From 2bc9c84327839e73e2b47e71bdc9f111dd2fc425 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Mon, 22 Jun 2015 15:54:55 +0200
Subject: [PATCH] Use posix_fallocate to create /nix/var/nix/db/reserved

---
 src/libstore/local-store.cc | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 1dcd7228f..074c3394f 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -289,7 +289,17 @@ LocalStore::LocalStore(bool reserveSpace)
             struct stat st;
             if (stat(reservedPath.c_str(), &st) == -1 ||
                 st.st_size != settings.reservedSize)
-                writeFile(reservedPath, string(settings.reservedSize, 'X'));
+            {
+                AutoCloseFD fd = open(reservedPath.c_str(), O_WRONLY | O_CREAT, 0600);
+                int res = -1;
+#if HAVE_POSIX_FALLOCATE
+                res = posix_fallocate(fd, 0, settings.reservedSize);
+#endif
+                if (res == -1) {
+                    writeFull(fd, string(settings.reservedSize, 'X'));
+                    ftruncate(fd, settings.reservedSize);
+                }
+            }
         }
         else
             deletePath(reservedPath);