sd: Reject optimal transfer length smaller than page size

Orabug: 23615929

(commit 9c1d9c207bb800498347a2716da298043ee280c5 of upstream)
Eryu Guan reported that loading scsi_debug would fail. This turned out
to be caused by scsi_debug reporting an optimal I/O size of 32KB which
is smaller than the 64KB page size on the PowerPC system in question.

Add a check to ensure that we only use the device-reported OPTIMAL
TRANSFER LENGTH if it is bigger than or equal to the page cache size.

Reported-by: Eryu Guan <guaneryu@gmail.com>
Reported-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Joe Jin <joe.jin@oracle.com>

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 4cd30d95ac310cff327a42ab523fc1313bfde161..1af23d34864ae645bd2b2bd6f7ad1eb4d80c6c50 100644 (file)
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2775,10 +2775,13 @@ static int sd_revalidate_disk(struct gendisk *disk)
 
        /*
         * Use the device's preferred I/O size for reads and writes
-        * unless the reported value is unreasonably large (or garbage).
+        * unless the reported value is unreasonably small, large, or
+        * garbage.
         */
-       if (sdkp->opt_xfer_blocks && sdkp->opt_xfer_blocks <= dev_max &&
-           sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS)
+       if (sdkp->opt_xfer_blocks &&
+           sdkp->opt_xfer_blocks <= dev_max &&
+           sdkp->opt_xfer_blocks <= SD_DEF_XFER_BLOCKS &&
+           sdkp->opt_xfer_blocks * sdp->sector_size >= PAGE_CACHE_SIZE)
                rw_max = q->limits.io_opt =
                        logical_to_sectors(sdp, sdkp->opt_xfer_blocks);
        else