From 84c4e5e675408b6fb7d74eec7da9a4a5698b50af Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 8 Sep 2015 14:59:17 -0700 Subject: dax: improve comment about truncate race Jan Kara pointed out I should be more explicit here about the perils of racing against truncate. The comment is mostly the same as for the PTE case. Signed-off-by: Matthew Wilcox Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/dax.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index 2deed64b7eea..c694117a7062 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -553,7 +553,12 @@ int __dax_pmd_fault(struct vm_area_struct *vma, unsigned long address, if (!buffer_size_valid(&bh) || bh.b_size < PMD_SIZE) goto fallback; - /* Guard against a race with truncate */ + /* + * If a truncate happened while we were allocating blocks, we may + * leave blocks allocated to the file that are beyond EOF. We can't + * take i_mutex here, so just leave them hanging; they'll be freed + * when the file is deleted. + */ size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; if (pgoff >= size) { result = VM_FAULT_SIGBUS; -- cgit v1.2.3