Root/drivers/md/linear.c

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
142    conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
143            GFP_KERNEL);
144    if (!conf)
145        return NULL;
146
147    cnt = 0;
148    conf->array_sectors = 0;
149
150    rdev_for_each(rdev, mddev) {
151        int j = rdev->raid_disk;
152        struct dev_info *disk = conf->disks + j;
153        sector_t sectors;
154
155        if (j < 0 || j >= raid_disks || disk->rdev) {
156            printk(KERN_ERR "md/linear:%s: disk numbering problem. Aborting!\n",
157                   mdname(mddev));
158            goto out;
159        }
160
161        disk->rdev = rdev;
162        if (mddev->chunk_sectors) {
163            sectors = rdev->sectors;
164            sector_div(sectors, mddev->chunk_sectors);
165            rdev->sectors = sectors * mddev->chunk_sectors;
166        }
167
168        disk_stack_limits(mddev->gendisk, rdev->bdev,
169                  rdev->data_offset << 9);
170
171        conf->array_sectors += rdev->sectors;
172        cnt++;
173
174    }
175    if (cnt != raid_disks) {
176        printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
177               mdname(mddev));
178        goto out;
179    }
180
181    /*
182     * Here we calculate the device offsets.
183     */
184    conf->disks[0].end_sector = conf->disks[0].rdev->sectors;
185
186    for (i = 1; i < raid_disks; i++)
187        conf->disks[i].end_sector =
188            conf->disks[i-1].end_sector +
189            conf->disks[i].rdev->sectors;
190
191    return conf;
192
193out:
194    kfree(conf);
195    return NULL;
196}
197
198static int linear_run (struct mddev *mddev)
199{
200    struct linear_conf *conf;
201    int ret;
202
203    if (md_check_no_bitmap(mddev))
204        return -EINVAL;
205    conf = linear_conf(mddev, mddev->raid_disks);
206
207    if (!conf)
208        return 1;
209    mddev->private = conf;
210    md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
211
212    blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
213    mddev->queue->backing_dev_info.congested_fn = linear_congested;
214    mddev->queue->backing_dev_info.congested_data = mddev;
215
216    ret = md_integrity_register(mddev);
217    if (ret) {
218        kfree(conf);
219        mddev->private = NULL;
220    }
221    return ret;
222}
223
224static int linear_add(struct mddev *mddev, struct md_rdev *rdev)
225{
226    /* Adding a drive to a linear array allows the array to grow.
227     * It is permitted if the new drive has a matching superblock
228     * already on it, with raid_disk equal to raid_disks.
229     * It is achieved by creating a new linear_private_data structure
230     * and swapping it in in-place of the current one.
231     * The current one is never freed until the array is stopped.
232     * This avoids races.
233     */
234    struct linear_conf *newconf, *oldconf;
235
236    if (rdev->saved_raid_disk != mddev->raid_disks)
237        return -EINVAL;
238
239    rdev->raid_disk = rdev->saved_raid_disk;
240    rdev->saved_raid_disk = -1;
241
242    newconf = linear_conf(mddev,mddev->raid_disks+1);
243
244    if (!newconf)
245        return -ENOMEM;
246
247    oldconf = rcu_dereference(mddev->private);
248    mddev->raid_disks++;
249    rcu_assign_pointer(mddev->private, newconf);
250    md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
251    set_capacity(mddev->gendisk, mddev->array_sectors);
252    revalidate_disk(mddev->gendisk);
253    kfree_rcu(oldconf, rcu);
254    return 0;
255}
256
257static int linear_stop (struct mddev *mddev)
258{
259    struct linear_conf *conf = mddev->private;
260
261    /*
262     * We do not require rcu protection here since
263     * we hold reconfig_mutex for both linear_add and
264     * linear_stop, so they cannot race.
265     * We should make sure any old 'conf's are properly
266     * freed though.
267     */
268    rcu_barrier();
269    blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
270    kfree(conf);
271    mddev->private = NULL;
272
273    return 0;
274}
275
276static void linear_make_request(struct mddev *mddev, struct bio *bio)
277{
278    struct dev_info *tmp_dev;
279    sector_t start_sector;
280
281    if (unlikely(bio->bi_rw & REQ_FLUSH)) {
282        md_flush_request(mddev, bio);
283        return;
284    }
285
286    rcu_read_lock();
287    tmp_dev = which_dev(mddev, bio->bi_sector);
288    start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
289
290
291    if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
292             || (bio->bi_sector < start_sector))) {
293        char b[BDEVNAME_SIZE];
294
295        printk(KERN_ERR
296               "md/linear:%s: make_request: Sector %llu out of bounds on "
297               "dev %s: %llu sectors, offset %llu\n",
298               mdname(mddev),
299               (unsigned long long)bio->bi_sector,
300               bdevname(tmp_dev->rdev->bdev, b),
301               (unsigned long long)tmp_dev->rdev->sectors,
302               (unsigned long long)start_sector);
303        rcu_read_unlock();
304        bio_io_error(bio);
305        return;
306    }
307    if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
308             tmp_dev->end_sector)) {
309        /* This bio crosses a device boundary, so we have to
310         * split it.
311         */
312        struct bio_pair *bp;
313        sector_t end_sector = tmp_dev->end_sector;
314
315        rcu_read_unlock();
316
317        bp = bio_split(bio, end_sector - bio->bi_sector);
318
319        linear_make_request(mddev, &bp->bio1);
320        linear_make_request(mddev, &bp->bio2);
321        bio_pair_release(bp);
322        return;
323    }
324            
325    bio->bi_bdev = tmp_dev->rdev->bdev;
326    bio->bi_sector = bio->bi_sector - start_sector
327        + tmp_dev->rdev->data_offset;
328    rcu_read_unlock();
329    generic_make_request(bio);
330}
331
332static void linear_status (struct seq_file *seq, struct mddev *mddev)
333{
334
335    seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
336}
337
338
339static struct md_personality linear_personality =
340{
341    .name = "linear",
342    .level = LEVEL_LINEAR,
343    .owner = THIS_MODULE,
344    .make_request = linear_make_request,
345    .run = linear_run,
346    .stop = linear_stop,
347    .status = linear_status,
348    .hot_add_disk = linear_add,
349    .size = linear_size,
350};
351
352static int __init linear_init (void)
353{
354    return register_md_personality (&linear_personality);
355}
356
357static void linear_exit (void)
358{
359    unregister_md_personality (&linear_personality);
360}
361
362
363module_init(linear_init);
364module_exit(linear_exit);
365MODULE_LICENSE("GPL");
366MODULE_DESCRIPTION("Linear device concatenation personality for MD");
367MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
368MODULE_ALIAS("md-linear");
369MODULE_ALIAS("md-level--1");
370

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