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    SubjectRe: [RFC PATCH V2 01/12] fs/stat: Define DAX statx attribute
    On Thu, Jan 16, 2020 at 09:55:02AM -0800, Ira Weiny wrote:
    > On Wed, Jan 15, 2020 at 09:39:35PM -0800, Darrick J. Wong wrote:
    > > On Wed, Jan 15, 2020 at 02:38:21PM -0800, Ira Weiny wrote:
    > > > On Wed, Jan 15, 2020 at 12:10:50PM -0800, Dan Williams wrote:
    > > > > On Wed, Jan 15, 2020 at 11:45 AM Ira Weiny <ira.weiny@intel.com> wrote:
    > > > > >
    > > > > > On Wed, Jan 15, 2020 at 09:38:34AM -0800, Darrick J. Wong wrote:
    > > > > > > On Wed, Jan 15, 2020 at 12:37:15PM +0100, Jan Kara wrote:
    > > > > > > > On Fri 10-01-20 11:29:31, ira.weiny@intel.com wrote:
    > > > > > > > > From: Ira Weiny <ira.weiny@intel.com>
    > > > > > > > >
    > > >
    >
    > [snip]
    >
    > > >
    > > > Sure, but for now I think referencing mmap for details on MAP_SYNC works.
    > > >
    > > > I suspect that we may have some word smithing once I get this series in and we
    > > > submit a change to the statx man page itself. Can I move forward with the
    > > > following for this patch?
    > > >
    > > > <quote>
    > > > STATX_ATTR_DAX
    > > >
    > > > The file is in the DAX (cpu direct access) state. DAX state
    > >
    > > Hmm, now that I see it written out, I <cough> kind of like "DAX mode"
    > > better now. :/
    > >
    > > "The file is in DAX (CPU direct access) mode. DAX mode attempts..."
    >
    > Sure... now you tell me... ;-)
    >
    > Seriously, we could use mode here in the man page as this is less confusing to
    > say "DAX mode".
    >
    > But I think the code should still use 'state' because mode is just too
    > overloaded. You were not the only one who was thrown by my use of mode and I
    > don't want that confusion when we look at this code 2 weeks from now...
    >
    > https://www.reddit.com/r/ProgrammerHumor/comments/852og2/only_god_knows/
    >
    > ;-)

    Ok, let's leave it alone for now then.

    I'm not even sure what 'DAX' stands for. Direct Access to ...
    Professor Xavier? 8-)

    > >
    > > > attempts to minimize software cache effects for both I/O and
    > > > memory mappings of this file. It requires a file system which
    > > > has been configured to support DAX.
    > > >
    > > > DAX generally assumes all accesses are via cpu load / store
    > > > instructions which can minimize overhead for small accesses, but
    > > > may adversely affect cpu utilization for large transfers.
    > > >
    > > > File I/O is done directly to/from user-space buffers and memory
    > > > mapped I/O may be performed with direct memory mappings that
    > > > bypass kernel page cache.
    > > >
    > > > While the DAX property tends to result in data being transferred
    > > > synchronously, it does not give the same guarantees of
    > > > synchronous I/O where data and the necessary metadata are
    > > > transferred together.
    > >
    > > (I'm frankly not sure that synchronous I/O actually guarantees that the
    > > metadata has hit stable storage...)
    >
    > I'll let you and Dan work this one out... ;-)

    Hehe. I think the wording here is fine.

    --D

    > Ira
    >

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