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| author | Jeff Garzik <jeff@garzik.org> | 2007-10-18 16:21:18 -0400 |
|---|---|---|
| committer | Jeff Garzik <jeff@garzik.org> | 2007-10-18 16:21:18 -0400 |
| commit | 3be6cbd73f74b4a3da82cc7d6e1688a4ae595fc7 (patch) | |
| tree | a077cf70d1cd438db34f5def23dd8f72f42b5a8c /drivers/ata/sata_sil24.c | |
| parent | 858c9c406688bc7244986b5836265071edfd1d3f (diff) | |
| download | lwn-3be6cbd73f74b4a3da82cc7d6e1688a4ae595fc7.tar.gz lwn-3be6cbd73f74b4a3da82cc7d6e1688a4ae595fc7.zip | |
[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>
Diffstat (limited to 'drivers/ata/sata_sil24.c')
| -rw-r--r-- | drivers/ata/sata_sil24.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/ata/sata_sil24.c b/drivers/ata/sata_sil24.c index b0619278454a..26ebffc10f3e 100644 --- a/drivers/ata/sata_sil24.c +++ b/drivers/ata/sata_sil24.c @@ -796,16 +796,19 @@ static inline void sil24_fill_sg(struct ata_queued_cmd *qc, 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) |