linux-kernel - Re: [PATCH] mm/zsmalloc: fix comment in zsmalloc

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Date:   Thu, 9 Feb 2017 12:55:16 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Yisheng Xie <xieyisheng1@...wei.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, minchan@...nel.org,
        sergey.senozhatsky@...il.com, ngupta@...are.org,
        guohanjun@...wei.com
Subject: Re: [PATCH] mm/zsmalloc: fix comment in zsmalloc

On (02/09/17 11:23), Yisheng Xie wrote:
> The class index and fullness group are not encoded in
> (first)page->mapping any more, after commit 3783689a1aa8 ("zsmalloc:
> introduce zspage structure"). Instead, they are store in struct zspage.
> 
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Cc: Nitin Gupta <ngupta@...are.org>
> Cc: Hanjun Guo <guohanjun@...wei.com>
> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>

no objections from my side.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>




a side note - may be we don't need this comment at all.
the code looks like this:

/*
 * A zspage's class index and fullness group
 * are stored in struct zspage.
 */
#define FULLNESS_BITS	2
#define CLASS_BITS	8
#define ISOLATED_BITS	3
#define MAGIC_VAL_BITS	8

struct zspage {
	struct {
		unsigned int fullness:FULLNESS_BITS;
		unsigned int class:CLASS_BITS;
		unsigned int isolated:ISOLATED_BITS;
		unsigned int magic:MAGIC_VAL_BITS;
	};
	unsigned int inuse;
	unsigned int freeobj;
	struct page *first_page;
	struct list_head list; /* fullness list */
#ifdef CONFIG_COMPACTION
	rwlock_t lock;
#endif
};


so, basically, the comment just "repeats" the next 5 lines.
but, like I said, that's just a side note.

	-ss