From 3f53a96a8bd0cd4a18f819b6857e6a764706ede5 Mon Sep 17 00:00:00 2001
From: Filipe David Manana <fdmanana@gmail.com>
Date: Thu, 22 Apr 2010 23:40:26 +0100
Subject: Add file:datasync/1 for syncing file contents only

file:datasync/1 invokes the POSIX system call "int fdatasync(int fd)".
This system call is similar to "fsync" but, unlike fsync, it does not
update the metadata associated with the file (like the access time for
example). It's used by many DBMSs (MySQL and SQLite of example) to
increase disk IO performance, as it avoids disk seeks and disk write
operations compared to fsync.

More details on it at:

http://linux.die.net/man/2/fdatasync

An example, from the MySQL source:

http://bazaar.launchpad.net/~mysql/mysql-server/mysql-5.1-telco-6.1/annotate/head%3A/mysys/my_sync.c#L61

This new function just calls fsync on systems not implementing fdatasync.
---
 lib/kernel/test/file_SUITE.erl | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

(limited to 'lib/kernel/test/file_SUITE.erl')

diff --git a/lib/kernel/test/file_SUITE.erl b/lib/kernel/test/file_SUITE.erl
index 1d170790a3..2e6c3aba16 100644
--- a/lib/kernel/test/file_SUITE.erl
+++ b/lib/kernel/test/file_SUITE.erl
@@ -52,7 +52,7 @@
 	 old_modes/1, new_modes/1, path_open/1, open_errors/1]).
 -export([file_info/1, file_info_basic_file/1, file_info_basic_directory/1,
 	 file_info_bad/1, file_info_times/1, file_write_file_info/1]).
--export([rename/1, access/1, truncate/1, sync/1,
+-export([rename/1, access/1, truncate/1, datasync/1, sync/1,
 	 read_write/1, pread_write/1, append/1]).
 -export([errors/1, e_delete/1, e_rename/1, e_make_dir/1, e_del_dir/1]).
 -export([otp_5814/1]).
@@ -377,7 +377,7 @@ win_cur_dir_1(_Config) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-files(suite) -> [open,pos,file_info,consult,eval,script,truncate,sync].
+files(suite) -> [open,pos,file_info,consult,eval,script,truncate,sync,datasync].
 
 open(suite) -> [open1,old_modes,new_modes,path_open,close,access,read_write,
 	       pread_write,append,open_errors].
@@ -1355,6 +1355,30 @@ truncate(Config) when is_list(Config) ->
     ok.
 
 
+datasync(suite) -> [];
+datasync(doc) -> "Tests that ?FILE_MODULE:datasync/1 at least doesn't crash.";
+datasync(Config) when is_list(Config) ->
+    ?line Dog = test_server:timetrap(test_server:seconds(5)),
+    ?line PrivDir = ?config(priv_dir, Config),
+    ?line Sync = filename:join(PrivDir,
+			       atom_to_list(?MODULE)
+			       ++"_sync.fil"),
+
+    %% Raw open.
+    ?line {ok, Fd} = ?FILE_MODULE:open(Sync, [write, raw]),
+    ?line ok = ?FILE_MODULE:datasync(Fd),
+    ?line ok = ?FILE_MODULE:close(Fd),
+
+    %% Ordinary open.
+    ?line {ok, Fd2} = ?FILE_MODULE:open(Sync, [write]),
+    ?line ok = ?FILE_MODULE:datasync(Fd2),
+    ?line ok = ?FILE_MODULE:close(Fd2),
+
+    ?line [] = flush(),
+    ?line test_server:timetrap_cancel(Dog),
+    ok.
+
+
 sync(suite) -> [];
 sync(doc) -> "Tests that ?FILE_MODULE:sync/1 at least doesn't crash.";
 sync(Config) when is_list(Config) ->
-- 
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