Patch-mainline: v4.13-rc1
Git-commit: 8bc3c3fe4f3483374fed4254e47a14ec8c555909
References: bsc#1184207
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
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 <n-horiguchi@ah.jp.nec.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
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) &&
--
2.34.1