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FAILED: patch "[PATCH] scsi: sd: Do not override max_sectors_kb sysfs setting" failed to apply to 3.18-stable tree

PATCH [email protected] 1 participant 1 message Oct 10, 2017

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The patch below does not apply to the 3.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 77082ca503bed061f7fbda7cfd7c93beda967a41 Mon Sep 17 00:00:00 2001

From: "Martin K. Petersen" <[email protected]>
Date: Wed, 27 Sep 2017 21:38:59 -0400
Subject: [PATCH] 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.

Cc <[email protected]>
Reported-by Don Brace <[email protected]>
Reviewed-by Martin Wilck <[email protected]>
Tested-by Don Brace <[email protected]>
Signed-off-by Martin K. Petersen <[email protected]>
drivers/scsi/sd.c +14 -5
index 3d26a729825c..d175c5c5ccf8 100644
@@ -3107,8 +3107,6 @@ static int sd_revalidate_disk(struct gendisk *disk)
 		sd_read_security(sdkp, buffer);
 	}
 
-	sdkp->first_scan = 0;
-
 	/*
 	 * We now have all cache related info, determine how we deal
 	 * with flush requests.

@@ -3123,7 +3121,7 @@ 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.
 	 */

@@ -3137,8 +3135,19 @@ static int sd_revalidate_disk(struct gendisk *disk)
 		rw_max = min_not_zero(logical_to_sectors(sdp, dev_max),
 				      (sector_t)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);