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>,
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: Wed, 14 Apr 2021 22:35:56 +0100 [thread overview]
Message-ID: <20210414213556.GY2531743@casper.infradead.org> (raw)
In-Reply-To: <20210414211322.3799afd4@carbon>
On Wed, Apr 14, 2021 at 09:13:22PM +0200, Jesper Dangaard Brouer wrote:
> (If others want to reproduce). First I could not reproduce on ARM32.
> Then I found out that enabling CONFIG_XEN on ARCH=arm was needed to
> cause the issue by enabling CONFIG_ARCH_DMA_ADDR_T_64BIT.
hmmm ... you should be able to provoke it by enabling ARM_LPAE,
which selects PHYS_ADDR_T_64BIT, and
config ARCH_DMA_ADDR_T_64BIT
def_bool 64BIT || PHYS_ADDR_T_64BIT
> struct page {
> long unsigned int flags; /* 0 4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> union {
> struct {
> struct list_head lru; /* 8 8 */
> struct address_space * mapping; /* 16 4 */
> long unsigned int index; /* 20 4 */
> long unsigned int private; /* 24 4 */
> }; /* 8 20 */
> struct {
> dma_addr_t dma_addr; /* 8 8 */
> }; /* 8 8 */
[...]
> } __attribute__((__aligned__(8))); /* 8 24 */
> union {
> atomic_t _mapcount; /* 32 4 */
> unsigned int page_type; /* 32 4 */
> unsigned int active; /* 32 4 */
> int units; /* 32 4 */
> }; /* 32 4 */
> atomic_t _refcount; /* 36 4 */
>
> /* size: 40, cachelines: 1, members: 4 */
> /* sum members: 36, holes: 1, sum holes: 4 */
> /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
> /* last cacheline: 40 bytes */
> } __attribute__((__aligned__(8)));
If you also enable CONFIG_MEMCG or enough options to make
LAST_CPUPID_NOT_IN_PAGE_FLAGS true, you'll end up with another 4-byte
hole at the end.
next prev parent reply other threads:[~2021-04-14 21:36 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
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 [this message]
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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