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authorSeth, Rohit <rohit.seth@intel.com>2005-10-18 14:15:12 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-19 13:56:27 -0700
commit3359b54c8c07338f3a863d1109b42eebccdcf379 (patch)
treef91edd52c71e57ce4b46e3875c9054666ca4e24c
parentbb7e257ef8d8ba43cab356aa1cc1b20d0106d45f (diff)
downloadop-kernel-dev-3359b54c8c07338f3a863d1109b42eebccdcf379.zip
op-kernel-dev-3359b54c8c07338f3a863d1109b42eebccdcf379.tar.gz
[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: 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>
-rw-r--r--include/linux/hugetlb.h13
-rw-r--r--mm/memory.c14
2 files changed, 25 insertions, 2 deletions
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index e670b0d..42cb7d70 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -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 */
diff --git a/mm/memory.c b/mm/memory.c
index ae8161f..8c88b97 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -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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