> From: Balbir Singh <[EMAIL PROTECTED]>
> void page_assign_page_cgroup(struct page *page, struct page_cgroup *pc)
> {
> - page->page_cgroup = (unsigned long)pc;
> + int locked;
> +
> + /*
> + * While resetting the page_cgroup we might not hold the
> + * page_cgroup lock. free_hot_cold_page() is an example
> + * of such a scenario
> + */
> + if (pc)
> + VM_BUG_ON(!page_cgroup_locked(page));
> + locked = (page->page_cgroup & PAGE_CGROUP_LOCK);
> + page->page_cgroup = ((unsigned long)pc | locked);
> }
This looks a bit odd, why not write:
locked = page_cgroup_locked(page);
if (pc)
VM_BUG_ON(!locked)
> +/*
> + * Charge the memory controller for page usage.
> + * Return
> + * 0 if the charge was successful
> + * < 0 if the cgroup is over its limit
> + */
> +int mem_cgroup_charge(struct page *page, struct mm_struct *mm)
> +{
> + struct mem_cgroup *mem;
> + struct page_cgroup *pc, *race_pc;
> +
> + /*
> + * Should page_cgroup's go to their own slab?
> + * One could optimize the performance of the charging routine
> + * by saving a bit in the page_flags and using it as a lock
> + * to see if the cgroup page already has a page_cgroup associated
> + * with it
> + */
> + lock_page_cgroup(page);
> + pc = page_get_page_cgroup(page);
> + /*
> + * The page_cgroup exists and the page has already been accounted
> + */
> + if (pc) {
> + atomic_inc(&pc->ref_cnt);
> + goto done;
> + }
> +
> + unlock_page_cgroup(page);
> +
> + pc = kzalloc(sizeof(struct page_cgroup), GFP_KERNEL);
> + if (pc == NULL)
> + goto err;
> +
> + rcu_read_lock();
> + /*
> + * We always charge the cgroup the mm_struct belongs to
> + * the mm_struct's mem_cgroup changes on task migration if the
> + * thread group leader migrates. It's possible that mm is not
> + * set, if so charge the init_mm (happens for pagecache usage).
> + */
> + if (!mm)
> + mm = &init_mm;
> +
> + mem = rcu_dereference(mm->mem_cgroup);
> + /*
> + * For every charge from the cgroup, increment reference
> + * count
> + */
> + css_get(&mem->css);
> + rcu_read_unlock();
> +
> + /*
> + * If we created the page_cgroup, we should free it on exceeding
> + * the cgroup limit.
> + */
> + if (res_counter_charge(&mem->res, 1)) {
> + css_put(&mem->css);
> + goto free_pc;
> + }
> +
> + lock_page_cgroup(page);
> + /*
> + * Check if somebody else beat us to allocating the page_cgroup
> + */
> + race_pc = page_get_page_cgroup(page);
> + if (race_pc) {
> + kfree(pc);
> + pc = race_pc;
> + atomic_inc(&pc->ref_cnt);
This inc
> + res_counter_uncharge(&mem->res, 1);
> + css_put(&mem->css);
> + goto done;
> + }
> +
> + atomic_set(&pc->ref_cnt, 1);
combined with this set make me wonder...
> + pc->mem_cgroup = mem;
> + pc->page = page;
> + page_assign_page_cgroup(page, pc);
> +
> +done:
> + unlock_page_cgroup(page);
> + return 0;
> +free_pc:
> + kfree(pc);
> + return -ENOMEM;
> +err:
> + unlock_page_cgroup(page);
> + return -ENOMEM;
> +}
> @@ -2161,6 +2184,9 @@ static int do_anonymous_page(struct mm_s
> if (!page)
> goto oom;
>
> + if (mem_cgroup_charge(page, mm))
> + goto oom_free_page;
> +
> entry = mk_pte(page, vma->vm_page_prot);
> entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>
whitespace damage
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