On Fri, 2015-04-10 at 02:08 -0500, michaelc@xxxxxxxxxxx wrote:
> From: Mike Christie <michaelc@xxxxxxxxxxx>
>
> If the user has set max_sectors in sysfs, but the disk is revalidated
> due to it being removable or having write protections and it being
> opened, or dm/md claiming it, or something like a scsi rescan, etc,
> then we are overwriting the user specified max_sectors value. This patch
> only has us set the max_sectors if the new max_hw_sectors is smaller
> or if the user has not changed max_sectors.
>
> Signed-off-by: Mike Christie <michaelc@xxxxxxxxxxx>
> ---
> block/blk-settings.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 12600bf..d6c7b0c 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -248,6 +248,10 @@ EXPORT_SYMBOL(blk_queue_bounce_limit);
> * filesystem type requests. This value can be overridden on a
> * per-device basis in /sys/block/<device>/queue/max_sectors_kb.
> * The soft limit can not exceed max_hw_sectors.
> + *
> + * If this is called as a result of a revalidation then we will only
> + * override the user specified max_sectors if the new max_hw_sectors is
> + * smaller.
> **/
> void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_sectors)
> {
> @@ -257,7 +261,11 @@ void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_
> __func__, max_hw_sectors);
> }
>
> - limits->max_sectors = limits->max_hw_sectors = max_hw_sectors;
> + if (limits->max_sectors == limits->max_hw_sectors ||
> + max_hw_sectors < limits->max_sectors)
> + limits->max_sectors = limits->max_hw_sectors = max_hw_sectors;
> + else
> + limits->max_hw_sectors = max_hw_sectors;
> }
> EXPORT_SYMBOL(blk_limits_max_hw_sectors);
>
Thanks for posting this, Mike.
(For some context, this fixes a problem where a user had a storage
array connected via iSCSI that reported incorrect information in the
block limits VPD page, and generated an error on a large write. Setting
max_sectors_kb via sysfs didn't fix it because the value was being
overwritten when the iSCSI connection was re-established.)
Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>
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