_ERR "md/linear:%s: disk numbering problem. Aborting!\n",
147			       mdname(mddev));
148			goto out;
149		}
150
151		disk->rdev = rdev;
152		if (mddev->chunk_sectors) {
153			sectors = rdev->sectors;
154			sector_div(sectors, mddev->chunk_sectors);
155			rdev->sectors = sectors * mddev->chunk_sectors;
156		}
157
158		disk_stack_limits(mddev->gendisk, rdev->bdev,
159				  rdev->data_offset << 9);
160
161		conf->array_sectors += rdev->sectors;
162		cnt++;
163
164		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
165			discard_supported = true;
166	}
167	if (cnt != raid_disks) {
168		printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
169		       mdname(mddev));
170		goto out;
171	}
172
173	if (!discard_supported)
174		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
175	else
176		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
177
178	/*
179	 * Here we calculate the device offsets.
180	 */
181	conf->disks[0].end_sector = conf->disks[0].rdev->sectors;
182
183	for (i = 1; i < raid_disks; i++)
184		conf->disks[i].end_sector =
185			conf->disks[i-1].end_sector +
186			conf->disks[i].rdev->sectors;
187
188	return conf;
189
190out:
191	kfree(conf);
192	return NULL;
193}
194
195static int linear_run (struct mddev *mddev)
196{
197	struct linear_conf *conf;
198	int ret;
199
200	if (md_check_no_bitmap(mddev))
201		return -EINVAL;
202	conf = linear_conf(mddev, mddev->raid_disks);
203
204	if (!conf)
205		return 1;
206	mddev->private = conf;
207	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
208
209	ret =  md_integrity_register(mddev);
210	if (ret) {
211		kfree(conf);
212		mddev->private = NULL;
213	}
214	return ret;
215}
216
217static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
218{
219	/* Adding a drive to a linear array allows the array to grow.
220	 * It is permitted if the new drive has a matching superblock
221	 * already on it, with raid_disk equal to raid_disks.
222	 * It is achieved by creating a new linear_private_data structure
223	 * and swapping it in in-place of the current one.
224	 * The current one is never freed until the array is stopped.
225	 * This avoids races.
226	 */
227	struct linear_conf *newconf, *oldconf;
228
229	if (rdev->saved_raid_disk != mddev->raid_disks)
230		return -EINVAL;
231
232	rdev->raid_disk = rdev->saved_raid_disk;
233	rdev->saved_raid_disk = -1;
234
235	newconf = linear_conf(mddev,mddev->raid_disks+1);
236
237	if (!newconf)
238		return -ENOMEM;
239
240	mddev_suspend(mddev);
241	oldconf = mddev->private;
242	mddev->raid_disks++;
243	mddev->private = newconf;
244	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
245	set_capacity(mddev->gendisk, mddev->array_sectors);
246	mddev_resume(mddev);
247	revalidate_disk(mddev->gendisk);
248	kfree(oldconf);
249	return 0;
250}
251
252static void linear_free(struct mddev *mddev, void *priv)
253{
254	struct linear_conf *conf = priv;
255
256	kfree(conf);
257}
258
259static void linear_make_request(struct mddev *mddev, struct bio *bio)
260{
261	char b[BDEVNAME_SIZE];
262	struct dev_info *tmp_dev;
263	struct bio *split;
264	sector_t start_sector, end_sector, data_offset;
265
266	if (unlikely(bio->bi_rw & REQ_FLUSH)) {
267		md_flush_request(mddev, bio);
268		return;
269	}
270
271	do {
272		tmp_dev = which_dev(mddev, bio->bi_iter.bi_sector);
273		start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
274		end_sector = tmp_dev->end_sector;
275		data_offset = tmp_dev->rdev->data_offset;
276		bio->bi_bdev = tmp_dev->rdev->bdev;
277
278		if (unlikely(bio->bi_iter.bi_sector >= end_sector ||
279			     bio->bi_iter.bi_sector < start_sector))
280			goto out_of_bounds;
281
282		if (unlikely(bio_end_sector(bio) > end_sector)) {
283			/* This bio crosses a device boundary, so we have to
284			 * split it.
285			 */
286			split = bio_split(bio, end_sector -
287					  bio->bi_iter.bi_sector,
288					  GFP_NOIO, fs_bio_set);
289			bio_chain(split, bio);
290		} else {
291			split = bio;
292		}
293
294		split->bi_iter.bi_sector = split->bi_iter.bi_sector -
295			start_sector + data_offset;
296
297		if (unlikely((split->bi_rw & REQ_DISCARD) &&
298			 !blk_queue_discard(bdev_get_queue(split->bi_bdev)))) {
299			/* Just ignore it */
300			bio_endio(split, 0);
301		} else
302			generic_make_request(split);
303	} while (split != bio);
304	return;
305
306out_of_bounds:
307	printk(KERN_ERR
308	       "md/linear:%s: make_request: Sector %llu out of bounds on "
309	       "dev %s: %llu sectors, offset %llu\n",
310	       mdname(mddev),
311	       (unsigned long long)bio->bi_iter.bi_sector,
312	       bdevname(tmp_dev->rdev->bdev, b),
313	       (unsigned long long)tmp_dev->rdev->sectors,
314	       (unsigned long long)start_sector);
315	bio_io_error(bio);
316}
317
318static void linear_status (struct seq_file *seq, struct mddev *mddev)
319{
320
321	seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
322}
323
324static void linear_quiesce(struct mddev *mddev, int state)
325{
326}
327
328static struct md_personality linear_personality =
329{
330	.name		= "linear",
331	.level		= LEVEL_LINEAR,
332	.owner		= THIS_MODULE,
333	.make_request	= linear_make_request,
334	.run		= linear_run,
335	.free		= linear_free,
336	.status		= linear_status,
337	.hot_add_disk	= linear_add,
338	.size		= linear_size,
339	.quiesce	= linear_quiesce,
340	.congested	= linear_congested,
341	.mergeable_bvec	= linear_mergeable_bvec,
342};
343
344static int __init linear_init (void)
345{
346	return register_md_personality (&linear_personality);
347}
348
349static void linear_exit (void)
350{
351	unregister_md_personality (&linear_personality);
352}
353
354module_init(linear_init);
355module_exit(linear_exit);
356MODULE_LICENSE("GPL");
357MODULE_DESCRIPTION("Linear device concatenation personality for MD");
358MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
359MODULE_ALIAS("md-linear");
360MODULE_ALIAS("md-level--1");
361