• Al Viro's avatar
    Fix the regression created by "set S_DEAD on unlink()..." commit · d83c49f3
    Al Viro authored
    1) i_flags simply doesn't work for mount/unlink race prevention;
    we may have many links to file and rm on one of those obviously
    shouldn't prevent bind on top of another later on.  To fix it
    right way we need to mark _dentry_ as unsuitable for mounting
    upon; new flag (DCACHE_CANT_MOUNT) is protected by d_flags and
    i_mutex on the inode in question.  Set it (with dont_mount(dentry))
    in unlink/rmdir/etc., check (with cant_mount(dentry)) in places
    in namespace.c that used to check for S_DEAD.  Setting S_DEAD
    is still needed in places where we used to set it (for directories
    getting killed), since we rely on it for readdir/rmdir race
    prevention.
    
    2) rename()/mount() protection has another bogosity - we unhash
    the target before we'd checked that it's not a mountpoint.  Fixed.
    
    3) ancient bogosity in pivot_root() - we locked i_mutex on the
    right directory, but checked S_DEAD on the different (and wrong)
    one.  Noticed and fixed.
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    d83c49f3
inode.c 17.7 KB