linux-ext4 - Re: [PATCH v2] fs/{posix_acl,ext2,jfs,ceph}: apply umask if ACL support is disabled

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Date:   Wed, 11 Oct 2023 13:00:42 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Christian Brauner <brauner@...nel.org>
Cc:     Jan Kara <jack@...e.cz>, Max Kellermann <max.kellermann@...os.com>,
        Xiubo Li <xiubli@...hat.com>,
        Ilya Dryomov <idryomov@...il.com>,
        Jeff Layton <jlayton@...nel.org>, Jan Kara <jack@...e.com>,
        Dave Kleikamp <shaggy@...nel.org>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
        jfs-discussion@...ts.sourceforge.net,
        Yang Xu <xuyang2018.jy@...itsu.com>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] fs/{posix_acl,ext2,jfs,ceph}: apply umask if ACL
 support is disabled

On Wed, Oct 11, 2023 at 05:27:37PM +0200, Christian Brauner wrote:
> Aside from that, the problem had been that filesystems like nfs v4
> intentionally raised SB_POSIXACL to prevent umask stripping in the VFS.
> IOW, for them SB_POSIXACL was equivalent to "don't apply any umask".
> 
> And afaict nfs v4 has it's own thing going on how and where umasks are
> applied. However, since we now have the following commit in vfs.misc:
> 
>     fs: add a new SB_I_NOUMASK flag

To summarize, just to make sure I understand where we're going.  Since
normally (excepting unusual cases like NFS), it's fine to strip the
umask bits twice (once in the VFS, and once in the file system, for
those file systems that are doing it), once we have SB_I_NOUMASK and
NFS starts using it, then the VFS can just unconditionally strip the
umask bits, and then we can gradually clean up the file system umask
handling (which would then be harmlessly duplicative).

Did I get this right?

					- Ted