linux-kernel - Re: [PATCH 20/22] mm/mremap: Use vma_lookup() in vma_to

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Date:   Thu, 20 May 2021 20:47:19 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Liam Howlett <liam.howlett@...cle.com>
Cc:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Song Liu <songliubraving@...com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <michel@...pinasse.org>
Subject: Re: [PATCH 20/22] mm/mremap: Use vma_lookup() in vma_to_resize()

On Mon, 10 May 2021, Liam Howlett wrote:

>Use vma_lookup() to find the VMA at a specific address.  As vma_lookup()
>will return NULL if the address is not within any VMA, the start address
>no longer needs to be validated.
>
>Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
>---
> mm/mremap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/mm/mremap.c b/mm/mremap.c
>index 47c255b60150..04143755cd1e 100644
>--- a/mm/mremap.c
>+++ b/mm/mremap.c
>@@ -634,10 +634,10 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
> 	unsigned long *p)
> {
> 	struct mm_struct *mm = current->mm;
>-	struct vm_area_struct *vma = find_vma(mm, addr);
>+	struct vm_area_struct *vma = vma_lookup(mm, addr);
> 	unsigned long pgoff;
>

Nit, but could the vma_lookup() call be separate from the declaration
of vma?

	vma = find_vma();
>-	if (!vma || vma->vm_start > addr)
>+	if (!vma)
> 		return ERR_PTR(-EFAULT);

Thanks,
Davidlohr