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scsi: sd: Do not override max_sectors_kb sysfs setting

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commit 77082ca503bed061f7fbda7cfd7c93beda967a41 upstream.

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.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Martin K. Petersen 2017-09-27 21:38:59 -04:00 committed by Greg Kroah-Hartman
parent aee20f321d
commit 12b182a35f
1 changed files with 14 additions and 5 deletions

19
drivers/scsi/sd.c

@ -2867,8 +2867,6 @@ 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.
@ -2883,7 +2881,7 @@ 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.
*/
@ -2897,8 +2895,19 @@ 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);