mem_cgroup_lru_del_before_commit_swapcache() seems broken

mem_cgroup_lru_del_before_commit_swapcache() seems broken

[Balbir Singh]

Hi, Kame,

mem_cgroup_lru_del_before_commit_swapcache() seems to be broken, here
is why


static void mem_cgroup_lru_del_before_commit_swapcache(struct page
*page)
{
        unsigned long flags;
        struct zone *zone = page_zone(page);
        struct page_cgroup *pc = lookup_page_cgroup(page);

        spin_lock_irqsave(&zone->lru_lock, flags);
        /*
         * Forget old LRU when this page_cgroup is *not* used. This
         * Used bit
         * is guarded by lock_page() because the page is SwapCache.
         */
        if (!PageCgroupUsed(pc))
                mem_cgroup_del_lru_list(page, page_lru(page));

...
...
void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
{
        struct page_cgroup *pc;
        struct mem_cgroup *mem;
        struct mem_cgroup_per_zone *mz;

        if (mem_cgroup_disabled())
                return;
        pc = lookup_page_cgroup(page);
        /* can happen while we handle swapcache. */
        if (!PageCgroupUsed(pc))
                return;


In mem_cgroup_lru_del_before_commit_swapcache() we say
        if (!PageCgroupused(pc))
                mem_cgroup_del_lru_list()

in mem_cgroup_del_lru_list() we say
        if (!PageCgroupUsed(pc))
                return;

So why call mem_cgroup_del_lru_list() at all? Am I missing something.

-- 
	Balbir

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Re: mem_cgroup_lru_del_before_commit_swapcache() seems broken

[Balbir Singh]

* Balbir Singh <balbir@linux.vnet.ibm.com> [2009-05-14 22:20:45]:

> Hi, Kame,
> 
> mem_cgroup_lru_del_before_commit_swapcache() seems to be broken, here
> is why
> 
> 
> static void mem_cgroup_lru_del_before_commit_swapcache(struct page
> *page)
> {
>         unsigned long flags;
>         struct zone *zone = page_zone(page);
>         struct page_cgroup *pc = lookup_page_cgroup(page);
> 
>         spin_lock_irqsave(&zone->lru_lock, flags);
>         /*
>          * Forget old LRU when this page_cgroup is *not* used. This
>          * Used bit
>          * is guarded by lock_page() because the page is SwapCache.
>          */
>         if (!PageCgroupUsed(pc))
>                 mem_cgroup_del_lru_list(page, page_lru(page));
> 
> ...
> ...
> void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
> {
>         struct page_cgroup *pc;
>         struct mem_cgroup *mem;
>         struct mem_cgroup_per_zone *mz;
> 
>         if (mem_cgroup_disabled())
>                 return;
>         pc = lookup_page_cgroup(page);
>         /* can happen while we handle swapcache. */
>         if (!PageCgroupUsed(pc))
>                 return;
> 
> 
> In mem_cgroup_lru_del_before_commit_swapcache() we say
>         if (!PageCgroupused(pc))
>                 mem_cgroup_del_lru_list()
> 
> in mem_cgroup_del_lru_list() we say
>         if (!PageCgroupUsed(pc))
>                 return;
> 
> So why call mem_cgroup_del_lru_list() at all? Am I missing something.
>

Please ignore, looks like a badly applied diff, let the change over in
my sources. Sorry for the noise 

-- 
	Balbir

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