fs/ext4: Disallow verity if inode is DAX

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@suse.cz>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20200528150003.828793-3-ira.weiny@intel.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/Documentation/filesystems/ext4/verity.rst b/Documentation/filesystems/ext4/verity.rst
index 3e4c0ee..e99ff3f 100644 (file)
--- 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 dc5ec72..f05a09f 100644 (file)
--- 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;