[PATCH v2] btrfs: zstd ensure reclaim timer is properly cleaned up

[Dennis Zhou <dennis@kernel.org>]

The timer function, zstd_reclaim_timer_fn(), reschedules itself under
certain conditions. When cleaning up, take the lock and remove all
workspaces. This prevents the timer from rearming itself. Lastly, switch
to del_timer_sync() to ensure that the timer function can't trigger as
we're unloading.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
v2:
- cleanup workspaces and then disable the timer

 fs/btrfs/zstd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 3e418a3aeb11..6b9e29d050f3 100644
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -195,8 +195,7 @@ static void zstd_cleanup_workspace_manager(void)
 	struct workspace *workspace;
 	int i;
 
-	del_timer(&wsm.timer);
-
+	spin_lock(&wsm.lock);
 	for (i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) {
 		while (!list_empty(&wsm.idle_ws[i])) {
 			workspace = container_of(wsm.idle_ws[i].next,
@@ -206,6 +205,9 @@ static void zstd_cleanup_workspace_manager(void)
 			wsm.ops->free_workspace(&workspace->list);
 		}
 	}
+	spin_unlock(&wsm.lock);
+
+	del_timer_sync(&wsm.timer);
 }
 
 /*
-- 
2.17.1