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Linux/include/linux/device-mapper.h

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  1 /*
  2  * Copyright (C) 2001 Sistina Software (UK) Limited.
  3  * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
  4  *
  5  * This file is released under the LGPL.
  6  */
  7 
  8 #ifndef _LINUX_DEVICE_MAPPER_H
  9 #define _LINUX_DEVICE_MAPPER_H
 10 
 11 #include <linux/bio.h>
 12 #include <linux/blkdev.h>
 13 #include <linux/math64.h>
 14 #include <linux/ratelimit.h>
 15 
 16 struct dm_dev;
 17 struct dm_target;
 18 struct dm_table;
 19 struct mapped_device;
 20 struct bio_vec;
 21 
 22 typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;
 23 
 24 union map_info {
 25         void *ptr;
 26 };
 27 
 28 /*
 29  * In the constructor the target parameter will already have the
 30  * table, type, begin and len fields filled in.
 31  */
 32 typedef int (*dm_ctr_fn) (struct dm_target *target,
 33                           unsigned int argc, char **argv);
 34 
 35 /*
 36  * The destructor doesn't need to free the dm_target, just
 37  * anything hidden ti->private.
 38  */
 39 typedef void (*dm_dtr_fn) (struct dm_target *ti);
 40 
 41 /*
 42  * The map function must return:
 43  * < 0: error
 44  * = 0: The target will handle the io by resubmitting it later
 45  * = 1: simple remap complete
 46  * = 2: The target wants to push back the io
 47  */
 48 typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio);
 49 typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
 50                                   union map_info *map_context);
 51 
 52 /*
 53  * Returns:
 54  * < 0 : error (currently ignored)
 55  * 0   : ended successfully
 56  * 1   : for some reason the io has still not completed (eg,
 57  *       multipath target might want to requeue a failed io).
 58  * 2   : The target wants to push back the io
 59  */
 60 typedef int (*dm_endio_fn) (struct dm_target *ti,
 61                             struct bio *bio, int error);
 62 typedef int (*dm_request_endio_fn) (struct dm_target *ti,
 63                                     struct request *clone, int error,
 64                                     union map_info *map_context);
 65 
 66 typedef void (*dm_presuspend_fn) (struct dm_target *ti);
 67 typedef void (*dm_postsuspend_fn) (struct dm_target *ti);
 68 typedef int (*dm_preresume_fn) (struct dm_target *ti);
 69 typedef void (*dm_resume_fn) (struct dm_target *ti);
 70 
 71 typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
 72                               unsigned status_flags, char *result, unsigned maxlen);
 73 
 74 typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);
 75 
 76 typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd,
 77                             unsigned long arg);
 78 
 79 typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
 80                             struct bio_vec *biovec, int max_size);
 81 
 82 /*
 83  * These iteration functions are typically used to check (and combine)
 84  * properties of underlying devices.
 85  * E.g. Does at least one underlying device support flush?
 86  *      Does any underlying device not support WRITE_SAME?
 87  *
 88  * The callout function is called once for each contiguous section of
 89  * an underlying device.  State can be maintained in *data.
 90  * Return non-zero to stop iterating through any further devices.
 91  */
 92 typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
 93                                            struct dm_dev *dev,
 94                                            sector_t start, sector_t len,
 95                                            void *data);
 96 
 97 /*
 98  * This function must iterate through each section of device used by the
 99  * target until it encounters a non-zero return code, which it then returns.
100  * Returns zero if no callout returned non-zero.
101  */
102 typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
103                                       iterate_devices_callout_fn fn,
104                                       void *data);
105 
106 typedef void (*dm_io_hints_fn) (struct dm_target *ti,
107                                 struct queue_limits *limits);
108 
109 /*
110  * Returns:
111  *    0: The target can handle the next I/O immediately.
112  *    1: The target can't handle the next I/O immediately.
113  */
114 typedef int (*dm_busy_fn) (struct dm_target *ti);
115 
116 void dm_error(const char *message);
117 
118 struct dm_dev {
119         struct block_device *bdev;
120         fmode_t mode;
121         char name[16];
122 };
123 
124 /*
125  * Constructors should call these functions to ensure destination devices
126  * are opened/closed correctly.
127  */
128 int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
129                   struct dm_dev **result);
130 void dm_put_device(struct dm_target *ti, struct dm_dev *d);
131 
132 /*
133  * Information about a target type
134  */
135 
136 struct target_type {
137         uint64_t features;
138         const char *name;
139         struct module *module;
140         unsigned version[3];
141         dm_ctr_fn ctr;
142         dm_dtr_fn dtr;
143         dm_map_fn map;
144         dm_map_request_fn map_rq;
145         dm_endio_fn end_io;
146         dm_request_endio_fn rq_end_io;
147         dm_presuspend_fn presuspend;
148         dm_postsuspend_fn postsuspend;
149         dm_preresume_fn preresume;
150         dm_resume_fn resume;
151         dm_status_fn status;
152         dm_message_fn message;
153         dm_ioctl_fn ioctl;
154         dm_merge_fn merge;
155         dm_busy_fn busy;
156         dm_iterate_devices_fn iterate_devices;
157         dm_io_hints_fn io_hints;
158 
159         /* For internal device-mapper use. */
160         struct list_head list;
161 };
162 
163 /*
164  * Target features
165  */
166 
167 /*
168  * Any table that contains an instance of this target must have only one.
169  */
170 #define DM_TARGET_SINGLETON             0x00000001
171 #define dm_target_needs_singleton(type) ((type)->features & DM_TARGET_SINGLETON)
172 
173 /*
174  * Indicates that a target does not support read-only devices.
175  */
176 #define DM_TARGET_ALWAYS_WRITEABLE      0x00000002
177 #define dm_target_always_writeable(type) \
178                 ((type)->features & DM_TARGET_ALWAYS_WRITEABLE)
179 
180 /*
181  * Any device that contains a table with an instance of this target may never
182  * have tables containing any different target type.
183  */
184 #define DM_TARGET_IMMUTABLE             0x00000004
185 #define dm_target_is_immutable(type)    ((type)->features & DM_TARGET_IMMUTABLE)
186 
187 /*
188  * Some targets need to be sent the same WRITE bio severals times so
189  * that they can send copies of it to different devices.  This function
190  * examines any supplied bio and returns the number of copies of it the
191  * target requires.
192  */
193 typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio);
194 
195 struct dm_target {
196         struct dm_table *table;
197         struct target_type *type;
198 
199         /* target limits */
200         sector_t begin;
201         sector_t len;
202 
203         /* If non-zero, maximum size of I/O submitted to a target. */
204         uint32_t max_io_len;
205 
206         /*
207          * A number of zero-length barrier bios that will be submitted
208          * to the target for the purpose of flushing cache.
209          *
210          * The bio number can be accessed with dm_bio_get_target_bio_nr.
211          * It is a responsibility of the target driver to remap these bios
212          * to the real underlying devices.
213          */
214         unsigned num_flush_bios;
215 
216         /*
217          * The number of discard bios that will be submitted to the target.
218          * The bio number can be accessed with dm_bio_get_target_bio_nr.
219          */
220         unsigned num_discard_bios;
221 
222         /*
223          * The number of WRITE SAME bios that will be submitted to the target.
224          * The bio number can be accessed with dm_bio_get_target_bio_nr.
225          */
226         unsigned num_write_same_bios;
227 
228         /*
229          * The minimum number of extra bytes allocated in each bio for the
230          * target to use.  dm_per_bio_data returns the data location.
231          */
232         unsigned per_bio_data_size;
233 
234         /*
235          * If defined, this function is called to find out how many
236          * duplicate bios should be sent to the target when writing
237          * data.
238          */
239         dm_num_write_bios_fn num_write_bios;
240 
241         /* target specific data */
242         void *private;
243 
244         /* Used to provide an error string from the ctr */
245         char *error;
246 
247         /*
248          * Set if this target needs to receive flushes regardless of
249          * whether or not its underlying devices have support.
250          */
251         bool flush_supported:1;
252 
253         /*
254          * Set if this target needs to receive discards regardless of
255          * whether or not its underlying devices have support.
256          */
257         bool discards_supported:1;
258 
259         /*
260          * Set if the target required discard bios to be split
261          * on max_io_len boundary.
262          */
263         bool split_discard_bios:1;
264 
265         /*
266          * Set if this target does not return zeroes on discarded blocks.
267          */
268         bool discard_zeroes_data_unsupported:1;
269 };
270 
271 /* Each target can link one of these into the table */
272 struct dm_target_callbacks {
273         struct list_head list;
274         int (*congested_fn) (struct dm_target_callbacks *, int);
275 };
276 
277 /*
278  * For bio-based dm.
279  * One of these is allocated for each bio.
280  * This structure shouldn't be touched directly by target drivers.
281  * It is here so that we can inline dm_per_bio_data and
282  * dm_bio_from_per_bio_data
283  */
284 struct dm_target_io {
285         struct dm_io *io;
286         struct dm_target *ti;
287         unsigned target_bio_nr;
288         unsigned *len_ptr;
289         struct bio clone;
290 };
291 
292 static inline void *dm_per_bio_data(struct bio *bio, size_t data_size)
293 {
294         return (char *)bio - offsetof(struct dm_target_io, clone) - data_size;
295 }
296 
297 static inline struct bio *dm_bio_from_per_bio_data(void *data, size_t data_size)
298 {
299         return (struct bio *)((char *)data + data_size + offsetof(struct dm_target_io, clone));
300 }
301 
302 static inline unsigned dm_bio_get_target_bio_nr(const struct bio *bio)
303 {
304         return container_of(bio, struct dm_target_io, clone)->target_bio_nr;
305 }
306 
307 int dm_register_target(struct target_type *t);
308 void dm_unregister_target(struct target_type *t);
309 
310 /*
311  * Target argument parsing.
312  */
313 struct dm_arg_set {
314         unsigned argc;
315         char **argv;
316 };
317 
318 /*
319  * The minimum and maximum value of a numeric argument, together with
320  * the error message to use if the number is found to be outside that range.
321  */
322 struct dm_arg {
323         unsigned min;
324         unsigned max;
325         char *error;
326 };
327 
328 /*
329  * Validate the next argument, either returning it as *value or, if invalid,
330  * returning -EINVAL and setting *error.
331  */
332 int dm_read_arg(struct dm_arg *arg, struct dm_arg_set *arg_set,
333                 unsigned *value, char **error);
334 
335 /*
336  * Process the next argument as the start of a group containing between
337  * arg->min and arg->max further arguments. Either return the size as
338  * *num_args or, if invalid, return -EINVAL and set *error.
339  */
340 int dm_read_arg_group(struct dm_arg *arg, struct dm_arg_set *arg_set,
341                       unsigned *num_args, char **error);
342 
343 /*
344  * Return the current argument and shift to the next.
345  */
346 const char *dm_shift_arg(struct dm_arg_set *as);
347 
348 /*
349  * Move through num_args arguments.
350  */
351 void dm_consume_args(struct dm_arg_set *as, unsigned num_args);
352 
353 /*-----------------------------------------------------------------
354  * Functions for creating and manipulating mapped devices.
355  * Drop the reference with dm_put when you finish with the object.
356  *---------------------------------------------------------------*/
357 
358 /*
359  * DM_ANY_MINOR chooses the next available minor number.
360  */
361 #define DM_ANY_MINOR (-1)
362 int dm_create(int minor, struct mapped_device **md);
363 
364 /*
365  * Reference counting for md.
366  */
367 struct mapped_device *dm_get_md(dev_t dev);
368 void dm_get(struct mapped_device *md);
369 void dm_put(struct mapped_device *md);
370 
371 /*
372  * An arbitrary pointer may be stored alongside a mapped device.
373  */
374 void dm_set_mdptr(struct mapped_device *md, void *ptr);
375 void *dm_get_mdptr(struct mapped_device *md);
376 
377 /*
378  * A device can still be used while suspended, but I/O is deferred.
379  */
380 int dm_suspend(struct mapped_device *md, unsigned suspend_flags);
381 int dm_resume(struct mapped_device *md);
382 
383 /*
384  * Event functions.
385  */
386 uint32_t dm_get_event_nr(struct mapped_device *md);
387 int dm_wait_event(struct mapped_device *md, int event_nr);
388 uint32_t dm_next_uevent_seq(struct mapped_device *md);
389 void dm_uevent_add(struct mapped_device *md, struct list_head *elist);
390 
391 /*
392  * Info functions.
393  */
394 const char *dm_device_name(struct mapped_device *md);
395 int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid);
396 struct gendisk *dm_disk(struct mapped_device *md);
397 int dm_suspended(struct dm_target *ti);
398 int dm_noflush_suspending(struct dm_target *ti);
399 void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors);
400 union map_info *dm_get_rq_mapinfo(struct request *rq);
401 
402 struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
403 
404 /*
405  * Geometry functions.
406  */
407 int dm_get_geometry(struct mapped_device *md, struct hd_geometry *geo);
408 int dm_set_geometry(struct mapped_device *md, struct hd_geometry *geo);
409 
410 /*-----------------------------------------------------------------
411  * Functions for manipulating device-mapper tables.
412  *---------------------------------------------------------------*/
413 
414 /*
415  * First create an empty table.
416  */
417 int dm_table_create(struct dm_table **result, fmode_t mode,
418                     unsigned num_targets, struct mapped_device *md);
419 
420 /*
421  * Then call this once for each target.
422  */
423 int dm_table_add_target(struct dm_table *t, const char *type,
424                         sector_t start, sector_t len, char *params);
425 
426 /*
427  * Target_ctr should call this if it needs to add any callbacks.
428  */
429 void dm_table_add_target_callbacks(struct dm_table *t, struct dm_target_callbacks *cb);
430 
431 /*
432  * Finally call this to make the table ready for use.
433  */
434 int dm_table_complete(struct dm_table *t);
435 
436 /*
437  * Target may require that it is never sent I/O larger than len.
438  */
439 int __must_check dm_set_target_max_io_len(struct dm_target *ti, sector_t len);
440 
441 /*
442  * Table reference counting.
443  */
444 struct dm_table *dm_get_live_table(struct mapped_device *md, int *srcu_idx);
445 void dm_put_live_table(struct mapped_device *md, int srcu_idx);
446 void dm_sync_table(struct mapped_device *md);
447 
448 /*
449  * Queries
450  */
451 sector_t dm_table_get_size(struct dm_table *t);
452 unsigned int dm_table_get_num_targets(struct dm_table *t);
453 fmode_t dm_table_get_mode(struct dm_table *t);
454 struct mapped_device *dm_table_get_md(struct dm_table *t);
455 
456 /*
457  * Trigger an event.
458  */
459 void dm_table_event(struct dm_table *t);
460 
461 /*
462  * Run the queue for request-based targets.
463  */
464 void dm_table_run_md_queue_async(struct dm_table *t);
465 
466 /*
467  * The device must be suspended before calling this method.
468  * Returns the previous table, which the caller must destroy.
469  */
470 struct dm_table *dm_swap_table(struct mapped_device *md,
471                                struct dm_table *t);
472 
473 /*
474  * A wrapper around vmalloc.
475  */
476 void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size);
477 
478 /*-----------------------------------------------------------------
479  * Macros.
480  *---------------------------------------------------------------*/
481 #define DM_NAME "device-mapper"
482 
483 #ifdef CONFIG_PRINTK
484 extern struct ratelimit_state dm_ratelimit_state;
485 
486 #define dm_ratelimit()  __ratelimit(&dm_ratelimit_state)
487 #else
488 #define dm_ratelimit()  0
489 #endif
490 
491 #define DMCRIT(f, arg...) \
492         printk(KERN_CRIT DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
493 
494 #define DMERR(f, arg...) \
495         printk(KERN_ERR DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
496 #define DMERR_LIMIT(f, arg...) \
497         do { \
498                 if (dm_ratelimit())     \
499                         printk(KERN_ERR DM_NAME ": " DM_MSG_PREFIX ": " \
500                                f "\n", ## arg); \
501         } while (0)
502 
503 #define DMWARN(f, arg...) \
504         printk(KERN_WARNING DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
505 #define DMWARN_LIMIT(f, arg...) \
506         do { \
507                 if (dm_ratelimit())     \
508                         printk(KERN_WARNING DM_NAME ": " DM_MSG_PREFIX ": " \
509                                f "\n", ## arg); \
510         } while (0)
511 
512 #define DMINFO(f, arg...) \
513         printk(KERN_INFO DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
514 #define DMINFO_LIMIT(f, arg...) \
515         do { \
516                 if (dm_ratelimit())     \
517                         printk(KERN_INFO DM_NAME ": " DM_MSG_PREFIX ": " f \
518                                "\n", ## arg); \
519         } while (0)
520 
521 #ifdef CONFIG_DM_DEBUG
522 #  define DMDEBUG(f, arg...) \
523         printk(KERN_DEBUG DM_NAME ": " DM_MSG_PREFIX " DEBUG: " f "\n", ## arg)
524 #  define DMDEBUG_LIMIT(f, arg...) \
525         do { \
526                 if (dm_ratelimit())     \
527                         printk(KERN_DEBUG DM_NAME ": " DM_MSG_PREFIX ": " f \
528                                "\n", ## arg); \
529         } while (0)
530 #else
531 #  define DMDEBUG(f, arg...) do {} while (0)
532 #  define DMDEBUG_LIMIT(f, arg...) do {} while (0)
533 #endif
534 
535 #define DMEMIT(x...) sz += ((sz >= maxlen) ? \
536                           0 : scnprintf(result + sz, maxlen - sz, x))
537 
538 #define SECTOR_SHIFT 9
539 
540 /*
541  * Definitions of return values from target end_io function.
542  */
543 #define DM_ENDIO_INCOMPLETE     1
544 #define DM_ENDIO_REQUEUE        2
545 
546 /*
547  * Definitions of return values from target map function.
548  */
549 #define DM_MAPIO_SUBMITTED      0
550 #define DM_MAPIO_REMAPPED       1
551 #define DM_MAPIO_REQUEUE        DM_ENDIO_REQUEUE
552 
553 #define dm_sector_div64(x, y)( \
554 { \
555         u64 _res; \
556         (x) = div64_u64_rem(x, y, &_res); \
557         _res; \
558 } \
559 )
560 
561 /*
562  * Ceiling(n / sz)
563  */
564 #define dm_div_up(n, sz) (((n) + (sz) - 1) / (sz))
565 
566 #define dm_sector_div_up(n, sz) ( \
567 { \
568         sector_t _r = ((n) + (sz) - 1); \
569         sector_div(_r, (sz)); \
570         _r; \
571 } \
572 )
573 
574 /*
575  * ceiling(n / size) * size
576  */
577 #define dm_round_up(n, sz) (dm_div_up((n), (sz)) * (sz))
578 
579 #define dm_array_too_big(fixed, obj, num) \
580         ((num) > (UINT_MAX - (fixed)) / (obj))
581 
582 /*
583  * Sector offset taken relative to the start of the target instead of
584  * relative to the start of the device.
585  */
586 #define dm_target_offset(ti, sector) ((sector) - (ti)->begin)
587 
588 static inline sector_t to_sector(unsigned long n)
589 {
590         return (n >> SECTOR_SHIFT);
591 }
592 
593 static inline unsigned long to_bytes(sector_t n)
594 {
595         return (n << SECTOR_SHIFT);
596 }
597 
598 /*-----------------------------------------------------------------
599  * Helper for block layer and dm core operations
600  *---------------------------------------------------------------*/
601 void dm_dispatch_request(struct request *rq);
602 void dm_requeue_unmapped_request(struct request *rq);
603 void dm_kill_unmapped_request(struct request *rq, int error);
604 int dm_underlying_device_busy(struct request_queue *q);
605 
606 #endif  /* _LINUX_DEVICE_MAPPER_H */
607 

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