1 /* 2 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com> 3 * 4 * Scatterlist handling helpers. 5 * 6 * This source code is licensed under the GNU General Public License, 7 * Version 2. See the file COPYING for more details. 8 */ 9 #include <linux/export.h> 10 #include <linux/slab.h> 11 #include <linux/scatterlist.h> 12 #include <linux/highmem.h> 13 #include <linux/kmemleak.h> 14 15 /** 16 * sg_next - return the next scatterlist entry in a list 17 * @sg: The current sg entry 18 * 19 * Description: 20 * Usually the next entry will be @sg@ + 1, but if this sg element is part 21 * of a chained scatterlist, it could jump to the start of a new 22 * scatterlist array. 23 * 24 **/ 25 struct scatterlist *sg_next(struct scatterlist *sg) 26 { 27 #ifdef CONFIG_DEBUG_SG 28 BUG_ON(sg->sg_magic != SG_MAGIC); 29 #endif 30 if (sg_is_last(sg)) 31 return NULL; 32 33 sg++; 34 if (unlikely(sg_is_chain(sg))) 35 sg = sg_chain_ptr(sg); 36 37 return sg; 38 } 39 EXPORT_SYMBOL(sg_next); 40 41 /** 42 * sg_nents - return total count of entries in scatterlist 43 * @sg: The scatterlist 44 * 45 * Description: 46 * Allows to know how many entries are in sg, taking into acount 47 * chaining as well 48 * 49 **/ 50 int sg_nents(struct scatterlist *sg) 51 { 52 int nents; 53 for (nents = 0; sg; sg = sg_next(sg)) 54 nents++; 55 return nents; 56 } 57 EXPORT_SYMBOL(sg_nents); 58 59 60 /** 61 * sg_last - return the last scatterlist entry in a list 62 * @sgl: First entry in the scatterlist 63 * @nents: Number of entries in the scatterlist 64 * 65 * Description: 66 * Should only be used casually, it (currently) scans the entire list 67 * to get the last entry. 68 * 69 * Note that the @sgl@ pointer passed in need not be the first one, 70 * the important bit is that @nents@ denotes the number of entries that 71 * exist from @sgl@. 72 * 73 **/ 74 struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) 75 { 76 #ifndef ARCH_HAS_SG_CHAIN 77 struct scatterlist *ret = &sgl[nents - 1]; 78 #else 79 struct scatterlist *sg, *ret = NULL; 80 unsigned int i; 81 82 for_each_sg(sgl, sg, nents, i) 83 ret = sg; 84 85 #endif 86 #ifdef CONFIG_DEBUG_SG 87 BUG_ON(sgl[0].sg_magic != SG_MAGIC); 88 BUG_ON(!sg_is_last(ret)); 89 #endif 90 return ret; 91 } 92 EXPORT_SYMBOL(sg_last); 93 94 /** 95 * sg_init_table - Initialize SG table 96 * @sgl: The SG table 97 * @nents: Number of entries in table 98 * 99 * Notes: 100 * If this is part of a chained sg table, sg_mark_end() should be 101 * used only on the last table part. 102 * 103 **/ 104 void sg_init_table(struct scatterlist *sgl, unsigned int nents) 105 { 106 memset(sgl, 0, sizeof(*sgl) * nents); 107 #ifdef CONFIG_DEBUG_SG 108 { 109 unsigned int i; 110 for (i = 0; i < nents; i++) 111 sgl[i].sg_magic = SG_MAGIC; 112 } 113 #endif 114 sg_mark_end(&sgl[nents - 1]); 115 } 116 EXPORT_SYMBOL(sg_init_table); 117 118 /** 119 * sg_init_one - Initialize a single entry sg list 120 * @sg: SG entry 121 * @buf: Virtual address for IO 122 * @buflen: IO length 123 * 124 **/ 125 void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) 126 { 127 sg_init_table(sg, 1); 128 sg_set_buf(sg, buf, buflen); 129 } 130 EXPORT_SYMBOL(sg_init_one); 131 132 /* 133 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree 134 * helpers. 135 */ 136 static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) 137 { 138 if (nents == SG_MAX_SINGLE_ALLOC) { 139 /* 140 * Kmemleak doesn't track page allocations as they are not 141 * commonly used (in a raw form) for kernel data structures. 142 * As we chain together a list of pages and then a normal 143 * kmalloc (tracked by kmemleak), in order to for that last 144 * allocation not to become decoupled (and thus a 145 * false-positive) we need to inform kmemleak of all the 146 * intermediate allocations. 147 */ 148 void *ptr = (void *) __get_free_page(gfp_mask); 149 kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); 150 return ptr; 151 } else 152 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); 153 } 154 155 static void sg_kfree(struct scatterlist *sg, unsigned int nents) 156 { 157 if (nents == SG_MAX_SINGLE_ALLOC) { 158 kmemleak_free(sg); 159 free_page((unsigned long) sg); 160 } else 161 kfree(sg); 162 } 163 164 /** 165 * __sg_free_table - Free a previously mapped sg table 166 * @table: The sg table header to use 167 * @max_ents: The maximum number of entries per single scatterlist 168 * @free_fn: Free function 169 * 170 * Description: 171 * Free an sg table previously allocated and setup with 172 * __sg_alloc_table(). The @max_ents value must be identical to 173 * that previously used with __sg_alloc_table(). 174 * 175 **/ 176 void __sg_free_table(struct sg_table *table, unsigned int max_ents, 177 sg_free_fn *free_fn) 178 { 179 struct scatterlist *sgl, *next; 180 181 if (unlikely(!table->sgl)) 182 return; 183 184 sgl = table->sgl; 185 while (table->orig_nents) { 186 unsigned int alloc_size = table->orig_nents; 187 unsigned int sg_size; 188 189 /* 190 * If we have more than max_ents segments left, 191 * then assign 'next' to the sg table after the current one. 192 * sg_size is then one less than alloc size, since the last 193 * element is the chain pointer. 194 */ 195 if (alloc_size > max_ents) { 196 next = sg_chain_ptr(&sgl[max_ents - 1]); 197 alloc_size = max_ents; 198 sg_size = alloc_size - 1; 199 } else { 200 sg_size = alloc_size; 201 next = NULL; 202 } 203 204 table->orig_nents -= sg_size; 205 free_fn(sgl, alloc_size); 206 sgl = next; 207 } 208 209 table->sgl = NULL; 210 } 211 EXPORT_SYMBOL(__sg_free_table); 212 213 /** 214 * sg_free_table - Free a previously allocated sg table 215 * @table: The mapped sg table header 216 * 217 **/ 218 void sg_free_table(struct sg_table *table) 219 { 220 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); 221 } 222 EXPORT_SYMBOL(sg_free_table); 223 224 /** 225 * __sg_alloc_table - Allocate and initialize an sg table with given allocator 226 * @table: The sg table header to use 227 * @nents: Number of entries in sg list 228 * @max_ents: The maximum number of entries the allocator returns per call 229 * @gfp_mask: GFP allocation mask 230 * @alloc_fn: Allocator to use 231 * 232 * Description: 233 * This function returns a @table @nents long. The allocator is 234 * defined to return scatterlist chunks of maximum size @max_ents. 235 * Thus if @nents is bigger than @max_ents, the scatterlists will be 236 * chained in units of @max_ents. 237 * 238 * Notes: 239 * If this function returns non-0 (eg failure), the caller must call 240 * __sg_free_table() to cleanup any leftover allocations. 241 * 242 **/ 243 int __sg_alloc_table(struct sg_table *table, unsigned int nents, 244 unsigned int max_ents, gfp_t gfp_mask, 245 sg_alloc_fn *alloc_fn) 246 { 247 struct scatterlist *sg, *prv; 248 unsigned int left; 249 250 #ifndef ARCH_HAS_SG_CHAIN 251 if (WARN_ON_ONCE(nents > max_ents)) 252 return -EINVAL; 253 #endif 254 255 memset(table, 0, sizeof(*table)); 256 257 left = nents; 258 prv = NULL; 259 do { 260 unsigned int sg_size, alloc_size = left; 261 262 if (alloc_size > max_ents) { 263 alloc_size = max_ents; 264 sg_size = alloc_size - 1; 265 } else 266 sg_size = alloc_size; 267 268 left -= sg_size; 269 270 sg = alloc_fn(alloc_size, gfp_mask); 271 if (unlikely(!sg)) { 272 /* 273 * Adjust entry count to reflect that the last 274 * entry of the previous table won't be used for 275 * linkage. Without this, sg_kfree() may get 276 * confused. 277 */ 278 if (prv) 279 table->nents = ++table->orig_nents; 280 281 return -ENOMEM; 282 } 283 284 sg_init_table(sg, alloc_size); 285 table->nents = table->orig_nents += sg_size; 286 287 /* 288 * If this is the first mapping, assign the sg table header. 289 * If this is not the first mapping, chain previous part. 290 */ 291 if (prv) 292 sg_chain(prv, max_ents, sg); 293 else 294 table->sgl = sg; 295 296 /* 297 * If no more entries after this one, mark the end 298 */ 299 if (!left) 300 sg_mark_end(&sg[sg_size - 1]); 301 302 prv = sg; 303 } while (left); 304 305 return 0; 306 } 307 EXPORT_SYMBOL(__sg_alloc_table); 308 309 /** 310 * sg_alloc_table - Allocate and initialize an sg table 311 * @table: The sg table header to use 312 * @nents: Number of entries in sg list 313 * @gfp_mask: GFP allocation mask 314 * 315 * Description: 316 * Allocate and initialize an sg table. If @nents@ is larger than 317 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. 318 * 319 **/ 320 int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) 321 { 322 int ret; 323 324 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, 325 gfp_mask, sg_kmalloc); 326 if (unlikely(ret)) 327 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); 328 329 return ret; 330 } 331 EXPORT_SYMBOL(sg_alloc_table); 332 333 /** 334 * sg_alloc_table_from_pages - Allocate and initialize an sg table from 335 * an array of pages 336 * @sgt: The sg table header to use 337 * @pages: Pointer to an array of page pointers 338 * @n_pages: Number of pages in the pages array 339 * @offset: Offset from start of the first page to the start of a buffer 340 * @size: Number of valid bytes in the buffer (after offset) 341 * @gfp_mask: GFP allocation mask 342 * 343 * Description: 344 * Allocate and initialize an sg table from a list of pages. Contiguous 345 * ranges of the pages are squashed into a single scatterlist node. A user 346 * may provide an offset at a start and a size of valid data in a buffer 347 * specified by the page array. The returned sg table is released by 348 * sg_free_table. 349 * 350 * Returns: 351 * 0 on success, negative error on failure 352 */ 353 int sg_alloc_table_from_pages(struct sg_table *sgt, 354 struct page **pages, unsigned int n_pages, 355 unsigned long offset, unsigned long size, 356 gfp_t gfp_mask) 357 { 358 unsigned int chunks; 359 unsigned int i; 360 unsigned int cur_page; 361 int ret; 362 struct scatterlist *s; 363 364 /* compute number of contiguous chunks */ 365 chunks = 1; 366 for (i = 1; i < n_pages; ++i) 367 if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) 368 ++chunks; 369 370 ret = sg_alloc_table(sgt, chunks, gfp_mask); 371 if (unlikely(ret)) 372 return ret; 373 374 /* merging chunks and putting them into the scatterlist */ 375 cur_page = 0; 376 for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { 377 unsigned long chunk_size; 378 unsigned int j; 379 380 /* look for the end of the current chunk */ 381 for (j = cur_page + 1; j < n_pages; ++j) 382 if (page_to_pfn(pages[j]) != 383 page_to_pfn(pages[j - 1]) + 1) 384 break; 385 386 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; 387 sg_set_page(s, pages[cur_page], min(size, chunk_size), offset); 388 size -= chunk_size; 389 offset = 0; 390 cur_page = j; 391 } 392 393 return 0; 394 } 395 EXPORT_SYMBOL(sg_alloc_table_from_pages); 396 397 void __sg_page_iter_start(struct sg_page_iter *piter, 398 struct scatterlist *sglist, unsigned int nents, 399 unsigned long pgoffset) 400 { 401 piter->__pg_advance = 0; 402 piter->__nents = nents; 403 404 piter->sg = sglist; 405 piter->sg_pgoffset = pgoffset; 406 } 407 EXPORT_SYMBOL(__sg_page_iter_start); 408 409 static int sg_page_count(struct scatterlist *sg) 410 { 411 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; 412 } 413 414 bool __sg_page_iter_next(struct sg_page_iter *piter) 415 { 416 if (!piter->__nents || !piter->sg) 417 return false; 418 419 piter->sg_pgoffset += piter->__pg_advance; 420 piter->__pg_advance = 1; 421 422 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { 423 piter->sg_pgoffset -= sg_page_count(piter->sg); 424 piter->sg = sg_next(piter->sg); 425 if (!--piter->__nents || !piter->sg) 426 return false; 427 } 428 429 return true; 430 } 431 EXPORT_SYMBOL(__sg_page_iter_next); 432 433 /** 434 * sg_miter_start - start mapping iteration over a sg list 435 * @miter: sg mapping iter to be started 436 * @sgl: sg list to iterate over 437 * @nents: number of sg entries 438 * 439 * Description: 440 * Starts mapping iterator @miter. 441 * 442 * Context: 443 * Don't care. 444 */ 445 void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 446 unsigned int nents, unsigned int flags) 447 { 448 memset(miter, 0, sizeof(struct sg_mapping_iter)); 449 450 __sg_page_iter_start(&miter->piter, sgl, nents, 0); 451 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 452 miter->__flags = flags; 453 } 454 EXPORT_SYMBOL(sg_miter_start); 455 456 /** 457 * sg_miter_next - proceed mapping iterator to the next mapping 458 * @miter: sg mapping iter to proceed 459 * 460 * Description: 461 * Proceeds @miter to the next mapping. @miter should have been started 462 * using sg_miter_start(). On successful return, @miter->page, 463 * @miter->addr and @miter->length point to the current mapping. 464 * 465 * Context: 466 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled 467 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC. 468 * 469 * Returns: 470 * true if @miter contains the next mapping. false if end of sg 471 * list is reached. 472 */ 473 bool sg_miter_next(struct sg_mapping_iter *miter) 474 { 475 sg_miter_stop(miter); 476 477 /* 478 * Get to the next page if necessary. 479 * __remaining, __offset is adjusted by sg_miter_stop 480 */ 481 if (!miter->__remaining) { 482 struct scatterlist *sg; 483 unsigned long pgoffset; 484 485 if (!__sg_page_iter_next(&miter->piter)) 486 return false; 487 488 sg = miter->piter.sg; 489 pgoffset = miter->piter.sg_pgoffset; 490 491 miter->__offset = pgoffset ? 0 : sg->offset; 492 miter->__remaining = sg->offset + sg->length - 493 (pgoffset << PAGE_SHIFT) - miter->__offset; 494 miter->__remaining = min_t(unsigned long, miter->__remaining, 495 PAGE_SIZE - miter->__offset); 496 } 497 miter->page = sg_page_iter_page(&miter->piter); 498 miter->consumed = miter->length = miter->__remaining; 499 500 if (miter->__flags & SG_MITER_ATOMIC) 501 miter->addr = kmap_atomic(miter->page) + miter->__offset; 502 else 503 miter->addr = kmap(miter->page) + miter->__offset; 504 505 return true; 506 } 507 EXPORT_SYMBOL(sg_miter_next); 508 509 /** 510 * sg_miter_stop - stop mapping iteration 511 * @miter: sg mapping iter to be stopped 512 * 513 * Description: 514 * Stops mapping iterator @miter. @miter should have been started 515 * started using sg_miter_start(). A stopped iteration can be 516 * resumed by calling sg_miter_next() on it. This is useful when 517 * resources (kmap) need to be released during iteration. 518 * 519 * Context: 520 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care 521 * otherwise. 522 */ 523 void sg_miter_stop(struct sg_mapping_iter *miter) 524 { 525 WARN_ON(miter->consumed > miter->length); 526 527 /* drop resources from the last iteration */ 528 if (miter->addr) { 529 miter->__offset += miter->consumed; 530 miter->__remaining -= miter->consumed; 531 532 if (miter->__flags & SG_MITER_TO_SG) 533 flush_kernel_dcache_page(miter->page); 534 535 if (miter->__flags & SG_MITER_ATOMIC) { 536 WARN_ON_ONCE(preemptible()); 537 kunmap_atomic(miter->addr); 538 } else 539 kunmap(miter->page); 540 541 miter->page = NULL; 542 miter->addr = NULL; 543 miter->length = 0; 544 miter->consumed = 0; 545 } 546 } 547 EXPORT_SYMBOL(sg_miter_stop); 548 549 /** 550 * sg_copy_buffer - Copy data between a linear buffer and an SG list 551 * @sgl: The SG list 552 * @nents: Number of SG entries 553 * @buf: Where to copy from 554 * @buflen: The number of bytes to copy 555 * @to_buffer: transfer direction (non zero == from an sg list to a 556 * buffer, 0 == from a buffer to an sg list 557 * 558 * Returns the number of copied bytes. 559 * 560 **/ 561 static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, 562 void *buf, size_t buflen, int to_buffer) 563 { 564 unsigned int offset = 0; 565 struct sg_mapping_iter miter; 566 unsigned long flags; 567 unsigned int sg_flags = SG_MITER_ATOMIC; 568 569 if (to_buffer) 570 sg_flags |= SG_MITER_FROM_SG; 571 else 572 sg_flags |= SG_MITER_TO_SG; 573 574 sg_miter_start(&miter, sgl, nents, sg_flags); 575 576 local_irq_save(flags); 577 578 while (sg_miter_next(&miter) && offset < buflen) { 579 unsigned int len; 580 581 len = min(miter.length, buflen - offset); 582 583 if (to_buffer) 584 memcpy(buf + offset, miter.addr, len); 585 else 586 memcpy(miter.addr, buf + offset, len); 587 588 offset += len; 589 } 590 591 sg_miter_stop(&miter); 592 593 local_irq_restore(flags); 594 return offset; 595 } 596 597 /** 598 * sg_copy_from_buffer - Copy from a linear buffer to an SG list 599 * @sgl: The SG list 600 * @nents: Number of SG entries 601 * @buf: Where to copy from 602 * @buflen: The number of bytes to copy 603 * 604 * Returns the number of copied bytes. 605 * 606 **/ 607 size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 608 void *buf, size_t buflen) 609 { 610 return sg_copy_buffer(sgl, nents, buf, buflen, 0); 611 } 612 EXPORT_SYMBOL(sg_copy_from_buffer); 613 614 /** 615 * sg_copy_to_buffer - Copy from an SG list to a linear buffer 616 * @sgl: The SG list 617 * @nents: Number of SG entries 618 * @buf: Where to copy to 619 * @buflen: The number of bytes to copy 620 * 621 * Returns the number of copied bytes. 622 * 623 **/ 624 size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 625 void *buf, size_t buflen) 626 { 627 return sg_copy_buffer(sgl, nents, buf, buflen, 1); 628 } 629 EXPORT_SYMBOL(sg_copy_to_buffer); 630