2 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
4 * Scatterlist handling helpers.
6 * This source code is licensed under the GNU General Public License,
7 * Version 2. See the file COPYING for more details.
9 #include <linux/export.h>
10 #include <linux/slab.h>
11 #include <linux/scatterlist.h>
12 #include <linux/highmem.h>
13 #include <linux/kmemleak.h>
16 * sg_next - return the next scatterlist entry in a list
17 * @sg: The current sg entry
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
25 struct scatterlist
*sg_next(struct scatterlist
*sg
)
27 #ifdef CONFIG_DEBUG_SG
28 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
34 if (unlikely(sg_is_chain(sg
)))
35 sg
= sg_chain_ptr(sg
);
39 EXPORT_SYMBOL(sg_next
);
42 * sg_nents - return total count of entries in scatterlist
43 * @sg: The scatterlist
46 * Allows to know how many entries are in sg, taking into acount
50 int sg_nents(struct scatterlist
*sg
)
53 for (nents
= 0; sg
; sg
= sg_next(sg
))
57 EXPORT_SYMBOL(sg_nents
);
60 * sg_nents_for_len - return total count of entries in scatterlist
61 * needed to satisfy the supplied length
62 * @sg: The scatterlist
63 * @len: The total required length
66 * Determines the number of entries in sg that are required to meet
67 * the supplied length, taking into acount chaining as well
70 * the number of sg entries needed, negative error on failure
73 int sg_nents_for_len(struct scatterlist
*sg
, u64 len
)
81 for (nents
= 0, total
= 0; sg
; sg
= sg_next(sg
)) {
90 EXPORT_SYMBOL(sg_nents_for_len
);
93 * sg_last - return the last scatterlist entry in a list
94 * @sgl: First entry in the scatterlist
95 * @nents: Number of entries in the scatterlist
98 * Should only be used casually, it (currently) scans the entire list
99 * to get the last entry.
101 * Note that the @sgl@ pointer passed in need not be the first one,
102 * the important bit is that @nents@ denotes the number of entries that
106 struct scatterlist
*sg_last(struct scatterlist
*sgl
, unsigned int nents
)
108 struct scatterlist
*sg
, *ret
= NULL
;
111 for_each_sg(sgl
, sg
, nents
, i
)
114 #ifdef CONFIG_DEBUG_SG
115 BUG_ON(sgl
[0].sg_magic
!= SG_MAGIC
);
116 BUG_ON(!sg_is_last(ret
));
120 EXPORT_SYMBOL(sg_last
);
123 * sg_init_table - Initialize SG table
125 * @nents: Number of entries in table
128 * If this is part of a chained sg table, sg_mark_end() should be
129 * used only on the last table part.
132 void sg_init_table(struct scatterlist
*sgl
, unsigned int nents
)
134 memset(sgl
, 0, sizeof(*sgl
) * nents
);
135 sg_init_marker(sgl
, nents
);
137 EXPORT_SYMBOL(sg_init_table
);
140 * sg_init_one - Initialize a single entry sg list
142 * @buf: Virtual address for IO
146 void sg_init_one(struct scatterlist
*sg
, const void *buf
, unsigned int buflen
)
148 sg_init_table(sg
, 1);
149 sg_set_buf(sg
, buf
, buflen
);
151 EXPORT_SYMBOL(sg_init_one
);
154 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
157 static struct scatterlist
*sg_kmalloc(unsigned int nents
, gfp_t gfp_mask
)
159 if (nents
== SG_MAX_SINGLE_ALLOC
) {
161 * Kmemleak doesn't track page allocations as they are not
162 * commonly used (in a raw form) for kernel data structures.
163 * As we chain together a list of pages and then a normal
164 * kmalloc (tracked by kmemleak), in order to for that last
165 * allocation not to become decoupled (and thus a
166 * false-positive) we need to inform kmemleak of all the
167 * intermediate allocations.
169 void *ptr
= (void *) __get_free_page(gfp_mask
);
170 kmemleak_alloc(ptr
, PAGE_SIZE
, 1, gfp_mask
);
173 return kmalloc_array(nents
, sizeof(struct scatterlist
),
177 static void sg_kfree(struct scatterlist
*sg
, unsigned int nents
)
179 if (nents
== SG_MAX_SINGLE_ALLOC
) {
181 free_page((unsigned long) sg
);
187 * __sg_free_table - Free a previously mapped sg table
188 * @table: The sg table header to use
189 * @max_ents: The maximum number of entries per single scatterlist
190 * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk
191 * @free_fn: Free function
194 * Free an sg table previously allocated and setup with
195 * __sg_alloc_table(). The @max_ents value must be identical to
196 * that previously used with __sg_alloc_table().
199 void __sg_free_table(struct sg_table
*table
, unsigned int max_ents
,
200 bool skip_first_chunk
, sg_free_fn
*free_fn
)
202 struct scatterlist
*sgl
, *next
;
204 if (unlikely(!table
->sgl
))
208 while (table
->orig_nents
) {
209 unsigned int alloc_size
= table
->orig_nents
;
210 unsigned int sg_size
;
213 * If we have more than max_ents segments left,
214 * then assign 'next' to the sg table after the current one.
215 * sg_size is then one less than alloc size, since the last
216 * element is the chain pointer.
218 if (alloc_size
> max_ents
) {
219 next
= sg_chain_ptr(&sgl
[max_ents
- 1]);
220 alloc_size
= max_ents
;
221 sg_size
= alloc_size
- 1;
223 sg_size
= alloc_size
;
227 table
->orig_nents
-= sg_size
;
228 if (skip_first_chunk
)
229 skip_first_chunk
= false;
231 free_fn(sgl
, alloc_size
);
237 EXPORT_SYMBOL(__sg_free_table
);
240 * sg_free_table - Free a previously allocated sg table
241 * @table: The mapped sg table header
244 void sg_free_table(struct sg_table
*table
)
246 __sg_free_table(table
, SG_MAX_SINGLE_ALLOC
, false, sg_kfree
);
248 EXPORT_SYMBOL(sg_free_table
);
251 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
252 * @table: The sg table header to use
253 * @nents: Number of entries in sg list
254 * @max_ents: The maximum number of entries the allocator returns per call
255 * @gfp_mask: GFP allocation mask
256 * @alloc_fn: Allocator to use
259 * This function returns a @table @nents long. The allocator is
260 * defined to return scatterlist chunks of maximum size @max_ents.
261 * Thus if @nents is bigger than @max_ents, the scatterlists will be
262 * chained in units of @max_ents.
265 * If this function returns non-0 (eg failure), the caller must call
266 * __sg_free_table() to cleanup any leftover allocations.
269 int __sg_alloc_table(struct sg_table
*table
, unsigned int nents
,
270 unsigned int max_ents
, struct scatterlist
*first_chunk
,
271 gfp_t gfp_mask
, sg_alloc_fn
*alloc_fn
)
273 struct scatterlist
*sg
, *prv
;
276 memset(table
, 0, sizeof(*table
));
280 #ifndef CONFIG_ARCH_HAS_SG_CHAIN
281 if (WARN_ON_ONCE(nents
> max_ents
))
288 unsigned int sg_size
, alloc_size
= left
;
290 if (alloc_size
> max_ents
) {
291 alloc_size
= max_ents
;
292 sg_size
= alloc_size
- 1;
294 sg_size
= alloc_size
;
302 sg
= alloc_fn(alloc_size
, gfp_mask
);
306 * Adjust entry count to reflect that the last
307 * entry of the previous table won't be used for
308 * linkage. Without this, sg_kfree() may get
312 table
->nents
= ++table
->orig_nents
;
317 sg_init_table(sg
, alloc_size
);
318 table
->nents
= table
->orig_nents
+= sg_size
;
321 * If this is the first mapping, assign the sg table header.
322 * If this is not the first mapping, chain previous part.
325 sg_chain(prv
, max_ents
, sg
);
330 * If no more entries after this one, mark the end
333 sg_mark_end(&sg
[sg_size
- 1]);
340 EXPORT_SYMBOL(__sg_alloc_table
);
343 * sg_alloc_table - Allocate and initialize an sg table
344 * @table: The sg table header to use
345 * @nents: Number of entries in sg list
346 * @gfp_mask: GFP allocation mask
349 * Allocate and initialize an sg table. If @nents@ is larger than
350 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
353 int sg_alloc_table(struct sg_table
*table
, unsigned int nents
, gfp_t gfp_mask
)
357 ret
= __sg_alloc_table(table
, nents
, SG_MAX_SINGLE_ALLOC
,
358 NULL
, gfp_mask
, sg_kmalloc
);
360 __sg_free_table(table
, SG_MAX_SINGLE_ALLOC
, false, sg_kfree
);
364 EXPORT_SYMBOL(sg_alloc_table
);
367 * __sg_alloc_table_from_pages - Allocate and initialize an sg table from
369 * @sgt: The sg table header to use
370 * @pages: Pointer to an array of page pointers
371 * @n_pages: Number of pages in the pages array
372 * @offset: Offset from start of the first page to the start of a buffer
373 * @size: Number of valid bytes in the buffer (after offset)
374 * @max_segment: Maximum size of a scatterlist node in bytes (page aligned)
375 * @gfp_mask: GFP allocation mask
378 * Allocate and initialize an sg table from a list of pages. Contiguous
379 * ranges of the pages are squashed into a single scatterlist node up to the
380 * maximum size specified in @max_segment. An user may provide an offset at a
381 * start and a size of valid data in a buffer specified by the page array.
382 * The returned sg table is released by sg_free_table.
385 * 0 on success, negative error on failure
387 int __sg_alloc_table_from_pages(struct sg_table
*sgt
, struct page
**pages
,
388 unsigned int n_pages
, unsigned int offset
,
389 unsigned long size
, unsigned int max_segment
,
392 unsigned int chunks
, cur_page
, seg_len
, i
;
394 struct scatterlist
*s
;
396 if (WARN_ON(!max_segment
|| offset_in_page(max_segment
)))
399 /* compute number of contiguous chunks */
402 for (i
= 1; i
< n_pages
; i
++) {
403 seg_len
+= PAGE_SIZE
;
404 if (seg_len
>= max_segment
||
405 page_to_pfn(pages
[i
]) != page_to_pfn(pages
[i
- 1]) + 1) {
411 ret
= sg_alloc_table(sgt
, chunks
, gfp_mask
);
415 /* merging chunks and putting them into the scatterlist */
417 for_each_sg(sgt
->sgl
, s
, sgt
->orig_nents
, i
) {
418 unsigned int j
, chunk_size
;
420 /* look for the end of the current chunk */
422 for (j
= cur_page
+ 1; j
< n_pages
; j
++) {
423 seg_len
+= PAGE_SIZE
;
424 if (seg_len
>= max_segment
||
425 page_to_pfn(pages
[j
]) !=
426 page_to_pfn(pages
[j
- 1]) + 1)
430 chunk_size
= ((j
- cur_page
) << PAGE_SHIFT
) - offset
;
431 sg_set_page(s
, pages
[cur_page
],
432 min_t(unsigned long, size
, chunk_size
), offset
);
440 EXPORT_SYMBOL(__sg_alloc_table_from_pages
);
443 * sg_alloc_table_from_pages - Allocate and initialize an sg table from
445 * @sgt: The sg table header to use
446 * @pages: Pointer to an array of page pointers
447 * @n_pages: Number of pages in the pages array
448 * @offset: Offset from start of the first page to the start of a buffer
449 * @size: Number of valid bytes in the buffer (after offset)
450 * @gfp_mask: GFP allocation mask
453 * Allocate and initialize an sg table from a list of pages. Contiguous
454 * ranges of the pages are squashed into a single scatterlist node. A user
455 * may provide an offset at a start and a size of valid data in a buffer
456 * specified by the page array. The returned sg table is released by
460 * 0 on success, negative error on failure
462 int sg_alloc_table_from_pages(struct sg_table
*sgt
, struct page
**pages
,
463 unsigned int n_pages
, unsigned int offset
,
464 unsigned long size
, gfp_t gfp_mask
)
466 return __sg_alloc_table_from_pages(sgt
, pages
, n_pages
, offset
, size
,
467 SCATTERLIST_MAX_SEGMENT
, gfp_mask
);
469 EXPORT_SYMBOL(sg_alloc_table_from_pages
);
471 #ifdef CONFIG_SGL_ALLOC
474 * sgl_alloc_order - allocate a scatterlist and its pages
475 * @length: Length in bytes of the scatterlist. Must be at least one
476 * @order: Second argument for alloc_pages()
477 * @chainable: Whether or not to allocate an extra element in the scatterlist
478 * for scatterlist chaining purposes
479 * @gfp: Memory allocation flags
480 * @nent_p: [out] Number of entries in the scatterlist that have pages
482 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
484 struct scatterlist
*sgl_alloc_order(unsigned long long length
,
485 unsigned int order
, bool chainable
,
486 gfp_t gfp
, unsigned int *nent_p
)
488 struct scatterlist
*sgl
, *sg
;
490 unsigned int nent
, nalloc
;
493 nent
= round_up(length
, PAGE_SIZE
<< order
) >> (PAGE_SHIFT
+ order
);
494 /* Check for integer overflow */
495 if (length
> (nent
<< (PAGE_SHIFT
+ order
)))
499 /* Check for integer overflow */
500 if (nalloc
+ 1 < nalloc
)
504 sgl
= kmalloc_array(nalloc
, sizeof(struct scatterlist
),
505 (gfp
& ~GFP_DMA
) | __GFP_ZERO
);
509 sg_init_table(sgl
, nalloc
);
512 elem_len
= min_t(u64
, length
, PAGE_SIZE
<< order
);
513 page
= alloc_pages(gfp
, order
);
519 sg_set_page(sg
, page
, elem_len
, 0);
523 WARN_ONCE(length
, "length = %lld\n", length
);
528 EXPORT_SYMBOL(sgl_alloc_order
);
531 * sgl_alloc - allocate a scatterlist and its pages
532 * @length: Length in bytes of the scatterlist
533 * @gfp: Memory allocation flags
534 * @nent_p: [out] Number of entries in the scatterlist
536 * Returns: A pointer to an initialized scatterlist or %NULL upon failure.
538 struct scatterlist
*sgl_alloc(unsigned long long length
, gfp_t gfp
,
539 unsigned int *nent_p
)
541 return sgl_alloc_order(length
, 0, false, gfp
, nent_p
);
543 EXPORT_SYMBOL(sgl_alloc
);
546 * sgl_free_n_order - free a scatterlist and its pages
547 * @sgl: Scatterlist with one or more elements
548 * @nents: Maximum number of elements to free
549 * @order: Second argument for __free_pages()
552 * - If several scatterlists have been chained and each chain element is
553 * freed separately then it's essential to set nents correctly to avoid that a
554 * page would get freed twice.
555 * - All pages in a chained scatterlist can be freed at once by setting @nents
558 void sgl_free_n_order(struct scatterlist
*sgl
, int nents
, int order
)
560 struct scatterlist
*sg
;
564 for_each_sg(sgl
, sg
, nents
, i
) {
569 __free_pages(page
, order
);
573 EXPORT_SYMBOL(sgl_free_n_order
);
576 * sgl_free_order - free a scatterlist and its pages
577 * @sgl: Scatterlist with one or more elements
578 * @order: Second argument for __free_pages()
580 void sgl_free_order(struct scatterlist
*sgl
, int order
)
582 sgl_free_n_order(sgl
, INT_MAX
, order
);
584 EXPORT_SYMBOL(sgl_free_order
);
587 * sgl_free - free a scatterlist and its pages
588 * @sgl: Scatterlist with one or more elements
590 void sgl_free(struct scatterlist
*sgl
)
592 sgl_free_order(sgl
, 0);
594 EXPORT_SYMBOL(sgl_free
);
596 #endif /* CONFIG_SGL_ALLOC */
598 void __sg_page_iter_start(struct sg_page_iter
*piter
,
599 struct scatterlist
*sglist
, unsigned int nents
,
600 unsigned long pgoffset
)
602 piter
->__pg_advance
= 0;
603 piter
->__nents
= nents
;
606 piter
->sg_pgoffset
= pgoffset
;
608 EXPORT_SYMBOL(__sg_page_iter_start
);
610 static int sg_page_count(struct scatterlist
*sg
)
612 return PAGE_ALIGN(sg
->offset
+ sg
->length
) >> PAGE_SHIFT
;
615 bool __sg_page_iter_next(struct sg_page_iter
*piter
)
617 if (!piter
->__nents
|| !piter
->sg
)
620 piter
->sg_pgoffset
+= piter
->__pg_advance
;
621 piter
->__pg_advance
= 1;
623 while (piter
->sg_pgoffset
>= sg_page_count(piter
->sg
)) {
624 piter
->sg_pgoffset
-= sg_page_count(piter
->sg
);
625 piter
->sg
= sg_next(piter
->sg
);
626 if (!--piter
->__nents
|| !piter
->sg
)
632 EXPORT_SYMBOL(__sg_page_iter_next
);
635 * sg_miter_start - start mapping iteration over a sg list
636 * @miter: sg mapping iter to be started
637 * @sgl: sg list to iterate over
638 * @nents: number of sg entries
641 * Starts mapping iterator @miter.
646 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
647 unsigned int nents
, unsigned int flags
)
649 memset(miter
, 0, sizeof(struct sg_mapping_iter
));
651 __sg_page_iter_start(&miter
->piter
, sgl
, nents
, 0);
652 WARN_ON(!(flags
& (SG_MITER_TO_SG
| SG_MITER_FROM_SG
)));
653 miter
->__flags
= flags
;
655 EXPORT_SYMBOL(sg_miter_start
);
657 static bool sg_miter_get_next_page(struct sg_mapping_iter
*miter
)
659 if (!miter
->__remaining
) {
660 struct scatterlist
*sg
;
661 unsigned long pgoffset
;
663 if (!__sg_page_iter_next(&miter
->piter
))
666 sg
= miter
->piter
.sg
;
667 pgoffset
= miter
->piter
.sg_pgoffset
;
669 miter
->__offset
= pgoffset
? 0 : sg
->offset
;
670 miter
->__remaining
= sg
->offset
+ sg
->length
-
671 (pgoffset
<< PAGE_SHIFT
) - miter
->__offset
;
672 miter
->__remaining
= min_t(unsigned long, miter
->__remaining
,
673 PAGE_SIZE
- miter
->__offset
);
680 * sg_miter_skip - reposition mapping iterator
681 * @miter: sg mapping iter to be skipped
682 * @offset: number of bytes to plus the current location
685 * Sets the offset of @miter to its current location plus @offset bytes.
686 * If mapping iterator @miter has been proceeded by sg_miter_next(), this
690 * Don't care if @miter is stopped, or not proceeded yet.
691 * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
694 * true if @miter contains the valid mapping. false if end of sg
697 bool sg_miter_skip(struct sg_mapping_iter
*miter
, off_t offset
)
699 sg_miter_stop(miter
);
704 if (!sg_miter_get_next_page(miter
))
707 consumed
= min_t(off_t
, offset
, miter
->__remaining
);
708 miter
->__offset
+= consumed
;
709 miter
->__remaining
-= consumed
;
715 EXPORT_SYMBOL(sg_miter_skip
);
718 * sg_miter_next - proceed mapping iterator to the next mapping
719 * @miter: sg mapping iter to proceed
722 * Proceeds @miter to the next mapping. @miter should have been started
723 * using sg_miter_start(). On successful return, @miter->page,
724 * @miter->addr and @miter->length point to the current mapping.
727 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
728 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
731 * true if @miter contains the next mapping. false if end of sg
734 bool sg_miter_next(struct sg_mapping_iter
*miter
)
736 sg_miter_stop(miter
);
739 * Get to the next page if necessary.
740 * __remaining, __offset is adjusted by sg_miter_stop
742 if (!sg_miter_get_next_page(miter
))
745 miter
->page
= sg_page_iter_page(&miter
->piter
);
746 miter
->consumed
= miter
->length
= miter
->__remaining
;
748 if (miter
->__flags
& SG_MITER_ATOMIC
)
749 miter
->addr
= kmap_atomic(miter
->page
) + miter
->__offset
;
751 miter
->addr
= kmap(miter
->page
) + miter
->__offset
;
755 EXPORT_SYMBOL(sg_miter_next
);
758 * sg_miter_stop - stop mapping iteration
759 * @miter: sg mapping iter to be stopped
762 * Stops mapping iterator @miter. @miter should have been started
763 * using sg_miter_start(). A stopped iteration can be resumed by
764 * calling sg_miter_next() on it. This is useful when resources (kmap)
765 * need to be released during iteration.
768 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
771 void sg_miter_stop(struct sg_mapping_iter
*miter
)
773 WARN_ON(miter
->consumed
> miter
->length
);
775 /* drop resources from the last iteration */
777 miter
->__offset
+= miter
->consumed
;
778 miter
->__remaining
-= miter
->consumed
;
780 if ((miter
->__flags
& SG_MITER_TO_SG
) &&
781 !PageSlab(miter
->page
))
782 flush_kernel_dcache_page(miter
->page
);
784 if (miter
->__flags
& SG_MITER_ATOMIC
) {
785 WARN_ON_ONCE(preemptible());
786 kunmap_atomic(miter
->addr
);
796 EXPORT_SYMBOL(sg_miter_stop
);
799 * sg_copy_buffer - Copy data between a linear buffer and an SG list
801 * @nents: Number of SG entries
802 * @buf: Where to copy from
803 * @buflen: The number of bytes to copy
804 * @skip: Number of bytes to skip before copying
805 * @to_buffer: transfer direction (true == from an sg list to a
806 * buffer, false == from a buffer to an sg list
808 * Returns the number of copied bytes.
811 size_t sg_copy_buffer(struct scatterlist
*sgl
, unsigned int nents
, void *buf
,
812 size_t buflen
, off_t skip
, bool to_buffer
)
814 unsigned int offset
= 0;
815 struct sg_mapping_iter miter
;
816 unsigned int sg_flags
= SG_MITER_ATOMIC
;
819 sg_flags
|= SG_MITER_FROM_SG
;
821 sg_flags
|= SG_MITER_TO_SG
;
823 sg_miter_start(&miter
, sgl
, nents
, sg_flags
);
825 if (!sg_miter_skip(&miter
, skip
))
828 while ((offset
< buflen
) && sg_miter_next(&miter
)) {
831 len
= min(miter
.length
, buflen
- offset
);
834 memcpy(buf
+ offset
, miter
.addr
, len
);
836 memcpy(miter
.addr
, buf
+ offset
, len
);
841 sg_miter_stop(&miter
);
845 EXPORT_SYMBOL(sg_copy_buffer
);
848 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
850 * @nents: Number of SG entries
851 * @buf: Where to copy from
852 * @buflen: The number of bytes to copy
854 * Returns the number of copied bytes.
857 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
858 const void *buf
, size_t buflen
)
860 return sg_copy_buffer(sgl
, nents
, (void *)buf
, buflen
, 0, false);
862 EXPORT_SYMBOL(sg_copy_from_buffer
);
865 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
867 * @nents: Number of SG entries
868 * @buf: Where to copy to
869 * @buflen: The number of bytes to copy
871 * Returns the number of copied bytes.
874 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
875 void *buf
, size_t buflen
)
877 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, 0, true);
879 EXPORT_SYMBOL(sg_copy_to_buffer
);
882 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
884 * @nents: Number of SG entries
885 * @buf: Where to copy from
886 * @buflen: The number of bytes to copy
887 * @skip: Number of bytes to skip before copying
889 * Returns the number of copied bytes.
892 size_t sg_pcopy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
893 const void *buf
, size_t buflen
, off_t skip
)
895 return sg_copy_buffer(sgl
, nents
, (void *)buf
, buflen
, skip
, false);
897 EXPORT_SYMBOL(sg_pcopy_from_buffer
);
900 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
902 * @nents: Number of SG entries
903 * @buf: Where to copy to
904 * @buflen: The number of bytes to copy
905 * @skip: Number of bytes to skip before copying
907 * Returns the number of copied bytes.
910 size_t sg_pcopy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
911 void *buf
, size_t buflen
, off_t skip
)
913 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, skip
, true);
915 EXPORT_SYMBOL(sg_pcopy_to_buffer
);
918 * sg_zero_buffer - Zero-out a part of a SG list
920 * @nents: Number of SG entries
921 * @buflen: The number of bytes to zero out
922 * @skip: Number of bytes to skip before zeroing
924 * Returns the number of bytes zeroed.
926 size_t sg_zero_buffer(struct scatterlist
*sgl
, unsigned int nents
,
927 size_t buflen
, off_t skip
)
929 unsigned int offset
= 0;
930 struct sg_mapping_iter miter
;
931 unsigned int sg_flags
= SG_MITER_ATOMIC
| SG_MITER_TO_SG
;
933 sg_miter_start(&miter
, sgl
, nents
, sg_flags
);
935 if (!sg_miter_skip(&miter
, skip
))
938 while (offset
< buflen
&& sg_miter_next(&miter
)) {
941 len
= min(miter
.length
, buflen
- offset
);
942 memset(miter
.addr
, 0, len
);
947 sg_miter_stop(&miter
);
950 EXPORT_SYMBOL(sg_zero_buffer
);