Commit 73a6ec47 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds

dax: ensure that zero pages are removed from other processes

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.
Signed-off-by: default avatarMatthew Wilcox <>
Reported-by: default avatarKirill A. Shutemov <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent d295e341
......@@ -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)) {
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