Revert "Clean up redundant flags with O3"

This reverts commit 2f33b2003989856e620885eab82e80f140f05933.
new helper: file_inode(file)

[alex: trimmed down to modify f2fs and linux/fs.h]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Alejandro Martinez Ruiz <alex@nowcomputing.com>