blob: 3675452b23ca175b612489e362aa7274b75d96a5 [file] [log] [blame]
Jens Axboe0db92992007-11-30 09:16:50 +01001/*
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 */
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -05009#include <linux/export.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090010#include <linux/slab.h>
Jens Axboe0db92992007-11-30 09:16:50 +010011#include <linux/scatterlist.h>
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +090012#include <linux/highmem.h>
Chris Wilsonb94de9b2010-07-28 22:59:02 +010013#include <linux/kmemleak.h>
Jens Axboe0db92992007-11-30 09:16:50 +010014
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/**
Maxim Levitsky2e484612012-09-27 12:45:28 +020042 * 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 **/
50int sg_nents(struct scatterlist *sg)
51{
Maxim Levitsky232f1b52012-09-28 10:38:15 +020052 int nents;
53 for (nents = 0; sg; sg = sg_next(sg))
Maxim Levitsky2e484612012-09-27 12:45:28 +020054 nents++;
Maxim Levitsky2e484612012-09-27 12:45:28 +020055 return nents;
56}
57EXPORT_SYMBOL(sg_nents);
58
59
60/**
Jens Axboe0db92992007-11-30 09:16:50 +010061 * 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 **/
74struct 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}
92EXPORT_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 **/
104void 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}
116EXPORT_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 **/
125void 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}
130EXPORT_SYMBOL(sg_init_one);
131
132/*
133 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
134 * helpers.
135 */
136static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
137{
Chris Wilsonb94de9b2010-07-28 22:59:02 +0100138 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
Jens Axboe0db92992007-11-30 09:16:50 +0100152 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
153}
154
155static void sg_kfree(struct scatterlist *sg, unsigned int nents)
156{
Chris Wilsonb94de9b2010-07-28 22:59:02 +0100157 if (nents == SG_MAX_SINGLE_ALLOC) {
158 kmemleak_free(sg);
Jens Axboe0db92992007-11-30 09:16:50 +0100159 free_page((unsigned long) sg);
Chris Wilsonb94de9b2010-07-28 22:59:02 +0100160 } else
Jens Axboe0db92992007-11-30 09:16:50 +0100161 kfree(sg);
162}
163
164/**
165 * __sg_free_table - Free a previously mapped sg table
166 * @table: The sg table header to use
James Bottomley7cedb1f2008-01-13 14:15:28 -0600167 * @max_ents: The maximum number of entries per single scatterlist
Jens Axboe0db92992007-11-30 09:16:50 +0100168 * @free_fn: Free function
169 *
170 * Description:
James Bottomley7cedb1f2008-01-13 14:15:28 -0600171 * 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().
Jens Axboe0db92992007-11-30 09:16:50 +0100174 *
175 **/
James Bottomley7cedb1f2008-01-13 14:15:28 -0600176void __sg_free_table(struct sg_table *table, unsigned int max_ents,
177 sg_free_fn *free_fn)
Jens Axboe0db92992007-11-30 09:16:50 +0100178{
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 /*
James Bottomley7cedb1f2008-01-13 14:15:28 -0600190 * If we have more than max_ents segments left,
Jens Axboe0db92992007-11-30 09:16:50 +0100191 * 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 */
James Bottomley7cedb1f2008-01-13 14:15:28 -0600195 if (alloc_size > max_ents) {
196 next = sg_chain_ptr(&sgl[max_ents - 1]);
197 alloc_size = max_ents;
Jens Axboe0db92992007-11-30 09:16:50 +0100198 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}
211EXPORT_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 **/
218void sg_free_table(struct sg_table *table)
219{
James Bottomley7cedb1f2008-01-13 14:15:28 -0600220 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
Jens Axboe0db92992007-11-30 09:16:50 +0100221}
222EXPORT_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
James Bottomley7cedb1f2008-01-13 14:15:28 -0600228 * @max_ents: The maximum number of entries the allocator returns per call
Jens Axboe0db92992007-11-30 09:16:50 +0100229 * @gfp_mask: GFP allocation mask
230 * @alloc_fn: Allocator to use
231 *
James Bottomley7cedb1f2008-01-13 14:15:28 -0600232 * 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 *
Jens Axboe0db92992007-11-30 09:16:50 +0100238 * 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 **/
James Bottomley7cedb1f2008-01-13 14:15:28 -0600243int __sg_alloc_table(struct sg_table *table, unsigned int nents,
244 unsigned int max_ents, gfp_t gfp_mask,
Jens Axboe0db92992007-11-30 09:16:50 +0100245 sg_alloc_fn *alloc_fn)
246{
247 struct scatterlist *sg, *prv;
248 unsigned int left;
249
250#ifndef ARCH_HAS_SG_CHAIN
James Bottomley7cedb1f2008-01-13 14:15:28 -0600251 BUG_ON(nents > max_ents);
Jens Axboe0db92992007-11-30 09:16:50 +0100252#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
James Bottomley7cedb1f2008-01-13 14:15:28 -0600261 if (alloc_size > max_ents) {
262 alloc_size = max_ents;
Jens Axboe0db92992007-11-30 09:16:50 +0100263 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);
Jeffrey Carlyleedce6822010-08-30 19:55:09 +0200270 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 }
Jens Axboe0db92992007-11-30 09:16:50 +0100282
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)
James Bottomley7cedb1f2008-01-13 14:15:28 -0600291 sg_chain(prv, max_ents, sg);
Jens Axboe0db92992007-11-30 09:16:50 +0100292 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
Jens Axboe0db92992007-11-30 09:16:50 +0100301 prv = sg;
302 } while (left);
303
304 return 0;
305}
306EXPORT_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 **/
319int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
320{
321 int ret;
322
James Bottomley7cedb1f2008-01-13 14:15:28 -0600323 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
324 gfp_mask, sg_kmalloc);
Jens Axboe0db92992007-11-30 09:16:50 +0100325 if (unlikely(ret))
James Bottomley7cedb1f2008-01-13 14:15:28 -0600326 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
Jens Axboe0db92992007-11-30 09:16:50 +0100327
328 return ret;
329}
330EXPORT_SYMBOL(sg_alloc_table);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900331
332/**
Tomasz Stanislawskiefc42bc2012-06-18 09:25:01 +0200333 * 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 */
352int 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}
394EXPORT_SYMBOL(sg_alloc_table_from_pages);
395
396/**
Tejun Heo137d3ed2008-07-19 23:03:35 +0900397 * 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 */
408void 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;
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200416 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
Tejun Heo137d3ed2008-07-19 23:03:35 +0900417 miter->__flags = flags;
418}
419EXPORT_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:
Tejun Heo8290e2d2012-10-04 17:13:28 -0700426 * 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.
Tejun Heo137d3ed2008-07-19 23:03:35 +0900429 *
430 * Context:
Tejun Heo8290e2d2012-10-04 17:13:28 -0700431 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
432 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
Tejun Heo137d3ed2008-07-19 23:03:35 +0900433 *
434 * Returns:
435 * true if @miter contains the next mapping. false if end of sg
436 * list is reached.
437 */
438bool 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 */
Tejun Heo23c560a2009-04-15 22:10:23 +0900449 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;
Tejun Heo137d3ed2008-07-19 23:03:35 +0900455 }
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)
Cong Wangc3eede82011-11-25 23:14:39 +0800467 miter->addr = kmap_atomic(miter->page) + off;
Tejun Heo137d3ed2008-07-19 23:03:35 +0900468 else
469 miter->addr = kmap(miter->page) + off;
470
471 return true;
472}
473EXPORT_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:
Tejun Heo8290e2d2012-10-04 17:13:28 -0700486 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
487 * otherwise.
Tejun Heo137d3ed2008-07-19 23:03:35 +0900488 */
489void 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
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200497 if (miter->__flags & SG_MITER_TO_SG)
498 flush_kernel_dcache_page(miter->page);
499
Tejun Heo137d3ed2008-07-19 23:03:35 +0900500 if (miter->__flags & SG_MITER_ATOMIC) {
Tejun Heo8290e2d2012-10-04 17:13:28 -0700501 WARN_ON_ONCE(preemptible());
Cong Wangc3eede82011-11-25 23:14:39 +0800502 kunmap_atomic(miter->addr);
Tejun Heo137d3ed2008-07-19 23:03:35 +0900503 } else
Arjan van de Venf652c522008-11-19 15:36:19 -0800504 kunmap(miter->page);
Tejun Heo137d3ed2008-07-19 23:03:35 +0900505
506 miter->page = NULL;
507 miter->addr = NULL;
508 miter->length = 0;
509 miter->consumed = 0;
510 }
511}
512EXPORT_SYMBOL(sg_miter_stop);
513
514/**
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900515 * 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 **/
526static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
527 void *buf, size_t buflen, int to_buffer)
528{
Tejun Heo137d3ed2008-07-19 23:03:35 +0900529 unsigned int offset = 0;
530 struct sg_mapping_iter miter;
FUJITA Tomonori50bed2e2008-09-11 18:35:39 +0200531 unsigned long flags;
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200532 unsigned int sg_flags = SG_MITER_ATOMIC;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900533
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200534 if (to_buffer)
535 sg_flags |= SG_MITER_FROM_SG;
536 else
537 sg_flags |= SG_MITER_TO_SG;
538
539 sg_miter_start(&miter, sgl, nents, sg_flags);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900540
FUJITA Tomonori50bed2e2008-09-11 18:35:39 +0200541 local_irq_save(flags);
542
Tejun Heo137d3ed2008-07-19 23:03:35 +0900543 while (sg_miter_next(&miter) && offset < buflen) {
544 unsigned int len;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900545
Tejun Heo137d3ed2008-07-19 23:03:35 +0900546 len = min(miter.length, buflen - offset);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900547
Tejun Heo137d3ed2008-07-19 23:03:35 +0900548 if (to_buffer)
549 memcpy(buf + offset, miter.addr, len);
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200550 else
Tejun Heo137d3ed2008-07-19 23:03:35 +0900551 memcpy(miter.addr, buf + offset, len);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900552
Tejun Heo137d3ed2008-07-19 23:03:35 +0900553 offset += len;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900554 }
555
Tejun Heo137d3ed2008-07-19 23:03:35 +0900556 sg_miter_stop(&miter);
557
FUJITA Tomonori50bed2e2008-09-11 18:35:39 +0200558 local_irq_restore(flags);
Tejun Heo137d3ed2008-07-19 23:03:35 +0900559 return offset;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900560}
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 **/
572size_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}
577EXPORT_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 **/
589size_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}
594EXPORT_SYMBOL(sg_copy_to_buffer);