linux-kernel - Re: [PATCH 8/8] binder: use per-vma lock in page installation

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Message-ID: <ZyqRvLlPdvKknbWE@google.com>
Date: Tue, 5 Nov 2024 21:44:28 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Christian Brauner <brauner@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com,
	Nhat Pham <nphamcs@...il.com>, Johannes Weiner <hannes@...xchg.org>,
	Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH 8/8] binder: use per-vma lock in page installation

On Tue, Nov 05, 2024 at 08:02:50PM +0000, Carlos Llamas wrote:
> +static struct page *binder_page_lookup(struct mm_struct *mm,
> +				       struct vm_area_struct *vma,
> +				       unsigned long addr,
> +				       bool mm_locked)
> +{
> +	struct folio_walk fw;
> +	struct page *page;
> +
> +	/* folio_walk_start() requires the mmap_lock */
> +	if (!mm_locked)
> +		mmap_read_lock(mm);
> +
> +	if (!folio_walk_start(&fw, vma, addr, 0))
> +		return NULL;

Just realized that mmap_lock need to be released if folio_walk_start()
fails and !mm_locked. I'll add the fix for v2.