iomap: share iomap_unshare_iter predicate code with fsdax

The predicate code that iomap_unshare_iter uses to decide if it's really
needs to unshare a file range mapping should be shared with the fsdax
version, because right now they're opencoded and inconsistent.

Note that we simplify the predicate logic a bit -- we no longer allow
unsharing of inline data mappings, but there aren't any filesystems that
allow shared inline data currently.

This is a fix in the sense that it should have been ported to fsdax.

Fixes: b53fdb215d13 ("iomap: improve shared block detection in iomap_unshare_iter")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/172796813294.1131942.15762084021076932620.stgit@frogsfrogsfrogs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/dax.c b/fs/dax.c
index c62acd2812f8..5064eefb1c1e 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1268,8 +1268,7 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
 	s64 ret = 0;
 	void *daddr = NULL, *saddr = NULL;
 
-	/* don't bother with blocks that are not shared to start with */
-	if (!(iomap->flags & IOMAP_F_SHARED))
+	if (!iomap_want_unshare_iter(iter))
 		return length;
 
 	id = dax_read_lock();