From 10b6d0129d062f4d5d8a7611023c3f8cc43f1eab Mon Sep 17 00:00:00 2001
From: Zac Medico <zmedico@gentoo.org>
Date: Thu, 25 Oct 2012 01:35:31 -0700
Subject: Add FEATURES=merge-sync, for bug #439584.

---
 cnf/make.globals             |  2 +-
 man/make.conf.5              |  5 +++++
 pym/portage/const.py         |  1 +
 pym/portage/dbapi/vartree.py | 41 ++++++++++++++++++++++++++++++++++++++++-
 4 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/cnf/make.globals b/cnf/make.globals
index e53f1867f..47ee787c6 100644
--- a/cnf/make.globals
+++ b/cnf/make.globals
@@ -53,7 +53,7 @@ FETCHCOMMAND_SFTP="bash -c \"x=\\\${2#sftp://} ; host=\\\${x%%/*} ; port=\\\${ho
 # Default user options
 FEATURES="assume-digests binpkg-logs
           config-protect-if-modified distlocks ebuild-locks
-          fixlafiles news parallel-fetch protect-owned
+          fixlafiles merge-sync news parallel-fetch protect-owned
           sandbox sfperms strict unknown-features-warn unmerge-logs
           unmerge-orphans userfetch"
 
diff --git a/man/make.conf.5 b/man/make.conf.5
index 4c86d38e6..9152ab295 100644
--- a/man/make.conf.5
+++ b/man/make.conf.5
@@ -361,6 +361,11 @@ Do \fBNOT\fR use \fIlmirror\fR for clients that need to override \fBRESTRICT\fR
 when fetching from a local mirror, but instead use a "local" mirror setting
 in \fI/etc/portage/mirrors\fR, as described in \fBportage\fR(5).
 .TP
+.B merge\-sync
+After a package is merged or unmerged, sync relevant files to
+disk in order to avoid data\-loss in the event of a power failure.
+This feature is enabled by default.
+.TP
 .B metadata\-transfer
 Automatically perform a metadata transfer when `emerge \-\-sync` is run.
 In versions of portage >=2.1.5, this feature is disabled by
diff --git a/pym/portage/const.py b/pym/portage/const.py
index 3242861cf..8c5bbf308 100644
--- a/pym/portage/const.py
+++ b/pym/portage/const.py
@@ -96,6 +96,7 @@ SUPPORTED_FEATURES       = frozenset([
                            "downgrade-backup", "ebuild-locks", "fakeroot",
                            "fail-clean", "force-mirror", "force-prefix", "getbinpkg",
                            "installsources", "keeptemp", "keepwork", "fixlafiles", "lmirror",
+                           "merge-sync",
                            "metadata-transfer", "mirror", "multilib-strict", "news",
                            "noauto", "noclean", "nodoc", "noinfo", "noman",
                            "nostrip", "notitles", "parallel-fetch", "parallel-install",
diff --git a/pym/portage/dbapi/vartree.py b/pym/portage/dbapi/vartree.py
index cb7b39b02..edc477a09 100644
--- a/pym/portage/dbapi/vartree.py
+++ b/pym/portage/dbapi/vartree.py
@@ -30,6 +30,7 @@ portage.proxy.lazyimport.lazyimport(globals(),
 	'portage.util.env_update:env_update',
 	'portage.util.listdir:dircache,listdir',
 	'portage.util.movefile:movefile',
+	'portage.util._ctypes:find_library,LoadLibrary',
 	'portage.util._dyn_libs.PreservedLibsRegistry:PreservedLibsRegistry',
 	'portage.util._dyn_libs.LinkageMapELF:LinkageMapELF@LinkageMap',
 	'portage.util._async.SchedulerInterface:SchedulerInterface',
@@ -73,6 +74,7 @@ import io
 from itertools import chain
 import logging
 import os as _os
+import platform
 import pwd
 import re
 import stat
@@ -4688,7 +4690,44 @@ class dblink(object):
 		disk and avoid data-loss in the event of a power failure. This method
 		does nothing if FEATURES=merge-sync is disabled.
 		"""
-		pass
+		if not self._device_path_map or \
+			"merge-sync" not in self.settings.features:
+			return
+
+		syncfs = self._get_syncfs()
+		if syncfs is None:
+			try:
+				proc = subprocess.Popen(["sync"])
+			except EnvironmentError:
+				pass
+			else:
+				proc.wait()
+		else:
+			for path in self._device_path_map.values():
+				try:
+					fd = os.open(path, os.O_RDONLY)
+				except OSError:
+					pass
+				else:
+					try:
+						syncfs(fd)
+					except OSError:
+						pass
+					finally:
+						os.close(fd)
+
+	def _get_syncfs(self):
+		if platform.system() == "Linux":
+			filename = find_library("c")
+			if filename is not None:
+				library = LoadLibrary(filename)
+				if library is not None:
+					try:
+						return library.syncfs
+					except AttributeError:
+						pass
+
+		return None
 
 	def merge(self, mergeroot, inforoot, myroot=None, myebuild=None, cleanup=0,
 		mydbapi=None, prev_mtimes=None, counter=None):
-- 
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