blob: a49a9c8f2cb1faffe5c16d782ea793839062dcc4 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 * (C) 2003 David Woodhouse <dwmw2@infradead.org>
3 *
4 * Interface to Linux 2.5 block layer for MTD 'translation layers'.
5 *
6 */
7
8#include <linux/kernel.h>
9#include <linux/slab.h>
10#include <linux/module.h>
11#include <linux/list.h>
12#include <linux/fs.h>
13#include <linux/mtd/blktrans.h>
14#include <linux/mtd/mtd.h>
15#include <linux/blkdev.h>
16#include <linux/blkpg.h>
Rafael J. Wysocki83144182007-07-17 04:03:35 -070017#include <linux/freezer.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018#include <linux/spinlock.h>
19#include <linux/hdreg.h>
20#include <linux/init.h>
Ingo Molnar48b19262006-03-31 02:29:41 -080021#include <linux/mutex.h>
Eric W. Biederman99f9b242007-04-19 01:58:33 -060022#include <linux/kthread.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023#include <asm/uaccess.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070024
Ben Dooks356d70f2007-05-28 20:28:34 +010025#include "mtdcore.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070026
Ben Dooks356d70f2007-05-28 20:28:34 +010027static LIST_HEAD(blktrans_majors);
Linus Torvalds1da177e2005-04-16 15:20:36 -070028
29struct mtd_blkcore_priv {
Christoph Hellwig3e67fe42007-04-22 20:40:57 +010030 struct task_struct *thread;
Linus Torvalds1da177e2005-04-16 15:20:36 -070031 struct request_queue *rq;
32 spinlock_t queue_lock;
33};
34
David Woodhouseeae9acd2008-08-05 18:08:25 +010035static int blktrans_discard_request(struct request_queue *q,
36 struct request *req)
37{
38 req->cmd_type = REQ_TYPE_LINUX_BLOCK;
39 req->cmd[0] = REQ_LB_OP_DISCARD;
40 return 0;
41}
42
Linus Torvalds1da177e2005-04-16 15:20:36 -070043static int do_blktrans_request(struct mtd_blktrans_ops *tr,
44 struct mtd_blktrans_dev *dev,
45 struct request *req)
46{
47 unsigned long block, nsect;
48 char *buf;
49
Richard Purdie19187672006-10-27 09:09:33 +010050 block = req->sector << 9 >> tr->blkshift;
51 nsect = req->current_nr_sectors << 9 >> tr->blkshift;
52
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 buf = req->buffer;
54
David Woodhouseeae9acd2008-08-05 18:08:25 +010055 if (req->cmd_type == REQ_TYPE_LINUX_BLOCK &&
56 req->cmd[0] == REQ_LB_OP_DISCARD)
57 return !tr->discard(dev, block, nsect);
58
Jens Axboe4aff5e22006-08-10 08:44:47 +020059 if (!blk_fs_request(req))
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 return 0;
61
Richard Purdie19187672006-10-27 09:09:33 +010062 if (req->sector + req->current_nr_sectors > get_capacity(req->rq_disk))
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 return 0;
64
65 switch(rq_data_dir(req)) {
66 case READ:
Richard Purdie19187672006-10-27 09:09:33 +010067 for (; nsect > 0; nsect--, block++, buf += tr->blksize)
Linus Torvalds1da177e2005-04-16 15:20:36 -070068 if (tr->readsect(dev, block, buf))
69 return 0;
70 return 1;
71
72 case WRITE:
73 if (!tr->writesect)
74 return 0;
75
Richard Purdie19187672006-10-27 09:09:33 +010076 for (; nsect > 0; nsect--, block++, buf += tr->blksize)
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 if (tr->writesect(dev, block, buf))
78 return 0;
79 return 1;
80
81 default:
Jeff Garzik9a292302006-10-01 12:16:00 -040082 printk(KERN_NOTICE "Unknown request %u\n", rq_data_dir(req));
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 return 0;
84 }
85}
86
87static int mtd_blktrans_thread(void *arg)
88{
89 struct mtd_blktrans_ops *tr = arg;
90 struct request_queue *rq = tr->blkcore_priv->rq;
91
92 /* we might get involved when memory gets low, so use PF_MEMALLOC */
Rafael J. Wysocki83144182007-07-17 04:03:35 -070093 current->flags |= PF_MEMALLOC;
Linus Torvalds1da177e2005-04-16 15:20:36 -070094
Linus Torvalds1da177e2005-04-16 15:20:36 -070095 spin_lock_irq(rq->queue_lock);
Christoph Hellwig3e67fe42007-04-22 20:40:57 +010096 while (!kthread_should_stop()) {
Linus Torvalds1da177e2005-04-16 15:20:36 -070097 struct request *req;
98 struct mtd_blktrans_dev *dev;
99 int res = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100
101 req = elv_next_request(rq);
102
103 if (!req) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 set_current_state(TASK_INTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 spin_unlock_irq(rq->queue_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 schedule();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107 spin_lock_irq(rq->queue_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108 continue;
109 }
110
111 dev = req->rq_disk->private_data;
112 tr = dev->tr;
113
114 spin_unlock_irq(rq->queue_lock);
115
Ingo Molnar48b19262006-03-31 02:29:41 -0800116 mutex_lock(&dev->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117 res = do_blktrans_request(tr, dev, req);
Ingo Molnar48b19262006-03-31 02:29:41 -0800118 mutex_unlock(&dev->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
120 spin_lock_irq(rq->queue_lock);
121
122 end_request(req, res);
123 }
124 spin_unlock_irq(rq->queue_lock);
125
Christoph Hellwig3e67fe42007-04-22 20:40:57 +0100126 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127}
128
129static void mtd_blktrans_request(struct request_queue *rq)
130{
131 struct mtd_blktrans_ops *tr = rq->queuedata;
Christoph Hellwig3e67fe42007-04-22 20:40:57 +0100132 wake_up_process(tr->blkcore_priv->thread);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133}
134
135
Al Viroaf0e2a02008-03-02 10:35:06 -0500136static int blktrans_open(struct block_device *bdev, fmode_t mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137{
Al Viroaf0e2a02008-03-02 10:35:06 -0500138 struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
139 struct mtd_blktrans_ops *tr = dev->tr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140 int ret = -ENODEV;
141
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142 if (!try_module_get(dev->mtd->owner))
143 goto out;
144
145 if (!try_module_get(tr->owner))
146 goto out_tr;
147
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000148 /* FIXME: Locking. A hot pluggable device can go away
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149 (del_mtd_device can be called for it) without its module
150 being unloaded. */
151 dev->mtd->usecount++;
152
153 ret = 0;
154 if (tr->open && (ret = tr->open(dev))) {
155 dev->mtd->usecount--;
156 module_put(dev->mtd->owner);
157 out_tr:
158 module_put(tr->owner);
159 }
160 out:
161 return ret;
162}
163
Al Viroaf0e2a02008-03-02 10:35:06 -0500164static int blktrans_release(struct gendisk *disk, fmode_t mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165{
Al Viroaf0e2a02008-03-02 10:35:06 -0500166 struct mtd_blktrans_dev *dev = disk->private_data;
167 struct mtd_blktrans_ops *tr = dev->tr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168 int ret = 0;
169
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 if (tr->release)
171 ret = tr->release(dev);
172
173 if (!ret) {
174 dev->mtd->usecount--;
175 module_put(dev->mtd->owner);
176 module_put(tr->owner);
177 }
178
179 return ret;
180}
181
Christoph Hellwiga885c8c2006-01-08 01:02:50 -0800182static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
183{
184 struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
185
186 if (dev->tr->getgeo)
187 return dev->tr->getgeo(dev, geo);
188 return -ENOTTY;
189}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190
Al Viroaf0e2a02008-03-02 10:35:06 -0500191static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 unsigned int cmd, unsigned long arg)
193{
Al Viroaf0e2a02008-03-02 10:35:06 -0500194 struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195 struct mtd_blktrans_ops *tr = dev->tr;
196
197 switch (cmd) {
198 case BLKFLSBUF:
199 if (tr->flush)
200 return tr->flush(dev);
201 /* The core code did the work, we had nothing to do. */
202 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 default:
204 return -ENOTTY;
205 }
206}
207
Ben Dooks8f026f72007-05-28 19:51:59 +0100208static struct block_device_operations mtd_blktrans_ops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209 .owner = THIS_MODULE,
Al Viroaf0e2a02008-03-02 10:35:06 -0500210 .open = blktrans_open,
211 .release = blktrans_release,
212 .locked_ioctl = blktrans_ioctl,
Christoph Hellwiga885c8c2006-01-08 01:02:50 -0800213 .getgeo = blktrans_getgeo,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214};
215
216int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
217{
218 struct mtd_blktrans_ops *tr = new->tr;
Chris Malley71a928c2008-05-19 20:11:50 +0100219 struct mtd_blktrans_dev *d;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220 int last_devnum = -1;
221 struct gendisk *gd;
222
Jean Delvareb3561ea2007-05-08 00:30:46 -0700223 if (mutex_trylock(&mtd_table_mutex)) {
Ingo Molnar48b19262006-03-31 02:29:41 -0800224 mutex_unlock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 BUG();
226 }
227
Chris Malley71a928c2008-05-19 20:11:50 +0100228 list_for_each_entry(d, &tr->devs, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 if (new->devnum == -1) {
230 /* Use first free number */
231 if (d->devnum != last_devnum+1) {
232 /* Found a free devnum. Plug it in here */
233 new->devnum = last_devnum+1;
234 list_add_tail(&new->list, &d->list);
235 goto added;
236 }
237 } else if (d->devnum == new->devnum) {
238 /* Required number taken */
239 return -EBUSY;
240 } else if (d->devnum > new->devnum) {
241 /* Required number was free */
242 list_add_tail(&new->list, &d->list);
243 goto added;
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000244 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700245 last_devnum = d->devnum;
246 }
247 if (new->devnum == -1)
248 new->devnum = last_devnum+1;
249
250 if ((new->devnum << tr->part_bits) > 256) {
251 return -EBUSY;
252 }
253
Linus Torvalds1da177e2005-04-16 15:20:36 -0700254 list_add_tail(&new->list, &tr->devs);
255 added:
David Woodhousece37ab42007-12-03 12:46:12 +0000256 mutex_init(&new->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 if (!tr->writesect)
258 new->readonly = 1;
259
260 gd = alloc_disk(1 << tr->part_bits);
261 if (!gd) {
262 list_del(&new->list);
263 return -ENOMEM;
264 }
265 gd->major = tr->major;
266 gd->first_minor = (new->devnum) << tr->part_bits;
267 gd->fops = &mtd_blktrans_ops;
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000268
Todd Poynor65a8de32005-07-29 20:42:07 +0100269 if (tr->part_bits)
270 if (new->devnum < 26)
271 snprintf(gd->disk_name, sizeof(gd->disk_name),
272 "%s%c", tr->name, 'a' + new->devnum);
273 else
274 snprintf(gd->disk_name, sizeof(gd->disk_name),
275 "%s%c%c", tr->name,
276 'a' - 1 + new->devnum / 26,
277 'a' + new->devnum % 26);
278 else
279 snprintf(gd->disk_name, sizeof(gd->disk_name),
280 "%s%d", tr->name, new->devnum);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281
282 /* 2.5 has capacity in units of 512 bytes while still
283 having BLOCK_SIZE_BITS set to 10. Just to keep us amused. */
Richard Purdie19187672006-10-27 09:09:33 +0100284 set_capacity(gd, (new->size * tr->blksize) >> 9);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285
286 gd->private_data = new;
287 new->blkcore_priv = gd;
288 gd->queue = tr->blkcore_priv->rq;
David Brownell1f24b5a2009-03-26 00:42:41 -0700289 gd->driverfs_dev = new->mtd->dev.parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700290
291 if (new->readonly)
292 set_disk_ro(gd, 1);
293
294 add_disk(gd);
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000295
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296 return 0;
297}
298
299int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
300{
Jean Delvareb3561ea2007-05-08 00:30:46 -0700301 if (mutex_trylock(&mtd_table_mutex)) {
Ingo Molnar48b19262006-03-31 02:29:41 -0800302 mutex_unlock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 BUG();
304 }
305
306 list_del(&old->list);
307
308 del_gendisk(old->blkcore_priv);
309 put_disk(old->blkcore_priv);
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000310
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 return 0;
312}
313
314static void blktrans_notify_remove(struct mtd_info *mtd)
315{
Chris Malley71a928c2008-05-19 20:11:50 +0100316 struct mtd_blktrans_ops *tr;
317 struct mtd_blktrans_dev *dev, *next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318
Chris Malley71a928c2008-05-19 20:11:50 +0100319 list_for_each_entry(tr, &blktrans_majors, list)
320 list_for_each_entry_safe(dev, next, &tr->devs, list)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700321 if (dev->mtd == mtd)
322 tr->remove_dev(dev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323}
324
325static void blktrans_notify_add(struct mtd_info *mtd)
326{
Chris Malley71a928c2008-05-19 20:11:50 +0100327 struct mtd_blktrans_ops *tr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328
329 if (mtd->type == MTD_ABSENT)
330 return;
331
Chris Malley71a928c2008-05-19 20:11:50 +0100332 list_for_each_entry(tr, &blktrans_majors, list)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333 tr->add_mtd(tr, mtd);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334}
335
336static struct mtd_notifier blktrans_notifier = {
337 .add = blktrans_notify_add,
338 .remove = blktrans_notify_remove,
339};
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000340
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
342{
343 int ret, i;
344
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000345 /* Register the notifier if/when the first device type is
Linus Torvalds1da177e2005-04-16 15:20:36 -0700346 registered, to prevent the link/init ordering from fucking
347 us over. */
348 if (!blktrans_notifier.list.next)
349 register_mtd_user(&blktrans_notifier);
350
Burman Yan95b93a02006-11-15 21:10:29 +0200351 tr->blkcore_priv = kzalloc(sizeof(*tr->blkcore_priv), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352 if (!tr->blkcore_priv)
353 return -ENOMEM;
354
Ingo Molnar48b19262006-03-31 02:29:41 -0800355 mutex_lock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356
357 ret = register_blkdev(tr->major, tr->name);
358 if (ret) {
359 printk(KERN_WARNING "Unable to register %s block device on major %d: %d\n",
360 tr->name, tr->major, ret);
361 kfree(tr->blkcore_priv);
Ingo Molnar48b19262006-03-31 02:29:41 -0800362 mutex_unlock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363 return ret;
364 }
365 spin_lock_init(&tr->blkcore_priv->queue_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366
367 tr->blkcore_priv->rq = blk_init_queue(mtd_blktrans_request, &tr->blkcore_priv->queue_lock);
368 if (!tr->blkcore_priv->rq) {
369 unregister_blkdev(tr->major, tr->name);
370 kfree(tr->blkcore_priv);
Ingo Molnar48b19262006-03-31 02:29:41 -0800371 mutex_unlock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372 return -ENOMEM;
373 }
374
375 tr->blkcore_priv->rq->queuedata = tr;
Richard Purdie19187672006-10-27 09:09:33 +0100376 blk_queue_hardsect_size(tr->blkcore_priv->rq, tr->blksize);
David Woodhouseeae9acd2008-08-05 18:08:25 +0100377 if (tr->discard)
378 blk_queue_set_discard(tr->blkcore_priv->rq,
379 blktrans_discard_request);
380
Richard Purdie19187672006-10-27 09:09:33 +0100381 tr->blkshift = ffs(tr->blksize) - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382
Christoph Hellwig3e67fe42007-04-22 20:40:57 +0100383 tr->blkcore_priv->thread = kthread_run(mtd_blktrans_thread, tr,
384 "%sd", tr->name);
385 if (IS_ERR(tr->blkcore_priv->thread)) {
Marcin Slusarz2cf3a1142009-03-28 18:44:24 +0100386 int ret = PTR_ERR(tr->blkcore_priv->thread);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 blk_cleanup_queue(tr->blkcore_priv->rq);
388 unregister_blkdev(tr->major, tr->name);
389 kfree(tr->blkcore_priv);
Ingo Molnar48b19262006-03-31 02:29:41 -0800390 mutex_unlock(&mtd_table_mutex);
Marcin Slusarz2cf3a1142009-03-28 18:44:24 +0100391 return ret;
Thomas Gleixner97894cd2005-11-07 11:15:26 +0000392 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393
Linus Torvalds1da177e2005-04-16 15:20:36 -0700394 INIT_LIST_HEAD(&tr->devs);
395 list_add(&tr->list, &blktrans_majors);
396
397 for (i=0; i<MAX_MTD_DEVICES; i++) {
398 if (mtd_table[i] && mtd_table[i]->type != MTD_ABSENT)
399 tr->add_mtd(tr, mtd_table[i]);
400 }
401
Ingo Molnar48b19262006-03-31 02:29:41 -0800402 mutex_unlock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403
404 return 0;
405}
406
407int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)
408{
Chris Malley71a928c2008-05-19 20:11:50 +0100409 struct mtd_blktrans_dev *dev, *next;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410
Ingo Molnar48b19262006-03-31 02:29:41 -0800411 mutex_lock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700412
413 /* Clean up the kernel thread */
Christoph Hellwig3e67fe42007-04-22 20:40:57 +0100414 kthread_stop(tr->blkcore_priv->thread);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415
416 /* Remove it from the list of active majors */
417 list_del(&tr->list);
418
Chris Malley71a928c2008-05-19 20:11:50 +0100419 list_for_each_entry_safe(dev, next, &tr->devs, list)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700420 tr->remove_dev(dev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700421
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 blk_cleanup_queue(tr->blkcore_priv->rq);
423 unregister_blkdev(tr->major, tr->name);
424
Ingo Molnar48b19262006-03-31 02:29:41 -0800425 mutex_unlock(&mtd_table_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426
427 kfree(tr->blkcore_priv);
428
Eric Sesterhenn373ebfb2006-03-26 18:15:12 +0200429 BUG_ON(!list_empty(&tr->devs));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 return 0;
431}
432
433static void __exit mtd_blktrans_exit(void)
434{
435 /* No race here -- if someone's currently in register_mtd_blktrans
436 we're screwed anyway. */
437 if (blktrans_notifier.list.next)
438 unregister_mtd_user(&blktrans_notifier);
439}
440
441module_exit(mtd_blktrans_exit);
442
443EXPORT_SYMBOL_GPL(register_mtd_blktrans);
444EXPORT_SYMBOL_GPL(deregister_mtd_blktrans);
445EXPORT_SYMBOL_GPL(add_mtd_blktrans_dev);
446EXPORT_SYMBOL_GPL(del_mtd_blktrans_dev);
447
448MODULE_AUTHOR("David Woodhouse <dwmw2@infradead.org>");
449MODULE_LICENSE("GPL");
450MODULE_DESCRIPTION("Common interface to block layer for MTD 'translation layers'");