diff options
| -rw-r--r-- | mm/mprotect.c | 46 |
1 files changed, 15 insertions, 31 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c index f9c07f54dd62..a45b4dc6a7f5 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -33,34 +33,6 @@ #include "internal.h" -/* - * For a prot_numa update we only hold mmap_sem for read so there is a - * potential race with faulting where a pmd was temporarily none. This - * function checks for a transhuge pmd under the appropriate lock. It - * returns a pte if it was successfully locked or NULL if it raced with - * a transhuge insertion. - */ -static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long addr, int prot_numa, spinlock_t **ptl) -{ - pte_t *pte; - spinlock_t *pmdl; - - /* !prot_numa is protected by mmap_sem held for write */ - if (!prot_numa) - return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); - - pmdl = pmd_lock(vma->vm_mm, pmd); - if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) { - spin_unlock(pmdl); - return NULL; - } - - pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl); - spin_unlock(pmdl); - return pte; -} - static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr, unsigned long end, pgprot_t newprot, int dirty_accountable, int prot_numa) @@ -71,7 +43,21 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, unsigned long pages = 0; int target_node = NUMA_NO_NODE; - pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl); + /* + * Can be called with only the mmap_sem for reading by + * prot_numa so we must check the pmd isn't constantly + * changing from under us from pmd_none to pmd_trans_huge + * and/or the other way around. + */ + if (pmd_trans_unstable(pmd)) + return 0; + + /* + * The pmd points to a regular pte so the pmd can't change + * from under us even if the mmap_sem is only hold for + * reading. + */ + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); if (!pte) return 0; @@ -177,8 +163,6 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { if (next - addr != HPAGE_PMD_SIZE) { __split_huge_pmd(vma, pmd, addr, false, NULL); - if (pmd_trans_unstable(pmd)) - continue; } else { int nr_ptes = change_huge_pmd(vma, pmd, addr, newprot, prot_numa); |