From 8bc3c3fe4f3483374fed4254e47a14ec8c555909 Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Thu, 6 Jul 2017 15:39:26 -0700 Subject: [PATCH] mm: drop NULL return check of pte_offset_map_lock() 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. Link: http://lkml.kernel.org/r/1495089737-1292-1-git-send-email-n-horiguchi@ah.jp.nec.com Signed-off-by: Naoya Horiguchi Acked-by: Vlastimil Babka Cc: Mel Gorman Cc: Johannes Weiner Cc: Andrea Arcangeli Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 2 -- mm/mprotect.c | 2 -- 2 files changed, 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index bb11c474857e..bf3aab1684e9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4014,8 +4014,6 @@ 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 a/mm/mprotect.c b/mm/mprotect.c index 8edd0d576254..1a8c9ca83e48 100644 --- a/mm/mprotect.c +++ b/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) && -- 2.20.1