linux-kernel - Re: [PATCH] mm: thp: fix a double unlock bug

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Date:   Tue, 1 Jun 2021 10:30:17 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] mm: thp: fix a double unlock bug

On Tue, Jun 1, 2021 at 2:24 AM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> We're supposed to be holding the "vmf->ptl" spin_lock when we goto
> out_map.  The lock is dropped after if finishes cleaning up.
>
> Fixes: 9aff7b33c74a ("mm: thp: refactor NUMA fault handling")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Thanks for catching this. Acked-by: Yang Shi <shy828301@...il.com>

> ---
>  mm/huge_memory.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index e353bbc6cee3..caa0148f15bb 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1465,10 +1465,8 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
>
>         pmd = pmd_modify(oldpmd, vma->vm_page_prot);
>         page = vm_normal_page_pmd(vma, haddr, pmd);
> -       if (!page) {
> -               spin_unlock(vmf->ptl);
> +       if (!page)
>                 goto out_map;
> -       }
>
>         /* See similar comment in do_numa_page for explanation */
>         if (!was_writable)
> --
> 2.30.2
>