[Cluster-devel] [GFS2 PATCH 2/2] GFS2: Use resizable hash table for glocks

[Andreas Gruenbacher]

Bob,

[sorry for the empty previous reply ...]

2015-07-09 20:25 GMT+02:00 Bob Peterson <rpeterso at redhat.com>:
> @@ -1460,31 +1421,24 @@ static struct shrinker glock_shrinker = {
>   *
>   */
>
> -static void examine_bucket(glock_examiner examiner, const struct gfs2_sbd *sdp,
> -                         unsigned int hash)
> +static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
>  {
>         struct gfs2_glock *gl;
> -       struct hlist_bl_head *head = &gl_hash_table[hash];
> -       struct hlist_bl_node *pos;
> +       struct rhash_head *pos, *next;
> +       const struct bucket_table *tbl;
> +       int i;
>
> -       rcu_read_lock();
> -       hlist_bl_for_each_entry_rcu(gl, pos, head, gl_list) {
> -               if ((gl->gl_name.ln_sbd == sdp) && lockref_get_not_dead(&gl->gl_lockref))
> -                       examiner(gl);
> +       tbl = rht_dereference_rcu(gl_hash_table.tbl, &gl_hash_table);
> +       for (i = 0; i < tbl->size; i++) {
> +               rht_for_each_entry_safe(gl, pos, next, tbl, i, gl_node) {
> +                       if ((gl->gl_name.ln_sbd == sdp) &&
> +                           lockref_get_not_dead(&gl->gl_lockref))
> +                               examiner(gl);
> +               }
>         }
> -       rcu_read_unlock();
>         cond_resched();
>  }
>
> -static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
> -{
> -       unsigned x;
> -
> -       for (x = 0; x < GFS2_GL_HASH_SIZE; x++)
> -               examine_bucket(examiner, sdp, x);
> -}
> -
> -
>  /**
>   * thaw_glock - thaw out a glock which has an unprocessed reply waiting
>   * @gl: The glock to thaw

I don't think we can drop the rcu read lock in glock_hash_walk(): That
"lock" prevents a concurrent hash table resize from freeing the bucket
table under us.

Thanks,
Andreas