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Tue, 01 Oct 2019 04:47:00 -0700 (PDT) Date: Tue, 1 Oct 2019 11:47:00 +0000 From: Wei Yang To: Peter Zijlstra Cc: Wei Yang , dave.hansen@linux.intel.com, luto@kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] x86/mm: replace a goto by merging two if clause Message-ID: <20191001114700.wqcglmbrajqkmc22@master> Reply-To: Wei Yang References: <20190919020844.27461-1-richardw.yang@linux.intel.com> <20190919020844.27461-2-richardw.yang@linux.intel.com> <20190923092231.GJ2349@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190923092231.GJ2349@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 23, 2019 at 11:22:31AM +0200, Peter Zijlstra wrote: >On Thu, Sep 19, 2019 at 10:08:44AM +0800, Wei Yang wrote: >> There is only one place to use good_area jump, which could be reduced by >> merging the following two if clause. >> >> Signed-off-by: Wei Yang >> --- >> arch/x86/mm/fault.c | 11 +++++------ >> 1 file changed, 5 insertions(+), 6 deletions(-) >> >> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c >> index 9d18b73b5f77..72ce6c69e195 100644 >> --- a/arch/x86/mm/fault.c >> +++ b/arch/x86/mm/fault.c >> @@ -1390,18 +1390,17 @@ void do_user_addr_fault(struct pt_regs *regs, >> vma = find_vma(mm, address); >> if (unlikely(!vma)) >> goto bad_area; >> - if (likely(vma->vm_start <= address)) >> - goto good_area; >> - if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) >> - goto bad_area; >> - if (unlikely(expand_stack(vma, address))) >> + if (likely(vma->vm_start <= address)) { >> + /* good area, do nothing */ >> + } else if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)) || >> + unlikely(expand_stack(vma, address))) { >> goto bad_area; >> + } >> >> /* >> * Ok, we have a good vm_area for this memory access, so >> * we can handle it.. >> */ >> -good_area: >> if (unlikely(access_error(hw_error_code, vma))) { >> bad_area_access_error(regs, hw_error_code, address, vma); >> return; > >I find the old code far easier to read... is there any actual reason to >do this? Hi, Peter, Do you have some comment for the Patch 1? -- Wei Yang Help you, Help me