Linus,
[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).
Thanks,
-rohit
Signed-off-by: Rohit Seth <[email protected]>
--- linux-2.6.14-rc4-git5-x86/include/linux/hugetlb.h 2005-10-18 13:14:24.879947360 -0700
+++ b/include/linux/hugetlb.h 2005-10-18 13:13:55.711381656 -0700
@@ -155,11 +155,24 @@
{
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 */
--- linux-2.6.14-rc4-git5-x86/mm/memory.c 2005-10-18 12:24:14.153647328 -0700
+++ b/mm/memory.c 2005-10-18 10:39:41.980162632 -0700
@@ -2045,8 +2045,18 @@
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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
