block: Consolidate phys_segment and hw_segment limits
[linux-2.6.git] / drivers / s390 / char / tape_block.c
1 /*
2  *  drivers/s390/char/tape_block.c
3  *    block device frontend for tape device driver
4  *
5  *  S390 and zSeries version
6  *    Copyright (C) 2001,2003 IBM Deutschland Entwicklung GmbH, IBM Corporation
7  *    Author(s): Carsten Otte <cotte@de.ibm.com>
8  *               Tuan Ngo-Anh <ngoanh@de.ibm.com>
9  *               Martin Schwidefsky <schwidefsky@de.ibm.com>
10  *               Stefan Bader <shbader@de.ibm.com>
11  */
12
13 #define KMSG_COMPONENT "tape"
14 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
15
16 #include <linux/fs.h>
17 #include <linux/module.h>
18 #include <linux/blkdev.h>
19 #include <linux/interrupt.h>
20 #include <linux/buffer_head.h>
21 #include <linux/kernel.h>
22
23 #include <asm/debug.h>
24
25 #define TAPE_DBF_AREA   tape_core_dbf
26
27 #include "tape.h"
28
29 #define TAPEBLOCK_MAX_SEC       100
30 #define TAPEBLOCK_MIN_REQUEUE   3
31
32 /*
33  * 2003/11/25  Stefan Bader <shbader@de.ibm.com>
34  *
35  * In 2.5/2.6 the block device request function is very likely to be called
36  * with disabled interrupts (e.g. generic_unplug_device). So the driver can't
37  * just call any function that tries to allocate CCW requests from that con-
38  * text since it might sleep. There are two choices to work around this:
39  *      a) do not allocate with kmalloc but use its own memory pool
40  *      b) take requests from the queue outside that context, knowing that
41  *         allocation might sleep
42  */
43
44 /*
45  * file operation structure for tape block frontend
46  */
47 static int tapeblock_open(struct block_device *, fmode_t);
48 static int tapeblock_release(struct gendisk *, fmode_t);
49 static int tapeblock_medium_changed(struct gendisk *);
50 static int tapeblock_revalidate_disk(struct gendisk *);
51
52 static const struct block_device_operations tapeblock_fops = {
53         .owner           = THIS_MODULE,
54         .open            = tapeblock_open,
55         .release         = tapeblock_release,
56         .media_changed   = tapeblock_medium_changed,
57         .revalidate_disk = tapeblock_revalidate_disk,
58 };
59
60 static int tapeblock_major = 0;
61
62 static void
63 tapeblock_trigger_requeue(struct tape_device *device)
64 {
65         /* Protect against rescheduling. */
66         if (atomic_cmpxchg(&device->blk_data.requeue_scheduled, 0, 1) != 0)
67                 return;
68         schedule_work(&device->blk_data.requeue_task);
69 }
70
71 /*
72  * Post finished request.
73  */
74 static void
75 __tapeblock_end_request(struct tape_request *ccw_req, void *data)
76 {
77         struct tape_device *device;
78         struct request *req;
79
80         DBF_LH(6, "__tapeblock_end_request()\n");
81
82         device = ccw_req->device;
83         req = (struct request *) data;
84         blk_end_request_all(req, (ccw_req->rc == 0) ? 0 : -EIO);
85         if (ccw_req->rc == 0)
86                 /* Update position. */
87                 device->blk_data.block_position =
88                   (blk_rq_pos(req) + blk_rq_sectors(req)) >> TAPEBLOCK_HSEC_S2B;
89         else
90                 /* We lost the position information due to an error. */
91                 device->blk_data.block_position = -1;
92         device->discipline->free_bread(ccw_req);
93         if (!list_empty(&device->req_queue) ||
94             blk_peek_request(device->blk_data.request_queue))
95                 tapeblock_trigger_requeue(device);
96 }
97
98 /*
99  * Feed the tape device CCW queue with requests supplied in a list.
100  */
101 static int
102 tapeblock_start_request(struct tape_device *device, struct request *req)
103 {
104         struct tape_request *   ccw_req;
105         int                     rc;
106
107         DBF_LH(6, "tapeblock_start_request(%p, %p)\n", device, req);
108
109         ccw_req = device->discipline->bread(device, req);
110         if (IS_ERR(ccw_req)) {
111                 DBF_EVENT(1, "TBLOCK: bread failed\n");
112                 blk_end_request_all(req, -EIO);
113                 return PTR_ERR(ccw_req);
114         }
115         ccw_req->callback = __tapeblock_end_request;
116         ccw_req->callback_data = (void *) req;
117         ccw_req->retries = TAPEBLOCK_RETRIES;
118
119         rc = tape_do_io_async(device, ccw_req);
120         if (rc) {
121                 /*
122                  * Start/enqueueing failed. No retries in
123                  * this case.
124                  */
125                 blk_end_request_all(req, -EIO);
126                 device->discipline->free_bread(ccw_req);
127         }
128
129         return rc;
130 }
131
132 /*
133  * Move requests from the block device request queue to the tape device ccw
134  * queue.
135  */
136 static void
137 tapeblock_requeue(struct work_struct *work) {
138         struct tape_blk_data *  blkdat;
139         struct tape_device *    device;
140         struct request_queue *  queue;
141         int                     nr_queued;
142         struct request *        req;
143         struct list_head *      l;
144         int                     rc;
145
146         blkdat = container_of(work, struct tape_blk_data, requeue_task);
147         device = blkdat->device;
148         if (!device)
149                 return;
150
151         spin_lock_irq(get_ccwdev_lock(device->cdev));
152         queue  = device->blk_data.request_queue;
153
154         /* Count number of requests on ccw queue. */
155         nr_queued = 0;
156         list_for_each(l, &device->req_queue)
157                 nr_queued++;
158         spin_unlock(get_ccwdev_lock(device->cdev));
159
160         spin_lock_irq(&device->blk_data.request_queue_lock);
161         while (
162                 !blk_queue_plugged(queue) &&
163                 blk_peek_request(queue) &&
164                 nr_queued < TAPEBLOCK_MIN_REQUEUE
165         ) {
166                 req = blk_fetch_request(queue);
167                 if (rq_data_dir(req) == WRITE) {
168                         DBF_EVENT(1, "TBLOCK: Rejecting write request\n");
169                         spin_unlock_irq(&device->blk_data.request_queue_lock);
170                         blk_end_request_all(req, -EIO);
171                         spin_lock_irq(&device->blk_data.request_queue_lock);
172                         continue;
173                 }
174                 nr_queued++;
175                 spin_unlock_irq(&device->blk_data.request_queue_lock);
176                 rc = tapeblock_start_request(device, req);
177                 spin_lock_irq(&device->blk_data.request_queue_lock);
178         }
179         spin_unlock_irq(&device->blk_data.request_queue_lock);
180         atomic_set(&device->blk_data.requeue_scheduled, 0);
181 }
182
183 /*
184  * Tape request queue function. Called from ll_rw_blk.c
185  */
186 static void
187 tapeblock_request_fn(struct request_queue *queue)
188 {
189         struct tape_device *device;
190
191         device = (struct tape_device *) queue->queuedata;
192         DBF_LH(6, "tapeblock_request_fn(device=%p)\n", device);
193         BUG_ON(device == NULL);
194         tapeblock_trigger_requeue(device);
195 }
196
197 /*
198  * This function is called for every new tapedevice
199  */
200 int
201 tapeblock_setup_device(struct tape_device * device)
202 {
203         struct tape_blk_data *  blkdat;
204         struct gendisk *        disk;
205         int                     rc;
206
207         blkdat = &device->blk_data;
208         blkdat->device = device;
209         spin_lock_init(&blkdat->request_queue_lock);
210         atomic_set(&blkdat->requeue_scheduled, 0);
211
212         blkdat->request_queue = blk_init_queue(
213                 tapeblock_request_fn,
214                 &blkdat->request_queue_lock
215         );
216         if (!blkdat->request_queue)
217                 return -ENOMEM;
218
219         elevator_exit(blkdat->request_queue->elevator);
220         rc = elevator_init(blkdat->request_queue, "noop");
221         if (rc)
222                 goto cleanup_queue;
223
224         blk_queue_logical_block_size(blkdat->request_queue, TAPEBLOCK_HSEC_SIZE);
225         blk_queue_max_hw_sectors(blkdat->request_queue, TAPEBLOCK_MAX_SEC);
226         blk_queue_max_segments(blkdat->request_queue, -1L);
227         blk_queue_max_segment_size(blkdat->request_queue, -1L);
228         blk_queue_segment_boundary(blkdat->request_queue, -1L);
229
230         disk = alloc_disk(1);
231         if (!disk) {
232                 rc = -ENOMEM;
233                 goto cleanup_queue;
234         }
235
236         disk->major = tapeblock_major;
237         disk->first_minor = device->first_minor;
238         disk->fops = &tapeblock_fops;
239         disk->private_data = tape_get_device(device);
240         disk->queue = blkdat->request_queue;
241         set_capacity(disk, 0);
242         sprintf(disk->disk_name, "btibm%d",
243                 device->first_minor / TAPE_MINORS_PER_DEV);
244
245         blkdat->disk = disk;
246         blkdat->medium_changed = 1;
247         blkdat->request_queue->queuedata = tape_get_device(device);
248
249         add_disk(disk);
250
251         tape_get_device(device);
252         INIT_WORK(&blkdat->requeue_task, tapeblock_requeue);
253
254         return 0;
255
256 cleanup_queue:
257         blk_cleanup_queue(blkdat->request_queue);
258         blkdat->request_queue = NULL;
259
260         return rc;
261 }
262
263 void
264 tapeblock_cleanup_device(struct tape_device *device)
265 {
266         flush_scheduled_work();
267         tape_put_device(device);
268
269         if (!device->blk_data.disk) {
270                 goto cleanup_queue;
271         }
272
273         del_gendisk(device->blk_data.disk);
274         device->blk_data.disk->private_data = NULL;
275         tape_put_device(device);
276         put_disk(device->blk_data.disk);
277
278         device->blk_data.disk = NULL;
279 cleanup_queue:
280         device->blk_data.request_queue->queuedata = NULL;
281         tape_put_device(device);
282
283         blk_cleanup_queue(device->blk_data.request_queue);
284         device->blk_data.request_queue = NULL;
285 }
286
287 /*
288  * Detect number of blocks of the tape.
289  * FIXME: can we extent this to detect the blocks size as well ?
290  */
291 static int
292 tapeblock_revalidate_disk(struct gendisk *disk)
293 {
294         struct tape_device *    device;
295         unsigned int            nr_of_blks;
296         int                     rc;
297
298         device = (struct tape_device *) disk->private_data;
299         BUG_ON(!device);
300
301         if (!device->blk_data.medium_changed)
302                 return 0;
303
304         rc = tape_mtop(device, MTFSFM, 1);
305         if (rc)
306                 return rc;
307
308         rc = tape_mtop(device, MTTELL, 1);
309         if (rc < 0)
310                 return rc;
311
312         pr_info("%s: Determining the size of the recorded area...\n",
313                 dev_name(&device->cdev->dev));
314         DBF_LH(3, "Image file ends at %d\n", rc);
315         nr_of_blks = rc;
316
317         /* This will fail for the first file. Catch the error by checking the
318          * position. */
319         tape_mtop(device, MTBSF, 1);
320
321         rc = tape_mtop(device, MTTELL, 1);
322         if (rc < 0)
323                 return rc;
324
325         if (rc > nr_of_blks)
326                 return -EINVAL;
327
328         DBF_LH(3, "Image file starts at %d\n", rc);
329         device->bof = rc;
330         nr_of_blks -= rc;
331
332         pr_info("%s: The size of the recorded area is %i blocks\n",
333                 dev_name(&device->cdev->dev), nr_of_blks);
334         set_capacity(device->blk_data.disk,
335                 nr_of_blks*(TAPEBLOCK_HSEC_SIZE/512));
336
337         device->blk_data.block_position = 0;
338         device->blk_data.medium_changed = 0;
339         return 0;
340 }
341
342 static int
343 tapeblock_medium_changed(struct gendisk *disk)
344 {
345         struct tape_device *device;
346
347         device = (struct tape_device *) disk->private_data;
348         DBF_LH(6, "tapeblock_medium_changed(%p) = %d\n",
349                 device, device->blk_data.medium_changed);
350
351         return device->blk_data.medium_changed;
352 }
353
354 /*
355  * Block frontend tape device open function.
356  */
357 static int
358 tapeblock_open(struct block_device *bdev, fmode_t mode)
359 {
360         struct gendisk *        disk = bdev->bd_disk;
361         struct tape_device *    device;
362         int                     rc;
363
364         device = tape_get_device(disk->private_data);
365
366         if (device->required_tapemarks) {
367                 DBF_EVENT(2, "TBLOCK: missing tapemarks\n");
368                 pr_warning("%s: Opening the tape failed because of missing "
369                            "end-of-file marks\n", dev_name(&device->cdev->dev));
370                 rc = -EPERM;
371                 goto put_device;
372         }
373
374         rc = tape_open(device);
375         if (rc)
376                 goto put_device;
377
378         rc = tapeblock_revalidate_disk(disk);
379         if (rc)
380                 goto release;
381
382         /*
383          * Note: The reference to <device> is hold until the release function
384          *       is called.
385          */
386         tape_state_set(device, TS_BLKUSE);
387         return 0;
388
389 release:
390         tape_release(device);
391  put_device:
392         tape_put_device(device);
393         return rc;
394 }
395
396 /*
397  * Block frontend tape device release function.
398  *
399  * Note: One reference to the tape device was made by the open function. So
400  *       we just get the pointer here and release the reference.
401  */
402 static int
403 tapeblock_release(struct gendisk *disk, fmode_t mode)
404 {
405         struct tape_device *device = disk->private_data;
406
407         tape_state_set(device, TS_IN_USE);
408         tape_release(device);
409         tape_put_device(device);
410
411         return 0;
412 }
413
414 /*
415  * Initialize block device frontend.
416  */
417 int
418 tapeblock_init(void)
419 {
420         int rc;
421
422         /* Register the tape major number to the kernel */
423         rc = register_blkdev(tapeblock_major, "tBLK");
424         if (rc < 0)
425                 return rc;
426
427         if (tapeblock_major == 0)
428                 tapeblock_major = rc;
429         return 0;
430 }
431
432 /*
433  * Deregister major for block device frontend
434  */
435 void
436 tapeblock_exit(void)
437 {
438         unregister_blkdev(tapeblock_major, "tBLK");
439 }