[PATCH V4 2/8] fs/ext4: Disallow verity if inode is DAX

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

Verity and DAX are incompatible.  Changing the DAX mode due to a verity
flag change is wrong without a corresponding address_space_operations
update.

Make the 2 options mutually exclusive by returning an error if DAX was
set first.

(Setting DAX is already disabled if Verity is set first.)

Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>

---
Changes from V2:
	Remove Section title 'Verity and DAX'

Changes:
	remove WARN_ON_ONCE
	Add documentation for DAX/Verity exclusivity
---
 Documentation/filesystems/ext4/verity.rst | 3 +++
 fs/ext4/verity.c                          | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
index 3e4c0ee0e068..e99ff3fd09f7 100644
--- a/Documentation/filesystems/ext4/verity.rst
+++ b/Documentation/filesystems/ext4/verity.rst
@@ -39,3 +39,6 @@ is encrypted as well as the data itself.
 
 Verity files cannot have blocks allocated past the end of the verity
 metadata.
+
+Verity and DAX are not compatible and attempts to set both of these flags
+on a file will fail.
diff --git a/fs/ext4/verity.c b/fs/ext4/verity.c
index dc5ec724d889..f05a09fb2ae4 100644
--- a/fs/ext4/verity.c
+++ b/fs/ext4/verity.c
@@ -113,6 +113,9 @@ static int ext4_begin_enable_verity(struct file *filp)
 	handle_t *handle;
 	int err;
 
+	if (IS_DAX(inode))
+		return -EINVAL;
+
 	if (ext4_verity_in_progress(inode))
 		return -EBUSY;
 
-- 
2.25.1