linux-kernel - Re: [PATCH v2] userfaultfd: clear flag if remap event not enabled

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Message-Id: <FB9EEE4D-B2E6-44B9-9145-259E785AD3F4@oracle.com>
Date:   Tue, 11 Dec 2018 06:46:13 -0700
From:   William Kucharski <william.kucharski@...cle.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Hugh Dickins <hughd@...gle.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Pravin Shedge <pravin.shedge4linux@...il.com>,
        linux-mm@...ck.org
Subject: Re: [PATCH v2] userfaultfd: clear flag if remap event not enabled



> On Dec 10, 2018, at 10:34 PM, Peter Xu <peterx@...hat.com> wrote:
> 
> ---
> fs/userfaultfd.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cd58939dc977..4567b5b6fd32 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -736,10 +736,18 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,
> 	struct userfaultfd_ctx *ctx;
> 
> 	ctx = vma->vm_userfaultfd_ctx.ctx;
> -	if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {
> +
> +	if (!ctx)
> +		return;
> +
> +	if (ctx->features & UFFD_FEATURE_EVENT_REMAP) {
> 		vm_ctx->ctx = ctx;
> 		userfaultfd_ctx_get(ctx);
> 		WRITE_ONCE(ctx->mmap_changing, true);
> +	} else {
> +		/* Drop uffd context if remap feature not enabled */
> +		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
> +		vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
> 	}
> }
> 
> -- 
> 2.17.1
> 

Looks good.

Reviewed-by: William Kucharski <william.kucharski@...cle.com>