linux-kernel - Re: [Drbd-dev] [PATCH 11/30] drbd: when receiving P

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Date:	Mon, 25 Apr 2016 09:37:28 -0700
From:	Bart Van Assche <bart.vanassche@...disk.com>
To:	Philipp Reisner <philipp.reisner@...bit.com>,
	Jens Axboe <axboe@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Lars Ellenberg <lars.ellenberg@...bit.com>,
	"drbd-dev@...ts.linbit.com" <drbd-dev@...ts.linbit.com>
Subject: Re: [Drbd-dev] [PATCH 11/30] drbd: when receiving P_TRIM, zero-out
 partial unaligned chunks

On 04/25/2016 05:13 AM, Philipp Reisner wrote:
> +	while (nr_sectors >= granularity) {
> +		nr = min_t(sector_t, nr_sectors, max_discard_sectors);
> +		err |= blkdev_issue_discard(bdev, start, nr, GFP_NOIO, 0);
> +		nr_sectors -= nr;
> +		start += nr;
> +	}

Hello Phil,

In blk_bio_discard_split() the following statement protects against 
block drivers for which max_discard_sectors is not a multiple of the 
discard granularity:

	max_discard_sectors -= max_discard_sectors % granularity;

Do we need something similar in the above loop?

To Jens: should the drbd_issue_discard_or_zero_out() function go 
upstream or should rather what this function does be integrated in 
blkdev_issue_zeroout() as is done by the patch series "[PATCH v2 0/6] 
Make blkdev_issue_discard() submit aligned discard requests" 
(http://thread.gmane.org/gmane.linux.kernel.device-mapper.devel/23801)?

Thanks,

Bart.