Re: [PATCH 1/3] ext4: return the extent cache information via fiemap

["Theodore Y. Ts'o" <tytso@mit.edu>]

On Sat, Aug 10, 2019 at 12:33:43AM -0700, Christoph Hellwig wrote:
> 
> On Fri, Aug 09, 2019 at 02:18:29PM -0400, Theodore Ts'o wrote:
> > For debugging reasons, it's useful to know the contents of the extent
> > cache.  Since the extent cache contains much of what is in the fiemap
> > ioctl, extend the fiemap interface to return this information via some
> > ext4-specific flags.
> 
> Nak.  No weird fs specific fiemap flags that aren't even in the uapi
> header.  Please provide your own debug only interface.

I can understand why you don't like this from the principle of the
thing.

I'll create my own ioctl, and make a copy of ioctl_fiemap() into ext4
and modify it for my needs.  I was trying to avoid needing to do that,
since there is plenty of space in the fiemap flags to carve out space
for file-specific specific flags, and avoiding making extra copies of
code for the purposes of reuse weighed more heavily than "no
fs-specific fiemap flags".

						- Ted