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lib/scatterlist: add sg_init_marker() helper

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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: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Prashant Bhole 2018-03-30 09:20:59 +09:00 committed by Daniel Borkmann
parent 1379ef828a
commit f385178679
2 changed files with 19 additions and 8 deletions
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18
include/linux/scatterlist.h
View File

@ -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 *);

9
lib/scatterlist.c
View File

@ -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);