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Date:   Sun, 20 Sep 2020 22:25:50 -0400
From:   Stuart Little <achirvasub@gmail.com>
To:     Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>, linux-nvdimm@lists.01.org
Cc:     kernel list <linux-kernel@vger.kernel.org>
Subject: Re: PROBLEM: 5.9.0-rc6 fails =?utf-8?Q?to_?=
 =?utf-8?Q?compile_due_to_'redefinition_of_=E2=80=98dax=5Fsupported?=
 =?utf-8?B?4oCZJw==?=
Message-ID: <20200921022550.GE3027080@arch-chirva.localdomain>
References: <20200921010359.GO3027113@arch-chirva.localdomain>
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An update on this: I've done a bisect, with the following result.

--- cut here ---

e2ec5128254518cae320d5dc631b71b94160f663 is the first bad commit
commit e2ec5128254518cae320d5dc631b71b94160f663
Author: Jan Kara <jack@suse.cz>
Date:   Sun Sep 20 08:54:42 2020 -0700

    dm: Call proper helper to determine dax support
    
    DM was calling generic_fsdax_supported() to determine whether a device
    referenced in the DM table supports DAX. However this is a helper for "leaf" device drivers so that
    they don't have to duplicate common generic checks. High level code
    should call dax_supported() helper which that calls into appropriate
    helper for the particular device. This problem manifested itself as
    kernel messages:
    
    dm-3: error: dax access failed (-95)
    
    when lvm2-testsuite run in cases where a DM device was stacked on top of
    another DM device.
    
    Fixes: 7bf7eac8d648 ("dax: Arrange for dax_supported check to span multiple devices")
    Cc: <stable@vger.kernel.org>
    Tested-by: Adrian Huang <ahuang12@lenovo.com>
    Signed-off-by: Jan Kara <jack@suse.cz>
    Acked-by: Mike Snitzer <snitzer@redhat.com>
    Reported-by: kernel test robot <lkp@intel.com>
    Link: https://lore.kernel.org/r/160061715195.13131.5503173247632041975.stgit@dwillia2-desk3.amr.corp.intel.com
    Signed-off-by: Dan Williams <dan.j.williams@intel.com>

 drivers/dax/super.c   |  4 ++++
 drivers/md/dm-table.c | 10 +++++++---
 include/linux/dax.h   | 22 ++++++++++++++++++++--
 3 files changed, 31 insertions(+), 5 deletions(-)

--- end ---

On Sun, Sep 20, 2020 at 09:03:59PM -0400, Stuart Little wrote:
> I am trying to compile for an x86_64 machine (Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz). The config file I am currently using is at
> 
> https://termbin.com/xin7
> 
> The build for 5.9.0-rc6 fails with the following errors:
> 
> --- cut here ---
> 
> drivers/dax/super.c:325:6: error: redefinition of ‘dax_supported’
>   325 | bool dax_supported(struct dax_device *dax_dev, struct block_device *bdev,
>       |      ^~~~~~~~~~~~~
> In file included from drivers/dax/super.c:16:
> ./include/linux/dax.h:162:20: note: previous definition of ‘dax_supported’ was here
>   162 | static inline bool dax_supported(struct dax_device *dax_dev,
>       |                    ^~~~~~~~~~~~~
>   CC      lib/memregion.o
>   CC [M]  drivers/gpu/drm/drm_gem_vram_helper.o
> make[2]: *** [scripts/Makefile.build:283: drivers/dax/super.o] Error 1
> make[1]: *** [scripts/Makefile.build:500: drivers/dax] Error 2
> make[1]: *** Waiting for unfinished jobs....
> 
> --- end ---
> 
> That's earlier on, and then later, at the end of the (failed) build:
> 
> make: *** [Makefile:1784: drivers] Error 2
> 
> The full build log is at
> 
> https://termbin.com/ihxj
> 
> but I do not see anything else amiss. 5.9.0-rc5 built fine last week.