Commit 77082ca5 authored by Martin K. Petersen's avatar Martin K. Petersen
Browse files

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: <stable@vger.kernel.org>
Reported-by: default avatarDon Brace <don.brace@microsemi.com>
Reviewed-by: default avatarMartin Wilck <mwilck@suse.com>
Tested-by: default avatarDon Brace <don.brace@microsemi.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 28a0bc41

drivers/scsi/sd.c

+14 −5
Original line number Diff line number Diff line
@@ -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);

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