From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 801716B0038 for ; Thu, 18 May 2017 02:42:24 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id n75so25820657pfh.0 for ; Wed, 17 May 2017 23:42:24 -0700 (PDT) Received: from mail-pg0-x244.google.com (mail-pg0-x244.google.com. [2607:f8b0:400e:c05::244]) by mx.google.com with ESMTPS id o89si4326277pfa.348.2017.05.17.23.42.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 May 2017 23:42:23 -0700 (PDT) Received: by mail-pg0-x244.google.com with SMTP id u187so4781147pgb.1 for ; Wed, 17 May 2017 23:42:23 -0700 (PDT) From: Naoya Horiguchi Subject: [PATCH v1] mm: drop NULL return check of pte_offset_map_lock() Date: Thu, 18 May 2017 15:42:17 +0900 Message-Id: <1495089737-1292-1-git-send-email-n-horiguchi@ah.jp.nec.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Mel Gorman , Johannes Weiner , Andrea Arcangeli , Rik van Riel , Andrew Morton , linux-kernel@vger.kernel.org, Naoya Horiguchi pte_offset_map_lock() finds and takes ptl, and returns pte. But some callers return without unlocking the ptl when pte == NULL, which seems weird. Git history said that !pte check in change_pte_range() was introduced in commit 1ad9f620c3a2 ("mm: numa: recheck for transhuge pages under lock during protection changes") and still remains after commit 175ad4f1e7a2 ("mm: mprotect: use pmd_trans_unstable instead of taking the pmd_lock") which partially reverts 1ad9f620c3a2. So I think that it's just dead code. Many other caller of pte_offset_map_lock() never check NULL return, so let's do likewise. Signed-off-by: Naoya Horiguchi --- mm/memory.c | 2 -- mm/mprotect.c | 2 -- 2 files changed, 4 deletions(-) diff --git v4.11-rc6-mmotm-2017-04-13-14-50/mm/memory.c v4.11-rc6-mmotm-2017-04-13-14-50_patched/mm/memory.c index 8ae6700..c17fad1d 100644 --- v4.11-rc6-mmotm-2017-04-13-14-50/mm/memory.c +++ v4.11-rc6-mmotm-2017-04-13-14-50_patched/mm/memory.c @@ -4040,8 +4040,6 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address, goto out; ptep = pte_offset_map_lock(mm, pmd, address, ptlp); - if (!ptep) - goto out; if (!pte_present(*ptep)) goto unlock; *ptepp = ptep; diff --git v4.11-rc6-mmotm-2017-04-13-14-50/mm/mprotect.c v4.11-rc6-mmotm-2017-04-13-14-50_patched/mm/mprotect.c index 8fd010f..d60a1ee 100644 --- v4.11-rc6-mmotm-2017-04-13-14-50/mm/mprotect.c +++ v4.11-rc6-mmotm-2017-04-13-14-50_patched/mm/mprotect.c @@ -58,8 +58,6 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, * reading. */ pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); - if (!pte) - return 0; /* Get target node for single threaded private VMAs */ if (prot_numa && !(vma->vm_flags & VM_SHARED) && -- 2.7.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org