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SubjectRe: [PATCH v2] btrfs: zstd ensure reclaim timer is properly cleaned up
On Fri, Feb 22, 2019 at 02:53:48PM -0500, Dennis Zhou wrote:
> 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>

Reviewed-by: David Sterba <dsterba@suse.com>

> ---
> 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);

I've noticed while reading the code, why do you use the indirect call
here? The wsm.ops points to btrfs_zstd_compress so free_workspace is
always zstd_free_workspace.

The compiler is usually smart to replace such things by direct call if
the type has not escaped, but this is not true for btrfs_compress_op so
the indirect function call must be preserved.

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