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lib/scatterlist: introduce sg_pcopy_from_buffer() and sg_pcopy_to_buffer()

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The only difference between sg_pcopy_{from,to}_buffer() and
sg_copy_{from,to}_buffer() is an additional argument that specifies the
number of bytes to skip the SG list before copying.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Horia Geanta <horia.geanta@freescale.com>
Cc: Imre Deak <imre.deak@intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Akinobu Mita 2013-07-08 16:01:54 -07:00 committed by Linus Torvalds
parent 1105200480
commit df642cea25
2 changed files with 88 additions and 5 deletions
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5
include/linux/scatterlist.h
View file

@ -244,6 +244,11 @@ size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen);
size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, off_t skip);
size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, off_t skip);
/*
* Maximum number of entries that will be allocated in one piece, if
* a list larger than this is required then chaining will be utilized.

88
lib/scatterlist.c
View file

@ -475,6 +475,43 @@ static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)
return true;
}
/**
* sg_miter_skip - reposition mapping iterator
* @miter: sg mapping iter to be skipped
* @offset: number of bytes to plus the current location
*
* Description:
* Sets the offset of @miter to its current location plus @offset bytes.
* If mapping iterator @miter has been proceeded by sg_miter_next(), this
* stops @miter.
*
* Context:
* Don't care if @miter is stopped, or not proceeded yet.
* Otherwise, preemption disabled if the SG_MITER_ATOMIC is set.
*
* Returns:
* true if @miter contains the valid mapping. false if end of sg
* list is reached.
*/
static bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset)
{
sg_miter_stop(miter);
while (offset) {
off_t consumed;
if (!sg_miter_get_next_page(miter))
return false;
consumed = min_t(off_t, offset, miter->__remaining);
miter->__offset += consumed;
miter->__remaining -= consumed;
offset -= consumed;
}
return true;
}
/**
* sg_miter_next - proceed mapping iterator to the next mapping
* @miter: sg mapping iter to proceed
@ -561,14 +598,16 @@ EXPORT_SYMBOL(sg_miter_stop);
* @nents: Number of SG entries
* @buf: Where to copy from
* @buflen: The number of bytes to copy
* @to_buffer: transfer direction (non zero == from an sg list to a
* buffer, 0 == from a buffer to an sg list
* @skip: Number of bytes to skip before copying
* @to_buffer: transfer direction (true == from an sg list to a
* buffer, false == from a buffer to an sg list
*
* Returns the number of copied bytes.
*
**/
static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, int to_buffer)
void *buf, size_t buflen, off_t skip,
bool to_buffer)
{
unsigned int offset = 0;
struct sg_mapping_iter miter;
@ -582,6 +621,9 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
sg_miter_start(&miter, sgl, nents, sg_flags);
if (!sg_miter_skip(&miter, skip))
return false;
local_irq_save(flags);
while (sg_miter_next(&miter) && offset < buflen) {
@ -616,7 +658,7 @@ static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents,
size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen)
{
return sg_copy_buffer(sgl, nents, buf, buflen, 0);
return sg_copy_buffer(sgl, nents, buf, buflen, 0, false);
}
EXPORT_SYMBOL(sg_copy_from_buffer);
@ -633,6 +675,42 @@ EXPORT_SYMBOL(sg_copy_from_buffer);
size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen)
{
return sg_copy_buffer(sgl, nents, buf, buflen, 1);
return sg_copy_buffer(sgl, nents, buf, buflen, 0, true);
}
EXPORT_SYMBOL(sg_copy_to_buffer);
/**
* sg_pcopy_from_buffer - Copy from a linear buffer to an SG list
* @sgl: The SG list
* @nents: Number of SG entries
* @buf: Where to copy from
* @skip: Number of bytes to skip before copying
* @buflen: The number of bytes to copy
*
* Returns the number of copied bytes.
*
**/
size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, off_t skip)
{
return sg_copy_buffer(sgl, nents, buf, buflen, skip, false);
}
EXPORT_SYMBOL(sg_pcopy_from_buffer);
/**
* sg_pcopy_to_buffer - Copy from an SG list to a linear buffer
* @sgl: The SG list
* @nents: Number of SG entries
* @buf: Where to copy to
* @skip: Number of bytes to skip before copying
* @buflen: The number of bytes to copy
*
* Returns the number of copied bytes.
*
**/
size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
void *buf, size_t buflen, off_t skip)
{
return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);
}
EXPORT_SYMBOL(sg_pcopy_to_buffer);