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0db9299f JA |
1 | /* |
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 | */ | |
9 | #include <linux/module.h> | |
5a0e3ad6 | 10 | #include <linux/slab.h> |
0db9299f | 11 | #include <linux/scatterlist.h> |
b1adaf65 | 12 | #include <linux/highmem.h> |
0db9299f JA |
13 | |
14 | /** | |
15 | * sg_next - return the next scatterlist entry in a list | |
16 | * @sg: The current sg entry | |
17 | * | |
18 | * Description: | |
19 | * Usually the next entry will be @sg@ + 1, but if this sg element is part | |
20 | * of a chained scatterlist, it could jump to the start of a new | |
21 | * scatterlist array. | |
22 | * | |
23 | **/ | |
24 | struct scatterlist *sg_next(struct scatterlist *sg) | |
25 | { | |
26 | #ifdef CONFIG_DEBUG_SG | |
27 | BUG_ON(sg->sg_magic != SG_MAGIC); | |
28 | #endif | |
29 | if (sg_is_last(sg)) | |
30 | return NULL; | |
31 | ||
32 | sg++; | |
33 | if (unlikely(sg_is_chain(sg))) | |
34 | sg = sg_chain_ptr(sg); | |
35 | ||
36 | return sg; | |
37 | } | |
38 | EXPORT_SYMBOL(sg_next); | |
39 | ||
40 | /** | |
41 | * sg_last - return the last scatterlist entry in a list | |
42 | * @sgl: First entry in the scatterlist | |
43 | * @nents: Number of entries in the scatterlist | |
44 | * | |
45 | * Description: | |
46 | * Should only be used casually, it (currently) scans the entire list | |
47 | * to get the last entry. | |
48 | * | |
49 | * Note that the @sgl@ pointer passed in need not be the first one, | |
50 | * the important bit is that @nents@ denotes the number of entries that | |
51 | * exist from @sgl@. | |
52 | * | |
53 | **/ | |
54 | struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) | |
55 | { | |
56 | #ifndef ARCH_HAS_SG_CHAIN | |
57 | struct scatterlist *ret = &sgl[nents - 1]; | |
58 | #else | |
59 | struct scatterlist *sg, *ret = NULL; | |
60 | unsigned int i; | |
61 | ||
62 | for_each_sg(sgl, sg, nents, i) | |
63 | ret = sg; | |
64 | ||
65 | #endif | |
66 | #ifdef CONFIG_DEBUG_SG | |
67 | BUG_ON(sgl[0].sg_magic != SG_MAGIC); | |
68 | BUG_ON(!sg_is_last(ret)); | |
69 | #endif | |
70 | return ret; | |
71 | } | |
72 | EXPORT_SYMBOL(sg_last); | |
73 | ||
74 | /** | |
75 | * sg_init_table - Initialize SG table | |
76 | * @sgl: The SG table | |
77 | * @nents: Number of entries in table | |
78 | * | |
79 | * Notes: | |
80 | * If this is part of a chained sg table, sg_mark_end() should be | |
81 | * used only on the last table part. | |
82 | * | |
83 | **/ | |
84 | void sg_init_table(struct scatterlist *sgl, unsigned int nents) | |
85 | { | |
86 | memset(sgl, 0, sizeof(*sgl) * nents); | |
87 | #ifdef CONFIG_DEBUG_SG | |
88 | { | |
89 | unsigned int i; | |
90 | for (i = 0; i < nents; i++) | |
91 | sgl[i].sg_magic = SG_MAGIC; | |
92 | } | |
93 | #endif | |
94 | sg_mark_end(&sgl[nents - 1]); | |
95 | } | |
96 | EXPORT_SYMBOL(sg_init_table); | |
97 | ||
98 | /** | |
99 | * sg_init_one - Initialize a single entry sg list | |
100 | * @sg: SG entry | |
101 | * @buf: Virtual address for IO | |
102 | * @buflen: IO length | |
103 | * | |
104 | **/ | |
105 | void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) | |
106 | { | |
107 | sg_init_table(sg, 1); | |
108 | sg_set_buf(sg, buf, buflen); | |
109 | } | |
110 | EXPORT_SYMBOL(sg_init_one); | |
111 | ||
112 | /* | |
113 | * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree | |
114 | * helpers. | |
115 | */ | |
116 | static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) | |
117 | { | |
118 | if (nents == SG_MAX_SINGLE_ALLOC) | |
119 | return (struct scatterlist *) __get_free_page(gfp_mask); | |
120 | else | |
121 | return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); | |
122 | } | |
123 | ||
124 | static void sg_kfree(struct scatterlist *sg, unsigned int nents) | |
125 | { | |
126 | if (nents == SG_MAX_SINGLE_ALLOC) | |
127 | free_page((unsigned long) sg); | |
128 | else | |
129 | kfree(sg); | |
130 | } | |
131 | ||
132 | /** | |
133 | * __sg_free_table - Free a previously mapped sg table | |
134 | * @table: The sg table header to use | |
7cedb1f1 | 135 | * @max_ents: The maximum number of entries per single scatterlist |
0db9299f JA |
136 | * @free_fn: Free function |
137 | * | |
138 | * Description: | |
7cedb1f1 JB |
139 | * Free an sg table previously allocated and setup with |
140 | * __sg_alloc_table(). The @max_ents value must be identical to | |
141 | * that previously used with __sg_alloc_table(). | |
0db9299f JA |
142 | * |
143 | **/ | |
7cedb1f1 JB |
144 | void __sg_free_table(struct sg_table *table, unsigned int max_ents, |
145 | sg_free_fn *free_fn) | |
0db9299f JA |
146 | { |
147 | struct scatterlist *sgl, *next; | |
148 | ||
149 | if (unlikely(!table->sgl)) | |
150 | return; | |
151 | ||
152 | sgl = table->sgl; | |
153 | while (table->orig_nents) { | |
154 | unsigned int alloc_size = table->orig_nents; | |
155 | unsigned int sg_size; | |
156 | ||
157 | /* | |
7cedb1f1 | 158 | * If we have more than max_ents segments left, |
0db9299f JA |
159 | * then assign 'next' to the sg table after the current one. |
160 | * sg_size is then one less than alloc size, since the last | |
161 | * element is the chain pointer. | |
162 | */ | |
7cedb1f1 JB |
163 | if (alloc_size > max_ents) { |
164 | next = sg_chain_ptr(&sgl[max_ents - 1]); | |
165 | alloc_size = max_ents; | |
0db9299f JA |
166 | sg_size = alloc_size - 1; |
167 | } else { | |
168 | sg_size = alloc_size; | |
169 | next = NULL; | |
170 | } | |
171 | ||
172 | table->orig_nents -= sg_size; | |
173 | free_fn(sgl, alloc_size); | |
174 | sgl = next; | |
175 | } | |
176 | ||
177 | table->sgl = NULL; | |
178 | } | |
179 | EXPORT_SYMBOL(__sg_free_table); | |
180 | ||
181 | /** | |
182 | * sg_free_table - Free a previously allocated sg table | |
183 | * @table: The mapped sg table header | |
184 | * | |
185 | **/ | |
186 | void sg_free_table(struct sg_table *table) | |
187 | { | |
7cedb1f1 | 188 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
189 | } |
190 | EXPORT_SYMBOL(sg_free_table); | |
191 | ||
192 | /** | |
193 | * __sg_alloc_table - Allocate and initialize an sg table with given allocator | |
194 | * @table: The sg table header to use | |
195 | * @nents: Number of entries in sg list | |
7cedb1f1 | 196 | * @max_ents: The maximum number of entries the allocator returns per call |
0db9299f JA |
197 | * @gfp_mask: GFP allocation mask |
198 | * @alloc_fn: Allocator to use | |
199 | * | |
7cedb1f1 JB |
200 | * Description: |
201 | * This function returns a @table @nents long. The allocator is | |
202 | * defined to return scatterlist chunks of maximum size @max_ents. | |
203 | * Thus if @nents is bigger than @max_ents, the scatterlists will be | |
204 | * chained in units of @max_ents. | |
205 | * | |
0db9299f JA |
206 | * Notes: |
207 | * If this function returns non-0 (eg failure), the caller must call | |
208 | * __sg_free_table() to cleanup any leftover allocations. | |
209 | * | |
210 | **/ | |
7cedb1f1 JB |
211 | int __sg_alloc_table(struct sg_table *table, unsigned int nents, |
212 | unsigned int max_ents, gfp_t gfp_mask, | |
0db9299f JA |
213 | sg_alloc_fn *alloc_fn) |
214 | { | |
215 | struct scatterlist *sg, *prv; | |
216 | unsigned int left; | |
217 | ||
218 | #ifndef ARCH_HAS_SG_CHAIN | |
7cedb1f1 | 219 | BUG_ON(nents > max_ents); |
0db9299f JA |
220 | #endif |
221 | ||
222 | memset(table, 0, sizeof(*table)); | |
223 | ||
224 | left = nents; | |
225 | prv = NULL; | |
226 | do { | |
227 | unsigned int sg_size, alloc_size = left; | |
228 | ||
7cedb1f1 JB |
229 | if (alloc_size > max_ents) { |
230 | alloc_size = max_ents; | |
0db9299f JA |
231 | sg_size = alloc_size - 1; |
232 | } else | |
233 | sg_size = alloc_size; | |
234 | ||
235 | left -= sg_size; | |
236 | ||
237 | sg = alloc_fn(alloc_size, gfp_mask); | |
238 | if (unlikely(!sg)) | |
239 | return -ENOMEM; | |
240 | ||
241 | sg_init_table(sg, alloc_size); | |
242 | table->nents = table->orig_nents += sg_size; | |
243 | ||
244 | /* | |
245 | * If this is the first mapping, assign the sg table header. | |
246 | * If this is not the first mapping, chain previous part. | |
247 | */ | |
248 | if (prv) | |
7cedb1f1 | 249 | sg_chain(prv, max_ents, sg); |
0db9299f JA |
250 | else |
251 | table->sgl = sg; | |
252 | ||
253 | /* | |
254 | * If no more entries after this one, mark the end | |
255 | */ | |
256 | if (!left) | |
257 | sg_mark_end(&sg[sg_size - 1]); | |
258 | ||
259 | /* | |
260 | * only really needed for mempool backed sg allocations (like | |
261 | * SCSI), a possible improvement here would be to pass the | |
262 | * table pointer into the allocator and let that clear these | |
263 | * flags | |
264 | */ | |
265 | gfp_mask &= ~__GFP_WAIT; | |
266 | gfp_mask |= __GFP_HIGH; | |
267 | prv = sg; | |
268 | } while (left); | |
269 | ||
270 | return 0; | |
271 | } | |
272 | EXPORT_SYMBOL(__sg_alloc_table); | |
273 | ||
274 | /** | |
275 | * sg_alloc_table - Allocate and initialize an sg table | |
276 | * @table: The sg table header to use | |
277 | * @nents: Number of entries in sg list | |
278 | * @gfp_mask: GFP allocation mask | |
279 | * | |
280 | * Description: | |
281 | * Allocate and initialize an sg table. If @nents@ is larger than | |
282 | * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. | |
283 | * | |
284 | **/ | |
285 | int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) | |
286 | { | |
287 | int ret; | |
288 | ||
7cedb1f1 JB |
289 | ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, |
290 | gfp_mask, sg_kmalloc); | |
0db9299f | 291 | if (unlikely(ret)) |
7cedb1f1 | 292 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
293 | |
294 | return ret; | |
295 | } | |
296 | EXPORT_SYMBOL(sg_alloc_table); | |
b1adaf65 | 297 | |
137d3edb TH |
298 | /** |
299 | * sg_miter_start - start mapping iteration over a sg list | |
300 | * @miter: sg mapping iter to be started | |
301 | * @sgl: sg list to iterate over | |
302 | * @nents: number of sg entries | |
303 | * | |
304 | * Description: | |
305 | * Starts mapping iterator @miter. | |
306 | * | |
307 | * Context: | |
308 | * Don't care. | |
309 | */ | |
310 | void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, | |
311 | unsigned int nents, unsigned int flags) | |
312 | { | |
313 | memset(miter, 0, sizeof(struct sg_mapping_iter)); | |
314 | ||
315 | miter->__sg = sgl; | |
316 | miter->__nents = nents; | |
317 | miter->__offset = 0; | |
6de7e356 | 318 | WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); |
137d3edb TH |
319 | miter->__flags = flags; |
320 | } | |
321 | EXPORT_SYMBOL(sg_miter_start); | |
322 | ||
323 | /** | |
324 | * sg_miter_next - proceed mapping iterator to the next mapping | |
325 | * @miter: sg mapping iter to proceed | |
326 | * | |
327 | * Description: | |
328 | * Proceeds @miter@ to the next mapping. @miter@ should have been | |
329 | * started using sg_miter_start(). On successful return, | |
330 | * @miter@->page, @miter@->addr and @miter@->length point to the | |
331 | * current mapping. | |
332 | * | |
333 | * Context: | |
334 | * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till | |
335 | * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC. | |
336 | * | |
337 | * Returns: | |
338 | * true if @miter contains the next mapping. false if end of sg | |
339 | * list is reached. | |
340 | */ | |
341 | bool sg_miter_next(struct sg_mapping_iter *miter) | |
342 | { | |
343 | unsigned int off, len; | |
344 | ||
345 | /* check for end and drop resources from the last iteration */ | |
346 | if (!miter->__nents) | |
347 | return false; | |
348 | ||
349 | sg_miter_stop(miter); | |
350 | ||
351 | /* get to the next sg if necessary. __offset is adjusted by stop */ | |
23c560a9 TH |
352 | while (miter->__offset == miter->__sg->length) { |
353 | if (--miter->__nents) { | |
354 | miter->__sg = sg_next(miter->__sg); | |
355 | miter->__offset = 0; | |
356 | } else | |
357 | return false; | |
137d3edb TH |
358 | } |
359 | ||
360 | /* map the next page */ | |
361 | off = miter->__sg->offset + miter->__offset; | |
362 | len = miter->__sg->length - miter->__offset; | |
363 | ||
364 | miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT); | |
365 | off &= ~PAGE_MASK; | |
366 | miter->length = min_t(unsigned int, len, PAGE_SIZE - off); | |
367 | miter->consumed = miter->length; | |
368 | ||
369 | if (miter->__flags & SG_MITER_ATOMIC) | |
370 | miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off; | |
371 | else | |
372 | miter->addr = kmap(miter->page) + off; | |
373 | ||
374 | return true; | |
375 | } | |
376 | EXPORT_SYMBOL(sg_miter_next); | |
377 | ||
378 | /** | |
379 | * sg_miter_stop - stop mapping iteration | |
380 | * @miter: sg mapping iter to be stopped | |
381 | * | |
382 | * Description: | |
383 | * Stops mapping iterator @miter. @miter should have been started | |
384 | * started using sg_miter_start(). A stopped iteration can be | |
385 | * resumed by calling sg_miter_next() on it. This is useful when | |
386 | * resources (kmap) need to be released during iteration. | |
387 | * | |
388 | * Context: | |
389 | * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise. | |
390 | */ | |
391 | void sg_miter_stop(struct sg_mapping_iter *miter) | |
392 | { | |
393 | WARN_ON(miter->consumed > miter->length); | |
394 | ||
395 | /* drop resources from the last iteration */ | |
396 | if (miter->addr) { | |
397 | miter->__offset += miter->consumed; | |
398 | ||
6de7e356 SAS |
399 | if (miter->__flags & SG_MITER_TO_SG) |
400 | flush_kernel_dcache_page(miter->page); | |
401 | ||
137d3edb TH |
402 | if (miter->__flags & SG_MITER_ATOMIC) { |
403 | WARN_ON(!irqs_disabled()); | |
404 | kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ); | |
405 | } else | |
f652c521 | 406 | kunmap(miter->page); |
137d3edb TH |
407 | |
408 | miter->page = NULL; | |
409 | miter->addr = NULL; | |
410 | miter->length = 0; | |
411 | miter->consumed = 0; | |
412 | } | |
413 | } | |
414 | EXPORT_SYMBOL(sg_miter_stop); | |
415 | ||
b1adaf65 FT |
416 | /** |
417 | * sg_copy_buffer - Copy data between a linear buffer and an SG list | |
418 | * @sgl: The SG list | |
419 | * @nents: Number of SG entries | |
420 | * @buf: Where to copy from | |
421 | * @buflen: The number of bytes to copy | |
422 | * @to_buffer: transfer direction (non zero == from an sg list to a | |
423 | * buffer, 0 == from a buffer to an sg list | |
424 | * | |
425 | * Returns the number of copied bytes. | |
426 | * | |
427 | **/ | |
428 | static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, | |
429 | void *buf, size_t buflen, int to_buffer) | |
430 | { | |
137d3edb TH |
431 | unsigned int offset = 0; |
432 | struct sg_mapping_iter miter; | |
50bed2e2 | 433 | unsigned long flags; |
6de7e356 SAS |
434 | unsigned int sg_flags = SG_MITER_ATOMIC; |
435 | ||
436 | if (to_buffer) | |
437 | sg_flags |= SG_MITER_FROM_SG; | |
438 | else | |
439 | sg_flags |= SG_MITER_TO_SG; | |
137d3edb | 440 | |
6de7e356 | 441 | sg_miter_start(&miter, sgl, nents, sg_flags); |
137d3edb | 442 | |
50bed2e2 FT |
443 | local_irq_save(flags); |
444 | ||
137d3edb TH |
445 | while (sg_miter_next(&miter) && offset < buflen) { |
446 | unsigned int len; | |
447 | ||
448 | len = min(miter.length, buflen - offset); | |
449 | ||
450 | if (to_buffer) | |
451 | memcpy(buf + offset, miter.addr, len); | |
6de7e356 | 452 | else |
137d3edb | 453 | memcpy(miter.addr, buf + offset, len); |
b1adaf65 | 454 | |
137d3edb | 455 | offset += len; |
b1adaf65 FT |
456 | } |
457 | ||
137d3edb TH |
458 | sg_miter_stop(&miter); |
459 | ||
50bed2e2 | 460 | local_irq_restore(flags); |
137d3edb | 461 | return offset; |
b1adaf65 FT |
462 | } |
463 | ||
464 | /** | |
465 | * sg_copy_from_buffer - Copy from a linear buffer to an SG list | |
466 | * @sgl: The SG list | |
467 | * @nents: Number of SG entries | |
468 | * @buf: Where to copy from | |
469 | * @buflen: The number of bytes to copy | |
470 | * | |
471 | * Returns the number of copied bytes. | |
472 | * | |
473 | **/ | |
474 | size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, | |
475 | void *buf, size_t buflen) | |
476 | { | |
477 | return sg_copy_buffer(sgl, nents, buf, buflen, 0); | |
478 | } | |
479 | EXPORT_SYMBOL(sg_copy_from_buffer); | |
480 | ||
481 | /** | |
482 | * sg_copy_to_buffer - Copy from an SG list to a linear buffer | |
483 | * @sgl: The SG list | |
484 | * @nents: Number of SG entries | |
485 | * @buf: Where to copy to | |
486 | * @buflen: The number of bytes to copy | |
487 | * | |
488 | * Returns the number of copied bytes. | |
489 | * | |
490 | **/ | |
491 | size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, | |
492 | void *buf, size_t buflen) | |
493 | { | |
494 | return sg_copy_buffer(sgl, nents, buf, buflen, 1); | |
495 | } | |
496 | EXPORT_SYMBOL(sg_copy_to_buffer); |