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/module.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 **/ 25struct 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} 39EXPORT_SYMBOL(sg_next); 40 41/** 42 * sg_last - return the last scatterlist entry in a list 43 * @sgl: First entry in the scatterlist 44 * @nents: Number of entries in the scatterlist 45 * 46 * Description: 47 * Should only be used casually, it (currently) scans the entire list 48 * to get the last entry. 49 * 50 * Note that the @sgl@ pointer passed in need not be the first one, 51 * the important bit is that @nents@ denotes the number of entries that 52 * exist from @sgl@. 53 * 54 **/ 55struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) 56{ 57#ifndef ARCH_HAS_SG_CHAIN 58 struct scatterlist *ret = &sgl[nents - 1]; 59#else 60 struct scatterlist *sg, *ret = NULL; 61 unsigned int i; 62 63 for_each_sg(sgl, sg, nents, i) 64 ret = sg; 65 66#endif 67#ifdef CONFIG_DEBUG_SG 68 BUG_ON(sgl[0].sg_magic != SG_MAGIC); 69 BUG_ON(!sg_is_last(ret)); 70#endif 71 return ret; 72} 73EXPORT_SYMBOL(sg_last); 74 75/** 76 * sg_init_table - Initialize SG table 77 * @sgl: The SG table 78 * @nents: Number of entries in table 79 * 80 * Notes: 81 * If this is part of a chained sg table, sg_mark_end() should be 82 * used only on the last table part. 83 * 84 **/ 85void sg_init_table(struct scatterlist *sgl, unsigned int nents) 86{ 87 memset(sgl, 0, sizeof(*sgl) * nents); 88#ifdef CONFIG_DEBUG_SG 89 { 90 unsigned int i; 91 for (i = 0; i < nents; i++) 92 sgl[i].sg_magic = SG_MAGIC; 93 } 94#endif 95 sg_mark_end(&sgl[nents - 1]); 96} 97EXPORT_SYMBOL(sg_init_table); 98 99/** 100 * sg_init_one - Initialize a single entry sg list 101 * @sg: SG entry 102 * @buf: Virtual address for IO 103 * @buflen: IO length 104 * 105 **/ 106void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) 107{ 108 sg_init_table(sg, 1); 109 sg_set_buf(sg, buf, buflen); 110} 111EXPORT_SYMBOL(sg_init_one); 112 113/* 114 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree 115 * helpers. 116 */ 117static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) 118{ 119 if (nents == SG_MAX_SINGLE_ALLOC) { 120 /* 121 * Kmemleak doesn't track page allocations as they are not 122 * commonly used (in a raw form) for kernel data structures. 123 * As we chain together a list of pages and then a normal 124 * kmalloc (tracked by kmemleak), in order to for that last 125 * allocation not to become decoupled (and thus a 126 * false-positive) we need to inform kmemleak of all the 127 * intermediate allocations. 128 */ 129 void *ptr = (void *) __get_free_page(gfp_mask); 130 kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); 131 return ptr; 132 } else 133 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); 134} 135 136static void sg_kfree(struct scatterlist *sg, unsigned int nents) 137{ 138 if (nents == SG_MAX_SINGLE_ALLOC) { 139 kmemleak_free(sg); 140 free_page((unsigned long) sg); 141 } else 142 kfree(sg); 143} 144 145/** 146 * __sg_free_table - Free a previously mapped sg table 147 * @table: The sg table header to use 148 * @max_ents: The maximum number of entries per single scatterlist 149 * @free_fn: Free function 150 * 151 * Description: 152 * Free an sg table previously allocated and setup with 153 * __sg_alloc_table(). The @max_ents value must be identical to 154 * that previously used with __sg_alloc_table(). 155 * 156 **/ 157void __sg_free_table(struct sg_table *table, unsigned int max_ents, 158 sg_free_fn *free_fn) 159{ 160 struct scatterlist *sgl, *next; 161 162 if (unlikely(!table->sgl)) 163 return; 164 165 sgl = table->sgl; 166 while (table->orig_nents) { 167 unsigned int alloc_size = table->orig_nents; 168 unsigned int sg_size; 169 170 /* 171 * If we have more than max_ents segments left, 172 * then assign 'next' to the sg table after the current one. 173 * sg_size is then one less than alloc size, since the last 174 * element is the chain pointer. 175 */ 176 if (alloc_size > max_ents) { 177 next = sg_chain_ptr(&sgl[max_ents - 1]); 178 alloc_size = max_ents; 179 sg_size = alloc_size - 1; 180 } else { 181 sg_size = alloc_size; 182 next = NULL; 183 } 184 185 table->orig_nents -= sg_size; 186 free_fn(sgl, alloc_size); 187 sgl = next; 188 } 189 190 table->sgl = NULL; 191} 192EXPORT_SYMBOL(__sg_free_table); 193 194/** 195 * sg_free_table - Free a previously allocated sg table 196 * @table: The mapped sg table header 197 * 198 **/ 199void sg_free_table(struct sg_table *table) 200{ 201 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); 202} 203EXPORT_SYMBOL(sg_free_table); 204 205/** 206 * __sg_alloc_table - Allocate and initialize an sg table with given allocator 207 * @table: The sg table header to use 208 * @nents: Number of entries in sg list 209 * @max_ents: The maximum number of entries the allocator returns per call 210 * @gfp_mask: GFP allocation mask 211 * @alloc_fn: Allocator to use 212 * 213 * Description: 214 * This function returns a @table @nents long. The allocator is 215 * defined to return scatterlist chunks of maximum size @max_ents. 216 * Thus if @nents is bigger than @max_ents, the scatterlists will be 217 * chained in units of @max_ents. 218 * 219 * Notes: 220 * If this function returns non-0 (eg failure), the caller must call 221 * __sg_free_table() to cleanup any leftover allocations. 222 * 223 **/ 224int __sg_alloc_table(struct sg_table *table, unsigned int nents, 225 unsigned int max_ents, gfp_t gfp_mask, 226 sg_alloc_fn *alloc_fn) 227{ 228 struct scatterlist *sg, *prv; 229 unsigned int left; 230 231#ifndef ARCH_HAS_SG_CHAIN 232 BUG_ON(nents > max_ents); 233#endif 234 235 memset(table, 0, sizeof(*table)); 236 237 left = nents; 238 prv = NULL; 239 do { 240 unsigned int sg_size, alloc_size = left; 241 242 if (alloc_size > max_ents) { 243 alloc_size = max_ents; 244 sg_size = alloc_size - 1; 245 } else 246 sg_size = alloc_size; 247 248 left -= sg_size; 249 250 sg = alloc_fn(alloc_size, gfp_mask); 251 if (unlikely(!sg)) { 252 /* 253 * Adjust entry count to reflect that the last 254 * entry of the previous table won't be used for 255 * linkage. Without this, sg_kfree() may get 256 * confused. 257 */ 258 if (prv) 259 table->nents = ++table->orig_nents; 260 261 return -ENOMEM; 262 } 263 264 sg_init_table(sg, alloc_size); 265 table->nents = table->orig_nents += sg_size; 266 267 /* 268 * If this is the first mapping, assign the sg table header. 269 * If this is not the first mapping, chain previous part. 270 */ 271 if (prv) 272 sg_chain(prv, max_ents, sg); 273 else 274 table->sgl = sg; 275 276 /* 277 * If no more entries after this one, mark the end 278 */ 279 if (!left) 280 sg_mark_end(&sg[sg_size - 1]); 281 282 /* 283 * only really needed for mempool backed sg allocations (like 284 * SCSI), a possible improvement here would be to pass the 285 * table pointer into the allocator and let that clear these 286 * flags 287 */ 288 gfp_mask &= ~__GFP_WAIT; 289 gfp_mask |= __GFP_HIGH; 290 prv = sg; 291 } while (left); 292 293 return 0; 294} 295EXPORT_SYMBOL(__sg_alloc_table); 296 297/** 298 * sg_alloc_table - Allocate and initialize an sg table 299 * @table: The sg table header to use 300 * @nents: Number of entries in sg list 301 * @gfp_mask: GFP allocation mask 302 * 303 * Description: 304 * Allocate and initialize an sg table. If @nents@ is larger than 305 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. 306 * 307 **/ 308int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) 309{ 310 int ret; 311 312 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, 313 gfp_mask, sg_kmalloc); 314 if (unlikely(ret)) 315 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); 316 317 return ret; 318} 319EXPORT_SYMBOL(sg_alloc_table); 320 321/** 322 * sg_miter_start - start mapping iteration over a sg list 323 * @miter: sg mapping iter to be started 324 * @sgl: sg list to iterate over 325 * @nents: number of sg entries 326 * 327 * Description: 328 * Starts mapping iterator @miter. 329 * 330 * Context: 331 * Don't care. 332 */ 333void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 334 unsigned int nents, unsigned int flags) 335{ 336 memset(miter, 0, sizeof(struct sg_mapping_iter)); 337 338 miter->__sg = sgl; 339 miter->__nents = nents; 340 miter->__offset = 0; 341 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 342 miter->__flags = flags; 343} 344EXPORT_SYMBOL(sg_miter_start); 345 346/** 347 * sg_miter_next - proceed mapping iterator to the next mapping 348 * @miter: sg mapping iter to proceed 349 * 350 * Description: 351 * Proceeds @miter@ to the next mapping. @miter@ should have been 352 * started using sg_miter_start(). On successful return, 353 * @miter@->page, @miter@->addr and @miter@->length point to the 354 * current mapping. 355 * 356 * Context: 357 * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till 358 * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC. 359 * 360 * Returns: 361 * true if @miter contains the next mapping. false if end of sg 362 * list is reached. 363 */ 364bool sg_miter_next(struct sg_mapping_iter *miter) 365{ 366 unsigned int off, len; 367 368 /* check for end and drop resources from the last iteration */ 369 if (!miter->__nents) 370 return false; 371 372 sg_miter_stop(miter); 373 374 /* get to the next sg if necessary. __offset is adjusted by stop */ 375 while (miter->__offset == miter->__sg->length) { 376 if (--miter->__nents) { 377 miter->__sg = sg_next(miter->__sg); 378 miter->__offset = 0; 379 } else 380 return false; 381 } 382 383 /* map the next page */ 384 off = miter->__sg->offset + miter->__offset; 385 len = miter->__sg->length - miter->__offset; 386 387 miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT); 388 off &= ~PAGE_MASK; 389 miter->length = min_t(unsigned int, len, PAGE_SIZE - off); 390 miter->consumed = miter->length; 391 392 if (miter->__flags & SG_MITER_ATOMIC) 393 miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off; 394 else 395 miter->addr = kmap(miter->page) + off; 396 397 return true; 398} 399EXPORT_SYMBOL(sg_miter_next); 400 401/** 402 * sg_miter_stop - stop mapping iteration 403 * @miter: sg mapping iter to be stopped 404 * 405 * Description: 406 * Stops mapping iterator @miter. @miter should have been started 407 * started using sg_miter_start(). A stopped iteration can be 408 * resumed by calling sg_miter_next() on it. This is useful when 409 * resources (kmap) need to be released during iteration. 410 * 411 * Context: 412 * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise. 413 */ 414void sg_miter_stop(struct sg_mapping_iter *miter) 415{ 416 WARN_ON(miter->consumed > miter->length); 417 418 /* drop resources from the last iteration */ 419 if (miter->addr) { 420 miter->__offset += miter->consumed; 421 422 if (miter->__flags & SG_MITER_TO_SG) 423 flush_kernel_dcache_page(miter->page); 424 425 if (miter->__flags & SG_MITER_ATOMIC) { 426 WARN_ON(!irqs_disabled()); 427 kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ); 428 } else 429 kunmap(miter->page); 430 431 miter->page = NULL; 432 miter->addr = NULL; 433 miter->length = 0; 434 miter->consumed = 0; 435 } 436} 437EXPORT_SYMBOL(sg_miter_stop); 438 439/** 440 * sg_copy_buffer - Copy data between a linear buffer and an SG list 441 * @sgl: The SG list 442 * @nents: Number of SG entries 443 * @buf: Where to copy from 444 * @buflen: The number of bytes to copy 445 * @to_buffer: transfer direction (non zero == from an sg list to a 446 * buffer, 0 == from a buffer to an sg list 447 * 448 * Returns the number of copied bytes. 449 * 450 **/ 451static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, 452 void *buf, size_t buflen, int to_buffer) 453{ 454 unsigned int offset = 0; 455 struct sg_mapping_iter miter; 456 unsigned long flags; 457 unsigned int sg_flags = SG_MITER_ATOMIC; 458 459 if (to_buffer) 460 sg_flags |= SG_MITER_FROM_SG; 461 else 462 sg_flags |= SG_MITER_TO_SG; 463 464 sg_miter_start(&miter, sgl, nents, sg_flags); 465 466 local_irq_save(flags); 467 468 while (sg_miter_next(&miter) && offset < buflen) { 469 unsigned int len; 470 471 len = min(miter.length, buflen - offset); 472 473 if (to_buffer) 474 memcpy(buf + offset, miter.addr, len); 475 else 476 memcpy(miter.addr, buf + offset, len); 477 478 offset += len; 479 } 480 481 sg_miter_stop(&miter); 482 483 local_irq_restore(flags); 484 return offset; 485} 486 487/** 488 * sg_copy_from_buffer - Copy from a linear buffer to an SG list 489 * @sgl: The SG list 490 * @nents: Number of SG entries 491 * @buf: Where to copy from 492 * @buflen: The number of bytes to copy 493 * 494 * Returns the number of copied bytes. 495 * 496 **/ 497size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 498 void *buf, size_t buflen) 499{ 500 return sg_copy_buffer(sgl, nents, buf, buflen, 0); 501} 502EXPORT_SYMBOL(sg_copy_from_buffer); 503 504/** 505 * sg_copy_to_buffer - Copy from an SG list to a linear buffer 506 * @sgl: The SG list 507 * @nents: Number of SG entries 508 * @buf: Where to copy to 509 * @buflen: The number of bytes to copy 510 * 511 * Returns the number of copied bytes. 512 * 513 **/ 514size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 515 void *buf, size_t buflen) 516{ 517 return sg_copy_buffer(sgl, nents, buf, buflen, 1); 518} 519EXPORT_SYMBOL(sg_copy_to_buffer); 520