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From: Miklos Szeredi <miklos@szeredi.hu>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Amir Goldstein <amir73il@gmail.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-nvdimm <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>,
	Peng Tao <tao.peng@linux.alibaba.com>
Subject: Re: [PATCH 12/20] fuse: Introduce setupmapping/removemapping commands
Date: Wed, 11 Mar 2020 16:12:15 +0100	[thread overview]
Message-ID: <CAJfpegvTo=FX5y+8R3hdkv6mOTAUQgg9qmzvL5oStddFW0OBgg@mail.gmail.com> (raw)
In-Reply-To: <20200311144124.GB83257@redhat.com>

On Wed, Mar 11, 2020 at 3:41 PM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> On Wed, Mar 11, 2020 at 03:19:18PM +0100, Miklos Szeredi wrote:
> > On Wed, Mar 11, 2020 at 8:03 AM Amir Goldstein <amir73il@gmail.com> wrote:
> > >
> > > On Tue, Mar 10, 2020 at 10:34 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> > > >
> > > > On Tue, Mar 10, 2020 at 08:49:49PM +0100, Miklos Szeredi wrote:
> > > > > On Wed, Mar 4, 2020 at 5:59 PM Vivek Goyal <vgoyal@redhat.com> wrote:
> > > > > >
> > > > > > Introduce two new fuse commands to setup/remove memory mappings. This
> > > > > > will be used to setup/tear down file mapping in dax window.
> > > > > >
> > > > > > Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> > > > > > Signed-off-by: Peng Tao <tao.peng@linux.alibaba.com>
> > > > > > ---
> > > > > >  include/uapi/linux/fuse.h | 37 +++++++++++++++++++++++++++++++++++++
> > > > > >  1 file changed, 37 insertions(+)
> > > > > >
> > > > > > diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
> > > > > > index 5b85819e045f..62633555d547 100644
> > > > > > --- a/include/uapi/linux/fuse.h
> > > > > > +++ b/include/uapi/linux/fuse.h
> > > > > > @@ -894,4 +894,41 @@ struct fuse_copy_file_range_in {
> > > > > >         uint64_t        flags;
> > > > > >  };
> > > > > >
> > > > > > +#define FUSE_SETUPMAPPING_ENTRIES 8
> > > > > > +#define FUSE_SETUPMAPPING_FLAG_WRITE (1ull << 0)
> > > > > > +struct fuse_setupmapping_in {
> > > > > > +       /* An already open handle */
> > > > > > +       uint64_t        fh;
> > > > > > +       /* Offset into the file to start the mapping */
> > > > > > +       uint64_t        foffset;
> > > > > > +       /* Length of mapping required */
> > > > > > +       uint64_t        len;
> > > > > > +       /* Flags, FUSE_SETUPMAPPING_FLAG_* */
> > > > > > +       uint64_t        flags;
> > > > > > +       /* Offset in Memory Window */
> > > > > > +       uint64_t        moffset;
> > > > > > +};
> > > > > > +
> > > > > > +struct fuse_setupmapping_out {
> > > > > > +       /* Offsets into the cache of mappings */
> > > > > > +       uint64_t        coffset[FUSE_SETUPMAPPING_ENTRIES];
> > > > > > +        /* Lengths of each mapping */
> > > > > > +        uint64_t       len[FUSE_SETUPMAPPING_ENTRIES];
> > > > > > +};
> > > > >
> > > > > fuse_setupmapping_out together with FUSE_SETUPMAPPING_ENTRIES seem to be unused.
> > > >
> > > > This looks like leftover from the old code. I will get rid of it. Thanks.
> > > >
> > >
> > > Hmm. I wonder if we should keep some out args for future extensions.
> > > Maybe return the mapped size even though it is all or nothing at this
> > > point?
> > >
> > > I have interest in a similar FUSE mapping functionality that was prototyped
> > > by Miklos and published here:
> > > https://lore.kernel.org/linux-fsdevel/CAJfpegtjEoE7H8tayLaQHG9fRSBiVuaspnmPr2oQiOZXVB1+7g@mail.gmail.com/
> > >
> > > In this prototype, a FUSE_MAP command is used by the server to map a
> > > range of file to the kernel for io. The command in args are quite similar to
> > > those in fuse_setupmapping_in, but since the server is on the same host,
> > > the mapping response is {mapfd, offset, size}.
> >
> > Right.  So the difference is in which entity allocates the mapping.
> > IOW whether the {fd, offset, size} is input or output in the protocol.
> >
> > I don't remember the reasons for going with the mapping being
> > allocated by the client, not the other way round.   Vivek?
>
> I think one of the main reasons is memory reclaim. Once all ranges in
> a cache range are allocated, we need to free a memory range which can be
> reused. And client has all the logic to free up that range so that it can
> be remapped and reused for a different file/offset. Server will not know
> any of this. So I will think that for virtiofs, server might not be
> able to decide where to map a section of file and it has to be told
> explicitly by the client.

Okay.

> >
> > If the allocation were to be by the server, we could share the request
> > type and possibly some code between the two, although the I/O
> > mechanism would still be different.
> >
>
> So input parameters of both FUSE_SETUPMAPPING and FUSE_MAP seem
> similar (except the moffset field).  Given output of FUSE_MAP reqeust
> is very different, I would think it will be easier to have it as a
> separate command.
>
> Or can it be some sort of optional output args which can differentiate
> between two types of requests.
>
> /me personally finds it simpler to have separate command instead of
> overloading FUSE_SETUPMAPPING. But its your call. :-)

I too prefer a separate request type.

Thanks,
Miklos
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  reply	other threads:[~2020-03-11 15:12 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-04 16:58 [PATCH 00/20] virtiofs: Add DAX support Vivek Goyal
2020-03-04 16:58 ` [PATCH 01/20] dax: Modify bdev_dax_pgoff() to handle NULL bdev Vivek Goyal
2020-03-04 16:58 ` [PATCH 02/20] dax: Create a range version of dax_layout_busy_page() Vivek Goyal
2020-03-10 15:19   ` Ira Weiny
2020-03-10 20:29     ` Vivek Goyal
2020-03-04 16:58 ` [PATCH 03/20] virtio: Add get_shm_region method Vivek Goyal
2020-03-10 10:53   ` Stefan Hajnoczi
2020-03-04 16:58 ` [PATCH 04/20] virtio: Implement get_shm_region for PCI transport Vivek Goyal
2020-03-10 11:04   ` Stefan Hajnoczi
2020-03-10 18:19     ` Vivek Goyal
2020-03-11 17:34       ` Stefan Hajnoczi
2020-03-11 19:29         ` Vivek Goyal
2020-03-10 11:12   ` Michael S. Tsirkin
2020-03-10 18:47     ` Vivek Goyal
2020-03-10 21:27       ` Michael S. Tsirkin
2020-03-04 16:58 ` [PATCH 05/20] virtio: Implement get_shm_region for MMIO transport Vivek Goyal
2020-03-10 11:06   ` Stefan Hajnoczi
2020-03-04 16:58 ` [PATCH 06/20] virtiofs: Provide a helper function for virtqueue initialization Vivek Goyal
2020-03-10 14:10   ` Miklos Szeredi
2020-03-04 16:58 ` [PATCH 07/20] fuse: Get rid of no_mount_options Vivek Goyal
2020-03-10 14:12   ` Miklos Szeredi
2020-03-04 16:58 ` [PATCH 08/20] fuse,virtiofs: Add a mount option to enable dax Vivek Goyal
2020-03-10 14:16   ` Miklos Szeredi
2020-03-04 16:58 ` [PATCH 09/20] virtio_fs, dax: Set up virtio_fs dax_device Vivek Goyal
2020-03-04 16:58 ` [PATCH 10/20] fuse,virtiofs: Keep a list of free dax memory ranges Vivek Goyal
2020-03-10 19:29   ` Miklos Szeredi
2020-03-04 16:58 ` [PATCH 11/20] fuse: implement FUSE_INIT map_alignment field Vivek Goyal
2020-03-10 19:31   ` Miklos Szeredi
2020-03-04 16:58 ` [PATCH 12/20] fuse: Introduce setupmapping/removemapping commands Vivek Goyal
2020-03-10 19:49   ` Miklos Szeredi
2020-03-10 20:33     ` Vivek Goyal
2020-03-11  7:03       ` Amir Goldstein
2020-03-11 14:19         ` Miklos Szeredi
2020-03-11 14:41           ` Vivek Goyal
2020-03-11 15:12             ` Miklos Szeredi [this message]
2020-03-04 16:58 ` [PATCH 13/20] fuse, dax: Implement dax read/write operations Vivek Goyal
2020-03-12  9:43   ` Miklos Szeredi
2020-03-12 16:02     ` Vivek Goyal
2020-03-13 10:18       ` Miklos Szeredi
2020-03-13 13:41         ` Vivek Goyal
2020-04-04  0:25   ` Liu Bo
2020-04-14 12:54     ` Vivek Goyal
2020-03-04 16:58 ` [PATCH 14/20] fuse,dax: add DAX mmap support Vivek Goyal
2020-03-04 16:58 ` [PATCH 15/20] fuse, dax: Take ->i_mmap_sem lock during dax page fault Vivek Goyal
2020-03-04 16:58 ` [PATCH 16/20] fuse,virtiofs: Define dax address space operations Vivek Goyal
2020-03-04 16:58 ` [PATCH 17/20] fuse,virtiofs: Maintain a list of busy elements Vivek Goyal
2020-03-04 16:58 ` [PATCH 18/20] fuse: Release file in process context Vivek Goyal
2020-03-04 16:58 ` [PATCH 19/20] fuse: Take inode lock for dax inode truncation Vivek Goyal
2020-03-04 16:58 ` [PATCH 20/20] fuse,virtiofs: Add logic to free up a memory range Vivek Goyal
2020-03-11  5:16   ` Liu Bo
2020-03-11 12:59     ` Vivek Goyal
2020-03-11 17:24       ` Liu Bo
2020-03-26  0:09   ` Liu Bo
2020-03-27 14:01     ` Vivek Goyal
2020-03-27 22:06       ` Liu Bo
2020-04-14 19:30         ` Vivek Goyal
2020-04-15 17:22           ` Liu Bo
2020-04-16 19:05             ` Vivek Goyal
2020-04-17 18:05               ` Liu Bo
2020-03-11  5:22 ` [PATCH 00/20] virtiofs: Add DAX support Amir Goldstein
2020-03-11 13:09   ` Vivek Goyal
2020-03-11 18:48   ` Vivek Goyal
2020-03-11 19:32     ` Amir Goldstein
2020-03-11 19:39       ` Vivek Goyal
2020-03-11 13:38 ` Patrick Ohly
2020-03-16 13:02   ` Vivek Goyal
2020-03-17  8:28     ` Patrick Ohly

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