• Amir Goldstein's avatar
    ovl: persistent inode numbers for upper hardlinks · 6371afaf
    Amir Goldstein authored
    
    [ Upstream commit 5b6c9053 ]
    
    An upper type non directory dentry that is a copy up target
    should have a reference to its lower copy up origin.
    
    There are three ways for an upper type dentry to be instantiated:
    1. A lower type dentry that is being copied up
    2. An entry that is found in upper dir by ovl_lookup()
    3. A negative dentry is hardlinked to an upper type dentry
    
    In the first case, the lower reference is set before copy up.
    In the second case, the lower reference is found by ovl_lookup().
    In the last case of hardlinked upper dentry, it is not easy to
    update the lower reference of the negative dentry.  Instead,
    drop the newly hardlinked negative dentry from dcache and let
    the next access call ovl_lookup() to find its lower reference.
    
    This makes sure that the inode number reported by stat(2) after
    the hardlink is created is the same inode number that will be
    reported by stat(2) after mount cycle, which is the inode number
    of the lower copy up origin of the hardlink source.
    
    NOTE that this does not fix breaking of lower hardlinks on copy
    up, but only fixes the case of lower nlink == 1, whose upper copy
    up inode is hardlinked in upper dir.
    Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
    Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: default avatarSasha Levin <alexander.levin@microsoft.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    6371afaf