From: Christoph Hellwig <hch@lst.de>
To: John Hubbard <jhubbard@nvidia.com>
Cc: "Ralph Campbell" <rcampbell@nvidia.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
willy@infradead.org, "Vlastimil Babka" <vbabka@suse.cz>,
"Christoph Lameter" <cl@linux.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
"Lai Jiangshan" <jiangshanlai@gmail.com>,
"Martin Schwidefsky" <schwidefsky@de.ibm.com>,
"Pekka Enberg" <penberg@kernel.org>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Andrey Ryabinin" <aryabinin@virtuozzo.com>,
"Christoph Hellwig" <hch@lst.de>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>
Subject: Re: [PATCH 1/3] mm: document zone device struct page reserved fields
Date: Wed, 17 Jul 2019 06:22:33 +0200 [thread overview]
Message-ID: <20190717042233.GA4529@lst.de> (raw)
In-Reply-To: <26a47482-c736-22c4-c21b-eb5f82186363@nvidia.com>
On Tue, Jul 16, 2019 at 06:20:23PM -0700, John Hubbard wrote:
> > - unsigned long _zd_pad_1; /* uses mapping */
> > + /*
> > + * The following fields are used to hold the source
> > + * page anonymous mapping information while it is
> > + * migrated to device memory. See migrate_page().
> > + */
> > + unsigned long _zd_pad_1; /* aliases mapping */
> > + unsigned long _zd_pad_2; /* aliases index */
> > + unsigned long _zd_pad_3; /* aliases private */
>
> Actually, I do think this helps. It's hard to document these fields, and
> the ZONE_DEVICE pages have a really complicated situation during migration
> to a device.
>
> Additionally, I'm not sure, but should we go even further, and do this on the
> other side of the alias:
The _zd_pad_* field obviously are NOT used anywhere in the source tree.
So these comments are very misleading. If we still keep
using ->mapping, ->index and ->private we really should clean up the
definition of struct page to make that obvious instead of trying to
doctor around it using comments.
next prev parent reply other threads:[~2019-07-17 4:22 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 0:14 [PATCH 0/3] mm/hmm: fixes for device private page migration Ralph Campbell
2019-07-17 0:14 ` [PATCH 1/3] mm: document zone device struct page reserved fields Ralph Campbell
2019-07-17 1:20 ` John Hubbard
2019-07-17 4:22 ` Christoph Hellwig [this message]
2019-07-17 4:31 ` John Hubbard
2019-07-17 4:38 ` Christoph Hellwig
2019-07-17 17:50 ` Ralph Campbell
2019-07-17 0:14 ` [PATCH 2/3] mm/hmm: fix ZONE_DEVICE anon page mapping reuse Ralph Campbell
2019-07-17 1:40 ` John Hubbard
2019-07-17 0:14 ` [PATCH 3/3] mm/hmm: Fix bad subpage pointer in try_to_unmap_one Ralph Campbell
2019-07-17 1:51 ` John Hubbard
2019-07-17 15:14 ` Sasha Levin
2019-07-19 19:06 [PATCH 0/3] mm/hmm: fixes for device private page migration Ralph Campbell
2019-07-19 19:06 ` [PATCH 1/3] mm: document zone device struct page reserved fields Ralph Campbell
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