On Thu, Nov 17, 2016 at 02:17:11PM -0800, Chaitanya Kulkarni wrote:
> From: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxxx>
>
> This adds a new block layer operation to zero out a range of
> LBAs. This allows to implement zeroing for devices that don't use
> either discard with a predictable zero pattern or WRITE SAME of zeroes.
> The prominent example of that is NVMe with the Write Zeroes command,
> but in the future this should also help with improving the way
> zeroing discards work.
>
> Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@xxxxxxxx>
I think you'll need to resend the whole series so that nvme can set
the maximum discard sectors value.
> @@ -575,9 +575,10 @@ static inline bool wbt_should_throttle(struct rq_wb *rwb, struct bio *bio)
> const int op = bio_op(bio);
>
> /*
> - * If not a WRITE (or a discard), do nothing
> + * If not a WRITE (or a discard or write zeroes), do nothing
> */
> - if (!(op == REQ_OP_WRITE || op == REQ_OP_DISCARD))
> + if (!(op == REQ_OP_WRITE || op == REQ_OP_DISCARD ||
> + op == REQ_OP_WRITE_ZEROES))
> return false;
Jens: should we really throttle for discard or write zeroes here?
Those aren't really writeback driven..
> +static inline unsigned int bdev_write_zeroes(struct block_device *bdev)
> +{
> + struct request_queue *q = bdev_get_queue(bdev);
> +
> + if (q)
> + return q->limits.max_write_zeroes_sectors;
> +
> + return 0;
If this returns a sector value I'd name it bdev_write_zeroes_sectors.
Otherwise this looks great.
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