On 7/20/07, Balbir Singh <[EMAIL PROTECTED]> wrote:
+void __always_inline unlock_meta_page(struct page *page)
+{
+ bit_spin_unlock(PG_metapage, &page->flags);
+}
Maybe add a BUG_ON(!test_bit(PG_metapage, &page->flags)) at least for
development?
+ mem = rcu_dereference(mm->mem_container);
+ /*
+ * For every charge from the container, increment reference
+ * count
+ */
+ css_get(&mem->css);
+ rcu_read_unlock();
It's not clear to me that this is safe.
If
+
+ /*
+ * If we created the meta_page, we should free it on exceeding
+ * the container limit.
+ */
+ if (res_counter_charge(&mem->res, 1)) {
+ css_put(&mem->css);
+ goto free_mp;
+ }
+
+ lock_meta_page(page);
+ /*
+ * Check if somebody else beat us to allocating the meta_page
+ */
+ if (page_get_meta_page(page)) {
I think you need to add something like
kfree(mp);
mp = page_get_meta_page(page);
otherwise you're going to leak the new but unneeded metapage.
+ atomic_inc(&mp->ref_cnt);
+ res_counter_uncharge(&mem->res, 1);
+ goto done;
+ }
+
+ atomic_set(&mp->ref_cnt, 1);
+ mp->mem_container = mem;
+ mp->page = page;
+ page_assign_meta_page(page, mp);
Would it make sense to have the "mp->page = page" be part of
page_assign_meta_page() for consistency?
+err:
+ unlock_meta_page(page);
+ return -ENOMEM;
The only jump to err: is from a location where the metapage is already
unlocked. Maybe scrap err: and just do a return -ENOMEM when the
allocation fails?
+out_uncharge:
+ mem_container_uncharge(page_get_meta_page(page));
Wanting to call mem_container_uncharge() on a page and hence having to
call page_get_meta_page() seems to be more common than wanting to call
it on a meta page that you already have available. Maybe make
mem_container_uncharge() be a wrapper that take a struct page and does
something like mem_container_uncharge_mp(page_get_meta_page(page))
where mem_container_uncharge_mp() is the raw meta-page version?
Paul
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