linux-kernel - Re: [PATCH v2 02/31] exportfs: add new EXPORT_OP_STABLE

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Message-ID: <aW8ztQ-RbhxwzMk7@infradead.org>
Date: Mon, 19 Jan 2026 23:50:13 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Jeff Layton <jlayton@...nel.org>
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Subject: Re: [PATCH v2 02/31] exportfs: add new EXPORT_OP_STABLE_HANDLES flag

On Mon, Jan 19, 2026 at 11:26:19AM -0500, Jeff Layton wrote:
> +  EXPORT_OP_STABLE_HANDLES - This filesystem provides filehandles that are
> +    stable across the lifetime of a file. This is a hard requirement for export
> +    via nfsd. Any filesystem that is eligible to be exported via nfsd must
> +    indicate this guarantee by setting this flag. Most disk-based filesystems
> +    can do this naturally. Pseudofilesystems that are for local reporting and
> +    control (e.g. kernfs, pidfs, nsfs) usually can't support this.

Suggested rewording, taking some of the ideas from Dave Chinners earlier
comments into account:

  EXPORT_OP_STABLE_HANDLES - This filesystem provides filehandles that are
    stable across the lifetime of a file.  A file in this context is an
    instantiated inode reachable by one or more file names, or still open after
    the last name has been unlinked.  Reuses of the same on-disk inode structure
    are considered new files and must provide different file handles from the
    previous incarnation.  Most file systems designed to store user data
    naturally provide this capability.  Pseudofilesystems that are for local
    reporting and control (e.g. kernfs, pidfs, nsfs) usually can't support this.

    This flags is a hard requirement for export via nfsd. Any filesystem that
    is eligible to be exported via nfsd must indicate this guarantee by
    setting this flag.