Loading...
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 **/
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_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{
52 int nents;
53 for (nents = 0; sg; sg = sg_next(sg))
54 nents++;
55 return nents;
56}
57EXPORT_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 **/
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{
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
155static 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 **/
176void __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}
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{
220 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
221}
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
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 **/
243int __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 memset(table, 0, sizeof(*table));
251
252 if (nents == 0)
253 return -EINVAL;
254#ifndef ARCH_HAS_SG_CHAIN
255 if (WARN_ON_ONCE(nents > max_ents))
256 return -EINVAL;
257#endif
258
259 left = nents;
260 prv = NULL;
261 do {
262 unsigned int sg_size, alloc_size = left;
263
264 if (alloc_size > max_ents) {
265 alloc_size = max_ents;
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);
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 }
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)
294 sg_chain(prv, max_ents, sg);
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
304 prv = sg;
305 } while (left);
306
307 return 0;
308}
309EXPORT_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 **/
322int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
323{
324 int ret;
325
326 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
327 gfp_mask, sg_kmalloc);
328 if (unlikely(ret))
329 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
330
331 return ret;
332}
333EXPORT_SYMBOL(sg_alloc_table);
334
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 */
355int 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}
397EXPORT_SYMBOL(sg_alloc_table_from_pages);
398
399void __sg_page_iter_start(struct sg_page_iter *piter,
400 struct scatterlist *sglist, unsigned int nents,
401 unsigned long pgoffset)
402{
403 piter->__pg_advance = 0;
404 piter->__nents = nents;
405
406 piter->sg = sglist;
407 piter->sg_pgoffset = pgoffset;
408}
409EXPORT_SYMBOL(__sg_page_iter_start);
410
411static int sg_page_count(struct scatterlist *sg)
412{
413 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
414}
415
416bool __sg_page_iter_next(struct sg_page_iter *piter)
417{
418 if (!piter->__nents || !piter->sg)
419 return false;
420
421 piter->sg_pgoffset += piter->__pg_advance;
422 piter->__pg_advance = 1;
423
424 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
425 piter->sg_pgoffset -= sg_page_count(piter->sg);
426 piter->sg = sg_next(piter->sg);
427 if (!--piter->__nents || !piter->sg)
428 return false;
429 }
430
431 return true;
432}
433EXPORT_SYMBOL(__sg_page_iter_next);
434
435/**
436 * sg_miter_start - start mapping iteration over a sg list
437 * @miter: sg mapping iter to be started
438 * @sgl: sg list to iterate over
439 * @nents: number of sg entries
440 *
441 * Description:
442 * Starts mapping iterator @miter.
443 *
444 * Context:
445 * Don't care.
446 */
447void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
448 unsigned int nents, unsigned int flags)
449{
450 memset(miter, 0, sizeof(struct sg_mapping_iter));
451
452 __sg_page_iter_start(&miter->piter, sgl, nents, 0);
453 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
454 miter->__flags = flags;
455}
456EXPORT_SYMBOL(sg_miter_start);
457
458static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
459{
460 if (!miter->__remaining) {
461 struct scatterlist *sg;
462 unsigned long pgoffset;
463
464 if (!__sg_page_iter_next(&miter->piter))
465 return false;
466
467 sg = miter->piter.sg;
468 pgoffset = miter->piter.sg_pgoffset;
469
470 miter->__offset = pgoffset ? 0 : sg->offset;
471 miter->__remaining = sg->offset + sg->length -
472 (pgoffset << PAGE_SHIFT) - miter->__offset;
473 miter->__remaining = min_t(unsigned long, miter->__remaining,
474 PAGE_SIZE - miter->__offset);
475 }
476
477 return true;
478}
479
480/**
481 * sg_miter_skip - reposition mapping iterator
482 * @miter: sg mapping iter to be skipped
483 * @offset: number of bytes to plus the current location
484 *
485 * Description:
486 * Sets the offset of @miter to its current location plus @offset bytes.
487 * If mapping iterator @miter has been proceeded by sg_miter_next(), this
488 * stops @miter.
489 *
490 * Context:
491 * Don't care if @miter is stopped, or not proceeded yet.
492 * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
493 *
494 * Returns:
495 * true if @miter contains the valid mapping. false if end of sg
496 * list is reached.
497 */
498bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
499{
500 sg_miter_stop(miter);
501
502 while (offset) {
503 off_t consumed;
504
505 if (!sg_miter_get_next_page(miter))
506 return false;
507
508 consumed = min_t(off_t, offset, miter->__remaining);
509 miter->__offset += consumed;
510 miter->__remaining -= consumed;
511 offset -= consumed;
512 }
513
514 return true;
515}
516EXPORT_SYMBOL(sg_miter_skip);
517
518/**
519 * sg_miter_next - proceed mapping iterator to the next mapping
520 * @miter: sg mapping iter to proceed
521 *
522 * Description:
523 * Proceeds @miter to the next mapping. @miter should have been started
524 * using sg_miter_start(). On successful return, @miter->page,
525 * @miter->addr and @miter->length point to the current mapping.
526 *
527 * Context:
528 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
529 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
530 *
531 * Returns:
532 * true if @miter contains the next mapping. false if end of sg
533 * list is reached.
534 */
535bool sg_miter_next(struct sg_mapping_iter *miter)
536{
537 sg_miter_stop(miter);
538
539 /*
540 * Get to the next page if necessary.
541 * __remaining, __offset is adjusted by sg_miter_stop
542 */
543 if (!sg_miter_get_next_page(miter))
544 return false;
545
546 miter->page = sg_page_iter_page(&miter->piter);
547 miter->consumed = miter->length = miter->__remaining;
548
549 if (miter->__flags & SG_MITER_ATOMIC)
550 miter->addr = kmap_atomic(miter->page) + miter->__offset;
551 else
552 miter->addr = kmap(miter->page) + miter->__offset;
553
554 return true;
555}
556EXPORT_SYMBOL(sg_miter_next);
557
558/**
559 * sg_miter_stop - stop mapping iteration
560 * @miter: sg mapping iter to be stopped
561 *
562 * Description:
563 * Stops mapping iterator @miter. @miter should have been started
564 * started using sg_miter_start(). A stopped iteration can be
565 * resumed by calling sg_miter_next() on it. This is useful when
566 * resources (kmap) need to be released during iteration.
567 *
568 * Context:
569 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
570 * otherwise.
571 */
572void sg_miter_stop(struct sg_mapping_iter *miter)
573{
574 WARN_ON(miter->consumed > miter->length);
575
576 /* drop resources from the last iteration */
577 if (miter->addr) {
578 miter->__offset += miter->consumed;
579 miter->__remaining -= miter->consumed;
580
581 if ((miter->__flags & SG_MITER_TO_SG) &&
582 !PageSlab(miter->page))
583 flush_kernel_dcache_page(miter->page);
584
585 if (miter->__flags & SG_MITER_ATOMIC) {
586 WARN_ON_ONCE(preemptible());
587 kunmap_atomic(miter->addr);
588 } else
589 kunmap(miter->page);
590
591 miter->page = NULL;
592 miter->addr = NULL;
593 miter->length = 0;
594 miter->consumed = 0;
595 }
596}
597EXPORT_SYMBOL(sg_miter_stop);
598
599/**
600 * sg_copy_buffer - Copy data between a linear buffer and an SG list
601 * @sgl: The SG list
602 * @nents: Number of SG entries
603 * @buf: Where to copy from
604 * @buflen: The number of bytes to copy
605 * @skip: Number of bytes to skip before copying
606 * @to_buffer: transfer direction (true == from an sg list to a
607 * buffer, false == from a buffer to an sg list
608 *
609 * Returns the number of copied bytes.
610 *
611 **/
612static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
613 void *buf, size_t buflen, off_t skip,
614 bool to_buffer)
615{
616 unsigned int offset = 0;
617 struct sg_mapping_iter miter;
618 unsigned long flags;
619 unsigned int sg_flags = SG_MITER_ATOMIC;
620
621 if (to_buffer)
622 sg_flags |= SG_MITER_FROM_SG;
623 else
624 sg_flags |= SG_MITER_TO_SG;
625
626 sg_miter_start(&miter, sgl, nents, sg_flags);
627
628 if (!sg_miter_skip(&miter, skip))
629 return false;
630
631 local_irq_save(flags);
632
633 while (sg_miter_next(&miter) && offset < buflen) {
634 unsigned int len;
635
636 len = min(miter.length, buflen - offset);
637
638 if (to_buffer)
639 memcpy(buf + offset, miter.addr, len);
640 else
641 memcpy(miter.addr, buf + offset, len);
642
643 offset += len;
644 }
645
646 sg_miter_stop(&miter);
647
648 local_irq_restore(flags);
649 return offset;
650}
651
652/**
653 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
654 * @sgl: The SG list
655 * @nents: Number of SG entries
656 * @buf: Where to copy from
657 * @buflen: The number of bytes to copy
658 *
659 * Returns the number of copied bytes.
660 *
661 **/
662size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
663 void *buf, size_t buflen)
664{
665 return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
666}
667EXPORT_SYMBOL(sg_copy_from_buffer);
668
669/**
670 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
671 * @sgl: The SG list
672 * @nents: Number of SG entries
673 * @buf: Where to copy to
674 * @buflen: The number of bytes to copy
675 *
676 * Returns the number of copied bytes.
677 *
678 **/
679size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
680 void *buf, size_t buflen)
681{
682 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
683}
684EXPORT_SYMBOL(sg_copy_to_buffer);
685
686/**
687 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
688 * @sgl: The SG list
689 * @nents: Number of SG entries
690 * @buf: Where to copy from
691 * @skip: Number of bytes to skip before copying
692 * @buflen: The number of bytes to copy
693 *
694 * Returns the number of copied bytes.
695 *
696 **/
697size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
698 void *buf, size_t buflen, off_t skip)
699{
700 return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
701}
702EXPORT_SYMBOL(sg_pcopy_from_buffer);
703
704/**
705 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
706 * @sgl: The SG list
707 * @nents: Number of SG entries
708 * @buf: Where to copy to
709 * @skip: Number of bytes to skip before copying
710 * @buflen: The number of bytes to copy
711 *
712 * Returns the number of copied bytes.
713 *
714 **/
715size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
716 void *buf, size_t buflen, off_t skip)
717{
718 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
719}
720EXPORT_SYMBOL(sg_pcopy_to_buffer);
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 **/
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_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{
52 int nents;
53 for (nents = 0; sg; sg = sg_next(sg))
54 nents++;
55 return nents;
56}
57EXPORT_SYMBOL(sg_nents);
58
59/**
60 * sg_nents_for_len - return total count of entries in scatterlist
61 * needed to satisfy the supplied length
62 * @sg: The scatterlist
63 * @len: The total required length
64 *
65 * Description:
66 * Determines the number of entries in sg that are required to meet
67 * the supplied length, taking into acount chaining as well
68 *
69 * Returns:
70 * the number of sg entries needed, negative error on failure
71 *
72 **/
73int sg_nents_for_len(struct scatterlist *sg, u64 len)
74{
75 int nents;
76 u64 total;
77
78 if (!len)
79 return 0;
80
81 for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
82 nents++;
83 total += sg->length;
84 if (total >= len)
85 return nents;
86 }
87
88 return -EINVAL;
89}
90EXPORT_SYMBOL(sg_nents_for_len);
91
92/**
93 * sg_last - return the last scatterlist entry in a list
94 * @sgl: First entry in the scatterlist
95 * @nents: Number of entries in the scatterlist
96 *
97 * Description:
98 * Should only be used casually, it (currently) scans the entire list
99 * to get the last entry.
100 *
101 * Note that the @sgl@ pointer passed in need not be the first one,
102 * the important bit is that @nents@ denotes the number of entries that
103 * exist from @sgl@.
104 *
105 **/
106struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
107{
108 struct scatterlist *sg, *ret = NULL;
109 unsigned int i;
110
111 for_each_sg(sgl, sg, nents, i)
112 ret = sg;
113
114#ifdef CONFIG_DEBUG_SG
115 BUG_ON(sgl[0].sg_magic != SG_MAGIC);
116 BUG_ON(!sg_is_last(ret));
117#endif
118 return ret;
119}
120EXPORT_SYMBOL(sg_last);
121
122/**
123 * sg_init_table - Initialize SG table
124 * @sgl: The SG table
125 * @nents: Number of entries in table
126 *
127 * Notes:
128 * If this is part of a chained sg table, sg_mark_end() should be
129 * used only on the last table part.
130 *
131 **/
132void sg_init_table(struct scatterlist *sgl, unsigned int nents)
133{
134 memset(sgl, 0, sizeof(*sgl) * nents);
135 sg_init_marker(sgl, nents);
136}
137EXPORT_SYMBOL(sg_init_table);
138
139/**
140 * sg_init_one - Initialize a single entry sg list
141 * @sg: SG entry
142 * @buf: Virtual address for IO
143 * @buflen: IO length
144 *
145 **/
146void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
147{
148 sg_init_table(sg, 1);
149 sg_set_buf(sg, buf, buflen);
150}
151EXPORT_SYMBOL(sg_init_one);
152
153/*
154 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
155 * helpers.
156 */
157static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
158{
159 if (nents == SG_MAX_SINGLE_ALLOC) {
160 /*
161 * Kmemleak doesn't track page allocations as they are not
162 * commonly used (in a raw form) for kernel data structures.
163 * As we chain together a list of pages and then a normal
164 * kmalloc (tracked by kmemleak), in order to for that last
165 * allocation not to become decoupled (and thus a
166 * false-positive) we need to inform kmemleak of all the
167 * intermediate allocations.
168 */
169 void *ptr = (void *) __get_free_page(gfp_mask);
170 kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
171 return ptr;
172 } else
173 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
174}
175
176static void sg_kfree(struct scatterlist *sg, unsigned int nents)
177{
178 if (nents == SG_MAX_SINGLE_ALLOC) {
179 kmemleak_free(sg);
180 free_page((unsigned long) sg);
181 } else
182 kfree(sg);
183}
184
185/**
186 * __sg_free_table - Free a previously mapped sg table
187 * @table: The sg table header to use
188 * @max_ents: The maximum number of entries per single scatterlist
189 * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk
190 * @free_fn: Free function
191 *
192 * Description:
193 * Free an sg table previously allocated and setup with
194 * __sg_alloc_table(). The @max_ents value must be identical to
195 * that previously used with __sg_alloc_table().
196 *
197 **/
198void __sg_free_table(struct sg_table *table, unsigned int max_ents,
199 bool skip_first_chunk, sg_free_fn *free_fn)
200{
201 struct scatterlist *sgl, *next;
202
203 if (unlikely(!table->sgl))
204 return;
205
206 sgl = table->sgl;
207 while (table->orig_nents) {
208 unsigned int alloc_size = table->orig_nents;
209 unsigned int sg_size;
210
211 /*
212 * If we have more than max_ents segments left,
213 * then assign 'next' to the sg table after the current one.
214 * sg_size is then one less than alloc size, since the last
215 * element is the chain pointer.
216 */
217 if (alloc_size > max_ents) {
218 next = sg_chain_ptr(&sgl[max_ents - 1]);
219 alloc_size = max_ents;
220 sg_size = alloc_size - 1;
221 } else {
222 sg_size = alloc_size;
223 next = NULL;
224 }
225
226 table->orig_nents -= sg_size;
227 if (skip_first_chunk)
228 skip_first_chunk = false;
229 else
230 free_fn(sgl, alloc_size);
231 sgl = next;
232 }
233
234 table->sgl = NULL;
235}
236EXPORT_SYMBOL(__sg_free_table);
237
238/**
239 * sg_free_table - Free a previously allocated sg table
240 * @table: The mapped sg table header
241 *
242 **/
243void sg_free_table(struct sg_table *table)
244{
245 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
246}
247EXPORT_SYMBOL(sg_free_table);
248
249/**
250 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
251 * @table: The sg table header to use
252 * @nents: Number of entries in sg list
253 * @max_ents: The maximum number of entries the allocator returns per call
254 * @gfp_mask: GFP allocation mask
255 * @alloc_fn: Allocator to use
256 *
257 * Description:
258 * This function returns a @table @nents long. The allocator is
259 * defined to return scatterlist chunks of maximum size @max_ents.
260 * Thus if @nents is bigger than @max_ents, the scatterlists will be
261 * chained in units of @max_ents.
262 *
263 * Notes:
264 * If this function returns non-0 (eg failure), the caller must call
265 * __sg_free_table() to cleanup any leftover allocations.
266 *
267 **/
268int __sg_alloc_table(struct sg_table *table, unsigned int nents,
269 unsigned int max_ents, struct scatterlist *first_chunk,
270 gfp_t gfp_mask, sg_alloc_fn *alloc_fn)
271{
272 struct scatterlist *sg, *prv;
273 unsigned int left;
274
275 memset(table, 0, sizeof(*table));
276
277 if (nents == 0)
278 return -EINVAL;
279#ifndef CONFIG_ARCH_HAS_SG_CHAIN
280 if (WARN_ON_ONCE(nents > max_ents))
281 return -EINVAL;
282#endif
283
284 left = nents;
285 prv = NULL;
286 do {
287 unsigned int sg_size, alloc_size = left;
288
289 if (alloc_size > max_ents) {
290 alloc_size = max_ents;
291 sg_size = alloc_size - 1;
292 } else
293 sg_size = alloc_size;
294
295 left -= sg_size;
296
297 if (first_chunk) {
298 sg = first_chunk;
299 first_chunk = NULL;
300 } else {
301 sg = alloc_fn(alloc_size, gfp_mask);
302 }
303 if (unlikely(!sg)) {
304 /*
305 * Adjust entry count to reflect that the last
306 * entry of the previous table won't be used for
307 * linkage. Without this, sg_kfree() may get
308 * confused.
309 */
310 if (prv)
311 table->nents = ++table->orig_nents;
312
313 return -ENOMEM;
314 }
315
316 sg_init_table(sg, alloc_size);
317 table->nents = table->orig_nents += sg_size;
318
319 /*
320 * If this is the first mapping, assign the sg table header.
321 * If this is not the first mapping, chain previous part.
322 */
323 if (prv)
324 sg_chain(prv, max_ents, sg);
325 else
326 table->sgl = sg;
327
328 /*
329 * If no more entries after this one, mark the end
330 */
331 if (!left)
332 sg_mark_end(&sg[sg_size - 1]);
333
334 prv = sg;
335 } while (left);
336
337 return 0;
338}
339EXPORT_SYMBOL(__sg_alloc_table);
340
341/**
342 * sg_alloc_table - Allocate and initialize an sg table
343 * @table: The sg table header to use
344 * @nents: Number of entries in sg list
345 * @gfp_mask: GFP allocation mask
346 *
347 * Description:
348 * Allocate and initialize an sg table. If @nents@ is larger than
349 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
350 *
351 **/
352int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
353{
354 int ret;
355
356 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
357 NULL, gfp_mask, sg_kmalloc);
358 if (unlikely(ret))
359 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree);
360
361 return ret;
362}
363EXPORT_SYMBOL(sg_alloc_table);
364
365/**
366 * __sg_alloc_table_from_pages - Allocate and initialize an sg table from
367 * an array of pages
368 * @sgt: The sg table header to use
369 * @pages: Pointer to an array of page pointers
370 * @n_pages: Number of pages in the pages array
371 * @offset: Offset from start of the first page to the start of a buffer
372 * @size: Number of valid bytes in the buffer (after offset)
373 * @max_segment: Maximum size of a scatterlist node in bytes (page aligned)
374 * @gfp_mask: GFP allocation mask
375 *
376 * Description:
377 * Allocate and initialize an sg table from a list of pages. Contiguous
378 * ranges of the pages are squashed into a single scatterlist node up to the
379 * maximum size specified in @max_segment. An user may provide an offset at a
380 * start and a size of valid data in a buffer specified by the page array.
381 * The returned sg table is released by sg_free_table.
382 *
383 * Returns:
384 * 0 on success, negative error on failure
385 */
386int __sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
387 unsigned int n_pages, unsigned int offset,
388 unsigned long size, unsigned int max_segment,
389 gfp_t gfp_mask)
390{
391 unsigned int chunks, cur_page, seg_len, i;
392 int ret;
393 struct scatterlist *s;
394
395 if (WARN_ON(!max_segment || offset_in_page(max_segment)))
396 return -EINVAL;
397
398 /* compute number of contiguous chunks */
399 chunks = 1;
400 seg_len = 0;
401 for (i = 1; i < n_pages; i++) {
402 seg_len += PAGE_SIZE;
403 if (seg_len >= max_segment ||
404 page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) {
405 chunks++;
406 seg_len = 0;
407 }
408 }
409
410 ret = sg_alloc_table(sgt, chunks, gfp_mask);
411 if (unlikely(ret))
412 return ret;
413
414 /* merging chunks and putting them into the scatterlist */
415 cur_page = 0;
416 for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
417 unsigned int j, chunk_size;
418
419 /* look for the end of the current chunk */
420 seg_len = 0;
421 for (j = cur_page + 1; j < n_pages; j++) {
422 seg_len += PAGE_SIZE;
423 if (seg_len >= max_segment ||
424 page_to_pfn(pages[j]) !=
425 page_to_pfn(pages[j - 1]) + 1)
426 break;
427 }
428
429 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
430 sg_set_page(s, pages[cur_page],
431 min_t(unsigned long, size, chunk_size), offset);
432 size -= chunk_size;
433 offset = 0;
434 cur_page = j;
435 }
436
437 return 0;
438}
439EXPORT_SYMBOL(__sg_alloc_table_from_pages);
440
441/**
442 * sg_alloc_table_from_pages - Allocate and initialize an sg table from
443 * an array of pages
444 * @sgt: The sg table header to use
445 * @pages: Pointer to an array of page pointers
446 * @n_pages: Number of pages in the pages array
447 * @offset: Offset from start of the first page to the start of a buffer
448 * @size: Number of valid bytes in the buffer (after offset)
449 * @gfp_mask: GFP allocation mask
450 *
451 * Description:
452 * Allocate and initialize an sg table from a list of pages. Contiguous
453 * ranges of the pages are squashed into a single scatterlist node. A user
454 * may provide an offset at a start and a size of valid data in a buffer
455 * specified by the page array. The returned sg table is released by
456 * sg_free_table.
457 *
458 * Returns:
459 * 0 on success, negative error on failure
460 */
461int sg_alloc_table_from_pages(struct sg_table *sgt, struct page **pages,
462 unsigned int n_pages, unsigned int offset,
463 unsigned long size, gfp_t gfp_mask)
464{
465 return __sg_alloc_table_from_pages(sgt, pages, n_pages, offset, size,
466 SCATTERLIST_MAX_SEGMENT, gfp_mask);
467}
468EXPORT_SYMBOL(sg_alloc_table_from_pages);
469
470#ifdef CONFIG_SGL_ALLOC
471
472/**
473 * sgl_alloc_order - allocate a scatterlist and its pages
474 * @length: Length in bytes of the scatterlist. Must be at least one
475 * @order: Second argument for alloc_pages()
476 * @chainable: Whether or not to allocate an extra element in the scatterlist
477 * for scatterlist chaining purposes
478 * @gfp: Memory allocation flags
479 * @nent_p: [out] Number of entries in the scatterlist that have pages
480 *
481 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
482 */
483struct scatterlist *sgl_alloc_order(unsigned long long length,
484 unsigned int order, bool chainable,
485 gfp_t gfp, unsigned int *nent_p)
486{
487 struct scatterlist *sgl, *sg;
488 struct page *page;
489 unsigned int nent, nalloc;
490 u32 elem_len;
491
492 nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
493 /* Check for integer overflow */
494 if (length > (nent << (PAGE_SHIFT + order)))
495 return NULL;
496 nalloc = nent;
497 if (chainable) {
498 /* Check for integer overflow */
499 if (nalloc + 1 < nalloc)
500 return NULL;
501 nalloc++;
502 }
503 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
504 (gfp & ~GFP_DMA) | __GFP_ZERO);
505 if (!sgl)
506 return NULL;
507
508 sg_init_table(sgl, nalloc);
509 sg = sgl;
510 while (length) {
511 elem_len = min_t(u64, length, PAGE_SIZE << order);
512 page = alloc_pages(gfp, order);
513 if (!page) {
514 sgl_free(sgl);
515 return NULL;
516 }
517
518 sg_set_page(sg, page, elem_len, 0);
519 length -= elem_len;
520 sg = sg_next(sg);
521 }
522 WARN_ONCE(length, "length = %lld\n", length);
523 if (nent_p)
524 *nent_p = nent;
525 return sgl;
526}
527EXPORT_SYMBOL(sgl_alloc_order);
528
529/**
530 * sgl_alloc - allocate a scatterlist and its pages
531 * @length: Length in bytes of the scatterlist
532 * @gfp: Memory allocation flags
533 * @nent_p: [out] Number of entries in the scatterlist
534 *
535 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
536 */
537struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
538 unsigned int *nent_p)
539{
540 return sgl_alloc_order(length, 0, false, gfp, nent_p);
541}
542EXPORT_SYMBOL(sgl_alloc);
543
544/**
545 * sgl_free_n_order - free a scatterlist and its pages
546 * @sgl: Scatterlist with one or more elements
547 * @nents: Maximum number of elements to free
548 * @order: Second argument for __free_pages()
549 *
550 * Notes:
551 * - If several scatterlists have been chained and each chain element is
552 * freed separately then it's essential to set nents correctly to avoid that a
553 * page would get freed twice.
554 * - All pages in a chained scatterlist can be freed at once by setting @nents
555 * to a high number.
556 */
557void sgl_free_n_order(struct scatterlist *sgl, int nents, int order)
558{
559 struct scatterlist *sg;
560 struct page *page;
561 int i;
562
563 for_each_sg(sgl, sg, nents, i) {
564 if (!sg)
565 break;
566 page = sg_page(sg);
567 if (page)
568 __free_pages(page, order);
569 }
570 kfree(sgl);
571}
572EXPORT_SYMBOL(sgl_free_n_order);
573
574/**
575 * sgl_free_order - free a scatterlist and its pages
576 * @sgl: Scatterlist with one or more elements
577 * @order: Second argument for __free_pages()
578 */
579void sgl_free_order(struct scatterlist *sgl, int order)
580{
581 sgl_free_n_order(sgl, INT_MAX, order);
582}
583EXPORT_SYMBOL(sgl_free_order);
584
585/**
586 * sgl_free - free a scatterlist and its pages
587 * @sgl: Scatterlist with one or more elements
588 */
589void sgl_free(struct scatterlist *sgl)
590{
591 sgl_free_order(sgl, 0);
592}
593EXPORT_SYMBOL(sgl_free);
594
595#endif /* CONFIG_SGL_ALLOC */
596
597void __sg_page_iter_start(struct sg_page_iter *piter,
598 struct scatterlist *sglist, unsigned int nents,
599 unsigned long pgoffset)
600{
601 piter->__pg_advance = 0;
602 piter->__nents = nents;
603
604 piter->sg = sglist;
605 piter->sg_pgoffset = pgoffset;
606}
607EXPORT_SYMBOL(__sg_page_iter_start);
608
609static int sg_page_count(struct scatterlist *sg)
610{
611 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
612}
613
614bool __sg_page_iter_next(struct sg_page_iter *piter)
615{
616 if (!piter->__nents || !piter->sg)
617 return false;
618
619 piter->sg_pgoffset += piter->__pg_advance;
620 piter->__pg_advance = 1;
621
622 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
623 piter->sg_pgoffset -= sg_page_count(piter->sg);
624 piter->sg = sg_next(piter->sg);
625 if (!--piter->__nents || !piter->sg)
626 return false;
627 }
628
629 return true;
630}
631EXPORT_SYMBOL(__sg_page_iter_next);
632
633/**
634 * sg_miter_start - start mapping iteration over a sg list
635 * @miter: sg mapping iter to be started
636 * @sgl: sg list to iterate over
637 * @nents: number of sg entries
638 *
639 * Description:
640 * Starts mapping iterator @miter.
641 *
642 * Context:
643 * Don't care.
644 */
645void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
646 unsigned int nents, unsigned int flags)
647{
648 memset(miter, 0, sizeof(struct sg_mapping_iter));
649
650 __sg_page_iter_start(&miter->piter, sgl, nents, 0);
651 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
652 miter->__flags = flags;
653}
654EXPORT_SYMBOL(sg_miter_start);
655
656static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
657{
658 if (!miter->__remaining) {
659 struct scatterlist *sg;
660 unsigned long pgoffset;
661
662 if (!__sg_page_iter_next(&miter->piter))
663 return false;
664
665 sg = miter->piter.sg;
666 pgoffset = miter->piter.sg_pgoffset;
667
668 miter->__offset = pgoffset ? 0 : sg->offset;
669 miter->__remaining = sg->offset + sg->length -
670 (pgoffset << PAGE_SHIFT) - miter->__offset;
671 miter->__remaining = min_t(unsigned long, miter->__remaining,
672 PAGE_SIZE - miter->__offset);
673 }
674
675 return true;
676}
677
678/**
679 * sg_miter_skip - reposition mapping iterator
680 * @miter: sg mapping iter to be skipped
681 * @offset: number of bytes to plus the current location
682 *
683 * Description:
684 * Sets the offset of @miter to its current location plus @offset bytes.
685 * If mapping iterator @miter has been proceeded by sg_miter_next(), this
686 * stops @miter.
687 *
688 * Context:
689 * Don't care if @miter is stopped, or not proceeded yet.
690 * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
691 *
692 * Returns:
693 * true if @miter contains the valid mapping. false if end of sg
694 * list is reached.
695 */
696bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
697{
698 sg_miter_stop(miter);
699
700 while (offset) {
701 off_t consumed;
702
703 if (!sg_miter_get_next_page(miter))
704 return false;
705
706 consumed = min_t(off_t, offset, miter->__remaining);
707 miter->__offset += consumed;
708 miter->__remaining -= consumed;
709 offset -= consumed;
710 }
711
712 return true;
713}
714EXPORT_SYMBOL(sg_miter_skip);
715
716/**
717 * sg_miter_next - proceed mapping iterator to the next mapping
718 * @miter: sg mapping iter to proceed
719 *
720 * Description:
721 * Proceeds @miter to the next mapping. @miter should have been started
722 * using sg_miter_start(). On successful return, @miter->page,
723 * @miter->addr and @miter->length point to the current mapping.
724 *
725 * Context:
726 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
727 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
728 *
729 * Returns:
730 * true if @miter contains the next mapping. false if end of sg
731 * list is reached.
732 */
733bool sg_miter_next(struct sg_mapping_iter *miter)
734{
735 sg_miter_stop(miter);
736
737 /*
738 * Get to the next page if necessary.
739 * __remaining, __offset is adjusted by sg_miter_stop
740 */
741 if (!sg_miter_get_next_page(miter))
742 return false;
743
744 miter->page = sg_page_iter_page(&miter->piter);
745 miter->consumed = miter->length = miter->__remaining;
746
747 if (miter->__flags & SG_MITER_ATOMIC)
748 miter->addr = kmap_atomic(miter->page) + miter->__offset;
749 else
750 miter->addr = kmap(miter->page) + miter->__offset;
751
752 return true;
753}
754EXPORT_SYMBOL(sg_miter_next);
755
756/**
757 * sg_miter_stop - stop mapping iteration
758 * @miter: sg mapping iter to be stopped
759 *
760 * Description:
761 * Stops mapping iterator @miter. @miter should have been started
762 * using sg_miter_start(). A stopped iteration can be resumed by
763 * calling sg_miter_next() on it. This is useful when resources (kmap)
764 * need to be released during iteration.
765 *
766 * Context:
767 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
768 * otherwise.
769 */
770void sg_miter_stop(struct sg_mapping_iter *miter)
771{
772 WARN_ON(miter->consumed > miter->length);
773
774 /* drop resources from the last iteration */
775 if (miter->addr) {
776 miter->__offset += miter->consumed;
777 miter->__remaining -= miter->consumed;
778
779 if ((miter->__flags & SG_MITER_TO_SG) &&
780 !PageSlab(miter->page))
781 flush_kernel_dcache_page(miter->page);
782
783 if (miter->__flags & SG_MITER_ATOMIC) {
784 WARN_ON_ONCE(preemptible());
785 kunmap_atomic(miter->addr);
786 } else
787 kunmap(miter->page);
788
789 miter->page = NULL;
790 miter->addr = NULL;
791 miter->length = 0;
792 miter->consumed = 0;
793 }
794}
795EXPORT_SYMBOL(sg_miter_stop);
796
797/**
798 * sg_copy_buffer - Copy data between a linear buffer and an SG list
799 * @sgl: The SG list
800 * @nents: Number of SG entries
801 * @buf: Where to copy from
802 * @buflen: The number of bytes to copy
803 * @skip: Number of bytes to skip before copying
804 * @to_buffer: transfer direction (true == from an sg list to a
805 * buffer, false == from a buffer to an sg list
806 *
807 * Returns the number of copied bytes.
808 *
809 **/
810size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
811 size_t buflen, off_t skip, bool to_buffer)
812{
813 unsigned int offset = 0;
814 struct sg_mapping_iter miter;
815 unsigned int sg_flags = SG_MITER_ATOMIC;
816
817 if (to_buffer)
818 sg_flags |= SG_MITER_FROM_SG;
819 else
820 sg_flags |= SG_MITER_TO_SG;
821
822 sg_miter_start(&miter, sgl, nents, sg_flags);
823
824 if (!sg_miter_skip(&miter, skip))
825 return false;
826
827 while ((offset < buflen) && sg_miter_next(&miter)) {
828 unsigned int len;
829
830 len = min(miter.length, buflen - offset);
831
832 if (to_buffer)
833 memcpy(buf + offset, miter.addr, len);
834 else
835 memcpy(miter.addr, buf + offset, len);
836
837 offset += len;
838 }
839
840 sg_miter_stop(&miter);
841
842 return offset;
843}
844EXPORT_SYMBOL(sg_copy_buffer);
845
846/**
847 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
848 * @sgl: The SG list
849 * @nents: Number of SG entries
850 * @buf: Where to copy from
851 * @buflen: The number of bytes to copy
852 *
853 * Returns the number of copied bytes.
854 *
855 **/
856size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
857 const void *buf, size_t buflen)
858{
859 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
860}
861EXPORT_SYMBOL(sg_copy_from_buffer);
862
863/**
864 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
865 * @sgl: The SG list
866 * @nents: Number of SG entries
867 * @buf: Where to copy to
868 * @buflen: The number of bytes to copy
869 *
870 * Returns the number of copied bytes.
871 *
872 **/
873size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
874 void *buf, size_t buflen)
875{
876 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
877}
878EXPORT_SYMBOL(sg_copy_to_buffer);
879
880/**
881 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
882 * @sgl: The SG list
883 * @nents: Number of SG entries
884 * @buf: Where to copy from
885 * @buflen: The number of bytes to copy
886 * @skip: Number of bytes to skip before copying
887 *
888 * Returns the number of copied bytes.
889 *
890 **/
891size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
892 const void *buf, size_t buflen, off_t skip)
893{
894 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false);
895}
896EXPORT_SYMBOL(sg_pcopy_from_buffer);
897
898/**
899 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
900 * @sgl: The SG list
901 * @nents: Number of SG entries
902 * @buf: Where to copy to
903 * @buflen: The number of bytes to copy
904 * @skip: Number of bytes to skip before copying
905 *
906 * Returns the number of copied bytes.
907 *
908 **/
909size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
910 void *buf, size_t buflen, off_t skip)
911{
912 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
913}
914EXPORT_SYMBOL(sg_pcopy_to_buffer);
915
916/**
917 * sg_zero_buffer - Zero-out a part of a SG list
918 * @sgl: The SG list
919 * @nents: Number of SG entries
920 * @buflen: The number of bytes to zero out
921 * @skip: Number of bytes to skip before zeroing
922 *
923 * Returns the number of bytes zeroed.
924 **/
925size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
926 size_t buflen, off_t skip)
927{
928 unsigned int offset = 0;
929 struct sg_mapping_iter miter;
930 unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
931
932 sg_miter_start(&miter, sgl, nents, sg_flags);
933
934 if (!sg_miter_skip(&miter, skip))
935 return false;
936
937 while (offset < buflen && sg_miter_next(&miter)) {
938 unsigned int len;
939
940 len = min(miter.length, buflen - offset);
941 memset(miter.addr, 0, len);
942
943 offset += len;
944 }
945
946 sg_miter_stop(&miter);
947 return offset;
948}
949EXPORT_SYMBOL(sg_zero_buffer);