From 1752a17a1e6f7138892eeeb4806cd04ccb3ca1b0 Mon Sep 17 00:00:00 2001
From: Ludovic Courtès <ludo@gnu.org>
Date: Mon, 13 Jun 2016 17:52:08 +0200
Subject: utils: 'with-atomic-file-output' calls 'fdatasync'.

Suggested by Danny Milosavljevic <dannym@scratchpost.org>
at <https://lists.gnu.org/archive/html/guix-devel/2016-06/msg00456.html>.

* guix/build/syscalls.scm (fdatasync): New procedure.
* guix/utils.scm (with-atomic-file-output): Use it.  Use 'close-port'
instead of 'close'.
---
 guix/build/syscalls.scm | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'guix/build/syscalls.scm')

diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index 48ff227e10..ed0eb060d9 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -64,6 +64,7 @@
 
             processes
             mkdtemp!
+            fdatasync
             pivot-root
             fcntl-flock
 
@@ -506,6 +507,20 @@ string TMPL and return its file name.  TMPL must end with 'XXXXXX'."
                  (list err)))
         (pointer->string result)))))
 
+(define fdatasync
+  (let ((proc (syscall->procedure int "fdatasync" (list int))))
+    (lambda (port)
+      "Flush buffered output of PORT, an output file port, and then call
+fdatasync(2) on the underlying file descriptor."
+      (force-output port)
+      (let* ((fd  (fileno port))
+             (ret (proc fd))
+             (err (errno)))
+        (unless (zero? ret)
+          (throw 'system-error "fdatasync" "~S: ~A"
+                 (list fd (strerror err))
+                 (list err)))))))
+
 
 (define-record-type <file-system>
   (file-system type block-size blocks blocks-free
-- 
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