linux-kernel - Re: [PATCH] erofs: get rid of ->lru usage

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Message-ID: <YXWQ6p4Hlx6tGpPN@moria.home.lan>
Date:   Sun, 24 Oct 2021 12:59:22 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     linux-erofs@...ts.ozlabs.org, Chao Yu <chao@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH] erofs: get rid of ->lru usage

On Fri, Oct 22, 2021 at 05:01:20PM +0800, Gao Xiang wrote:
> Currently, ->lru is a way to arrange non-LRU pages and has some
> in-kernel users. In order to minimize noticable issues of page
> reclaim and cache thrashing under high memory presure, limited
> temporary pages were all chained with ->lru and can be reused
> during the request. However, it seems that ->lru could be removed
> when folio is landing.
> 
> Let's use page->private to chain temporary pages for now instead
> and transform EROFS formally after the topic of the folio / file
> page design is finalized.
> 
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Kent Overstreet <kent.overstreet@...il.com>
> Cc: Chao Yu <chao@...nel.org>
> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>

Would it not be an option to use an array of pointers to pages, instead of a
linked list? Arrays are faster than lists, and page->private is another thing we
prefer not to use if we don't have to.

That said - this is definitely preferable to using page->lru - thank you.

Reviewed-by: Kent Overstreet <kent.overstreet@...il.com>