Re: [RFC V2 12/18] famfs_fuse: Plumb the GET_FMAP message/response

[John Groves]

On 25/08/14 04:36PM, Miklos Szeredi wrote:
> On Thu, 14 Aug 2025 at 15:36, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> 
> > I'm still hoping some common ground would benefit both interfaces.
> > Just not sure what it should be.
> 
> Something very high level:
> 
>  - allow several map formats: say a plain one with a list of extents
> and a famfs one
>  - allow several types of backing files: say regular and dax dev
>  - querying maps has a common protocol, format of maps is opaque to this
>  - maps are cached by a common facility
>  - each type of mapping has a decoder module
>  - each type of backing file has a module for handling I/O
> 
> Does this make sense?
> 
> This doesn't have to be implemented in one go, but for example
> GET_FMAP could be renamed to GET_READ_MAP with an added offset and
> size parameter.  For famfs the offset/size would be set to zero/inf.
> I'd be content with that for now.

Maybe GET_FILE_MAP or GET_FILE_IOMAP if we want to keep overloading 
the term iomap. Maps are to backing-dev for regular file systems,
and to device memory (devdax) for famfs - in all cases both read
and write (when write is allowed).

Thanks,
John