On Thu, Dec 05, 2024 at 05:49:38PM +0000, Matthew Wilcox (Oracle) wrote:
> From: Alex Shi <alexs@xxxxxxxxxx>
>
> The 1st patch introduces new memory descriptor zpdesc and rename
> zspage.first_page to zspage.first_zpdesc, no functional change.
>
> We removed PG_owner_priv_1 since it was moved to zspage after
> commit a41ec880aa7b ("zsmalloc: move huge compressed obj from
> page to zspage").
>
> Originally-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
> Signed-off-by: Alex Shi <alexs@xxxxxxxxxx>
> ---
> mm/zpdesc.h | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++
> mm/zsmalloc.c | 9 ++++---
> 2 files changed, 74 insertions(+), 4 deletions(-)
> create mode 100644 mm/zpdesc.h
>
> diff --git a/mm/zpdesc.h b/mm/zpdesc.h
> new file mode 100644
> index 000000000000..9ad232774469
> --- /dev/null
> +++ b/mm/zpdesc.h
> @@ -0,0 +1,69 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* zpdesc.h: zswap.zpool memory descriptor
> + *
> + * Written by Alex Shi <alexs@xxxxxxxxxx>
> + * Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
> + */
> +#ifndef __MM_ZPDESC_H__
> +#define __MM_ZPDESC_H__
> +
> +/*
> + * struct zpdesc - Memory descriptor for zpool memory
> + * @flags: Page flags, mostly unused.
> + * @lru: Indirectly used by page migration
> + * @movable_ops: Used by page migration
> + * @next: Next zpdesc in a zspage in zsmalloc zpool
> + * @handle: For huge zspage in zsmalloc zpool
> + * @zspage: Points to the zspage this zpdesc is a part of
> + * @first_obj_offset: First object offset in zsmalloc zpool
> + * @_refcount: Indirectly used by page migration
> + * @memcg_data: Memory Control Group data.
It seems you forgot to remove the comment about memcg_data?
No strong opinion about memcg_data from me, tbh.
> + *
> + * This struct overlays struct page for now. Do not modify without a good
> + * understanding of the issues. In particular, do not expand into
> + * the overlap with memcg_data.
> + *
> + * Page flags used:
> + * * PG_private identifies the first component page
> + * * PG_locked is used by page migration code
> + */
> +struct zpdesc {
> + unsigned long flags;
> + struct list_head lru;
> + unsigned long movable_ops;
> + union {
> + struct zpdesc *next;
> + unsigned long handle;
> + };
> + struct zspage *zspage;
> + unsigned int first_obj_offset;
> + atomic_t _refcount;
> +};
> +#define ZPDESC_MATCH(pg, zp) \
> + static_assert(offsetof(struct page, pg) == offsetof(struct zpdesc, zp))
> +
> +ZPDESC_MATCH(flags, flags);
> +ZPDESC_MATCH(lru, lru);
> +ZPDESC_MATCH(mapping, movable_ops);
> +ZPDESC_MATCH(index, next);
> +ZPDESC_MATCH(index, handle);
> +ZPDESC_MATCH(private, zspage);
> +ZPDESC_MATCH(page_type, first_obj_offset);
> +ZPDESC_MATCH(_refcount, _refcount);
> +#undef ZPDESC_MATCH
> +static_assert(sizeof(struct zpdesc) <= sizeof(struct page));
