From: Martin K. Petersen <martin.petersen@oracle.com>
Date: Thu, 28 Sep 2017 01:38:59 +0000 (-0400)
Subject: scsi: sd: Do not override max_sectors_kb sysfs setting
X-Git-Tag: v4.1.12-124.31.3~158
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d8344b28f8c6537e8b801f5fc603fde23c0355de;p=users%2Fjedix%2Flinux-maple.git

scsi: sd: Do not override max_sectors_kb sysfs setting

A user may lower the max_sectors_kb setting in sysfs to accommodate
certain workloads. Previously we would always set the max I/O size to
either the block layer default or the optional preferred I/O size
reported by the device.

Keep the current heuristics for the initial setting of max_sectors_kb.
For subsequent invocations, only update the current queue limit if it
exceeds the capabilities of the hardware.

Orabug: 29596510

Cc: <stable@vger.kernel.org>
Reported-by: Don Brace <don.brace@microsemi.com>
Reviewed-by: Martin Wilck <mwilck@suse.com>
Tested-by: Don Brace <don.brace@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit 77082ca503bed061f7fbda7cfd7c93beda967a41)

Signed-off-by: John Sobecki <john.sobecki@oracle.com>
Tested-by: Dustin Samko <Dustin.Samko@gm.com>
Reviewed-by: Ritika Srivastava <ritika.srivastava@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>
---

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 9cd46eca3482..37b5accbad25 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2766,8 +2766,6 @@ static int sd_revalidate_disk(struct gendisk *disk)
 		sd_read_write_same(sdkp, buffer);
 	}
 
-	sdkp->first_scan = 0;
-
 	/*
 	 * We now have all cache related info, determine how we deal
 	 * with flush requests.
@@ -2782,7 +2780,7 @@ static int sd_revalidate_disk(struct gendisk *disk)
 	q->limits.max_dev_sectors = logical_to_sectors(sdp, dev_max);
 
 	/*
-	 * Use the device's preferred I/O size for reads and writes
+	 * Determine the device's preferred I/O size for reads and writes
 	 * unless the reported value is unreasonably small, large, or
 	 * garbage.
 	 */
@@ -2795,8 +2793,19 @@ static int sd_revalidate_disk(struct gendisk *disk)
 	} else
 		rw_max = BLK_DEF_MAX_SECTORS;
 
-	/* Combine with controller limits */
-	q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q));
+	/* Do not exceed controller limit */
+	rw_max = min(rw_max, queue_max_hw_sectors(q));
+
+	/*
+	 * Only update max_sectors if previously unset or if the current value
+	 * exceeds the capabilities of the hardware.
+	 */
+	if (sdkp->first_scan ||
+	    q->limits.max_sectors > q->limits.max_dev_sectors ||
+	    q->limits.max_sectors > q->limits.max_hw_sectors)
+		q->limits.max_sectors = rw_max;
+
+	sdkp->first_scan = 0;
 
 	set_capacity(disk, logical_to_sectors(sdp, sdkp->capacity));
 	sd_config_write_same(sdkp);