From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: [PATCH 10/11] dax: Ensure that zero pages are removed from other processes Date: Tue, 4 Aug 2015 15:58:04 -0400 Message-ID: <1438718285-21168-11-git-send-email-matthew.r.wilcox@intel.com> References: <1438718285-21168-1-git-send-email-matthew.r.wilcox@intel.com> Cc: Matthew Wilcox To: Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Return-path: In-Reply-To: <1438718285-21168-1-git-send-email-matthew.r.wilcox@intel.com> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org From: Matthew Wilcox 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 Signed-off-by: Matthew Wilcox --- 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org