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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,
	linux-fsdevel@vger.kernel.org, linux-acpi@vger.kernel.org,
	qemu-devel@nongnu.org, linux-ext4@vger.kernel.org,
	linux-xfs@vger.kernel.org, dan.j.williams@intel.com,
	zwisler@kernel.org, vishal.l.verma@intel.com,
	dave.jiang@intel.com, mst@redhat.com, jasowang@redhat.com,
	willy@infradead.org, rjw@rjwysocki.net, hch@infradead.org,
	lenb@kernel.org, jack@suse.cz, tytso@mit.edu,
	adilger.kernel@dilger.ca, darrick.wong@oracle.com,
	lcapitulino@redhat.com, kwolf@redhat.com, imammedo@redhat.com,
	jmoyer@redhat.com, nilal@redhat.com, riel@surriel.com,
	stefanha@redhat.com, aarcange@redhat.com, david@redhat.com,
	david@fromorbit.com, cohuck@redhat.com,
	xiaoguangrong.eric@gmail.com, pbonzini@redhat.com,
	kilobyte@angband.pl, yuval.shaia@oracle.com
Subject: Re: [PATCH v5 4/6] dax: check synchronous mapping is supported
Date: Wed, 10 Apr 2019 10:25:04 +0200	[thread overview]
Message-ID: <20190410082504.GF1426@quack2.suse.cz> (raw)
In-Reply-To: <20190410040826.24371-5-pagupta@redhat.com>

On Wed 10-04-19 09:38:24, 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>
> ---
>  include/linux/dax.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index b896706a5ee9..4a2a60ffec86 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -38,6 +38,24 @@ 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);
> +
> +/*
> + * Callers check if synchronous mapping is enabled for DAX file
> + * and attached dax device is also synchronous.
> + *
> + * dax_synchronous function verifies if dax device is synchronous.
> + * Currently, only virtio pmem device supports asynchronous device
> + * flush.
> + */

Thanks for the patch! I'd restructure this comment like:

/*
 * 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)
> +{

	/* Everyone supports non-sync mappings */
> +	if (!(vma->vm_flags & VM_SYNC))
> +		return true;
	/* Sync mappings are supported only for files using DAX */
> +	if (!IS_DAX(file_inode(vma->vm_file)))
> +		return false;
	/* Underlying device must support persisting through CPU instructions */
> +	return dax_synchronous(dax_dev);
> +}
>  #else
>  static inline struct dax_device *dax_get_by_host(const char *host)
>  {
> @@ -69,6 +87,11 @@ static inline bool dax_synchronous(struct dax_device *dax_dev)
>  {
>  	return true;
>  }
> +static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
> +				struct dax_device *dax_dev)
> +{
> +	return true;

This looks wrong. Shouldn't it rather be:

	return !(vma->flags & VM_SYNC);

?

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2019-04-10  8:25 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-10  4:08 [PATCH v5 0/6] virtio pmem driver Pankaj Gupta
2019-04-10  4:08 ` [PATCH v5 1/6] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-04-11 14:51   ` Dan Williams
2019-04-11 15:57     ` [Qemu-devel] " Pankaj Gupta
2019-04-11 16:09       ` Dan Williams
2019-04-11 16:23         ` Pankaj Gupta
2019-04-12  8:32     ` Jan Kara
2019-04-12 13:12       ` Jeff Moyer
2019-04-18  6:27         ` [Qemu-devel] " Pankaj Gupta
2019-04-18 16:05         ` Dan Williams
2019-04-18 16:10           ` Jeff Moyer
2019-04-18 16:18           ` Christoph Hellwig
2019-04-18 18:14             ` Dan Williams
2019-04-22 15:51               ` Jeff Moyer
2019-04-22 19:44                 ` Dan Williams
2019-04-22 21:03                   ` Jeff Moyer
2019-04-23  4:07                     ` Pankaj Gupta
2019-04-10  4:08 ` [PATCH v5 2/5] virtio-pmem: Add virtio pmem driver Pankaj Gupta
2019-04-10 12:24   ` Cornelia Huck
2019-04-10 14:38     ` Yuval Shaia
2019-04-10 15:44       ` Pankaj Gupta
2019-04-10 15:38     ` Pankaj Gupta
2019-04-10 13:12   ` Michael S. Tsirkin
2019-04-10 14:03     ` [Qemu-devel] " Pankaj Gupta
2019-04-10 14:31       ` Cornelia Huck
2019-04-10 16:46         ` Michael S. Tsirkin
2019-04-10 16:52           ` Cornelia Huck
2019-04-10 14:41   ` Yuval Shaia
2019-04-10  4:08 ` [PATCH v5 3/6] libnvdimm: add dax_dev sync flag Pankaj Gupta
2019-04-10  8:28   ` Jan Kara
2019-04-10  8:38     ` Pankaj Gupta
2019-04-11 14:56   ` Dan Williams
2019-04-11 15:39     ` Pankaj Gupta
2019-04-10  4:08 ` [PATCH v5 4/6] dax: check synchronous mapping is supported Pankaj Gupta
2019-04-10  8:25   ` Jan Kara [this message]
2019-04-10  8:31     ` Pankaj Gupta
2019-04-10  4:08 ` [PATCH v5 5/6] ext4: disable map_sync for async flush Pankaj Gupta
2019-04-10  4:08 ` [PATCH v5 6/6] xfs: " Pankaj Gupta

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