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scatterlist: introduce sg_unmark_end

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This is useful in places that recycle the same scatterlist multiple
times, and do not want to incur the cost of sg_init_table every
time in hot paths.

Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Paolo Bonzini 2013-03-20 15:37:08 +10:30 committed by Rusty Russell
parent 0d2e1a2926
commit c8164d8931
3 changed files with 18 additions and 2 deletions
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2
block/blk-integrity.c
View File

@ -110,7 +110,7 @@ int blk_rq_map_integrity_sg(struct request_queue *q, struct bio *bio,
if (!sg)
sg = sglist;
else {
sg->page_link &= ~0x02;
sg_unmark_end(sg);
sg = sg_next(sg);
}

2
block/blk-merge.c
View File

@ -143,7 +143,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
* termination bit to avoid doing a full
* sg_init_table() in drivers for each command.
*/
(*sg)->page_link &= ~0x02;
sg_unmark_end(*sg);
*sg = sg_next(*sg);
}

16
include/linux/scatterlist.h
View File

@ -171,6 +171,22 @@ static inline void sg_mark_end(struct scatterlist *sg)
sg->page_link &= ~0x01;
}
/**
* sg_unmark_end - Undo setting the end of the scatterlist
* @sg: SG entryScatterlist
*
* Description:
* Removes the termination marker from the given entry of the scatterlist.
*
**/
static inline void sg_unmark_end(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
sg->page_link &= ~0x02;
}
/**
* sg_phys - Return physical address of an sg entry
* @sg: SG entry