Re: [PATCH] ndctl: Use the same align value as original namespace on reconfigure

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Fri, 2019-10-18 at 15:55 +0530, Aneesh Kumar K.V wrote:
> Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> writes:
> 
> > "Verma, Vishal L" <vishal.l.verma@intel.com> writes:
> > 
> > > On Wed, 2019-08-07 at 10:14 +0530, Aneesh Kumar K.V wrote:
> > > > When using reconfigure command to add a `name` to the namespace we end
> > > > up updating the align attribute. Avoid this by using the value from
> > > > the original namespace. Do this only if we are keeping the namespace mode
> > > > same.
> > > > 
> > > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> > > > ---
> > > >  ndctl/namespace.c | 16 ++++++++++++++++
> > > >  1 file changed, 16 insertions(+)
> > > 
> > > Hi Aneesh,
> > > 
> > > A few comments below:
> > > 
> > > > diff --git a/ndctl/namespace.c b/ndctl/namespace.c
> > > > index 1f212a2b3a9b..24e51bb35ae1 100644
> > > > --- a/ndctl/namespace.c
> > > > +++ b/ndctl/namespace.c
> > > > @@ -596,6 +596,22 @@ static int validate_namespace_options(struct ndctl_region *region,
> > > >  			return -ENXIO;
> > > >  		}
> > > >  	} else {
> > > > +
> > > > +		/*
> > > > +		 * If we are tryint to reconfigure with the same namespace mode
> > > 
> > >                              ^trying
> > > 
> > > > +		 * Use the align details from the origin namespace. Otherwise
> > > 
> > > s/origin/original/
> > > 
> > > > +		 * pick the align details from seed namespace
> > > > +		 */
> > > > +		if (ndns && p->mode == ndctl_namespace_get_mode(ndns)) {
> > > 
> > > Do we need to depend on the mode here?
> > > 
> > > I'm thinking it should be sufficient to do:
> > >   1. Check We're in 'reconfigure'
> > >   2. Check param.align was not supplied
> > >   3. Get alignment from the pfn/dax personality, and just use that.
> > > 
> > > Does this make sense (Maybe I'm missing something).
> > 
> > We want to use the align value from the seed when we are trying
> > to reconfigure a namespace with a different mode. ie, if we are moving a
> > fsdax namespace with align value 64K to a devdax, IMHO we should pick 16M
> > as alignment for devdax.
> > 
> > > > +			struct ndctl_pfn *ns_pfn = ndctl_namespace_get_pfn(ndns);
> > > > +			struct ndctl_dax *ns_dax = ndctl_namespace_get_dax(ndns);
> > > > +			if (ns_pfn)
> > > > +				p->align = ndctl_pfn_get_align(ns_pfn);
> > > > +			else if (ns_dax)
> > > > +				p->align = ndctl_dax_get_align(ns_dax);
> > > > +			else
> > > > +				p->align = sysconf(_SC_PAGE_SIZE);
> > > 
> > > Do we need the page size fallback here - there are other checks after
> > > this point that also do a similar fallback, do they not catch the
> > > default case?
> > 
> > I did that to simplify the code with that `else if`  
> > 
> > > > +		} else
> > > >  		/*
> > > >  		 * Use the seed namespace alignment as the default if we need
> > > >  		 * one. If we don't then use PAGE_SIZE so the size_align
> 
> Any update on this.?

Yes - I've applied it to the pending branch, and it will be in v67.


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