From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
If the first access to a huge page was a store, there would be no existing
zero pmd in this process's page tables. There could be a zero pmd in
another process's page tables, if it had done a load. We can detect this
case by noticing that the buffer_head returned from the filesystem is
New, and ensure that other processes mapping this huge page have their
page tables flushed.
Reported-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
---
fs/dax.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/dax.c b/fs/dax.c
index bf9a22b..233e61e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -568,7 +568,11 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address,
if ((pgoff | PG_PMD_COLOUR) >= size)
goto fallback;
- if (is_huge_zero_pmd(*pmd))
+ /*
+ * If we allocated new storage, make sure no process has any
+ * zero pages covering this hole
+ */
+ if (buffer_new(&bh))
unmap_mapping_range(mapping, pgoff << PAGE_SHIFT, PMD_SIZE, 0);
if (!write && !buffer_mapped(&bh) && buffer_uptodate(&bh)) {
--
2.1.4
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