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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> |
10 | #include <linux/slab.h> |
11 | #include <linux/scatterlist.h> |
12 | #include <linux/highmem.h> |
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 |
135 | * @max_ents: The maximum number of entries per single scatterlist |
136 | * @free_fn: Free function |
137 | * |
138 | * Description: |
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(). |
142 | * |
143 | **/ |
144 | void __sg_free_table(struct sg_table *table, unsigned int max_ents, |
145 | sg_free_fn *free_fn) |
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 | /* |
158 | * If we have more than max_ents segments left, |
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 | */ |
163 | if (alloc_size > max_ents) { |
164 | next = sg_chain_ptr(&sgl[max_ents - 1]); |
165 | alloc_size = max_ents; |
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 | { |
188 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
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 |
196 | * @max_ents: The maximum number of entries the allocator returns per call |
197 | * @gfp_mask: GFP allocation mask |
198 | * @alloc_fn: Allocator to use |
199 | * |
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 | * |
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 | **/ |
211 | int __sg_alloc_table(struct sg_table *table, unsigned int nents, |
212 | unsigned int max_ents, gfp_t gfp_mask, |
213 | sg_alloc_fn *alloc_fn) |
214 | { |
215 | struct scatterlist *sg, *prv; |
216 | unsigned int left; |
217 | |
218 | #ifndef ARCH_HAS_SG_CHAIN |
219 | BUG_ON(nents > max_ents); |
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 | |
229 | if (alloc_size > max_ents) { |
230 | alloc_size = max_ents; |
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) |
249 | sg_chain(prv, max_ents, sg); |
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 | |
289 | ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, |
290 | gfp_mask, sg_kmalloc); |
291 | if (unlikely(ret)) |
292 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
293 | |
294 | return ret; |
295 | } |
296 | EXPORT_SYMBOL(sg_alloc_table); |
297 | |
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; |
318 | WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); |
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 */ |
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; |
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 | |
399 | if (miter->__flags & SG_MITER_TO_SG) |
400 | flush_kernel_dcache_page(miter->page); |
401 | |
402 | if (miter->__flags & SG_MITER_ATOMIC) { |
403 | WARN_ON(!irqs_disabled()); |
404 | kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ); |
405 | } else |
406 | kunmap(miter->page); |
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 | |
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 | { |
431 | unsigned int offset = 0; |
432 | struct sg_mapping_iter miter; |
433 | unsigned long flags; |
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; |
440 | |
441 | sg_miter_start(&miter, sgl, nents, sg_flags); |
442 | |
443 | local_irq_save(flags); |
444 | |
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); |
452 | else |
453 | memcpy(miter.addr, buf + offset, len); |
454 | |
455 | offset += len; |
456 | } |
457 | |
458 | sg_miter_stop(&miter); |
459 | |
460 | local_irq_restore(flags); |
461 | return offset; |
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); |
497 |
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