dm-io.c revision dd0fc66fb33cd610bc1a5db8a5e232d34879b4d7
1/* 2 * Copyright (C) 2003 Sistina Software 3 * 4 * This file is released under the GPL. 5 */ 6 7#include "dm-io.h" 8 9#include <linux/bio.h> 10#include <linux/mempool.h> 11#include <linux/module.h> 12#include <linux/sched.h> 13#include <linux/slab.h> 14 15static struct bio_set *_bios; 16 17/* FIXME: can we shrink this ? */ 18struct io { 19 unsigned long error; 20 atomic_t count; 21 struct task_struct *sleeper; 22 io_notify_fn callback; 23 void *context; 24}; 25 26/* 27 * io contexts are only dynamically allocated for asynchronous 28 * io. Since async io is likely to be the majority of io we'll 29 * have the same number of io contexts as buffer heads ! (FIXME: 30 * must reduce this). 31 */ 32static unsigned _num_ios; 33static mempool_t *_io_pool; 34 35static void *alloc_io(gfp_t gfp_mask, void *pool_data) 36{ 37 return kmalloc(sizeof(struct io), gfp_mask); 38} 39 40static void free_io(void *element, void *pool_data) 41{ 42 kfree(element); 43} 44 45static unsigned int pages_to_ios(unsigned int pages) 46{ 47 return 4 * pages; /* too many ? */ 48} 49 50static int resize_pool(unsigned int new_ios) 51{ 52 int r = 0; 53 54 if (_io_pool) { 55 if (new_ios == 0) { 56 /* free off the pool */ 57 mempool_destroy(_io_pool); 58 _io_pool = NULL; 59 bioset_free(_bios); 60 61 } else { 62 /* resize the pool */ 63 r = mempool_resize(_io_pool, new_ios, GFP_KERNEL); 64 } 65 66 } else { 67 /* create new pool */ 68 _io_pool = mempool_create(new_ios, alloc_io, free_io, NULL); 69 if (!_io_pool) 70 return -ENOMEM; 71 72 _bios = bioset_create(16, 16, 4); 73 if (!_bios) { 74 mempool_destroy(_io_pool); 75 _io_pool = NULL; 76 return -ENOMEM; 77 } 78 } 79 80 if (!r) 81 _num_ios = new_ios; 82 83 return r; 84} 85 86int dm_io_get(unsigned int num_pages) 87{ 88 return resize_pool(_num_ios + pages_to_ios(num_pages)); 89} 90 91void dm_io_put(unsigned int num_pages) 92{ 93 resize_pool(_num_ios - pages_to_ios(num_pages)); 94} 95 96/*----------------------------------------------------------------- 97 * We need to keep track of which region a bio is doing io for. 98 * In order to save a memory allocation we store this the last 99 * bvec which we know is unused (blech). 100 * XXX This is ugly and can OOPS with some configs... find another way. 101 *---------------------------------------------------------------*/ 102static inline void bio_set_region(struct bio *bio, unsigned region) 103{ 104 bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region; 105} 106 107static inline unsigned bio_get_region(struct bio *bio) 108{ 109 return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len; 110} 111 112/*----------------------------------------------------------------- 113 * We need an io object to keep track of the number of bios that 114 * have been dispatched for a particular io. 115 *---------------------------------------------------------------*/ 116static void dec_count(struct io *io, unsigned int region, int error) 117{ 118 if (error) 119 set_bit(region, &io->error); 120 121 if (atomic_dec_and_test(&io->count)) { 122 if (io->sleeper) 123 wake_up_process(io->sleeper); 124 125 else { 126 int r = io->error; 127 io_notify_fn fn = io->callback; 128 void *context = io->context; 129 130 mempool_free(io, _io_pool); 131 fn(r, context); 132 } 133 } 134} 135 136static int endio(struct bio *bio, unsigned int done, int error) 137{ 138 struct io *io = (struct io *) bio->bi_private; 139 140 /* keep going until we've finished */ 141 if (bio->bi_size) 142 return 1; 143 144 if (error && bio_data_dir(bio) == READ) 145 zero_fill_bio(bio); 146 147 dec_count(io, bio_get_region(bio), error); 148 bio_put(bio); 149 150 return 0; 151} 152 153/*----------------------------------------------------------------- 154 * These little objects provide an abstraction for getting a new 155 * destination page for io. 156 *---------------------------------------------------------------*/ 157struct dpages { 158 void (*get_page)(struct dpages *dp, 159 struct page **p, unsigned long *len, unsigned *offset); 160 void (*next_page)(struct dpages *dp); 161 162 unsigned context_u; 163 void *context_ptr; 164}; 165 166/* 167 * Functions for getting the pages from a list. 168 */ 169static void list_get_page(struct dpages *dp, 170 struct page **p, unsigned long *len, unsigned *offset) 171{ 172 unsigned o = dp->context_u; 173 struct page_list *pl = (struct page_list *) dp->context_ptr; 174 175 *p = pl->page; 176 *len = PAGE_SIZE - o; 177 *offset = o; 178} 179 180static void list_next_page(struct dpages *dp) 181{ 182 struct page_list *pl = (struct page_list *) dp->context_ptr; 183 dp->context_ptr = pl->next; 184 dp->context_u = 0; 185} 186 187static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset) 188{ 189 dp->get_page = list_get_page; 190 dp->next_page = list_next_page; 191 dp->context_u = offset; 192 dp->context_ptr = pl; 193} 194 195/* 196 * Functions for getting the pages from a bvec. 197 */ 198static void bvec_get_page(struct dpages *dp, 199 struct page **p, unsigned long *len, unsigned *offset) 200{ 201 struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr; 202 *p = bvec->bv_page; 203 *len = bvec->bv_len; 204 *offset = bvec->bv_offset; 205} 206 207static void bvec_next_page(struct dpages *dp) 208{ 209 struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr; 210 dp->context_ptr = bvec + 1; 211} 212 213static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec) 214{ 215 dp->get_page = bvec_get_page; 216 dp->next_page = bvec_next_page; 217 dp->context_ptr = bvec; 218} 219 220static void vm_get_page(struct dpages *dp, 221 struct page **p, unsigned long *len, unsigned *offset) 222{ 223 *p = vmalloc_to_page(dp->context_ptr); 224 *offset = dp->context_u; 225 *len = PAGE_SIZE - dp->context_u; 226} 227 228static void vm_next_page(struct dpages *dp) 229{ 230 dp->context_ptr += PAGE_SIZE - dp->context_u; 231 dp->context_u = 0; 232} 233 234static void vm_dp_init(struct dpages *dp, void *data) 235{ 236 dp->get_page = vm_get_page; 237 dp->next_page = vm_next_page; 238 dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1); 239 dp->context_ptr = data; 240} 241 242static void dm_bio_destructor(struct bio *bio) 243{ 244 bio_free(bio, _bios); 245} 246 247/*----------------------------------------------------------------- 248 * IO routines that accept a list of pages. 249 *---------------------------------------------------------------*/ 250static void do_region(int rw, unsigned int region, struct io_region *where, 251 struct dpages *dp, struct io *io) 252{ 253 struct bio *bio; 254 struct page *page; 255 unsigned long len; 256 unsigned offset; 257 unsigned num_bvecs; 258 sector_t remaining = where->count; 259 260 while (remaining) { 261 /* 262 * Allocate a suitably sized bio, we add an extra 263 * bvec for bio_get/set_region(). 264 */ 265 num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2; 266 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios); 267 bio->bi_sector = where->sector + (where->count - remaining); 268 bio->bi_bdev = where->bdev; 269 bio->bi_end_io = endio; 270 bio->bi_private = io; 271 bio->bi_destructor = dm_bio_destructor; 272 bio_set_region(bio, region); 273 274 /* 275 * Try and add as many pages as possible. 276 */ 277 while (remaining) { 278 dp->get_page(dp, &page, &len, &offset); 279 len = min(len, to_bytes(remaining)); 280 if (!bio_add_page(bio, page, len, offset)) 281 break; 282 283 offset = 0; 284 remaining -= to_sector(len); 285 dp->next_page(dp); 286 } 287 288 atomic_inc(&io->count); 289 submit_bio(rw, bio); 290 } 291} 292 293static void dispatch_io(int rw, unsigned int num_regions, 294 struct io_region *where, struct dpages *dp, 295 struct io *io, int sync) 296{ 297 int i; 298 struct dpages old_pages = *dp; 299 300 if (sync) 301 rw |= (1 << BIO_RW_SYNC); 302 303 /* 304 * For multiple regions we need to be careful to rewind 305 * the dp object for each call to do_region. 306 */ 307 for (i = 0; i < num_regions; i++) { 308 *dp = old_pages; 309 if (where[i].count) 310 do_region(rw, i, where + i, dp, io); 311 } 312 313 /* 314 * Drop the extra refence that we were holding to avoid 315 * the io being completed too early. 316 */ 317 dec_count(io, 0, 0); 318} 319 320static int sync_io(unsigned int num_regions, struct io_region *where, 321 int rw, struct dpages *dp, unsigned long *error_bits) 322{ 323 struct io io; 324 325 if (num_regions > 1 && rw != WRITE) { 326 WARN_ON(1); 327 return -EIO; 328 } 329 330 io.error = 0; 331 atomic_set(&io.count, 1); /* see dispatch_io() */ 332 io.sleeper = current; 333 334 dispatch_io(rw, num_regions, where, dp, &io, 1); 335 336 while (1) { 337 set_current_state(TASK_UNINTERRUPTIBLE); 338 339 if (!atomic_read(&io.count) || signal_pending(current)) 340 break; 341 342 io_schedule(); 343 } 344 set_current_state(TASK_RUNNING); 345 346 if (atomic_read(&io.count)) 347 return -EINTR; 348 349 *error_bits = io.error; 350 return io.error ? -EIO : 0; 351} 352 353static int async_io(unsigned int num_regions, struct io_region *where, int rw, 354 struct dpages *dp, io_notify_fn fn, void *context) 355{ 356 struct io *io; 357 358 if (num_regions > 1 && rw != WRITE) { 359 WARN_ON(1); 360 fn(1, context); 361 return -EIO; 362 } 363 364 io = mempool_alloc(_io_pool, GFP_NOIO); 365 io->error = 0; 366 atomic_set(&io->count, 1); /* see dispatch_io() */ 367 io->sleeper = NULL; 368 io->callback = fn; 369 io->context = context; 370 371 dispatch_io(rw, num_regions, where, dp, io, 0); 372 return 0; 373} 374 375int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw, 376 struct page_list *pl, unsigned int offset, 377 unsigned long *error_bits) 378{ 379 struct dpages dp; 380 list_dp_init(&dp, pl, offset); 381 return sync_io(num_regions, where, rw, &dp, error_bits); 382} 383 384int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw, 385 struct bio_vec *bvec, unsigned long *error_bits) 386{ 387 struct dpages dp; 388 bvec_dp_init(&dp, bvec); 389 return sync_io(num_regions, where, rw, &dp, error_bits); 390} 391 392int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw, 393 void *data, unsigned long *error_bits) 394{ 395 struct dpages dp; 396 vm_dp_init(&dp, data); 397 return sync_io(num_regions, where, rw, &dp, error_bits); 398} 399 400int dm_io_async(unsigned int num_regions, struct io_region *where, int rw, 401 struct page_list *pl, unsigned int offset, 402 io_notify_fn fn, void *context) 403{ 404 struct dpages dp; 405 list_dp_init(&dp, pl, offset); 406 return async_io(num_regions, where, rw, &dp, fn, context); 407} 408 409int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw, 410 struct bio_vec *bvec, io_notify_fn fn, void *context) 411{ 412 struct dpages dp; 413 bvec_dp_init(&dp, bvec); 414 return async_io(num_regions, where, rw, &dp, fn, context); 415} 416 417int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw, 418 void *data, io_notify_fn fn, void *context) 419{ 420 struct dpages dp; 421 vm_dp_init(&dp, data); 422 return async_io(num_regions, where, rw, &dp, fn, context); 423} 424 425EXPORT_SYMBOL(dm_io_get); 426EXPORT_SYMBOL(dm_io_put); 427EXPORT_SYMBOL(dm_io_sync); 428EXPORT_SYMBOL(dm_io_async); 429EXPORT_SYMBOL(dm_io_sync_bvec); 430EXPORT_SYMBOL(dm_io_async_bvec); 431EXPORT_SYMBOL(dm_io_sync_vm); 432EXPORT_SYMBOL(dm_io_async_vm); 433