Re: [RFC][PATCH 1/8] memcg: migration handling

[Li Zefan <lizf@cn.fujitsu.com>]

KAMEZAWA Hiroyuki wrote:
[..snip..]
> Index: mm-2.6.25-mm1/mm/migrate.c
> ===================================================================
> --- mm-2.6.25-mm1.orig/mm/migrate.c
> +++ mm-2.6.25-mm1/mm/migrate.c
> @@ -357,6 +357,10 @@ static int migrate_page_move_mapping(str
>  	__inc_zone_page_state(newpage, NR_FILE_PAGES);
>  
>  	write_unlock_irq(&mapping->tree_lock);
> +	if (!PageSwapCache(newpage)) {
> +		mem_cgroup_uncharge_page(page);
> +		mem_cgroup_getref(newpage);
> +	}
>  
>  	return 0;
>  }
> @@ -603,7 +607,6 @@ static int move_to_new_page(struct page 
>  		rc = fallback_migrate_page(mapping, newpage, page);
>  
>  	if (!rc) {
> -		mem_cgroup_page_migration(page, newpage);
>  		remove_migration_ptes(page, newpage);
>  	} else
>  		newpage->mapping = NULL;
> @@ -633,6 +636,12 @@ static int unmap_and_move(new_page_t get
>  		/* page was freed from under us. So we are done. */
>  		goto move_newpage;
>  
> +	charge = mem_cgroup_prepare_migration(page, newpage);
> +	if (charge == -ENOMEM) {
> +		rc = -ENOMEM;
> +		goto move_newpage;
> +	}
> +

A BUG_ON(charge) is needed to insure the only error code from
mem_cgroup_prepare_migration() is -ENOMEM ?

>  	rc = -EAGAIN;
>  	if (TestSetPageLocked(page)) {
>  		if (!force)
> @@ -684,19 +693,14 @@ static int unmap_and_move(new_page_t get
>  		goto rcu_unlock;
>  	}
>  
> -	charge = mem_cgroup_prepare_migration(page);
>  	/* Establish migration ptes or remove ptes */
>  	try_to_unmap(page, 1);
>  
>  	if (!page_mapped(page))
>  		rc = move_to_new_page(newpage, page);
>  
> -	if (rc) {
> +	if (rc)
>  		remove_migration_ptes(page, page);
> -		if (charge)
> -			mem_cgroup_end_migration(page);
> -	} else if (charge)
> - 		mem_cgroup_end_migration(newpage);
>  rcu_unlock:
>  	if (rcu_locked)
>  		rcu_read_unlock();
> @@ -717,6 +721,8 @@ unlock:
>  	}
>  
>  move_newpage:
> +	if (!charge)
> +		mem_cgroup_end_migration(newpage);
>  	/*
>  	 * Move the new page to the LRU. If migration was not successful
>  	 * then this will free the page.
> 
> --

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