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mm: drop NULL return check of pte_offset_map_lock()

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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 1ad9f620c3 ("mm: numa: recheck for transhuge pages under lock
during protection changes") and still remains after commit 175ad4f1e7
("mm: mprotect: use pmd_trans_unstable instead of taking the pmd_lock")
which partially reverts 1ad9f620c3.  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]>
This commit is contained in:
Naoya Horiguchi 2017-07-06 15:39:26 -07:00 • committed by Linus Torvalds
commit 8bc3c3fe4f
2 changed files with 0 additions and 4 deletions
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2
mm/mprotect.c
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@ -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) &&