linux-kernel - Re: [PATCH 1/2] dm: Allow .prepare

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Message-ID: <aBFfK8mdxZ5dCW-0@redhat.com>
Date: Tue, 29 Apr 2025 19:22:19 -0400
From: Benjamin Marzinski <bmarzins@...hat.com>
To: Kevin Wolf <kwolf@...hat.com>
Cc: dm-devel@...ts.linux.dev, hreitz@...hat.com, mpatocka@...hat.com,
        snitzer@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dm: Allow .prepare_ioctl to handle ioctls directly

On Tue, Apr 29, 2025 at 06:50:17PM +0200, Kevin Wolf wrote:
> This adds a 'bool *forward' parameter to .prepare_ioctl, which allows
> device mapper targets to accept ioctls to themselves instead of the
> underlying device. If the target already fully handled the ioctl, it
> sets *forward to false and device mapper won't forward it to the
> underlying device any more.
> 
> In order for targets to actually know what the ioctl is about and how to
> handle it, pass also cmd and arg.
> 
> As long as targets restrict themselves to interpreting ioctls of type
> DM_IOCTL, this is a backwards compatible change because previously, any
> such ioctl would have been passed down through all device mapper layers
> until it reached a device that can't understand the ioctl and would
> return an error.
> 
> Signed-off-by: Kevin Wolf <kwolf@...hat.com>

Reviewed-by: Benjamin Marzinski <bmarzins@...hat.com>