Re: [RFC PATCH 12/14] mm: Free folios directly in move_folios_to_lru()

[Matthew Wilcox <willy@infradead.org>]

On Thu, Aug 31, 2023 at 04:46:50PM +0100, Ryan Roberts wrote:
> On 25/08/2023 14:59, Matthew Wilcox (Oracle) wrote:
> > The few folios which can't be moved to the LRU list (because their
> > refcount dropped to zero) used to be returned to the caller to dispose
> > of.  Make this simpler to call by freeing the folios directly through
> > free_unref_folios().
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> > ---
> >  mm/vmscan.c | 31 ++++++++++++-------------------
> >  1 file changed, 12 insertions(+), 19 deletions(-)
> > 
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 965c429847fd..d5080510608e 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -2489,8 +2489,9 @@ static unsigned int move_folios_to_lru(struct lruvec *lruvec,
> >  		struct list_head *list)
> 
> The comment for this function is now stale:
> 
> /*
>  * move_folios_to_lru() moves folios from private @list to appropriate LRU list.
>  * On return, @list is reused as a list of folios to be freed by the caller.
>  *
>  * Returns the number of pages moved to the given lruvec.
>  */
> 
> I think the "On return" bit is no longer true.

It's still true, but misleading ;-)  I'll amend it to

- * On return, @list is reused as a list of folios to be freed by the caller.
+ * On return, @list is empty.