ext4: don't enable DAX on new encrypted files

Summary

In the Linux kernel, the following vulnerability has been resolved: ext4: don't enable DAX on new encrypted files Currently, when a new encrypted regular file is created, the call to ext4_set_inode_flags(inode, init=true) in __ext4_new_inode() is made before EXT4_INODE_ENCRYPT is set. As a result, it can set S_DAX if the filesystem is mounted with "-o dax=always". EXT4_INODE_ENCRYPT then actually gets set a bit later in __ext4_new_inode(), when it calls fscrypt_set_context() which calls ext4_set_context(). ext4_set_context() sets EXT4_INODE_ENCRYPT and calls ext4_set_inode_flags(inode, init=false) to set S_ENCRYPTED too. This was intended to clear S_DAX as well. However, this was broken by commit 043546e46dc7 ("fs/ext4: Only change S_DAX on inode load"). This causes data written to the file to bypass encryption, also causing xfstests failures such as generic/548 (when "-o dax=always" is used). Fix this by simplifying the flow by making __ext4_new_inode() set EXT4_INODE_ENCRYPT earlier. This makes it take effect in ext4_set_inode_flags(inode, init=true), making S_DAX never be set. Similarly, make EXT4_STATE_MAY_INLINE_DATA never be set in the first place on new encrypted inodes. Then it doesn't need to be cleared. As a result of these simplifications, ext4_set_context() no longer needs to change inode flags or state when 'handle != NULL'. Remove that too.