[RFC v3 11/24] gfs2: 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/gfs2 --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/gfs2/glock.c      | 6 +++---
 fs/gfs2/log.c        | 2 --
 fs/gfs2/main.c       | 4 ++--
 fs/gfs2/ops_fstype.c | 4 ++--
 fs/gfs2/quota.c      | 2 --
 5 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 524f3c96b9a4..7ad1a1229ae3 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -2459,14 +2459,14 @@ int __init gfs2_glock_init(void)
 	if (ret < 0)
 		return ret;
 
-	glock_workqueue = alloc_workqueue("glock_workqueue", WQ_MEM_RECLAIM |
-					  WQ_HIGHPRI | WQ_FREEZABLE, 0);
+	glock_workqueue = alloc_workqueue("glock_workqueue",
+					  WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
 	if (!glock_workqueue) {
 		rhashtable_destroy(&gl_hash_table);
 		return -ENOMEM;
 	}
 	gfs2_delete_workqueue = alloc_workqueue("delete_workqueue",
-						WQ_MEM_RECLAIM | WQ_FREEZABLE,
+						WQ_MEM_RECLAIM,
 						0);
 	if (!gfs2_delete_workqueue) {
 		destroy_workqueue(glock_workqueue);
diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 1fcc829f02ab..213fafc367f4 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1330,8 +1330,6 @@ int gfs2_logd(void *data)
 
 		t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
 
-		try_to_freeze();
-
 		do {
 			prepare_to_wait(&sdp->sd_logd_waitq, &wait,
 					TASK_INTERRUPTIBLE);
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index afcb32854f14..43d4748ad183 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -153,12 +153,12 @@ static int __init init_gfs2_fs(void)
 
 	error = -ENOMEM;
 	gfs_recovery_wq = alloc_workqueue("gfs_recovery",
-					  WQ_MEM_RECLAIM | WQ_FREEZABLE, 0);
+					  WQ_MEM_RECLAIM, 0);
 	if (!gfs_recovery_wq)
 		goto fail_wq1;
 
 	gfs2_control_wq = alloc_workqueue("gfs2_control",
-					  WQ_UNBOUND | WQ_FREEZABLE, 0);
+					  WQ_UNBOUND, 0);
 	if (!gfs2_control_wq)
 		goto fail_wq2;
 
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index c0cf1d2d0ef5..8f5a63148eaf 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1740,7 +1740,7 @@ static void gfs2_kill_sb(struct super_block *sb)
 
 struct file_system_type gfs2_fs_type = {
 	.name = "gfs2",
-	.fs_flags = FS_REQUIRES_DEV,
+	.fs_flags = FS_REQUIRES_DEV | FS_AUTOFREEZE,
 	.init_fs_context = gfs2_init_fs_context,
 	.parameters = gfs2_fs_parameters,
 	.kill_sb = gfs2_kill_sb,
@@ -1750,7 +1750,7 @@ MODULE_ALIAS_FS("gfs2");
 
 struct file_system_type gfs2meta_fs_type = {
 	.name = "gfs2meta",
-	.fs_flags = FS_REQUIRES_DEV,
+	.fs_flags = FS_REQUIRES_DEV | FS_AUTOFREEZE,
 	.init_fs_context = gfs2_meta_init_fs_context,
 	.owner = THIS_MODULE,
 };
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 1ed17226d9ed..710764af9d04 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -1555,8 +1555,6 @@ int gfs2_quotad(void *data)
 		quotad_check_timeo(sdp, "sync", gfs2_quota_sync, t,
 				   &quotad_timeo, &tune->gt_quota_quantum);
 
-		try_to_freeze();
-
 bypass:
 		t = min(quotad_timeo, statfs_timeo);
 
-- 
2.35.1