James Bottomley wrote:
On Sun, 2007-06-03 at 10:45 +0300, Boaz Harrosh wrote:
Jeff Garzik wrote:
Boaz Harrosh wrote:
FUJITA Tomonori wrote:
From: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
Subject: Re: [PATCH v2] add bidi support for block pc requests
Date: Thu, 17 May 2007 17:00:21 +0300
Yes Tomo found it at ata_scsi_slave_config(). Attached below the way I
fixed it. Now it works with 127.
I think that we can just remove blk_queue_max_phys_segments since the
ata drivers seem to set sg_tablesize to LIBATA_MAX_PRD.
Who should send a patch upstream? (I cc'ed Jeff Garzik)
Boaz
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index dd81fa7..3660f3e 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -800,8 +800,6 @@ int ata_scsi_slave_config(struct scsi_device *sdev)
ata_scsi_sdev_config(sdev);
- blk_queue_max_phys_segments(sdev->request_queue, LIBATA_MAX_PRD);
-
sdev->manage_start_stop = 1;
I don't mind the patch, but could someone refresh me as to the context?
Is there something wrong with the above code, or is it simply redundant
to the scsi_host_template settings in each LLDD?
Jeff
Hi Jeff
What happens is that if SCSI-ml sets an higher value than LIBATA_MAX_PRD (=128)
than every thing is OK and libata-scsi will only see its LIBATA_MAX_PRD. But what
happens if SCSI-ml sets a lower value? It will than crash on unexpected high sg
count. My first Patch was an "if >" but Tomo said that it is redundant since
drivers do that already. So I guess it is your call. Can it be removed or we need
a: if ( sdev->request_queue->max_phys_segments > LIBATA_MAX_PRD)
Ordinarily, in SCSI, phys_segments is the wrong thing for a driver to
set because what a driver wants to see is what comes out the other side
of dma_map_sg() (which is controlled by hw_segments) not what goes in.
However, I could see libata having an interest in the phys_segments if
the physical region descriptors are going to the device via PIO ... is
that what this is for?
LIBATA_MAX_PRD is the maximum number of DMA scatter/gather elements
permitted by the HBA's DMA engine, for a single ATA command.
The PIO code doesn't really care about segments.
Jeff
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