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From: SeongJae Park <sj@kernel.org>
To: Barry Song <21cnbao@gmail.com>
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Subject: Re: [PATCH v2 1/5] mm: swap: introduce swap_free_nr() for batched swap_free()
Date: Wed, 10 Apr 2024 16:37:59 -0700
Message-Id: <20240410233759.274907-1-sj@kernel.org>
In-Reply-To: <20240409082631.187483-2-21cnbao@gmail.com>
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Hi Barry,

On Tue,  9 Apr 2024 20:26:27 +1200 Barry Song <21cnbao@gmail.com> wrote:

> From: Chuanhua Han <hanchuanhua@oppo.com>
> 
> While swapping in a large folio, we need to free swaps related to the whole
> folio. To avoid frequently acquiring and releasing swap locks, it is better
> to introduce an API for batched free.
> 
> Signed-off-by: Chuanhua Han <hanchuanhua@oppo.com>
> Co-developed-by: Barry Song <v-songbaohua@oppo.com>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> ---
>  include/linux/swap.h |  5 +++++
>  mm/swapfile.c        | 51 ++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 11c53692f65f..b7a107e983b8 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
[...]
> +void swap_free_nr(swp_entry_t entry, int nr_pages)
> +{
> +}

I found the latest mm-unstable fails build when CONFIG_SWAP is not set with
errors including below, and 'git bisect' points this patch.

    do_mounts.c:(.text+0x6): multiple definition of `swap_free_nr'; init/main.o:main.c:(.text+0x9c): first defined here

I think this should be defined as 'static inline'?  I confirmed adding the two
keywords as below fixes the build failure.

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 4bf5090de0fd..5fd60d733ba8 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -562,7 +562,7 @@ static inline void swap_free(swp_entry_t swp)
 {
 }

-void swap_free_nr(swp_entry_t entry, int nr_pages)
+static inline void swap_free_nr(swp_entry_t entry, int nr_pages)
 {
 }


Thanks,
SJ

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