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Commit aa50d3a7 authored by Andi Kleen's avatar Andi Kleen
Browse files

Encode huge page size for VM_FAULT_HWPOISON errors 



This fixes a problem introduced with the hugetlb hwpoison handling

The user space SIGBUS signalling wants to know the size of the hugepage
that caused a HWPOISON fault.

Unfortunately the architecture page fault handlers do not have easy
access to the struct page.

Pass the information out in the fault error code instead.

I added a separate VM_FAULT_HWPOISON_LARGE bit for this case and encode
the hpage index in some free upper bits of the fault code. The small
page hwpoison keeps stays with the VM_FAULT_HWPOISON name to minimize
changes.

Also add code to hugetlb.h to convert that index into a page shift.

Will be used in a further patch.

Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: fengguang.wu@intel.com
Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
parent 6f39ce05

include/linux/hugetlb.h

+6 −0
Original line number Diff line number Diff line
@@ -307,6 +307,11 @@ static inline struct hstate *page_hstate(struct page *page) 
	return size_to_hstate(PAGE_SIZE << compound_order(page));

}



static inline unsigned hstate_index_to_shift(unsigned index)

{

	return hstates[index].order + PAGE_SHIFT;

}



#else

struct hstate {};

#define alloc_huge_page_node(h, nid) NULL
@@ -324,6 +329,7 @@ static inline unsigned int pages_per_huge_page(struct hstate *h) 
{

	return 1;

}

#define hstate_index_to_shift(index) 0

#endif



#endif /* _LINUX_HUGETLB_H */

include/linux/mm.h

+10 −2
Original line number Diff line number Diff line
@@ -718,12 +718,20 @@ static inline int page_mapped(struct page *page) 
#define VM_FAULT_SIGBUS	0x0002

#define VM_FAULT_MAJOR	0x0004

#define VM_FAULT_WRITE	0x0008	/* Special case for get_user_pages */

#define VM_FAULT_HWPOISON 0x0010	/* Hit poisoned page */

#define VM_FAULT_HWPOISON 0x0010	/* Hit poisoned small page */

#define VM_FAULT_HWPOISON_LARGE 0x0020  /* Hit poisoned large page. Index encoded in upper bits */



#define VM_FAULT_NOPAGE	0x0100	/* ->fault installed the pte, not return page */

#define VM_FAULT_LOCKED	0x0200	/* ->fault locked the returned page */



#define VM_FAULT_ERROR	(VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_HWPOISON)

#define VM_FAULT_HWPOISON_LARGE_MASK 0xf000 /* encodes hpage index for large hwpoison */



#define VM_FAULT_ERROR	(VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | \

			 VM_FAULT_HWPOISON_LARGE)



/* Encode hstate index for a hwpoisoned large page */

#define VM_FAULT_SET_HINDEX(x) ((x) << 12)

#define VM_FAULT_GET_HINDEX(x) (((x) >> 12) & 0xf)



/*

 * Can be called by the pagefault handler when it gets a VM_FAULT_OOM.

mm/hugetlb.c

+4 −2
Original line number Diff line number Diff line
@@ -2589,7 +2589,8 @@ retry: 
		 * So we need to block hugepage fault by PG_hwpoison bit check.

		 */

		if (unlikely(PageHWPoison(page))) {

			ret = VM_FAULT_HWPOISON;

			ret = VM_FAULT_HWPOISON | 

			      VM_FAULT_SET_HINDEX(h - hstates);

			goto backout_unlocked;

		}

		page_dup_rmap(page);
@@ -2656,7 +2657,8 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, 
			migration_entry_wait(mm, (pmd_t *)ptep, address);

			return 0;

		} else if (unlikely(is_hugetlb_entry_hwpoisoned(entry)))

			return VM_FAULT_HWPOISON;

			return VM_FAULT_HWPOISON_LARGE | 

			       VM_FAULT_SET_HINDEX(h - hstates);

	}



	ptep = huge_pte_alloc(mm, address, huge_page_size(h));

mm/memory.c

+2 −1
Original line number Diff line number Diff line
@@ -1450,7 +1450,8 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 
					if (ret & VM_FAULT_OOM)

						return i ? i : -ENOMEM;

					if (ret &

					    (VM_FAULT_HWPOISON|VM_FAULT_SIGBUS))

					    (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE|

					     VM_FAULT_SIGBUS))

						return i ? i : -EFAULT;

					BUG();

				}