diff options
| -rw-r--r-- | mm/migrate.c | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index a73504ff5ab..4e0eccca5e2 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -153,11 +153,6 @@ static void remove_migration_pte(struct vm_area_struct *vma, return; } - if (mem_cgroup_charge(new, mm, GFP_KERNEL)) { - pte_unmap(ptep); - return; - } - ptl = pte_lockptr(mm, pmd); spin_lock(ptl); pte = *ptep; @@ -169,6 +164,20 @@ static void remove_migration_pte(struct vm_area_struct *vma, if (!is_migration_entry(entry) || migration_entry_to_page(entry) != old) goto out; + /* + * Yes, ignore the return value from a GFP_ATOMIC mem_cgroup_charge. + * Failure is not an option here: we're now expected to remove every + * migration pte, and will cause crashes otherwise. Normally this + * is not an issue: mem_cgroup_prepare_migration bumped up the old + * page_cgroup count for safety, that's now attached to the new page, + * so this charge should just be another incrementation of the count, + * to keep in balance with rmap.c's mem_cgroup_uncharging. But if + * there's been a force_empty, those reference counts may no longer + * be reliable, and this charge can actually fail: oh well, we don't + * make the situation any worse by proceeding as if it had succeeded. + */ + mem_cgroup_charge(new, mm, GFP_ATOMIC); + get_page(new); pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); if (is_write_migration_entry(entry)) |