Re: [PATCH v2] btrfs: zstd ensure reclaim timer is properly cleaned up

[David Sterba <dsterba@suse.cz>]

On Wed, Feb 27, 2019 at 01:29:16PM -0500, Dennis Zhou wrote:
> > I've noticed while reading the code, why do you use the indirect call
> > here? The wsm.ops points to btrfs_zstd_compress so free_workspace is
> > always zstd_free_workspace.
> > 
> > The compiler is usually smart to replace such things by direct call if
> > the type has not escaped, but this is not true for btrfs_compress_op so
> > the indirect function call must be preserved.
> 
> I don't have a strong reason to use the indirect call here. It was just
> to make it consistent for everyone to use the indirection. This at least
> is in the cleanup path, so I don't think performance is that important?

It's not just that, the timer uses it too and there are indirect calls
of the alloc_workspace callback. The indirection is not used by lzo nor
zlib code, so I don't see what 'everyone' you mean. In the generic
compression code it makes sense, I see that.

> But I don't feel strongly for or against calling zstd_free_workspace()
> directly.

I feel strongly about not using the indirection when not necessary :)