From: Nam Cao <namcao@linutronix.de>
To: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jaya Kumar <jayalk@intworks.biz>, Daniel Vetter <daniel@ffwll.ch>,
Helge Deller <deller@gmx.de>,
Javier Martinez Canillas <javierm@redhat.com>,
linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org, tiwai@suse.de,
bigeasy@linutronix.de, patrik.r.jakobsson@gmail.com,
Vegard Nossum <vegard.nossum@oracle.com>,
George Kennedy <george.kennedy@oracle.com>,
Darren Kenny <darren.kenny@oracle.com>,
chuansheng.liu@intel.com,
Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] fbdev: fix incorrect address computation in deferred IO
Date: Tue, 23 Apr 2024 13:39:33 +0200 [thread overview]
Message-ID: <20240423113933.IpMjHGw7@linutronix.de> (raw)
In-Reply-To: <64c1585d-70e0-47d4-9d78-405b483b433c@suse.de>
On Tue, Apr 23, 2024 at 01:27:09PM +0200, Thomas Zimmermann wrote:
> Am 23.04.24 um 11:55 schrieb Nam Cao:
...
> > > The page-fault handler at [1] use vm_fault.pgoff to retrieve the page
> > > structure. Can we do the same here and avoid that computation?
> > Yes, thanks for the suggestion.
> >
> > It will change things a bit: offset will not be the exact value anymore,
> > but will be rounded down to multiple of PAGE_SIZE. But that doesn't matter,
> > because it will only be used to calculate the page offset later on.
> >
> > We can clean this up and rename this "offset" to "pg_offset". But that's
> > for another day.
>
> But can't we use struct vm_fault.pgoff directly? The page-fault handler has
> used it since forever. The look-up code for the pageref should probably do
> the same, because there's a 1:1 connection between the page and the pageref.
> The pageref structure only exists because we cannot store its data in struct
> page directly.
>
> AFAICT pgoff is exactly the value want to compute. See [1] and the
> calculation at [2].
Completely agree. I just wanted to point out that the value inside the
variable "offset" won't be the same as before, but it's still correct.
I just tested the patch on real hardware, will send it shortly.
Best regards,
Nam
prev parent reply other threads:[~2024-04-23 11:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-19 19:00 [PATCH] fbdev: fix incorrect address computation in deferred IO Nam Cao
2024-04-23 8:37 ` Thomas Zimmermann
2024-04-23 9:55 ` Nam Cao
2024-04-23 11:27 ` Thomas Zimmermann
2024-04-23 11:39 ` Nam Cao [this message]
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