From: Matthew Wilcox <willy@infradead.org>
To: David Laight <David.Laight@aculab.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-mips@vger.kernel.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: Fri, 16 Apr 2021 12:05:53 +0100 [thread overview]
Message-ID: <20210416110553.GH2531743@casper.infradead.org> (raw)
In-Reply-To: <f51e1aa98cb94880a236d58c75c20994@AcuMS.aculab.com>
On Fri, Apr 16, 2021 at 07:32:35AM +0000, David Laight wrote:
> From: Matthew Wilcox <willy@infradead.org>
> > Sent: 15 April 2021 23:22
> >
> > On Thu, Apr 15, 2021 at 09:11:56PM +0000, David Laight wrote:
> > > Isn't it possible to move the field down one long?
> > > This might require an explicit zero - but this is not a common
> > > code path - the extra write will be noise.
> >
> > Then it overlaps page->mapping. See emails passim.
>
> The rules on overlaps make be wonder if every 'long'
> should be in its own union.
That was what we used to have. It was worse.
> The comments would need to say when each field is used.
> It would, at least, make these errors less common.
>
> That doesn't solve the 64bit dma_addr though.
>
> Actually rather that word-swapping dma_addr on 32bit BE
> could you swap over the two fields it overlays with.
> That might look messy in the .h, but it doesn't require
> an accessor function to do the swap - easily missed.
No.
WARNING: multiple messages have this Message-ID (diff)
From: Matthew Wilcox <willy@infradead.org>
To: David Laight <David.Laight@aculab.com>
Cc: Arnd Bergmann <arnd@kernel.org>,
Grygorii Strashko <grygorii.strashko@ti.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Matteo Croce <mcroce@linux.microsoft.com>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
Christoph Hellwig <hch@lst.de>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems
Date: Fri, 16 Apr 2021 12:05:53 +0100 [thread overview]
Message-ID: <20210416110553.GH2531743@casper.infradead.org> (raw)
In-Reply-To: <f51e1aa98cb94880a236d58c75c20994@AcuMS.aculab.com>
On Fri, Apr 16, 2021 at 07:32:35AM +0000, David Laight wrote:
> From: Matthew Wilcox <willy@infradead.org>
> > Sent: 15 April 2021 23:22
> >
> > On Thu, Apr 15, 2021 at 09:11:56PM +0000, David Laight wrote:
> > > Isn't it possible to move the field down one long?
> > > This might require an explicit zero - but this is not a common
> > > code path - the extra write will be noise.
> >
> > Then it overlaps page->mapping. See emails passim.
>
> The rules on overlaps make be wonder if every 'long'
> should be in its own union.
That was what we used to have. It was worse.
> The comments would need to say when each field is used.
> It would, at least, make these errors less common.
>
> That doesn't solve the 64bit dma_addr though.
>
> Actually rather that word-swapping dma_addr on 32bit BE
> could you swap over the two fields it overlays with.
> That might look messy in the .h, but it doesn't require
> an accessor function to do the swap - easily missed.
No.
WARNING: multiple messages have this Message-ID (diff)
From: Matthew Wilcox <willy@infradead.org>
To: David Laight <David.Laight@aculab.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-mips@vger.kernel.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: Fri, 16 Apr 2021 12:05:53 +0100 [thread overview]
Message-ID: <20210416110553.GH2531743@casper.infradead.org> (raw)
In-Reply-To: <f51e1aa98cb94880a236d58c75c20994@AcuMS.aculab.com>
On Fri, Apr 16, 2021 at 07:32:35AM +0000, David Laight wrote:
> From: Matthew Wilcox <willy@infradead.org>
> > Sent: 15 April 2021 23:22
> >
> > On Thu, Apr 15, 2021 at 09:11:56PM +0000, David Laight wrote:
> > > Isn't it possible to move the field down one long?
> > > This might require an explicit zero - but this is not a common
> > > code path - the extra write will be noise.
> >
> > Then it overlaps page->mapping. See emails passim.
>
> The rules on overlaps make be wonder if every 'long'
> should be in its own union.
That was what we used to have. It was worse.
> The comments would need to say when each field is used.
> It would, at least, make these errors less common.
>
> That doesn't solve the 64bit dma_addr though.
>
> Actually rather that word-swapping dma_addr on 32bit BE
> could you swap over the two fields it overlays with.
> That might look messy in the .h, but it doesn't require
> an accessor function to do the swap - easily missed.
No.
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next prev parent reply other threads:[~2021-04-16 11:06 UTC|newest]
Thread overview: 105+ 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 ` Matthew Wilcox (Oracle)
2021-04-10 20:52 ` Matthew Wilcox (Oracle)
2021-04-10 20:52 ` [PATCH 1/1] mm: " Matthew Wilcox (Oracle)
2021-04-10 20:52 ` Matthew Wilcox (Oracle)
2021-04-10 20:52 ` Matthew Wilcox (Oracle)
2021-04-11 9:43 ` Jesper Dangaard Brouer
2021-04-11 9:43 ` Jesper Dangaard Brouer
2021-04-11 9:43 ` Jesper Dangaard Brouer
2021-04-11 10:33 ` Matthew Wilcox
2021-04-11 10:33 ` Matthew Wilcox
2021-04-11 10:33 ` Matthew Wilcox
2021-04-12 1:15 ` Matthew Wilcox
2021-04-12 1:15 ` Matthew Wilcox
2021-04-12 1:15 ` Matthew Wilcox
2021-04-14 8:10 ` Jesper Dangaard Brouer
2021-04-14 8:10 ` Jesper Dangaard Brouer
2021-04-14 8:10 ` Jesper Dangaard Brouer
2021-04-14 11:50 ` Matthew Wilcox
2021-04-14 11:50 ` Matthew Wilcox
2021-04-14 11:50 ` Matthew Wilcox
2021-04-14 11:56 ` Ilias Apalodimas
2021-04-14 11:56 ` Ilias Apalodimas
2021-04-14 11:56 ` Ilias Apalodimas
2021-04-14 15:52 ` David Laight
2021-04-14 15:52 ` David Laight
2021-04-14 15:52 ` David Laight
2021-04-14 15:52 ` David Laight
2021-04-14 19:13 ` Jesper Dangaard Brouer
2021-04-14 19:13 ` Jesper Dangaard Brouer
2021-04-14 19:13 ` Jesper Dangaard Brouer
2021-04-14 21:35 ` Matthew Wilcox
2021-04-14 21:35 ` Matthew Wilcox
2021-04-14 21:35 ` Matthew Wilcox
2021-04-14 21:56 ` David Laight
2021-04-14 21:56 ` David Laight
2021-04-14 21:56 ` David Laight
2021-04-14 21:56 ` David Laight
2021-04-15 18:08 ` Jesper Dangaard Brouer
2021-04-15 18:08 ` Jesper Dangaard Brouer
2021-04-15 18:08 ` Jesper Dangaard Brouer
2021-04-15 18:08 ` Jesper Dangaard Brouer
2021-04-15 18:21 ` Matthew Wilcox
2021-04-15 18:21 ` Matthew Wilcox
2021-04-15 18:21 ` Matthew Wilcox
2021-04-15 18:21 ` Matthew Wilcox
2021-04-15 21:11 ` David Laight
2021-04-15 21:11 ` David Laight
2021-04-15 21:11 ` David Laight
2021-04-15 21:11 ` David Laight
2021-04-15 22:22 ` Matthew Wilcox
2021-04-15 22:22 ` Matthew Wilcox
2021-04-15 22:22 ` Matthew Wilcox
2021-04-15 22:22 ` Matthew Wilcox
2021-04-16 7:32 ` David Laight
2021-04-16 7:32 ` David Laight
2021-04-16 7:32 ` David Laight
2021-04-16 7:32 ` David Laight
2021-04-16 11:05 ` Matthew Wilcox [this message]
2021-04-16 11:05 ` Matthew Wilcox
2021-04-16 11:05 ` Matthew Wilcox
2021-04-16 11:05 ` Matthew Wilcox
2021-04-16 15:27 ` Matthew Wilcox
2021-04-16 15:27 ` Matthew Wilcox
2021-04-16 15:27 ` Matthew Wilcox
2021-04-16 15:27 ` Matthew Wilcox
2021-04-16 17:08 ` Jesper Dangaard Brouer
2021-04-16 17:08 ` Jesper Dangaard Brouer
2021-04-16 17:08 ` Jesper Dangaard Brouer
2021-04-16 17:08 ` Jesper Dangaard Brouer
2021-04-17 3:19 ` Matthew Wilcox
2021-04-17 3:19 ` Matthew Wilcox
2021-04-17 3:19 ` Matthew Wilcox
2021-04-17 3:19 ` Matthew Wilcox
2021-04-17 10:31 ` Arnd Bergmann
2021-04-17 10:31 ` Arnd Bergmann
2021-04-17 10:31 ` Arnd Bergmann
2021-04-17 10:31 ` Arnd Bergmann
2021-04-17 13:56 ` Matthew Wilcox
2021-04-17 13:56 ` Matthew Wilcox
2021-04-17 13:56 ` Matthew Wilcox
2021-04-17 13:56 ` Matthew Wilcox
2021-04-17 17:30 ` Arnd Bergmann
2021-04-17 17:30 ` Arnd Bergmann
2021-04-17 17:30 ` Arnd Bergmann
2021-04-17 17:30 ` Arnd Bergmann
2021-04-17 10:59 ` David Laight
2021-04-17 10:59 ` David Laight
2021-04-17 10:59 ` David Laight
2021-04-17 10:59 ` David Laight
2021-04-19 6:34 ` Christoph Hellwig
2021-04-19 6:34 ` Christoph Hellwig
2021-04-19 6:34 ` Christoph Hellwig
2021-04-19 6:34 ` Christoph Hellwig
2021-04-19 7:15 ` Ilias Apalodimas
2021-04-19 7:15 ` Ilias Apalodimas
2021-04-19 7:15 ` Ilias Apalodimas
2021-04-19 7:15 ` Ilias Apalodimas
2021-04-12 18:23 ` Matthew Wilcox
2021-04-12 18:23 ` Matthew Wilcox
2021-04-12 18:23 ` Matthew Wilcox
2021-04-13 8:21 ` David Laight
2021-04-13 8:21 ` David Laight
2021-04-13 8:21 ` David Laight
2021-04-13 8:21 ` David Laight
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