linux-ext4 - Re: [RFC 02/10] mm/hmm: Remove dead check for HugeTLB and FS DAX

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Date: Thu, 11 Apr 2024 09:37:33 -0400
From: Peter Xu <peterx@...hat.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Alistair Popple <apopple@...dia.com>, linux-mm@...ck.org,
	david@...morbit.com, dan.j.williams@...el.com, jhubbard@...dia.com,
	rcampbell@...dia.com, willy@...radead.org,
	linux-fsdevel@...r.kernel.org, jack@...e.cz, djwong@...nel.org,
	hch@....de, david@...hat.com, ruansy.fnst@...itsu.com,
	nvdimm@...ts.linux.dev, linux-xfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, jglisse@...hat.com
Subject: Re: [RFC 02/10] mm/hmm: Remove dead check for HugeTLB and FS DAX

On Thu, Apr 11, 2024 at 09:25:30AM -0300, Jason Gunthorpe wrote:
> On Thu, Apr 11, 2024 at 10:57:23AM +1000, Alistair Popple wrote:
> > pud_huge() returns true only for a HugeTLB page. pud_devmap() is only
> > used by FS DAX pages. These two things are mutually exclusive so this
> > code is dead code and can be removed.
> 
> I'm not sure this is true.. pud_huge() is mostly a misspelling of pud_leaf()..
> 
> > -	if (pud_huge(pud) && pud_devmap(pud)) {
> 
> I suspect this should be written as:
> 
>    if (pud_leaf(pud) && pud_devmap(pud)) {
> 
> In line with Peter's work here:
> 
> https://lore.kernel.org/linux-mm/20240321220802.679544-1-peterx@redhat.com/

Just to provide more information for Alistair, this patch already switched
that over to a _leaf():

https://lore.kernel.org/r/20240318200404.448346-12-peterx@redhat.com

That's in mm-unstable now, so should see that in a rebase.

And btw it's great to see that pxx_devmap() can go away.

Thanks,

-- 
Peter Xu