[libata] kill ata_sg_is_last()
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>
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c
index b061927..26ebffc 100644
--- a/drivers/ata/sata_sil24.c
+++ b/drivers/ata/sata_sil24.c
@@ -796,16 +796,19 @@
struct sil24_sge *sge)
{
struct scatterlist *sg;
+ struct sil24_sge *last_sge = NULL;
ata_for_each_sg(sg, qc) {
sge->addr = cpu_to_le64(sg_dma_address(sg));
sge->cnt = cpu_to_le32(sg_dma_len(sg));
- if (ata_sg_is_last(sg, qc))
- sge->flags = cpu_to_le32(SGE_TRM);
- else
- sge->flags = 0;
+ sge->flags = 0;
+
+ last_sge = sge;
sge++;
}
+
+ if (likely(last_sge))
+ last_sge->flags = cpu_to_le32(SGE_TRM);
}
static int sil24_qc_defer(struct ata_queued_cmd *qc)