On Wed, 10 Apr 2013, Naoya Horiguchi wrote: > # I suspended Reviewed and Acked given for the previous version, because > # it has a non-minor change. If you want to restore it, please let me know. > ----- > 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(). > > 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. > > ChangeLog v5: > - improve comment and description. > > ChangeLog v4: > - move is_swap_page() to right place. > > ChangeLog v3: > - add comment about using is_swap_pte() > > Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Stable for 2.6.34+? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>