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Commit 0945e569 authored by Johannes Thumshirn's avatar Johannes Thumshirn Committed by Christoph Hellwig
Browse files

scatterlist: add sg_zero_buffer() helper 



The sg_zero_buffer() helper is used to zero fill an area in a SG
list.

Signed-off-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
[hch: renamed to sg_zero_buffer]
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent d19d4c8e

include/linux/scatterlist.h

+2 −0
Original line number Diff line number Diff line
@@ -278,6 +278,8 @@ size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 
			    const 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);

size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,

		       size_t buflen, off_t skip);



/*

 * Maximum number of entries that will be allocated in one piece, if

lib/scatterlist.c

+35 −0
Original line number Diff line number Diff line
@@ -751,3 +751,38 @@ size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 
	return sg_copy_buffer(sgl, nents, buf, buflen, skip, true);

}

EXPORT_SYMBOL(sg_pcopy_to_buffer);



/**

 * sg_zero_buffer - Zero-out a part of a SG list

 * @sgl:		 The SG list

 * @nents:		 Number of SG entries

 * @buflen:		 The number of bytes to zero out

 * @skip:		 Number of bytes to skip before zeroing

 *

 * Returns the number of bytes zeroed.

 **/

size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents,

		       size_t buflen, off_t skip)

{

	unsigned int offset = 0;

	struct sg_mapping_iter miter;

	unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG;



	sg_miter_start(&miter, sgl, nents, sg_flags);



	if (!sg_miter_skip(&miter, skip))

		return false;



	while (offset < buflen && sg_miter_next(&miter)) {

		unsigned int len;



		len = min(miter.length, buflen - offset);

		memset(miter.addr, 0, len);



		offset += len;

	}



	sg_miter_stop(&miter);

	return offset;

}

EXPORT_SYMBOL(sg_zero_buffer);