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
......@@ -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 */
......
......@@ -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))
return VM_FAULT_SIGBUS; /* mapping truncation does this. */
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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