On Fri, Sep 18 2009 at 12:24pm -0400,
Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx> wrote:
> This patch is a preparation for the last patch in this patchset
> which changes blk_set_default_limits() to set 0 to max_sectors.
should read: changes blk_set_default_limits() to set max_sectors to 0.
> dm uses blk_stack_limits() to merge limits of underlying devices
> and copy the end result to the queue.
> But if there's no underlying device (like 'zero' target),
> max_sectors/max_hw_sectors are left unchanged from the default 0
> and just copying it to the queue causes problems.
>
> Provide blk_queue_copy_limits() to get a safe copy with
> invalid values fixed-up.
>
> Signed-off-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx>
> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx>
> Cc: David Strand <dpstrand@xxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Cc: Alasdair G Kergon <agk@xxxxxxxxxx>
> Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
> ---
> block/blk-settings.c | 28 ++++++++++++++++++++++++++++
> include/linux/blkdev.h | 1 +
> 2 files changed, 29 insertions(+)
>
> Index: linux-2.6.31.work/block/blk-settings.c
> ===================================================================
> --- linux-2.6.31.work.orig/block/blk-settings.c
> +++ linux-2.6.31.work/block/blk-settings.c
> @@ -122,6 +122,34 @@ void blk_set_default_limits(struct queue
> EXPORT_SYMBOL(blk_set_default_limits);
>
> /**
> + * blk_queue_copy_limits - copy limits to queue
> + * @q: the request queue whose limits as a copy destination
> + * @lim: the queue_limits structure as a copy source
> + *
> + * Description:
> + * Copies a queue_limit struct contents to @q with fix-ups to
> + * invalid values.
> + */
> +void blk_queue_copy_limits(struct request_queue *q, struct queue_limits
> *lim)
> +{
> + q->limits = *lim;
> +
> + /*
> + * blk_set_default_limits() sets 0 to max_sectors/max_hw_sectors
> + * so that blk_stack_limits() appropriately propagate the values
> + * of lower-stack by min_not_zero().
> + * However, if the default value 0 is unchanged (e.g. the stacking
> + * device is virtual and has no underlying device), it results
> + * in unusable device.
Likewise:
blk_set_default_limits() sets max_sectors/max_hw_sectors to 0?
> + * Check if max_sectors/max_hw_sectors have non-zero values,
> + * and set SAFE_MAX_SECTORS if they do.
> + */
> + if (q->limits.max_sectors == 0 || q->limits.max_hw_sectors == 0)
> + blk_queue_max_sectors(q, SAFE_MAX_SECTORS);
Shouldn't this check (and the entire comment above it) get added in the
3rd patch once max_sectors/max_hw_sectors sre actually set to 0? I'm
being really pedantic here but...
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