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Jens Axboe0db92992007-11-30 09:16:50 +01001/*
2 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
3 *
4 * Scatterlist handling helpers.
5 *
6 * This source code is licensed under the GNU General Public License,
7 * Version 2. See the file COPYING for more details.
8 */
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -05009#include <linux/export.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090010#include <linux/slab.h>
Jens Axboe0db92992007-11-30 09:16:50 +010011#include <linux/scatterlist.h>
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +090012#include <linux/highmem.h>
Chris Wilsonb94de9b2010-07-28 22:59:02 +010013#include <linux/kmemleak.h>
Jens Axboe0db92992007-11-30 09:16:50 +010014
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 **/
25struct scatterlist *sg_next(struct scatterlist *sg)
26{
27#ifdef CONFIG_DEBUG_SG
28 BUG_ON(sg->sg_magic != SG_MAGIC);
29#endif
30 if (sg_is_last(sg))
31 return NULL;
32
33 sg++;
34 if (unlikely(sg_is_chain(sg)))
35 sg = sg_chain_ptr(sg);
36
37 return sg;
38}
39EXPORT_SYMBOL(sg_next);
40
41/**
42 * sg_last - return the last scatterlist entry in a list
43 * @sgl: First entry in the scatterlist
44 * @nents: Number of entries in the scatterlist
45 *
46 * Description:
47 * Should only be used casually, it (currently) scans the entire list
48 * to get the last entry.
49 *
50 * Note that the @sgl@ pointer passed in need not be the first one,
51 * the important bit is that @nents@ denotes the number of entries that
52 * exist from @sgl@.
53 *
54 **/
55struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
56{
57#ifndef ARCH_HAS_SG_CHAIN
58 struct scatterlist *ret = &sgl[nents - 1];
59#else
60 struct scatterlist *sg, *ret = NULL;
61 unsigned int i;
62
63 for_each_sg(sgl, sg, nents, i)
64 ret = sg;
65
66#endif
67#ifdef CONFIG_DEBUG_SG
68 BUG_ON(sgl[0].sg_magic != SG_MAGIC);
69 BUG_ON(!sg_is_last(ret));
70#endif
71 return ret;
72}
73EXPORT_SYMBOL(sg_last);
74
75/**
76 * sg_init_table - Initialize SG table
77 * @sgl: The SG table
78 * @nents: Number of entries in table
79 *
80 * Notes:
81 * If this is part of a chained sg table, sg_mark_end() should be
82 * used only on the last table part.
83 *
84 **/
85void sg_init_table(struct scatterlist *sgl, unsigned int nents)
86{
87 memset(sgl, 0, sizeof(*sgl) * nents);
88#ifdef CONFIG_DEBUG_SG
89 {
90 unsigned int i;
91 for (i = 0; i < nents; i++)
92 sgl[i].sg_magic = SG_MAGIC;
93 }
94#endif
95 sg_mark_end(&sgl[nents - 1]);
96}
97EXPORT_SYMBOL(sg_init_table);
98
99/**
100 * sg_init_one - Initialize a single entry sg list
101 * @sg: SG entry
102 * @buf: Virtual address for IO
103 * @buflen: IO length
104 *
105 **/
106void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
107{
108 sg_init_table(sg, 1);
109 sg_set_buf(sg, buf, buflen);
110}
111EXPORT_SYMBOL(sg_init_one);
112
113/*
114 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
115 * helpers.
116 */
117static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
118{
Chris Wilsonb94de9b2010-07-28 22:59:02 +0100119 if (nents == SG_MAX_SINGLE_ALLOC) {
120 /*
121 * Kmemleak doesn't track page allocations as they are not
122 * commonly used (in a raw form) for kernel data structures.
123 * As we chain together a list of pages and then a normal
124 * kmalloc (tracked by kmemleak), in order to for that last
125 * allocation not to become decoupled (and thus a
126 * false-positive) we need to inform kmemleak of all the
127 * intermediate allocations.
128 */
129 void *ptr = (void *) __get_free_page(gfp_mask);
130 kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask);
131 return ptr;
132 } else
Jens Axboe0db92992007-11-30 09:16:50 +0100133 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
134}
135
136static void sg_kfree(struct scatterlist *sg, unsigned int nents)
137{
Chris Wilsonb94de9b2010-07-28 22:59:02 +0100138 if (nents == SG_MAX_SINGLE_ALLOC) {
139 kmemleak_free(sg);
Jens Axboe0db92992007-11-30 09:16:50 +0100140 free_page((unsigned long) sg);
Chris Wilsonb94de9b2010-07-28 22:59:02 +0100141 } else
Jens Axboe0db92992007-11-30 09:16:50 +0100142 kfree(sg);
143}
144
145/**
146 * __sg_free_table - Free a previously mapped sg table
147 * @table: The sg table header to use
James Bottomley7cedb1f2008-01-13 14:15:28 -0600148 * @max_ents: The maximum number of entries per single scatterlist
Jens Axboe0db92992007-11-30 09:16:50 +0100149 * @free_fn: Free function
150 *
151 * Description:
James Bottomley7cedb1f2008-01-13 14:15:28 -0600152 * Free an sg table previously allocated and setup with
153 * __sg_alloc_table(). The @max_ents value must be identical to
154 * that previously used with __sg_alloc_table().
Jens Axboe0db92992007-11-30 09:16:50 +0100155 *
156 **/
James Bottomley7cedb1f2008-01-13 14:15:28 -0600157void __sg_free_table(struct sg_table *table, unsigned int max_ents,
158 sg_free_fn *free_fn)
Jens Axboe0db92992007-11-30 09:16:50 +0100159{
160 struct scatterlist *sgl, *next;
161
162 if (unlikely(!table->sgl))
163 return;
164
165 sgl = table->sgl;
166 while (table->orig_nents) {
167 unsigned int alloc_size = table->orig_nents;
168 unsigned int sg_size;
169
170 /*
James Bottomley7cedb1f2008-01-13 14:15:28 -0600171 * If we have more than max_ents segments left,
Jens Axboe0db92992007-11-30 09:16:50 +0100172 * then assign 'next' to the sg table after the current one.
173 * sg_size is then one less than alloc size, since the last
174 * element is the chain pointer.
175 */
James Bottomley7cedb1f2008-01-13 14:15:28 -0600176 if (alloc_size > max_ents) {
177 next = sg_chain_ptr(&sgl[max_ents - 1]);
178 alloc_size = max_ents;
Jens Axboe0db92992007-11-30 09:16:50 +0100179 sg_size = alloc_size - 1;
180 } else {
181 sg_size = alloc_size;
182 next = NULL;
183 }
184
185 table->orig_nents -= sg_size;
186 free_fn(sgl, alloc_size);
187 sgl = next;
188 }
189
190 table->sgl = NULL;
191}
192EXPORT_SYMBOL(__sg_free_table);
193
194/**
195 * sg_free_table - Free a previously allocated sg table
196 * @table: The mapped sg table header
197 *
198 **/
199void sg_free_table(struct sg_table *table)
200{
James Bottomley7cedb1f2008-01-13 14:15:28 -0600201 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
Jens Axboe0db92992007-11-30 09:16:50 +0100202}
203EXPORT_SYMBOL(sg_free_table);
204
205/**
206 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
207 * @table: The sg table header to use
208 * @nents: Number of entries in sg list
James Bottomley7cedb1f2008-01-13 14:15:28 -0600209 * @max_ents: The maximum number of entries the allocator returns per call
Jens Axboe0db92992007-11-30 09:16:50 +0100210 * @gfp_mask: GFP allocation mask
211 * @alloc_fn: Allocator to use
212 *
James Bottomley7cedb1f2008-01-13 14:15:28 -0600213 * Description:
214 * This function returns a @table @nents long. The allocator is
215 * defined to return scatterlist chunks of maximum size @max_ents.
216 * Thus if @nents is bigger than @max_ents, the scatterlists will be
217 * chained in units of @max_ents.
218 *
Jens Axboe0db92992007-11-30 09:16:50 +0100219 * Notes:
220 * If this function returns non-0 (eg failure), the caller must call
221 * __sg_free_table() to cleanup any leftover allocations.
222 *
223 **/
James Bottomley7cedb1f2008-01-13 14:15:28 -0600224int __sg_alloc_table(struct sg_table *table, unsigned int nents,
225 unsigned int max_ents, gfp_t gfp_mask,
Jens Axboe0db92992007-11-30 09:16:50 +0100226 sg_alloc_fn *alloc_fn)
227{
228 struct scatterlist *sg, *prv;
229 unsigned int left;
230
231#ifndef ARCH_HAS_SG_CHAIN
James Bottomley7cedb1f2008-01-13 14:15:28 -0600232 BUG_ON(nents > max_ents);
Jens Axboe0db92992007-11-30 09:16:50 +0100233#endif
234
235 memset(table, 0, sizeof(*table));
236
237 left = nents;
238 prv = NULL;
239 do {
240 unsigned int sg_size, alloc_size = left;
241
James Bottomley7cedb1f2008-01-13 14:15:28 -0600242 if (alloc_size > max_ents) {
243 alloc_size = max_ents;
Jens Axboe0db92992007-11-30 09:16:50 +0100244 sg_size = alloc_size - 1;
245 } else
246 sg_size = alloc_size;
247
248 left -= sg_size;
249
250 sg = alloc_fn(alloc_size, gfp_mask);
Jeffrey Carlyleedce6822010-08-30 19:55:09 +0200251 if (unlikely(!sg)) {
252 /*
253 * Adjust entry count to reflect that the last
254 * entry of the previous table won't be used for
255 * linkage. Without this, sg_kfree() may get
256 * confused.
257 */
258 if (prv)
259 table->nents = ++table->orig_nents;
260
261 return -ENOMEM;
262 }
Jens Axboe0db92992007-11-30 09:16:50 +0100263
264 sg_init_table(sg, alloc_size);
265 table->nents = table->orig_nents += sg_size;
266
267 /*
268 * If this is the first mapping, assign the sg table header.
269 * If this is not the first mapping, chain previous part.
270 */
271 if (prv)
James Bottomley7cedb1f2008-01-13 14:15:28 -0600272 sg_chain(prv, max_ents, sg);
Jens Axboe0db92992007-11-30 09:16:50 +0100273 else
274 table->sgl = sg;
275
276 /*
277 * If no more entries after this one, mark the end
278 */
279 if (!left)
280 sg_mark_end(&sg[sg_size - 1]);
281
Jens Axboe0db92992007-11-30 09:16:50 +0100282 prv = sg;
283 } while (left);
284
285 return 0;
286}
287EXPORT_SYMBOL(__sg_alloc_table);
288
289/**
290 * sg_alloc_table - Allocate and initialize an sg table
291 * @table: The sg table header to use
292 * @nents: Number of entries in sg list
293 * @gfp_mask: GFP allocation mask
294 *
295 * Description:
296 * Allocate and initialize an sg table. If @nents@ is larger than
297 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
298 *
299 **/
300int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
301{
302 int ret;
303
James Bottomley7cedb1f2008-01-13 14:15:28 -0600304 ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC,
305 gfp_mask, sg_kmalloc);
Jens Axboe0db92992007-11-30 09:16:50 +0100306 if (unlikely(ret))
James Bottomley7cedb1f2008-01-13 14:15:28 -0600307 __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree);
Jens Axboe0db92992007-11-30 09:16:50 +0100308
309 return ret;
310}
311EXPORT_SYMBOL(sg_alloc_table);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900312
313/**
Tomasz Stanislawskiefc42bc2012-06-18 09:25:01 +0200314 * sg_alloc_table_from_pages - Allocate and initialize an sg table from
315 * an array of pages
316 * @sgt: The sg table header to use
317 * @pages: Pointer to an array of page pointers
318 * @n_pages: Number of pages in the pages array
319 * @offset: Offset from start of the first page to the start of a buffer
320 * @size: Number of valid bytes in the buffer (after offset)
321 * @gfp_mask: GFP allocation mask
322 *
323 * Description:
324 * Allocate and initialize an sg table from a list of pages. Contiguous
325 * ranges of the pages are squashed into a single scatterlist node. A user
326 * may provide an offset at a start and a size of valid data in a buffer
327 * specified by the page array. The returned sg table is released by
328 * sg_free_table.
329 *
330 * Returns:
331 * 0 on success, negative error on failure
332 */
333int sg_alloc_table_from_pages(struct sg_table *sgt,
334 struct page **pages, unsigned int n_pages,
335 unsigned long offset, unsigned long size,
336 gfp_t gfp_mask)
337{
338 unsigned int chunks;
339 unsigned int i;
340 unsigned int cur_page;
341 int ret;
342 struct scatterlist *s;
343
344 /* compute number of contiguous chunks */
345 chunks = 1;
346 for (i = 1; i < n_pages; ++i)
347 if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
348 ++chunks;
349
350 ret = sg_alloc_table(sgt, chunks, gfp_mask);
351 if (unlikely(ret))
352 return ret;
353
354 /* merging chunks and putting them into the scatterlist */
355 cur_page = 0;
356 for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
357 unsigned long chunk_size;
358 unsigned int j;
359
360 /* look for the end of the current chunk */
361 for (j = cur_page + 1; j < n_pages; ++j)
362 if (page_to_pfn(pages[j]) !=
363 page_to_pfn(pages[j - 1]) + 1)
364 break;
365
366 chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
367 sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
368 size -= chunk_size;
369 offset = 0;
370 cur_page = j;
371 }
372
373 return 0;
374}
375EXPORT_SYMBOL(sg_alloc_table_from_pages);
376
377/**
Tejun Heo137d3ed2008-07-19 23:03:35 +0900378 * sg_miter_start - start mapping iteration over a sg list
379 * @miter: sg mapping iter to be started
380 * @sgl: sg list to iterate over
381 * @nents: number of sg entries
382 *
383 * Description:
384 * Starts mapping iterator @miter.
385 *
386 * Context:
387 * Don't care.
388 */
389void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl,
390 unsigned int nents, unsigned int flags)
391{
392 memset(miter, 0, sizeof(struct sg_mapping_iter));
393
394 miter->__sg = sgl;
395 miter->__nents = nents;
396 miter->__offset = 0;
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200397 WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG)));
Tejun Heo137d3ed2008-07-19 23:03:35 +0900398 miter->__flags = flags;
399}
400EXPORT_SYMBOL(sg_miter_start);
401
402/**
403 * sg_miter_next - proceed mapping iterator to the next mapping
404 * @miter: sg mapping iter to proceed
405 *
406 * Description:
407 * Proceeds @miter@ to the next mapping. @miter@ should have been
408 * started using sg_miter_start(). On successful return,
409 * @miter@->page, @miter@->addr and @miter@->length point to the
410 * current mapping.
411 *
412 * Context:
413 * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till
414 * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC.
415 *
416 * Returns:
417 * true if @miter contains the next mapping. false if end of sg
418 * list is reached.
419 */
420bool sg_miter_next(struct sg_mapping_iter *miter)
421{
422 unsigned int off, len;
423
424 /* check for end and drop resources from the last iteration */
425 if (!miter->__nents)
426 return false;
427
428 sg_miter_stop(miter);
429
430 /* get to the next sg if necessary. __offset is adjusted by stop */
Tejun Heo23c560a2009-04-15 22:10:23 +0900431 while (miter->__offset == miter->__sg->length) {
432 if (--miter->__nents) {
433 miter->__sg = sg_next(miter->__sg);
434 miter->__offset = 0;
435 } else
436 return false;
Tejun Heo137d3ed2008-07-19 23:03:35 +0900437 }
438
439 /* map the next page */
440 off = miter->__sg->offset + miter->__offset;
441 len = miter->__sg->length - miter->__offset;
442
443 miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT);
444 off &= ~PAGE_MASK;
445 miter->length = min_t(unsigned int, len, PAGE_SIZE - off);
446 miter->consumed = miter->length;
447
448 if (miter->__flags & SG_MITER_ATOMIC)
Cong Wangc3eede82011-11-25 23:14:39 +0800449 miter->addr = kmap_atomic(miter->page) + off;
Tejun Heo137d3ed2008-07-19 23:03:35 +0900450 else
451 miter->addr = kmap(miter->page) + off;
452
453 return true;
454}
455EXPORT_SYMBOL(sg_miter_next);
456
457/**
458 * sg_miter_stop - stop mapping iteration
459 * @miter: sg mapping iter to be stopped
460 *
461 * Description:
462 * Stops mapping iterator @miter. @miter should have been started
463 * started using sg_miter_start(). A stopped iteration can be
464 * resumed by calling sg_miter_next() on it. This is useful when
465 * resources (kmap) need to be released during iteration.
466 *
467 * Context:
468 * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise.
469 */
470void sg_miter_stop(struct sg_mapping_iter *miter)
471{
472 WARN_ON(miter->consumed > miter->length);
473
474 /* drop resources from the last iteration */
475 if (miter->addr) {
476 miter->__offset += miter->consumed;
477
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200478 if (miter->__flags & SG_MITER_TO_SG)
479 flush_kernel_dcache_page(miter->page);
480
Tejun Heo137d3ed2008-07-19 23:03:35 +0900481 if (miter->__flags & SG_MITER_ATOMIC) {
482 WARN_ON(!irqs_disabled());
Cong Wangc3eede82011-11-25 23:14:39 +0800483 kunmap_atomic(miter->addr);
Tejun Heo137d3ed2008-07-19 23:03:35 +0900484 } else
Arjan van de Venf652c522008-11-19 15:36:19 -0800485 kunmap(miter->page);
Tejun Heo137d3ed2008-07-19 23:03:35 +0900486
487 miter->page = NULL;
488 miter->addr = NULL;
489 miter->length = 0;
490 miter->consumed = 0;
491 }
492}
493EXPORT_SYMBOL(sg_miter_stop);
494
495/**
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900496 * sg_copy_buffer - Copy data between a linear buffer and an SG list
497 * @sgl: The SG list
498 * @nents: Number of SG entries
499 * @buf: Where to copy from
500 * @buflen: The number of bytes to copy
501 * @to_buffer: transfer direction (non zero == from an sg list to a
502 * buffer, 0 == from a buffer to an sg list
503 *
504 * Returns the number of copied bytes.
505 *
506 **/
507static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
508 void *buf, size_t buflen, int to_buffer)
509{
Tejun Heo137d3ed2008-07-19 23:03:35 +0900510 unsigned int offset = 0;
511 struct sg_mapping_iter miter;
FUJITA Tomonori50bed2e2008-09-11 18:35:39 +0200512 unsigned long flags;
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200513 unsigned int sg_flags = SG_MITER_ATOMIC;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900514
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200515 if (to_buffer)
516 sg_flags |= SG_MITER_FROM_SG;
517 else
518 sg_flags |= SG_MITER_TO_SG;
519
520 sg_miter_start(&miter, sgl, nents, sg_flags);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900521
FUJITA Tomonori50bed2e2008-09-11 18:35:39 +0200522 local_irq_save(flags);
523
Tejun Heo137d3ed2008-07-19 23:03:35 +0900524 while (sg_miter_next(&miter) && offset < buflen) {
525 unsigned int len;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900526
Tejun Heo137d3ed2008-07-19 23:03:35 +0900527 len = min(miter.length, buflen - offset);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900528
Tejun Heo137d3ed2008-07-19 23:03:35 +0900529 if (to_buffer)
530 memcpy(buf + offset, miter.addr, len);
Sebastian Andrzej Siewior6de7e3562009-06-18 10:19:12 +0200531 else
Tejun Heo137d3ed2008-07-19 23:03:35 +0900532 memcpy(miter.addr, buf + offset, len);
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900533
Tejun Heo137d3ed2008-07-19 23:03:35 +0900534 offset += len;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900535 }
536
Tejun Heo137d3ed2008-07-19 23:03:35 +0900537 sg_miter_stop(&miter);
538
FUJITA Tomonori50bed2e2008-09-11 18:35:39 +0200539 local_irq_restore(flags);
Tejun Heo137d3ed2008-07-19 23:03:35 +0900540 return offset;
FUJITA Tomonorib1adaf62008-03-18 00:15:03 +0900541}
542
543/**
544 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
545 * @sgl: The SG list
546 * @nents: Number of SG entries
547 * @buf: Where to copy from
548 * @buflen: The number of bytes to copy
549 *
550 * Returns the number of copied bytes.
551 *
552 **/
553size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
554 void *buf, size_t buflen)
555{
556 return sg_copy_buffer(sgl, nents, buf, buflen, 0);
557}
558EXPORT_SYMBOL(sg_copy_from_buffer);
559
560/**
561 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
562 * @sgl: The SG list
563 * @nents: Number of SG entries
564 * @buf: Where to copy to
565 * @buflen: The number of bytes to copy
566 *
567 * Returns the number of copied bytes.
568 *
569 **/
570size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
571 void *buf, size_t buflen)
572{
573 return sg_copy_buffer(sgl, nents, buf, buflen, 1);
574}
575EXPORT_SYMBOL(sg_copy_to_buffer);