[PATCH] Handle spurious page fault for hugetlb region (3359b54c) · Commits · 戴 / test

The hugetlb pages are currently pre-faulted. At the time of mmap of hugepages, we populate the new PTEs. It is possible that HW has already cached some of the unused PTEs internally. These stale entries never get a chance to be purged in existing control flow. This patch extends the check in page fault code for hugepages. Check if a faulted address falls with in size for the hugetlb file backing it. We return VM_FAULT_MINOR for these cases (assuming that the arch specific page-faulting code purges the stale entry for the archs that need it). Signed-off-by:

Rohit Seth <rohit.seth@intel.com> [ This is apparently arguably an ia64 port bug. But the code won't hurt, and for now it fixes a real problem on some ia64 machines ] Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

include/linux/hugetlb.h

+13 −0

Original line number	Diff line number	Diff line
		@@ -155,11 +155,24 @@ static inline void set_file_hugepages(struct file *file)
		{
		file->f_op = &hugetlbfs_file_operations;
		}

		static inline int valid_hugetlb_file_off(struct vm_area_struct *vma,
		unsigned long address)
		{
		struct inode *inode = vma->vm_file->f_dentry->d_inode;
		loff_t file_off = address - vma->vm_start;

		file_off += (vma->vm_pgoff << PAGE_SHIFT);

		return (file_off < inode->i_size);
		}

		#else /* !CONFIG_HUGETLBFS */

		#define is_file_hugepages(file) 0
		#define set_file_hugepages(file) BUG()
		#define hugetlb_zero_setup(size) ERR_PTR(-ENOSYS)
		#define valid_hugetlb_file_off(vma, address) 0

		#endif /* !CONFIG_HUGETLBFS */

mm/memory.c

+12 −2

Original line number	Diff line number	Diff line
		@@ -2045,8 +2045,18 @@ int __handle_mm_fault(struct mm_struct mm, struct vm_area_struct vma,

		inc_page_state(pgfault);

		if (is_vm_hugetlb_page(vma))
		if (unlikely(is_vm_hugetlb_page(vma))) {
		if (valid_hugetlb_file_off(vma, address))
		/* We get here only if there was a stale(zero) TLB entry
		* (because of HW prefetching).
		* Low-level arch code (if needed) should have already
		* purged the stale entry as part of this fault handling.
		* Here we just return.
		*/
		return VM_FAULT_MINOR;
		else
		return VM_FAULT_SIGBUS; /* mapping truncation does this. */
		}

		/*
		* We need the page table lock to synchronize with kswapd

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