[PATCH RESEND v6 9/9] fsdax: add exception for reflinked files

[Shiyang Ruan <ruansy.fnst@fujitsu.com>]

For reflinked files, one dax page may be associated more than once with
different fime mapping and index.  It will report warning.  Now, since
we have introduced dax-RMAP for this case and also have to keep its
functionality for other filesystems who are not support rmap, I add this
exception here.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
---
 fs/dax.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index dce6307a12eb..f5910d178695 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -352,9 +352,10 @@ static void dax_associate_entry(void *entry, struct address_space *mapping,
 	for_each_mapped_pfn(entry, pfn) {
 		struct page *page = pfn_to_page(pfn);
 
-		WARN_ON_ONCE(page->mapping);
-		page->mapping = mapping;
-		page->index = index + i++;
+		if (!page->mapping) {
+			page->mapping = mapping;
+			page->index = index + i++;
+		}
 	}
 }
 
@@ -370,9 +371,10 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
 		struct page *page = pfn_to_page(pfn);
 
 		WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
-		WARN_ON_ONCE(page->mapping && page->mapping != mapping);
-		page->mapping = NULL;
-		page->index = 0;
+		if (page->mapping == mapping) {
+			page->mapping = NULL;
+			page->index = 0;
+		}
 	}
 }
 
-- 
2.32.0