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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// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
4 *
5 * Scatterlist handling helpers.
6 */
7#include <linux/export.h>
8#include <linux/slab.h>
9#include <linux/scatterlist.h>
10#include <linux/highmem.h>
11#include <linux/kmemleak.h>
12
13/**
14 * sg_next - return the next scatterlist entry in a list
15 * @sg: The current sg entry
16 *
17 * Description:
18 * Usually the next entry will be @sg@ + 1, but if this sg element is part
19 * of a chained scatterlist, it could jump to the start of a new
20 * scatterlist array.
21 *
22 **/
23struct scatterlist *sg_next(struct scatterlist *sg)
24{
25 if (sg_is_last(sg))
26 return NULL;
27
28 sg++;
29 if (unlikely(sg_is_chain(sg)))
30 sg = sg_chain_ptr(sg);
31
32 return sg;
33}
34EXPORT_SYMBOL(sg_next);
35
36/**
37 * sg_nents - return total count of entries in scatterlist
38 * @sg: The scatterlist
39 *
40 * Description:
41 * Allows to know how many entries are in sg, taking into account
42 * chaining as well
43 *
44 **/
45int sg_nents(struct scatterlist *sg)
46{
47 int nents;
48 for (nents = 0; sg; sg = sg_next(sg))
49 nents++;
50 return nents;
51}
52EXPORT_SYMBOL(sg_nents);
53
54/**
55 * sg_nents_for_len - return total count of entries in scatterlist
56 * needed to satisfy the supplied length
57 * @sg: The scatterlist
58 * @len: The total required length
59 *
60 * Description:
61 * Determines the number of entries in sg that are required to meet
62 * the supplied length, taking into account chaining as well
63 *
64 * Returns:
65 * the number of sg entries needed, negative error on failure
66 *
67 **/
68int sg_nents_for_len(struct scatterlist *sg, u64 len)
69{
70 int nents;
71 u64 total;
72
73 if (!len)
74 return 0;
75
76 for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
77 nents++;
78 total += sg->length;
79 if (total >= len)
80 return nents;
81 }
82
83 return -EINVAL;
84}
85EXPORT_SYMBOL(sg_nents_for_len);
86
87/**
88 * sg_last - return the last scatterlist entry in a list
89 * @sgl: First entry in the scatterlist
90 * @nents: Number of entries in the scatterlist
91 *
92 * Description:
93 * Should only be used casually, it (currently) scans the entire list
94 * to get the last entry.
95 *
96 * Note that the @sgl@ pointer passed in need not be the first one,
97 * the important bit is that @nents@ denotes the number of entries that
98 * exist from @sgl@.
99 *
100 **/
101struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
102{
103 struct scatterlist *sg, *ret = NULL;
104 unsigned int i;
105
106 for_each_sg(sgl, sg, nents, i)
107 ret = sg;
108
109 BUG_ON(!sg_is_last(ret));
110 return ret;
111}
112EXPORT_SYMBOL(sg_last);
113
114/**
115 * sg_init_table - Initialize SG table
116 * @sgl: The SG table
117 * @nents: Number of entries in table
118 *
119 * Notes:
120 * If this is part of a chained sg table, sg_mark_end() should be
121 * used only on the last table part.
122 *
123 **/
124void sg_init_table(struct scatterlist *sgl, unsigned int nents)
125{
126 memset(sgl, 0, sizeof(*sgl) * nents);
127 sg_init_marker(sgl, nents);
128}
129EXPORT_SYMBOL(sg_init_table);
130
131/**
132 * sg_init_one - Initialize a single entry sg list
133 * @sg: SG entry
134 * @buf: Virtual address for IO
135 * @buflen: IO length
136 *
137 **/
138void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
139{
140 sg_init_table(sg, 1);
141 sg_set_buf(sg, buf, buflen);
142}
143EXPORT_SYMBOL(sg_init_one);
144
145/*
146 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
147 * helpers.
148 */
149static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
150{
151 if (nents == SG_MAX_SINGLE_ALLOC) {
152 /*
153 * Kmemleak doesn't track page allocations as they are not
154 * commonly used (in a raw form) for kernel data structures.
155 * As we chain together a list of pages and then a normal
156 * kmalloc (tracked by kmemleak), in order to for that last
157 * allocation not to become decoupled (and thus a
158 * false-positive) we need to inform kmemleak of all the
159 * intermediate allocations.
160 */
161 void *ptr = (void *) __get_free_page(gfp_mask);
162 kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
163 return ptr;
164 } else
165 return kmalloc_array(nents, sizeof(struct scatterlist),
166 gfp_mask);
167}
168
169static void sg_kfree(struct scatterlist *sg, unsigned int nents)
170{
171 if (nents == SG_MAX_SINGLE_ALLOC) {
172 kmemleak_free(sg);
173 free_page((unsigned long) sg);
174 } else
175 kfree(sg);
176}
177
178/**
179 * __sg_free_table - Free a previously mapped sg table
180 * @table: The sg table header to use
181 * @max_ents: The maximum number of entries per single scatterlist
182 * @nents_first_chunk: Number of entries int the (preallocated) first
183 * scatterlist chunk, 0 means no such preallocated first chunk
184 * @free_fn: Free function
185 * @num_ents: Number of entries in the table
186 *
187 * Description:
188 * Free an sg table previously allocated and setup with
189 * __sg_alloc_table(). The @max_ents value must be identical to
190 * that previously used with __sg_alloc_table().
191 *
192 **/
193void __sg_free_table(struct sg_table *table, unsigned int max_ents,
194 unsigned int nents_first_chunk, sg_free_fn *free_fn,
195 unsigned int num_ents)
196{
197 struct scatterlist *sgl, *next;
198 unsigned curr_max_ents = nents_first_chunk ?: max_ents;
199
200 if (unlikely(!table->sgl))
201 return;
202
203 sgl = table->sgl;
204 while (num_ents) {
205 unsigned int alloc_size = num_ents;
206 unsigned int sg_size;
207
208 /*
209 * If we have more than max_ents segments left,
210 * then assign 'next' to the sg table after the current one.
211 * sg_size is then one less than alloc size, since the last
212 * element is the chain pointer.
213 */
214 if (alloc_size > curr_max_ents) {
215 next = sg_chain_ptr(&sgl[curr_max_ents - 1]);
216 alloc_size = curr_max_ents;
217 sg_size = alloc_size - 1;
218 } else {
219 sg_size = alloc_size;
220 next = NULL;
221 }
222
223 num_ents -= sg_size;
224 if (nents_first_chunk)
225 nents_first_chunk = 0;
226 else
227 free_fn(sgl, alloc_size);
228 sgl = next;
229 curr_max_ents = max_ents;
230 }
231
232 table->sgl = NULL;
233}
234EXPORT_SYMBOL(__sg_free_table);
235
236/**
237 * sg_free_append_table - Free a previously allocated append sg table.
238 * @table: The mapped sg append table header
239 *
240 **/
241void sg_free_append_table(struct sg_append_table *table)
242{
243 __sg_free_table(&table->sgt, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
244 table->total_nents);
245}
246EXPORT_SYMBOL(sg_free_append_table);
247
248
249/**
250 * sg_free_table - Free a previously allocated sg table
251 * @table: The mapped sg table header
252 *
253 **/
254void sg_free_table(struct sg_table *table)
255{
256 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
257 table->orig_nents);
258}
259EXPORT_SYMBOL(sg_free_table);
260
261/**
262 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
263 * @table: The sg table header to use
264 * @nents: Number of entries in sg list
265 * @max_ents: The maximum number of entries the allocator returns per call
266 * @nents_first_chunk: Number of entries int the (preallocated) first
267 * scatterlist chunk, 0 means no such preallocated chunk provided by user
268 * @gfp_mask: GFP allocation mask
269 * @alloc_fn: Allocator to use
270 *
271 * Description:
272 * This function returns a @table @nents long. The allocator is
273 * defined to return scatterlist chunks of maximum size @max_ents.
274 * Thus if @nents is bigger than @max_ents, the scatterlists will be
275 * chained in units of @max_ents.
276 *
277 * Notes:
278 * If this function returns non-0 (eg failure), the caller must call
279 * __sg_free_table() to cleanup any leftover allocations.
280 *
281 **/
282int __sg_alloc_table(struct sg_table *table, unsigned int nents,
283 unsigned int max_ents, struct scatterlist *first_chunk,
284 unsigned int nents_first_chunk, gfp_t gfp_mask,
285 sg_alloc_fn *alloc_fn)
286{
287 struct scatterlist *sg, *prv;
288 unsigned int left;
289 unsigned curr_max_ents = nents_first_chunk ?: max_ents;
290 unsigned prv_max_ents;
291
292 memset(table, 0, sizeof(*table));
293
294 if (nents == 0)
295 return -EINVAL;
296#ifdef CONFIG_ARCH_NO_SG_CHAIN
297 if (WARN_ON_ONCE(nents > max_ents))
298 return -EINVAL;
299#endif
300
301 left = nents;
302 prv = NULL;
303 do {
304 unsigned int sg_size, alloc_size = left;
305
306 if (alloc_size > curr_max_ents) {
307 alloc_size = curr_max_ents;
308 sg_size = alloc_size - 1;
309 } else
310 sg_size = alloc_size;
311
312 left -= sg_size;
313
314 if (first_chunk) {
315 sg = first_chunk;
316 first_chunk = NULL;
317 } else {
318 sg = alloc_fn(alloc_size, gfp_mask);
319 }
320 if (unlikely(!sg)) {
321 /*
322 * Adjust entry count to reflect that the last
323 * entry of the previous table won't be used for
324 * linkage. Without this, sg_kfree() may get
325 * confused.
326 */
327 if (prv)
328 table->nents = ++table->orig_nents;
329
330 return -ENOMEM;
331 }
332
333 sg_init_table(sg, alloc_size);
334 table->nents = table->orig_nents += sg_size;
335
336 /*
337 * If this is the first mapping, assign the sg table header.
338 * If this is not the first mapping, chain previous part.
339 */
340 if (prv)
341 sg_chain(prv, prv_max_ents, sg);
342 else
343 table->sgl = sg;
344
345 /*
346 * If no more entries after this one, mark the end
347 */
348 if (!left)
349 sg_mark_end(&sg[sg_size - 1]);
350
351 prv = sg;
352 prv_max_ents = curr_max_ents;
353 curr_max_ents = max_ents;
354 } while (left);
355
356 return 0;
357}
358EXPORT_SYMBOL(__sg_alloc_table);
359
360/**
361 * sg_alloc_table - Allocate and initialize an sg table
362 * @table: The sg table header to use
363 * @nents: Number of entries in sg list
364 * @gfp_mask: GFP allocation mask
365 *
366 * Description:
367 * Allocate and initialize an sg table. If @nents@ is larger than
368 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
369 *
370 **/
371int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
372{
373 int ret;
374
375 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
376 NULL, 0, gfp_mask, sg_kmalloc);
377 if (unlikely(ret))
378 sg_free_table(table);
379 return ret;
380}
381EXPORT_SYMBOL(sg_alloc_table);
382
383static struct scatterlist *get_next_sg(struct sg_append_table *table,
384 struct scatterlist *cur,
385 unsigned long needed_sges,
386 gfp_t gfp_mask)
387{
388 struct scatterlist *new_sg, *next_sg;
389 unsigned int alloc_size;
390
391 if (cur) {
392 next_sg = sg_next(cur);
393 /* Check if last entry should be keeped for chainning */
394 if (!sg_is_last(next_sg) || needed_sges == 1)
395 return next_sg;
396 }
397
398 alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC);
399 new_sg = sg_kmalloc(alloc_size, gfp_mask);
400 if (!new_sg)
401 return ERR_PTR(-ENOMEM);
402 sg_init_table(new_sg, alloc_size);
403 if (cur) {
404 table->total_nents += alloc_size - 1;
405 __sg_chain(next_sg, new_sg);
406 } else {
407 table->sgt.sgl = new_sg;
408 table->total_nents = alloc_size;
409 }
410 return new_sg;
411}
412
413static bool pages_are_mergeable(struct page *a, struct page *b)
414{
415 if (page_to_pfn(a) != page_to_pfn(b) + 1)
416 return false;
417 if (!zone_device_pages_have_same_pgmap(a, b))
418 return false;
419 return true;
420}
421
422/**
423 * sg_alloc_append_table_from_pages - Allocate and initialize an append sg
424 * table from an array of pages
425 * @sgt_append: The sg append table to use
426 * @pages: Pointer to an array of page pointers
427 * @n_pages: Number of pages in the pages array
428 * @offset: Offset from start of the first page to the start of a buffer
429 * @size: Number of valid bytes in the buffer (after offset)
430 * @max_segment: Maximum size of a scatterlist element in bytes
431 * @left_pages: Left pages caller have to set after this call
432 * @gfp_mask: GFP allocation mask
433 *
434 * Description:
435 * In the first call it allocate and initialize an sg table from a list of
436 * pages, else reuse the scatterlist from sgt_append. Contiguous ranges of
437 * the pages are squashed into a single scatterlist entry up to the maximum
438 * size specified in @max_segment. A user may provide an offset at a start
439 * and a size of valid data in a buffer specified by the page array. The
440 * returned sg table is released by sg_free_append_table
441 *
442 * Returns:
443 * 0 on success, negative error on failure
444 *
445 * Notes:
446 * If this function returns non-0 (eg failure), the caller must call
447 * sg_free_append_table() to cleanup any leftover allocations.
448 *
449 * In the fist call, sgt_append must by initialized.
450 */
451int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append,
452 struct page **pages, unsigned int n_pages, unsigned int offset,
453 unsigned long size, unsigned int max_segment,
454 unsigned int left_pages, gfp_t gfp_mask)
455{
456 unsigned int chunks, cur_page, seg_len, i, prv_len = 0;
457 unsigned int added_nents = 0;
458 struct scatterlist *s = sgt_append->prv;
459 struct page *last_pg;
460
461 /*
462 * The algorithm below requires max_segment to be aligned to PAGE_SIZE
463 * otherwise it can overshoot.
464 */
465 max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE);
466 if (WARN_ON(max_segment < PAGE_SIZE))
467 return -EINVAL;
468
469 if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && sgt_append->prv)
470 return -EOPNOTSUPP;
471
472 if (sgt_append->prv) {
473 unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) +
474 sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE;
475
476 if (WARN_ON(offset))
477 return -EINVAL;
478
479 /* Merge contiguous pages into the last SG */
480 prv_len = sgt_append->prv->length;
481 if (page_to_pfn(pages[0]) == next_pfn) {
482 last_pg = pfn_to_page(next_pfn - 1);
483 while (n_pages && pages_are_mergeable(pages[0], last_pg)) {
484 if (sgt_append->prv->length + PAGE_SIZE > max_segment)
485 break;
486 sgt_append->prv->length += PAGE_SIZE;
487 last_pg = pages[0];
488 pages++;
489 n_pages--;
490 }
491 if (!n_pages)
492 goto out;
493 }
494 }
495
496 /* compute number of contiguous chunks */
497 chunks = 1;
498 seg_len = 0;
499 for (i = 1; i < n_pages; i++) {
500 seg_len += PAGE_SIZE;
501 if (seg_len >= max_segment ||
502 !pages_are_mergeable(pages[i], pages[i - 1])) {
503 chunks++;
504 seg_len = 0;
505 }
506 }
507
508 /* merging chunks and putting them into the scatterlist */
509 cur_page = 0;
510 for (i = 0; i < chunks; i++) {
511 unsigned int j, chunk_size;
512
513 /* look for the end of the current chunk */
514 seg_len = 0;
515 for (j = cur_page + 1; j < n_pages; j++) {
516 seg_len += PAGE_SIZE;
517 if (seg_len >= max_segment ||
518 !pages_are_mergeable(pages[j], pages[j - 1]))
519 break;
520 }
521
522 /* Pass how many chunks might be left */
523 s = get_next_sg(sgt_append, s, chunks - i + left_pages,
524 gfp_mask);
525 if (IS_ERR(s)) {
526 /*
527 * Adjust entry length to be as before function was
528 * called.
529 */
530 if (sgt_append->prv)
531 sgt_append->prv->length = prv_len;
532 return PTR_ERR(s);
533 }
534 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
535 sg_set_page(s, pages[cur_page],
536 min_t(unsigned long, size, chunk_size), offset);
537 added_nents++;
538 size -= chunk_size;
539 offset = 0;
540 cur_page = j;
541 }
542 sgt_append->sgt.nents += added_nents;
543 sgt_append->sgt.orig_nents = sgt_append->sgt.nents;
544 sgt_append->prv = s;
545out:
546 if (!left_pages)
547 sg_mark_end(s);
548 return 0;
549}
550EXPORT_SYMBOL(sg_alloc_append_table_from_pages);
551
552/**
553 * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from
554 * an array of pages and given maximum
555 * segment.
556 * @sgt: The sg table header to use
557 * @pages: Pointer to an array of page pointers
558 * @n_pages: Number of pages in the pages array
559 * @offset: Offset from start of the first page to the start of a buffer
560 * @size: Number of valid bytes in the buffer (after offset)
561 * @max_segment: Maximum size of a scatterlist element in bytes
562 * @gfp_mask: GFP allocation mask
563 *
564 * Description:
565 * Allocate and initialize an sg table from a list of pages. Contiguous
566 * ranges of the pages are squashed into a single scatterlist node up to the
567 * maximum size specified in @max_segment. A user may provide an offset at a
568 * start and a size of valid data in a buffer specified by the page array.
569 *
570 * The returned sg table is released by sg_free_table.
571 *
572 * Returns:
573 * 0 on success, negative error on failure
574 */
575int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages,
576 unsigned int n_pages, unsigned int offset,
577 unsigned long size, unsigned int max_segment,
578 gfp_t gfp_mask)
579{
580 struct sg_append_table append = {};
581 int err;
582
583 err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset,
584 size, max_segment, 0, gfp_mask);
585 if (err) {
586 sg_free_append_table(&append);
587 return err;
588 }
589 memcpy(sgt, &append.sgt, sizeof(*sgt));
590 WARN_ON(append.total_nents != sgt->orig_nents);
591 return 0;
592}
593EXPORT_SYMBOL(sg_alloc_table_from_pages_segment);
594
595#ifdef CONFIG_SGL_ALLOC
596
597/**
598 * sgl_alloc_order - allocate a scatterlist and its pages
599 * @length: Length in bytes of the scatterlist. Must be at least one
600 * @order: Second argument for alloc_pages()
601 * @chainable: Whether or not to allocate an extra element in the scatterlist
602 * for scatterlist chaining purposes
603 * @gfp: Memory allocation flags
604 * @nent_p: [out] Number of entries in the scatterlist that have pages
605 *
606 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
607 */
608struct scatterlist *sgl_alloc_order(unsigned long long length,
609 unsigned int order, bool chainable,
610 gfp_t gfp, unsigned int *nent_p)
611{
612 struct scatterlist *sgl, *sg;
613 struct page *page;
614 unsigned int nent, nalloc;
615 u32 elem_len;
616
617 nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
618 /* Check for integer overflow */
619 if (length > (nent << (PAGE_SHIFT + order)))
620 return NULL;
621 nalloc = nent;
622 if (chainable) {
623 /* Check for integer overflow */
624 if (nalloc + 1 < nalloc)
625 return NULL;
626 nalloc++;
627 }
628 sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
629 gfp & ~GFP_DMA);
630 if (!sgl)
631 return NULL;
632
633 sg_init_table(sgl, nalloc);
634 sg = sgl;
635 while (length) {
636 elem_len = min_t(u64, length, PAGE_SIZE << order);
637 page = alloc_pages(gfp, order);
638 if (!page) {
639 sgl_free_order(sgl, order);
640 return NULL;
641 }
642
643 sg_set_page(sg, page, elem_len, 0);
644 length -= elem_len;
645 sg = sg_next(sg);
646 }
647 WARN_ONCE(length, "length = %lld\n", length);
648 if (nent_p)
649 *nent_p = nent;
650 return sgl;
651}
652EXPORT_SYMBOL(sgl_alloc_order);
653
654/**
655 * sgl_alloc - allocate a scatterlist and its pages
656 * @length: Length in bytes of the scatterlist
657 * @gfp: Memory allocation flags
658 * @nent_p: [out] Number of entries in the scatterlist
659 *
660 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
661 */
662struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
663 unsigned int *nent_p)
664{
665 return sgl_alloc_order(length, 0, false, gfp, nent_p);
666}
667EXPORT_SYMBOL(sgl_alloc);
668
669/**
670 * sgl_free_n_order - free a scatterlist and its pages
671 * @sgl: Scatterlist with one or more elements
672 * @nents: Maximum number of elements to free
673 * @order: Second argument for __free_pages()
674 *
675 * Notes:
676 * - If several scatterlists have been chained and each chain element is
677 * freed separately then it's essential to set nents correctly to avoid that a
678 * page would get freed twice.
679 * - All pages in a chained scatterlist can be freed at once by setting @nents
680 * to a high number.
681 */
682void sgl_free_n_order(struct scatterlist *sgl, int nents, int order)
683{
684 struct scatterlist *sg;
685 struct page *page;
686 int i;
687
688 for_each_sg(sgl, sg, nents, i) {
689 if (!sg)
690 break;
691 page = sg_page(sg);
692 if (page)
693 __free_pages(page, order);
694 }
695 kfree(sgl);
696}
697EXPORT_SYMBOL(sgl_free_n_order);
698
699/**
700 * sgl_free_order - free a scatterlist and its pages
701 * @sgl: Scatterlist with one or more elements
702 * @order: Second argument for __free_pages()
703 */
704void sgl_free_order(struct scatterlist *sgl, int order)
705{
706 sgl_free_n_order(sgl, INT_MAX, order);
707}
708EXPORT_SYMBOL(sgl_free_order);
709
710/**
711 * sgl_free - free a scatterlist and its pages
712 * @sgl: Scatterlist with one or more elements
713 */
714void sgl_free(struct scatterlist *sgl)
715{
716 sgl_free_order(sgl, 0);
717}
718EXPORT_SYMBOL(sgl_free);
719
720#endif /* CONFIG_SGL_ALLOC */
721
722void __sg_page_iter_start(struct sg_page_iter *piter,
723 struct scatterlist *sglist, unsigned int nents,
724 unsigned long pgoffset)
725{
726 piter->__pg_advance = 0;
727 piter->__nents = nents;
728
729 piter->sg = sglist;
730 piter->sg_pgoffset = pgoffset;
731}
732EXPORT_SYMBOL(__sg_page_iter_start);
733
734static int sg_page_count(struct scatterlist *sg)
735{
736 return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
737}
738
739bool __sg_page_iter_next(struct sg_page_iter *piter)
740{
741 if (!piter->__nents || !piter->sg)
742 return false;
743
744 piter->sg_pgoffset += piter->__pg_advance;
745 piter->__pg_advance = 1;
746
747 while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
748 piter->sg_pgoffset -= sg_page_count(piter->sg);
749 piter->sg = sg_next(piter->sg);
750 if (!--piter->__nents || !piter->sg)
751 return false;
752 }
753
754 return true;
755}
756EXPORT_SYMBOL(__sg_page_iter_next);
757
758static int sg_dma_page_count(struct scatterlist *sg)
759{
760 return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT;
761}
762
763bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter)
764{
765 struct sg_page_iter *piter = &dma_iter->base;
766
767 if (!piter->__nents || !piter->sg)
768 return false;
769
770 piter->sg_pgoffset += piter->__pg_advance;
771 piter->__pg_advance = 1;
772
773 while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) {
774 piter->sg_pgoffset -= sg_dma_page_count(piter->sg);
775 piter->sg = sg_next(piter->sg);
776 if (!--piter->__nents || !piter->sg)
777 return false;
778 }
779
780 return true;
781}
782EXPORT_SYMBOL(__sg_page_iter_dma_next);
783
784/**
785 * sg_miter_start - start mapping iteration over a sg list
786 * @miter: sg mapping iter to be started
787 * @sgl: sg list to iterate over
788 * @nents: number of sg entries
789 *
790 * Description:
791 * Starts mapping iterator @miter.
792 *
793 * Context:
794 * Don't care.
795 */
796void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
797 unsigned int nents, unsigned int flags)
798{
799 memset(miter, 0, sizeof(struct sg_mapping_iter));
800
801 __sg_page_iter_start(&miter->piter, sgl, nents, 0);
802 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
803 miter->__flags = flags;
804}
805EXPORT_SYMBOL(sg_miter_start);
806
807static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
808{
809 if (!miter->__remaining) {
810 struct scatterlist *sg;
811
812 if (!__sg_page_iter_next(&miter->piter))
813 return false;
814
815 sg = miter->piter.sg;
816
817 miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset;
818 miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT;
819 miter->__offset &= PAGE_SIZE - 1;
820 miter->__remaining = sg->offset + sg->length -
821 (miter->piter.sg_pgoffset << PAGE_SHIFT) -
822 miter->__offset;
823 miter->__remaining = min_t(unsigned long, miter->__remaining,
824 PAGE_SIZE - miter->__offset);
825 }
826
827 return true;
828}
829
830/**
831 * sg_miter_skip - reposition mapping iterator
832 * @miter: sg mapping iter to be skipped
833 * @offset: number of bytes to plus the current location
834 *
835 * Description:
836 * Sets the offset of @miter to its current location plus @offset bytes.
837 * If mapping iterator @miter has been proceeded by sg_miter_next(), this
838 * stops @miter.
839 *
840 * Context:
841 * Don't care.
842 *
843 * Returns:
844 * true if @miter contains the valid mapping. false if end of sg
845 * list is reached.
846 */
847bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
848{
849 sg_miter_stop(miter);
850
851 while (offset) {
852 off_t consumed;
853
854 if (!sg_miter_get_next_page(miter))
855 return false;
856
857 consumed = min_t(off_t, offset, miter->__remaining);
858 miter->__offset += consumed;
859 miter->__remaining -= consumed;
860 offset -= consumed;
861 }
862
863 return true;
864}
865EXPORT_SYMBOL(sg_miter_skip);
866
867/**
868 * sg_miter_next - proceed mapping iterator to the next mapping
869 * @miter: sg mapping iter to proceed
870 *
871 * Description:
872 * Proceeds @miter to the next mapping. @miter should have been started
873 * using sg_miter_start(). On successful return, @miter->page,
874 * @miter->addr and @miter->length point to the current mapping.
875 *
876 * Context:
877 * May sleep if !SG_MITER_ATOMIC.
878 *
879 * Returns:
880 * true if @miter contains the next mapping. false if end of sg
881 * list is reached.
882 */
883bool sg_miter_next(struct sg_mapping_iter *miter)
884{
885 sg_miter_stop(miter);
886
887 /*
888 * Get to the next page if necessary.
889 * __remaining, __offset is adjusted by sg_miter_stop
890 */
891 if (!sg_miter_get_next_page(miter))
892 return false;
893
894 miter->page = sg_page_iter_page(&miter->piter);
895 miter->consumed = miter->length = miter->__remaining;
896
897 if (miter->__flags & SG_MITER_ATOMIC)
898 miter->addr = kmap_atomic(miter->page) + miter->__offset;
899 else
900 miter->addr = kmap(miter->page) + miter->__offset;
901
902 return true;
903}
904EXPORT_SYMBOL(sg_miter_next);
905
906/**
907 * sg_miter_stop - stop mapping iteration
908 * @miter: sg mapping iter to be stopped
909 *
910 * Description:
911 * Stops mapping iterator @miter. @miter should have been started
912 * using sg_miter_start(). A stopped iteration can be resumed by
913 * calling sg_miter_next() on it. This is useful when resources (kmap)
914 * need to be released during iteration.
915 *
916 * Context:
917 * Don't care otherwise.
918 */
919void sg_miter_stop(struct sg_mapping_iter *miter)
920{
921 WARN_ON(miter->consumed > miter->length);
922
923 /* drop resources from the last iteration */
924 if (miter->addr) {
925 miter->__offset += miter->consumed;
926 miter->__remaining -= miter->consumed;
927
928 if (miter->__flags & SG_MITER_TO_SG)
929 flush_dcache_page(miter->page);
930
931 if (miter->__flags & SG_MITER_ATOMIC) {
932 WARN_ON_ONCE(!pagefault_disabled());
933 kunmap_atomic(miter->addr);
934 } else
935 kunmap(miter->page);
936
937 miter->page = NULL;
938 miter->addr = NULL;
939 miter->length = 0;
940 miter->consumed = 0;
941 }
942}
943EXPORT_SYMBOL(sg_miter_stop);
944
945/**
946 * sg_copy_buffer - Copy data between a linear buffer and an SG list
947 * @sgl: The SG list
948 * @nents: Number of SG entries
949 * @buf: Where to copy from
950 * @buflen: The number of bytes to copy
951 * @skip: Number of bytes to skip before copying
952 * @to_buffer: transfer direction (true == from an sg list to a
953 * buffer, false == from a buffer to an sg list)
954 *
955 * Returns the number of copied bytes.
956 *
957 **/
958size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
959 size_t buflen, off_t skip, bool to_buffer)
960{
961 unsigned int offset = 0;
962 struct sg_mapping_iter miter;
963 unsigned int sg_flags = SG_MITER_ATOMIC;
964
965 if (to_buffer)
966 sg_flags |= SG_MITER_FROM_SG;
967 else
968 sg_flags |= SG_MITER_TO_SG;
969
970 sg_miter_start(&miter, sgl, nents, sg_flags);
971
972 if (!sg_miter_skip(&miter, skip))
973 return 0;
974
975 while ((offset < buflen) && sg_miter_next(&miter)) {
976 unsigned int len;
977
978 len = min(miter.length, buflen - offset);
979
980 if (to_buffer)
981 memcpy(buf + offset, miter.addr, len);
982 else
983 memcpy(miter.addr, buf + offset, len);
984
985 offset += len;
986 }
987
988 sg_miter_stop(&miter);
989
990 return offset;
991}
992EXPORT_SYMBOL(sg_copy_buffer);
993
994/**
995 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
996 * @sgl: The SG list
997 * @nents: Number of SG entries
998 * @buf: Where to copy from
999 * @buflen: The number of bytes to copy
1000 *
1001 * Returns the number of copied bytes.
1002 *
1003 **/
1004size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
1005 const void *buf, size_t buflen)
1006{
1007 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
1008}
1009EXPORT_SYMBOL(sg_copy_from_buffer);
1010
1011/**
1012 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
1013 * @sgl: The SG list
1014 * @nents: Number of SG entries
1015 * @buf: Where to copy to
1016 * @buflen: The number of bytes to copy
1017 *
1018 * Returns the number of copied bytes.
1019 *
1020 **/
1021size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
1022 void *buf, size_t buflen)
1023{
1024 return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
1025}
1026EXPORT_SYMBOL(sg_copy_to_buffer);
1027
1028/**
1029 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
1030 * @sgl: The SG list
1031 * @nents: Number of SG entries
1032 * @buf: Where to copy from
1033 * @buflen: The number of bytes to copy
1034 * @skip: Number of bytes to skip before copying
1035 *
1036 * Returns the number of copied bytes.
1037 *
1038 **/
1039size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
1040 const void *buf, size_t buflen, off_t skip)
1041{
1042 return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false);
1043}
1044EXPORT_SYMBOL(sg_pcopy_from_buffer);
1045
1046/**
1047 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
1048 * @sgl: The SG list
1049 * @nents: Number of SG entries
1050 * @buf: Where to copy to
1051 * @buflen: The number of bytes to copy
1052 * @skip: Number of bytes to skip before copying
1053 *
1054 * Returns the number of copied bytes.
1055 *
1056 **/
1057size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
1058 void *buf, size_t buflen, off_t skip)
1059{
1060 return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
1061}
1062EXPORT_SYMBOL(sg_pcopy_to_buffer);
1063
1064/**
1065 * sg_zero_buffer - Zero-out a part of a SG list
1066 * @sgl: The SG list
1067 * @nents: Number of SG entries
1068 * @buflen: The number of bytes to zero out
1069 * @skip: Number of bytes to skip before zeroing
1070 *
1071 * Returns the number of bytes zeroed.
1072 **/
1073size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
1074 size_t buflen, off_t skip)
1075{
1076 unsigned int offset = 0;
1077 struct sg_mapping_iter miter;
1078 unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
1079
1080 sg_miter_start(&miter, sgl, nents, sg_flags);
1081
1082 if (!sg_miter_skip(&miter, skip))
1083 return false;
1084
1085 while (offset < buflen && sg_miter_next(&miter)) {
1086 unsigned int len;
1087
1088 len = min(miter.length, buflen - offset);
1089 memset(miter.addr, 0, len);
1090
1091 offset += len;
1092 }
1093
1094 sg_miter_stop(&miter);
1095 return offset;
1096}
1097EXPORT_SYMBOL(sg_zero_buffer);