Date:   Tue, 23 Apr 2019 16:27:23 +0200
From:   Jan Kara <jack@suse.cz>
To:     Pankaj Gupta <pagupta@redhat.com>
Cc:     linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
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        xiaoguangrong.eric@gmail.com, pbonzini@redhat.com,
        yuval.shaia@oracle.com, kilobyte@angband.pl
Subject: Re: [PATCH v6 4/6]  dax: check synchronous mapping is supported
Message-ID: <20190423142723.GD9910@quack2.suse.cz>
References: <20190423080612.15361-1-pagupta@redhat.com>
 <20190423080612.15361-5-pagupta@redhat.com>
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On Tue 23-04-19 13:36:10, Pankaj Gupta wrote:
> This patch introduces 'daxdev_mapping_supported' helper
> which checks if 'MAP_SYNC' is supported with filesystem
> mapping. It also checks if corresponding dax_device is
> synchronous. Virtio pmem device is asynchronous and
> does not not support VM_SYNC. 
> 
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>

The patch looks good to me. You can add:

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

								Honza


> ---
>  include/linux/dax.h | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index c97fc0cc7167..41b4a5db6305 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -41,6 +41,18 @@ void kill_dax(struct dax_device *dax_dev);
>  void dax_write_cache(struct dax_device *dax_dev, bool wc);
>  bool dax_write_cache_enabled(struct dax_device *dax_dev);
>  bool dax_synchronous(struct dax_device *dax_dev);
> +/*
> + * Check if given mapping is supported by the file / underlying device.
> + */
> +static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
> +				struct dax_device *dax_dev)
> +{
> +	if (!(vma->vm_flags & VM_SYNC))
> +		return true;
> +	if (!IS_DAX(file_inode(vma->vm_file)))
> +		return false;
> +	return dax_synchronous(dax_dev);
> +}
>  #else
>  static inline struct dax_device *dax_get_by_host(const char *host)
>  {
> @@ -68,6 +80,11 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
>  {
>  	return false;
>  }
> +static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
> +				struct dax_device *dax_dev)
> +{
> +	return !(vma->flags & VM_SYNC);
> +}
>  #endif
>  
>  struct writeback_control;
> -- 
> 2.20.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR