diff options
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r-- | mm/huge_memory.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 530e6427f823..6c6f5ccfcda1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1269,6 +1269,16 @@ out_unlock: return ret; } +/* + * FOLL_FORCE can write to even unwritable pmd's, but only + * after we've gone through a COW cycle and they are dirty. + */ +static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags) +{ + return pmd_write(pmd) || + ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd)); +} + struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, unsigned long addr, pmd_t *pmd, @@ -1279,7 +1289,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, assert_spin_locked(pmd_lockptr(mm, pmd)); - if (flags & FOLL_WRITE && !pmd_write(*pmd)) + if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags)) goto out; /* Avoid dumping huge zero page */ @@ -1353,8 +1363,11 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, */ if (unlikely(pmd_trans_migrating(*pmdp))) { page = pmd_page(*pmdp); + if (!get_page_unless_zero(page)) + goto out_unlock; spin_unlock(ptl); wait_on_page_locked(page); + put_page(page); goto out; } @@ -1386,8 +1399,11 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, /* Migration could have started since the pmd_trans_migrating check */ if (!page_locked) { + if (!get_page_unless_zero(page)) + goto out_unlock; spin_unlock(ptl); wait_on_page_locked(page); + put_page(page); page_nid = -1; goto out; } |