[PATCH 1/2] gfs2: Add missing set_freezable() for freezable kthread

[PATCH 1/2] gfs2: Add missing set_freezable() for freezable kthread

[Kevin Hao]

The kernel thread function gfs2_logd() and gfs2_quotad() invoke the
try_to_freeze() in its loop. But all the kernel threads are no-freezable
by default. So if we want to make a kernel thread to be freezable,
we have to invoke set_freezable() explicitly.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
---
 fs/gfs2/log.c   | 1 +
 fs/gfs2/quota.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index e5271ae87d1c..a268b69bb636 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1297,6 +1297,7 @@ int gfs2_logd(void *data)
 	struct gfs2_sbd *sdp = data;
 	unsigned long t = 1;
 
+	set_freezable();
 	while (!kthread_should_stop()) {
 		if (gfs2_withdrawn(sdp))
 			break;
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index fa47824acf13..173581736a6e 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -1583,6 +1583,7 @@ int gfs2_quotad(void *data)
 	unsigned long quotad_timeo = 0;
 	unsigned long t = 0;
 
+	set_freezable();
 	while (!kthread_should_stop()) {
 		if (gfs2_withdrawn(sdp))
 			break;
-- 
2.39.2

[PATCH 2/2] gfs2: Use wait_event_freezable_timeout() for freezable kthread

[Kevin Hao]

A freezable kernel thread can enter frozen state during freezing by
either calling try_to_freeze() or using wait_event_freezable() and its
variants. So for the following snippet of code in a kernel thread loop:
  try_to_freeze();
  wait_event_interruptible_timeout();

We can change it to a simple wait_event_freezable_timeout() and then
eliminate a function call.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
---
 fs/gfs2/log.c   | 4 +---
 fs/gfs2/quota.c | 4 +---
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index a268b69bb636..20059fc913e7 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1331,9 +1331,7 @@ int gfs2_logd(void *data)
 
 		t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
 
-		try_to_freeze();
-
-		t = wait_event_interruptible_timeout(sdp->sd_logd_waitq,
+		t = wait_event_freezable_timeout(sdp->sd_logd_waitq,
 				test_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags) ||
 				gfs2_ail_flush_reqd(sdp) ||
 				gfs2_jrnl_flush_reqd(sdp) ||
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 173581736a6e..05ef8409b614 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -1603,11 +1603,9 @@ int gfs2_quotad(void *data)
 		quotad_check_timeo(sdp, "sync", gfs2_quota_sync, t,
 				   &quotad_timeo, &tune->gt_quota_quantum);
 
-		try_to_freeze();
-
 		t = min(quotad_timeo, statfs_timeo);
 
-		t = wait_event_interruptible_timeout(sdp->sd_quota_wait,
+		t = wait_event_freezable_timeout(sdp->sd_quota_wait,
 				sdp->sd_statfs_force_sync ||
 				gfs2_withdrawn(sdp) ||
 				kthread_should_stop(),
-- 
2.39.2

Re: [PATCH 1/2] gfs2: Add missing set_freezable() for freezable kthread

[Andreas Gruenbacher]

Kevin,

On Mon, Dec 18, 2023 at 6:36 AM Kevin Hao <haokexin@gmail.com> wrote:
> The kernel thread function gfs2_logd() and gfs2_quotad() invoke the
> try_to_freeze() in its loop. But all the kernel threads are no-freezable
> by default. So if we want to make a kernel thread to be freezable,
> we have to invoke set_freezable() explicitly.
>
> Signed-off-by: Kevin Hao <haokexin@gmail.com>
> ---
>  fs/gfs2/log.c   | 1 +
>  fs/gfs2/quota.c | 1 +
>  2 files changed, 2 insertions(+)
>
> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> index e5271ae87d1c..a268b69bb636 100644
> --- a/fs/gfs2/log.c
> +++ b/fs/gfs2/log.c
> @@ -1297,6 +1297,7 @@ int gfs2_logd(void *data)
>         struct gfs2_sbd *sdp = data;
>         unsigned long t = 1;
>
> +       set_freezable();
>         while (!kthread_should_stop()) {
>                 if (gfs2_withdrawn(sdp))
>                         break;
> diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
> index fa47824acf13..173581736a6e 100644
> --- a/fs/gfs2/quota.c
> +++ b/fs/gfs2/quota.c
> @@ -1583,6 +1583,7 @@ int gfs2_quotad(void *data)
>         unsigned long quotad_timeo = 0;
>         unsigned long t = 0;
>
> +       set_freezable();
>         while (!kthread_should_stop()) {
>                 if (gfs2_withdrawn(sdp))
>                         break;
> --
> 2.39.2
>

This is looking good, thank you. I've applied it to our for-next branch.

Andreas

Re: [PATCH 2/2] gfs2: Use wait_event_freezable_timeout() for freezable kthread

[Andreas Gruenbacher]

Kevin,

On Mon, Dec 18, 2023 at 6:36 AM Kevin Hao <haokexin@gmail.com> wrote:
> A freezable kernel thread can enter frozen state during freezing by
> either calling try_to_freeze() or using wait_event_freezable() and its
> variants. So for the following snippet of code in a kernel thread loop:
>   try_to_freeze();
>   wait_event_interruptible_timeout();
>
> We can change it to a simple wait_event_freezable_timeout() and then
> eliminate a function call.
>
> Signed-off-by: Kevin Hao <haokexin@gmail.com>
> ---
>  fs/gfs2/log.c   | 4 +---
>  fs/gfs2/quota.c | 4 +---
>  2 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
> index a268b69bb636..20059fc913e7 100644
> --- a/fs/gfs2/log.c
> +++ b/fs/gfs2/log.c
> @@ -1331,9 +1331,7 @@ int gfs2_logd(void *data)
>
>                 t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
>
> -               try_to_freeze();
> -
> -               t = wait_event_interruptible_timeout(sdp->sd_logd_waitq,
> +               t = wait_event_freezable_timeout(sdp->sd_logd_waitq,
>                                 test_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags) ||
>                                 gfs2_ail_flush_reqd(sdp) ||
>                                 gfs2_jrnl_flush_reqd(sdp) ||
> diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
> index 173581736a6e..05ef8409b614 100644
> --- a/fs/gfs2/quota.c
> +++ b/fs/gfs2/quota.c
> @@ -1603,11 +1603,9 @@ int gfs2_quotad(void *data)
>                 quotad_check_timeo(sdp, "sync", gfs2_quota_sync, t,
>                                    &quotad_timeo, &tune->gt_quota_quantum);
>
> -               try_to_freeze();
> -
>                 t = min(quotad_timeo, statfs_timeo);
>
> -               t = wait_event_interruptible_timeout(sdp->sd_quota_wait,
> +               t = wait_event_freezable_timeout(sdp->sd_quota_wait,
>                                 sdp->sd_statfs_force_sync ||
>                                 gfs2_withdrawn(sdp) ||
>                                 kthread_should_stop(),
> --
> 2.39.2
>

This also is looking good; applied as well.

Thank you,
Andreas