linux-kernel - Re: [PATCH] zsmalloc: remove obj

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Message-ID: <CAKEwX=NRS0wa1NToNyA2=F_D3pK5BLeV7Up6PJUpag=Dy8psdQ@mail.gmail.com>
Date:   Sat, 8 Jul 2023 20:17:38 -0700
From:   Nhat Pham <nphamcs@...il.com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] zsmalloc: remove obj_tagged()

On Sat, Jul 8, 2023 at 7:58 PM Sergey Senozhatsky
<senozhatsky@...omium.org> wrote:
>
> obj_tagged() is not needed at this point, because objects can
> only have one tag: OBJ_ALLOCATED_TAG. We needed obj_tagged()
> for the zsmalloc LRU implementation, which has now been
> removed. Simplify zsmalloc code and revert to the previous
> implementation that was in place before the zsmalloc LRU series.
>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
>  mm/zsmalloc.c | 29 +++++++----------------------
>  1 file changed, 7 insertions(+), 22 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 84beadc088b8..32f5bc4074df 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -795,8 +795,8 @@ static unsigned long handle_to_obj(unsigned long handle)
>         return *(unsigned long *)handle;
>  }
>
> -static bool obj_tagged(struct page *page, void *obj, unsigned long *phandle,
> -               int tag)
> +static inline bool obj_allocated(struct page *page, void *obj,
> +                                unsigned long *phandle)
>  {
>         unsigned long handle;
>         struct zspage *zspage = get_zspage(page);
> @@ -807,7 +807,7 @@ static bool obj_tagged(struct page *page, void *obj, unsigned long *phandle,
>         } else
>                 handle = *(unsigned long *)obj;
>
> -       if (!(handle & tag))
> +       if (!(handle & OBJ_ALLOCATED_TAG))
>                 return false;
>
>         /* Clear all tags before returning the handle */
> @@ -815,11 +815,6 @@ static bool obj_tagged(struct page *page, void *obj, unsigned long *phandle,
>         return true;
>  }
>
> -static inline bool obj_allocated(struct page *page, void *obj, unsigned long *phandle)
> -{
> -       return obj_tagged(page, obj, phandle, OBJ_ALLOCATED_TAG);
> -}
> -
>  static void reset_page(struct page *page)
>  {
>         __ClearPageMovable(page);
> @@ -1551,11 +1546,11 @@ static void zs_object_copy(struct size_class *class, unsigned long dst,
>  }
>
>  /*
> - * Find object with a certain tag in zspage from index object and
> + * Find alloced object in zspage from index object and
>   * return handle.
>   */
> -static unsigned long find_tagged_obj(struct size_class *class,
> -                                       struct page *page, int *obj_idx, int tag)
> +static unsigned long find_alloced_obj(struct size_class *class,
> +                                     struct page *page, int *obj_idx)
>  {
>         unsigned int offset;
>         int index = *obj_idx;
> @@ -1566,7 +1561,7 @@ static unsigned long find_tagged_obj(struct size_class *class,
>         offset += class->size * index;
>
>         while (offset < PAGE_SIZE) {
> -               if (obj_tagged(page, addr + offset, &handle, tag))
> +               if (obj_allocated(page, addr + offset, &handle))
>                         break;
>
>                 offset += class->size;
> @@ -1580,16 +1575,6 @@ static unsigned long find_tagged_obj(struct size_class *class,
>         return handle;
>  }
>
> -/*
> - * Find alloced object in zspage from index object and
> - * return handle.
> - */
> -static unsigned long find_alloced_obj(struct size_class *class,
> -                                       struct page *page, int *obj_idx)
> -{
> -       return find_tagged_obj(class, page, obj_idx, OBJ_ALLOCATED_TAG);
> -}
> -
>  static void migrate_zspage(struct zs_pool *pool, struct zspage *src_zspage,
>                            struct zspage *dst_zspage)
>  {
> --
> 2.41.0.255.g8b1d071c50-goog
>
>

LGTM! This was only introduced for the (temporary) deferred tag.
We've removed it so this should go away too.

Acked-by: Nhat Pham <nphamcs@...il.com>