Re: [RFC PATCH 02/17] vfs: Implement a FIEMAP callback

Christoph Hellwig
2026-03-04T14:06:55Z

On Wed, Mar 04, 2026 at 02:03:09PM +0000, David Howells wrote:
> Implement a callback in the internal kernel FIEMAP API so that kernel users
> can make use of it as the filler function expects to write to userspace.
> This allows the FIEMAP data to be captured and parsed. This is useful for
> cachefiles and also potentially for knfsd and ksmbd to implement their
> equivalents of FIEMAP remotely rather than using SEEK_DATA/SEEK_HOLE.

Hell no. FIEMAP is purely a debugging toool and must not get anywhere
near a data path. NAK to all of this.