linux-kernel - Re: [PATCH] zram: extra zram_get_element call in zram_read_from

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Date:   Wed, 8 Nov 2023 12:32:44 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Vasily Averin <vasily.averin@...ux.dev>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, zhouxianrong <zhouxianrong@...wei.com>
Subject: Re: [PATCH] zram: extra zram_get_element call in
 zram_read_from_zspool()

On (23/11/08 06:16), Vasily Averin wrote:
> On 11/8/23 05:49, Sergey Senozhatsky wrote:
> > On (23/11/06 22:55), Vasily Averin wrote:
> >>
> >> 'element' and 'handle' are union in struct zram_table_entry.
> >>
> >> Fixes: 8e19d540d107 ("zram: extend zero pages to same element pages")
> > 
> > Sorry, what exactly does it fix?
> 
> It removes unneeded call of zram_get_element() and unneeded variable 'value'.

Yes, what the patch does is pretty clear. It doesn't *fix* anything per se.

> zram_get_element() == zram_get_handle(), they both access the same field of the same struct zram_table_entry,
> no need to read it 2nd time. 
> 'value' variable is not required, 'handle' can be used instead.
> 
> I hope this explain why element/handle union should be removed: it confuses reviewers.

I do not agree with "union should be removed" part.

In this particular case - using handle as the page pattern (element)
is in fact quite confusing. The visual separation of `handle` and `element`
is helpful.