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). Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> --- This patch depends on the prior patch: block: Introduce new blk_queue_update_dma_alignment interface diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 571fba5..db627a4 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -824,6 +824,9 @@ static void ata_scsi_sdev_config(struct scsi_device *sdev) * requests. */ sdev->max_device_blocked = 1; + + /* set the min alignment */ + blk_queue_update_dma_alignment(sdev->request_queue, ATA_DMA_PAD_MASK); } static void ata_scsi_dev_config(struct scsi_device *sdev, @@ -868,7 +871,7 @@ int ata_scsi_slave_config(struct scsi_device *sdev) if (dev) ata_scsi_dev_config(sdev, dev); - return 0; /* scsi layer doesn't check return value, sigh */ + return 0; } /** diff --git a/drivers/firewire/fw-sbp2.c b/drivers/firewire/fw-sbp2.c index 624ff3e..c2169d2 100644 --- a/drivers/firewire/fw-sbp2.c +++ b/drivers/firewire/fw-sbp2.c @@ -1238,6 +1238,12 @@ static int sbp2_scsi_slave_alloc(struct scsi_device *sdev) sdev->allow_restart = 1; + /* + * Update the dma alignment (minimum alignment requirements for + * start and end of DMA transfers) to be a sector + */ + blk_queue_update_dma_alignment(sdev->request_queue, 511); + if (lu->tgt->workarounds & SBP2_WORKAROUND_INQUIRY_36) sdev->inquiry_len = 36; diff --git a/drivers/ieee1394/sbp2.c b/drivers/ieee1394/sbp2.c index b83d254..1eda11a 100644 --- a/drivers/ieee1394/sbp2.c +++ b/drivers/ieee1394/sbp2.c @@ -1963,6 +1963,12 @@ static int sbp2scsi_slave_alloc(struct scsi_device *sdev) lu->sdev = sdev; sdev->allow_restart = 1; + /* + * Update the dma alignment (minimum alignment requirements for + * start and end of DMA transfers) to be a sector + */ + blk_queue_update_dma_alignment(sdev->request_queue, 511); + if (lu->workarounds & SBP2_WORKAROUND_INQUIRY_36) sdev->inquiry_len = 36; return 0; diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index d1a4671..0aa5296 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1667,6 +1667,14 @@ 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); diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c index 7c9593b..39c03f9 100644 --- a/drivers/usb/storage/scsiglue.c +++ b/drivers/usb/storage/scsiglue.c @@ -82,6 +82,12 @@ static int slave_alloc (struct scsi_device *sdev) sdev->inquiry_len = 36; /* + * Update the dma alignment (minimum alignment requirements for + * start and end of DMA transfers) to be a sector + */ + blk_queue_update_dma_alignment(sdev->request_queue, 511); + + /* * The UFI spec treates the Peripheral Qualifier bits in an * INQUIRY result as reserved and requires devices to set them * to 0. However the SCSI spec requires these bits to be set - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
