0,0 → 1,363 |
/* |
* Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com> |
* |
* Scatterlist handling helpers. |
* |
* This source code is licensed under the GNU General Public License, |
* Version 2. See the file COPYING for more details. |
*/ |
#include <linux/export.h> |
#include <linux/scatterlist.h> |
|
/** |
* sg_next - return the next scatterlist entry in a list |
* @sg: The current sg entry |
* |
* Description: |
* Usually the next entry will be @sg@ + 1, but if this sg element is part |
* of a chained scatterlist, it could jump to the start of a new |
* scatterlist array. |
* |
**/ |
struct scatterlist *sg_next(struct scatterlist *sg) |
{ |
#ifdef CONFIG_DEBUG_SG |
BUG_ON(sg->sg_magic != SG_MAGIC); |
#endif |
if (sg_is_last(sg)) |
return NULL; |
|
sg++; |
if (unlikely(sg_is_chain(sg))) |
sg = sg_chain_ptr(sg); |
|
return sg; |
} |
EXPORT_SYMBOL(sg_next); |
|
/** |
* sg_nents - return total count of entries in scatterlist |
* @sg: The scatterlist |
* |
* Description: |
* Allows to know how many entries are in sg, taking into acount |
* chaining as well |
* |
**/ |
int sg_nents(struct scatterlist *sg) |
{ |
int nents; |
for (nents = 0; sg; sg = sg_next(sg)) |
nents++; |
return nents; |
} |
EXPORT_SYMBOL(sg_nents); |
|
|
/** |
* sg_last - return the last scatterlist entry in a list |
* @sgl: First entry in the scatterlist |
* @nents: Number of entries in the scatterlist |
* |
* Description: |
* Should only be used casually, it (currently) scans the entire list |
* to get the last entry. |
* |
* Note that the @sgl@ pointer passed in need not be the first one, |
* the important bit is that @nents@ denotes the number of entries that |
* exist from @sgl@. |
* |
**/ |
struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) |
{ |
#ifndef ARCH_HAS_SG_CHAIN |
struct scatterlist *ret = &sgl[nents - 1]; |
#else |
struct scatterlist *sg, *ret = NULL; |
unsigned int i; |
|
for_each_sg(sgl, sg, nents, i) |
ret = sg; |
|
#endif |
#ifdef CONFIG_DEBUG_SG |
BUG_ON(sgl[0].sg_magic != SG_MAGIC); |
BUG_ON(!sg_is_last(ret)); |
#endif |
return ret; |
} |
EXPORT_SYMBOL(sg_last); |
|
/** |
* sg_init_table - Initialize SG table |
* @sgl: The SG table |
* @nents: Number of entries in table |
* |
* Notes: |
* If this is part of a chained sg table, sg_mark_end() should be |
* used only on the last table part. |
* |
**/ |
void sg_init_table(struct scatterlist *sgl, unsigned int nents) |
{ |
memset(sgl, 0, sizeof(*sgl) * nents); |
#ifdef CONFIG_DEBUG_SG |
{ |
unsigned int i; |
for (i = 0; i < nents; i++) |
sgl[i].sg_magic = SG_MAGIC; |
} |
#endif |
sg_mark_end(&sgl[nents - 1]); |
} |
EXPORT_SYMBOL(sg_init_table); |
|
/** |
* sg_init_one - Initialize a single entry sg list |
* @sg: SG entry |
* @buf: Virtual address for IO |
* @buflen: IO length |
* |
**/ |
//void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) |
//{ |
// sg_init_table(sg, 1); |
// sg_set_buf(sg, buf, buflen); |
//} |
EXPORT_SYMBOL(sg_init_one); |
|
/* |
* The default behaviour of sg_alloc_table() is to use these kmalloc/kfree |
* helpers. |
*/ |
static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) |
{ |
return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); |
} |
|
static void sg_kfree(struct scatterlist *sg, unsigned int nents) |
{ |
kfree(sg); |
} |
|
/** |
* __sg_free_table - Free a previously mapped sg table |
* @table: The sg table header to use |
* @max_ents: The maximum number of entries per single scatterlist |
* @skip_first_chunk: don't free the (preallocated) first scatterlist chunk |
* @free_fn: Free function |
* |
* Description: |
* Free an sg table previously allocated and setup with |
* __sg_alloc_table(). The @max_ents value must be identical to |
* that previously used with __sg_alloc_table(). |
* |
**/ |
void __sg_free_table(struct sg_table *table, unsigned int max_ents, |
bool skip_first_chunk, sg_free_fn *free_fn) |
{ |
struct scatterlist *sgl, *next; |
|
if (unlikely(!table->sgl)) |
return; |
|
sgl = table->sgl; |
while (table->orig_nents) { |
unsigned int alloc_size = table->orig_nents; |
unsigned int sg_size; |
|
/* |
* If we have more than max_ents segments left, |
* then assign 'next' to the sg table after the current one. |
* sg_size is then one less than alloc size, since the last |
* element is the chain pointer. |
*/ |
if (alloc_size > max_ents) { |
next = sg_chain_ptr(&sgl[max_ents - 1]); |
alloc_size = max_ents; |
sg_size = alloc_size - 1; |
} else { |
sg_size = alloc_size; |
next = NULL; |
} |
|
table->orig_nents -= sg_size; |
if (!skip_first_chunk) { |
free_fn(sgl, alloc_size); |
skip_first_chunk = false; |
} |
sgl = next; |
} |
|
table->sgl = NULL; |
} |
EXPORT_SYMBOL(__sg_free_table); |
|
/** |
* sg_free_table - Free a previously allocated sg table |
* @table: The mapped sg table header |
* |
**/ |
void sg_free_table(struct sg_table *table) |
{ |
__sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); |
} |
EXPORT_SYMBOL(sg_free_table); |
|
/** |
* __sg_alloc_table - Allocate and initialize an sg table with given allocator |
* @table: The sg table header to use |
* @nents: Number of entries in sg list |
* @max_ents: The maximum number of entries the allocator returns per call |
* @gfp_mask: GFP allocation mask |
* @alloc_fn: Allocator to use |
* |
* Description: |
* This function returns a @table @nents long. The allocator is |
* defined to return scatterlist chunks of maximum size @max_ents. |
* Thus if @nents is bigger than @max_ents, the scatterlists will be |
* chained in units of @max_ents. |
* |
* Notes: |
* If this function returns non-0 (eg failure), the caller must call |
* __sg_free_table() to cleanup any leftover allocations. |
* |
**/ |
int __sg_alloc_table(struct sg_table *table, unsigned int nents, |
unsigned int max_ents, struct scatterlist *first_chunk, |
gfp_t gfp_mask, sg_alloc_fn *alloc_fn) |
{ |
struct scatterlist *sg, *prv; |
unsigned int left; |
|
memset(table, 0, sizeof(*table)); |
|
if (nents == 0) |
return -EINVAL; |
#ifndef ARCH_HAS_SG_CHAIN |
if (WARN_ON_ONCE(nents > max_ents)) |
return -EINVAL; |
#endif |
|
left = nents; |
prv = NULL; |
do { |
unsigned int sg_size, alloc_size = left; |
|
if (alloc_size > max_ents) { |
alloc_size = max_ents; |
sg_size = alloc_size - 1; |
} else |
sg_size = alloc_size; |
|
left -= sg_size; |
|
if (first_chunk) { |
sg = first_chunk; |
first_chunk = NULL; |
} else { |
sg = alloc_fn(alloc_size, gfp_mask); |
} |
if (unlikely(!sg)) { |
/* |
* Adjust entry count to reflect that the last |
* entry of the previous table won't be used for |
* linkage. Without this, sg_kfree() may get |
* confused. |
*/ |
if (prv) |
table->nents = ++table->orig_nents; |
|
return -ENOMEM; |
} |
|
sg_init_table(sg, alloc_size); |
table->nents = table->orig_nents += sg_size; |
|
/* |
* If this is the first mapping, assign the sg table header. |
* If this is not the first mapping, chain previous part. |
*/ |
if (prv) |
sg_chain(prv, max_ents, sg); |
else |
table->sgl = sg; |
|
/* |
* If no more entries after this one, mark the end |
*/ |
if (!left) |
sg_mark_end(&sg[sg_size - 1]); |
|
prv = sg; |
} while (left); |
|
return 0; |
} |
EXPORT_SYMBOL(__sg_alloc_table); |
|
/** |
* sg_alloc_table - Allocate and initialize an sg table |
* @table: The sg table header to use |
* @nents: Number of entries in sg list |
* @gfp_mask: GFP allocation mask |
* |
* Description: |
* Allocate and initialize an sg table. If @nents@ is larger than |
* SG_MAX_SINGLE_ALLOC a chained sg table will be setup. |
* |
**/ |
int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) |
{ |
int ret; |
|
ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, |
NULL, gfp_mask, sg_kmalloc); |
if (unlikely(ret)) |
__sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); |
|
return ret; |
} |
EXPORT_SYMBOL(sg_alloc_table); |
|
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|
|
void __sg_page_iter_start(struct sg_page_iter *piter, |
struct scatterlist *sglist, unsigned int nents, |
unsigned long pgoffset) |
{ |
piter->__pg_advance = 0; |
piter->__nents = nents; |
|
piter->sg = sglist; |
piter->sg_pgoffset = pgoffset; |
} |
EXPORT_SYMBOL(__sg_page_iter_start); |
|
static int sg_page_count(struct scatterlist *sg) |
{ |
return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; |
} |
|
bool __sg_page_iter_next(struct sg_page_iter *piter) |
{ |
if (!piter->__nents || !piter->sg) |
return false; |
|
piter->sg_pgoffset += piter->__pg_advance; |
piter->__pg_advance = 1; |
|
while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { |
piter->sg_pgoffset -= sg_page_count(piter->sg); |
piter->sg = sg_next(piter->sg); |
if (!--piter->__nents || !piter->sg) |
return false; |
} |
|
return true; |
} |
EXPORT_SYMBOL(__sg_page_iter_next); |
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