linux-kernel - Re: [PATCH 1/3] fs/userfaultfd.c: remove a redundant check on end

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Message-ID: <20191012091604.GB6047@richard>
Date:   Sat, 12 Oct 2019 17:16:04 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     Wei Yang <richardw.yang@...ux.intel.com>
Cc:     viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] fs/userfaultfd.c: remove a redundant check on end

Ping for comment :-)

On Fri, Sep 13, 2019 at 05:31:08AM +0800, Wei Yang wrote:
>For the ending vma, there is a check to make sure the end is huge page
>aligned.
>
>The *if* check makes sure vm_start < end <= vm_end. While the first half
>is not necessary, because the *for* clause makes sure vm_start < end.
>
>This patch just removes it.
>
>Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
>---
> fs/userfaultfd.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
>diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
>index 653d8f7c453c..9ce09ac619a2 100644
>--- a/fs/userfaultfd.c
>+++ b/fs/userfaultfd.c
>@@ -1402,8 +1402,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
> 		 * If this vma contains ending address, and huge pages
> 		 * check alignment.
> 		 */
>-		if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
>-		    end > cur->vm_start) {
>+		if (is_vm_hugetlb_page(cur) && end <= cur->vm_end) {
> 			unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
> 
> 			ret = -EINVAL;
>-- 
>2.17.1

-- 
Wei Yang
Help you, Help me