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authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2017-07-06 15:39:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-06 16:24:33 -0700
commit8bc3c3fe4f3483374fed4254e47a14ec8c555909 (patch)
treeca1f3b9e9ccba747519a47176ea2e7b5dbd33d55
parentd73d3c9f698c5e474e58acbaba87a1f134772747 (diff)
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>
-rw-r--r--mm/memory.c2
-rw-r--r--mm/mprotect.c2
2 files changed, 0 insertions, 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) &&