[PATCH v3 06/25] fsdax: Validate DAX layouts broken before truncate

[Dan Williams <dan.j.williams@intel.com>]

Now that iput_final() arranges for dax_break_layouts(), all
truncate_inode_pages() paths in the kernel ensure that no DAX pages
hosted by that inode are in use. Add warnings to assert the new entry
state transitions.

Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 fs/dax.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index e3deb60a792f..1d4f0072e58d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -401,13 +401,15 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
 	for_each_mapped_pfn(entry, pfn) {
 		struct page *page = pfn_to_page(pfn);
 
-		WARN_ON_ONCE(trunc && !dax_page_idle(page));
 		if (dax_mapping_is_cow(page->mapping)) {
 			/* keep the CoW flag if this page is still shared */
 			if (page->index-- > 0)
 				continue;
-		} else
+		} else {
+			WARN_ON_ONCE(trunc && !dax_is_zapped(entry));
+			WARN_ON_ONCE(trunc && !dax_page_idle(page));
 			WARN_ON_ONCE(page->mapping && page->mapping != mapping);
+		}
 		page->mapping = NULL;
 		page->index = 0;
 	}