On Tue, Apr 23, 2013 at 02:53:44PM -0700, Greg Kroah-Hartman wrote: > 3.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > > commit 9cc3a5bd40067b9a0fbd49199d0780463fc2140f upstream. > > With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in > initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory > error happens on a hugepage and the affected processes try to access the > error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0) in > get_page(). Is this required? You didn't apply the previous patch referred to above (commit a2fce9143057) to 3.4.y or 3.0.y since it claimed to fix a regression in 3.7 (commit 314e51b9851b 'mm: kill vma flag VM_RESERVED and mm->reserved_vm counter'). I'm not saying it *isn't* required, mind. Ben. > The reason for this bug is that coredump-related code doesn't recognise > "hugepage hwpoison entry" with which a pmd entry is replaced when a memory > error occurs on a hugepage. > > In other words, physical address information is stored in different bit > layout between hugepage hwpoison entry and pmd entry, so > follow_hugetlb_page() which is called in get_dump_page() returns a wrong > page from a given address. > > The expected behavior is like this: > > absent is_swap_pte FOLL_DUMP Expected behavior > ------------------------------------------------------------------- > true false false hugetlb_fault > false true false hugetlb_fault > false false false return page > true false true skip page (to avoid allocation) > false true true hugetlb_fault > false false true return page > > With this patch, we can call hugetlb_fault() and take proper actions (we > wait for migration entries, fail with VM_FAULT_HWPOISON_LARGE for > hwpoisoned entries,) and as the result we can dump all hugepages except > for hwpoisoned ones. > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Cc: Rik van Riel <riel@xxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxx> > Cc: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx> > Acked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > --- > mm/hugetlb.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2906,7 +2906,17 @@ int follow_hugetlb_page(struct mm_struct > break; > } > > - if (absent || > + /* > + * We need call hugetlb_fault for both hugepages under migration > + * (in which case hugetlb_fault waits for the migration,) and > + * hwpoisoned hugepages (in which case we need to prevent the > + * caller from accessing to them.) In order to do this, we use > + * here is_swap_pte instead of is_hugetlb_entry_migration and > + * is_hugetlb_entry_hwpoisoned. This is because it simply covers > + * both cases, and because we can't follow correct pages > + * directly from any kind of swap entries. > + */ > + if (absent || is_swap_pte(huge_ptep_get(pte)) || > ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) { > int ret; > -- Ben Hutchings We get into the habit of living before acquiring the habit of thinking. - Albert Camus -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html