Connect to plymouth and support cancellation of in progress fsck

Try to connect and send to plymouth (if running) some checked report progress,
using direct plymouth protocole.

Update message is the following:
fsckd:<num_devices>:<progress>:<string>
* num_devices corresponds to the current number of devices being checked (int)
* progress corresponds to the current minimum percentage of all devices being
  checked (float, from 0 to 100)
* string is a translated message ready to be displayed by the plymouth theme
  displaying the information above. It can be overriden by plymouth themes
  supporting i18n.

Grab in fsckd plymouth watch key Control+C, and propagate this cancel request
to systemd-fsck which will terminate fsck.

Send a message to signal to user what key we are grabbing for fsck cancel.

Message is: fsckd-cancel-msg:<string>
Where string is a translated string ready to be displayed by the plymouth theme
indicating that Control+C can be used to cancel current checks. It can be
overriden (matching only fsckd-cancel-msg prefix) for themes supporting i18n.

1 files changed, 24 insertions, 9 deletions

diff --git a/src/fsck/fsck.c b/src/fsck/fsck.c
index 9ecba99bb1..e7185342d7 100644
--- a/src/fsck/fsck.c
+++ b/src/fsck/fsck.c
@@ -132,7 +132,7 @@ static void test_files(void) {
 
 }
 
-static int process_progress(int fd, dev_t device_num) {
+static int process_progress(int fd, pid_t fsck_pid, dev_t device_num) {
         _cleanup_fclose_ FILE *f = NULL;
         usec_t last = 0;
         _cleanup_close_ int fsckd_fd = -1;
@@ -153,11 +153,13 @@ static int process_progress(int fd, dev_t device_num) {
 
         while (!feof(f)) {
                 int pass;
+                size_t buflen;
                 size_t cur, max;
-                ssize_t n;
+                ssize_t r;
                 usec_t t;
                 _cleanup_free_ char *device = NULL;
                 FsckProgress progress;
+                FsckdMessage fsckd_message;
 
                 if (fscanf(f, "%i %lu %lu %ms", &pass, &cur, &max, &device) != 4)
                         break;
@@ -175,9 +177,19 @@ static int process_progress(int fd, dev_t device_num) {
                 progress.max = max;
                 progress.pass = pass;
 
-                n = send(fsckd_fd, &progress, sizeof(FsckProgress), 0);
-                if (n < 0 || (size_t) n < sizeof(FsckProgress))
+                r = send(fsckd_fd, &progress, sizeof(FsckProgress), 0);
+                if (r < 0 || (size_t) r < sizeof(FsckProgress))
                         log_warning_errno(errno, "Cannot communicate fsck progress to fsckd: %m");
+
+                /* get fsckd requests, only read when we have coherent size data */
+                r = ioctl(fsckd_fd, FIONREAD, &buflen);
+                if (r == 0 && (size_t) buflen >= sizeof(FsckdMessage)) {
+                        r = recv(fsckd_fd, &fsckd_message, sizeof(FsckdMessage), 0);
+                        if (r > 0 && fsckd_message.cancel == 1) {
+                                log_info("Request to cancel fsck from fsckd");
+                                kill(fsck_pid, SIGTERM);
+                        }
+                }
         }
 
         return 0;
@@ -187,6 +199,7 @@ int main(int argc, char *argv[]) {
         const char *cmdline[9];
         int i = 0, r = EXIT_FAILURE, q;
         pid_t pid;
+        int progress_rc;
         siginfo_t status;
         _cleanup_udev_unref_ struct udev *udev = NULL;
         _cleanup_udev_device_unref_ struct udev_device *udev_device = NULL;
@@ -328,7 +341,7 @@ int main(int argc, char *argv[]) {
         progress_pipe[1] = safe_close(progress_pipe[1]);
 
         if (progress_pipe[0] >= 0) {
-                process_progress(progress_pipe[0], st.st_rdev);
+                progress_rc = process_progress(progress_pipe[0], pid, st.st_rdev);
                 progress_pipe[0] = -1;
         }
 
@@ -338,13 +351,14 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
-        if (status.si_code != CLD_EXITED || (status.si_status & ~1)) {
+        if (status.si_code != CLD_EXITED || (status.si_status & ~1) || progress_rc != 0) {
 
-                if (status.si_code == CLD_KILLED || status.si_code == CLD_DUMPED)
+                /* cancel will kill fsck (but process_progress returns 0) */
+                if ((progress_rc != 0 && status.si_code == CLD_KILLED) || status.si_code == CLD_DUMPED)
                         log_error("fsck terminated by signal %s.", signal_to_string(status.si_status));
                 else if (status.si_code == CLD_EXITED)
                         log_error("fsck failed with error code %i.", status.si_status);
-                else
+                else if (progress_rc != 0)
                         log_error("fsck failed due to unknown reason.");
 
                 if (status.si_code == CLD_EXITED && (status.si_status & 2) && root_directory)
@@ -355,7 +369,8 @@ int main(int argc, char *argv[]) {
                         start_target(SPECIAL_EMERGENCY_TARGET);
                 else {
                         r = EXIT_SUCCESS;
-                        log_warning("Ignoring error.");
+                        if (progress_rc != 0)
+                                log_warning("Ignoring error.");
                 }
 
         } else