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Encode huge page size for VM_FAULT_HWPOISON errors

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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: Andi Kleen <ak@linux.intel.com>
This commit is contained in:
Andi Kleen 2010-10-06 21:45:00 +02:00
parent 6f39ce056a
commit aa50d3a7aa
4 changed files with 22 additions and 5 deletions
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6
include/linux/hugetlb.h
View file

@ -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 */

12
include/linux/mm.h
View file

@ -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.

6
mm/hugetlb.c
View file

@ -2589,7 +2589,8 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
* 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));

3
mm/memory.c
View file

@ -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();
}