Messages in this thread | | | Date | Fri, 16 Oct 2020 16:05:37 +0200 | From | osalvador@suse ... | Subject | Re: [PATCH] mm: fix potential pte_unmap_unlock pte error |
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On 2020-10-16 15:42, Michal Hocko wrote: > OK, I finally managed to convince my friday brain to think and grasped > what the code is intended to do. The loop is hairy and we want to > prevent from spurious EIO when all the pages are on a proper node. So > the check has to be done inside the loop. Anyway I would find the > following fix less error prone and easier to follow > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index eddbe4e56c73..8cc1fc9c4d13 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -525,7 +525,7 @@ static int queue_pages_pte_range(pmd_t *pmd, > unsigned long addr, > unsigned long flags = qp->flags; > int ret; > bool has_unmovable = false; > - pte_t *pte; > + pte_t *pte, *mapped_pte; > spinlock_t *ptl; > > ptl = pmd_trans_huge_lock(pmd, vma); > @@ -539,7 +539,7 @@ static int queue_pages_pte_range(pmd_t *pmd, > unsigned long addr, > if (pmd_trans_unstable(pmd)) > return 0; > > - pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > + mapped_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); > for (; addr != end; pte++, addr += PAGE_SIZE) { > if (!pte_present(*pte)) > continue; > @@ -571,7 +571,7 @@ static int queue_pages_pte_range(pmd_t *pmd, > unsigned long addr, > } else > break; > } > - pte_unmap_unlock(pte - 1, ptl); > + pte_unmap_unlock(mapped_pte, ptl); > cond_resched(); > > if (has_unmovable)
It is more clear to grasp, definitely.
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