libfs.c: new helper - next_positive()

Return nth positive child after given or NULL if there's
less than n left.  dcache_readdir() and dcache_dir_lseek()
switched to it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 47 insertions, 30 deletions

diff --git a/fs/libfs.c b/fs/libfs.c