/*
* 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/slab.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 CONFIG_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)
skip_first_chunk = false;
else
free_fn(sgl, alloc_size);
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 CONFIG_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);
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);