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SubjectRe: [RFC][PATCH 2/7] UBC: core (structures, API)
Kirill Korotaev wrote:
>
> +struct user_beancounter *beancounter_findcreate(uid_t uid,
> + struct user_beancounter *p, int mask)
> +{
> + struct user_beancounter *new_ub, *ub, *tmpl_ub;
> + unsigned long flags;
> + struct hlist_head *slot;
> + struct hlist_node *pos;
> +
> + if (mask & UB_LOOKUP_SUB) {
> + WARN_ON(p == NULL);
> + tmpl_ub = &default_subbeancounter;
> + slot = &ub_hash[ub_subhash_fun(p, uid)];
> + } else {
> + WARN_ON(p != NULL);
> + tmpl_ub = &default_beancounter;
> + slot = &ub_hash[ub_hash_fun(uid)];
> + }
> + new_ub = NULL;
> +
> +retry:
> + spin_lock_irqsave(&ub_hash_lock, flags);
> + hlist_for_each_entry (ub, pos, slot, hash)
> + if (ub->ub_uid == uid && ub->parent == p)
> + break;
> +
> + if (pos != NULL) {
> + get_beancounter(ub);
> + spin_unlock_irqrestore(&ub_hash_lock, flags);
> +
> + if (new_ub != NULL) {
> + put_beancounter(new_ub->parent);
^^^^^^^^^^^^^^

Stupid question: why ->parent can't be NULL ? (without UB_LOOKUP_SUB).

> + if (mask & UB_ALLOC_ATOMIC) {
> + new_ub = kmem_cache_alloc(ub_cachep, GFP_ATOMIC);
> + if (new_ub == NULL)
> + goto out_unlock;
> +
> + memcpy(new_ub, tmpl_ub, sizeof(*new_ub));
> + init_beancounter_struct(new_ub, uid);
> + if (p)
> + new_ub->parent = get_beancounter(p);
> + goto out_install;
> + }
> +
> + spin_unlock_irqrestore(&ub_hash_lock, flags);
> +
> + new_ub = kmem_cache_alloc(ub_cachep, GFP_KERNEL);

beancounter_findcreate() is not time critical, yes? Isn't it better
to kill 'if (mask & UB_ALLOC_ATOMIC) { ... }' and just do

new_ub = kmem_cache_alloc(ub_cachep,
UB_ALLOC_ATOMIC ? GFP_ATOMIC : GFP_KERNEL);

after spin_unlock(&ub_hash_lock) ?

Oleg.

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