Commit | Line | Data |
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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 | { | |
232f1b51 ML |
52 | int nents; |
53 | for (nents = 0; sg; sg = sg_next(sg)) | |
2e484610 | 54 | nents++; |
2e484610 ML |
55 | return nents; |
56 | } | |
57 | EXPORT_SYMBOL(sg_nents); | |
58 | ||
59 | ||
0db9299f JA |
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 | { | |
b94de9bb CW |
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 | |
0db9299f JA |
152 | return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); |
153 | } | |
154 | ||
155 | static void sg_kfree(struct scatterlist *sg, unsigned int nents) | |
156 | { | |
b94de9bb CW |
157 | if (nents == SG_MAX_SINGLE_ALLOC) { |
158 | kmemleak_free(sg); | |
0db9299f | 159 | free_page((unsigned long) sg); |
b94de9bb | 160 | } else |
0db9299f JA |
161 | kfree(sg); |
162 | } | |
163 | ||
164 | /** | |
165 | * __sg_free_table - Free a previously mapped sg table | |
166 | * @table: The sg table header to use | |
7cedb1f1 | 167 | * @max_ents: The maximum number of entries per single scatterlist |
0db9299f JA |
168 | * @free_fn: Free function |
169 | * | |
170 | * Description: | |
7cedb1f1 JB |
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(). | |
0db9299f JA |
174 | * |
175 | **/ | |
7cedb1f1 JB |
176 | void __sg_free_table(struct sg_table *table, unsigned int max_ents, |
177 | sg_free_fn *free_fn) | |
0db9299f JA |
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 | /* | |
7cedb1f1 | 190 | * If we have more than max_ents segments left, |
0db9299f JA |
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 | */ | |
7cedb1f1 JB |
195 | if (alloc_size > max_ents) { |
196 | next = sg_chain_ptr(&sgl[max_ents - 1]); | |
197 | alloc_size = max_ents; | |
0db9299f JA |
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 | { | |
7cedb1f1 | 220 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
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 | |
7cedb1f1 | 228 | * @max_ents: The maximum number of entries the allocator returns per call |
0db9299f JA |
229 | * @gfp_mask: GFP allocation mask |
230 | * @alloc_fn: Allocator to use | |
231 | * | |
7cedb1f1 JB |
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 | * | |
0db9299f JA |
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 | **/ | |
7cedb1f1 JB |
243 | int __sg_alloc_table(struct sg_table *table, unsigned int nents, |
244 | unsigned int max_ents, gfp_t gfp_mask, | |
0db9299f JA |
245 | sg_alloc_fn *alloc_fn) |
246 | { | |
247 | struct scatterlist *sg, *prv; | |
248 | unsigned int left; | |
249 | ||
250 | #ifndef ARCH_HAS_SG_CHAIN | |
7cedb1f1 | 251 | BUG_ON(nents > max_ents); |
0db9299f JA |
252 | #endif |
253 | ||
254 | memset(table, 0, sizeof(*table)); | |
255 | ||
256 | left = nents; | |
257 | prv = NULL; | |
258 | do { | |
259 | unsigned int sg_size, alloc_size = left; | |
260 | ||
7cedb1f1 JB |
261 | if (alloc_size > max_ents) { |
262 | alloc_size = max_ents; | |
0db9299f JA |
263 | sg_size = alloc_size - 1; |
264 | } else | |
265 | sg_size = alloc_size; | |
266 | ||
267 | left -= sg_size; | |
268 | ||
269 | sg = alloc_fn(alloc_size, gfp_mask); | |
edce6820 JC |
270 | if (unlikely(!sg)) { |
271 | /* | |
272 | * Adjust entry count to reflect that the last | |
273 | * entry of the previous table won't be used for | |
274 | * linkage. Without this, sg_kfree() may get | |
275 | * confused. | |
276 | */ | |
277 | if (prv) | |
278 | table->nents = ++table->orig_nents; | |
279 | ||
280 | return -ENOMEM; | |
281 | } | |
0db9299f JA |
282 | |
283 | sg_init_table(sg, alloc_size); | |
284 | table->nents = table->orig_nents += sg_size; | |
285 | ||
286 | /* | |
287 | * If this is the first mapping, assign the sg table header. | |
288 | * If this is not the first mapping, chain previous part. | |
289 | */ | |
290 | if (prv) | |
7cedb1f1 | 291 | sg_chain(prv, max_ents, sg); |
0db9299f JA |
292 | else |
293 | table->sgl = sg; | |
294 | ||
295 | /* | |
296 | * If no more entries after this one, mark the end | |
297 | */ | |
298 | if (!left) | |
299 | sg_mark_end(&sg[sg_size - 1]); | |
300 | ||
0db9299f JA |
301 | prv = sg; |
302 | } while (left); | |
303 | ||
304 | return 0; | |
305 | } | |
306 | EXPORT_SYMBOL(__sg_alloc_table); | |
307 | ||
308 | /** | |
309 | * sg_alloc_table - Allocate and initialize an sg table | |
310 | * @table: The sg table header to use | |
311 | * @nents: Number of entries in sg list | |
312 | * @gfp_mask: GFP allocation mask | |
313 | * | |
314 | * Description: | |
315 | * Allocate and initialize an sg table. If @nents@ is larger than | |
316 | * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. | |
317 | * | |
318 | **/ | |
319 | int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) | |
320 | { | |
321 | int ret; | |
322 | ||
7cedb1f1 JB |
323 | ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, |
324 | gfp_mask, sg_kmalloc); | |
0db9299f | 325 | if (unlikely(ret)) |
7cedb1f1 | 326 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
327 | |
328 | return ret; | |
329 | } | |
330 | EXPORT_SYMBOL(sg_alloc_table); | |
b1adaf65 | 331 | |
efc42bc9 TS |
332 | /** |
333 | * sg_alloc_table_from_pages - Allocate and initialize an sg table from | |
334 | * an array of pages | |
335 | * @sgt: The sg table header to use | |
336 | * @pages: Pointer to an array of page pointers | |
337 | * @n_pages: Number of pages in the pages array | |
338 | * @offset: Offset from start of the first page to the start of a buffer | |
339 | * @size: Number of valid bytes in the buffer (after offset) | |
340 | * @gfp_mask: GFP allocation mask | |
341 | * | |
342 | * Description: | |
343 | * Allocate and initialize an sg table from a list of pages. Contiguous | |
344 | * ranges of the pages are squashed into a single scatterlist node. A user | |
345 | * may provide an offset at a start and a size of valid data in a buffer | |
346 | * specified by the page array. The returned sg table is released by | |
347 | * sg_free_table. | |
348 | * | |
349 | * Returns: | |
350 | * 0 on success, negative error on failure | |
351 | */ | |
352 | int sg_alloc_table_from_pages(struct sg_table *sgt, | |
353 | struct page **pages, unsigned int n_pages, | |
354 | unsigned long offset, unsigned long size, | |
355 | gfp_t gfp_mask) | |
356 | { | |
357 | unsigned int chunks; | |
358 | unsigned int i; | |
359 | unsigned int cur_page; | |
360 | int ret; | |
361 | struct scatterlist *s; | |
362 | ||
363 | /* compute number of contiguous chunks */ | |
364 | chunks = 1; | |
365 | for (i = 1; i < n_pages; ++i) | |
366 | if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) | |
367 | ++chunks; | |
368 | ||
369 | ret = sg_alloc_table(sgt, chunks, gfp_mask); | |
370 | if (unlikely(ret)) | |
371 | return ret; | |
372 | ||
373 | /* merging chunks and putting them into the scatterlist */ | |
374 | cur_page = 0; | |
375 | for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { | |
376 | unsigned long chunk_size; | |
377 | unsigned int j; | |
378 | ||
379 | /* look for the end of the current chunk */ | |
380 | for (j = cur_page + 1; j < n_pages; ++j) | |
381 | if (page_to_pfn(pages[j]) != | |
382 | page_to_pfn(pages[j - 1]) + 1) | |
383 | break; | |
384 | ||
385 | chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; | |
386 | sg_set_page(s, pages[cur_page], min(size, chunk_size), offset); | |
387 | size -= chunk_size; | |
388 | offset = 0; | |
389 | cur_page = j; | |
390 | } | |
391 | ||
392 | return 0; | |
393 | } | |
394 | EXPORT_SYMBOL(sg_alloc_table_from_pages); | |
395 | ||
137d3edb TH |
396 | /** |
397 | * sg_miter_start - start mapping iteration over a sg list | |
398 | * @miter: sg mapping iter to be started | |
399 | * @sgl: sg list to iterate over | |
400 | * @nents: number of sg entries | |
401 | * | |
402 | * Description: | |
403 | * Starts mapping iterator @miter. | |
404 | * | |
405 | * Context: | |
406 | * Don't care. | |
407 | */ | |
408 | void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, | |
409 | unsigned int nents, unsigned int flags) | |
410 | { | |
411 | memset(miter, 0, sizeof(struct sg_mapping_iter)); | |
412 | ||
413 | miter->__sg = sgl; | |
414 | miter->__nents = nents; | |
415 | miter->__offset = 0; | |
6de7e356 | 416 | WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); |
137d3edb TH |
417 | miter->__flags = flags; |
418 | } | |
419 | EXPORT_SYMBOL(sg_miter_start); | |
420 | ||
421 | /** | |
422 | * sg_miter_next - proceed mapping iterator to the next mapping | |
423 | * @miter: sg mapping iter to proceed | |
424 | * | |
425 | * Description: | |
8290e2d2 TH |
426 | * Proceeds @miter to the next mapping. @miter should have been started |
427 | * using sg_miter_start(). On successful return, @miter->page, | |
428 | * @miter->addr and @miter->length point to the current mapping. | |
137d3edb TH |
429 | * |
430 | * Context: | |
8290e2d2 TH |
431 | * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled |
432 | * till @miter is stopped. May sleep if !SG_MITER_ATOMIC. | |
137d3edb TH |
433 | * |
434 | * Returns: | |
435 | * true if @miter contains the next mapping. false if end of sg | |
436 | * list is reached. | |
437 | */ | |
438 | bool sg_miter_next(struct sg_mapping_iter *miter) | |
439 | { | |
440 | unsigned int off, len; | |
441 | ||
442 | /* check for end and drop resources from the last iteration */ | |
443 | if (!miter->__nents) | |
444 | return false; | |
445 | ||
446 | sg_miter_stop(miter); | |
447 | ||
448 | /* get to the next sg if necessary. __offset is adjusted by stop */ | |
23c560a9 TH |
449 | while (miter->__offset == miter->__sg->length) { |
450 | if (--miter->__nents) { | |
451 | miter->__sg = sg_next(miter->__sg); | |
452 | miter->__offset = 0; | |
453 | } else | |
454 | return false; | |
137d3edb TH |
455 | } |
456 | ||
457 | /* map the next page */ | |
458 | off = miter->__sg->offset + miter->__offset; | |
459 | len = miter->__sg->length - miter->__offset; | |
460 | ||
461 | miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT); | |
462 | off &= ~PAGE_MASK; | |
463 | miter->length = min_t(unsigned int, len, PAGE_SIZE - off); | |
464 | miter->consumed = miter->length; | |
465 | ||
466 | if (miter->__flags & SG_MITER_ATOMIC) | |
c3eede8e | 467 | miter->addr = kmap_atomic(miter->page) + off; |
137d3edb TH |
468 | else |
469 | miter->addr = kmap(miter->page) + off; | |
470 | ||
471 | return true; | |
472 | } | |
473 | EXPORT_SYMBOL(sg_miter_next); | |
474 | ||
475 | /** | |
476 | * sg_miter_stop - stop mapping iteration | |
477 | * @miter: sg mapping iter to be stopped | |
478 | * | |
479 | * Description: | |
480 | * Stops mapping iterator @miter. @miter should have been started | |
481 | * started using sg_miter_start(). A stopped iteration can be | |
482 | * resumed by calling sg_miter_next() on it. This is useful when | |
483 | * resources (kmap) need to be released during iteration. | |
484 | * | |
485 | * Context: | |
8290e2d2 TH |
486 | * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care |
487 | * otherwise. | |
137d3edb TH |
488 | */ |
489 | void sg_miter_stop(struct sg_mapping_iter *miter) | |
490 | { | |
491 | WARN_ON(miter->consumed > miter->length); | |
492 | ||
493 | /* drop resources from the last iteration */ | |
494 | if (miter->addr) { | |
495 | miter->__offset += miter->consumed; | |
496 | ||
6de7e356 SAS |
497 | if (miter->__flags & SG_MITER_TO_SG) |
498 | flush_kernel_dcache_page(miter->page); | |
499 | ||
137d3edb | 500 | if (miter->__flags & SG_MITER_ATOMIC) { |
8290e2d2 | 501 | WARN_ON_ONCE(preemptible()); |
c3eede8e | 502 | kunmap_atomic(miter->addr); |
137d3edb | 503 | } else |
f652c521 | 504 | kunmap(miter->page); |
137d3edb TH |
505 | |
506 | miter->page = NULL; | |
507 | miter->addr = NULL; | |
508 | miter->length = 0; | |
509 | miter->consumed = 0; | |
510 | } | |
511 | } | |
512 | EXPORT_SYMBOL(sg_miter_stop); | |
513 | ||
b1adaf65 FT |
514 | /** |
515 | * sg_copy_buffer - Copy data between a linear buffer and an SG list | |
516 | * @sgl: The SG list | |
517 | * @nents: Number of SG entries | |
518 | * @buf: Where to copy from | |
519 | * @buflen: The number of bytes to copy | |
520 | * @to_buffer: transfer direction (non zero == from an sg list to a | |
521 | * buffer, 0 == from a buffer to an sg list | |
522 | * | |
523 | * Returns the number of copied bytes. | |
524 | * | |
525 | **/ | |
526 | static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, | |
527 | void *buf, size_t buflen, int to_buffer) | |
528 | { | |
137d3edb TH |
529 | unsigned int offset = 0; |
530 | struct sg_mapping_iter miter; | |
50bed2e2 | 531 | unsigned long flags; |
6de7e356 SAS |
532 | unsigned int sg_flags = SG_MITER_ATOMIC; |
533 | ||
534 | if (to_buffer) | |
535 | sg_flags |= SG_MITER_FROM_SG; | |
536 | else | |
537 | sg_flags |= SG_MITER_TO_SG; | |
137d3edb | 538 | |
6de7e356 | 539 | sg_miter_start(&miter, sgl, nents, sg_flags); |
137d3edb | 540 | |
50bed2e2 FT |
541 | local_irq_save(flags); |
542 | ||
137d3edb TH |
543 | while (sg_miter_next(&miter) && offset < buflen) { |
544 | unsigned int len; | |
545 | ||
546 | len = min(miter.length, buflen - offset); | |
547 | ||
548 | if (to_buffer) | |
549 | memcpy(buf + offset, miter.addr, len); | |
6de7e356 | 550 | else |
137d3edb | 551 | memcpy(miter.addr, buf + offset, len); |
b1adaf65 | 552 | |
137d3edb | 553 | offset += len; |
b1adaf65 FT |
554 | } |
555 | ||
137d3edb TH |
556 | sg_miter_stop(&miter); |
557 | ||
50bed2e2 | 558 | local_irq_restore(flags); |
137d3edb | 559 | return offset; |
b1adaf65 FT |
560 | } |
561 | ||
562 | /** | |
563 | * sg_copy_from_buffer - Copy from a linear buffer to an SG list | |
564 | * @sgl: The SG list | |
565 | * @nents: Number of SG entries | |
566 | * @buf: Where to copy from | |
567 | * @buflen: The number of bytes to copy | |
568 | * | |
569 | * Returns the number of copied bytes. | |
570 | * | |
571 | **/ | |
572 | size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, | |
573 | void *buf, size_t buflen) | |
574 | { | |
575 | return sg_copy_buffer(sgl, nents, buf, buflen, 0); | |
576 | } | |
577 | EXPORT_SYMBOL(sg_copy_from_buffer); | |
578 | ||
579 | /** | |
580 | * sg_copy_to_buffer - Copy from an SG list to a linear buffer | |
581 | * @sgl: The SG list | |
582 | * @nents: Number of SG entries | |
583 | * @buf: Where to copy to | |
584 | * @buflen: The number of bytes to copy | |
585 | * | |
586 | * Returns the number of copied bytes. | |
587 | * | |
588 | **/ | |
589 | size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, | |
590 | void *buf, size_t buflen) | |
591 | { | |
592 | return sg_copy_buffer(sgl, nents, buf, buflen, 1); | |
593 | } | |
594 | EXPORT_SYMBOL(sg_copy_to_buffer); |