@@ -1648,3 +1648,88 @@ int thaw_super(struct super_block *sb)
return error;
}
EXPORT_SYMBOL(thaw_super);
+
+#ifdef CONFIG_PM_SLEEP
+static bool super_should_freeze(struct super_block *sb)
+{
+ if (!sb->s_root)
+ return false;
+ if (!(sb->s_flags & MS_BORN))
+ return false;
+ /*
+ * We don't freeze virtual filesystems, we skip those filesystems with
+ * no backing device.
+ */
+ if (sb->s_bdi == &noop_backing_dev_info)
+ return false;
+ /* No need to freeze read-only filesystems */
+ if (sb->s_flags & MS_RDONLY)
+ return false;
+
+ return true;
+}
+
+static int fs_suspend_freeze_sb(struct super_block *sb, void *priv)
+{
+ int error = 0;
+
+ spin_lock(&sb_lock);
+ if (!super_should_freeze(sb))
+ goto out;
+
+ pr_info("%s (%s): freezing\n", sb->s_type->name, sb->s_id);
+
+ spin_unlock(&sb_lock);
+
+ atomic_inc(&sb->s_active);
+ error = freeze_locked_super(sb, false);
+ if (error)
+ atomic_dec(&sb->s_active);
+
+ spin_lock(&sb_lock);
+ if (error && error != -EBUSY)
+ pr_notice("%s (%s): Unable to freeze, error=%d",
+ sb->s_type->name, sb->s_id, error);
+
+out:
+ spin_unlock(&sb_lock);
+ return error;
+}
+
+int fs_suspend_freeze(void)
+{
+ return iterate_supers_reverse_excl(fs_suspend_freeze_sb, NULL);
+}
+
+static int fs_suspend_thaw_sb(struct super_block *sb, void *priv)
+{
+ int error = 0;
+
+ spin_lock(&sb_lock);
+ if (!super_should_freeze(sb))
+ goto out;
+
+ pr_info("%s (%s): thawing\n", sb->s_type->name, sb->s_id);
+
+ spin_unlock(&sb_lock);
+
+ error = thaw_locked_super(sb, false);
+ if (!error)
+ atomic_dec(&sb->s_active);
+
+ spin_lock(&sb_lock);
+ if (error && error != -EBUSY)
+ pr_notice("%s (%s): Unable to unfreeze, error=%d",
+ sb->s_type->name, sb->s_id, error);
+
+out:
+ spin_unlock(&sb_lock);
+ return error;
+}
+
+int fs_resume_unfreeze(void)
+{
+ return iterate_supers_excl(fs_suspend_thaw_sb, NULL);
+}
+
+#endif
@@ -2237,6 +2237,19 @@ extern int user_statfs(const char __user *, struct kstatfs *);
extern int fd_statfs(int, struct kstatfs *);
extern int freeze_super(struct super_block *super);
extern int thaw_super(struct super_block *super);
+#ifdef CONFIG_PM_SLEEP
+int fs_suspend_freeze(void);
+int fs_resume_unfreeze(void);
+#else
+static inline int fs_suspend_freeze(void)
+{
+ return 0;
+}
+static inline int fs_resume_unfreeze(void)
+{
+ return 0;
+}
+#endif
extern bool our_mnt(struct vfsmount *mnt);
extern __printf(2, 3)
int super_setup_bdi_name(struct super_block *sb, char *fmt, ...);
@@ -145,6 +145,16 @@ int freeze_processes(void)
pr_cont("\n");
BUG_ON(in_atomic());
+ pr_info("Freezing filesystems ... ");
+ error = fs_suspend_freeze();
+ if (error) {
+ pr_cont("failed\n");
+ fs_resume_unfreeze();
+ thaw_processes();
+ return error;
+ }
+ pr_cont("done.\n");
+
/*
* Now that the whole userspace is frozen we need to disbale
* the OOM killer to disallow any further interference with
@@ -154,8 +164,10 @@ int freeze_processes(void)
if (!error && !oom_killer_disable(msecs_to_jiffies(freeze_timeout_msecs)))
error = -EBUSY;
- if (error)
+ if (error) {
+ fs_resume_unfreeze();
thaw_processes();
+ }
return error;
}
@@ -198,6 +210,7 @@ void thaw_processes(void)
pm_nosig_freezing = false;
oom_killer_enable();
+ fs_resume_unfreeze();
pr_info("Restarting tasks ... ");
This uses the existing filesystem freeze and thaw callbacks to freeze each filesystem on suspend/hibernation and thaw upon resume. This is needed so that we properly really stop IO in flight without races after userspace has been frozen. Without this we rely on kthread freezing and its semantics are loose and error prone. For instance, even though a kthread may use try_to_freeze() and end up being frozen we have no way of being sure that everything that has been spawned asynchronously from it (such as timers) have also been stopped as well. A long term advantage of also adding filesystem freeze / thawing supporting durign suspend / hibernation is that long term we may be able to eventually drop the kernel's thread freezing completely as it was originally added to stop disk IO in flight as we hibernate or suspend. This also implies that many kthread users exist which have been adding freezer semantics onto its kthreads without need. These also will need to be reviewed later. This is based on prior work originally by Rafael Wysocki and later by Jiri Kosina. Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> --- fs/super.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 13 ++++++++ kernel/power/process.c | 15 ++++++++- 3 files changed, 112 insertions(+), 1 deletion(-)