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Date:   Tue, 30 Mar 2021 15:49:03 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Alistair Popple <apopple@nvidia.com>
Cc:     linux-mm@kvack.org, nouveau@lists.freedesktop.org,
        bskeggs@redhat.com, akpm@linux-foundation.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm-ppc@vger.kernel.org, dri-devel@lists.freedesktop.org,
        jhubbard@nvidia.com, rcampbell@nvidia.com, jglisse@redhat.com,
        hch@infradead.org, daniel@ffwll.ch, willy@infradead.org,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v7 3/8] mm/rmap: Split try_to_munlock from try_to_unmap
Message-ID: <20210330184903.GZ2356281@nvidia.com>
References: <20210326000805.2518-1-apopple@nvidia.com>
 <20210326000805.2518-4-apopple@nvidia.com>
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On Fri, Mar 26, 2021 at 11:08:00AM +1100, Alistair Popple wrote:

> +static bool try_to_munlock_one(struct page *page, struct vm_area_struct *vma,
> +		     unsigned long address, void *arg)
> +{

Is this function name right?

> +	struct page_vma_mapped_walk pvmw = {
> +		.page = page,
> +		.vma = vma,
> +		.address = address,
> +	};
> +
> +	/* munlock has nothing to gain from examining un-locked vmas */
> +	if (!(vma->vm_flags & VM_LOCKED))
> +		return true;
> +
> +	while (page_vma_mapped_walk(&pvmw)) {
> +		/* PTE-mapped THP are never mlocked */
> +		if (!PageTransCompound(page)) {
> +			/*
> +			 * Holding pte lock, we do *not* need
> +			 * mmap_lock here
> +			 */
> +			mlock_vma_page(page);

Because the only action this function seems to take is to call
*mlock*_vma_page()

> +		}
> +		page_vma_mapped_walk_done(&pvmw);
> +
> +		/* found a mlocked page, no point continuing munlock check */
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  /**
>   * try_to_munlock - try to munlock a page
>   * @page: the page to be munlocked
> @@ -1796,8 +1821,7 @@ bool try_to_unmap(struct page *page, enum ttu_flags flags)
>  void try_to_munlock(struct page *page)
>  {

But this is also called try_to_munlock ??

/**
 * try_to_munlock - try to munlock a page
 * @page: the page to be munlocked
 *
 * Called from munlock code.  Checks all of the VMAs mapping the page
 * to make sure nobody else has this page mlocked. The page will be
 * returned with PG_mlocked cleared if no other vmas have it mlocked.
 */

So what clears PG_mlocked on this call path?

Something needs attention here..

Jason