From: Matthew Wilcox <willy@infradead.org>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Matteo Croce <mcroce@linux.microsoft.com>,
Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>,
Grygorii Strashko <grygorii.strashko@ti.com>,
Arnd Bergmann <arnd@kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems
Date: Mon, 12 Apr 2021 02:15:32 +0100 [thread overview]
Message-ID: <20210412011532.GG2531743@casper.infradead.org> (raw)
In-Reply-To: <20210411103318.GC2531743@casper.infradead.org>
On Sun, Apr 11, 2021 at 11:33:18AM +0100, Matthew Wilcox wrote:
> Basically, we have three aligned dwords here. We can either alias with
> @flags and the first word of @lru, or the second word of @lru and @mapping,
> or @index and @private. @flags is a non-starter. If we use @mapping,
> then you have to set it to NULL before you free it, and I'm not sure
> how easy that will be for you. If that's trivial, then we could use
> the layout:
>
> unsigned long _pp_flags;
> unsigned long pp_magic;
> union {
> dma_addr_t dma_addr; /* might be one or two words */
> unsigned long _pp_align[2];
> };
> unsigned long pp_pfmemalloc;
> unsigned long xmi;
I forgot about the munmap path. That calls zap_page_range() which calls
set_page_dirty() which calls page_mapping(). If we use page->mapping,
that's going to get interpreted as an address_space pointer.
*sigh*. Foiled at every turn.
I'm kind of inclined towards using two (or more) bits for PageSlab as
we discussed here:
https://lore.kernel.org/linux-mm/01000163efe179fe-d6270c58-eaba-482f-a6bd-334667250ef7-000000@email.amazonses.com/
so we have PageKAlloc that's true for PageSlab, PagePool, PageDMAPool,
PageVMalloc, PageFrag and maybe a few other kernel-internal allocations.
(see also here:)
https://lore.kernel.org/linux-mm/20180518194519.3820-18-willy@infradead.org/
next prev parent reply other threads:[~2021-04-12 1:16 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-10 20:52 [PATCH 0/1] Fix struct page layout on 32-bit systems Matthew Wilcox (Oracle)
2021-04-10 20:52 ` [PATCH 1/1] mm: " Matthew Wilcox (Oracle)
2021-04-11 9:43 ` Jesper Dangaard Brouer
2021-04-11 10:33 ` Matthew Wilcox
2021-04-12 1:15 ` Matthew Wilcox [this message]
2021-04-14 8:10 ` Jesper Dangaard Brouer
2021-04-14 11:50 ` Matthew Wilcox
2021-04-14 11:56 ` Ilias Apalodimas
2021-04-14 15:52 ` David Laight
2021-04-14 19:13 ` Jesper Dangaard Brouer
2021-04-14 21:35 ` Matthew Wilcox
2021-04-14 21:56 ` David Laight
2021-04-15 18:08 ` Jesper Dangaard Brouer
2021-04-15 18:21 ` Matthew Wilcox
2021-04-15 21:11 ` David Laight
2021-04-15 22:22 ` Matthew Wilcox
2021-04-16 7:32 ` David Laight
2021-04-16 11:05 ` Matthew Wilcox
2021-04-16 15:27 ` Matthew Wilcox
2021-04-16 17:08 ` Jesper Dangaard Brouer
2021-04-17 3:19 ` Matthew Wilcox
2021-04-17 10:31 ` Arnd Bergmann
2021-04-17 13:56 ` Matthew Wilcox
2021-04-17 17:30 ` Arnd Bergmann
2021-04-17 10:59 ` David Laight
2021-04-19 6:34 ` Christoph Hellwig
2021-04-19 7:15 ` Ilias Apalodimas
2021-04-12 18:23 ` Matthew Wilcox
2021-04-13 8:21 ` David Laight
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