remove_file: don't call rmdir if remove_file return failure

When deleting a directory, the directory should not be removed if the
file in the subdirectory fails to be deleted.

Background information:

When I tested the kernel using LTP (linux-test-project).I found the
mv command have some issue. The LTP test case use the mv command to
move the directory t1 in the cgroup file system to the /tmp directory.
becase files in the cgroup file system are not allowed to be removed.
so the mv reported "Permission denied", but I used the ls command to
view the results and found that the directory t1 had been removed
from the cgroup file system. For the same test case, I used the mv
tool in the GNU coreutils, and the directory t1 will not be removed.

the following testcase use busybox mv:

/ # mount -t cgroup -o cpu cgroup /cpu
/ # cd /cpu
/cpu # mkdir -p t1
/cpu # ls
cgroup.clone_children  cpu.cfs_period_us  cpu.stat  t1
cgroup.procs           cpu.cfs_quota_us   notify_on_release  tasks
cgroup.sane_behavior   cpu.shares         release_agent
/cpu # mv t1 /tmp
mv: can't remove 't1/cgroup.procs': Operation not permitted
mv: can't remove 't1/cpu.cfs_period_us': Operation not permitted
mv: can't remove 't1/cpu.stat': Operation not permitted
mv: can't remove 't1/cpu.shares': Operation not permitted
mv: can't remove 't1/cpu.cfs_quota_us': Operation not permitted
mv: can't remove 't1/tasks': Operation not permitted
mv: can't remove 't1/notify_on_release': Operation not permitted
mv: can't remove 't1/cgroup.clone_children': Operation not permitted
/cpu # ls
cgroup.clone_children  cpu.cfs_period_us  cpu.stat  cgroup.procs
cpu.cfs_quota_us       notify_on_release  tasks   cgroup.sane_behavior
cpu.shares             release_agent
/cpu #

This patch fixed it, don't call rmdir if remove_file return failure,
and under certain file systems, the mv could work normally.

Signed-off-by: Chen Yu <yu.chen3@zte.com.cn>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/remove_file.c

@@ -73,7 +73,7 @@ int FAST_FUNC remove_file(const char *path, int flags)
 				return status;
 		}
 
-		if (rmdir(path) < 0) {
+		if (status == 0 && rmdir(path) < 0) {
 			bb_perror_msg("can't remove '%s'", path);
 			return -1;
 		}