Re: [dm-devel] [PATCH v2 1/3] block: add sysfs entry for discard_alignment

Vivek Goyal
2012-07-03T14:40:03Z

On Tue, Jul 03, 2012 at 04:21:34PM +0200, Paolo Bonzini wrote:

[..]
> > That raises an interesting question for patch3. If the discard is happening to
> > a partition, shouldn't you be looking at partition discard_alignment
> > instead of always looking at queue discard_alignment?
>
> Good point! Like this?

This looks better.
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ba43f40..3530764 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1125,6 +1125,16 @@ static inline int queue_limit_discard_alignment(struct queue_limits *lim, sector
> & (lim->discard_granularity - 1);
> }
>
> +static inline int bdev_discard_alignment(struct block_device *bdev)
> +{
> + struct request_queue *q = bdev_get_queue(bdev);
> +
> + if (bdev != bdev->bd_contains)
> + return bdev->bd_part->discard_alignment;
> +
> + return q->limits.discard_alignment;
> +}
> +
> static inline unsigned int queue_discard_zeroes_data(struct request_queue *q)
> {
> if (q->limits.max_discard_sectors && q->limits.discard_zeroes_data == 1)
> diff --git a/block/blk-lib.c b/block/blk-lib.c
> index b2bde5c..77d8869 100644
> --- a/block/blk-lib.c
> +++ b/block/blk-lib.c
> @@ -58,7 +58,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
> /* Zero-sector (unknown) and one-sector granularities are the same. */
> granularity = max(q->limits.discard_granularity >> 9, 1U);
> mask = granularity - 1;
> - alignment = (q->limits.discard_alignment >> 9) & mask;
> + alignment = bdev_discard_alignment(bdev) >> 9;

Why are you removing AND with mask operation? I don't see any AND
operation being done in bdev_discard_alignment().

Thanks
Vivek