Introduce loop_read_exact helper

Usually when using loop_read(), we want to read the full buffer.
Add a helper that mirrors loop_write(), and returns 0 when full buffer
was read, and an error otherwise.

Use -ENODATA for the short read, to distinguish it from a read error.

1 files changed, 3 insertions, 7 deletions

diff --git a/src/core/automount.c b/src/core/automount.c
index 0539fbbc41..cec90cbb31 100644
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -725,7 +725,6 @@ static bool automount_check_gc(Unit *u) {
 static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, void *userdata) {
         union autofs_v5_packet_union packet;
         Automount *a = AUTOMOUNT(userdata);
-        ssize_t l;
         int r;
 
         assert(a);
@@ -736,12 +735,9 @@ static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, vo
                 goto fail;
         }
 
-        l = loop_read(a->pipe_fd, &packet, sizeof(packet), true);
-        if (l != sizeof(packet)) {
-                if (l < 0)
-                        log_unit_error_errno(UNIT(a)->id, l, "Invalid read from pipe: %m");
-                else
-                        log_unit_error(UNIT(a)->id, "Invalid read from pipe: short read");
+        r = loop_read_exact(a->pipe_fd, &packet, sizeof(packet), true);
+        if (r < 0) {
+                log_unit_error_errno(UNIT(a)->id, r, "Invalid read from pipe: %m");
                 goto fail;
         }