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Date:   Wed, 17 Jul 2019 06:38:24 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        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>,
        =?iso-8859-1?B?Suly9G1l?= 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>,
        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
Message-ID: <20190717043824.GA4755@lst.de>
References: <20190717001446.12351-1-rcampbell@nvidia.com> <20190717001446.12351-2-rcampbell@nvidia.com> <26a47482-c736-22c4-c21b-eb5f82186363@nvidia.com> <20190717042233.GA4529@lst.de> <ae3936eb-2c08-c4a4-f670-10f25c7e0ed8@nvidia.com>
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On Tue, Jul 16, 2019 at 09:31:33PM -0700, John Hubbard wrote:
> OK, so just delete all the _zd_pad_* fields? Works for me. It's misleading to
> calling something padding, if it's actually unavailable because it's used
> in the other union, so deleting would be even better than commenting.
> 
> In that case, it would still be nice to have this new snippet, right?:

I hope willy can chime in a bit on his thoughts about how the union in
struct page should look like.  The padding at the end of the sub-structs
certainly looks pointless, and other places don't use it either.  But if
we are using the other fields it almost seems to me like we only want to
union the lru field in the first sub-struct instead of overlaying most
of it.