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| author | James Bottomley | 2008-01-01 17:00:10 +0100 |
|---|---|---|
| committer | James Bottomley | 2008-01-12 01:29:22 +0100 |
| commit | 465ff3185e0cb76d46137335a4d21d0d9d3ac8a2 (patch) | |
| tree | 171068cd7d99600cd094c2eb72bac712649fd9eb /drivers/scsi | |
| parent | [SCSI] block: Introduce new blk_queue_update_dma_alignment interface (diff) | |
| download | kernel-qcow2-linux-465ff3185e0cb76d46137335a4d21d0d9d3ac8a2.tar.gz kernel-qcow2-linux-465ff3185e0cb76d46137335a4d21d0d9d3ac8a2.tar.xz kernel-qcow2-linux-465ff3185e0cb76d46137335a4d21d0d9d3ac8a2.zip | |
[SCSI] relax scsi dma alignment
This patch relaxes the default SCSI DMA alignment from 512 bytes to 4
bytes. I remember from previous discussions that usb and firewire have
sector size alignment requirements, so I upped their alignments in the
respective slave allocs.
The reason for doing this is so that we don't get such a huge amount of
copy overhead in bio_copy_user() for udev. (basically all inquiries it
issues can now be directly mapped).
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Diffstat (limited to 'drivers/scsi')
| -rw-r--r-- | drivers/scsi/scsi_lib.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index db52222885b7..de601370c05b 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1668,6 +1668,14 @@ struct request_queue *__scsi_alloc_queue(struct Scsi_Host *shost, if (!shost->use_clustering) clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags); + + /* + * set a reasonable default alignment on word boundaries: the + * host and device may alter it using + * blk_queue_update_dma_alignment() later. + */ + blk_queue_dma_alignment(q, 0x03); + return q; } EXPORT_SYMBOL(__scsi_alloc_queue); |