remove blk_queue_max_phys_segments in libata

LIBATA_MAX_PRD is the maximum number of DMA scatter/gather elements
permitted by the HBA's DMA engine. It's properly set to
q->max_hw_segments via the sg_tablesize parameter.

libata shouldn't call blk_queue_max_phys_segments. Now LIBATA_MAX_PRD
is equal to SCSI_MAX_PHYS_SEGMENTS by default (both is 128), so
everything is fine. But if they are changed, some code (like the scsi
mid layer, sg chaining, etc) might not work properly.

(Addition from Jens) The basic issue is that the physical segment
setting is purely a driver issue. And since SCSI is managing the sglist,
libata has no business changing the setting. All libata should care
about is the hw segment setting.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index d63c81ed084f7d016c70b55448804f0ad60d554e..ba62d534f32b91c401f99939a7193a7a2c975bdf 100644 (file)
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -801,8 +801,6 @@ 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;
 
        if (dev)