On Mon, 5 Jan 2004, Jens Axboe wrote:
> On Sun, Jan 04 2004, Matthew Dharm wrote:
> > Is there any indication that the SCSI parts of this patch will get
> > accepted?
>
> I'm fine with the patch, FWIW, just move it to scsi_alloc_queue()
> instead?
Here's the revised patch.
Alan Stern
===== scsiglue.c 1.60 vs edited =====
--- 1.60/drivers/usb/storage/scsiglue.c Fri Oct 24 14:53:38 2003
+++ edited/drivers/usb/storage/scsiglue.c Fri Nov 21 12:45:21 2003
@@ -65,6 +65,16 @@
static int slave_configure (struct scsi_device *sdev)
{
+ /* Scatter-gather buffers (all but the last) must have a length
+ * divisible by the bulk maxpacket size. Otherwise a data packet
+ * would end up being short, causing a premature end to the data
+ * transfer. Since high-speed bulk pipes have a maxpacket size
+ * of 512, we'll use that as the scsi device queue's DMA alignment
+ * mask. Guaranteeing proper alignment of the first buffer will
+ * have the desired effect because, except at the beginning and
+ * the end, scatter-gather buffers follow page boundaries. */
+ blk_queue_dma_alignment(sdev->request_queue, (512 - 1));
+
/* this is to satisify the compiler, tho I don't think the
* return code is ever checked anywhere. */
return 0;
===== sg.c 1.48 vs edited =====
--- 1.48/drivers/scsi/sg.c Fri Oct 24 14:53:37 2003
+++ edited/drivers/scsi/sg.c Fri Nov 21 12:28:52 2003
@@ -1741,7 +1741,11 @@
int sg_tablesize = sfp->parentdp->sg_tablesize;
struct scatterlist *sgl;
int mx_sc_elems, res;
+ struct scsi_device *sdev = sfp->parentdp->device;
+ if (((unsigned long)hp->dxferp &
+ queue_dma_alignment(sdev->request_queue)) != 0)
+ return 1;
mx_sc_elems = sg_build_sgat(schp, sfp, sg_tablesize);
if (mx_sc_elems <= 0) {
return 1;
===== st.c 1.45 vs edited =====
--- 1.45/drivers/scsi/st.c Fri Sep 5 12:16:40 2003
+++ edited/drivers/scsi/st.c Fri Nov 21 12:30:34 2003
@@ -1267,7 +1267,8 @@
i = STp->try_dio && try_rdio;
else
i = STp->try_dio && try_wdio;
- if (i) {
+ if (i && ((unsigned int)buf & queue_dma_alignment(
+ STp->device->request_queue)) == 0) {
i = st_map_user_pages(&(STbp->sg[0]), STbp->use_sg,
(unsigned long)buf, count, (is_read ? READ :
WRITE),
STp->max_pfn);
===== scsi_lib.c 1.49 vs edited =====
--- 1.49/drivers/scsi/scsi_lib.c Sat Nov 22 11:20:45 2003
+++ edited/drivers/scsi/scsi_lib.c Mon Jan 5 16:55:32 2004
@@ -1287,6 +1287,15 @@
blk_queue_max_sectors(q, shost->max_sectors);
blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
blk_queue_segment_boundary(q, shost->dma_boundary);
+
+ /*
+ * Set the queue's mask to require a mere 8-byte alignment for
+ * DMA buffers, rather than the default 512. This shouldn't
+ * inconvenience any user programs and should be okay for most
+ * host adapters. A host driver can alter this mask in its
+ * slave_alloc() or slave_configure() callback if necessary.
+ */
+ blk_queue_dma_alignment(sdev->request_queue, (8 - 1));
if (!shost->use_clustering)
clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
-------------------------------------------------------
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