linux-ext4 - Re: [PATCH] ext4: issue aligned discards

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Message-ID: <20200608073524.GA1480@infradead.org>
Date:   Mon, 8 Jun 2020 00:35:24 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Harshad Shirwadkar <harshadshirwadkar@...il.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: issue aligned discards

On Fri, Jun 05, 2020 at 03:28:19PM -0700, Harshad Shirwadkar wrote:
> Ext4 before this patch can issue discards without respecting block
> device's discard alignment. Such a discard results in EIO and
> kernel logs.

No, that is not how discard works.  The granularity is a hint and
blk_bio_discard_split already does all the work to align to it.  If
you have a make_request based driver that doesn't do that you need
to fix that driver instead.