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 : #include <linux/bvec.h>
13 : #include <linux/uio.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 : **/
25 0 : struct scatterlist *sg_next(struct scatterlist *sg)
26 : {
27 0 : if (sg_is_last(sg))
28 : return NULL;
29 :
30 0 : sg++;
31 0 : if (unlikely(sg_is_chain(sg)))
32 0 : sg = sg_chain_ptr(sg);
33 :
34 : return sg;
35 : }
36 : EXPORT_SYMBOL(sg_next);
37 :
38 : /**
39 : * sg_nents - return total count of entries in scatterlist
40 : * @sg: The scatterlist
41 : *
42 : * Description:
43 : * Allows to know how many entries are in sg, taking into account
44 : * chaining as well
45 : *
46 : **/
47 0 : int sg_nents(struct scatterlist *sg)
48 : {
49 : int nents;
50 0 : for (nents = 0; sg; sg = sg_next(sg))
51 0 : nents++;
52 0 : return nents;
53 : }
54 : EXPORT_SYMBOL(sg_nents);
55 :
56 : /**
57 : * sg_nents_for_len - return total count of entries in scatterlist
58 : * needed to satisfy the supplied length
59 : * @sg: The scatterlist
60 : * @len: The total required length
61 : *
62 : * Description:
63 : * Determines the number of entries in sg that are required to meet
64 : * the supplied length, taking into account chaining as well
65 : *
66 : * Returns:
67 : * the number of sg entries needed, negative error on failure
68 : *
69 : **/
70 0 : int sg_nents_for_len(struct scatterlist *sg, u64 len)
71 : {
72 : int nents;
73 : u64 total;
74 :
75 0 : if (!len)
76 : return 0;
77 :
78 0 : for (nents = 0, total = 0; sg; sg = sg_next(sg)) {
79 0 : nents++;
80 0 : total += sg->length;
81 0 : if (total >= len)
82 : return nents;
83 : }
84 :
85 : return -EINVAL;
86 : }
87 : EXPORT_SYMBOL(sg_nents_for_len);
88 :
89 : /**
90 : * sg_last - return the last scatterlist entry in a list
91 : * @sgl: First entry in the scatterlist
92 : * @nents: Number of entries in the scatterlist
93 : *
94 : * Description:
95 : * Should only be used casually, it (currently) scans the entire list
96 : * to get the last entry.
97 : *
98 : * Note that the @sgl@ pointer passed in need not be the first one,
99 : * the important bit is that @nents@ denotes the number of entries that
100 : * exist from @sgl@.
101 : *
102 : **/
103 0 : struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
104 : {
105 0 : struct scatterlist *sg, *ret = NULL;
106 : unsigned int i;
107 :
108 0 : for_each_sg(sgl, sg, nents, i)
109 0 : ret = sg;
110 :
111 0 : BUG_ON(!sg_is_last(ret));
112 0 : return ret;
113 : }
114 : EXPORT_SYMBOL(sg_last);
115 :
116 : /**
117 : * sg_init_table - Initialize SG table
118 : * @sgl: The SG table
119 : * @nents: Number of entries in table
120 : *
121 : * Notes:
122 : * If this is part of a chained sg table, sg_mark_end() should be
123 : * used only on the last table part.
124 : *
125 : **/
126 0 : void sg_init_table(struct scatterlist *sgl, unsigned int nents)
127 : {
128 0 : memset(sgl, 0, sizeof(*sgl) * nents);
129 0 : sg_init_marker(sgl, nents);
130 0 : }
131 : EXPORT_SYMBOL(sg_init_table);
132 :
133 : /**
134 : * sg_init_one - Initialize a single entry sg list
135 : * @sg: SG entry
136 : * @buf: Virtual address for IO
137 : * @buflen: IO length
138 : *
139 : **/
140 0 : void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
141 : {
142 0 : sg_init_table(sg, 1);
143 0 : sg_set_buf(sg, buf, buflen);
144 0 : }
145 : EXPORT_SYMBOL(sg_init_one);
146 :
147 : /*
148 : * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
149 : * helpers.
150 : */
151 0 : static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
152 : {
153 0 : if (nents == SG_MAX_SINGLE_ALLOC) {
154 : /*
155 : * Kmemleak doesn't track page allocations as they are not
156 : * commonly used (in a raw form) for kernel data structures.
157 : * As we chain together a list of pages and then a normal
158 : * kmalloc (tracked by kmemleak), in order to for that last
159 : * allocation not to become decoupled (and thus a
160 : * false-positive) we need to inform kmemleak of all the
161 : * intermediate allocations.
162 : */
163 0 : void *ptr = (void *) __get_free_page(gfp_mask);
164 0 : kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
165 0 : return ptr;
166 : } else
167 0 : return kmalloc_array(nents, sizeof(struct scatterlist),
168 : gfp_mask);
169 : }
170 :
171 0 : static void sg_kfree(struct scatterlist *sg, unsigned int nents)
172 : {
173 0 : if (nents == SG_MAX_SINGLE_ALLOC) {
174 0 : kmemleak_free(sg);
175 0 : free_page((unsigned long) sg);
176 : } else
177 0 : kfree(sg);
178 0 : }
179 :
180 : /**
181 : * __sg_free_table - Free a previously mapped sg table
182 : * @table: The sg table header to use
183 : * @max_ents: The maximum number of entries per single scatterlist
184 : * @nents_first_chunk: Number of entries int the (preallocated) first
185 : * scatterlist chunk, 0 means no such preallocated first chunk
186 : * @free_fn: Free function
187 : * @num_ents: Number of entries in the table
188 : *
189 : * Description:
190 : * Free an sg table previously allocated and setup with
191 : * __sg_alloc_table(). The @max_ents value must be identical to
192 : * that previously used with __sg_alloc_table().
193 : *
194 : **/
195 0 : void __sg_free_table(struct sg_table *table, unsigned int max_ents,
196 : unsigned int nents_first_chunk, sg_free_fn *free_fn,
197 : unsigned int num_ents)
198 : {
199 : struct scatterlist *sgl, *next;
200 0 : unsigned curr_max_ents = nents_first_chunk ?: max_ents;
201 :
202 0 : if (unlikely(!table->sgl))
203 : return;
204 :
205 : sgl = table->sgl;
206 0 : while (num_ents) {
207 0 : unsigned int alloc_size = num_ents;
208 : unsigned int sg_size;
209 :
210 : /*
211 : * If we have more than max_ents segments left,
212 : * then assign 'next' to the sg table after the current one.
213 : * sg_size is then one less than alloc size, since the last
214 : * element is the chain pointer.
215 : */
216 0 : if (alloc_size > curr_max_ents) {
217 0 : next = sg_chain_ptr(&sgl[curr_max_ents - 1]);
218 0 : alloc_size = curr_max_ents;
219 0 : sg_size = alloc_size - 1;
220 : } else {
221 : sg_size = alloc_size;
222 : next = NULL;
223 : }
224 :
225 0 : num_ents -= sg_size;
226 0 : if (nents_first_chunk)
227 : nents_first_chunk = 0;
228 : else
229 0 : free_fn(sgl, alloc_size);
230 : sgl = next;
231 : curr_max_ents = max_ents;
232 : }
233 :
234 0 : table->sgl = NULL;
235 : }
236 : EXPORT_SYMBOL(__sg_free_table);
237 :
238 : /**
239 : * sg_free_append_table - Free a previously allocated append sg table.
240 : * @table: The mapped sg append table header
241 : *
242 : **/
243 0 : void sg_free_append_table(struct sg_append_table *table)
244 : {
245 0 : __sg_free_table(&table->sgt, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
246 : table->total_nents);
247 0 : }
248 : EXPORT_SYMBOL(sg_free_append_table);
249 :
250 :
251 : /**
252 : * sg_free_table - Free a previously allocated sg table
253 : * @table: The mapped sg table header
254 : *
255 : **/
256 0 : void sg_free_table(struct sg_table *table)
257 : {
258 0 : __sg_free_table(table, SG_MAX_SINGLE_ALLOC, 0, sg_kfree,
259 : table->orig_nents);
260 0 : }
261 : EXPORT_SYMBOL(sg_free_table);
262 :
263 : /**
264 : * __sg_alloc_table - Allocate and initialize an sg table with given allocator
265 : * @table: The sg table header to use
266 : * @nents: Number of entries in sg list
267 : * @max_ents: The maximum number of entries the allocator returns per call
268 : * @nents_first_chunk: Number of entries int the (preallocated) first
269 : * scatterlist chunk, 0 means no such preallocated chunk provided by user
270 : * @gfp_mask: GFP allocation mask
271 : * @alloc_fn: Allocator to use
272 : *
273 : * Description:
274 : * This function returns a @table @nents long. The allocator is
275 : * defined to return scatterlist chunks of maximum size @max_ents.
276 : * Thus if @nents is bigger than @max_ents, the scatterlists will be
277 : * chained in units of @max_ents.
278 : *
279 : * Notes:
280 : * If this function returns non-0 (eg failure), the caller must call
281 : * __sg_free_table() to cleanup any leftover allocations.
282 : *
283 : **/
284 0 : int __sg_alloc_table(struct sg_table *table, unsigned int nents,
285 : unsigned int max_ents, struct scatterlist *first_chunk,
286 : unsigned int nents_first_chunk, gfp_t gfp_mask,
287 : sg_alloc_fn *alloc_fn)
288 : {
289 : struct scatterlist *sg, *prv;
290 : unsigned int left;
291 0 : unsigned curr_max_ents = nents_first_chunk ?: max_ents;
292 : unsigned prv_max_ents;
293 :
294 0 : memset(table, 0, sizeof(*table));
295 :
296 0 : if (nents == 0)
297 : return -EINVAL;
298 : #ifdef CONFIG_ARCH_NO_SG_CHAIN
299 : if (WARN_ON_ONCE(nents > max_ents))
300 : return -EINVAL;
301 : #endif
302 :
303 : left = nents;
304 : prv = NULL;
305 : do {
306 0 : unsigned int sg_size, alloc_size = left;
307 :
308 0 : if (alloc_size > curr_max_ents) {
309 0 : alloc_size = curr_max_ents;
310 0 : sg_size = alloc_size - 1;
311 : } else
312 : sg_size = alloc_size;
313 :
314 0 : left -= sg_size;
315 :
316 0 : if (first_chunk) {
317 : sg = first_chunk;
318 : first_chunk = NULL;
319 : } else {
320 0 : sg = alloc_fn(alloc_size, gfp_mask);
321 : }
322 0 : if (unlikely(!sg)) {
323 : /*
324 : * Adjust entry count to reflect that the last
325 : * entry of the previous table won't be used for
326 : * linkage. Without this, sg_kfree() may get
327 : * confused.
328 : */
329 0 : if (prv)
330 0 : table->nents = ++table->orig_nents;
331 :
332 : return -ENOMEM;
333 : }
334 :
335 0 : sg_init_table(sg, alloc_size);
336 0 : table->nents = table->orig_nents += sg_size;
337 :
338 : /*
339 : * If this is the first mapping, assign the sg table header.
340 : * If this is not the first mapping, chain previous part.
341 : */
342 0 : if (prv)
343 : sg_chain(prv, prv_max_ents, sg);
344 : else
345 0 : table->sgl = sg;
346 :
347 : /*
348 : * If no more entries after this one, mark the end
349 : */
350 0 : if (!left)
351 0 : sg_mark_end(&sg[sg_size - 1]);
352 :
353 0 : prv = sg;
354 0 : prv_max_ents = curr_max_ents;
355 0 : curr_max_ents = max_ents;
356 0 : } while (left);
357 :
358 : return 0;
359 : }
360 : EXPORT_SYMBOL(__sg_alloc_table);
361 :
362 : /**
363 : * sg_alloc_table - Allocate and initialize an sg table
364 : * @table: The sg table header to use
365 : * @nents: Number of entries in sg list
366 : * @gfp_mask: GFP allocation mask
367 : *
368 : * Description:
369 : * Allocate and initialize an sg table. If @nents@ is larger than
370 : * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
371 : *
372 : **/
373 0 : int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
374 : {
375 : int ret;
376 :
377 0 : ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
378 : NULL, 0, gfp_mask, sg_kmalloc);
379 0 : if (unlikely(ret))
380 0 : sg_free_table(table);
381 0 : return ret;
382 : }
383 : EXPORT_SYMBOL(sg_alloc_table);
384 :
385 0 : static struct scatterlist *get_next_sg(struct sg_append_table *table,
386 : struct scatterlist *cur,
387 : unsigned long needed_sges,
388 : gfp_t gfp_mask)
389 : {
390 : struct scatterlist *new_sg, *next_sg;
391 : unsigned int alloc_size;
392 :
393 0 : if (cur) {
394 0 : next_sg = sg_next(cur);
395 : /* Check if last entry should be keeped for chainning */
396 0 : if (!sg_is_last(next_sg) || needed_sges == 1)
397 : return next_sg;
398 : }
399 :
400 0 : alloc_size = min_t(unsigned long, needed_sges, SG_MAX_SINGLE_ALLOC);
401 0 : new_sg = sg_kmalloc(alloc_size, gfp_mask);
402 0 : if (!new_sg)
403 : return ERR_PTR(-ENOMEM);
404 0 : sg_init_table(new_sg, alloc_size);
405 0 : if (cur) {
406 0 : table->total_nents += alloc_size - 1;
407 : __sg_chain(next_sg, new_sg);
408 : } else {
409 0 : table->sgt.sgl = new_sg;
410 0 : table->total_nents = alloc_size;
411 : }
412 : return new_sg;
413 : }
414 :
415 : static bool pages_are_mergeable(struct page *a, struct page *b)
416 : {
417 0 : if (page_to_pfn(a) != page_to_pfn(b) + 1)
418 : return false;
419 0 : if (!zone_device_pages_have_same_pgmap(a, b))
420 : return false;
421 : return true;
422 : }
423 :
424 : /**
425 : * sg_alloc_append_table_from_pages - Allocate and initialize an append sg
426 : * table from an array of pages
427 : * @sgt_append: The sg append table to use
428 : * @pages: Pointer to an array of page pointers
429 : * @n_pages: Number of pages in the pages array
430 : * @offset: Offset from start of the first page to the start of a buffer
431 : * @size: Number of valid bytes in the buffer (after offset)
432 : * @max_segment: Maximum size of a scatterlist element in bytes
433 : * @left_pages: Left pages caller have to set after this call
434 : * @gfp_mask: GFP allocation mask
435 : *
436 : * Description:
437 : * In the first call it allocate and initialize an sg table from a list of
438 : * pages, else reuse the scatterlist from sgt_append. Contiguous ranges of
439 : * the pages are squashed into a single scatterlist entry up to the maximum
440 : * size specified in @max_segment. A user may provide an offset at a start
441 : * and a size of valid data in a buffer specified by the page array. The
442 : * returned sg table is released by sg_free_append_table
443 : *
444 : * Returns:
445 : * 0 on success, negative error on failure
446 : *
447 : * Notes:
448 : * If this function returns non-0 (eg failure), the caller must call
449 : * sg_free_append_table() to cleanup any leftover allocations.
450 : *
451 : * In the fist call, sgt_append must by initialized.
452 : */
453 0 : int sg_alloc_append_table_from_pages(struct sg_append_table *sgt_append,
454 : struct page **pages, unsigned int n_pages, unsigned int offset,
455 : unsigned long size, unsigned int max_segment,
456 : unsigned int left_pages, gfp_t gfp_mask)
457 : {
458 0 : unsigned int chunks, cur_page, seg_len, i, prv_len = 0;
459 0 : unsigned int added_nents = 0;
460 0 : struct scatterlist *s = sgt_append->prv;
461 : struct page *last_pg;
462 :
463 : /*
464 : * The algorithm below requires max_segment to be aligned to PAGE_SIZE
465 : * otherwise it can overshoot.
466 : */
467 0 : max_segment = ALIGN_DOWN(max_segment, PAGE_SIZE);
468 0 : if (WARN_ON(max_segment < PAGE_SIZE))
469 : return -EINVAL;
470 :
471 : if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN) && sgt_append->prv)
472 : return -EOPNOTSUPP;
473 :
474 0 : if (sgt_append->prv) {
475 0 : unsigned long next_pfn = (page_to_phys(sg_page(sgt_append->prv)) +
476 0 : sgt_append->prv->offset + sgt_append->prv->length) / PAGE_SIZE;
477 :
478 0 : if (WARN_ON(offset))
479 : return -EINVAL;
480 :
481 : /* Merge contiguous pages into the last SG */
482 0 : prv_len = sgt_append->prv->length;
483 0 : if (page_to_pfn(pages[0]) == next_pfn) {
484 0 : last_pg = pfn_to_page(next_pfn - 1);
485 0 : while (n_pages && pages_are_mergeable(pages[0], last_pg)) {
486 0 : if (sgt_append->prv->length + PAGE_SIZE > max_segment)
487 : break;
488 0 : sgt_append->prv->length += PAGE_SIZE;
489 0 : last_pg = pages[0];
490 0 : pages++;
491 0 : n_pages--;
492 : }
493 0 : if (!n_pages)
494 : goto out;
495 : }
496 : }
497 :
498 : /* compute number of contiguous chunks */
499 0 : chunks = 1;
500 0 : seg_len = 0;
501 0 : for (i = 1; i < n_pages; i++) {
502 0 : seg_len += PAGE_SIZE;
503 0 : if (seg_len >= max_segment ||
504 0 : !pages_are_mergeable(pages[i], pages[i - 1])) {
505 0 : chunks++;
506 0 : seg_len = 0;
507 : }
508 : }
509 :
510 : /* merging chunks and putting them into the scatterlist */
511 : cur_page = 0;
512 0 : for (i = 0; i < chunks; i++) {
513 : unsigned int j, chunk_size;
514 :
515 : /* look for the end of the current chunk */
516 0 : seg_len = 0;
517 0 : for (j = cur_page + 1; j < n_pages; j++) {
518 0 : seg_len += PAGE_SIZE;
519 0 : if (seg_len >= max_segment ||
520 0 : !pages_are_mergeable(pages[j], pages[j - 1]))
521 : break;
522 : }
523 :
524 : /* Pass how many chunks might be left */
525 0 : s = get_next_sg(sgt_append, s, chunks - i + left_pages,
526 : gfp_mask);
527 0 : if (IS_ERR(s)) {
528 : /*
529 : * Adjust entry length to be as before function was
530 : * called.
531 : */
532 0 : if (sgt_append->prv)
533 0 : sgt_append->prv->length = prv_len;
534 0 : return PTR_ERR(s);
535 : }
536 0 : chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
537 0 : sg_set_page(s, pages[cur_page],
538 0 : min_t(unsigned long, size, chunk_size), offset);
539 0 : added_nents++;
540 0 : size -= chunk_size;
541 0 : offset = 0;
542 0 : cur_page = j;
543 : }
544 0 : sgt_append->sgt.nents += added_nents;
545 0 : sgt_append->sgt.orig_nents = sgt_append->sgt.nents;
546 0 : sgt_append->prv = s;
547 : out:
548 0 : if (!left_pages)
549 0 : sg_mark_end(s);
550 : return 0;
551 : }
552 : EXPORT_SYMBOL(sg_alloc_append_table_from_pages);
553 :
554 : /**
555 : * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from
556 : * an array of pages and given maximum
557 : * segment.
558 : * @sgt: The sg table header to use
559 : * @pages: Pointer to an array of page pointers
560 : * @n_pages: Number of pages in the pages array
561 : * @offset: Offset from start of the first page to the start of a buffer
562 : * @size: Number of valid bytes in the buffer (after offset)
563 : * @max_segment: Maximum size of a scatterlist element in bytes
564 : * @gfp_mask: GFP allocation mask
565 : *
566 : * Description:
567 : * Allocate and initialize an sg table from a list of pages. Contiguous
568 : * ranges of the pages are squashed into a single scatterlist node up to the
569 : * maximum size specified in @max_segment. A user may provide an offset at a
570 : * start and a size of valid data in a buffer specified by the page array.
571 : *
572 : * The returned sg table is released by sg_free_table.
573 : *
574 : * Returns:
575 : * 0 on success, negative error on failure
576 : */
577 0 : int sg_alloc_table_from_pages_segment(struct sg_table *sgt, struct page **pages,
578 : unsigned int n_pages, unsigned int offset,
579 : unsigned long size, unsigned int max_segment,
580 : gfp_t gfp_mask)
581 : {
582 0 : struct sg_append_table append = {};
583 : int err;
584 :
585 0 : err = sg_alloc_append_table_from_pages(&append, pages, n_pages, offset,
586 : size, max_segment, 0, gfp_mask);
587 0 : if (err) {
588 0 : sg_free_append_table(&append);
589 0 : return err;
590 : }
591 0 : memcpy(sgt, &append.sgt, sizeof(*sgt));
592 0 : WARN_ON(append.total_nents != sgt->orig_nents);
593 : return 0;
594 : }
595 : EXPORT_SYMBOL(sg_alloc_table_from_pages_segment);
596 :
597 : #ifdef CONFIG_SGL_ALLOC
598 :
599 : /**
600 : * sgl_alloc_order - allocate a scatterlist and its pages
601 : * @length: Length in bytes of the scatterlist. Must be at least one
602 : * @order: Second argument for alloc_pages()
603 : * @chainable: Whether or not to allocate an extra element in the scatterlist
604 : * for scatterlist chaining purposes
605 : * @gfp: Memory allocation flags
606 : * @nent_p: [out] Number of entries in the scatterlist that have pages
607 : *
608 : * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
609 : */
610 : struct scatterlist *sgl_alloc_order(unsigned long long length,
611 : unsigned int order, bool chainable,
612 : gfp_t gfp, unsigned int *nent_p)
613 : {
614 : struct scatterlist *sgl, *sg;
615 : struct page *page;
616 : unsigned int nent, nalloc;
617 : u32 elem_len;
618 :
619 : nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order);
620 : /* Check for integer overflow */
621 : if (length > (nent << (PAGE_SHIFT + order)))
622 : return NULL;
623 : nalloc = nent;
624 : if (chainable) {
625 : /* Check for integer overflow */
626 : if (nalloc + 1 < nalloc)
627 : return NULL;
628 : nalloc++;
629 : }
630 : sgl = kmalloc_array(nalloc, sizeof(struct scatterlist),
631 : gfp & ~GFP_DMA);
632 : if (!sgl)
633 : return NULL;
634 :
635 : sg_init_table(sgl, nalloc);
636 : sg = sgl;
637 : while (length) {
638 : elem_len = min_t(u64, length, PAGE_SIZE << order);
639 : page = alloc_pages(gfp, order);
640 : if (!page) {
641 : sgl_free_order(sgl, order);
642 : return NULL;
643 : }
644 :
645 : sg_set_page(sg, page, elem_len, 0);
646 : length -= elem_len;
647 : sg = sg_next(sg);
648 : }
649 : WARN_ONCE(length, "length = %lld\n", length);
650 : if (nent_p)
651 : *nent_p = nent;
652 : return sgl;
653 : }
654 : EXPORT_SYMBOL(sgl_alloc_order);
655 :
656 : /**
657 : * sgl_alloc - allocate a scatterlist and its pages
658 : * @length: Length in bytes of the scatterlist
659 : * @gfp: Memory allocation flags
660 : * @nent_p: [out] Number of entries in the scatterlist
661 : *
662 : * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
663 : */
664 : struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,
665 : unsigned int *nent_p)
666 : {
667 : return sgl_alloc_order(length, 0, false, gfp, nent_p);
668 : }
669 : EXPORT_SYMBOL(sgl_alloc);
670 :
671 : /**
672 : * sgl_free_n_order - free a scatterlist and its pages
673 : * @sgl: Scatterlist with one or more elements
674 : * @nents: Maximum number of elements to free
675 : * @order: Second argument for __free_pages()
676 : *
677 : * Notes:
678 : * - If several scatterlists have been chained and each chain element is
679 : * freed separately then it's essential to set nents correctly to avoid that a
680 : * page would get freed twice.
681 : * - All pages in a chained scatterlist can be freed at once by setting @nents
682 : * to a high number.
683 : */
684 : void sgl_free_n_order(struct scatterlist *sgl, int nents, int order)
685 : {
686 : struct scatterlist *sg;
687 : struct page *page;
688 : int i;
689 :
690 : for_each_sg(sgl, sg, nents, i) {
691 : if (!sg)
692 : break;
693 : page = sg_page(sg);
694 : if (page)
695 : __free_pages(page, order);
696 : }
697 : kfree(sgl);
698 : }
699 : EXPORT_SYMBOL(sgl_free_n_order);
700 :
701 : /**
702 : * sgl_free_order - free a scatterlist and its pages
703 : * @sgl: Scatterlist with one or more elements
704 : * @order: Second argument for __free_pages()
705 : */
706 : void sgl_free_order(struct scatterlist *sgl, int order)
707 : {
708 : sgl_free_n_order(sgl, INT_MAX, order);
709 : }
710 : EXPORT_SYMBOL(sgl_free_order);
711 :
712 : /**
713 : * sgl_free - free a scatterlist and its pages
714 : * @sgl: Scatterlist with one or more elements
715 : */
716 : void sgl_free(struct scatterlist *sgl)
717 : {
718 : sgl_free_order(sgl, 0);
719 : }
720 : EXPORT_SYMBOL(sgl_free);
721 :
722 : #endif /* CONFIG_SGL_ALLOC */
723 :
724 0 : void __sg_page_iter_start(struct sg_page_iter *piter,
725 : struct scatterlist *sglist, unsigned int nents,
726 : unsigned long pgoffset)
727 : {
728 0 : piter->__pg_advance = 0;
729 0 : piter->__nents = nents;
730 :
731 0 : piter->sg = sglist;
732 0 : piter->sg_pgoffset = pgoffset;
733 0 : }
734 : EXPORT_SYMBOL(__sg_page_iter_start);
735 :
736 : static int sg_page_count(struct scatterlist *sg)
737 : {
738 0 : return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
739 : }
740 :
741 0 : bool __sg_page_iter_next(struct sg_page_iter *piter)
742 : {
743 0 : if (!piter->__nents || !piter->sg)
744 : return false;
745 :
746 0 : piter->sg_pgoffset += piter->__pg_advance;
747 0 : piter->__pg_advance = 1;
748 :
749 0 : while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
750 0 : piter->sg_pgoffset -= sg_page_count(piter->sg);
751 0 : piter->sg = sg_next(piter->sg);
752 0 : if (!--piter->__nents || !piter->sg)
753 : return false;
754 : }
755 :
756 : return true;
757 : }
758 : EXPORT_SYMBOL(__sg_page_iter_next);
759 :
760 : static int sg_dma_page_count(struct scatterlist *sg)
761 : {
762 0 : return PAGE_ALIGN(sg->offset + sg_dma_len(sg)) >> PAGE_SHIFT;
763 : }
764 :
765 0 : bool __sg_page_iter_dma_next(struct sg_dma_page_iter *dma_iter)
766 : {
767 0 : struct sg_page_iter *piter = &dma_iter->base;
768 :
769 0 : if (!piter->__nents || !piter->sg)
770 : return false;
771 :
772 0 : piter->sg_pgoffset += piter->__pg_advance;
773 0 : piter->__pg_advance = 1;
774 :
775 0 : while (piter->sg_pgoffset >= sg_dma_page_count(piter->sg)) {
776 0 : piter->sg_pgoffset -= sg_dma_page_count(piter->sg);
777 0 : piter->sg = sg_next(piter->sg);
778 0 : if (!--piter->__nents || !piter->sg)
779 : return false;
780 : }
781 :
782 : return true;
783 : }
784 : EXPORT_SYMBOL(__sg_page_iter_dma_next);
785 :
786 : /**
787 : * sg_miter_start - start mapping iteration over a sg list
788 : * @miter: sg mapping iter to be started
789 : * @sgl: sg list to iterate over
790 : * @nents: number of sg entries
791 : *
792 : * Description:
793 : * Starts mapping iterator @miter.
794 : *
795 : * Context:
796 : * Don't care.
797 : */
798 0 : void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
799 : unsigned int nents, unsigned int flags)
800 : {
801 0 : memset(miter, 0, sizeof(struct sg_mapping_iter));
802 :
803 0 : __sg_page_iter_start(&miter->piter, sgl, nents, 0);
804 0 : WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
805 0 : miter->__flags = flags;
806 0 : }
807 : EXPORT_SYMBOL(sg_miter_start);
808 :
809 0 : static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
810 : {
811 0 : if (!miter->__remaining) {
812 : struct scatterlist *sg;
813 :
814 0 : if (!__sg_page_iter_next(&miter->piter))
815 : return false;
816 :
817 0 : sg = miter->piter.sg;
818 :
819 0 : miter->__offset = miter->piter.sg_pgoffset ? 0 : sg->offset;
820 0 : miter->piter.sg_pgoffset += miter->__offset >> PAGE_SHIFT;
821 0 : miter->__offset &= PAGE_SIZE - 1;
822 0 : miter->__remaining = sg->offset + sg->length -
823 0 : (miter->piter.sg_pgoffset << PAGE_SHIFT) -
824 : miter->__offset;
825 0 : miter->__remaining = min_t(unsigned long, miter->__remaining,
826 : PAGE_SIZE - miter->__offset);
827 : }
828 :
829 : return true;
830 : }
831 :
832 : /**
833 : * sg_miter_skip - reposition mapping iterator
834 : * @miter: sg mapping iter to be skipped
835 : * @offset: number of bytes to plus the current location
836 : *
837 : * Description:
838 : * Sets the offset of @miter to its current location plus @offset bytes.
839 : * If mapping iterator @miter has been proceeded by sg_miter_next(), this
840 : * stops @miter.
841 : *
842 : * Context:
843 : * Don't care.
844 : *
845 : * Returns:
846 : * true if @miter contains the valid mapping. false if end of sg
847 : * list is reached.
848 : */
849 0 : bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
850 : {
851 0 : sg_miter_stop(miter);
852 :
853 0 : while (offset) {
854 : off_t consumed;
855 :
856 0 : if (!sg_miter_get_next_page(miter))
857 : return false;
858 :
859 0 : consumed = min_t(off_t, offset, miter->__remaining);
860 0 : miter->__offset += consumed;
861 0 : miter->__remaining -= consumed;
862 0 : offset -= consumed;
863 : }
864 :
865 : return true;
866 : }
867 : EXPORT_SYMBOL(sg_miter_skip);
868 :
869 : /**
870 : * sg_miter_next - proceed mapping iterator to the next mapping
871 : * @miter: sg mapping iter to proceed
872 : *
873 : * Description:
874 : * Proceeds @miter to the next mapping. @miter should have been started
875 : * using sg_miter_start(). On successful return, @miter->page,
876 : * @miter->addr and @miter->length point to the current mapping.
877 : *
878 : * Context:
879 : * May sleep if !SG_MITER_ATOMIC.
880 : *
881 : * Returns:
882 : * true if @miter contains the next mapping. false if end of sg
883 : * list is reached.
884 : */
885 0 : bool sg_miter_next(struct sg_mapping_iter *miter)
886 : {
887 0 : sg_miter_stop(miter);
888 :
889 : /*
890 : * Get to the next page if necessary.
891 : * __remaining, __offset is adjusted by sg_miter_stop
892 : */
893 0 : if (!sg_miter_get_next_page(miter))
894 : return false;
895 :
896 0 : miter->page = sg_page_iter_page(&miter->piter);
897 0 : miter->consumed = miter->length = miter->__remaining;
898 :
899 0 : if (miter->__flags & SG_MITER_ATOMIC)
900 0 : miter->addr = kmap_atomic(miter->page) + miter->__offset;
901 : else
902 0 : miter->addr = kmap(miter->page) + miter->__offset;
903 :
904 : return true;
905 : }
906 : EXPORT_SYMBOL(sg_miter_next);
907 :
908 : /**
909 : * sg_miter_stop - stop mapping iteration
910 : * @miter: sg mapping iter to be stopped
911 : *
912 : * Description:
913 : * Stops mapping iterator @miter. @miter should have been started
914 : * using sg_miter_start(). A stopped iteration can be resumed by
915 : * calling sg_miter_next() on it. This is useful when resources (kmap)
916 : * need to be released during iteration.
917 : *
918 : * Context:
919 : * Don't care otherwise.
920 : */
921 0 : void sg_miter_stop(struct sg_mapping_iter *miter)
922 : {
923 0 : WARN_ON(miter->consumed > miter->length);
924 :
925 : /* drop resources from the last iteration */
926 0 : if (miter->addr) {
927 0 : miter->__offset += miter->consumed;
928 0 : miter->__remaining -= miter->consumed;
929 :
930 0 : if (miter->__flags & SG_MITER_TO_SG)
931 : flush_dcache_page(miter->page);
932 :
933 0 : if (miter->__flags & SG_MITER_ATOMIC) {
934 0 : WARN_ON_ONCE(!pagefault_disabled());
935 0 : kunmap_atomic(miter->addr);
936 : } else
937 : kunmap(miter->page);
938 :
939 0 : miter->page = NULL;
940 0 : miter->addr = NULL;
941 0 : miter->length = 0;
942 0 : miter->consumed = 0;
943 : }
944 0 : }
945 : EXPORT_SYMBOL(sg_miter_stop);
946 :
947 : /**
948 : * sg_copy_buffer - Copy data between a linear buffer and an SG list
949 : * @sgl: The SG list
950 : * @nents: Number of SG entries
951 : * @buf: Where to copy from
952 : * @buflen: The number of bytes to copy
953 : * @skip: Number of bytes to skip before copying
954 : * @to_buffer: transfer direction (true == from an sg list to a
955 : * buffer, false == from a buffer to an sg list)
956 : *
957 : * Returns the number of copied bytes.
958 : *
959 : **/
960 0 : size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf,
961 : size_t buflen, off_t skip, bool to_buffer)
962 : {
963 0 : unsigned int offset = 0;
964 : struct sg_mapping_iter miter;
965 0 : unsigned int sg_flags = SG_MITER_ATOMIC;
966 :
967 0 : if (to_buffer)
968 : sg_flags |= SG_MITER_FROM_SG;
969 : else
970 0 : sg_flags |= SG_MITER_TO_SG;
971 :
972 0 : sg_miter_start(&miter, sgl, nents, sg_flags);
973 :
974 0 : if (!sg_miter_skip(&miter, skip))
975 : return 0;
976 :
977 0 : while ((offset < buflen) && sg_miter_next(&miter)) {
978 : unsigned int len;
979 :
980 0 : len = min(miter.length, buflen - offset);
981 :
982 0 : if (to_buffer)
983 0 : memcpy(buf + offset, miter.addr, len);
984 : else
985 0 : memcpy(miter.addr, buf + offset, len);
986 :
987 0 : offset += len;
988 : }
989 :
990 0 : sg_miter_stop(&miter);
991 :
992 0 : return offset;
993 : }
994 : EXPORT_SYMBOL(sg_copy_buffer);
995 :
996 : /**
997 : * sg_copy_from_buffer - Copy from a linear buffer to an SG list
998 : * @sgl: The SG list
999 : * @nents: Number of SG entries
1000 : * @buf: Where to copy from
1001 : * @buflen: The number of bytes to copy
1002 : *
1003 : * Returns the number of copied bytes.
1004 : *
1005 : **/
1006 0 : size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
1007 : const void *buf, size_t buflen)
1008 : {
1009 0 : return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false);
1010 : }
1011 : EXPORT_SYMBOL(sg_copy_from_buffer);
1012 :
1013 : /**
1014 : * sg_copy_to_buffer - Copy from an SG list to a linear buffer
1015 : * @sgl: The SG list
1016 : * @nents: Number of SG entries
1017 : * @buf: Where to copy to
1018 : * @buflen: The number of bytes to copy
1019 : *
1020 : * Returns the number of copied bytes.
1021 : *
1022 : **/
1023 0 : size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
1024 : void *buf, size_t buflen)
1025 : {
1026 0 : return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
1027 : }
1028 : EXPORT_SYMBOL(sg_copy_to_buffer);
1029 :
1030 : /**
1031 : * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
1032 : * @sgl: The SG list
1033 : * @nents: Number of SG entries
1034 : * @buf: Where to copy from
1035 : * @buflen: The number of bytes to copy
1036 : * @skip: Number of bytes to skip before copying
1037 : *
1038 : * Returns the number of copied bytes.
1039 : *
1040 : **/
1041 0 : size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
1042 : const void *buf, size_t buflen, off_t skip)
1043 : {
1044 0 : return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false);
1045 : }
1046 : EXPORT_SYMBOL(sg_pcopy_from_buffer);
1047 :
1048 : /**
1049 : * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
1050 : * @sgl: The SG list
1051 : * @nents: Number of SG entries
1052 : * @buf: Where to copy to
1053 : * @buflen: The number of bytes to copy
1054 : * @skip: Number of bytes to skip before copying
1055 : *
1056 : * Returns the number of copied bytes.
1057 : *
1058 : **/
1059 0 : size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
1060 : void *buf, size_t buflen, off_t skip)
1061 : {
1062 0 : return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
1063 : }
1064 : EXPORT_SYMBOL(sg_pcopy_to_buffer);
1065 :
1066 : /**
1067 : * sg_zero_buffer - Zero-out a part of a SG list
1068 : * @sgl: The SG list
1069 : * @nents: Number of SG entries
1070 : * @buflen: The number of bytes to zero out
1071 : * @skip: Number of bytes to skip before zeroing
1072 : *
1073 : * Returns the number of bytes zeroed.
1074 : **/
1075 0 : size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,
1076 : size_t buflen, off_t skip)
1077 : {
1078 0 : unsigned int offset = 0;
1079 : struct sg_mapping_iter miter;
1080 0 : unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;
1081 :
1082 0 : sg_miter_start(&miter, sgl, nents, sg_flags);
1083 :
1084 0 : if (!sg_miter_skip(&miter, skip))
1085 : return false;
1086 :
1087 0 : while (offset < buflen && sg_miter_next(&miter)) {
1088 : unsigned int len;
1089 :
1090 0 : len = min(miter.length, buflen - offset);
1091 0 : memset(miter.addr, 0, len);
1092 :
1093 0 : offset += len;
1094 : }
1095 :
1096 0 : sg_miter_stop(&miter);
1097 0 : return offset;
1098 : }
1099 : EXPORT_SYMBOL(sg_zero_buffer);
1100 :
1101 : /*
1102 : * Extract and pin a list of up to sg_max pages from UBUF- or IOVEC-class
1103 : * iterators, and add them to the scatterlist.
1104 : */
1105 0 : static ssize_t extract_user_to_sg(struct iov_iter *iter,
1106 : ssize_t maxsize,
1107 : struct sg_table *sgtable,
1108 : unsigned int sg_max,
1109 : iov_iter_extraction_t extraction_flags)
1110 : {
1111 0 : struct scatterlist *sg = sgtable->sgl + sgtable->nents;
1112 : struct page **pages;
1113 : unsigned int npages;
1114 0 : ssize_t ret = 0, res;
1115 : size_t len, off;
1116 :
1117 : /* We decant the page list into the tail of the scatterlist */
1118 0 : pages = (void *)sgtable->sgl +
1119 0 : array_size(sg_max, sizeof(struct scatterlist));
1120 0 : pages -= sg_max;
1121 :
1122 : do {
1123 0 : res = iov_iter_extract_pages(iter, &pages, maxsize, sg_max,
1124 : extraction_flags, &off);
1125 0 : if (res < 0)
1126 : goto failed;
1127 :
1128 0 : len = res;
1129 0 : maxsize -= len;
1130 0 : ret += len;
1131 0 : npages = DIV_ROUND_UP(off + len, PAGE_SIZE);
1132 0 : sg_max -= npages;
1133 :
1134 0 : for (; npages > 0; npages--) {
1135 0 : struct page *page = *pages;
1136 0 : size_t seg = min_t(size_t, PAGE_SIZE - off, len);
1137 :
1138 0 : *pages++ = NULL;
1139 0 : sg_set_page(sg, page, seg, off);
1140 0 : sgtable->nents++;
1141 0 : sg++;
1142 0 : len -= seg;
1143 0 : off = 0;
1144 : }
1145 0 : } while (maxsize > 0 && sg_max > 0);
1146 :
1147 : return ret;
1148 :
1149 : failed:
1150 0 : while (sgtable->nents > sgtable->orig_nents)
1151 0 : put_page(sg_page(&sgtable->sgl[--sgtable->nents]));
1152 : return res;
1153 : }
1154 :
1155 : /*
1156 : * Extract up to sg_max pages from a BVEC-type iterator and add them to the
1157 : * scatterlist. The pages are not pinned.
1158 : */
1159 0 : static ssize_t extract_bvec_to_sg(struct iov_iter *iter,
1160 : ssize_t maxsize,
1161 : struct sg_table *sgtable,
1162 : unsigned int sg_max,
1163 : iov_iter_extraction_t extraction_flags)
1164 : {
1165 0 : const struct bio_vec *bv = iter->bvec;
1166 0 : struct scatterlist *sg = sgtable->sgl + sgtable->nents;
1167 0 : unsigned long start = iter->iov_offset;
1168 : unsigned int i;
1169 0 : ssize_t ret = 0;
1170 :
1171 0 : for (i = 0; i < iter->nr_segs; i++) {
1172 : size_t off, len;
1173 :
1174 0 : len = bv[i].bv_len;
1175 0 : if (start >= len) {
1176 0 : start -= len;
1177 0 : continue;
1178 : }
1179 :
1180 0 : len = min_t(size_t, maxsize, len - start);
1181 0 : off = bv[i].bv_offset + start;
1182 :
1183 0 : sg_set_page(sg, bv[i].bv_page, len, off);
1184 0 : sgtable->nents++;
1185 0 : sg++;
1186 0 : sg_max--;
1187 :
1188 0 : ret += len;
1189 0 : maxsize -= len;
1190 0 : if (maxsize <= 0 || sg_max == 0)
1191 : break;
1192 : start = 0;
1193 : }
1194 :
1195 0 : if (ret > 0)
1196 0 : iov_iter_advance(iter, ret);
1197 0 : return ret;
1198 : }
1199 :
1200 : /*
1201 : * Extract up to sg_max pages from a KVEC-type iterator and add them to the
1202 : * scatterlist. This can deal with vmalloc'd buffers as well as kmalloc'd or
1203 : * static buffers. The pages are not pinned.
1204 : */
1205 0 : static ssize_t extract_kvec_to_sg(struct iov_iter *iter,
1206 : ssize_t maxsize,
1207 : struct sg_table *sgtable,
1208 : unsigned int sg_max,
1209 : iov_iter_extraction_t extraction_flags)
1210 : {
1211 0 : const struct kvec *kv = iter->kvec;
1212 0 : struct scatterlist *sg = sgtable->sgl + sgtable->nents;
1213 0 : unsigned long start = iter->iov_offset;
1214 : unsigned int i;
1215 0 : ssize_t ret = 0;
1216 :
1217 0 : for (i = 0; i < iter->nr_segs; i++) {
1218 : struct page *page;
1219 : unsigned long kaddr;
1220 : size_t off, len, seg;
1221 :
1222 0 : len = kv[i].iov_len;
1223 0 : if (start >= len) {
1224 0 : start -= len;
1225 0 : continue;
1226 : }
1227 :
1228 0 : kaddr = (unsigned long)kv[i].iov_base + start;
1229 0 : off = kaddr & ~PAGE_MASK;
1230 0 : len = min_t(size_t, maxsize, len - start);
1231 0 : kaddr &= PAGE_MASK;
1232 :
1233 0 : maxsize -= len;
1234 0 : ret += len;
1235 : do {
1236 0 : seg = min_t(size_t, len, PAGE_SIZE - off);
1237 0 : if (is_vmalloc_or_module_addr((void *)kaddr))
1238 0 : page = vmalloc_to_page((void *)kaddr);
1239 : else
1240 0 : page = virt_to_page((void *)kaddr);
1241 :
1242 0 : sg_set_page(sg, page, len, off);
1243 0 : sgtable->nents++;
1244 0 : sg++;
1245 0 : sg_max--;
1246 :
1247 0 : len -= seg;
1248 0 : kaddr += PAGE_SIZE;
1249 0 : off = 0;
1250 0 : } while (len > 0 && sg_max > 0);
1251 :
1252 0 : if (maxsize <= 0 || sg_max == 0)
1253 : break;
1254 : start = 0;
1255 : }
1256 :
1257 0 : if (ret > 0)
1258 0 : iov_iter_advance(iter, ret);
1259 0 : return ret;
1260 : }
1261 :
1262 : /*
1263 : * Extract up to sg_max folios from an XARRAY-type iterator and add them to
1264 : * the scatterlist. The pages are not pinned.
1265 : */
1266 0 : static ssize_t extract_xarray_to_sg(struct iov_iter *iter,
1267 : ssize_t maxsize,
1268 : struct sg_table *sgtable,
1269 : unsigned int sg_max,
1270 : iov_iter_extraction_t extraction_flags)
1271 : {
1272 0 : struct scatterlist *sg = sgtable->sgl + sgtable->nents;
1273 0 : struct xarray *xa = iter->xarray;
1274 : struct folio *folio;
1275 0 : loff_t start = iter->xarray_start + iter->iov_offset;
1276 0 : pgoff_t index = start / PAGE_SIZE;
1277 0 : ssize_t ret = 0;
1278 : size_t offset, len;
1279 0 : XA_STATE(xas, xa, index);
1280 :
1281 : rcu_read_lock();
1282 :
1283 0 : xas_for_each(&xas, folio, ULONG_MAX) {
1284 0 : if (xas_retry(&xas, folio))
1285 0 : continue;
1286 0 : if (WARN_ON(xa_is_value(folio)))
1287 : break;
1288 0 : if (WARN_ON(folio_test_hugetlb(folio)))
1289 : break;
1290 :
1291 0 : offset = offset_in_folio(folio, start);
1292 0 : len = min_t(size_t, maxsize, folio_size(folio) - offset);
1293 :
1294 0 : sg_set_page(sg, folio_page(folio, 0), len, offset);
1295 0 : sgtable->nents++;
1296 0 : sg++;
1297 0 : sg_max--;
1298 :
1299 0 : maxsize -= len;
1300 0 : ret += len;
1301 0 : if (maxsize <= 0 || sg_max == 0)
1302 : break;
1303 : }
1304 :
1305 : rcu_read_unlock();
1306 0 : if (ret > 0)
1307 0 : iov_iter_advance(iter, ret);
1308 0 : return ret;
1309 : }
1310 :
1311 : /**
1312 : * extract_iter_to_sg - Extract pages from an iterator and add to an sglist
1313 : * @iter: The iterator to extract from
1314 : * @maxsize: The amount of iterator to copy
1315 : * @sgtable: The scatterlist table to fill in
1316 : * @sg_max: Maximum number of elements in @sgtable that may be filled
1317 : * @extraction_flags: Flags to qualify the request
1318 : *
1319 : * Extract the page fragments from the given amount of the source iterator and
1320 : * add them to a scatterlist that refers to all of those bits, to a maximum
1321 : * addition of @sg_max elements.
1322 : *
1323 : * The pages referred to by UBUF- and IOVEC-type iterators are extracted and
1324 : * pinned; BVEC-, KVEC- and XARRAY-type are extracted but aren't pinned; PIPE-
1325 : * and DISCARD-type are not supported.
1326 : *
1327 : * No end mark is placed on the scatterlist; that's left to the caller.
1328 : *
1329 : * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
1330 : * be allowed on the pages extracted.
1331 : *
1332 : * If successful, @sgtable->nents is updated to include the number of elements
1333 : * added and the number of bytes added is returned. @sgtable->orig_nents is
1334 : * left unaltered.
1335 : *
1336 : * The iov_iter_extract_mode() function should be used to query how cleanup
1337 : * should be performed.
1338 : */
1339 0 : ssize_t extract_iter_to_sg(struct iov_iter *iter, size_t maxsize,
1340 : struct sg_table *sgtable, unsigned int sg_max,
1341 : iov_iter_extraction_t extraction_flags)
1342 : {
1343 0 : if (maxsize == 0)
1344 : return 0;
1345 :
1346 0 : switch (iov_iter_type(iter)) {
1347 : case ITER_UBUF:
1348 : case ITER_IOVEC:
1349 0 : return extract_user_to_sg(iter, maxsize, sgtable, sg_max,
1350 : extraction_flags);
1351 : case ITER_BVEC:
1352 0 : return extract_bvec_to_sg(iter, maxsize, sgtable, sg_max,
1353 : extraction_flags);
1354 : case ITER_KVEC:
1355 0 : return extract_kvec_to_sg(iter, maxsize, sgtable, sg_max,
1356 : extraction_flags);
1357 : case ITER_XARRAY:
1358 0 : return extract_xarray_to_sg(iter, maxsize, sgtable, sg_max,
1359 : extraction_flags);
1360 : default:
1361 0 : pr_err("%s(%u) unsupported\n", __func__, iov_iter_type(iter));
1362 0 : WARN_ON_ONCE(1);
1363 : return -EIO;
1364 : }
1365 : }
1366 : EXPORT_SYMBOL_GPL(extract_iter_to_sg);
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