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    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    struct dev_info *tmp_dev;
292    sector_t start_sector;
293
294    if (unlikely(bio->bi_rw & REQ_FLUSH)) {
295        md_flush_request(mddev, bio);
296        return;
297    }
298
299    rcu_read_lock();
300    tmp_dev = which_dev(mddev, bio->bi_sector);
301    start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
302
303
304    if (unlikely(bio->bi_sector >= (tmp_dev->end_sector)
305             || (bio->bi_sector < start_sector))) {
306        char b[BDEVNAME_SIZE];
307
308        printk(KERN_ERR
309               "md/linear:%s: make_request: Sector %llu out of bounds on "
310               "dev %s: %llu sectors, offset %llu\n",
311               mdname(mddev),
312               (unsigned long long)bio->bi_sector,
313               bdevname(tmp_dev->rdev->bdev, b),
314               (unsigned long long)tmp_dev->rdev->sectors,
315               (unsigned long long)start_sector);
316        rcu_read_unlock();
317        bio_io_error(bio);
318        return;
319    }
320    if (unlikely(bio->bi_sector + (bio->bi_size >> 9) >
321             tmp_dev->end_sector)) {
322        /* This bio crosses a device boundary, so we have to
323         * split it.
324         */
325        struct bio_pair *bp;
326        sector_t end_sector = tmp_dev->end_sector;
327
328        rcu_read_unlock();
329
330        bp = bio_split(bio, end_sector - bio->bi_sector);
331
332        linear_make_request(mddev, &bp->bio1);
333        linear_make_request(mddev, &bp->bio2);
334        bio_pair_release(bp);
335        return;
336    }
337            
338    bio->bi_bdev = tmp_dev->rdev->bdev;
339    bio->bi_sector = bio->bi_sector - start_sector
340        + tmp_dev->rdev->data_offset;
341    rcu_read_unlock();
342
343    if (unlikely((bio->bi_rw & REQ_DISCARD) &&
344             !blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
345        /* Just ignore it */
346        bio_endio(bio, 0);
347        return;
348    }
349
350    generic_make_request(bio);
351}
352
353static void linear_status (struct seq_file *seq, struct mddev *mddev)
354{
355
356    seq_printf(seq, " %dk rounding", mddev->chunk_sectors / 2);
357}
358
359
360static struct md_personality linear_personality =
361{
362    .name = "linear",
363    .level = LEVEL_LINEAR,
364    .owner = THIS_MODULE,
365    .make_request = linear_make_request,
366    .run = linear_run,
367    .stop = linear_stop,
368    .status = linear_status,
369    .hot_add_disk = linear_add,
370    .size = linear_size,
371};
372
373static int __init linear_init (void)
374{
375    return register_md_personality (&linear_personality);
376}
377
378static void linear_exit (void)
379{
380    unregister_md_personality (&linear_personality);
381}
382
383
384module_init(linear_init);
385module_exit(linear_exit);
386MODULE_LICENSE("GPL");
387MODULE_DESCRIPTION("Linear device concatenation personality for MD");
388MODULE_ALIAS("md-personality-1"); /* LINEAR - deprecated*/
389MODULE_ALIAS("md-linear");
390MODULE_ALIAS("md-level--1");
391

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