freezer: do not sync filesystems from freeze_processes

The syncing of filesystems from within the freezer is generally not needed.
Also, if there's an ext3 filesystem loopback-mounted from a FUSE one, the
syncing results in writes to it and deadlocks.  Similarly, it will deadlock if
FUSE implements sync.

Change freeze_processes() so that it doesn't execute sys_sync() and make the
suspend and hibernation code path sync filesystems independently of the
freezer.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/power/user.c b/kernel/power/user.c
index bd0723a..5bd321b 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -153,6 +153,10 @@
 		mutex_lock(&pm_mutex);
 		error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
 		if (!error) {
+			printk("Syncing filesystems ... ");
+			sys_sync();
+			printk("done.\n");
+
 			error = freeze_processes();
 			if (error)
 				thaw_processes();