linux-kernel - [RFC v3 17/24] ksmbd: replace kthread freezing with auto fs freezing

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Message-Id: <20230114003409.1168311-18-mcgrof@kernel.org>
Date:   Fri, 13 Jan 2023 16:34:02 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     hch@...radead.org, djwong@...nel.org, song@...nel.org,
        rafael@...nel.org, gregkh@...uxfoundation.org,
        viro@...iv.linux.org.uk, jack@...e.cz, bvanassche@....org,
        ebiederm@...ssion.com
Cc:     mchehab@...nel.org, keescook@...omium.org, p.raghav@...sung.com,
        linux-fsdevel@...r.kernel.org, kernel@...force.de,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: [RFC v3 17/24] ksmbd: replace kthread freezing with auto fs freezing

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/nfs --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@...nel.org>
---
 fs/ksmbd/connection.c    | 3 ---
 fs/ksmbd/transport_tcp.c | 2 --
 2 files changed, 5 deletions(-)

diff --git a/fs/ksmbd/connection.c b/fs/ksmbd/connection.c
index fd0a288af299..4ed17de1423e 100644
--- a/fs/ksmbd/connection.c
+++ b/fs/ksmbd/connection.c
@@ -292,9 +292,6 @@ int ksmbd_conn_handler_loop(void *p)
 
 	conn->last_active = jiffies;
 	while (ksmbd_conn_alive(conn)) {
-		if (try_to_freeze())
-			continue;
-
 		kvfree(conn->request_buf);
 		conn->request_buf = NULL;
 
diff --git a/fs/ksmbd/transport_tcp.c b/fs/ksmbd/transport_tcp.c
index 4c6bd0b69979..dadb4f306428 100644
--- a/fs/ksmbd/transport_tcp.c
+++ b/fs/ksmbd/transport_tcp.c
@@ -305,8 +305,6 @@ static int ksmbd_tcp_readv(struct tcp_transport *t, struct kvec *iov_orig,
 	ksmbd_msg.msg_controllen = 0;
 
 	for (total_read = 0; to_read; total_read += length, to_read -= length) {
-		try_to_freeze();
-
 		if (!ksmbd_conn_alive(conn)) {
 			total_read = -ESHUTDOWN;
 			break;
-- 
2.35.1