linux-kernel - Re: [PATCH v6 6/6] xfs: disable map

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Message-ID: <20190423220217.GA29573@dread.disaster.area>
Date:   Wed, 24 Apr 2019 08:02:17 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Pankaj Gupta <pagupta@...hat.com>
Cc:     linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-acpi@...r.kernel.org,
        qemu-devel@...gnu.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, dan.j.williams@...el.com,
        zwisler@...nel.org, vishal.l.verma@...el.com, dave.jiang@...el.com,
        mst@...hat.com, jasowang@...hat.com, willy@...radead.org,
        rjw@...ysocki.net, hch@...radead.org, lenb@...nel.org,
        jack@...e.cz, tytso@....edu, adilger.kernel@...ger.ca,
        darrick.wong@...cle.com, lcapitulino@...hat.com, kwolf@...hat.com,
        imammedo@...hat.com, jmoyer@...hat.com, nilal@...hat.com,
        riel@...riel.com, stefanha@...hat.com, aarcange@...hat.com,
        david@...hat.com, cohuck@...hat.com, xiaoguangrong.eric@...il.com,
        pbonzini@...hat.com, yuval.shaia@...cle.com, kilobyte@...band.pl
Subject: Re: [PATCH v6 6/6] xfs: disable map_sync for async flush

On Tue, Apr 23, 2019 at 01:36:12PM +0530, Pankaj Gupta wrote:
> Dont support 'MAP_SYNC' with non-DAX files and DAX files
> with asynchronous dax_device. Virtio pmem provides
> asynchronous host page cache flush mechanism. We don't
> support 'MAP_SYNC' with virtio pmem and xfs.
> 
> Signed-off-by: Pankaj Gupta <pagupta@...hat.com>
> ---
>  fs/xfs/xfs_file.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 1f2e2845eb76..0e59be018511 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1196,11 +1196,13 @@ xfs_file_mmap(
>  	struct file	*filp,
>  	struct vm_area_struct *vma)
>  {
> -	/*
> -	 * We don't support synchronous mappings for non-DAX files. At least
> -	 * until someone comes with a sensible use case.
> +	struct dax_device *dax_dev = xfs_find_daxdev_for_inode
> +						(file_inode(filp));
> +
> +	/* We don't support synchronous mappings for non-DAX files and
> +	 * for DAX files if underneath dax_device is not synchronous.
>  	 */

	/*
	 * This is the correct multi-line comment format. Please
	 * update the patch to maintain the existing comment format.
	 */

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com