[RFC v3 09/24] f2fs: replace kthread freezing with auto fs freezing

[Luis Chamberlain]

The kernel power management now supports allowing the VFS
to handle filesystem freezing freezes and thawing. Take advantage
of that and remove the kthread freezing. 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.

The filesystem therefore is in charge of properly dealing with
quiescing of the filesystem through its callbacks if it thinks
it knows better than how the VFS handles it.

The following Coccinelle rule was used as to remove the now superflous
freezer calls:

spatch --sp-file fs-freeze-cleanup.cocci --in-place --timeout 120 --dir fs/f2fs --jobs 12 --use-gitgrep

@ remove_set_freezable @
expression time;
statement S, S2;
expression task, current;
@@

(
-       set_freezable();
|
-       if (try_to_freeze())
-               continue;
|
-       try_to_freeze();
|
-       freezable_schedule();
+       schedule();
|
-       freezable_schedule_timeout(time);
+       schedule_timeout(time);
|
-       if (freezing(task)) { S }
|
-       if (freezing(task)) { S }
-       else
	    { S2 }
|
-       freezing(current)
)

@ remove_wq_freezable @
expression WQ_E, WQ_ARG1, WQ_ARG2, WQ_ARG3, WQ_ARG4;
identifier fs_wq_fn;
@@

(
    WQ_E = alloc_workqueue(WQ_ARG1,
-                              WQ_ARG2 | WQ_FREEZABLE,
+                              WQ_ARG2,
			   ...);
|
    WQ_E = alloc_workqueue(WQ_ARG1,
-                              WQ_ARG2 | WQ_FREEZABLE | WQ_ARG3,
+                              WQ_ARG2 | WQ_ARG3,
			   ...);
|
    WQ_E = alloc_workqueue(WQ_ARG1,
-                              WQ_ARG2 | WQ_ARG3 | WQ_FREEZABLE,
+                              WQ_ARG2 | WQ_ARG3,
			   ...);
|
    WQ_E = alloc_workqueue(WQ_ARG1,
-                              WQ_ARG2 | WQ_ARG3 | WQ_FREEZABLE | WQ_ARG4,
+                              WQ_ARG2 | WQ_ARG3 | WQ_ARG4,
			   ...);
|
	    WQ_E =
-               WQ_ARG1 | WQ_FREEZABLE
+               WQ_ARG1
|
	    WQ_E =
-               WQ_ARG1 | WQ_FREEZABLE | WQ_ARG3
+               WQ_ARG1 | WQ_ARG3
|
    fs_wq_fn(
-               WQ_FREEZABLE | WQ_ARG2 | WQ_ARG3
+               WQ_ARG2 | WQ_ARG3
    )
|
    fs_wq_fn(
-               WQ_FREEZABLE | WQ_ARG2
+               WQ_ARG2
    )
|
    fs_wq_fn(
-               WQ_FREEZABLE
+               0
    )
)

@ add_auto_flag @
expression E1;
identifier fs_type;
@@

struct file_system_type fs_type = {
	.fs_flags = E1
+                   | FS_AUTOFREEZE
	,
};

Generated-by: Coccinelle SmPL
Signed-off-by: Luis Chamberlain <mcgrof at kernel.org>
---
 fs/f2fs/gc.c      | 3 +--
 fs/f2fs/segment.c | 6 +-----
 fs/f2fs/super.c   | 2 +-
 3 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 8eac3042786b..627a7ea95851 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -42,12 +42,11 @@ static int gc_thread_func(void *data)
 
 	wait_ms = gc_th->min_sleep_time;
 
-	set_freezable();
 	do {
 		bool sync_mode, foreground = false;
 
 		wait_event_interruptible_timeout(*wq,
-				kthread_should_stop() || freezing(current) ||
+				kthread_should_stop() ||
 				waitqueue_active(fggc_wq) ||
 				gc_th->gc_wake,
 				msecs_to_jiffies(wait_ms));
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index e2f95f46d298..11cad5287047 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1682,11 +1682,9 @@ static int issue_discard_thread(void *data)
 	unsigned int wait_ms = dcc->min_discard_issue_time;
 	int issued;
 
-	set_freezable();
-
 	do {
 		wait_event_interruptible_timeout(*q,
-				kthread_should_stop() || freezing(current) ||
+				kthread_should_stop() ||
 				dcc->discard_wake,
 				msecs_to_jiffies(wait_ms));
 
@@ -1704,8 +1702,6 @@ static int issue_discard_thread(void *data)
 		if (atomic_read(&dcc->queued_discard))
 			__wait_all_discard_cmd(sbi, NULL);
 
-		if (try_to_freeze())
-			continue;
 		if (f2fs_readonly(sbi->sb))
 			continue;
 		if (kthread_should_stop())
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 87d56a9883e6..e9c6fb04c713 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4645,7 +4645,7 @@ static struct file_system_type f2fs_fs_type = {
 	.name		= "f2fs",
 	.mount		= f2fs_mount,
 	.kill_sb	= kill_f2fs_super,
-	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
+	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_AUTOFREEZE,
 };
 MODULE_ALIAS_FS("f2fs");
 
-- 
2.35.1