From 665dfe93185a1decdb422f9e5b65a7e39415f129 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 12 Dec 2017 23:21:09 +0100
Subject: [PATCH] io-util: make flush_fd() return how many bytes where flushed

This is useful so that callers know whether anything at all and how much
was flushed.

This patches through users of this functions to ensure that the return
values > 0 which may be returned now are not propagated in public APIs.

Also, users that ignore the return value are changed to do so explicitly
now.
---
 src/basic/io-util.c                                 |  9 ++++++---
 src/core/manager.c                                  |  2 +-
 src/libsystemd/sd-login/sd-login.c                  |  7 ++++++-
 src/libudev/libudev-queue.c                         | 10 +++++++++-
 src/shared/ask-password-api.c                       |  2 +-
 src/tty-ask-password-agent/tty-ask-password-agent.c |  2 +-
 6 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/src/basic/io-util.c b/src/basic/io-util.c
index 77c9bdc739..08ad42ed95 100644
--- a/src/basic/io-util.c
+++ b/src/basic/io-util.c
@@ -33,6 +33,7 @@ int flush_fd(int fd) {
                 .fd = fd,
                 .events = POLLIN,
         };
+        int count = 0;
 
         /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
          * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
@@ -52,7 +53,7 @@ int flush_fd(int fd) {
                         return -errno;
 
                 } else if (r == 0)
-                        return 0;
+                        return count;
 
                 l = read(fd, buf, sizeof(buf));
                 if (l < 0) {
@@ -61,11 +62,13 @@ int flush_fd(int fd) {
                                 continue;
 
                         if (errno == EAGAIN)
-                                return 0;
+                                return count;
 
                         return -errno;
                 } else if (l == 0)
-                        return 0;
+                        return count;
+
+                count += (int) l;
         }
 }
 
diff --git a/src/core/manager.c b/src/core/manager.c
index 15720ada24..860d58617f 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -263,7 +263,7 @@ static int manager_dispatch_ask_password_fd(sd_event_source *source,
 
         assert(m);
 
-        flush_fd(fd);
+        (void) flush_fd(fd);
 
         m->have_ask_password = have_ask_password();
         if (m->have_ask_password < 0)
diff --git a/src/libsystemd/sd-login/sd-login.c b/src/libsystemd/sd-login/sd-login.c
index e8adaa6823..69572d1a51 100644
--- a/src/libsystemd/sd-login/sd-login.c
+++ b/src/libsystemd/sd-login/sd-login.c
@@ -1061,10 +1061,15 @@ _public_ sd_login_monitor* sd_login_monitor_unref(sd_login_monitor *m) {
 }
 
 _public_ int sd_login_monitor_flush(sd_login_monitor *m) {
+        int r;
 
         assert_return(m, -EINVAL);
 
-        return flush_fd(MONITOR_TO_FD(m));
+        r = flush_fd(MONITOR_TO_FD(m));
+        if (r < 0)
+                return r;
+
+        return 0;
 }
 
 _public_ int sd_login_monitor_get_fd(sd_login_monitor *m) {
diff --git a/src/libudev/libudev-queue.c b/src/libudev/libudev-queue.c
index b941afb773..85ceb263a3 100644
--- a/src/libudev/libudev-queue.c
+++ b/src/libudev/libudev-queue.c
@@ -268,8 +268,16 @@ _public_ int udev_queue_get_fd(struct udev_queue *udev_queue) {
  * Returns: the result of clearing the watch for queue changes.
  */
 _public_ int udev_queue_flush(struct udev_queue *udev_queue) {
+        int r;
+
+        assert(udev_queue);
+
         if (udev_queue->fd < 0)
                 return -EINVAL;
 
-        return flush_fd(udev_queue->fd);
+        r = flush_fd(udev_queue->fd);
+        if (r < 0)
+                return r;
+
+        return 0;
 }
diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index 346d8c9d24..99d6a9b143 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -316,7 +316,7 @@ int ask_password_tty(
                 }
 
                 if (notify >= 0 && pollfd[POLL_INOTIFY].revents != 0)
-                        flush_fd(notify);
+                        (void) flush_fd(notify);
 
                 if (pollfd[POLL_TTY].revents == 0)
                         continue;
diff --git a/src/tty-ask-password-agent/tty-ask-password-agent.c b/src/tty-ask-password-agent/tty-ask-password-agent.c
index 6e9c10aeb0..d2648ead93 100644
--- a/src/tty-ask-password-agent/tty-ask-password-agent.c
+++ b/src/tty-ask-password-agent/tty-ask-password-agent.c
@@ -159,7 +159,7 @@ static int ask_password_plymouth(
                 }
 
                 if (notify >= 0 && pollfd[POLL_INOTIFY].revents != 0)
-                        flush_fd(notify);
+                        (void) flush_fd(notify);
 
                 if (pollfd[POLL_SOCKET].revents == 0)
                         continue;