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0db9299f JA |
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 | */ | |
8bc3bcc9 | 9 | #include <linux/export.h> |
5a0e3ad6 | 10 | #include <linux/slab.h> |
0db9299f | 11 | #include <linux/scatterlist.h> |
b1adaf65 | 12 | #include <linux/highmem.h> |
b94de9bb | 13 | #include <linux/kmemleak.h> |
0db9299f JA |
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 | ||
2e484610 ML |
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 = 0; | |
53 | while (sg) { | |
54 | nents++; | |
55 | sg = sg_next(sg); | |
56 | } | |
57 | ||
58 | return nents; | |
59 | } | |
60 | EXPORT_SYMBOL(sg_nents); | |
61 | ||
62 | ||
0db9299f JA |
63 | /** |
64 | * sg_last - return the last scatterlist entry in a list | |
65 | * @sgl: First entry in the scatterlist | |
66 | * @nents: Number of entries in the scatterlist | |
67 | * | |
68 | * Description: | |
69 | * Should only be used casually, it (currently) scans the entire list | |
70 | * to get the last entry. | |
71 | * | |
72 | * Note that the @sgl@ pointer passed in need not be the first one, | |
73 | * the important bit is that @nents@ denotes the number of entries that | |
74 | * exist from @sgl@. | |
75 | * | |
76 | **/ | |
77 | struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) | |
78 | { | |
79 | #ifndef ARCH_HAS_SG_CHAIN | |
80 | struct scatterlist *ret = &sgl[nents - 1]; | |
81 | #else | |
82 | struct scatterlist *sg, *ret = NULL; | |
83 | unsigned int i; | |
84 | ||
85 | for_each_sg(sgl, sg, nents, i) | |
86 | ret = sg; | |
87 | ||
88 | #endif | |
89 | #ifdef CONFIG_DEBUG_SG | |
90 | BUG_ON(sgl[0].sg_magic != SG_MAGIC); | |
91 | BUG_ON(!sg_is_last(ret)); | |
92 | #endif | |
93 | return ret; | |
94 | } | |
95 | EXPORT_SYMBOL(sg_last); | |
96 | ||
97 | /** | |
98 | * sg_init_table - Initialize SG table | |
99 | * @sgl: The SG table | |
100 | * @nents: Number of entries in table | |
101 | * | |
102 | * Notes: | |
103 | * If this is part of a chained sg table, sg_mark_end() should be | |
104 | * used only on the last table part. | |
105 | * | |
106 | **/ | |
107 | void sg_init_table(struct scatterlist *sgl, unsigned int nents) | |
108 | { | |
109 | memset(sgl, 0, sizeof(*sgl) * nents); | |
110 | #ifdef CONFIG_DEBUG_SG | |
111 | { | |
112 | unsigned int i; | |
113 | for (i = 0; i < nents; i++) | |
114 | sgl[i].sg_magic = SG_MAGIC; | |
115 | } | |
116 | #endif | |
117 | sg_mark_end(&sgl[nents - 1]); | |
118 | } | |
119 | EXPORT_SYMBOL(sg_init_table); | |
120 | ||
121 | /** | |
122 | * sg_init_one - Initialize a single entry sg list | |
123 | * @sg: SG entry | |
124 | * @buf: Virtual address for IO | |
125 | * @buflen: IO length | |
126 | * | |
127 | **/ | |
128 | void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) | |
129 | { | |
130 | sg_init_table(sg, 1); | |
131 | sg_set_buf(sg, buf, buflen); | |
132 | } | |
133 | EXPORT_SYMBOL(sg_init_one); | |
134 | ||
135 | /* | |
136 | * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree | |
137 | * helpers. | |
138 | */ | |
139 | static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) | |
140 | { | |
b94de9bb CW |
141 | if (nents == SG_MAX_SINGLE_ALLOC) { |
142 | /* | |
143 | * Kmemleak doesn't track page allocations as they are not | |
144 | * commonly used (in a raw form) for kernel data structures. | |
145 | * As we chain together a list of pages and then a normal | |
146 | * kmalloc (tracked by kmemleak), in order to for that last | |
147 | * allocation not to become decoupled (and thus a | |
148 | * false-positive) we need to inform kmemleak of all the | |
149 | * intermediate allocations. | |
150 | */ | |
151 | void *ptr = (void *) __get_free_page(gfp_mask); | |
152 | kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); | |
153 | return ptr; | |
154 | } else | |
0db9299f JA |
155 | return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); |
156 | } | |
157 | ||
158 | static void sg_kfree(struct scatterlist *sg, unsigned int nents) | |
159 | { | |
b94de9bb CW |
160 | if (nents == SG_MAX_SINGLE_ALLOC) { |
161 | kmemleak_free(sg); | |
0db9299f | 162 | free_page((unsigned long) sg); |
b94de9bb | 163 | } else |
0db9299f JA |
164 | kfree(sg); |
165 | } | |
166 | ||
167 | /** | |
168 | * __sg_free_table - Free a previously mapped sg table | |
169 | * @table: The sg table header to use | |
7cedb1f1 | 170 | * @max_ents: The maximum number of entries per single scatterlist |
0db9299f JA |
171 | * @free_fn: Free function |
172 | * | |
173 | * Description: | |
7cedb1f1 JB |
174 | * Free an sg table previously allocated and setup with |
175 | * __sg_alloc_table(). The @max_ents value must be identical to | |
176 | * that previously used with __sg_alloc_table(). | |
0db9299f JA |
177 | * |
178 | **/ | |
7cedb1f1 JB |
179 | void __sg_free_table(struct sg_table *table, unsigned int max_ents, |
180 | sg_free_fn *free_fn) | |
0db9299f JA |
181 | { |
182 | struct scatterlist *sgl, *next; | |
183 | ||
184 | if (unlikely(!table->sgl)) | |
185 | return; | |
186 | ||
187 | sgl = table->sgl; | |
188 | while (table->orig_nents) { | |
189 | unsigned int alloc_size = table->orig_nents; | |
190 | unsigned int sg_size; | |
191 | ||
192 | /* | |
7cedb1f1 | 193 | * If we have more than max_ents segments left, |
0db9299f JA |
194 | * then assign 'next' to the sg table after the current one. |
195 | * sg_size is then one less than alloc size, since the last | |
196 | * element is the chain pointer. | |
197 | */ | |
7cedb1f1 JB |
198 | if (alloc_size > max_ents) { |
199 | next = sg_chain_ptr(&sgl[max_ents - 1]); | |
200 | alloc_size = max_ents; | |
0db9299f JA |
201 | sg_size = alloc_size - 1; |
202 | } else { | |
203 | sg_size = alloc_size; | |
204 | next = NULL; | |
205 | } | |
206 | ||
207 | table->orig_nents -= sg_size; | |
208 | free_fn(sgl, alloc_size); | |
209 | sgl = next; | |
210 | } | |
211 | ||
212 | table->sgl = NULL; | |
213 | } | |
214 | EXPORT_SYMBOL(__sg_free_table); | |
215 | ||
216 | /** | |
217 | * sg_free_table - Free a previously allocated sg table | |
218 | * @table: The mapped sg table header | |
219 | * | |
220 | **/ | |
221 | void sg_free_table(struct sg_table *table) | |
222 | { | |
7cedb1f1 | 223 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
224 | } |
225 | EXPORT_SYMBOL(sg_free_table); | |
226 | ||
227 | /** | |
228 | * __sg_alloc_table - Allocate and initialize an sg table with given allocator | |
229 | * @table: The sg table header to use | |
230 | * @nents: Number of entries in sg list | |
7cedb1f1 | 231 | * @max_ents: The maximum number of entries the allocator returns per call |
0db9299f JA |
232 | * @gfp_mask: GFP allocation mask |
233 | * @alloc_fn: Allocator to use | |
234 | * | |
7cedb1f1 JB |
235 | * Description: |
236 | * This function returns a @table @nents long. The allocator is | |
237 | * defined to return scatterlist chunks of maximum size @max_ents. | |
238 | * Thus if @nents is bigger than @max_ents, the scatterlists will be | |
239 | * chained in units of @max_ents. | |
240 | * | |
0db9299f JA |
241 | * Notes: |
242 | * If this function returns non-0 (eg failure), the caller must call | |
243 | * __sg_free_table() to cleanup any leftover allocations. | |
244 | * | |
245 | **/ | |
7cedb1f1 JB |
246 | int __sg_alloc_table(struct sg_table *table, unsigned int nents, |
247 | unsigned int max_ents, gfp_t gfp_mask, | |
0db9299f JA |
248 | sg_alloc_fn *alloc_fn) |
249 | { | |
250 | struct scatterlist *sg, *prv; | |
251 | unsigned int left; | |
252 | ||
253 | #ifndef ARCH_HAS_SG_CHAIN | |
7cedb1f1 | 254 | BUG_ON(nents > max_ents); |
0db9299f JA |
255 | #endif |
256 | ||
257 | memset(table, 0, sizeof(*table)); | |
258 | ||
259 | left = nents; | |
260 | prv = NULL; | |
261 | do { | |
262 | unsigned int sg_size, alloc_size = left; | |
263 | ||
7cedb1f1 JB |
264 | if (alloc_size > max_ents) { |
265 | alloc_size = max_ents; | |
0db9299f JA |
266 | sg_size = alloc_size - 1; |
267 | } else | |
268 | sg_size = alloc_size; | |
269 | ||
270 | left -= sg_size; | |
271 | ||
272 | sg = alloc_fn(alloc_size, gfp_mask); | |
edce6820 JC |
273 | if (unlikely(!sg)) { |
274 | /* | |
275 | * Adjust entry count to reflect that the last | |
276 | * entry of the previous table won't be used for | |
277 | * linkage. Without this, sg_kfree() may get | |
278 | * confused. | |
279 | */ | |
280 | if (prv) | |
281 | table->nents = ++table->orig_nents; | |
282 | ||
283 | return -ENOMEM; | |
284 | } | |
0db9299f JA |
285 | |
286 | sg_init_table(sg, alloc_size); | |
287 | table->nents = table->orig_nents += sg_size; | |
288 | ||
289 | /* | |
290 | * If this is the first mapping, assign the sg table header. | |
291 | * If this is not the first mapping, chain previous part. | |
292 | */ | |
293 | if (prv) | |
7cedb1f1 | 294 | sg_chain(prv, max_ents, sg); |
0db9299f JA |
295 | else |
296 | table->sgl = sg; | |
297 | ||
298 | /* | |
299 | * If no more entries after this one, mark the end | |
300 | */ | |
301 | if (!left) | |
302 | sg_mark_end(&sg[sg_size - 1]); | |
303 | ||
0db9299f JA |
304 | prv = sg; |
305 | } while (left); | |
306 | ||
307 | return 0; | |
308 | } | |
309 | EXPORT_SYMBOL(__sg_alloc_table); | |
310 | ||
311 | /** | |
312 | * sg_alloc_table - Allocate and initialize an sg table | |
313 | * @table: The sg table header to use | |
314 | * @nents: Number of entries in sg list | |
315 | * @gfp_mask: GFP allocation mask | |
316 | * | |
317 | * Description: | |
318 | * Allocate and initialize an sg table. If @nents@ is larger than | |
319 | * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. | |
320 | * | |
321 | **/ | |
322 | int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) | |
323 | { | |
324 | int ret; | |
325 | ||
7cedb1f1 JB |
326 | ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, |
327 | gfp_mask, sg_kmalloc); | |
0db9299f | 328 | if (unlikely(ret)) |
7cedb1f1 | 329 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
330 | |
331 | return ret; | |
332 | } | |
333 | EXPORT_SYMBOL(sg_alloc_table); | |
b1adaf65 | 334 | |
efc42bc9 TS |
335 | /** |
336 | * sg_alloc_table_from_pages - Allocate and initialize an sg table from | |
337 | * an array of pages | |
338 | * @sgt: The sg table header to use | |
339 | * @pages: Pointer to an array of page pointers | |
340 | * @n_pages: Number of pages in the pages array | |
341 | * @offset: Offset from start of the first page to the start of a buffer | |
342 | * @size: Number of valid bytes in the buffer (after offset) | |
343 | * @gfp_mask: GFP allocation mask | |
344 | * | |
345 | * Description: | |
346 | * Allocate and initialize an sg table from a list of pages. Contiguous | |
347 | * ranges of the pages are squashed into a single scatterlist node. A user | |
348 | * may provide an offset at a start and a size of valid data in a buffer | |
349 | * specified by the page array. The returned sg table is released by | |
350 | * sg_free_table. | |
351 | * | |
352 | * Returns: | |
353 | * 0 on success, negative error on failure | |
354 | */ | |
355 | int sg_alloc_table_from_pages(struct sg_table *sgt, | |
356 | struct page **pages, unsigned int n_pages, | |
357 | unsigned long offset, unsigned long size, | |
358 | gfp_t gfp_mask) | |
359 | { | |
360 | unsigned int chunks; | |
361 | unsigned int i; | |
362 | unsigned int cur_page; | |
363 | int ret; | |
364 | struct scatterlist *s; | |
365 | ||
366 | /* compute number of contiguous chunks */ | |
367 | chunks = 1; | |
368 | for (i = 1; i < n_pages; ++i) | |
369 | if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) | |
370 | ++chunks; | |
371 | ||
372 | ret = sg_alloc_table(sgt, chunks, gfp_mask); | |
373 | if (unlikely(ret)) | |
374 | return ret; | |
375 | ||
376 | /* merging chunks and putting them into the scatterlist */ | |
377 | cur_page = 0; | |
378 | for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { | |
379 | unsigned long chunk_size; | |
380 | unsigned int j; | |
381 | ||
382 | /* look for the end of the current chunk */ | |
383 | for (j = cur_page + 1; j < n_pages; ++j) | |
384 | if (page_to_pfn(pages[j]) != | |
385 | page_to_pfn(pages[j - 1]) + 1) | |
386 | break; | |
387 | ||
388 | chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; | |
389 | sg_set_page(s, pages[cur_page], min(size, chunk_size), offset); | |
390 | size -= chunk_size; | |
391 | offset = 0; | |
392 | cur_page = j; | |
393 | } | |
394 | ||
395 | return 0; | |
396 | } | |
397 | EXPORT_SYMBOL(sg_alloc_table_from_pages); | |
398 | ||
137d3edb TH |
399 | /** |
400 | * sg_miter_start - start mapping iteration over a sg list | |
401 | * @miter: sg mapping iter to be started | |
402 | * @sgl: sg list to iterate over | |
403 | * @nents: number of sg entries | |
404 | * | |
405 | * Description: | |
406 | * Starts mapping iterator @miter. | |
407 | * | |
408 | * Context: | |
409 | * Don't care. | |
410 | */ | |
411 | void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, | |
412 | unsigned int nents, unsigned int flags) | |
413 | { | |
414 | memset(miter, 0, sizeof(struct sg_mapping_iter)); | |
415 | ||
416 | miter->__sg = sgl; | |
417 | miter->__nents = nents; | |
418 | miter->__offset = 0; | |
6de7e356 | 419 | WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); |
137d3edb TH |
420 | miter->__flags = flags; |
421 | } | |
422 | EXPORT_SYMBOL(sg_miter_start); | |
423 | ||
424 | /** | |
425 | * sg_miter_next - proceed mapping iterator to the next mapping | |
426 | * @miter: sg mapping iter to proceed | |
427 | * | |
428 | * Description: | |
429 | * Proceeds @miter@ to the next mapping. @miter@ should have been | |
430 | * started using sg_miter_start(). On successful return, | |
431 | * @miter@->page, @miter@->addr and @miter@->length point to the | |
432 | * current mapping. | |
433 | * | |
434 | * Context: | |
435 | * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till | |
436 | * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC. | |
437 | * | |
438 | * Returns: | |
439 | * true if @miter contains the next mapping. false if end of sg | |
440 | * list is reached. | |
441 | */ | |
442 | bool sg_miter_next(struct sg_mapping_iter *miter) | |
443 | { | |
444 | unsigned int off, len; | |
445 | ||
446 | /* check for end and drop resources from the last iteration */ | |
447 | if (!miter->__nents) | |
448 | return false; | |
449 | ||
450 | sg_miter_stop(miter); | |
451 | ||
452 | /* get to the next sg if necessary. __offset is adjusted by stop */ | |
23c560a9 TH |
453 | while (miter->__offset == miter->__sg->length) { |
454 | if (--miter->__nents) { | |
455 | miter->__sg = sg_next(miter->__sg); | |
456 | miter->__offset = 0; | |
457 | } else | |
458 | return false; | |
137d3edb TH |
459 | } |
460 | ||
461 | /* map the next page */ | |
462 | off = miter->__sg->offset + miter->__offset; | |
463 | len = miter->__sg->length - miter->__offset; | |
464 | ||
465 | miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT); | |
466 | off &= ~PAGE_MASK; | |
467 | miter->length = min_t(unsigned int, len, PAGE_SIZE - off); | |
468 | miter->consumed = miter->length; | |
469 | ||
470 | if (miter->__flags & SG_MITER_ATOMIC) | |
c3eede8e | 471 | miter->addr = kmap_atomic(miter->page) + off; |
137d3edb TH |
472 | else |
473 | miter->addr = kmap(miter->page) + off; | |
474 | ||
475 | return true; | |
476 | } | |
477 | EXPORT_SYMBOL(sg_miter_next); | |
478 | ||
479 | /** | |
480 | * sg_miter_stop - stop mapping iteration | |
481 | * @miter: sg mapping iter to be stopped | |
482 | * | |
483 | * Description: | |
484 | * Stops mapping iterator @miter. @miter should have been started | |
485 | * started using sg_miter_start(). A stopped iteration can be | |
486 | * resumed by calling sg_miter_next() on it. This is useful when | |
487 | * resources (kmap) need to be released during iteration. | |
488 | * | |
489 | * Context: | |
490 | * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise. | |
491 | */ | |
492 | void sg_miter_stop(struct sg_mapping_iter *miter) | |
493 | { | |
494 | WARN_ON(miter->consumed > miter->length); | |
495 | ||
496 | /* drop resources from the last iteration */ | |
497 | if (miter->addr) { | |
498 | miter->__offset += miter->consumed; | |
499 | ||
6de7e356 SAS |
500 | if (miter->__flags & SG_MITER_TO_SG) |
501 | flush_kernel_dcache_page(miter->page); | |
502 | ||
137d3edb TH |
503 | if (miter->__flags & SG_MITER_ATOMIC) { |
504 | WARN_ON(!irqs_disabled()); | |
c3eede8e | 505 | kunmap_atomic(miter->addr); |
137d3edb | 506 | } else |
f652c521 | 507 | kunmap(miter->page); |
137d3edb TH |
508 | |
509 | miter->page = NULL; | |
510 | miter->addr = NULL; | |
511 | miter->length = 0; | |
512 | miter->consumed = 0; | |
513 | } | |
514 | } | |
515 | EXPORT_SYMBOL(sg_miter_stop); | |
516 | ||
b1adaf65 FT |
517 | /** |
518 | * sg_copy_buffer - Copy data between a linear buffer and an SG list | |
519 | * @sgl: The SG list | |
520 | * @nents: Number of SG entries | |
521 | * @buf: Where to copy from | |
522 | * @buflen: The number of bytes to copy | |
523 | * @to_buffer: transfer direction (non zero == from an sg list to a | |
524 | * buffer, 0 == from a buffer to an sg list | |
525 | * | |
526 | * Returns the number of copied bytes. | |
527 | * | |
528 | **/ | |
529 | static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, | |
530 | void *buf, size_t buflen, int to_buffer) | |
531 | { | |
137d3edb TH |
532 | unsigned int offset = 0; |
533 | struct sg_mapping_iter miter; | |
50bed2e2 | 534 | unsigned long flags; |
6de7e356 SAS |
535 | unsigned int sg_flags = SG_MITER_ATOMIC; |
536 | ||
537 | if (to_buffer) | |
538 | sg_flags |= SG_MITER_FROM_SG; | |
539 | else | |
540 | sg_flags |= SG_MITER_TO_SG; | |
137d3edb | 541 | |
6de7e356 | 542 | sg_miter_start(&miter, sgl, nents, sg_flags); |
137d3edb | 543 | |
50bed2e2 FT |
544 | local_irq_save(flags); |
545 | ||
137d3edb TH |
546 | while (sg_miter_next(&miter) && offset < buflen) { |
547 | unsigned int len; | |
548 | ||
549 | len = min(miter.length, buflen - offset); | |
550 | ||
551 | if (to_buffer) | |
552 | memcpy(buf + offset, miter.addr, len); | |
6de7e356 | 553 | else |
137d3edb | 554 | memcpy(miter.addr, buf + offset, len); |
b1adaf65 | 555 | |
137d3edb | 556 | offset += len; |
b1adaf65 FT |
557 | } |
558 | ||
137d3edb TH |
559 | sg_miter_stop(&miter); |
560 | ||
50bed2e2 | 561 | local_irq_restore(flags); |
137d3edb | 562 | return offset; |
b1adaf65 FT |
563 | } |
564 | ||
565 | /** | |
566 | * sg_copy_from_buffer - Copy from a linear buffer to an SG list | |
567 | * @sgl: The SG list | |
568 | * @nents: Number of SG entries | |
569 | * @buf: Where to copy from | |
570 | * @buflen: The number of bytes to copy | |
571 | * | |
572 | * Returns the number of copied bytes. | |
573 | * | |
574 | **/ | |
575 | size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, | |
576 | void *buf, size_t buflen) | |
577 | { | |
578 | return sg_copy_buffer(sgl, nents, buf, buflen, 0); | |
579 | } | |
580 | EXPORT_SYMBOL(sg_copy_from_buffer); | |
581 | ||
582 | /** | |
583 | * sg_copy_to_buffer - Copy from an SG list to a linear buffer | |
584 | * @sgl: The SG list | |
585 | * @nents: Number of SG entries | |
586 | * @buf: Where to copy to | |
587 | * @buflen: The number of bytes to copy | |
588 | * | |
589 | * Returns the number of copied bytes. | |
590 | * | |
591 | **/ | |
592 | size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, | |
593 | void *buf, size_t buflen) | |
594 | { | |
595 | return sg_copy_buffer(sgl, nents, buf, buflen, 1); | |
596 | } | |
597 | EXPORT_SYMBOL(sg_copy_to_buffer); |