Re: [PATCH v11 16/21] vfs,ext2: Remove CONFIG_EXT2_FS_XIP and rename CONFIG_FS_XIP to CONFIG_FS_DAX

[Matthew Wilcox]

On Thu, Oct 16, 2014 at 02:26:18PM +0200, Mathieu Desnoyers wrote:
> > +	bool "Direct Access support"
> > +	depends on MMU
> > +	help
> > +	  Direct Access (DAX) can be used on memory-backed block devices.
> > +	  If the block device supports DAX and the filesystem supports DAX,
> > +	  then you can avoid using the pagecache to buffer I/Os.  Turning
> > +	  on this option will compile in support for DAX; you will need to
> > +	  mount the filesystem using the -o xip option.
> 
> There is a mismatch between the documentation file (earlier patch): -o
> dax, and this config description: -o xip.

Whoops!  Good catch.

> I guess we might want to switch the mount option to "-o dax" and
> document it as such, and since it should be usable transparently for the
> same use-cases "-o xip" was enabling, we might want to keep parsing of
> "-o xip" in the code for backward compatibility.
> 
> Thoughts ?

That's exactly what we do for ext2.  For ext4, we force people to use
the new -o dax option.  We stop documenting that -o xip exist, and we
print a message to tell people to switch over to -o dax.

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