Line data Source code
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 : **/
23 0 : struct scatterlist *sg_next(struct scatterlist *sg)
24 : {
25 0 : if (sg_is_last(sg))
26 : return NULL;
27 :
28 0 : sg++;
29 0 : if (unlikely(sg_is_chain(sg)))
30 0 : sg = sg_chain_ptr(sg);
31 :
32 : return sg;
33 : }
34 : EXPORT_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 : **/
45 0 : int sg_nents(struct scatterlist *sg)
46 : {
47 : int nents;
48 0 : for (nents = 0; sg; sg = sg_next(sg))
49 0 : nents++;
50 0 : return nents;
51 : }
52 : EXPORT_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 : **/
68 0 : int sg_nents_for_len(struct scatterlist *sg, u64 len)
69 : {
70 : int nents;
71 : u64 total;
72 :
73 0 : if (!len)
74 : return 0;
75 :
76 0 : for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
77 0 : nents++;
78 0 : total += sg->length;
79 0 : if (total >= len)
80 : return nents;
81 : }
82 :
83 : return -EINVAL;
84 : }
85 : EXPORT_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 : **/
101 0 : struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
102 : {
103 0 : struct scatterlist *sg, *ret = NULL;
104 : unsigned int i;
105 :
106 0 : for_each_sg(sgl, sg, nents, i)
107 0 : ret = sg;
108 :
109 0 : BUG_ON(!sg_is_last(ret));
110 0 : return ret;
111 : }
112 : EXPORT_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 : **/
124 0 : void sg_init_table(struct scatterlist *sgl, unsigned int nents)
125 : {
126 0 : memset(sgl, 0, sizeof(*sgl) * nents);
127 0 : sg_init_marker(sgl, nents);
128 0 : }
129 : EXPORT_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 : **/
138 0 : void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
139 : {
140 0 : sg_init_table(sg, 1);
141 0 : sg_set_buf(sg, buf, buflen);
142 0 : }
143 : EXPORT_SYMBOL(sg_init_one);
144 :
145 : /*
146 : * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
147 : * helpers.
148 : */
149 0 : static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
150 : {
151 0 : 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 0 : void *ptr = (void *) __get_free_page(gfp_mask);
162 0 : kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
163 0 : return ptr;
164 : } else
165 0 : return kmalloc_array(nents, sizeof(struct scatterlist),
166 : gfp_mask);
167 : }
168 :
169 0 : static void sg_kfree(struct scatterlist *sg, unsigned int nents)
170 : {
171 0 : if (nents == SG_MAX_SINGLE_ALLOC) {
172 0 : kmemleak_free(sg);
173 0 : free_page((unsigned long) sg);
174 : } else
175 0 : kfree(sg);
176 0 : }
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 : **/
193 0 : void __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 0 : unsigned curr_max_ents = nents_first_chunk ?: max_ents;
199 :
200 0 : if (unlikely(!table->sgl))
201 : return;
202 :
203 : sgl = table->sgl;
204 0 : while (num_ents) {
205 0 : 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 0 : if (alloc_size > curr_max_ents) {
215 0 : next = sg_chain_ptr(&sgl[curr_max_ents - 1]);
216 0 : alloc_size = curr_max_ents;
217 0 : sg_size = alloc_size - 1;
218 : } else {
219 : sg_size = alloc_size;
220 : next = NULL;
221 : }
222 :
223 0 : num_ents -= sg_size;
224 0 : if (nents_first_chunk)
225 : nents_first_chunk = 0;
226 : else
227 0 : free_fn(sgl, alloc_size);
228 : sgl = next;
229 : curr_max_ents = max_ents;
230 : }
231 :
232 0 : table->sgl = NULL;
233 : }
234 : EXPORT_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 : **/
241 0 : void sg_free_append_table(struct sg_append_table *table)
242 : {
243 0 : __sg_free_table(&table->sgt, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
244 : table->total_nents);
245 0 : }
246 : EXPORT_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 : **/
254 0 : void sg_free_table(struct sg_table *table)
255 : {
256 0 : __sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
257 : table->orig_nents);
258 0 : }
259 : EXPORT_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 : **/
282 0 : int __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 0 : unsigned curr_max_ents = nents_first_chunk ?: max_ents;
290 : unsigned prv_max_ents;
291 :
292 0 : memset(table, 0, sizeof(*table));
293 :
294 0 : 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 0 : unsigned int sg_size, alloc_size = left;
305 :
306 0 : if (alloc_size > curr_max_ents) {
307 0 : alloc_size = curr_max_ents;
308 0 : sg_size = alloc_size - 1;
309 : } else
310 : sg_size = alloc_size;
311 :
312 0 : left -= sg_size;
313 :
314 0 : if (first_chunk) {
315 : sg = first_chunk;
316 : first_chunk = NULL;
317 : } else {
318 0 : sg = alloc_fn(alloc_size, gfp_mask);
319 : }
320 0 : 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 0 : if (prv)
328 0 : table->nents = ++table->orig_nents;
329 :
330 : return -ENOMEM;
331 : }
332 :
333 0 : sg_init_table(sg, alloc_size);
334 0 : 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 0 : if (prv)
341 : sg_chain(prv, prv_max_ents, sg);
342 : else
343 0 : table->sgl = sg;
344 :
345 : /*
346 : * If no more entries after this one, mark the end
347 : */
348 0 : if (!left)
349 0 : sg_mark_end(&sg[sg_size - 1]);
350 :
351 0 : prv = sg;
352 0 : prv_max_ents = curr_max_ents;
353 0 : curr_max_ents = max_ents;
354 0 : } while (left);
355 :
356 : return 0;
357 : }
358 : EXPORT_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 : **/
371 0 : int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
372 : {
373 : int ret;
374 :
375 0 : ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
376 : NULL, 0, gfp_mask, sg_kmalloc);
377 0 : if (unlikely(ret))
378 0 : sg_free_table(table);
379 0 : return ret;
380 : }
381 : EXPORT_SYMBOL(sg_alloc_table);
382 :
383 0 : static 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 0 : if (cur) {
392 0 : next_sg = sg_next(cur);
393 : /* Check if last entry should be keeped for chainning */
394 0 : if (!sg_is_last(next_sg) || needed_sges == 1)
395 : return next_sg;
396 : }
397 :
398 0 : alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC);
399 0 : new_sg = sg_kmalloc(alloc_size, gfp_mask);
400 0 : if (!new_sg)
401 : return ERR_PTR(-ENOMEM);
402 0 : sg_init_table(new_sg, alloc_size);
403 0 : if (cur) {
404 0 : table->total_nents += alloc_size - 1;
405 : __sg_chain(next_sg, new_sg);
406 : } else {
407 0 : table->sgt.sgl = new_sg;
408 0 : table->total_nents = alloc_size;
409 : }
410 : return new_sg;
411 : }
412 :
413 : static bool pages_are_mergeable(struct page *a, struct page *b)
414 : {
415 0 : if (page_to_pfn(a) != page_to_pfn(b) + 1)
416 : return false;
417 0 : 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 : */
451 0 : int 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 0 : unsigned int chunks, cur_page, seg_len, i, prv_len = 0;
457 0 : unsigned int added_nents = 0;
458 0 : 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 0 : max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE);
466 0 : 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 0 : if (sgt_append->prv) {
473 0 : unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) +
474 0 : sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE;
475 :
476 0 : if (WARN_ON(offset))
477 : return -EINVAL;
478 :
479 : /* Merge contiguous pages into the last SG */
480 0 : prv_len = sgt_append->prv->length;
481 0 : if (page_to_pfn(pages[0]) == next_pfn) {
482 0 : last_pg = pfn_to_page(next_pfn - 1);
483 0 : while (n_pages && pages_are_mergeable(pages[0], last_pg)) {
484 0 : if (sgt_append->prv->length + PAGE_SIZE > max_segment)
485 : break;
486 0 : sgt_append->prv->length += PAGE_SIZE;
487 0 : last_pg = pages[0];
488 0 : pages++;
489 0 : n_pages--;
490 : }
491 0 : if (!n_pages)
492 : goto out;
493 : }
494 : }
495 :
496 : /* compute number of contiguous chunks */
497 0 : chunks = 1;
498 0 : seg_len = 0;
499 0 : for (i = 1; i < n_pages; i++) {
500 0 : seg_len += PAGE_SIZE;
501 0 : if (seg_len >= max_segment ||
502 0 : !pages_are_mergeable(pages[i], pages[i - 1])) {
503 0 : chunks++;
504 0 : seg_len = 0;
505 : }
506 : }
507 :
508 : /* merging chunks and putting them into the scatterlist */
509 : cur_page = 0;
510 0 : for (i = 0; i < chunks; i++) {
511 : unsigned int j, chunk_size;
512 :
513 : /* look for the end of the current chunk */
514 0 : seg_len = 0;
515 0 : for (j = cur_page + 1; j < n_pages; j++) {
516 0 : seg_len += PAGE_SIZE;
517 0 : if (seg_len >= max_segment ||
518 0 : !pages_are_mergeable(pages[j], pages[j - 1]))
519 : break;
520 : }
521 :
522 : /* Pass how many chunks might be left */
523 0 : s = get_next_sg(sgt_append, s, chunks - i + left_pages,
524 : gfp_mask);
525 0 : if (IS_ERR(s)) {
526 : /*
527 : * Adjust entry length to be as before function was
528 : * called.
529 : */
530 0 : if (sgt_append->prv)
531 0 : sgt_append->prv->length = prv_len;
532 0 : return PTR_ERR(s);
533 : }
534 0 : chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
535 0 : sg_set_page(s, pages[cur_page],
536 0 : min_t(unsigned long, size, chunk_size), offset);
537 0 : added_nents++;
538 0 : size -= chunk_size;
539 0 : offset = 0;
540 0 : cur_page = j;
541 : }
542 0 : sgt_append->sgt.nents += added_nents;
543 0 : sgt_append->sgt.orig_nents = sgt_append->sgt.nents;
544 0 : sgt_append->prv = s;
545 : out:
546 0 : if (!left_pages)
547 0 : sg_mark_end(s);
548 : return 0;
549 : }
550 : EXPORT_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 : */
575 0 : int 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 0 : struct sg_append_table append = {};
581 : int err;
582 :
583 0 : err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset,
584 : size, max_segment, 0, gfp_mask);
585 0 : if (err) {
586 0 : sg_free_append_table(&append);
587 0 : return err;
588 : }
589 0 : memcpy(sgt, &append.sgt, sizeof(*sgt));
590 0 : WARN_ON(append.total_nents != sgt->orig_nents);
591 : return 0;
592 : }
593 : EXPORT_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 : */
608 : struct 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 : }
652 : EXPORT_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 : */
662 : struct 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 : }
667 : EXPORT_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 : */
682 : void 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 : }
697 : EXPORT_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 : */
704 : void sgl_free_order(struct scatterlist *sgl, int order)
705 : {
706 : sgl_free_n_order(sgl, INT_MAX, order);
707 : }
708 : EXPORT_SYMBOL(sgl_free_order);
709 :
710 : /**
711 : * sgl_free - free a scatterlist and its pages
712 : * @sgl: Scatterlist with one or more elements
713 : */
714 : void sgl_free(struct scatterlist *sgl)
715 : {
716 : sgl_free_order(sgl, 0);
717 : }
718 : EXPORT_SYMBOL(sgl_free);
719 :
720 : #endif /* CONFIG_SGL_ALLOC */
721 :
722 0 : void __sg_page_iter_start(struct sg_page_iter *piter,
723 : struct scatterlist *sglist, unsigned int nents,
724 : unsigned long pgoffset)
725 : {
726 0 : piter->__pg_advance = 0;
727 0 : piter->__nents = nents;
728 :
729 0 : piter->sg = sglist;
730 0 : piter->sg_pgoffset = pgoffset;
731 0 : }
732 : EXPORT_SYMBOL(__sg_page_iter_start);
733 :
734 : static int sg_page_count(struct scatterlist *sg)
735 : {
736 0 : return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
737 : }
738 :
739 0 : bool __sg_page_iter_next(struct sg_page_iter *piter)
740 : {
741 0 : if (!piter->__nents || !piter->sg)
742 : return false;
743 :
744 0 : piter->sg_pgoffset += piter->__pg_advance;
745 0 : piter->__pg_advance = 1;
746 :
747 0 : while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
748 0 : piter->sg_pgoffset -= sg_page_count(piter->sg);
749 0 : piter->sg = sg_next(piter->sg);
750 0 : if (!--piter->__nents || !piter->sg)
751 : return false;
752 : }
753 :
754 : return true;
755 : }
756 : EXPORT_SYMBOL(__sg_page_iter_next);
757 :
758 : static int sg_dma_page_count(struct scatterlist *sg)
759 : {
760 0 : return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT;
761 : }
762 :
763 0 : bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter)
764 : {
765 0 : struct sg_page_iter *piter = &dma_iter->base;
766 :
767 0 : if (!piter->__nents || !piter->sg)
768 : return false;
769 :
770 0 : piter->sg_pgoffset += piter->__pg_advance;
771 0 : piter->__pg_advance = 1;
772 :
773 0 : while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) {
774 0 : piter->sg_pgoffset -= sg_dma_page_count(piter->sg);
775 0 : piter->sg = sg_next(piter->sg);
776 0 : if (!--piter->__nents || !piter->sg)
777 : return false;
778 : }
779 :
780 : return true;
781 : }
782 : EXPORT_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 : */
796 0 : void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
797 : unsigned int nents, unsigned int flags)
798 : {
799 0 : memset(miter, 0, sizeof(struct sg_mapping_iter));
800 :
801 0 : __sg_page_iter_start(&miter->piter, sgl, nents, 0);
802 0 : WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
803 0 : miter->__flags = flags;
804 0 : }
805 : EXPORT_SYMBOL(sg_miter_start);
806 :
807 0 : static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
808 : {
809 0 : if (!miter->__remaining) {
810 : struct scatterlist *sg;
811 :
812 0 : if (!__sg_page_iter_next(&miter->piter))
813 : return false;
814 :
815 0 : sg = miter->piter.sg;
816 :
817 0 : miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset;
818 0 : miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT;
819 0 : miter->__offset &= PAGE_SIZE - 1;
820 0 : miter->__remaining = sg->offset + sg->length -
821 0 : (miter->piter.sg_pgoffset << PAGE_SHIFT) -
822 : miter->__offset;
823 0 : 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 : */
847 0 : bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
848 : {
849 0 : sg_miter_stop(miter);
850 :
851 0 : while (offset) {
852 : off_t consumed;
853 :
854 0 : if (!sg_miter_get_next_page(miter))
855 : return false;
856 :
857 0 : consumed = min_t(off_t, offset, miter->__remaining);
858 0 : miter->__offset += consumed;
859 0 : miter->__remaining -= consumed;
860 0 : offset -= consumed;
861 : }
862 :
863 : return true;
864 : }
865 : EXPORT_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 : */
883 0 : bool sg_miter_next(struct sg_mapping_iter *miter)
884 : {
885 0 : 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 0 : if (!sg_miter_get_next_page(miter))
892 : return false;
893 :
894 0 : miter->page = sg_page_iter_page(&miter->piter);
895 0 : miter->consumed = miter->length = miter->__remaining;
896 :
897 0 : if (miter->__flags & SG_MITER_ATOMIC)
898 0 : miter->addr = kmap_atomic(miter->page) + miter->__offset;
899 : else
900 0 : miter->addr = kmap(miter->page) + miter->__offset;
901 :
902 : return true;
903 : }
904 : EXPORT_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 : */
919 0 : void sg_miter_stop(struct sg_mapping_iter *miter)
920 : {
921 0 : WARN_ON(miter->consumed > miter->length);
922 :
923 : /* drop resources from the last iteration */
924 0 : if (miter->addr) {
925 0 : miter->__offset += miter->consumed;
926 0 : miter->__remaining -= miter->consumed;
927 :
928 0 : if (miter->__flags & SG_MITER_TO_SG)
929 : flush_dcache_page(miter->page);
930 :
931 0 : if (miter->__flags & SG_MITER_ATOMIC) {
932 0 : WARN_ON_ONCE(!pagefault_disabled());
933 0 : kunmap_atomic(miter->addr);
934 : } else
935 : kunmap(miter->page);
936 :
937 0 : miter->page = NULL;
938 0 : miter->addr = NULL;
939 0 : miter->length = 0;
940 0 : miter->consumed = 0;
941 : }
942 0 : }
943 : EXPORT_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 : **/
958 0 : size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
959 : size_t buflen, off_t skip, bool to_buffer)
960 : {
961 0 : unsigned int offset = 0;
962 : struct sg_mapping_iter miter;
963 0 : unsigned int sg_flags = SG_MITER_ATOMIC;
964 :
965 0 : if (to_buffer)
966 : sg_flags |= SG_MITER_FROM_SG;
967 : else
968 0 : sg_flags |= SG_MITER_TO_SG;
969 :
970 0 : sg_miter_start(&miter, sgl, nents, sg_flags);
971 :
972 0 : if (!sg_miter_skip(&miter, skip))
973 : return 0;
974 :
975 0 : while ((offset < buflen) && sg_miter_next(&miter)) {
976 : unsigned int len;
977 :
978 0 : len = min(miter.length, buflen - offset);
979 :
980 0 : if (to_buffer)
981 0 : memcpy(buf + offset, miter.addr, len);
982 : else
983 0 : memcpy(miter.addr, buf + offset, len);
984 :
985 0 : offset += len;
986 : }
987 :
988 0 : sg_miter_stop(&miter);
989 :
990 0 : return offset;
991 : }
992 : EXPORT_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 : **/
1004 0 : size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
1005 : const void *buf, size_t buflen)
1006 : {
1007 0 : return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
1008 : }
1009 : EXPORT_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 : **/
1021 0 : size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
1022 : void *buf, size_t buflen)
1023 : {
1024 0 : return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
1025 : }
1026 : EXPORT_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 : **/
1039 0 : size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
1040 : const void *buf, size_t buflen, off_t skip)
1041 : {
1042 0 : return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false);
1043 : }
1044 : EXPORT_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 : **/
1057 0 : size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
1058 : void *buf, size_t buflen, off_t skip)
1059 : {
1060 0 : return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
1061 : }
1062 : EXPORT_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 : **/
1073 0 : size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
1074 : size_t buflen, off_t skip)
1075 : {
1076 0 : unsigned int offset = 0;
1077 : struct sg_mapping_iter miter;
1078 0 : unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
1079 :
1080 0 : sg_miter_start(&miter, sgl, nents, sg_flags);
1081 :
1082 0 : if (!sg_miter_skip(&miter, skip))
1083 : return false;
1084 :
1085 0 : while (offset < buflen && sg_miter_next(&miter)) {
1086 : unsigned int len;
1087 :
1088 0 : len = min(miter.length, buflen - offset);
1089 0 : memset(miter.addr, 0, len);
1090 :
1091 0 : offset += len;
1092 : }
1093 :
1094 0 : sg_miter_stop(&miter);
1095 0 : return offset;
1096 : }
1097 : EXPORT_SYMBOL(sg_zero_buffer);
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