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>

4 files changed, 14 insertions, 1 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 9348d95a4fb..555c0f0b2f7 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -313,6 +313,10 @@ int hibernate(void)
         if (error)
                 goto Exit;
 
+        printk("Syncing filesystems ... ");
+        sys_sync();
+        printk("done.\n");
+
         error = prepare_processes();
         if (error)
                 goto Finish;
diff --git a/kernel/power/main.c b/kernel/power/main.c
index fb2412e7a0c..3cdf95b1dc9 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -20,6 +20,7 @@
 #include <linux/resume-trace.h>
 #include <linux/freezer.h>
 #include <linux/vmstat.h>
+#include <linux/syscalls.h>
 
 #include "power.h"
 
@@ -230,9 +231,14 @@ static int enter_state(suspend_state_t state)
 
         if (!valid_state(state))
                 return -ENODEV;
+
         if (!mutex_trylock(&pm_mutex))
                 return -EBUSY;
 
+        printk("Syncing filesystems ... ");
+        sys_sync();
+        printk("done.\n");
+
         pr_debug("PM: Preparing system for %s sleep\n", pm_states[state]);
         if ((error = suspend_prepare()))
                 goto Unlock;
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 3434940a3df..dba2f3acb4f 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -191,7 +191,6 @@ int freeze_processes(void)
         if (error)
                 return error;
 
-        sys_sync();
         error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
         if (error)
                 return error;
diff --git a/kernel/power/user.c b/kernel/power/user.c
index bd0723a7df3..5bd321bcbb7 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -153,6 +153,10 @@ static int snapshot_ioctl(struct inode *inode, struct file *filp,
                 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();