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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Tue, 10 Mar 2020 20:31:44 +0100
Message-ID: <CAJfpegu5HMg2BnBsfSEWOv7K_0KjchntZ9q4oOvxzYLjOEBF3g@mail.gmail.com>
Subject: Re: [PATCH 11/20] fuse: implement FUSE_INIT map_alignment field
To:     Vivek Goyal <vgoyal@redhat.com>
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-nvdimm@lists.01.org, virtio-fs@redhat.com,
        Stefan Hajnoczi <stefanha@redhat.com>,
        "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
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On Wed, Mar 4, 2020 at 5:59 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> The device communicates FUSE_SETUPMAPPING/FUSE_REMOVMAPPING alignment
> constraints via the FUST_INIT map_alignment field.  Parse this field and
> ensure our DAX mappings meet the alignment constraints.
>
> We don't actually align anything differently since our mappings are
> already 2MB aligned.  Just check the value when the connection is
> established.  If it becomes necessary to honor arbitrary alignments in
> the future we'll have to adjust how mappings are sized.
>
> The upshot of this commit is that we can be confident that mappings will
> work even when emulating x86 on Power and similar combinations where the
> host page sizes are different.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>