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 #ifndef CONFIG_ARCH_HAS_SG_CHAIN
109 struct scatterlist
*ret
= &sgl
[nents
- 1];
111 struct scatterlist
*sg
, *ret
= NULL
;
114 for_each_sg(sgl
, sg
, nents
, i
)
118 #ifdef CONFIG_DEBUG_SG
119 BUG_ON(sgl
[0].sg_magic
!= SG_MAGIC
);
120 BUG_ON(!sg_is_last(ret
));
124 EXPORT_SYMBOL(sg_last
);
127 * sg_init_table - Initialize SG table
129 * @nents: Number of entries in table
132 * If this is part of a chained sg table, sg_mark_end() should be
133 * used only on the last table part.
136 void sg_init_table(struct scatterlist
*sgl
, unsigned int nents
)
138 memset(sgl
, 0, sizeof(*sgl
) * nents
);
139 #ifdef CONFIG_DEBUG_SG
142 for (i
= 0; i
< nents
; i
++)
143 sgl
[i
].sg_magic
= SG_MAGIC
;
146 sg_mark_end(&sgl
[nents
- 1]);
148 EXPORT_SYMBOL(sg_init_table
);
151 * sg_init_one - Initialize a single entry sg list
153 * @buf: Virtual address for IO
157 void sg_init_one(struct scatterlist
*sg
, const void *buf
, unsigned int buflen
)
159 sg_init_table(sg
, 1);
160 sg_set_buf(sg
, buf
, buflen
);
162 EXPORT_SYMBOL(sg_init_one
);
165 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
168 static struct scatterlist
*sg_kmalloc(unsigned int nents
, gfp_t gfp_mask
)
170 if (nents
== SG_MAX_SINGLE_ALLOC
) {
172 * Kmemleak doesn't track page allocations as they are not
173 * commonly used (in a raw form) for kernel data structures.
174 * As we chain together a list of pages and then a normal
175 * kmalloc (tracked by kmemleak), in order to for that last
176 * allocation not to become decoupled (and thus a
177 * false-positive) we need to inform kmemleak of all the
178 * intermediate allocations.
180 void *ptr
= (void *) __get_free_page(gfp_mask
);
181 kmemleak_alloc(ptr
, PAGE_SIZE
, 1, gfp_mask
);
184 return kmalloc(nents
* sizeof(struct scatterlist
), gfp_mask
);
187 static void sg_kfree(struct scatterlist
*sg
, unsigned int nents
)
189 if (nents
== SG_MAX_SINGLE_ALLOC
) {
191 free_page((unsigned long) sg
);
197 * __sg_free_table - Free a previously mapped sg table
198 * @table: The sg table header to use
199 * @max_ents: The maximum number of entries per single scatterlist
200 * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk
201 * @free_fn: Free function
204 * Free an sg table previously allocated and setup with
205 * __sg_alloc_table(). The @max_ents value must be identical to
206 * that previously used with __sg_alloc_table().
209 void __sg_free_table(struct sg_table
*table
, unsigned int max_ents
,
210 bool skip_first_chunk
, sg_free_fn
*free_fn
)
212 struct scatterlist
*sgl
, *next
;
214 if (unlikely(!table
->sgl
))
218 while (table
->orig_nents
) {
219 unsigned int alloc_size
= table
->orig_nents
;
220 unsigned int sg_size
;
223 * If we have more than max_ents segments left,
224 * then assign 'next' to the sg table after the current one.
225 * sg_size is then one less than alloc size, since the last
226 * element is the chain pointer.
228 if (alloc_size
> max_ents
) {
229 next
= sg_chain_ptr(&sgl
[max_ents
- 1]);
230 alloc_size
= max_ents
;
231 sg_size
= alloc_size
- 1;
233 sg_size
= alloc_size
;
237 table
->orig_nents
-= sg_size
;
238 if (skip_first_chunk
)
239 skip_first_chunk
= false;
241 free_fn(sgl
, alloc_size
);
247 EXPORT_SYMBOL(__sg_free_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
);
258 EXPORT_SYMBOL(sg_free_table
);
261 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
262 * @table: The sg table header to use
263 * @nents: Number of entries in sg list
264 * @max_ents: The maximum number of entries the allocator returns per call
265 * @gfp_mask: GFP allocation mask
266 * @alloc_fn: Allocator to use
269 * This function returns a @table @nents long. The allocator is
270 * defined to return scatterlist chunks of maximum size @max_ents.
271 * Thus if @nents is bigger than @max_ents, the scatterlists will be
272 * chained in units of @max_ents.
275 * If this function returns non-0 (eg failure), the caller must call
276 * __sg_free_table() to cleanup any leftover allocations.
279 int __sg_alloc_table(struct sg_table
*table
, unsigned int nents
,
280 unsigned int max_ents
, struct scatterlist
*first_chunk
,
281 gfp_t gfp_mask
, sg_alloc_fn
*alloc_fn
)
283 struct scatterlist
*sg
, *prv
;
286 memset(table
, 0, sizeof(*table
));
290 #ifndef CONFIG_ARCH_HAS_SG_CHAIN
291 if (WARN_ON_ONCE(nents
> max_ents
))
298 unsigned int sg_size
, alloc_size
= left
;
300 if (alloc_size
> max_ents
) {
301 alloc_size
= max_ents
;
302 sg_size
= alloc_size
- 1;
304 sg_size
= alloc_size
;
312 sg
= alloc_fn(alloc_size
, gfp_mask
);
316 * Adjust entry count to reflect that the last
317 * entry of the previous table won't be used for
318 * linkage. Without this, sg_kfree() may get
322 table
->nents
= ++table
->orig_nents
;
327 sg_init_table(sg
, alloc_size
);
328 table
->nents
= table
->orig_nents
+= sg_size
;
331 * If this is the first mapping, assign the sg table header.
332 * If this is not the first mapping, chain previous part.
335 sg_chain(prv
, max_ents
, sg
);
340 * If no more entries after this one, mark the end
343 sg_mark_end(&sg
[sg_size
- 1]);
350 EXPORT_SYMBOL(__sg_alloc_table
);
353 * sg_alloc_table - Allocate and initialize an sg table
354 * @table: The sg table header to use
355 * @nents: Number of entries in sg list
356 * @gfp_mask: GFP allocation mask
359 * Allocate and initialize an sg table. If @nents@ is larger than
360 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
363 int sg_alloc_table(struct sg_table
*table
, unsigned int nents
, gfp_t gfp_mask
)
367 ret
= __sg_alloc_table(table
, nents
, SG_MAX_SINGLE_ALLOC
,
368 NULL
, gfp_mask
, sg_kmalloc
);
370 __sg_free_table(table
, SG_MAX_SINGLE_ALLOC
, false, sg_kfree
);
374 EXPORT_SYMBOL(sg_alloc_table
);
377 * sg_alloc_table_from_pages - Allocate and initialize an sg table from
379 * @sgt: The sg table header to use
380 * @pages: Pointer to an array of page pointers
381 * @n_pages: Number of pages in the pages array
382 * @offset: Offset from start of the first page to the start of a buffer
383 * @size: Number of valid bytes in the buffer (after offset)
384 * @gfp_mask: GFP allocation mask
387 * Allocate and initialize an sg table from a list of pages. Contiguous
388 * ranges of the pages are squashed into a single scatterlist node. A user
389 * may provide an offset at a start and a size of valid data in a buffer
390 * specified by the page array. The returned sg table is released by
394 * 0 on success, negative error on failure
396 int sg_alloc_table_from_pages(struct sg_table
*sgt
,
397 struct page
**pages
, unsigned int n_pages
,
398 unsigned long offset
, unsigned long size
,
403 unsigned int cur_page
;
405 struct scatterlist
*s
;
407 /* compute number of contiguous chunks */
409 for (i
= 1; i
< n_pages
; ++i
)
410 if (page_to_pfn(pages
[i
]) != page_to_pfn(pages
[i
- 1]) + 1)
413 ret
= sg_alloc_table(sgt
, chunks
, gfp_mask
);
417 /* merging chunks and putting them into the scatterlist */
419 for_each_sg(sgt
->sgl
, s
, sgt
->orig_nents
, i
) {
420 unsigned long chunk_size
;
423 /* look for the end of the current chunk */
424 for (j
= cur_page
+ 1; j
< n_pages
; ++j
)
425 if (page_to_pfn(pages
[j
]) !=
426 page_to_pfn(pages
[j
- 1]) + 1)
429 chunk_size
= ((j
- cur_page
) << PAGE_SHIFT
) - offset
;
430 sg_set_page(s
, pages
[cur_page
], min(size
, chunk_size
), offset
);
438 EXPORT_SYMBOL(sg_alloc_table_from_pages
);
440 void __sg_page_iter_start(struct sg_page_iter
*piter
,
441 struct scatterlist
*sglist
, unsigned int nents
,
442 unsigned long pgoffset
)
444 piter
->__pg_advance
= 0;
445 piter
->__nents
= nents
;
448 piter
->sg_pgoffset
= pgoffset
;
450 EXPORT_SYMBOL(__sg_page_iter_start
);
452 static int sg_page_count(struct scatterlist
*sg
)
454 return PAGE_ALIGN(sg
->offset
+ sg
->length
) >> PAGE_SHIFT
;
457 bool __sg_page_iter_next(struct sg_page_iter
*piter
)
459 if (!piter
->__nents
|| !piter
->sg
)
462 piter
->sg_pgoffset
+= piter
->__pg_advance
;
463 piter
->__pg_advance
= 1;
465 while (piter
->sg_pgoffset
>= sg_page_count(piter
->sg
)) {
466 piter
->sg_pgoffset
-= sg_page_count(piter
->sg
);
467 piter
->sg
= sg_next(piter
->sg
);
468 if (!--piter
->__nents
|| !piter
->sg
)
474 EXPORT_SYMBOL(__sg_page_iter_next
);
477 * sg_miter_start - start mapping iteration over a sg list
478 * @miter: sg mapping iter to be started
479 * @sgl: sg list to iterate over
480 * @nents: number of sg entries
483 * Starts mapping iterator @miter.
488 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
489 unsigned int nents
, unsigned int flags
)
491 memset(miter
, 0, sizeof(struct sg_mapping_iter
));
493 __sg_page_iter_start(&miter
->piter
, sgl
, nents
, 0);
494 WARN_ON(!(flags
& (SG_MITER_TO_SG
| SG_MITER_FROM_SG
)));
495 miter
->__flags
= flags
;
497 EXPORT_SYMBOL(sg_miter_start
);
499 static bool sg_miter_get_next_page(struct sg_mapping_iter
*miter
)
501 if (!miter
->__remaining
) {
502 struct scatterlist
*sg
;
503 unsigned long pgoffset
;
505 if (!__sg_page_iter_next(&miter
->piter
))
508 sg
= miter
->piter
.sg
;
509 pgoffset
= miter
->piter
.sg_pgoffset
;
511 miter
->__offset
= pgoffset
? 0 : sg
->offset
;
512 miter
->__remaining
= sg
->offset
+ sg
->length
-
513 (pgoffset
<< PAGE_SHIFT
) - miter
->__offset
;
514 miter
->__remaining
= min_t(unsigned long, miter
->__remaining
,
515 PAGE_SIZE
- miter
->__offset
);
522 * sg_miter_skip - reposition mapping iterator
523 * @miter: sg mapping iter to be skipped
524 * @offset: number of bytes to plus the current location
527 * Sets the offset of @miter to its current location plus @offset bytes.
528 * If mapping iterator @miter has been proceeded by sg_miter_next(), this
532 * Don't care if @miter is stopped, or not proceeded yet.
533 * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
536 * true if @miter contains the valid mapping. false if end of sg
539 bool sg_miter_skip(struct sg_mapping_iter
*miter
, off_t offset
)
541 sg_miter_stop(miter
);
546 if (!sg_miter_get_next_page(miter
))
549 consumed
= min_t(off_t
, offset
, miter
->__remaining
);
550 miter
->__offset
+= consumed
;
551 miter
->__remaining
-= consumed
;
557 EXPORT_SYMBOL(sg_miter_skip
);
560 * sg_miter_next - proceed mapping iterator to the next mapping
561 * @miter: sg mapping iter to proceed
564 * Proceeds @miter to the next mapping. @miter should have been started
565 * using sg_miter_start(). On successful return, @miter->page,
566 * @miter->addr and @miter->length point to the current mapping.
569 * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled
570 * till @miter is stopped. May sleep if !SG_MITER_ATOMIC.
573 * true if @miter contains the next mapping. false if end of sg
576 bool sg_miter_next(struct sg_mapping_iter
*miter
)
578 sg_miter_stop(miter
);
581 * Get to the next page if necessary.
582 * __remaining, __offset is adjusted by sg_miter_stop
584 if (!sg_miter_get_next_page(miter
))
587 miter
->page
= sg_page_iter_page(&miter
->piter
);
588 miter
->consumed
= miter
->length
= miter
->__remaining
;
590 if (miter
->__flags
& SG_MITER_ATOMIC
)
591 miter
->addr
= kmap_atomic(miter
->page
) + miter
->__offset
;
593 miter
->addr
= kmap(miter
->page
) + miter
->__offset
;
597 EXPORT_SYMBOL(sg_miter_next
);
600 * sg_miter_stop - stop mapping iteration
601 * @miter: sg mapping iter to be stopped
604 * Stops mapping iterator @miter. @miter should have been started
605 * started using sg_miter_start(). A stopped iteration can be
606 * resumed by calling sg_miter_next() on it. This is useful when
607 * resources (kmap) need to be released during iteration.
610 * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care
613 void sg_miter_stop(struct sg_mapping_iter
*miter
)
615 WARN_ON(miter
->consumed
> miter
->length
);
617 /* drop resources from the last iteration */
619 miter
->__offset
+= miter
->consumed
;
620 miter
->__remaining
-= miter
->consumed
;
622 if ((miter
->__flags
& SG_MITER_TO_SG
) &&
623 !PageSlab(miter
->page
))
624 flush_kernel_dcache_page(miter
->page
);
626 if (miter
->__flags
& SG_MITER_ATOMIC
) {
627 WARN_ON_ONCE(preemptible());
628 kunmap_atomic(miter
->addr
);
638 EXPORT_SYMBOL(sg_miter_stop
);
641 * sg_copy_buffer - Copy data between a linear buffer and an SG list
643 * @nents: Number of SG entries
644 * @buf: Where to copy from
645 * @buflen: The number of bytes to copy
646 * @skip: Number of bytes to skip before copying
647 * @to_buffer: transfer direction (true == from an sg list to a
648 * buffer, false == from a buffer to an sg list
650 * Returns the number of copied bytes.
653 static size_t sg_copy_buffer(struct scatterlist
*sgl
, unsigned int nents
,
654 void *buf
, size_t buflen
, off_t skip
,
657 unsigned int offset
= 0;
658 struct sg_mapping_iter miter
;
660 unsigned int sg_flags
= SG_MITER_ATOMIC
;
663 sg_flags
|= SG_MITER_FROM_SG
;
665 sg_flags
|= SG_MITER_TO_SG
;
667 sg_miter_start(&miter
, sgl
, nents
, sg_flags
);
669 if (!sg_miter_skip(&miter
, skip
))
672 local_irq_save(flags
);
674 while (sg_miter_next(&miter
) && offset
< buflen
) {
677 len
= min(miter
.length
, buflen
- offset
);
680 memcpy(buf
+ offset
, miter
.addr
, len
);
682 memcpy(miter
.addr
, buf
+ offset
, len
);
687 sg_miter_stop(&miter
);
689 local_irq_restore(flags
);
694 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
696 * @nents: Number of SG entries
697 * @buf: Where to copy from
698 * @buflen: The number of bytes to copy
700 * Returns the number of copied bytes.
703 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
704 void *buf
, size_t buflen
)
706 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, 0, false);
708 EXPORT_SYMBOL(sg_copy_from_buffer
);
711 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
713 * @nents: Number of SG entries
714 * @buf: Where to copy to
715 * @buflen: The number of bytes to copy
717 * Returns the number of copied bytes.
720 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
721 void *buf
, size_t buflen
)
723 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, 0, true);
725 EXPORT_SYMBOL(sg_copy_to_buffer
);
728 * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
730 * @nents: Number of SG entries
731 * @buf: Where to copy from
732 * @skip: Number of bytes to skip before copying
733 * @buflen: The number of bytes to copy
735 * Returns the number of copied bytes.
738 size_t sg_pcopy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
739 void *buf
, size_t buflen
, off_t skip
)
741 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, skip
, false);
743 EXPORT_SYMBOL(sg_pcopy_from_buffer
);
746 * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
748 * @nents: Number of SG entries
749 * @buf: Where to copy to
750 * @skip: Number of bytes to skip before copying
751 * @buflen: The number of bytes to copy
753 * Returns the number of copied bytes.
756 size_t sg_pcopy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
757 void *buf
, size_t buflen
, off_t skip
)
759 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, skip
, true);
761 EXPORT_SYMBOL(sg_pcopy_to_buffer
);