Re: [PATCH v11 00/21] Add support for NV-DIMMs to ext4

From: Matthew Wilcox
Date: Tue Sep 30 2014 - 10:50:00 EST

On Tue, Sep 30, 2014 at 05:45:01AM -0400, Valdis.Kletnieks@xxxxxx wrote:
> On Thu, 25 Sep 2014 16:33:17 -0400, Matthew Wilcox said:
> > Patch 19 adds some DAX infrastructure to support ext4.
> >
> > Patch 20 adds DAX support to ext4. It is broadly similar to ext2's DAX
> > support, but it is more efficient than ext4's due to its support for
> > unwritten extents.
> I don't currently have a use case for NV-DIMM support.
> However, it would be nice if this code could be leveraged to support
> 'force O_DIRECT on all I/O to this file' - that I *do* have a use
> case for. Patch 20 looks to my untrained eye like it *almost* gets
> there.
> (And if in fact it *does* do the whole enchilada, the Changelog etc should
> mention it :)

No, it doesn't try to do that. Wouldn't you be better served with an
LD_PRELOAD that forces O_DIRECT on?

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