Commit df642cea authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
Browse files

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



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: default avatarAkinobu 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: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 11052004

include/linux/scatterlist.h

+5 −0
Original line number Diff line number Diff line
@@ -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.

lib/scatterlist.c

+83 −5
Original line number Diff line number Diff line
@@ -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);

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