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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/scsi/ipr.c | |
| parent | Update libata driver for bf548 atapi controller against the 2.6.24 tree. (diff) | |
| download | linux-dev-3be6cbd73f74b4a3da82cc7d6e1688a4ae595fc7.tar.xz linux-dev-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/scsi/ipr.c')
| -rw-r--r-- | drivers/scsi/ipr.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c index b41dfb539021..c316a0bcae6c 100644 --- a/drivers/scsi/ipr.c +++ b/drivers/scsi/ipr.c @@ -5134,6 +5134,7 @@ static void ipr_build_ata_ioadl(struct ipr_cmnd *ipr_cmd, u32 ioadl_flags = 0; struct ipr_ioarcb *ioarcb = &ipr_cmd->ioarcb; struct ipr_ioadl_desc *ioadl = ipr_cmd->ioadl; + struct ipr_ioadl_desc *last_ioadl = NULL; int len = qc->nbytes + qc->pad_len; struct scatterlist *sg; @@ -5156,11 +5157,13 @@ static void ipr_build_ata_ioadl(struct ipr_cmnd *ipr_cmd, ata_for_each_sg(sg, qc) { ioadl->flags_and_data_len = cpu_to_be32(ioadl_flags | sg_dma_len(sg)); ioadl->address = cpu_to_be32(sg_dma_address(sg)); - if (ata_sg_is_last(sg, qc)) - ioadl->flags_and_data_len |= cpu_to_be32(IPR_IOADL_FLAGS_LAST); - else - ioadl++; + + last_ioadl = ioadl; + ioadl++; } + + if (likely(last_ioadl)) + last_ioadl->flags_and_data_len |= cpu_to_be32(IPR_IOADL_FLAGS_LAST); } /** |