linux-kernel - Re: [PATCH v2 2/4] mm: change to return bool for isolate_lru

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Message-Id: <20230214193204.72057-1-sj@kernel.org>
Date:   Tue, 14 Feb 2023 19:32:04 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        sj@...nel.org, hannes@...xchg.org, mhocko@...nel.org,
        roman.gushchin@...ux.dev, shakeelb@...gle.com,
        muchun.song@...ux.dev, naoya.horiguchi@....com,
        linmiaohe@...wei.com, david@...hat.com, osalvador@...e.de,
        mike.kravetz@...cle.com, willy@...radead.org,
        damon@...ts.linux.dev, cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] mm: change to return bool for isolate_lru_page()

On Tue, 14 Feb 2023 21:59:30 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:

> The isolate_lru_page() can only return 0 or -EBUSY, and most users did
> not care about the negative error of isolate_lru_page(), except one user
> in add_page_for_migration(). So we can convert the isolate_lru_page() to
> return a boolean value, which can help to make the code more clear when
> checking the return value of isolate_lru_page().
> 
> Also convert all users' logic of checking the isolation state.
> 
> No functional changes intended.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  mm/folio-compat.c   | 12 +++---------
>  mm/internal.h       |  2 +-
>  mm/khugepaged.c     |  2 +-
>  mm/memcontrol.c     |  4 ++--
>  mm/memory-failure.c |  4 ++--
>  mm/memory_hotplug.c |  2 +-
>  mm/migrate.c        |  9 ++++++---
>  mm/migrate_device.c |  2 +-
>  8 files changed, 17 insertions(+), 20 deletions(-)
> 
[...]
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index a1e8c3e9ab08..17ed80707518 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1668,7 +1668,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
>  		 * LRU and non-lru movable pages.
>  		 */
>  		if (PageLRU(page))
> -			ret = isolate_lru_page(page);
> +			ret = !isolate_lru_page(page);

This may change return value of this function.  That is, this function will
return 1 instead of -EBUSY after this change.  It's not a real issue as no
caller of this function takes care of the return value, though.


Thanks,
SJ

>  		else
>  			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
>  		if (!ret) { /* Success */
[...]