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 1ad9f62 ("mm: numa: recheck for transhuge pages under lock during protection changes") and still remains after commit 175ad4f ("mm: mprotect: use pmd_trans_unstable instead of taking the pmd_lock") which partially reverts 1ad9f62. 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/[email protected] Signed-off-by: Naoya Horiguchi <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Johannes Weiner <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: Rik van Riel <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
mrcsosa · Jul 6, 2017 · 8bc3c3f · 8bc3c3f
1 parent d73d3c9
commit 8bc3c3f
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diff --git 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
@@ -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) &&