Re: [Cluster-devel] [PATCH][try6] VFS: new want_holesize and got_holesize buffer_head flags for fiemap

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
> This looks like a big indicator that get_blocks is the wrong
> interface for fiemap.

Hi Christoph,

Yes, I thought about that.
One of my early prototypes had a separate function used by fiemap.
Function __generic_block_fiemap would call get_block() which
returned an indication of a hole as it does today. When it saw
the hole, fiemap called a new function get_hole_size() that was
passed in like get_block. The problem is: it's grossly inefficient,
since the new function get_hole_size() has to redo most of the work
that get_block just did (at least in the case of GFS2). (Which in the
case of a 1PB sparse file is non-trivial, since it involves several
levels of metadata indirection). Combining it with get_block made it
much more efficient.

Making a separate get_block_map_fiemap() function just seems like an
exercise in redundancy.

Regards,

Bob Peterson
Red Hat File Systems