linux-kernel - Re: [PATCH 00/29] fs: require filesystems to explicitly opt-in to nfsd export support

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Message-ID: <aW3joQQvz2t6xkzh@infradead.org>
Date: Sun, 18 Jan 2026 23:56:17 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Dave Chinner <david@...morbit.com>
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Subject: Re: [PATCH 00/29] fs: require filesystems to explicitly opt-in to
 nfsd export support

On Fri, Jan 16, 2026 at 08:09:16AM +1100, Dave Chinner wrote:
> > I think we can be a lot more precise about the guarantee: The file
> > handle does not change for the life of the inode it represents. It
> 
> <pedantic mode engaged>
> 
> File handles most definitely change over the life of a /physical/
> inode. Unlinking a file does not require ending the life of the
> physical object that provides the persistent data store for the
> file.

> i.e. a free inode is still an -allocated, indexed inode- in the
> filesystem, and until we physically remove it from the filesystem
> the inode life cycle has not ended.

For other file systems like ext4 that have statically allocated
inodes that is even more so the case.

> IOWs, the physical (persistent) inode lifetime can span the lifetime
> of -many- files. However, the filesystem guarantees that the handle
> generated for that inode is different for each file it represents
> over the whole inode life time.
> 
> Hence I think that file handle stability/persistence needs to be
> defined in terms of -file lifetimes-, not the lifetimes of the
> filesystem objects implement the file's persistent data store.

Agreed, although I bet that is what most folks think of for the
inode - not a physical place on disk, but an object that gets
invalidated on the last close after unlink.  Either way, that rules
do need to be written down clearly.