linux-kernel - Re: [PATCH v4 00/10] man2: document "new" mount API

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Message-ID: <2025-09-21-eldest-expert-wrists-cuddle-CQWTLx@cyphar.com>
Date: Sun, 21 Sep 2025 19:58:12 +1000
From: Aleksa Sarai <cyphar@...har.com>
To: Askar Safin <safinaskar@...il.com>
Cc: alx@...nel.org, brauner@...nel.org, dhowells@...hat.com, 
	g.branden.robinson@...il.com, jack@...e.cz, linux-api@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-man@...r.kernel.org, 
	mtk.manpages@...il.com, safinaskar@...omail.com, viro@...iv.linux.org.uk
Subject: Re: [PATCH v4 00/10] man2: document "new" mount API

On 2025-09-21, Askar Safin <safinaskar@...il.com> wrote:
> Aleksa, thank you! Don't give up. We all need these manpages.
> 
> I see you didn't address some my previous notes.
> 
> * move_mount(2) still says "Mount objects cannot be attached beneath the filesystem root".
> I suggest saying "root directory" or "root" or "root directory of the process" or just "/"
> instead. But you may keep this phrase as is, of course.
> 
> * Docs for FSPICK_NO_AUTOMOUNT in fspick(2) are still wrong. They say that FSPICK_NO_AUTOMOUNT
> affects all components of path. Similar thing applies to mount_setattr(2) and move_mount(2)

Sorry, I last read through your review comments a month ago, I must've
forgotten to make these changes back then. I'll include them in v5.
(It seems I remembered to change the open_tree(2) automount one but
forgot to do it for the others, oops!)

> * open_tree(2) still says:
> > If flags does not contain OPEN_TREE_CLONE, open_tree() returns a file descriptor
> > that is exactly equivalent to one produced by openat(2) when called with the same dirfd and path.
> 
> This is not true if automounts are involved. I suggest adding "modulo automounts". But you may
> keep everything, of course.

Hmmm. As we discussed last time, this sentence is more intended to
indicate that the file descriptor is just a regular open file (with no
dissolve_on_fput() + FMODE_NEED_UNMOUNT magic) rather than the exact
behaviour you get with regards to path lookup.

I would honestly prefer to remove "when called with the same dirfd and
path" rather than add caveats, but I think it makes the sentence less
readable... I'll think about it and try to fix this wording up somehow
for v5.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/

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