Re: [PATCH 12/39] ALSA: pcm: use vm_insert_page() to map PCM status page

From: Takashi Iwai <tiwai@suse.de>
To: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
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Subject: Re: [PATCH 12/39] ALSA: pcm: use vm_insert_page() to map PCM status page
Date: Thu, 10 Sep 2026 18:15:01 +0200	[thread overview]
Message-ID: <87qzj1jd6i.wl-tiwai@suse.de> (raw)
In-Reply-To: <20260908-b4-mmap-prepare-vma-flag-sanify-v1-12-dacf19cce22b@kernel.org>

On Tue, 08 Sep 2026 22:01:16 +0200,
Lorenzo Stoakes (ARM) wrote:
> 
> There's no need to keep a fault handler around for this, instead map on
> mmap.
> 
> While we're here, rename area to vma to be consistent.
> 
> This correctly makes the mapping a mixed map mapping.
> 
> This works towards establishing the invariant that only PFN mapped or mixed
> map mappings may clear the VM_MAYWRITE flag. The status page mapping clears
> VM_MAYWRITE, so it must be kernel-owned; the control page mapping remains
> writable and is left fault-based.
> 
> The assumption is made that the struct pcm_mmap_status structure is at most
> a page in size, which is asserted as a build bug.
> 
> This is safe to assume, as the size of the structure is 56 bytes at most.
> 
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

Acked-by: Takashi Iwai <tiwai@suse.de>


thanks,

Takashi