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scatterlist: add sg_nents

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Useful helper to know the number of entries in scatterlist.

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Cc: Alex Dubov <oakad@yahoo.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Maxim Levitsky 2012-09-27 12:45:28 +02:00 committed by Jens Axboe
parent c2b1ad800b
commit 2e48461029
2 changed files with 23 additions and 0 deletions
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1
include/linux/scatterlist.h
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@ -201,6 +201,7 @@ static inline void *sg_virt(struct scatterlist *sg)
return page_address(sg_page(sg)) + sg->offset; return page_address(sg_page(sg)) + sg->offset;
} }
int sg_nents(struct scatterlist *sg);
struct scatterlist *sg_next(struct scatterlist *); struct scatterlist *sg_next(struct scatterlist *);
struct scatterlist *sg_last(struct scatterlist *s, unsigned int); struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
void sg_init_table(struct scatterlist *, unsigned int); void sg_init_table(struct scatterlist *, unsigned int);

22
lib/scatterlist.c
View File

@ -38,6 +38,28 @@ struct scatterlist *sg_next(struct scatterlist *sg)
} }
EXPORT_SYMBOL(sg_next); EXPORT_SYMBOL(sg_next);
/**
* sg_nents - return total count of entries in scatterlist
* @sg: The scatterlist
*
* Description:
* Allows to know how many entries are in sg, taking into acount
* chaining as well
*
**/
int sg_nents(struct scatterlist *sg)
{
int nents = 0;
while (sg) {
nents++;
sg = sg_next(sg);
}
return nents;
}
EXPORT_SYMBOL(sg_nents);
/** /**
* sg_last - return the last scatterlist entry in a list * sg_last - return the last scatterlist entry in a list
* @sgl: First entry in the scatterlist * @sgl: First entry in the scatterlist