"Don't fear the fsync()"

For files which are vital to boot

1. Avoid opening any window where power loss will zero them out or worse.
   I know app developers all coded to the ext3 implementation, but
   the only formal documentation we have says we're broken if we actually
   rely on it.  E.g.

   * `man mount`, search for `auto_da_alloc`.
   * http://www.linux-mtd.infradead.org/faq/ubifs.html#L_atomic_change
   * https://thunk.org/tytso/blog/2009/03/15/dont-fear-the-fsync/

2. If we tell the kernel we're interested in writing them to disk, it will
   tell us if that fails.  So at minimum, this means we play our part in
   notifying the user about errors.

I refactored error-handling in `udevadm-hwdb` a little.  It turns out I did
exactly the same as had already been done in the `systemd-hwdb` version,
i.e. commit d702dcd.

1 files changed, 10 insertions, 4 deletions

diff --git a/src/boot/bootctl.c b/src/boot/bootctl.c
index 233bc80292..85f3b42c48 100644
--- a/src/boot/bootctl.c
+++ b/src/boot/bootctl.c
@@ -539,12 +539,18 @@ static int copy_file_with_version_check(const char *from, const char *to, bool f
 
         r = copy_bytes(fd_from, fd_to, (uint64_t) -1, COPY_REFLINK);
         if (r < 0) {
-                unlink(t);
-                return log_error_errno(errno, "Failed to copy data from \"%s\" to \"%s\": %m", from, t);
+                (void) unlink(t);
+                return log_error_errno(r, "Failed to copy data from \"%s\" to \"%s\": %m", from, t);
         }
 
         (void) copy_times(fd_from, fd_to);
 
+        r = fsync(fd_to);
+        if (r < 0) {
+                (void) unlink_noerrno(t);
+                return log_error_errno(errno, "Failed to copy data from \"%s\" to \"%s\": %m", from, t);
+        }
+
         r = renameat(AT_FDCWD, t, AT_FDCWD, to);
         if (r < 0) {
                 (void) unlink_noerrno(t);
@@ -912,7 +918,7 @@ static int install_loader_config(const char *esp_path) {
 
         r = sd_id128_get_machine(&machine_id);
         if (r < 0)
-                return log_error_errno(r, "Failed to get machine did: %m");
+                return log_error_errno(r, "Failed to get machine id: %m");
 
         p = strjoina(esp_path, "/loader/loader.conf");
 
@@ -932,7 +938,7 @@ static int install_loader_config(const char *esp_path) {
         fprintf(f, "#timeout 3\n");
         fprintf(f, "default %s-*\n", sd_id128_to_string(machine_id, machine_string));
 
-        r = fflush_and_check(f);
+        r = fflush_sync_and_check(f);
         if (r < 0)
                 return log_error_errno(r, "Failed to write \"%s\": %m", p);