1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
5 * Scatterlist handling helpers.
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>
14 * sg_next - return the next scatterlist entry in a list
15 * @sg: The current sg entry
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
23 struct scatterlist
*sg_next(struct scatterlist
*sg
)
29 if (unlikely(sg_is_chain(sg
)))
30 sg
= sg_chain_ptr(sg
);
34 EXPORT_SYMBOL(sg_next
);
37 * sg_nents - return total count of entries in scatterlist
38 * @sg: The scatterlist
41 * Allows to know how many entries are in sg, taking into account
45 int sg_nents(struct scatterlist
*sg
)
48 for (nents
= 0; sg
; sg
= sg_next(sg
))
52 EXPORT_SYMBOL(sg_nents
);
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
61 * Determines the number of entries in sg that are required to meet
62 * the supplied length, taking into account chaining as well
65 * the number of sg entries needed, negative error on failure
68 int sg_nents_for_len(struct scatterlist
*sg
, u64 len
)
76 for (nents
= 0, total
= 0; sg
; sg
= sg_next(sg
)) {
85 EXPORT_SYMBOL(sg_nents_for_len
);
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
93 * Should only be used casually, it (currently) scans the entire list
94 * to get the last entry.
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
101 struct scatterlist
*sg_last(struct scatterlist
*sgl
, unsigned int nents
)
103 struct scatterlist
*sg
, *ret
= NULL
;
106 for_each_sg(sgl
, sg
, nents
, i
)
109 BUG_ON(!sg_is_last(ret
));
112 EXPORT_SYMBOL(sg_last
);
115 * sg_init_table - Initialize SG table
117 * @nents: Number of entries in table
120 * If this is part of a chained sg table, sg_mark_end() should be
121 * used only on the last table part.
124 void sg_init_table(struct scatterlist
*sgl
, unsigned int nents
)
126 memset(sgl
, 0, sizeof(*sgl
) * nents
);
127 sg_init_marker(sgl
, nents
);
129 EXPORT_SYMBOL(sg_init_table
);
132 * sg_init_one - Initialize a single entry sg list
134 * @buf: Virtual address for IO
138 void sg_init_one(struct scatterlist
*sg
, const void *buf
, unsigned int buflen
)
140 sg_init_table(sg
, 1);
141 sg_set_buf(sg
, buf
, buflen
);
143 EXPORT_SYMBOL(sg_init_one
);
146 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
149 static struct scatterlist
*sg_kmalloc(unsigned int nents
, gfp_t gfp_mask
)
151 if (nents
== SG_MAX_SINGLE_ALLOC
) {
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.
161 void *ptr
= (void *) __get_free_page(gfp_mask
);
162 kmemleak_alloc(ptr
, PAGE_SIZE
, 1, gfp_mask
);
165 return kmalloc_array(nents
, sizeof(struct scatterlist
),
169 static void sg_kfree(struct scatterlist
*sg
, unsigned int nents
)
171 if (nents
== SG_MAX_SINGLE_ALLOC
) {
173 free_page((unsigned long) sg
);
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
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().
193 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
)
197 struct scatterlist
*sgl
, *next
;
198 unsigned curr_max_ents
= nents_first_chunk
?: max_ents
;
200 if (unlikely(!table
->sgl
))
205 unsigned int alloc_size
= num_ents
;
206 unsigned int sg_size
;
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.
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;
219 sg_size
= alloc_size
;
224 if (nents_first_chunk
)
225 nents_first_chunk
= 0;
227 free_fn(sgl
, alloc_size
);
229 curr_max_ents
= max_ents
;
234 EXPORT_SYMBOL(__sg_free_table
);
237 * sg_free_append_table - Free a previously allocated append sg table.
238 * @table: The mapped sg append table header
241 void sg_free_append_table(struct sg_append_table
*table
)
243 __sg_free_table(&table
->sgt
, SG_MAX_SINGLE_ALLOC
, false, sg_kfree
,
246 EXPORT_SYMBOL(sg_free_append_table
);
250 * sg_free_table - Free a previously allocated sg table
251 * @table: The mapped sg table header
254 void sg_free_table(struct sg_table
*table
)
256 __sg_free_table(table
, SG_MAX_SINGLE_ALLOC
, false, sg_kfree
,
259 EXPORT_SYMBOL(sg_free_table
);
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
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.
278 * If this function returns non-0 (eg failure), the caller must call
279 * __sg_free_table() to cleanup any leftover allocations.
282 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
)
287 struct scatterlist
*sg
, *prv
;
289 unsigned curr_max_ents
= nents_first_chunk
?: max_ents
;
290 unsigned prv_max_ents
;
292 memset(table
, 0, sizeof(*table
));
296 #ifdef CONFIG_ARCH_NO_SG_CHAIN
297 if (WARN_ON_ONCE(nents
> max_ents
))
304 unsigned int sg_size
, alloc_size
= left
;
306 if (alloc_size
> curr_max_ents
) {
307 alloc_size
= curr_max_ents
;
308 sg_size
= alloc_size
- 1;
310 sg_size
= alloc_size
;
318 sg
= alloc_fn(alloc_size
, gfp_mask
);
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
328 table
->nents
= ++table
->orig_nents
;
333 sg_init_table(sg
, alloc_size
);
334 table
->nents
= table
->orig_nents
+= sg_size
;
337 * If this is the first mapping, assign the sg table header.
338 * If this is not the first mapping, chain previous part.
341 sg_chain(prv
, prv_max_ents
, sg
);
346 * If no more entries after this one, mark the end
349 sg_mark_end(&sg
[sg_size
- 1]);
352 prv_max_ents
= curr_max_ents
;
353 curr_max_ents
= max_ents
;
358 EXPORT_SYMBOL(__sg_alloc_table
);
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
367 * Allocate and initialize an sg table. If @nents@ is larger than
368 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
371 int sg_alloc_table(struct sg_table
*table
, unsigned int nents
, gfp_t gfp_mask
)
375 ret
= __sg_alloc_table(table
, nents
, SG_MAX_SINGLE_ALLOC
,
376 NULL
, 0, gfp_mask
, sg_kmalloc
);
378 sg_free_table(table
);
381 EXPORT_SYMBOL(sg_alloc_table
);
383 static struct scatterlist
*get_next_sg(struct sg_append_table
*table
,
384 struct scatterlist
*cur
,
385 unsigned long needed_sges
,
388 struct scatterlist
*new_sg
, *next_sg
;
389 unsigned int alloc_size
;
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)
398 alloc_size
= min_t(unsigned long, needed_sges
, SG_MAX_SINGLE_ALLOC
);
399 new_sg
= sg_kmalloc(alloc_size
, gfp_mask
);
401 return ERR_PTR(-ENOMEM
);
402 sg_init_table(new_sg
, alloc_size
);
404 table
->total_nents
+= alloc_size
- 1;
405 __sg_chain(next_sg
, new_sg
);
407 table
->sgt
.sgl
= new_sg
;
408 table
->total_nents
= alloc_size
;
414 * sg_alloc_append_table_from_pages - Allocate and initialize an append sg
415 * table from an array of pages
416 * @sgt_append: The sg append table to use
417 * @pages: Pointer to an array of page pointers
418 * @n_pages: Number of pages in the pages array
419 * @offset: Offset from start of the first page to the start of a buffer
420 * @size: Number of valid bytes in the buffer (after offset)
421 * @max_segment: Maximum size of a scatterlist element in bytes
422 * @left_pages: Left pages caller have to set after this call
423 * @gfp_mask: GFP allocation mask
426 * In the first call it allocate and initialize an sg table from a list of
427 * pages, else reuse the scatterlist from sgt_append. Contiguous ranges of
428 * the pages are squashed into a single scatterlist entry up to the maximum
429 * size specified in @max_segment. A user may provide an offset at a start
430 * and a size of valid data in a buffer specified by the page array. The
431 * returned sg table is released by sg_free_append_table
434 * 0 on success, negative error on failure
437 * If this function returns non-0 (eg failure), the caller must call
438 * sg_free_append_table() to cleanup any leftover allocations.
440 * In the fist call, sgt_append must by initialized.
442 int sg_alloc_append_table_from_pages(struct sg_append_table
*sgt_append
,
443 struct page
**pages
, unsigned int n_pages
, unsigned int offset
,
444 unsigned long size
, unsigned int max_segment
,
445 unsigned int left_pages
, gfp_t gfp_mask
)
447 unsigned int chunks
, cur_page
, seg_len
, i
, prv_len
= 0;
448 unsigned int added_nents
= 0;
449 struct scatterlist
*s
= sgt_append
->prv
;
452 * The algorithm below requires max_segment to be aligned to PAGE_SIZE
453 * otherwise it can overshoot.
455 max_segment
= ALIGN_DOWN(max_segment
, PAGE_SIZE
);
456 if (WARN_ON(max_segment
< PAGE_SIZE
))
459 if (IS_ENABLED(CONFIG_ARCH_NO_SG_CHAIN
) && sgt_append
->prv
)
462 if (sgt_append
->prv
) {
463 unsigned long paddr
=
464 (page_to_pfn(sg_page(sgt_append
->prv
)) * PAGE_SIZE
+
465 sgt_append
->prv
->offset
+ sgt_append
->prv
->length
) /
471 /* Merge contiguous pages into the last SG */
472 prv_len
= sgt_append
->prv
->length
;
473 while (n_pages
&& page_to_pfn(pages
[0]) == paddr
) {
474 if (sgt_append
->prv
->length
+ PAGE_SIZE
> max_segment
)
476 sgt_append
->prv
->length
+= PAGE_SIZE
;
485 /* compute number of contiguous chunks */
488 for (i
= 1; i
< n_pages
; i
++) {
489 seg_len
+= PAGE_SIZE
;
490 if (seg_len
>= max_segment
||
491 page_to_pfn(pages
[i
]) != page_to_pfn(pages
[i
- 1]) + 1) {
497 /* merging chunks and putting them into the scatterlist */
499 for (i
= 0; i
< chunks
; i
++) {
500 unsigned int j
, chunk_size
;
502 /* look for the end of the current chunk */
504 for (j
= cur_page
+ 1; j
< n_pages
; j
++) {
505 seg_len
+= PAGE_SIZE
;
506 if (seg_len
>= max_segment
||
507 page_to_pfn(pages
[j
]) !=
508 page_to_pfn(pages
[j
- 1]) + 1)
512 /* Pass how many chunks might be left */
513 s
= get_next_sg(sgt_append
, s
, chunks
- i
+ left_pages
,
517 * Adjust entry length to be as before function was
521 sgt_append
->prv
->length
= prv_len
;
524 chunk_size
= ((j
- cur_page
) << PAGE_SHIFT
) - offset
;
525 sg_set_page(s
, pages
[cur_page
],
526 min_t(unsigned long, size
, chunk_size
), offset
);
532 sgt_append
->sgt
.nents
+= added_nents
;
533 sgt_append
->sgt
.orig_nents
= sgt_append
->sgt
.nents
;
540 EXPORT_SYMBOL(sg_alloc_append_table_from_pages
);
543 * sg_alloc_table_from_pages_segment - Allocate and initialize an sg table from
544 * an array of pages and given maximum
546 * @sgt: The sg table header to use
547 * @pages: Pointer to an array of page pointers
548 * @n_pages: Number of pages in the pages array
549 * @offset: Offset from start of the first page to the start of a buffer
550 * @size: Number of valid bytes in the buffer (after offset)
551 * @max_segment: Maximum size of a scatterlist element in bytes
552 * @gfp_mask: GFP allocation mask
555 * Allocate and initialize an sg table from a list of pages. Contiguous
556 * ranges of the pages are squashed into a single scatterlist node up to the
557 * maximum size specified in @max_segment. A user may provide an offset at a
558 * start and a size of valid data in a buffer specified by the page array.
560 * The returned sg table is released by sg_free_table.
563 * 0 on success, negative error on failure
565 int sg_alloc_table_from_pages_segment(struct sg_table
*sgt
, struct page
**pages
,
566 unsigned int n_pages
, unsigned int offset
,
567 unsigned long size
, unsigned int max_segment
,
570 struct sg_append_table append
= {};
573 err
= sg_alloc_append_table_from_pages(&append
, pages
, n_pages
, offset
,
574 size
, max_segment
, 0, gfp_mask
);
576 sg_free_append_table(&append
);
579 memcpy(sgt
, &append
.sgt
, sizeof(*sgt
));
580 WARN_ON(append
.total_nents
!= sgt
->orig_nents
);
583 EXPORT_SYMBOL(sg_alloc_table_from_pages_segment
);
585 #ifdef CONFIG_SGL_ALLOC
588 * sgl_alloc_order - allocate a scatterlist and its pages
589 * @length: Length in bytes of the scatterlist. Must be at least one
590 * @order: Second argument for alloc_pages()
591 * @chainable: Whether or not to allocate an extra element in the scatterlist
592 * for scatterlist chaining purposes
593 * @gfp: Memory allocation flags
594 * @nent_p: [out] Number of entries in the scatterlist that have pages
596 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
598 struct scatterlist
*sgl_alloc_order(unsigned long long length
,
599 unsigned int order
, bool chainable
,
600 gfp_t gfp
, unsigned int *nent_p
)
602 struct scatterlist
*sgl
, *sg
;
604 unsigned int nent
, nalloc
;
607 nent
= round_up(length
, PAGE_SIZE
<< order
) >> (PAGE_SHIFT
+ order
);
608 /* Check for integer overflow */
609 if (length
> (nent
<< (PAGE_SHIFT
+ order
)))
613 /* Check for integer overflow */
614 if (nalloc
+ 1 < nalloc
)
618 sgl
= kmalloc_array(nalloc
, sizeof(struct scatterlist
),
623 sg_init_table(sgl
, nalloc
);
626 elem_len
= min_t(u64
, length
, PAGE_SIZE
<< order
);
627 page
= alloc_pages(gfp
, order
);
629 sgl_free_order(sgl
, order
);
633 sg_set_page(sg
, page
, elem_len
, 0);
637 WARN_ONCE(length
, "length = %lld\n", length
);
642 EXPORT_SYMBOL(sgl_alloc_order
);
645 * sgl_alloc - allocate a scatterlist and its pages
646 * @length: Length in bytes of the scatterlist
647 * @gfp: Memory allocation flags
648 * @nent_p: [out] Number of entries in the scatterlist
650 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
652 struct scatterlist
*sgl_alloc(unsigned long long length
, gfp_t gfp
,
653 unsigned int *nent_p
)
655 return sgl_alloc_order(length
, 0, false, gfp
, nent_p
);
657 EXPORT_SYMBOL(sgl_alloc
);
660 * sgl_free_n_order - free a scatterlist and its pages
661 * @sgl: Scatterlist with one or more elements
662 * @nents: Maximum number of elements to free
663 * @order: Second argument for __free_pages()
666 * - If several scatterlists have been chained and each chain element is
667 * freed separately then it's essential to set nents correctly to avoid that a
668 * page would get freed twice.
669 * - All pages in a chained scatterlist can be freed at once by setting @nents
672 void sgl_free_n_order(struct scatterlist
*sgl
, int nents
, int order
)
674 struct scatterlist
*sg
;
678 for_each_sg(sgl
, sg
, nents
, i
) {
683 __free_pages(page
, order
);
687 EXPORT_SYMBOL(sgl_free_n_order
);
690 * sgl_free_order - free a scatterlist and its pages
691 * @sgl: Scatterlist with one or more elements
692 * @order: Second argument for __free_pages()
694 void sgl_free_order(struct scatterlist
*sgl
, int order
)
696 sgl_free_n_order(sgl
, INT_MAX
, order
);
698 EXPORT_SYMBOL(sgl_free_order
);
701 * sgl_free - free a scatterlist and its pages
702 * @sgl: Scatterlist with one or more elements
704 void sgl_free(struct scatterlist
*sgl
)
706 sgl_free_order(sgl
, 0);
708 EXPORT_SYMBOL(sgl_free
);
710 #endif /* CONFIG_SGL_ALLOC */
712 void __sg_page_iter_start(struct sg_page_iter
*piter
,
713 struct scatterlist
*sglist
, unsigned int nents
,
714 unsigned long pgoffset
)
716 piter
->__pg_advance
= 0;
717 piter
->__nents
= nents
;
720 piter
->sg_pgoffset
= pgoffset
;
722 EXPORT_SYMBOL(__sg_page_iter_start
);
724 static int sg_page_count(struct scatterlist
*sg
)
726 return PAGE_ALIGN(sg
->offset
+ sg
->length
) >> PAGE_SHIFT
;
729 bool __sg_page_iter_next(struct sg_page_iter
*piter
)
731 if (!piter
->__nents
|| !piter
->sg
)
734 piter
->sg_pgoffset
+= piter
->__pg_advance
;
735 piter
->__pg_advance
= 1;
737 while (piter
->sg_pgoffset
>= sg_page_count(piter
->sg
)) {
738 piter
->sg_pgoffset
-= sg_page_count(piter
->sg
);
739 piter
->sg
= sg_next(piter
->sg
);
740 if (!--piter
->__nents
|| !piter
->sg
)
746 EXPORT_SYMBOL(__sg_page_iter_next
);
748 static int sg_dma_page_count(struct scatterlist
*sg
)
750 return PAGE_ALIGN(sg
->offset
+ sg_dma_len(sg
)) >> PAGE_SHIFT
;
753 bool __sg_page_iter_dma_next(struct sg_dma_page_iter
*dma_iter
)
755 struct sg_page_iter
*piter
= &dma_iter
->base
;
757 if (!piter
->__nents
|| !piter
->sg
)
760 piter
->sg_pgoffset
+= piter
->__pg_advance
;
761 piter
->__pg_advance
= 1;
763 while (piter
->sg_pgoffset
>= sg_dma_page_count(piter
->sg
)) {
764 piter
->sg_pgoffset
-= sg_dma_page_count(piter
->sg
);
765 piter
->sg
= sg_next(piter
->sg
);
766 if (!--piter
->__nents
|| !piter
->sg
)
772 EXPORT_SYMBOL(__sg_page_iter_dma_next
);
775 * sg_miter_start - start mapping iteration over a sg list
776 * @miter: sg mapping iter to be started
777 * @sgl: sg list to iterate over
778 * @nents: number of sg entries
781 * Starts mapping iterator @miter.
786 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
787 unsigned int nents
, unsigned int flags
)
789 memset(miter
, 0, sizeof(struct sg_mapping_iter
));
791 __sg_page_iter_start(&miter
->piter
, sgl
, nents
, 0);
792 WARN_ON(!(flags
& (SG_MITER_TO_SG
| SG_MITER_FROM_SG
)));
793 miter
->__flags
= flags
;
795 EXPORT_SYMBOL(sg_miter_start
);
797 static bool sg_miter_get_next_page(struct sg_mapping_iter
*miter
)
799 if (!miter
->__remaining
) {
800 struct scatterlist
*sg
;
802 if (!__sg_page_iter_next(&miter
->piter
))
805 sg
= miter
->piter
.sg
;
807 miter
->__offset
= miter
->piter
.sg_pgoffset
? 0 : sg
->offset
;
808 miter
->piter
.sg_pgoffset
+= miter
->__offset
>> PAGE_SHIFT
;
809 miter
->__offset
&= PAGE_SIZE
- 1;
810 miter
->__remaining
= sg
->offset
+ sg
->length
-
811 (miter
->piter
.sg_pgoffset
<< PAGE_SHIFT
) -
813 miter
->__remaining
= min_t(unsigned long, miter
->__remaining
,
814 PAGE_SIZE
- miter
->__offset
);
821 * sg_miter_skip - reposition mapping iterator
822 * @miter: sg mapping iter to be skipped
823 * @offset: number of bytes to plus the current location
826 * Sets the offset of @miter to its current location plus @offset bytes.
827 * If mapping iterator @miter has been proceeded by sg_miter_next(), this
831 * Don't care if @miter is stopped, or not proceeded yet.
832 * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
835 * true if @miter contains the valid mapping. false if end of sg
838 bool sg_miter_skip(struct sg_mapping_iter
*miter
, off_t offset
)
840 sg_miter_stop(miter
);
845 if (!sg_miter_get_next_page(miter
))
848 consumed
= min_t(off_t
, offset
, miter
->__remaining
);
849 miter
->__offset
+= consumed
;
850 miter
->__remaining
-= consumed
;
856 EXPORT_SYMBOL(sg_miter_skip
);
859 * sg_miter_next - proceed mapping iterator to the next mapping
860 * @miter: sg mapping iter to proceed
863 * Proceeds @miter to the next mapping. @miter should have been started
864 * using sg_miter_start(). On successful return, @miter->page,
865 * @miter->addr and @miter->length point to the current mapping.
868 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
869 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
872 * true if @miter contains the next mapping. false if end of sg
875 bool sg_miter_next(struct sg_mapping_iter
*miter
)
877 sg_miter_stop(miter
);
880 * Get to the next page if necessary.
881 * __remaining, __offset is adjusted by sg_miter_stop
883 if (!sg_miter_get_next_page(miter
))
886 miter
->page
= sg_page_iter_page(&miter
->piter
);
887 miter
->consumed
= miter
->length
= miter
->__remaining
;
889 if (miter
->__flags
& SG_MITER_ATOMIC
)
890 miter
->addr
= kmap_atomic(miter
->page
) + miter
->__offset
;
892 miter
->addr
= kmap(miter
->page
) + miter
->__offset
;
896 EXPORT_SYMBOL(sg_miter_next
);
899 * sg_miter_stop - stop mapping iteration
900 * @miter: sg mapping iter to be stopped
903 * Stops mapping iterator @miter. @miter should have been started
904 * using sg_miter_start(). A stopped iteration can be resumed by
905 * calling sg_miter_next() on it. This is useful when resources (kmap)
906 * need to be released during iteration.
909 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
912 void sg_miter_stop(struct sg_mapping_iter
*miter
)
914 WARN_ON(miter
->consumed
> miter
->length
);
916 /* drop resources from the last iteration */
918 miter
->__offset
+= miter
->consumed
;
919 miter
->__remaining
-= miter
->consumed
;
921 if (miter
->__flags
& SG_MITER_TO_SG
)
922 flush_dcache_page(miter
->page
);
924 if (miter
->__flags
& SG_MITER_ATOMIC
) {
925 WARN_ON_ONCE(preemptible());
926 kunmap_atomic(miter
->addr
);
936 EXPORT_SYMBOL(sg_miter_stop
);
939 * sg_copy_buffer - Copy data between a linear buffer and an SG list
941 * @nents: Number of SG entries
942 * @buf: Where to copy from
943 * @buflen: The number of bytes to copy
944 * @skip: Number of bytes to skip before copying
945 * @to_buffer: transfer direction (true == from an sg list to a
946 * buffer, false == from a buffer to an sg list)
948 * Returns the number of copied bytes.
951 size_t sg_copy_buffer(struct scatterlist
*sgl
, unsigned int nents
, void *buf
,
952 size_t buflen
, off_t skip
, bool to_buffer
)
954 unsigned int offset
= 0;
955 struct sg_mapping_iter miter
;
956 unsigned int sg_flags
= SG_MITER_ATOMIC
;
959 sg_flags
|= SG_MITER_FROM_SG
;
961 sg_flags
|= SG_MITER_TO_SG
;
963 sg_miter_start(&miter
, sgl
, nents
, sg_flags
);
965 if (!sg_miter_skip(&miter
, skip
))
968 while ((offset
< buflen
) && sg_miter_next(&miter
)) {
971 len
= min(miter
.length
, buflen
- offset
);
974 memcpy(buf
+ offset
, miter
.addr
, len
);
976 memcpy(miter
.addr
, buf
+ offset
, len
);
981 sg_miter_stop(&miter
);
985 EXPORT_SYMBOL(sg_copy_buffer
);
988 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
990 * @nents: Number of SG entries
991 * @buf: Where to copy from
992 * @buflen: The number of bytes to copy
994 * Returns the number of copied bytes.
997 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
998 const void *buf
, size_t buflen
)
1000 return sg_copy_buffer(sgl
, nents
, (void *)buf
, buflen
, 0, false);
1002 EXPORT_SYMBOL(sg_copy_from_buffer
);
1005 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
1007 * @nents: Number of SG entries
1008 * @buf: Where to copy to
1009 * @buflen: The number of bytes to copy
1011 * Returns the number of copied bytes.
1014 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
1015 void *buf
, size_t buflen
)
1017 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, 0, true);
1019 EXPORT_SYMBOL(sg_copy_to_buffer
);
1022 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
1024 * @nents: Number of SG entries
1025 * @buf: Where to copy from
1026 * @buflen: The number of bytes to copy
1027 * @skip: Number of bytes to skip before copying
1029 * Returns the number of copied bytes.
1032 size_t sg_pcopy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
1033 const void *buf
, size_t buflen
, off_t skip
)
1035 return sg_copy_buffer(sgl
, nents
, (void *)buf
, buflen
, skip
, false);
1037 EXPORT_SYMBOL(sg_pcopy_from_buffer
);
1040 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
1042 * @nents: Number of SG entries
1043 * @buf: Where to copy to
1044 * @buflen: The number of bytes to copy
1045 * @skip: Number of bytes to skip before copying
1047 * Returns the number of copied bytes.
1050 size_t sg_pcopy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
1051 void *buf
, size_t buflen
, off_t skip
)
1053 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, skip
, true);
1055 EXPORT_SYMBOL(sg_pcopy_to_buffer
);
1058 * sg_zero_buffer - Zero-out a part of a SG list
1060 * @nents: Number of SG entries
1061 * @buflen: The number of bytes to zero out
1062 * @skip: Number of bytes to skip before zeroing
1064 * Returns the number of bytes zeroed.
1066 size_t sg_zero_buffer(struct scatterlist
*sgl
, unsigned int nents
,
1067 size_t buflen
, off_t skip
)
1069 unsigned int offset
= 0;
1070 struct sg_mapping_iter miter
;
1071 unsigned int sg_flags
= SG_MITER_ATOMIC
| SG_MITER_TO_SG
;
1073 sg_miter_start(&miter
, sgl
, nents
, sg_flags
);
1075 if (!sg_miter_skip(&miter
, skip
))
1078 while (offset
< buflen
&& sg_miter_next(&miter
)) {
1081 len
= min(miter
.length
, buflen
- offset
);
1082 memset(miter
.addr
, 0, len
);
1087 sg_miter_stop(&miter
);
1090 EXPORT_SYMBOL(sg_zero_buffer
);