Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 3359b54c authored by Seth, Rohit's avatar Seth, Rohit Committed by Linus Torvalds
Browse files

[PATCH] Handle spurious page fault for hugetlb region 



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: default avatarRohit 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: default avatarLinus Torvalds <torvalds@osdl.org>
parent bb7e257e

include/linux/hugetlb.h

+13 −0
Original line number Original line Diff line number Diff line
@@ -155,11 +155,24 @@ static inline void set_file_hugepages(struct file *file) 
{

{

	file->f_op = &hugetlbfs_file_operations;

	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 */

#else /* !CONFIG_HUGETLBFS */





#define is_file_hugepages(file)		0

#define is_file_hugepages(file)		0

#define set_file_hugepages(file)	BUG()

#define set_file_hugepages(file)	BUG()

#define hugetlb_zero_setup(size)	ERR_PTR(-ENOSYS)

#define hugetlb_zero_setup(size)	ERR_PTR(-ENOSYS)

#define valid_hugetlb_file_off(vma, address) 	0





#endif /* !CONFIG_HUGETLBFS */

#endif /* !CONFIG_HUGETLBFS */

mm/memory.c

+12 −2
Original line number Original line 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);

	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. */

			return VM_FAULT_SIGBUS;	/* mapping truncation does this. */

	}





	/*

	/*

	 * We need the page table lock to synchronize with kswapd

	 * We need the page table lock to synchronize with kswapd