linux-kernel - Re: [PATCH v2 1/1] statmount: accept fd as a parameter

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Message-Id: <DDOYPQ2FG2ZF.2RO4YIQ0TRKJA@gmail.com>
Date: Wed, 22 Oct 2025 21:09:42 +0530
From: "Bhavik Sachdev" <b.sachdev1904@...il.com>
To: "Christian Brauner" <brauner@...nel.org>
Cc: "Alexander Viro" <viro@...iv.linux.org.uk>,
 <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Aleksa
 Sarai" <cyphar@...har.com>, "Pavel Tikhomirov" <ptikhomirov@...tuozzo.com>,
 "Jan Kara" <jack@...e.cz>, "John Garry" <john.g.garry@...cle.com>, "Arnaldo
 Carvalho de Melo" <acme@...hat.com>, "Darrick J . Wong"
 <djwong@...nel.org>, "Namhyung Kim" <namhyung@...nel.org>, "Ingo Molnar"
 <mingo@...nel.org>, "Andrei Vagin" <avagin@...il.com>, "Alexander
 Mikhalitsyn" <alexander@...alicyn.com>
Subject: Re: [PATCH v2 1/1] statmount: accept fd as a parameter

On Tue Oct 21, 2025 at 5:41 PM IST, Christian Brauner wrote:
> Hm, do you really need a new field? You could just use the @spare
> parameter in struct mnt_id_req. It's currently validated of not being
> allowed to be non-zero in copy_mnt_id_req() which is used by both
> statmount() and listmount().
>
> I think you could just reuse it for this purpose in statmount(). And
> then maybe the flag should be STATMOUNT_BY_FD?
>
We made a new field because we thought @spare is already being used (or
will have a future use?). grab_requested_mnt_ns uses @spare as a mount
namespace fd [1], but we also only allow @spare to be 0, so I don't
really understand whats happening here, is this functionality disabled?
> Otherwise I think this could work.
>
Thanks, Christian! I will send a new patch with all your requested
changes.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7b9d14af8777ac439bbfa9ac73a12a6d85289e7e