copy: optionally check for SIGINT regularly, and abort operation safely

src/basic/copy.c

@@ -86,6 +86,22 @@ static int fd_is_nonblock_pipe(int fd) {
         return FLAGS_SET(flags, O_NONBLOCK) ? FD_IS_NONBLOCKING_PIPE : FD_IS_BLOCKING_PIPE;
 }
 
+static int sigint_pending(void) {
+        sigset_t ss;
+
+        assert_se(sigemptyset(&ss) >= 0);
+        assert_se(sigaddset(&ss, SIGINT) >= 0);
+
+        if (sigtimedwait(&ss, NULL, &(struct timespec) { 0, 0 }) < 0) {
+                if (errno == EAGAIN)
+                        return false;
+
+                return -errno;
+        }
+
+        return true;
+}
+
 int copy_bytes_full(
                 int fdf, int fdt,
                 uint64_t max_bytes,
@@ -174,6 +190,14 @@ int copy_bytes_full(
                 if (max_bytes <= 0)
                         return 1; /* return > 0 if we hit the max_bytes limit */
 
+                if (FLAGS_SET(copy_flags, COPY_SIGINT)) {
+                        r = sigint_pending();
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                return -EINTR;
+                }
+
                 if (max_bytes != UINT64_MAX && m > max_bytes)
                         m = max_bytes;
 
@@ -559,6 +583,14 @@ static int fd_copy_directory(
                 if (dot_or_dot_dot(de->d_name))
                         continue;
 
+                if (FLAGS_SET(copy_flags, COPY_SIGINT)) {
+                        r = sigint_pending();
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                return -EINTR;
+                }
+
                 if (fstatat(dirfd(d), de->d_name, &buf, AT_SYMLINK_NOFOLLOW) < 0) {
                         r = -errno;
                         continue;
@@ -618,9 +650,10 @@ static int fd_copy_directory(
                 else
                         q = -EOPNOTSUPP;
 
+                if (q == -EINTR) /* Propagate SIGINT up instantly */
+                        return q;
                 if (q == -EEXIST && (copy_flags & COPY_MERGE))
                         q = 0;
-
                 if (q < 0)
                         r = q;
         }