linux-kernel - Re: [PATCH 5/5] brd: zero data for discard that is not aligned to page

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Message-ID: <aAXXS1Xq5g2yLTTM@infradead.org>
Date: Sun, 20 Apr 2025 22:27:39 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: axboe@...nel.dk, kbusch@...nel.org, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, yukuai3@...wei.com,
	yi.zhang@...wei.com, yangerkun@...wei.com, johnny.chenyi@...wei.com
Subject: Re: [PATCH 5/5] brd: zero data for discard that is not aligned to
 page

On Fri, Apr 18, 2025 at 05:38:26PM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> Currently brd_do_discard() will just skip unaligned sectors, and in this
> case user will still get old data after discard. Fix this by writing
> zero data to unaligned sectors.

Which is perfectly fine with discard semantics and that of the
underlying primitives in storage standards.  If you need guaranteed
zeroing you need to implement the write zeroes operation.