Re: [PATCH] dax: try to avoid unused function warnings

[Arnd Bergmann]

On Monday, November 28, 2016 2:24:00 PM CET Ross Zwisler wrote:
> On Mon, Nov 28, 2016 at 10:12:17PM +0100, Arnd Bergmann wrote:
> > Without the get_block based I/O, we get warnings when CONFIG_FS_IOMAP
> > is disabled:
> > 
> > fs/dax.c:736:12: error: âdax_insert_mappingâ defined but not used [-Werror=unused-function]
> > fs/dax.c:512:12: error: âcopy_user_daxâ defined but not used [-Werror=unused-function]
> > fs/dax.c:490:12: error: âdax_load_holeâ defined but not used [-Werror=unused-function]
> > fs/dax.c:294:14: error: âgrab_mapping_entryâ defined but not used [-Werror=unused-function]
> > 
> > This patch blindly marks those as __maybe_unused, which avoids the warnings.
> > However, I suspect that there is actually more code in this file that should
> > not be provided without CONFIG_FS_IOMAP even though we don't get a warning
> > for it, and that we actually want a different rework, so please treat this
> > as a bug report. I have applied the patch locally in my randconfig build
> > setup to avoid seeing the warnings.
> > 
> > Fixes: 5ac65736f740 ("dax: rip out get_block based IO support")
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> 
> Thanks for the report.  I think the right way to deal with this is to just
> select FS_IOMAP when we pull in the DAX code.  I sent out a patch last week
> that does this:
> 
> https://lkml.org/lkml/2016/11/23/591

It seems we never got agreement on the approach, and we still get the
warnings above in v4.10. Should we use my patch to fix up 4.10 and get
a clean build again? It no longer applies, but I have a rebased version
that I can send.

	Arnd