From 73a6ec47f68787df1b41869def52915da2f4a6b7 Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 8 Sep 2015 14:59:37 -0700 Subject: [PATCH] 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: Matthew Wilcox Reported-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/dax.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index d778e5f1a01c..74838c43be91 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)) { -- 2.20.1