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/module.h>
10 #include <linux/slab.h>
11 #include <linux/scatterlist.h>
12 #include <linux/highmem.h>
15 * sg_next - return the next scatterlist entry in a list
16 * @sg: The current sg entry
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
24 struct scatterlist
*sg_next(struct scatterlist
*sg
)
26 #ifdef CONFIG_DEBUG_SG
27 BUG_ON(sg
->sg_magic
!= SG_MAGIC
);
33 if (unlikely(sg_is_chain(sg
)))
34 sg
= sg_chain_ptr(sg
);
38 EXPORT_SYMBOL(sg_next
);
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
46 * Should only be used casually, it (currently) scans the entire list
47 * to get the last entry.
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
54 struct scatterlist
*sg_last(struct scatterlist
*sgl
, unsigned int nents
)
56 #ifndef ARCH_HAS_SG_CHAIN
57 struct scatterlist
*ret
= &sgl
[nents
- 1];
59 struct scatterlist
*sg
, *ret
= NULL
;
62 for_each_sg(sgl
, sg
, nents
, i
)
66 #ifdef CONFIG_DEBUG_SG
67 BUG_ON(sgl
[0].sg_magic
!= SG_MAGIC
);
68 BUG_ON(!sg_is_last(ret
));
72 EXPORT_SYMBOL(sg_last
);
75 * sg_init_table - Initialize SG table
77 * @nents: Number of entries in table
80 * If this is part of a chained sg table, sg_mark_end() should be
81 * used only on the last table part.
84 void sg_init_table(struct scatterlist
*sgl
, unsigned int nents
)
86 memset(sgl
, 0, sizeof(*sgl
) * nents
);
87 #ifdef CONFIG_DEBUG_SG
90 for (i
= 0; i
< nents
; i
++)
91 sgl
[i
].sg_magic
= SG_MAGIC
;
94 sg_mark_end(&sgl
[nents
- 1]);
96 EXPORT_SYMBOL(sg_init_table
);
99 * sg_init_one - Initialize a single entry sg list
101 * @buf: Virtual address for IO
105 void sg_init_one(struct scatterlist
*sg
, const void *buf
, unsigned int buflen
)
107 sg_init_table(sg
, 1);
108 sg_set_buf(sg
, buf
, buflen
);
110 EXPORT_SYMBOL(sg_init_one
);
113 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
116 static struct scatterlist
*sg_kmalloc(unsigned int nents
, gfp_t gfp_mask
)
118 if (nents
== SG_MAX_SINGLE_ALLOC
)
119 return (struct scatterlist
*) __get_free_page(gfp_mask
);
121 return kmalloc(nents
* sizeof(struct scatterlist
), gfp_mask
);
124 static void sg_kfree(struct scatterlist
*sg
, unsigned int nents
)
126 if (nents
== SG_MAX_SINGLE_ALLOC
)
127 free_page((unsigned long) sg
);
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
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().
144 void __sg_free_table(struct sg_table
*table
, unsigned int max_ents
,
147 struct scatterlist
*sgl
, *next
;
149 if (unlikely(!table
->sgl
))
153 while (table
->orig_nents
) {
154 unsigned int alloc_size
= table
->orig_nents
;
155 unsigned int sg_size
;
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.
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;
168 sg_size
= alloc_size
;
172 table
->orig_nents
-= sg_size
;
173 free_fn(sgl
, alloc_size
);
179 EXPORT_SYMBOL(__sg_free_table
);
182 * sg_free_table - Free a previously allocated sg table
183 * @table: The mapped sg table header
186 void sg_free_table(struct sg_table
*table
)
188 __sg_free_table(table
, SG_MAX_SINGLE_ALLOC
, sg_kfree
);
190 EXPORT_SYMBOL(sg_free_table
);
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
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.
207 * If this function returns non-0 (eg failure), the caller must call
208 * __sg_free_table() to cleanup any leftover allocations.
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
)
215 struct scatterlist
*sg
, *prv
;
218 #ifndef ARCH_HAS_SG_CHAIN
219 BUG_ON(nents
> max_ents
);
222 memset(table
, 0, sizeof(*table
));
227 unsigned int sg_size
, alloc_size
= left
;
229 if (alloc_size
> max_ents
) {
230 alloc_size
= max_ents
;
231 sg_size
= alloc_size
- 1;
233 sg_size
= alloc_size
;
237 sg
= alloc_fn(alloc_size
, gfp_mask
);
241 sg_init_table(sg
, alloc_size
);
242 table
->nents
= table
->orig_nents
+= sg_size
;
245 * If this is the first mapping, assign the sg table header.
246 * If this is not the first mapping, chain previous part.
249 sg_chain(prv
, max_ents
, sg
);
254 * If no more entries after this one, mark the end
257 sg_mark_end(&sg
[sg_size
- 1]);
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
265 gfp_mask
&= ~__GFP_WAIT
;
266 gfp_mask
|= __GFP_HIGH
;
272 EXPORT_SYMBOL(__sg_alloc_table
);
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
281 * Allocate and initialize an sg table. If @nents@ is larger than
282 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
285 int sg_alloc_table(struct sg_table
*table
, unsigned int nents
, gfp_t gfp_mask
)
289 ret
= __sg_alloc_table(table
, nents
, SG_MAX_SINGLE_ALLOC
,
290 gfp_mask
, sg_kmalloc
);
292 __sg_free_table(table
, SG_MAX_SINGLE_ALLOC
, sg_kfree
);
296 EXPORT_SYMBOL(sg_alloc_table
);
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
305 * Starts mapping iterator @miter.
310 void sg_miter_start(struct sg_mapping_iter
*miter
, struct scatterlist
*sgl
,
311 unsigned int nents
, unsigned int flags
)
313 memset(miter
, 0, sizeof(struct sg_mapping_iter
));
316 miter
->__nents
= nents
;
318 WARN_ON(!(flags
& (SG_MITER_TO_SG
| SG_MITER_FROM_SG
)));
319 miter
->__flags
= flags
;
321 EXPORT_SYMBOL(sg_miter_start
);
324 * sg_miter_next - proceed mapping iterator to the next mapping
325 * @miter: sg mapping iter to proceed
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
334 * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till
335 * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC.
338 * true if @miter contains the next mapping. false if end of sg
341 bool sg_miter_next(struct sg_mapping_iter
*miter
)
343 unsigned int off
, len
;
345 /* check for end and drop resources from the last iteration */
349 sg_miter_stop(miter
);
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
);
360 /* map the next page */
361 off
= miter
->__sg
->offset
+ miter
->__offset
;
362 len
= miter
->__sg
->length
- miter
->__offset
;
364 miter
->page
= nth_page(sg_page(miter
->__sg
), off
>> PAGE_SHIFT
);
366 miter
->length
= min_t(unsigned int, len
, PAGE_SIZE
- off
);
367 miter
->consumed
= miter
->length
;
369 if (miter
->__flags
& SG_MITER_ATOMIC
)
370 miter
->addr
= kmap_atomic(miter
->page
, KM_BIO_SRC_IRQ
) + off
;
372 miter
->addr
= kmap(miter
->page
) + off
;
376 EXPORT_SYMBOL(sg_miter_next
);
379 * sg_miter_stop - stop mapping iteration
380 * @miter: sg mapping iter to be stopped
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.
389 * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise.
391 void sg_miter_stop(struct sg_mapping_iter
*miter
)
393 WARN_ON(miter
->consumed
> miter
->length
);
395 /* drop resources from the last iteration */
397 miter
->__offset
+= miter
->consumed
;
399 if (miter
->__flags
& SG_MITER_TO_SG
)
400 flush_kernel_dcache_page(miter
->page
);
402 if (miter
->__flags
& SG_MITER_ATOMIC
) {
403 WARN_ON(!irqs_disabled());
404 kunmap_atomic(miter
->addr
, KM_BIO_SRC_IRQ
);
414 EXPORT_SYMBOL(sg_miter_stop
);
417 * sg_copy_buffer - Copy data between a linear buffer and an 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
425 * Returns the number of copied bytes.
428 static size_t sg_copy_buffer(struct scatterlist
*sgl
, unsigned int nents
,
429 void *buf
, size_t buflen
, int to_buffer
)
431 unsigned int offset
= 0;
432 struct sg_mapping_iter miter
;
434 unsigned int sg_flags
= SG_MITER_ATOMIC
;
437 sg_flags
|= SG_MITER_FROM_SG
;
439 sg_flags
|= SG_MITER_TO_SG
;
441 sg_miter_start(&miter
, sgl
, nents
, sg_flags
);
443 local_irq_save(flags
);
445 while (sg_miter_next(&miter
) && offset
< buflen
) {
448 len
= min(miter
.length
, buflen
- offset
);
451 memcpy(buf
+ offset
, miter
.addr
, len
);
453 memcpy(miter
.addr
, buf
+ offset
, len
);
458 sg_miter_stop(&miter
);
460 local_irq_restore(flags
);
465 * sg_copy_from_buffer - Copy from a linear buffer to an SG list
467 * @nents: Number of SG entries
468 * @buf: Where to copy from
469 * @buflen: The number of bytes to copy
471 * Returns the number of copied bytes.
474 size_t sg_copy_from_buffer(struct scatterlist
*sgl
, unsigned int nents
,
475 void *buf
, size_t buflen
)
477 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, 0);
479 EXPORT_SYMBOL(sg_copy_from_buffer
);
482 * sg_copy_to_buffer - Copy from an SG list to a linear buffer
484 * @nents: Number of SG entries
485 * @buf: Where to copy to
486 * @buflen: The number of bytes to copy
488 * Returns the number of copied bytes.
491 size_t sg_copy_to_buffer(struct scatterlist
*sgl
, unsigned int nents
,
492 void *buf
, size_t buflen
)
494 return sg_copy_buffer(sgl
, nents
, buf
, buflen
, 1);
496 EXPORT_SYMBOL(sg_copy_to_buffer
);