[RFC][PATCH -mm] PM: Do not sync from within the freezer during suspend to RAM

[Rafael J. Wysocki]

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

The syncing of filesystems from within the freezer in not needed for suspend to
RAM.  Change freeze_processes() so that it doesn't execute sys_sync() and
introduce the "syncing" version of it to be called from the hibernation code
paths.

Signed-off-by: Rafael J. Wysocki <[EMAIL PROTECTED]>
---
 include/linux/freezer.h |   14 ++++++++++++--
 kernel/power/disk.c     |    2 +-
 kernel/power/main.c     |    6 ++++++
 kernel/power/process.c  |    8 +++++---
 kernel/power/user.c     |    2 +-
 5 files changed, 25 insertions(+), 7 deletions(-)

Index: linux-2.6.22-rc7/include/linux/freezer.h
===================================================================
--- linux-2.6.22-rc7.orig/include/linux/freezer.h       2007-07-04 
00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/include/linux/freezer.h    2007-07-04 00:22:37.000000000 
+0200
@@ -62,7 +62,7 @@ static inline int thaw_process(struct ta
 }
 
 extern void refrigerator(void);
-extern int freeze_processes(void);
+extern int __freeze_processes(int sync_filesystems);
 extern void thaw_processes(void);
 
 static inline int try_to_freeze(void)
@@ -134,7 +134,7 @@ static inline void clear_freeze_flag(str
 static inline int thaw_process(struct task_struct *p) { return 1; }
 
 static inline void refrigerator(void) {}
-static inline int freeze_processes(void) { BUG(); return 0; }
+static inline int __freeze_processes(int s) { BUG(); return 0; }
 static inline void thaw_processes(void) {}
 
 static inline int try_to_freeze(void) { return 0; }
@@ -145,4 +145,14 @@ static inline int freezer_should_skip(st
 static inline void set_freezable(void) {}
 #endif
 
+static inline int freeze_processes(void)
+{
+       return __freeze_processes(0);
+}
+
+static inline int freeze_processes_with_sync(void)
+{
+       return __freeze_processes(1);
+}
+
 #endif /* FREEZER_H_INCLUDED */
Index: linux-2.6.22-rc7/kernel/power/disk.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/disk.c   2007-07-04 00:21:26.000000000 
+0200
+++ linux-2.6.22-rc7/kernel/power/disk.c        2007-07-04 00:21:44.000000000 
+0200
@@ -281,7 +281,7 @@ static int prepare_processes(void)
        int error = 0;
 
        pm_prepare_console();
-       if (freeze_processes()) {
+       if (freeze_processes_with_sync()) {
                error = -EBUSY;
                unprepare_processes();
        }
Index: linux-2.6.22-rc7/kernel/power/main.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/main.c   2007-07-04 00:21:26.000000000 
+0200
+++ linux-2.6.22-rc7/kernel/power/main.c        2007-07-04 00:23:40.000000000 
+0200
@@ -20,6 +20,7 @@
 #include <linux/resume-trace.h>
 #include <linux/freezer.h>
 #include <linux/vmstat.h>
+#include <linux/syscalls.h>
 
 #include "power.h"
 
@@ -231,6 +232,11 @@ static int enter_state(suspend_state_t s
 
        if (!valid_state(state))
                return -ENODEV;
+
+       printk("Syncing filesystems ... ");
+       sys_sync();
+       printk("done.\n");
+
        if (!mutex_trylock(&pm_mutex))
                return -EBUSY;
 
Index: linux-2.6.22-rc7/kernel/power/process.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/process.c        2007-07-04 
00:21:26.000000000 +0200
+++ linux-2.6.22-rc7/kernel/power/process.c     2007-07-04 00:21:44.000000000 
+0200
@@ -179,9 +179,9 @@ static int try_to_freeze_tasks(int freez
 }
 
 /**
- *     freeze_processes - tell processes to enter the refrigerator
+ *     __freeze_processes - tell processes to enter the refrigerator
  */
-int freeze_processes(void)
+int __freeze_processes(int sync_filesystems)
 {
        int error;
 
@@ -190,7 +190,9 @@ int freeze_processes(void)
        if (error)
                return error;
 
-       sys_sync();
+       if (sync_filesystems)
+               sys_sync();
+
        error = try_to_freeze_tasks(FREEZER_KERNEL_THREADS);
        if (error)
                return error;
Index: linux-2.6.22-rc7/kernel/power/user.c
===================================================================
--- linux-2.6.22-rc7.orig/kernel/power/user.c   2007-07-04 00:21:26.000000000 
+0200
+++ linux-2.6.22-rc7/kernel/power/user.c        2007-07-04 00:21:44.000000000 
+0200
@@ -153,7 +153,7 @@ static int snapshot_ioctl(struct inode *
                mutex_lock(&pm_mutex);
                error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
                if (!error) {
-                       error = freeze_processes();
+                       error = freeze_processes_with_sync();
                        if (error)
                                thaw_processes();
                }
-
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