Journal fsize

Fixed journal file size / limit arithmetics when the file size was larger than the imposed limits. Added unit tests for overfill / fillup and file size checks.

src/knot/server/journal.c

@@ -547,7 +547,11 @@ int journal_write_in(journal_t *j, journal_node_t **rn, uint64_t id, size_t len)
(unsigned long long)id, j->qtail, len, j->fsize);
/* Calculate remaining bytes to reach file size limit. */
-	size_t fs_remaining = j->fslimit - j->fsize;
+	size_t fs_remaining = 0;
+	if (j->fsize < j->fslimit) {
+		fs_remaining = j->fslimit - j->fsize;
+	}
+
int seek_ret = 0;
/* Increase free segment if on the end of file. */