From: Naoya Horiguchi <[email protected]>
Now error handling code is prepared, so remove the blocking code and
enable memory error handling on 1GB hugepage.
Signed-off-by: Naoya Horiguchi <[email protected]>
---
include/linux/mm.h | 1 -
include/ras/ras_event.h | 1 -
mm/memory-failure.c | 16 ----------------
3 files changed, 18 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 04de0c3e4f9f..58a6aa916e4f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3238,7 +3238,6 @@ enum mf_action_page_type {
MF_MSG_DIFFERENT_COMPOUND,
MF_MSG_HUGE,
MF_MSG_FREE_HUGE,
- MF_MSG_NON_PMD_HUGE,
MF_MSG_UNMAP_FAILED,
MF_MSG_DIRTY_SWAPCACHE,
MF_MSG_CLEAN_SWAPCACHE,
diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
index d0337a41141c..cbd3ddd7c33d 100644
--- a/include/ras/ras_event.h
+++ b/include/ras/ras_event.h
@@ -360,7 +360,6 @@ TRACE_EVENT(aer_event,
EM ( MF_MSG_DIFFERENT_COMPOUND, "different compound page after locking" ) \
EM ( MF_MSG_HUGE, "huge page" ) \
EM ( MF_MSG_FREE_HUGE, "free huge page" ) \
- EM ( MF_MSG_NON_PMD_HUGE, "non-pmd-sized huge page" ) \
EM ( MF_MSG_UNMAP_FAILED, "unmapping failed page" ) \
EM ( MF_MSG_DIRTY_SWAPCACHE, "dirty swapcache page" ) \
EM ( MF_MSG_CLEAN_SWAPCACHE, "clean swapcache page" ) \
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index babeb34f7477..ced033a99e19 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -725,7 +725,6 @@ static const char * const action_page_types[] = {
[MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking",
[MF_MSG_HUGE] = "huge page",
[MF_MSG_FREE_HUGE] = "free huge page",
- [MF_MSG_NON_PMD_HUGE] = "non-pmd-sized huge page",
[MF_MSG_UNMAP_FAILED] = "unmapping failed page",
[MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page",
[MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page",
@@ -1614,21 +1613,6 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
page_flags = head->flags;
- /*
- * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
- * simply disable it. In order to make it work properly, we need
- * make sure that:
- * - conversion of a pud that maps an error hugetlb into hwpoison
- * entry properly works, and
- * - other mm code walking over page table is aware of pud-aligned
- * hwpoison entries.
- */
- if (huge_page_size(page_hstate(head)) > PMD_SIZE) {
- action_result(pfn, MF_MSG_NON_PMD_HUGE, MF_IGNORED);
- res = -EBUSY;
- goto out;
- }
-
if (!hwpoison_user_mappings(p, pfn, flags, head)) {
action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);
res = -EBUSY;
--
2.25.1
On Tue, Jun 07, 2022 at 10:11:24PM +0800, Miaohe Lin wrote:
> On 2022/6/2 13:06, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <[email protected]>
> >
> > Now error handling code is prepared, so remove the blocking code and
> > enable memory error handling on 1GB hugepage.
> >
>
> I'm nervous about this change. It seems there are many code paths not awared of pud swap entry.
> I browsed some of them:
> apply_to_pud_range called from apply_to_page_range:
>
> apply_to_pud_range:
> next = pud_addr_end(addr, end);
> if (pud_none(*pud) && !create)
> continue;
> if (WARN_ON_ONCE(pud_leaf(*pud)))
> return -EINVAL;
> if (!pud_none(*pud) && WARN_ON_ONCE(pud_bad(*pud))) {
> if (!create)
> continue;
> pud_clear_bad(pud);
> }
> err = apply_to_pmd_range(mm, pud, addr, next,
> fn, data, create, mask);
>
> For !pud_present case, it will mostly reach apply_to_pmd_range and call pmd_offset on it. And invalid
> pointer will be de-referenced.
apply_to_pmd_range() has BUG_ON(pud_huge(*pud)) and apply_to_pte_range() has
BUG_ON(pmd_huge(*pmd)), so this page table walking code seems to not expect
to handle pmd/pud level mapping.
>
> Another example might be copy_pud_range and so on. So I think it might not be prepared to enable the
> 1GB hugepage or all of these places should be fixed?
I think that most of page table walker for user address space should first
check is_vm_hugetlb_page() and call hugetlb specific walking code for vma
with VM_HUGETLB.
copy_page_range() is a good example. It calls copy_hugetlb_page_range()
for vma with VM_HUGETLB and the function should support hwpoison entry.
But I feel that I need testing for confirmation.
And I'm not sure that all other are prepared for non-present pud-mapping,
so I'll need somehow code inspection and testing for each.
Thanks,
Naoya Horiguchi
On Wed, Jun 08, 2022 at 08:57:24PM +0800, Miaohe Lin wrote:
...
> >
> > I think that most of page table walker for user address space should first
> > check is_vm_hugetlb_page() and call hugetlb specific walking code for vma
> > with VM_HUGETLB.
> > copy_page_range() is a good example. It calls copy_hugetlb_page_range()
> > for vma with VM_HUGETLB and the function should support hwpoison entry.
> > But I feel that I need testing for confirmation.
>
> Sorry, I missed it should be called from hugetlb variants.
>
> >
> > And I'm not sure that all other are prepared for non-present pud-mapping,
> > so I'll need somehow code inspection and testing for each.
>
> I browsed the code again, there still might be some problematic code paths:
>
> 1.For follow_pud_mask, !pud_present will mostly reach follow_pmd_mask(). This can be
> called for hugetlb page. (Note gup_pud_range is fixed at 15494520b776 ("mm: fix gup_pud_range"))
>
> 2.Even for huge_pte_alloc, pud_offset will be called in pud_alloc. So pudp will be an invalid pointer.
> And it will be de-referenced later.
Yes, these paths need to support non-present pud entry, so I'll update/add
the patches. It seems that I did the similar work for pmd few years ago
(cbef8478bee5 ("mm/hugetlb: pmd_huge() returns true for non-present hugepage").
Thanks,
Naoya Horiguchi