linux-kernel - Re: [PATCH v2 2/5] dax: fix dax_mapping() definition in the FS_DAX=n + DEV

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Date:   Mon, 26 Feb 2018 10:44:28 +0100
From:   Jan Kara <jack@...e.cz>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...ts.01.org, Jan Kara <jack@...e.cz>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux-mm@...ck.org, Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org,
        kbuild test robot <fengguang.wu@...el.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 2/5] dax: fix dax_mapping() definition in the FS_DAX=n
 + DEV_DAX=y case

On Thu 22-02-18 23:17:51, Dan Williams wrote:
> An address_space will only have dax exceptional entries when FS_DAX is
> enabled. The current reliance on S_DAX causes compile failures when
> S_DAX is defined for DEV_DAX, but FS_DAX is disabled. Make dax_mapping()
> always return false so that mm/truncate.c drops its link time
> dependencies on fs/dax.c.
> 
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: linux-fsdevel@...r.kernel.org
> Cc: Christoph Hellwig <hch@....de>
> Cc: Jan Kara <jack@...e.cz>
> Cc: <stable@...r.kernel.org>
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Fixes: dee410792419 ("/dev/dax, core: file operations and dax-mmap")
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  include/linux/dax.h |    9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 0185ecdae135..62e8cf7eb566 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -107,6 +107,10 @@ int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
>  int __dax_zero_page_range(struct block_device *bdev,
>  		struct dax_device *dax_dev, sector_t sector,
>  		unsigned int offset, unsigned int length);
> +static inline bool dax_mapping(struct address_space *mapping)
> +{
> +	return mapping->host && IS_DAX(mapping->host);
> +}
>  #else
>  static inline int __dax_zero_page_range(struct block_device *bdev,
>  		struct dax_device *dax_dev, sector_t sector,
> @@ -114,12 +118,11 @@ static inline int __dax_zero_page_range(struct block_device *bdev,
>  {
>  	return -ENXIO;
>  }
> -#endif
> -
>  static inline bool dax_mapping(struct address_space *mapping)
>  {
> -	return mapping->host && IS_DAX(mapping->host);
> +	return false;
>  }
> +#endif
>  
>  struct writeback_control;
>  int dax_writeback_mapping_range(struct address_space *mapping,
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR