USB: usb-storage: increase max_sectors for tape drives

This patch (as1203) increases the max_sector limit for USB tape
drives.  By default usb-storage sets max_sectors to 240 (i.e., 120 KB)
for all devices.  But tape drives need a higher limit, since tapes can
and do have very large block sizes.  Without the ability to transfer
an entire large block in a single command, such tapes can't be used.

This fixes Bugzilla #12207.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Phil Mitchell <philipm@sybase.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 727c506..ed710bc 100644 (file)
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -135,6 +135,12 @@ static int slave_configure(struct scsi_device *sdev)
                if (sdev->request_queue->max_sectors > max_sectors)
                        blk_queue_max_sectors(sdev->request_queue,
                                              max_sectors);
+       } else if (sdev->type == TYPE_TAPE) {
+               /* Tapes need much higher max_sector limits, so just
+                * raise it to the maximum possible (4 GB / 512) and
+                * let the queue segment size sort out the real limit.
+                */
+               blk_queue_max_sectors(sdev->request_queue, 0x7FFFFF);
        }
 
        /* Some USB host controllers can't do DMA; they have to use PIO.