[PATCH] sd: Consider max_xfer_blocks if opt_xfer_blocks is unusable

[Fam Zheng]

If device reports a small max_xfer_blocks and a zero opt_xfer_blocks, we
end up using BLK_DEF_MAX_SECTORS, which is wrong and r/w of that size
may get error.

Fixes: ca369d51b3e ("block/sd: Fix device-imposed transfer length limits")
Signed-off-by: Fam Zheng <f...@redhat.com>
---
 drivers/scsi/sd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index fcfeddc..e2e21ab 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2957,6 +2957,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
                rw_max = logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
        } else
                rw_max = BLK_DEF_MAX_SECTORS;
+       rw_max = min_not_zero(rw_max, dev_max);
 
        /* Combine with controller limits */
        q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q));
-- 
2.9.3