logd: propagate ::log status

Add a return value for the ::log() methods, this allows
us to optimize the wakeup for the readers to only occur
when the log message is actually placed.

This is for a future where we may dedupe identical log
messages, filter out log messages, and certainly if we
filter the messages out with an internal logd check of
__android_log_is_loggable().

Change-Id: I763b2a7c29502ab7fa0a5d5022c7b60244fcfde4
diff --git a/logd/LogAudit.cpp b/logd/LogAudit.cpp
index 90370e9..caae54b 100644
--- a/logd/LogAudit.cpp
+++ b/logd/LogAudit.cpp
@@ -155,12 +155,14 @@
         event->length = htole32(l);
         memcpy(event->data, str, l);
 
-        logbuf->log(LOG_ID_EVENTS, now, uid, pid, tid,
-                    reinterpret_cast<char *>(event),
-                    (n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX);
+        rc = logbuf->log(LOG_ID_EVENTS, now, uid, pid, tid,
+                         reinterpret_cast<char *>(event),
+                         (n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX);
         free(event);
 
-        notify = true;
+        if (rc >= 0) {
+            notify = true;
+        }
     }
 
     // log to main
@@ -197,17 +199,22 @@
         strncpy(newstr + 1 + l, str, estr - str);
         strcpy(newstr + 1 + l + (estr - str), ecomm);
 
-        logbuf->log(LOG_ID_MAIN, now, uid, pid, tid, newstr,
-                    (n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX);
+        rc = logbuf->log(LOG_ID_MAIN, now, uid, pid, tid, newstr,
+                         (n <= USHRT_MAX) ? (unsigned short) n : USHRT_MAX);
         free(newstr);
 
-        notify = true;
+        if (rc >= 0) {
+            notify = true;
+        }
     }
 
     free(str);
 
     if (notify) {
         reader->notifyNewLog();
+        if (rc < 0) {
+            rc = n;
+        }
     }
 
     return rc;
@@ -216,7 +223,7 @@
 int LogAudit::log(char *buf) {
     char *audit = strstr(buf, " audit(");
     if (!audit) {
-        return 0;
+        return -EXDEV;
     }
 
     *audit = '\0';