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Commit 11052004 authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
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lib/scatterlist: factor out sg_miter_get_next_page() from sg_miter_next() 



This patchset introduces sg_pcopy_from_buffer() and sg_pcopy_to_buffer(),
which copy data between a linear buffer and an SG list.

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.

The main reason for introducing these functions is to fix a problem in
scsi_debug module.  And there is a local function in crypto/talitos
module, which can be replaced by sg_pcopy_to_buffer().

This patch:

sg_miter_get_next_page() is used to proceed page iterator to the next page
if necessary, and will be used to implement the variants of
sg_copy_{from,to}_buffer() later.

Signed-off-by: default avatarAkinobu Mita <akinobu.mita@gmail.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Horia Geanta <horia.geanta@freescale.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0ea8530d

lib/scatterlist.c

+24 −15
Original line number Original line Diff line number Diff line
@@ -453,6 +453,28 @@ void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 
}

}

EXPORT_SYMBOL(sg_miter_start);

EXPORT_SYMBOL(sg_miter_start);





static bool sg_miter_get_next_page(struct sg_mapping_iter *miter)

{

	if (!miter->__remaining) {

		struct scatterlist *sg;

		unsigned long pgoffset;



		if (!__sg_page_iter_next(&miter->piter))

			return false;



		sg = miter->piter.sg;

		pgoffset = miter->piter.sg_pgoffset;



		miter->__offset = pgoffset ? 0 : sg->offset;

		miter->__remaining = sg->offset + sg->length -

				(pgoffset << PAGE_SHIFT) - miter->__offset;

		miter->__remaining = min_t(unsigned long, miter->__remaining,

					   PAGE_SIZE - miter->__offset);

	}



	return true;

}



/**

/**

 * sg_miter_next - proceed mapping iterator to the next mapping

 * sg_miter_next - proceed mapping iterator to the next mapping

 * @miter: sg mapping iter to proceed

 * @miter: sg mapping iter to proceed
@@ -478,22 +500,9 @@ bool sg_miter_next(struct sg_mapping_iter *miter) 
	 * Get to the next page if necessary.

	 * Get to the next page if necessary.

	 * __remaining, __offset is adjusted by sg_miter_stop

	 * __remaining, __offset is adjusted by sg_miter_stop

	 */

	 */

	if (!miter->__remaining) {

	if (!sg_miter_get_next_page(miter))

		struct scatterlist *sg;

		unsigned long pgoffset;



		if (!__sg_page_iter_next(&miter->piter))

		return false;

		return false;





		sg = miter->piter.sg;

		pgoffset = miter->piter.sg_pgoffset;



		miter->__offset = pgoffset ? 0 : sg->offset;

		miter->__remaining = sg->offset + sg->length -

				(pgoffset << PAGE_SHIFT) - miter->__offset;

		miter->__remaining = min_t(unsigned long, miter->__remaining,

					   PAGE_SIZE - miter->__offset);

	}

	miter->page = sg_page_iter_page(&miter->piter);

	miter->page = sg_page_iter_page(&miter->piter);

	miter->consumed = miter->length = miter->__remaining;

	miter->consumed = miter->length = miter->__remaining;