On Mon 11-08-25 15:23:03, Uros Bizjak wrote:
> Use !try_cmpxchg() instead of cmpxchg(*ptr, old, new) != old.
>
> The x86 CMPXCHG instruction returns success in the ZF flag,
> so this change saves a compare after CMPXCHG.
>
> No functional change intended.
>
> Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/super.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index 7f876f32343a..e91718017701 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -2318,13 +2318,15 @@ int sb_init_dio_done_wq(struct super_block *sb)
> sb->s_id);
> if (!wq)
> return -ENOMEM;
> +
> + old = NULL;
> /*
> * This has to be atomic as more DIOs can race to create the workqueue
> */
> - old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
> - /* Someone created workqueue before us? Free ours... */
> - if (old)
> + if (!try_cmpxchg(&sb->s_dio_done_wq, &old, wq)) {
> + /* Someone created workqueue before us? Free ours... */
> destroy_workqueue(wq);
> + }
> return 0;
> }
> EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);
> --
> 2.50.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
