Commit 9c1d9c20 authored Dec 16, 2015 by Martin K. Petersen

sd: Reject optimal transfer length smaller than page size



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>

parent 1c69d3b6

drivers/scsi/sd.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -2885,10 +2885,13 @@ 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