Re: [PATCH 2/6] BC: beancounters core (API)

Oleg Nesterov
2006-08-24T17:09:36Z

On 08/23, Kirill Korotaev wrote:
>
> +struct beancounter *beancounter_findcreate(uid_t uid, int mask)
> +{
> + struct beancounter *new_bc, *bc;
> + unsigned long flags;
> + struct hlist_head *slot;
> + struct hlist_node *pos;
> +
> + slot = &bc_hash[bc_hash_fun(uid)];
> + new_bc = NULL;
> +
> +retry:
> + spin_lock_irqsave(&bc_hash_lock, flags);
> + hlist_for_each_entry (bc, pos, slot, hash)
> + if (bc->bc_id == uid)
> + break;
> +
> + if (pos != NULL) {
> + get_beancounter(bc);
> + spin_unlock_irqrestore(&bc_hash_lock, flags);
> +
> + if (new_bc != NULL)
> + kmem_cache_free(bc_cachep, new_bc);
> + return bc;
> + }
> +
> + if (!(mask & BC_ALLOC))
> + goto out_unlock;

Very minor nit: it is not clear why we are doing this check under
bc_hash_lock. I'd suggest to do

if (!(mask & BC_ALLOC))
goto out;

after unlock(bc_hash_lock) and kill out_unlock label.

> + if (new_bc != NULL)
> + goto out_install;
> +
> + spin_unlock_irqrestore(&bc_hash_lock, flags);
> +
> + new_bc = kmem_cache_alloc(bc_cachep,
> + mask & BC_ALLOC_ATOMIC ? GFP_ATOMIC : GFP_KERNEL);
> + if (new_bc == NULL)
> + goto out;
> +
> + memcpy(new_bc, &default_beancounter, sizeof(*new_bc));

May be it is just me, but I need a couple of seconds to parse this 'memcpy'.
How about

*new_bc = default_beancounter;

?

Oleg.