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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> | |
10 | #include <linux/scatterlist.h> | |
b1adaf65 | 11 | #include <linux/highmem.h> |
0db9299f JA |
12 | |
13 | /** | |
14 | * sg_next - return the next scatterlist entry in a list | |
15 | * @sg: The current sg entry | |
16 | * | |
17 | * Description: | |
18 | * Usually the next entry will be @sg@ + 1, but if this sg element is part | |
19 | * of a chained scatterlist, it could jump to the start of a new | |
20 | * scatterlist array. | |
21 | * | |
22 | **/ | |
23 | struct scatterlist *sg_next(struct scatterlist *sg) | |
24 | { | |
25 | #ifdef CONFIG_DEBUG_SG | |
26 | BUG_ON(sg->sg_magic != SG_MAGIC); | |
27 | #endif | |
28 | if (sg_is_last(sg)) | |
29 | return NULL; | |
30 | ||
31 | sg++; | |
32 | if (unlikely(sg_is_chain(sg))) | |
33 | sg = sg_chain_ptr(sg); | |
34 | ||
35 | return sg; | |
36 | } | |
37 | EXPORT_SYMBOL(sg_next); | |
38 | ||
39 | /** | |
40 | * sg_last - return the last scatterlist entry in a list | |
41 | * @sgl: First entry in the scatterlist | |
42 | * @nents: Number of entries in the scatterlist | |
43 | * | |
44 | * Description: | |
45 | * Should only be used casually, it (currently) scans the entire list | |
46 | * to get the last entry. | |
47 | * | |
48 | * Note that the @sgl@ pointer passed in need not be the first one, | |
49 | * the important bit is that @nents@ denotes the number of entries that | |
50 | * exist from @sgl@. | |
51 | * | |
52 | **/ | |
53 | struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) | |
54 | { | |
55 | #ifndef ARCH_HAS_SG_CHAIN | |
56 | struct scatterlist *ret = &sgl[nents - 1]; | |
57 | #else | |
58 | struct scatterlist *sg, *ret = NULL; | |
59 | unsigned int i; | |
60 | ||
61 | for_each_sg(sgl, sg, nents, i) | |
62 | ret = sg; | |
63 | ||
64 | #endif | |
65 | #ifdef CONFIG_DEBUG_SG | |
66 | BUG_ON(sgl[0].sg_magic != SG_MAGIC); | |
67 | BUG_ON(!sg_is_last(ret)); | |
68 | #endif | |
69 | return ret; | |
70 | } | |
71 | EXPORT_SYMBOL(sg_last); | |
72 | ||
73 | /** | |
74 | * sg_init_table - Initialize SG table | |
75 | * @sgl: The SG table | |
76 | * @nents: Number of entries in table | |
77 | * | |
78 | * Notes: | |
79 | * If this is part of a chained sg table, sg_mark_end() should be | |
80 | * used only on the last table part. | |
81 | * | |
82 | **/ | |
83 | void sg_init_table(struct scatterlist *sgl, unsigned int nents) | |
84 | { | |
85 | memset(sgl, 0, sizeof(*sgl) * nents); | |
86 | #ifdef CONFIG_DEBUG_SG | |
87 | { | |
88 | unsigned int i; | |
89 | for (i = 0; i < nents; i++) | |
90 | sgl[i].sg_magic = SG_MAGIC; | |
91 | } | |
92 | #endif | |
93 | sg_mark_end(&sgl[nents - 1]); | |
94 | } | |
95 | EXPORT_SYMBOL(sg_init_table); | |
96 | ||
97 | /** | |
98 | * sg_init_one - Initialize a single entry sg list | |
99 | * @sg: SG entry | |
100 | * @buf: Virtual address for IO | |
101 | * @buflen: IO length | |
102 | * | |
103 | **/ | |
104 | void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) | |
105 | { | |
106 | sg_init_table(sg, 1); | |
107 | sg_set_buf(sg, buf, buflen); | |
108 | } | |
109 | EXPORT_SYMBOL(sg_init_one); | |
110 | ||
111 | /* | |
112 | * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree | |
113 | * helpers. | |
114 | */ | |
115 | static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) | |
116 | { | |
117 | if (nents == SG_MAX_SINGLE_ALLOC) | |
118 | return (struct scatterlist *) __get_free_page(gfp_mask); | |
119 | else | |
120 | return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); | |
121 | } | |
122 | ||
123 | static void sg_kfree(struct scatterlist *sg, unsigned int nents) | |
124 | { | |
125 | if (nents == SG_MAX_SINGLE_ALLOC) | |
126 | free_page((unsigned long) sg); | |
127 | else | |
128 | kfree(sg); | |
129 | } | |
130 | ||
131 | /** | |
132 | * __sg_free_table - Free a previously mapped sg table | |
133 | * @table: The sg table header to use | |
7cedb1f1 | 134 | * @max_ents: The maximum number of entries per single scatterlist |
0db9299f JA |
135 | * @free_fn: Free function |
136 | * | |
137 | * Description: | |
7cedb1f1 JB |
138 | * Free an sg table previously allocated and setup with |
139 | * __sg_alloc_table(). The @max_ents value must be identical to | |
140 | * that previously used with __sg_alloc_table(). | |
0db9299f JA |
141 | * |
142 | **/ | |
7cedb1f1 JB |
143 | void __sg_free_table(struct sg_table *table, unsigned int max_ents, |
144 | sg_free_fn *free_fn) | |
0db9299f JA |
145 | { |
146 | struct scatterlist *sgl, *next; | |
147 | ||
148 | if (unlikely(!table->sgl)) | |
149 | return; | |
150 | ||
151 | sgl = table->sgl; | |
152 | while (table->orig_nents) { | |
153 | unsigned int alloc_size = table->orig_nents; | |
154 | unsigned int sg_size; | |
155 | ||
156 | /* | |
7cedb1f1 | 157 | * If we have more than max_ents segments left, |
0db9299f JA |
158 | * then assign 'next' to the sg table after the current one. |
159 | * sg_size is then one less than alloc size, since the last | |
160 | * element is the chain pointer. | |
161 | */ | |
7cedb1f1 JB |
162 | if (alloc_size > max_ents) { |
163 | next = sg_chain_ptr(&sgl[max_ents - 1]); | |
164 | alloc_size = max_ents; | |
0db9299f JA |
165 | sg_size = alloc_size - 1; |
166 | } else { | |
167 | sg_size = alloc_size; | |
168 | next = NULL; | |
169 | } | |
170 | ||
171 | table->orig_nents -= sg_size; | |
172 | free_fn(sgl, alloc_size); | |
173 | sgl = next; | |
174 | } | |
175 | ||
176 | table->sgl = NULL; | |
177 | } | |
178 | EXPORT_SYMBOL(__sg_free_table); | |
179 | ||
180 | /** | |
181 | * sg_free_table - Free a previously allocated sg table | |
182 | * @table: The mapped sg table header | |
183 | * | |
184 | **/ | |
185 | void sg_free_table(struct sg_table *table) | |
186 | { | |
7cedb1f1 | 187 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
188 | } |
189 | EXPORT_SYMBOL(sg_free_table); | |
190 | ||
191 | /** | |
192 | * __sg_alloc_table - Allocate and initialize an sg table with given allocator | |
193 | * @table: The sg table header to use | |
194 | * @nents: Number of entries in sg list | |
7cedb1f1 | 195 | * @max_ents: The maximum number of entries the allocator returns per call |
0db9299f JA |
196 | * @gfp_mask: GFP allocation mask |
197 | * @alloc_fn: Allocator to use | |
198 | * | |
7cedb1f1 JB |
199 | * Description: |
200 | * This function returns a @table @nents long. The allocator is | |
201 | * defined to return scatterlist chunks of maximum size @max_ents. | |
202 | * Thus if @nents is bigger than @max_ents, the scatterlists will be | |
203 | * chained in units of @max_ents. | |
204 | * | |
0db9299f JA |
205 | * Notes: |
206 | * If this function returns non-0 (eg failure), the caller must call | |
207 | * __sg_free_table() to cleanup any leftover allocations. | |
208 | * | |
209 | **/ | |
7cedb1f1 JB |
210 | int __sg_alloc_table(struct sg_table *table, unsigned int nents, |
211 | unsigned int max_ents, gfp_t gfp_mask, | |
0db9299f JA |
212 | sg_alloc_fn *alloc_fn) |
213 | { | |
214 | struct scatterlist *sg, *prv; | |
215 | unsigned int left; | |
216 | ||
217 | #ifndef ARCH_HAS_SG_CHAIN | |
7cedb1f1 | 218 | BUG_ON(nents > max_ents); |
0db9299f JA |
219 | #endif |
220 | ||
221 | memset(table, 0, sizeof(*table)); | |
222 | ||
223 | left = nents; | |
224 | prv = NULL; | |
225 | do { | |
226 | unsigned int sg_size, alloc_size = left; | |
227 | ||
7cedb1f1 JB |
228 | if (alloc_size > max_ents) { |
229 | alloc_size = max_ents; | |
0db9299f JA |
230 | sg_size = alloc_size - 1; |
231 | } else | |
232 | sg_size = alloc_size; | |
233 | ||
234 | left -= sg_size; | |
235 | ||
236 | sg = alloc_fn(alloc_size, gfp_mask); | |
237 | if (unlikely(!sg)) | |
238 | return -ENOMEM; | |
239 | ||
240 | sg_init_table(sg, alloc_size); | |
241 | table->nents = table->orig_nents += sg_size; | |
242 | ||
243 | /* | |
244 | * If this is the first mapping, assign the sg table header. | |
245 | * If this is not the first mapping, chain previous part. | |
246 | */ | |
247 | if (prv) | |
7cedb1f1 | 248 | sg_chain(prv, max_ents, sg); |
0db9299f JA |
249 | else |
250 | table->sgl = sg; | |
251 | ||
252 | /* | |
253 | * If no more entries after this one, mark the end | |
254 | */ | |
255 | if (!left) | |
256 | sg_mark_end(&sg[sg_size - 1]); | |
257 | ||
258 | /* | |
259 | * only really needed for mempool backed sg allocations (like | |
260 | * SCSI), a possible improvement here would be to pass the | |
261 | * table pointer into the allocator and let that clear these | |
262 | * flags | |
263 | */ | |
264 | gfp_mask &= ~__GFP_WAIT; | |
265 | gfp_mask |= __GFP_HIGH; | |
266 | prv = sg; | |
267 | } while (left); | |
268 | ||
269 | return 0; | |
270 | } | |
271 | EXPORT_SYMBOL(__sg_alloc_table); | |
272 | ||
273 | /** | |
274 | * sg_alloc_table - Allocate and initialize an sg table | |
275 | * @table: The sg table header to use | |
276 | * @nents: Number of entries in sg list | |
277 | * @gfp_mask: GFP allocation mask | |
278 | * | |
279 | * Description: | |
280 | * Allocate and initialize an sg table. If @nents@ is larger than | |
281 | * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. | |
282 | * | |
283 | **/ | |
284 | int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) | |
285 | { | |
286 | int ret; | |
287 | ||
7cedb1f1 JB |
288 | ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, |
289 | gfp_mask, sg_kmalloc); | |
0db9299f | 290 | if (unlikely(ret)) |
7cedb1f1 | 291 | __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); |
0db9299f JA |
292 | |
293 | return ret; | |
294 | } | |
295 | EXPORT_SYMBOL(sg_alloc_table); | |
b1adaf65 FT |
296 | |
297 | /** | |
298 | * sg_copy_buffer - Copy data between a linear buffer and an SG list | |
299 | * @sgl: The SG list | |
300 | * @nents: Number of SG entries | |
301 | * @buf: Where to copy from | |
302 | * @buflen: The number of bytes to copy | |
303 | * @to_buffer: transfer direction (non zero == from an sg list to a | |
304 | * buffer, 0 == from a buffer to an sg list | |
305 | * | |
306 | * Returns the number of copied bytes. | |
307 | * | |
308 | **/ | |
309 | static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, | |
310 | void *buf, size_t buflen, int to_buffer) | |
311 | { | |
312 | struct scatterlist *sg; | |
313 | size_t buf_off = 0; | |
314 | int i; | |
315 | ||
316 | WARN_ON(!irqs_disabled()); | |
317 | ||
318 | for_each_sg(sgl, sg, nents, i) { | |
319 | struct page *page; | |
320 | int n = 0; | |
321 | unsigned int sg_off = sg->offset; | |
322 | unsigned int sg_copy = sg->length; | |
323 | ||
324 | if (sg_copy > buflen) | |
325 | sg_copy = buflen; | |
326 | buflen -= sg_copy; | |
327 | ||
328 | while (sg_copy > 0) { | |
329 | unsigned int page_copy; | |
330 | void *p; | |
331 | ||
332 | page_copy = PAGE_SIZE - sg_off; | |
333 | if (page_copy > sg_copy) | |
334 | page_copy = sg_copy; | |
335 | ||
336 | page = nth_page(sg_page(sg), n); | |
337 | p = kmap_atomic(page, KM_BIO_SRC_IRQ); | |
338 | ||
339 | if (to_buffer) | |
340 | memcpy(buf + buf_off, p + sg_off, page_copy); | |
341 | else { | |
342 | memcpy(p + sg_off, buf + buf_off, page_copy); | |
343 | flush_kernel_dcache_page(page); | |
344 | } | |
345 | ||
346 | kunmap_atomic(p, KM_BIO_SRC_IRQ); | |
347 | ||
348 | buf_off += page_copy; | |
349 | sg_off += page_copy; | |
350 | if (sg_off == PAGE_SIZE) { | |
351 | sg_off = 0; | |
352 | n++; | |
353 | } | |
354 | sg_copy -= page_copy; | |
355 | } | |
356 | ||
357 | if (!buflen) | |
358 | break; | |
359 | } | |
360 | ||
361 | return buf_off; | |
362 | } | |
363 | ||
364 | /** | |
365 | * sg_copy_from_buffer - Copy from a linear buffer to an SG list | |
366 | * @sgl: The SG list | |
367 | * @nents: Number of SG entries | |
368 | * @buf: Where to copy from | |
369 | * @buflen: The number of bytes to copy | |
370 | * | |
371 | * Returns the number of copied bytes. | |
372 | * | |
373 | **/ | |
374 | size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, | |
375 | void *buf, size_t buflen) | |
376 | { | |
377 | return sg_copy_buffer(sgl, nents, buf, buflen, 0); | |
378 | } | |
379 | EXPORT_SYMBOL(sg_copy_from_buffer); | |
380 | ||
381 | /** | |
382 | * sg_copy_to_buffer - Copy from an SG list to a linear buffer | |
383 | * @sgl: The SG list | |
384 | * @nents: Number of SG entries | |
385 | * @buf: Where to copy to | |
386 | * @buflen: The number of bytes to copy | |
387 | * | |
388 | * Returns the number of copied bytes. | |
389 | * | |
390 | **/ | |
391 | size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, | |
392 | void *buf, size_t buflen) | |
393 | { | |
394 | return sg_copy_buffer(sgl, nents, buf, buflen, 1); | |
395 | } | |
396 | EXPORT_SYMBOL(sg_copy_to_buffer); |