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Commit f3851786 authored by Prashant Bhole's avatar Prashant Bhole Committed by Daniel Borkmann
Browse files

lib/scatterlist: add sg_init_marker() helper 



sg_init_marker initializes sg_magic in the sg table and calls
sg_mark_end() on the last entry of the table. This can be useful to
avoid memset in sg_init_table() when scatterlist is already zeroed out

For example: when scatterlist is embedded inside other struct and that
container struct is zeroed out

Suggested-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarPrashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 1379ef82

include/linux/scatterlist.h

+18 −0
Original line number Diff line number Diff line
@@ -248,6 +248,24 @@ static inline void *sg_virt(struct scatterlist *sg) 
	return page_address(sg_page(sg)) + sg->offset;

}



/**

 * sg_init_marker - Initialize markers in sg table

 * @sgl:	   The SG table

 * @nents:	   Number of entries in table

 *

 **/

static inline void sg_init_marker(struct scatterlist *sgl,

				  unsigned int 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]);

}



int sg_nents(struct scatterlist *sg);

int sg_nents_for_len(struct scatterlist *sg, u64 len);

struct scatterlist *sg_next(struct scatterlist *);

lib/scatterlist.c

+1 −8
Original line number Diff line number Diff line
@@ -132,14 +132,7 @@ EXPORT_SYMBOL(sg_last); 
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]);

	sg_init_marker(sgl, nents);

}

EXPORT_SYMBOL(sg_init_table);