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Message-ID: <2807E5FD2F6FDA4886F6618EAC48510E79E2E610@CRSMSX101.amr.corp.intel.com>
Date: Tue, 23 Jul 2019 21:39:17 +0000
From: "Weiny, Ira" <ira.weiny@...el.com>
To: Ralph Campbell <rcampbell@...dia.com>,
Matthew Wilcox <willy@...radead.org>
CC: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
John Hubbard <jhubbard@...dia.com>,
"Vlastimil Babka" <vbabka@...e.cz>,
Christoph Lameter <cl@...ux.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Jérôme Glisse <jglisse@...hat.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Pekka Enberg <penberg@...nel.org>,
Randy Dunlap <rdunlap@...radead.org>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Christoph Hellwig <hch@....de>,
Jason Gunthorpe <jgg@...lanox.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: RE: [PATCH v2 1/3] mm: document zone device struct page field usage
>
> On 7/22/19 4:08 AM, Matthew Wilcox wrote:
> > On Sun, Jul 21, 2019 at 10:13:45PM -0700, Ira Weiny wrote:
> >> On Sun, Jul 21, 2019 at 09:02:04AM -0700, Matthew Wilcox wrote:
> >>> On Fri, Jul 19, 2019 at 12:29:53PM -0700, Ralph Campbell wrote:
> >>>> Struct page for ZONE_DEVICE private pages uses the page->mapping
> >>>> and and page->index fields while the source anonymous pages are
> >>>> migrated to device private memory. This is so rmap_walk() can find
> >>>> the page when migrating the ZONE_DEVICE private page back to system
> memory.
> >>>> ZONE_DEVICE pmem backed fsdax pages also use the page->mapping
> and
> >>>> page->index fields when files are mapped into a process address space.
> >>>>
> >>>> Restructure struct page and add comments to make this more clear.
> >>>
> >>> NAK. I just got rid of this kind of foolishness from struct page,
> >>> and you're making it harder to understand, not easier. The comments
> >>> could be improved, but don't lay it out like this again.
> >>
> >> Was V1 of Ralphs patch ok? It seemed ok to me.
> >
> > Yes, v1 was fine. This seems like a regression.
> >
>
> This is about what people find "easiest to understand" and so I'm not
> surprised that opinions differ.
> What if I post a v3 based on v1 but remove the _zd_pad_* variables that
> Christoph found misleading and add some more comments about how the
> different ZONE_DEVICE types use the 3 remaining words (basically the
> comment from v2)?
I'm ok with that...
Ira
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