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Date:   Tue, 13 Jul 2021 13:32:42 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Christian Brauner <brauner@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>, Chris Mason <clm@fb.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 01/24] namei: handle mappings in lookup_one_len()
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References: <20210713111344.1149376-1-brauner@kernel.org>
 <20210713111344.1149376-2-brauner@kernel.org>
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On Tue, Jul 13, 2021 at 01:13:21PM +0200, Christian Brauner wrote:
> From: Christian Brauner <christian.brauner@ubuntu.com>
> 
> Various filesystems use the lookup_one_len() helper to lookup a single path
> component relative to a well-known starting point. Allow such filesystems to
> support idmapped mounts by enabling lookup_one_len() to take the idmap into
> account when calling inode_permission(). This change is a required to let btrfs
> (and other filesystems) support idmapped mounts.

NAK.  Expose a new variant if you must, but leave the old one alone.