05/08: Use posix_fallocate to create /nix/var/nix/db/reserved

[Ludovic Court�s]

civodul pushed a commit to branch nix
in repository guix.

commit 5e0a9ae2e25a1016389f4893a6ed6682aadcf51d
Author: Eelco Dolstra <eelco.dols...@logicblox.com>
Date:   Mon Jun 22 15:54:55 2015 +0200

    Use posix_fallocate to create /nix/var/nix/db/reserved
---
 nix/libstore/local-store.cc |   12 +++++++++++-
 1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/nix/libstore/local-store.cc b/nix/libstore/local-store.cc
index 9d8ae71..b2c7847 100644
--- a/nix/libstore/local-store.cc
+++ b/nix/libstore/local-store.cc
@@ -288,7 +288,17 @@ 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);