Re: [PATCH 0/4] mm: Use slab_list list_head instead of lru

[Tobin C. Harding]

On Mon, Mar 11, 2019 at 04:16:33PM -0700, Matthew Wilcox wrote:
> On Mon, Mar 11, 2019 at 08:49:23PM +0000, Roman Gushchin wrote:
> > The patchset looks good to me, however I'd add some clarifications
> > why switching from lru to slab_list is safe.
> > 
> > My understanding is that the slab_list fields isn't currently in use,
> > but it's not that obvious that putting slab_list and next/pages/pobjects
> > fields into a union is safe (for the slub case).
> 
> It's already in a union.
> 
> struct page {
>         union {
>                 struct {        /* Page cache and anonymous pages */
>                         struct list_head lru;
> ...
>                 struct {        /* slab, slob and slub */
>                         union {
>                                 struct list_head slab_list;     /* uses lru */
>                                 struct {        /* Partial pages */
>                                         struct page *next;
> 
> slab_list and lru are in the same bits.  Once this patch set is in,
> we can remove the enigmatic 'uses lru' comment that I added.

Funny you should say this, I came to me today while daydreaming that I
should have removed that comment :)

I'll remove it in v2.

thanks,
Tobin.