sd: Fix max transfer length for 4k disks

The following patch fixes an issue observed with 4k sector disks
where the max_hw_sectors attribute was getting set too large in
sd_revalidate_disk. Since sdkp->max_xfer_blocks is in units
of SCSI logical blocks and queue_max_hw_sectors is in units of
512 byte blocks, on a 4k sector disk, every time we went through
sd_revalidate_disk, we were taking the current value of
queue_max_hw_sectors and increasing it by a factor of 8. Fix
this by only shifting sdkp->max_xfer_blocks.

Cc: stable@vger.kernel.org
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 399516925d80..05ea0d49a3a3 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2800,9 +2800,11 @@ static int sd_revalidate_disk(struct gendisk *disk)
          */
         sd_set_flush_flag(sdkp);
 
-        max_xfer = min_not_zero(queue_max_hw_sectors(sdkp->disk->queue),
-                                sdkp->max_xfer_blocks);
+        max_xfer = sdkp->max_xfer_blocks;
         max_xfer <<= ilog2(sdp->sector_size) - 9;
+
+        max_xfer = min_not_zero(queue_max_hw_sectors(sdkp->disk->queue),
+                                max_xfer);
         blk_queue_max_hw_sectors(sdkp->disk->queue, max_xfer);
         set_capacity(disk, sdkp->capacity);
         sd_config_write_same(sdkp);