lkml.org 
[lkml]   [2020]   [Oct]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mm: fix potential pte_unmap_unlock pte error
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.

\
 
 \ /
  Last update: 2020-10-16 16:05    [W:0.056 / U:0.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site