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[libata] kill ata_sg_is_last()

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Short term, this works around a bug introduced by early sg-chaining
work.

Long term, removing this function eliminates a branch from a hot
path loop in each scatter/gather table build.  Also, as this code
demonstrates, we don't need to _track_ the end of the s/g list, as
long as we mark it in some way.  And doing so programatically is nice.
So its a useful cleanup, regardless of its short term effects.

Based conceptually on a quick patch by Jens Axboe.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
This commit is contained in:
Jeff Garzik
2007-10-18 16:21:18 -04:00
parent 858c9c4066
commit 3be6cbd73f
5 changed files with 27 additions and 42 deletions
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12
include/linux/libata.h
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@@ -1037,18 +1037,6 @@ extern void ata_port_pbar_desc(struct ata_port *ap, int bar, ssize_t offset,
/*
* qc helpers
*/
static inline int
ata_sg_is_last(struct scatterlist *sg, struct ata_queued_cmd *qc)
{
if (sg == &qc->pad_sgent)
return 1;
if (qc->pad_len)
return 0;
if (qc->n_iter == qc->n_elem)
return 1;
return 0;
}
static inline struct scatterlist *
ata_qc_first_sg(struct ata_queued_cmd *qc)
{