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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 typedef int (*dm_clone_and_map_request_fn) (struct dm_target *ti,
 52                                             struct request *rq,
 53                                             union map_info *map_context,
 54                                             struct request **clone);
 55 typedef void (*dm_release_clone_request_fn) (struct request *clone);
 56 
 57 /*
 58  * Returns:
 59  * < 0 : error (currently ignored)
 60  * 0   : ended successfully
 61  * 1   : for some reason the io has still not completed (eg,
 62  *       multipath target might want to requeue a failed io).
 63  * 2   : The target wants to push back the io
 64  */
 65 typedef int (*dm_endio_fn) (struct dm_target *ti,
 66                             struct bio *bio, int error);
 67 typedef int (*dm_request_endio_fn) (struct dm_target *ti,
 68                                     struct request *clone, int error,
 69                                     union map_info *map_context);
 70 
 71 typedef void (*dm_presuspend_fn) (struct dm_target *ti);
 72 typedef void (*dm_presuspend_undo_fn) (struct dm_target *ti);
 73 typedef void (*dm_postsuspend_fn) (struct dm_target *ti);
 74 typedef int (*dm_preresume_fn) (struct dm_target *ti);
 75 typedef void (*dm_resume_fn) (struct dm_target *ti);
 76 
 77 typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
 78                               unsigned status_flags, char *result, unsigned maxlen);
 79 
 80 typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);
 81 
 82 typedef int (*dm_prepare_ioctl_fn) (struct dm_target *ti,
 83                             struct block_device **bdev, fmode_t *mode);
 84 
 85 /*
 86  * These iteration functions are typically used to check (and combine)
 87  * properties of underlying devices.
 88  * E.g. Does at least one underlying device support flush?
 89  *      Does any underlying device not support WRITE_SAME?
 90  *
 91  * The callout function is called once for each contiguous section of
 92  * an underlying device.  State can be maintained in *data.
 93  * Return non-zero to stop iterating through any further devices.
 94  */
 95 typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
 96                                            struct dm_dev *dev,
 97                                            sector_t start, sector_t len,
 98                                            void *data);
 99 
100 /*
101  * This function must iterate through each section of device used by the
102  * target until it encounters a non-zero return code, which it then returns.
103  * Returns zero if no callout returned non-zero.
104  */
105 typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
106                                       iterate_devices_callout_fn fn,
107                                       void *data);
108 
109 typedef void (*dm_io_hints_fn) (struct dm_target *ti,
110                                 struct queue_limits *limits);
111 
112 /*
113  * Returns:
114  *    0: The target can handle the next I/O immediately.
115  *    1: The target can't handle the next I/O immediately.
116  */
117 typedef int (*dm_busy_fn) (struct dm_target *ti);
118 
119 void dm_error(const char *message);
120 
121 struct dm_dev {
122         struct block_device *bdev;
123         fmode_t mode;
124         char name[16];
125 };
126 
127 dev_t dm_get_dev_t(const char *path);
128 
129 /*
130  * Constructors should call these functions to ensure destination devices
131  * are opened/closed correctly.
132  */
133 int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
134                   struct dm_dev **result);
135 void dm_put_device(struct dm_target *ti, struct dm_dev *d);
136 
137 /*
138  * Information about a target type
139  */
140 
141 struct target_type {
142         uint64_t features;
143         const char *name;
144         struct module *module;
145         unsigned version[3];
146         dm_ctr_fn ctr;
147         dm_dtr_fn dtr;
148         dm_map_fn map;
149         dm_map_request_fn map_rq;
150         dm_clone_and_map_request_fn clone_and_map_rq;
151         dm_release_clone_request_fn release_clone_rq;
152         dm_endio_fn end_io;
153         dm_request_endio_fn rq_end_io;
154         dm_presuspend_fn presuspend;
155         dm_presuspend_undo_fn presuspend_undo;
156         dm_postsuspend_fn postsuspend;
157         dm_preresume_fn preresume;
158         dm_resume_fn resume;
159         dm_status_fn status;
160         dm_message_fn message;
161         dm_prepare_ioctl_fn prepare_ioctl;
162         dm_busy_fn busy;
163         dm_iterate_devices_fn iterate_devices;
164         dm_io_hints_fn io_hints;
165 
166         /* For internal device-mapper use. */
167         struct list_head list;
168 };
169 
170 /*
171  * Target features
172  */
173 
174 /*
175  * Any table that contains an instance of this target must have only one.
176  */
177 #define DM_TARGET_SINGLETON             0x00000001
178 #define dm_target_needs_singleton(type) ((type)->features & DM_TARGET_SINGLETON)
179 
180 /*
181  * Indicates that a target does not support read-only devices.
182  */
183 #define DM_TARGET_ALWAYS_WRITEABLE      0x00000002
184 #define dm_target_always_writeable(type) \
185                 ((type)->features & DM_TARGET_ALWAYS_WRITEABLE)
186 
187 /*
188  * Any device that contains a table with an instance of this target may never
189  * have tables containing any different target type.
190  */
191 #define DM_TARGET_IMMUTABLE             0x00000004
192 #define dm_target_is_immutable(type)    ((type)->features & DM_TARGET_IMMUTABLE)
193 
194 /*
195  * Indicates that a target may replace any target; even immutable targets.
196  * .map, .map_rq, .clone_and_map_rq and .release_clone_rq are all defined.
197  */
198 #define DM_TARGET_WILDCARD              0x00000008
199 #define dm_target_is_wildcard(type)     ((type)->features & DM_TARGET_WILDCARD)
200 
201 /*
202  * Some targets need to be sent the same WRITE bio severals times so
203  * that they can send copies of it to different devices.  This function
204  * examines any supplied bio and returns the number of copies of it the
205  * target requires.
206  */
207 typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio);
208 
209 struct dm_target {
210         struct dm_table *table;
211         struct target_type *type;
212 
213         /* target limits */
214         sector_t begin;
215         sector_t len;
216 
217         /* If non-zero, maximum size of I/O submitted to a target. */
218         uint32_t max_io_len;
219 
220         /*
221          * A number of zero-length barrier bios that will be submitted
222          * to the target for the purpose of flushing cache.
223          *
224          * The bio number can be accessed with dm_bio_get_target_bio_nr.
225          * It is a responsibility of the target driver to remap these bios
226          * to the real underlying devices.
227          */
228         unsigned num_flush_bios;
229 
230         /*
231          * The number of discard bios that will be submitted to the target.
232          * The bio number can be accessed with dm_bio_get_target_bio_nr.
233          */
234         unsigned num_discard_bios;
235 
236         /*
237          * The number of WRITE SAME bios that will be submitted to the target.
238          * The bio number can be accessed with dm_bio_get_target_bio_nr.
239          */
240         unsigned num_write_same_bios;
241 
242         /*
243          * The minimum number of extra bytes allocated in each io for the
244          * target to use.
245          */
246         unsigned per_io_data_size;
247 
248         /*
249          * If defined, this function is called to find out how many
250          * duplicate bios should be sent to the target when writing
251          * data.
252          */
253         dm_num_write_bios_fn num_write_bios;
254 
255         /* target specific data */
256         void *private;
257 
258         /* Used to provide an error string from the ctr */
259         char *error;
260 
261         /*
262          * Set if this target needs to receive flushes regardless of
263          * whether or not its underlying devices have support.
264          */
265         bool flush_supported:1;
266 
267         /*
268          * Set if this target needs to receive discards regardless of
269          * whether or not its underlying devices have support.
270          */
271         bool discards_supported:1;
272 
273         /*
274          * Set if the target required discard bios to be split
275          * on max_io_len boundary.
276          */
277         bool split_discard_bios:1;
278 
279         /*
280          * Set if this target does not return zeroes on discarded blocks.
281          */
282         bool discard_zeroes_data_unsupported:1;
283 };
284 
285 /* Each target can link one of these into the table */
286 struct dm_target_callbacks {
287         struct list_head list;
288         int (*congested_fn) (struct dm_target_callbacks *, int);
289 };
290 
291 /*
292  * For bio-based dm.
293  * One of these is allocated for each bio.
294  * This structure shouldn't be touched directly by target drivers.
295  * It is here so that we can inline dm_per_bio_data and
296  * dm_bio_from_per_bio_data
297  */
298 struct dm_target_io {
299         struct dm_io *io;
300         struct dm_target *ti;
301         unsigned target_bio_nr;
302         unsigned *len_ptr;
303         struct bio clone;
304 };
305 
306 static inline void *dm_per_bio_data(struct bio *bio, size_t data_size)
307 {
308         return (char *)bio - offsetof(struct dm_target_io, clone) - data_size;
309 }
310 
311 static inline struct bio *dm_bio_from_per_bio_data(void *data, size_t data_size)
312 {
313         return (struct bio *)((char *)data + data_size + offsetof(struct dm_target_io, clone));
314 }
315 
316 static inline unsigned dm_bio_get_target_bio_nr(const struct bio *bio)
317 {
318         return container_of(bio, struct dm_target_io, clone)->target_bio_nr;
319 }
320 
321 int dm_register_target(struct target_type *t);
322 void dm_unregister_target(struct target_type *t);
323 
324 /*
325  * Target argument parsing.
326  */
327 struct dm_arg_set {
328         unsigned argc;
329         char **argv;
330 };
331 
332 /*
333  * The minimum and maximum value of a numeric argument, together with
334  * the error message to use if the number is found to be outside that range.
335  */
336 struct dm_arg {
337         unsigned min;
338         unsigned max;
339         char *error;
340 };
341 
342 /*
343  * Validate the next argument, either returning it as *value or, if invalid,
344  * returning -EINVAL and setting *error.
345  */
346 int dm_read_arg(struct dm_arg *arg, struct dm_arg_set *arg_set,
347                 unsigned *value, char **error);
348 
349 /*
350  * Process the next argument as the start of a group containing between
351  * arg->min and arg->max further arguments. Either return the size as
352  * *num_args or, if invalid, return -EINVAL and set *error.
353  */
354 int dm_read_arg_group(struct dm_arg *arg, struct dm_arg_set *arg_set,
355                       unsigned *num_args, char **error);
356 
357 /*
358  * Return the current argument and shift to the next.
359  */
360 const char *dm_shift_arg(struct dm_arg_set *as);
361 
362 /*
363  * Move through num_args arguments.
364  */
365 void dm_consume_args(struct dm_arg_set *as, unsigned num_args);
366 
367 /*-----------------------------------------------------------------
368  * Functions for creating and manipulating mapped devices.
369  * Drop the reference with dm_put when you finish with the object.
370  *---------------------------------------------------------------*/
371 
372 /*
373  * DM_ANY_MINOR chooses the next available minor number.
374  */
375 #define DM_ANY_MINOR (-1)
376 int dm_create(int minor, struct mapped_device **md);
377 
378 /*
379  * Reference counting for md.
380  */
381 struct mapped_device *dm_get_md(dev_t dev);
382 void dm_get(struct mapped_device *md);
383 int dm_hold(struct mapped_device *md);
384 void dm_put(struct mapped_device *md);
385 
386 /*
387  * An arbitrary pointer may be stored alongside a mapped device.
388  */
389 void dm_set_mdptr(struct mapped_device *md, void *ptr);
390 void *dm_get_mdptr(struct mapped_device *md);
391 
392 /*
393  * A device can still be used while suspended, but I/O is deferred.
394  */
395 int dm_suspend(struct mapped_device *md, unsigned suspend_flags);
396 int dm_resume(struct mapped_device *md);
397 
398 /*
399  * Event functions.
400  */
401 uint32_t dm_get_event_nr(struct mapped_device *md);
402 int dm_wait_event(struct mapped_device *md, int event_nr);
403 uint32_t dm_next_uevent_seq(struct mapped_device *md);
404 void dm_uevent_add(struct mapped_device *md, struct list_head *elist);
405 
406 /*
407  * Info functions.
408  */
409 const char *dm_device_name(struct mapped_device *md);
410 int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid);
411 struct gendisk *dm_disk(struct mapped_device *md);
412 int dm_suspended(struct dm_target *ti);
413 int dm_noflush_suspending(struct dm_target *ti);
414 void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors);
415 union map_info *dm_get_rq_mapinfo(struct request *rq);
416 
417 struct queue_limits *dm_get_queue_limits(struct mapped_device *md);
418 
419 /*
420  * Geometry functions.
421  */
422 int dm_get_geometry(struct mapped_device *md, struct hd_geometry *geo);
423 int dm_set_geometry(struct mapped_device *md, struct hd_geometry *geo);
424 
425 /*-----------------------------------------------------------------
426  * Functions for manipulating device-mapper tables.
427  *---------------------------------------------------------------*/
428 
429 /*
430  * First create an empty table.
431  */
432 int dm_table_create(struct dm_table **result, fmode_t mode,
433                     unsigned num_targets, struct mapped_device *md);
434 
435 /*
436  * Then call this once for each target.
437  */
438 int dm_table_add_target(struct dm_table *t, const char *type,
439                         sector_t start, sector_t len, char *params);
440 
441 /*
442  * Target_ctr should call this if it needs to add any callbacks.
443  */
444 void dm_table_add_target_callbacks(struct dm_table *t, struct dm_target_callbacks *cb);
445 
446 /*
447  * Finally call this to make the table ready for use.
448  */
449 int dm_table_complete(struct dm_table *t);
450 
451 /*
452  * Target may require that it is never sent I/O larger than len.
453  */
454 int __must_check dm_set_target_max_io_len(struct dm_target *ti, sector_t len);
455 
456 /*
457  * Table reference counting.
458  */
459 struct dm_table *dm_get_live_table(struct mapped_device *md, int *srcu_idx);
460 void dm_put_live_table(struct mapped_device *md, int srcu_idx);
461 void dm_sync_table(struct mapped_device *md);
462 
463 /*
464  * Queries
465  */
466 sector_t dm_table_get_size(struct dm_table *t);
467 unsigned int dm_table_get_num_targets(struct dm_table *t);
468 fmode_t dm_table_get_mode(struct dm_table *t);
469 struct mapped_device *dm_table_get_md(struct dm_table *t);
470 
471 /*
472  * Trigger an event.
473  */
474 void dm_table_event(struct dm_table *t);
475 
476 /*
477  * Run the queue for request-based targets.
478  */
479 void dm_table_run_md_queue_async(struct dm_table *t);
480 
481 /*
482  * The device must be suspended before calling this method.
483  * Returns the previous table, which the caller must destroy.
484  */
485 struct dm_table *dm_swap_table(struct mapped_device *md,
486                                struct dm_table *t);
487 
488 /*
489  * A wrapper around vmalloc.
490  */
491 void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size);
492 
493 /*-----------------------------------------------------------------
494  * Macros.
495  *---------------------------------------------------------------*/
496 #define DM_NAME "device-mapper"
497 
498 #ifdef CONFIG_PRINTK
499 extern struct ratelimit_state dm_ratelimit_state;
500 
501 #define dm_ratelimit()  __ratelimit(&dm_ratelimit_state)
502 #else
503 #define dm_ratelimit()  0
504 #endif
505 
506 #define DMCRIT(f, arg...) \
507         printk(KERN_CRIT DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
508 
509 #define DMERR(f, arg...) \
510         printk(KERN_ERR DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
511 #define DMERR_LIMIT(f, arg...) \
512         do { \
513                 if (dm_ratelimit())     \
514                         printk(KERN_ERR DM_NAME ": " DM_MSG_PREFIX ": " \
515                                f "\n", ## arg); \
516         } while (0)
517 
518 #define DMWARN(f, arg...) \
519         printk(KERN_WARNING DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
520 #define DMWARN_LIMIT(f, arg...) \
521         do { \
522                 if (dm_ratelimit())     \
523                         printk(KERN_WARNING DM_NAME ": " DM_MSG_PREFIX ": " \
524                                f "\n", ## arg); \
525         } while (0)
526 
527 #define DMINFO(f, arg...) \
528         printk(KERN_INFO DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
529 #define DMINFO_LIMIT(f, arg...) \
530         do { \
531                 if (dm_ratelimit())     \
532                         printk(KERN_INFO DM_NAME ": " DM_MSG_PREFIX ": " f \
533                                "\n", ## arg); \
534         } while (0)
535 
536 #ifdef CONFIG_DM_DEBUG
537 #  define DMDEBUG(f, arg...) \
538         printk(KERN_DEBUG DM_NAME ": " DM_MSG_PREFIX " DEBUG: " f "\n", ## arg)
539 #  define DMDEBUG_LIMIT(f, arg...) \
540         do { \
541                 if (dm_ratelimit())     \
542                         printk(KERN_DEBUG DM_NAME ": " DM_MSG_PREFIX ": " f \
543                                "\n", ## arg); \
544         } while (0)
545 #else
546 #  define DMDEBUG(f, arg...) do {} while (0)
547 #  define DMDEBUG_LIMIT(f, arg...) do {} while (0)
548 #endif
549 
550 #define DMEMIT(x...) sz += ((sz >= maxlen) ? \
551                           0 : scnprintf(result + sz, maxlen - sz, x))
552 
553 #define SECTOR_SHIFT 9
554 
555 /*
556  * Definitions of return values from target end_io function.
557  */
558 #define DM_ENDIO_INCOMPLETE     1
559 #define DM_ENDIO_REQUEUE        2
560 
561 /*
562  * Definitions of return values from target map function.
563  */
564 #define DM_MAPIO_SUBMITTED      0
565 #define DM_MAPIO_REMAPPED       1
566 #define DM_MAPIO_REQUEUE        DM_ENDIO_REQUEUE
567 
568 #define dm_sector_div64(x, y)( \
569 { \
570         u64 _res; \
571         (x) = div64_u64_rem(x, y, &_res); \
572         _res; \
573 } \
574 )
575 
576 /*
577  * Ceiling(n / sz)
578  */
579 #define dm_div_up(n, sz) (((n) + (sz) - 1) / (sz))
580 
581 #define dm_sector_div_up(n, sz) ( \
582 { \
583         sector_t _r = ((n) + (sz) - 1); \
584         sector_div(_r, (sz)); \
585         _r; \
586 } \
587 )
588 
589 /*
590  * ceiling(n / size) * size
591  */
592 #define dm_round_up(n, sz) (dm_div_up((n), (sz)) * (sz))
593 
594 #define dm_array_too_big(fixed, obj, num) \
595         ((num) > (UINT_MAX - (fixed)) / (obj))
596 
597 /*
598  * Sector offset taken relative to the start of the target instead of
599  * relative to the start of the device.
600  */
601 #define dm_target_offset(ti, sector) ((sector) - (ti)->begin)
602 
603 static inline sector_t to_sector(unsigned long n)
604 {
605         return (n >> SECTOR_SHIFT);
606 }
607 
608 static inline unsigned long to_bytes(sector_t n)
609 {
610         return (n << SECTOR_SHIFT);
611 }
612 
613 #endif  /* _LINUX_DEVICE_MAPPER_H */
614 

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