linux-kernel - Re: [PATCH] z3fold: fix memory leak in kmem cache

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Date:   Thu, 19 Sep 2019 09:59:07 +0200
From:   Vitaly Wool <vitalywool@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Streetman <ddstreet@...e.org>,
        Markus Linnala <markus.linnala@...il.com>, stable@...nel.org
Subject: Re: [PATCH] z3fold: fix memory leak in kmem cache

On Wed, Sep 18, 2019 at 9:35 AM Vlastimil Babka <vbabka@...e.cz> wrote:
>
> On 9/17/19 5:53 PM, Vitaly Wool wrote:
> > Currently there is a leak in init_z3fold_page() -- it allocates
> > handles from kmem cache even for headless pages, but then they are
> > never used and never freed, so eventually kmem cache may get
> > exhausted. This patch provides a fix for that.
> >
> > Reported-by: Markus Linnala <markus.linnala@...il.com>
> > Signed-off-by: Vitaly Wool <vitalywool@...il.com>
>
> Can a Fixes: commit be pinpointed, and CC stable added?

Fixes: 7c2b8baa61fe578 "mm/z3fold.c: add structure for buddy handles"

Best regards,
   Vitaly

> > ---
> >  mm/z3fold.c | 15 +++++++++------
> >  1 file changed, 9 insertions(+), 6 deletions(-)
> >
> > diff --git a/mm/z3fold.c b/mm/z3fold.c
> > index 6397725b5ec6..7dffef2599c3 100644
> > --- a/mm/z3fold.c
> > +++ b/mm/z3fold.c
> > @@ -301,14 +301,11 @@ static void z3fold_unregister_migration(struct z3fold_pool *pool)
> >   }
> >
> >  /* Initializes the z3fold header of a newly allocated z3fold page */
> > -static struct z3fold_header *init_z3fold_page(struct page *page,
> > +static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
> >                                       struct z3fold_pool *pool, gfp_t gfp)
> >  {
> >       struct z3fold_header *zhdr = page_address(page);
> > -     struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp);
> > -
> > -     if (!slots)
> > -             return NULL;
> > +     struct z3fold_buddy_slots *slots;
> >
> >       INIT_LIST_HEAD(&page->lru);
> >       clear_bit(PAGE_HEADLESS, &page->private);
> > @@ -316,6 +313,12 @@ static struct z3fold_header *init_z3fold_page(struct page *page,
> >       clear_bit(NEEDS_COMPACTING, &page->private);
> >       clear_bit(PAGE_STALE, &page->private);
> >       clear_bit(PAGE_CLAIMED, &page->private);
> > +     if (headless)
> > +             return zhdr;
> > +
> > +     slots = alloc_slots(pool, gfp);
> > +     if (!slots)
> > +             return NULL;
> >
> >       spin_lock_init(&zhdr->page_lock);
> >       kref_init(&zhdr->refcount);
> > @@ -962,7 +965,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
> >       if (!page)
> >               return -ENOMEM;
> >
> > -     zhdr = init_z3fold_page(page, pool, gfp);
> > +     zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
> >       if (!zhdr) {
> >               __free_page(page);
> >               return -ENOMEM;
> >
>