Date: Sun, 18 Jun 2017 10:40:36 +0200
From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org, Jan Kara <jack@suse.cz>,
        dm-devel@redhat.com, Matthew Wilcox <mawilcox@microsoft.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org, hch@lst.de,
        Jeff Moyer <jmoyer@redhat.com>, Ingo Molnar <mingo@redhat.com>,
        "Oliver O'Halloran" <oohall@gmail.com>, viro@zeniv.linux.org.uk,
        "H. Peter Anvin" <hpa@zytor.com>, linux-fsdevel@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ross Zwisler <ross.zwisler@linux.intel.com>
Subject: Re: [PATCH v3 08/14] x86, dax, libnvdimm: move wb_cache_pmem() to
        libnvdimm
Message-ID: <20170618084036.GC26456@lst.de>
References: <149703982465.20620.14881139332926778446.stgit@dwillia2-desk3.amr.corp.intel.com> <149703986971.20620.10303247412197996310.stgit@dwillia2-desk3.amr.corp.intel.com>
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> +void clean_cache_range(void *addr, size_t size);
>  
>  static inline int
>  __copy_from_user_inatomic_nocache(void *dst, const void __user *src,
> diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
> index f42d2fd86ca3..baa80ff29da8 100644
> --- a/arch/x86/lib/usercopy_64.c
> +++ b/arch/x86/lib/usercopy_64.c
> @@ -85,7 +85,7 @@ copy_user_handle_tail(char *to, char *from, unsigned len)
>   * instruction. Note that @size is internally rounded up to be cache
>   * line size aligned.
>   */
> -static void clean_cache_range(void *addr, size_t size)
> +void clean_cache_range(void *addr, size_t size)

Can you keep clean_cache_range private please?  Just add
arch_wb_cache_pmem to usercopy_64.c just behind it so that the
compiler can tail-call and export that instead.

> --- a/drivers/nvdimm/pmem.h
> +++ b/drivers/nvdimm/pmem.h
> @@ -4,6 +4,13 @@
>  #include <linux/types.h>
>  #include <linux/pfn_t.h>
>  #include <linux/fs.h>
> +#include <asm/pmem.h>
> +
> +#ifndef CONFIG_ARCH_HAS_PMEM_API
> +static inline void arch_wb_cache_pmem(void *addr, size_t size)
> +{
> +}
> +#endif

And our normal Linux style would be to have this linux linux/pmem.h,
which should always be included for the asm version.