[RFC][PATCH -mm] PM: Do not sync filesystems from within the freezer

[Rafael J. Wysocki]

From: Rafael J. Wysocki <[EMAIL PROTECTED]>

The syncing of filesystems from within the freezer is generally not needed.
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 <[EMAIL PROTECTED]>
---
 kernel/power/disk.c    |    4 ++++
 kernel/power/main.c    |    6 ++++++
 kernel/power/process.c |    1 -
 kernel/power/user.c    |    4 ++++
 4 files changed, 14 insertions(+), 1 deletion(-)

Index: linux-2.6.22-rc6-mm1/kernel/power/disk.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/kernel/power/disk.c
+++ linux-2.6.22-rc6-mm1/kernel/power/disk.c
@@ -297,6 +297,10 @@ int hibernate(void)
        if (error)
                goto Exit;
 
+       printk("Syncing filesystems ... ");
+       sys_sync();
+       printk("done.\n");
+
        error = prepare_processes();
        if (error)
                goto Finish;
Index: linux-2.6.22-rc6-mm1/kernel/power/main.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/kernel/power/main.c
+++ linux-2.6.22-rc6-mm1/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"
 
@@ -234,9 +235,14 @@ static int enter_state(suspend_state_t s
 
        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;
Index: linux-2.6.22-rc6-mm1/kernel/power/process.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/kernel/power/process.c
+++ linux-2.6.22-rc6-mm1/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;
Index: linux-2.6.22-rc6-mm1/kernel/power/user.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/kernel/power/user.c
+++ linux-2.6.22-rc6-mm1/kernel/power/user.c
@@ -153,6 +153,10 @@ static int snapshot_ioctl(struct inode *
                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();
-
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