Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax, dma-to-storage, and swap

From	Andy Lutomirski <luto@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax, dma-to-storage, and swap
Date	2017-08-12 06:00 +0200
Message-ID	<udvKF-3Tr-1@gated-at.bofh.it> (permalink)
References	(1 earlier) <uaAGS-Pk-17@gated-at.bofh.it> <ub42e-3iq-9@gated-at.bofh.it> <ubyWl-5Tz-3@gated-at.bofh.it> <udfFT-2pX-9@gated-at.bofh.it> <udqBl-Ku-29@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Fri, Aug 11, 2017 at 3:26 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Fri, Aug 11, 2017 at 3:44 AM, Christoph Hellwig <hch@lst.de> wrote:
>> Please explain how this interface allows for any sort of safe userspace
>> DMA.
>
> So this is where I continue to see S_IOMAP_IMMUTABLE being able to
> support applications that MAP_SYNC does not. Dave mentioned userspace
> pNFS4 servers, but there's also Samba and other protocols that want to
> negotiate a direct path to pmem outside the kernel. Xen support has
> thus far not been able to follow in the footsteps of KVM enabling due
> to a dependence on static M2P tables that assume a static
> guest-physical to host-physical relationship [1]. Immutable files
> would allow Xen to follow the same "mmap a file" semantic as KVM.

One thing that makes me quite nervous about S_IOMAP_IMMUTABLE is the
degree to which things go badly if one program relies on it while
another program clears the flag: you risk corrupting unrelated
filesystem metadata.  I think a userspace interface to pin the extent
mapping of a file really wants a way to reliably keep it pinned (or to
reliably zap the userspace application if it gets unpinned).

Thread

[PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-04 04:40 +0200
  [PATCH v2 2/5] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP Dan Williams <dan.j.williams@intel.com> - 2017-08-04 04:40 +0200
    Re: [PATCH v2 2/5] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-04 21:50 +0200
      Re: [PATCH v2 2/5] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP Dan Williams <dan.j.williams@intel.com> - 2017-08-04 22:00 +0200
    Re: [PATCH v2 2/5] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP Dave Chinner <david@fromorbit.com> - 2017-08-05 01:40 +0200
      Re: [PATCH v2 2/5] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP Dan Williams <dan.j.williams@intel.com> - 2017-08-05 01:50 +0200
        Re: [PATCH v2 2/5] fs, xfs: introduce FALLOC_FL_SEAL_BLOCK_MAP Dave Chinner <david@fromorbit.com> - 2017-08-05 02:10 +0200
  [PATCH v2 1/5] fs, xfs: introduce S_IOMAP_IMMUTABLE Dan Williams <dan.j.williams@intel.com> - 2017-08-04 04:40 +0200
    Re: [PATCH v2 1/5] fs, xfs: introduce S_IOMAP_IMMUTABLE "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-04 22:10 +0200
      Re: [PATCH v2 1/5] fs, xfs: introduce S_IOMAP_IMMUTABLE Dan Williams <dan.j.williams@intel.com> - 2017-08-04 22:40 +0200
    Re: [PATCH v2 1/5] fs, xfs: introduce S_IOMAP_IMMUTABLE Christoph Hellwig <hch@lst.de> - 2017-08-05 11:50 +0200
      Re: [PATCH v2 1/5] fs, xfs: introduce S_IOMAP_IMMUTABLE Dave Chinner <david@fromorbit.com> - 2017-08-07 02:30 +0200
        Re: [PATCH v2 1/5] fs, xfs: introduce S_IOMAP_IMMUTABLE Christoph Hellwig <hch@lst.de> - 2017-08-11 12:40 +0200
  Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-04 04:40 +0200
    Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,         dma-to-storage, and swap Christoph Hellwig <hch@lst.de> - 2017-08-05 12:00 +0200
      Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-06 21:00 +0200
        Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,         dma-to-storage, and swap Christoph Hellwig <hch@lst.de> - 2017-08-11 12:50 +0200
          Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-12 00:30 +0200
            Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Andy Lutomirski <luto@kernel.org> - 2017-08-12 06:00 +0200
              Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-12 06:50 +0200
              Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,         dma-to-storage, and swap Christoph Hellwig <hch@lst.de> - 2017-08-12 09:40 +0200
            Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,         dma-to-storage, and swap Christoph Hellwig <hch@lst.de> - 2017-08-12 09:40 +0200
              Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-12 21:30 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,         dma-to-storage, and swap Christoph Hellwig <hch@lst.de> - 2017-08-13 11:30 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-13 22:40 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Jan Kara <jack@suse.cz> - 2017-08-14 14:50 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-14 18:20 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Jan Kara <jack@suse.cz> - 2017-08-15 10:40 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dan Williams <dan.j.williams@intel.com> - 2017-08-16 02:00 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Jan Kara <jack@suse.cz> - 2017-08-16 16:00 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Peter Zijlstra <peterz@infradead.org> - 2017-08-21 11:20 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-14 23:50 +0200
                Re: [PATCH v2 0/5] fs, xfs: block map immutable files for dax,  dma-to-storage, and swap Dave Chinner <david@fromorbit.com> - 2017-08-14 01:50 +0200
  [PATCH v2 5/5] xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in response  to fallocate Dan Williams <dan.j.williams@intel.com> - 2017-08-04 04:40 +0200
    Re: [PATCH v2 5/5] xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in  response to fallocate "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-04 22:20 +0200
      Re: [PATCH v2 5/5] xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in  response to fallocate Dan Williams <dan.j.williams@intel.com> - 2017-08-04 22:50 +0200
        Re: [PATCH v2 5/5] xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in  response to fallocate Dan Williams <dan.j.williams@intel.com> - 2017-08-04 23:00 +0200
        Re: [PATCH v2 5/5] xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in  response to fallocate "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-04 23:00 +0200
  [PATCH v2 4/5] xfs: introduce XFS_DIFLAG2_IOMAP_IMMUTABLE Dan Williams <dan.j.williams@intel.com> - 2017-08-04 04:40 +0200
    Re: [PATCH v2 4/5] xfs: introduce XFS_DIFLAG2_IOMAP_IMMUTABLE "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-04 22:40 +0200
      Re: [PATCH v2 4/5] xfs: introduce XFS_DIFLAG2_IOMAP_IMMUTABLE Dan Williams <dan.j.williams@intel.com> - 2017-08-04 22:50 +0200
      Re: [PATCH v2 4/5] xfs: introduce XFS_DIFLAG2_IOMAP_IMMUTABLE Dave Chinner <david@fromorbit.com> - 2017-08-05 01:50 +0200
        Re: [PATCH v2 4/5] xfs: introduce XFS_DIFLAG2_IOMAP_IMMUTABLE "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-08-05 02:00 +0200

csiph-web