• Miklos Szeredi's avatar
    ovl: check lower existence when removing · 2aff4534
    Miklos Szeredi authored
    Currently ovl_lookup() checks existence of lower file even if there's a
    non-directory on upper (which is always opaque).  This is done so that
    remove can decide whether a whiteout is needed or not.
    
    It would be better to defer this check to unlink, since most of the time
    the gathered information about opaqueness will be unused.
    
    This adds a helper ovl_lower_positive() that checks if there's anything on
    the lower layer(s).
    
    The following patches also introduce changes to how the "opaque" attribute
    is updated on directories: this attribute is added when the directory is
    creted or moved over a whiteout or object covering something on the lower
    layer.  However following changes will allow the attribute to remain on the
    directory after being moved, even if the new location doesn't cover
    anything.  Because of this, we need to check lower layers even for opaque
    directories, so that whiteout is only created when necessary.
    
    This function will later be also used to decide about marking a directory
    opaque, so deal with negative dentries as well.  When dealing with
    negative, it's enough to check for being a whiteout
    
    If the dentry is positive but not upper then it also obviously needs
    whiteout/opaque.
    Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
    2aff4534
overlayfs.h 7.51 KB