[PATCH v2 2/6] unshare: Add waitchild helper

[Sean Anderson <seanga2@gmail.com>]

This refactors out the waitpid() logic into a function which will be
reused for the upcoming patches.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
---

Changes in v2:
- Add some documentation for waitchild

 sys-utils/unshare.c | 37 +++++++++++++++++++++++++------------
 1 file changed, 25 insertions(+), 12 deletions(-)

diff --git a/sys-utils/unshare.c b/sys-utils/unshare.c
index 3f8287799..62fa66067 100644
--- a/sys-utils/unshare.c
+++ b/sys-utils/unshare.c
@@ -226,6 +226,30 @@ static void settime(time_t offset, clockid_t clk_id)
 	close(fd);
 }
 
+/**
+ * waitchild() - Wait for a process to exit successfully
+ * @pid: PID of the process to wait for
+ *
+ * Wait for a process to exit successfully. If it exits with a non-zero return
+ * code, then exit() with the same status.
+ */
+static void waitchild(int pid)
+{
+	int rc, status;
+
+	do {
+		rc = waitpid(pid, &status, 0);
+		if (rc < 0) {
+			if (errno == EINTR)
+				continue;
+			err(EXIT_FAILURE, _("waitpid failed"));
+		}
+		if (WIFEXITED(status) &&
+		    WEXITSTATUS(status) != EXIT_SUCCESS)
+			exit(WEXITSTATUS(status));
+	} while (rc < 0);
+}
+
 static void bind_ns_files_from_child(pid_t *child, int fds[2])
 {
 	char ch;
@@ -580,7 +604,6 @@ int main(int argc, char *argv[])
 	if (npersists && (pid || !forkit)) {
 		/* run in parent */
 		if (pid_bind && (unshare_flags & CLONE_NEWNS)) {
-			int rc;
 			char ch = PIPE_SYNC_BYTE;
 
 			/* signal child we are ready */
@@ -589,17 +612,7 @@ int main(int argc, char *argv[])
 			fds[1] = -1;
 
 			/* wait for bind_ns_files_from_child() */
-			do {
-				rc = waitpid(pid_bind, &status, 0);
-				if (rc < 0) {
-					if (errno == EINTR)
-						continue;
-					err(EXIT_FAILURE, _("waitpid failed"));
-				}
-				if (WIFEXITED(status) &&
-				    WEXITSTATUS(status) != EXIT_SUCCESS)
-					return WEXITSTATUS(status);
-			} while (rc < 0);
+			waitchild(pid_bind);
 		} else
 			/* simple way, just bind */
 			bind_ns_files(getpid());
-- 
2.33.0