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[195.135.220.15]) by mx.google.com with ESMTPS id b35si36390690eda.123.2019.08.09.01.03.21 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 09 Aug 2019 01:03:22 -0700 (PDT) Received-SPF: pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 67869AECD; Fri, 9 Aug 2019 08:03:21 +0000 (UTC) Subject: Re: [PATCH v2] mm/mmap.c: refine find_vma_prev with rb_last To: Wei Yang , akpm@linux-foundation.org, mhocko@suse.com, kirill.shutemov@linux.intel.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190809001928.4950-1-richardw.yang@linux.intel.com> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190809001928.4950-1-richardw.yang@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 8/9/19 2:19 AM, Wei Yang wrote: > When addr is out of the range of the whole rb_tree, pprev will points to > the right-most node. rb_tree facility already provides a helper > function, rb_last, to do this task. We can leverage this instead of > re-implement it. > > This patch refines find_vma_prev with rb_last to make it a little nicer > to read. > > Signed-off-by: Wei Yang Acked-by: Vlastimil Babka Nit below: > --- > v2: leverage rb_last > --- > mm/mmap.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 7e8c3e8ae75f..f7ed0afb994c 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2270,12 +2270,9 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr, > if (vma) { > *pprev = vma->vm_prev; > } else { > - struct rb_node *rb_node = mm->mm_rb.rb_node; > - *pprev = NULL; > - while (rb_node) { > - *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb); > - rb_node = rb_node->rb_right; > - } > + struct rb_node *rb_node = rb_last(&mm->mm_rb); > + *pprev = !rb_node ? NULL : > + rb_entry(rb_node, struct vm_area_struct, vm_rb); It's perhaps more common to write it like: *pprev = rb_node ? rb_entry(rb_node, struct vm_area_struct, vm_rb) : NULL; > } > return vma; > } >