linux-kernel - Re: [PATCH v2 02/23] vmw_balloon: remove vmballoon_compaction

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Message-ID: <7a6d15b1-0273-44ba-95d2-35533320bc09@lucifer.local>
Date: Thu, 15 Jan 2026 11:20:41 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org,
        Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
        linux-doc@...r.kernel.org, virtualization@...ts.linux.dev,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Jonathan Corbet <corbet@....net>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jerrin Shaji George <jerrin.shaji-george@...adcom.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Eugenio Pérez <eperezma@...hat.com>,
        Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH v2 02/23] vmw_balloon: remove vmballoon_compaction_init()

On Thu, Jan 15, 2026 at 10:19:52AM +0100, David Hildenbrand (Red Hat) wrote:
> Now that there is not a lot of logic left, let's just inline setting up
> the migration function and drop all these excessive comments that are
> not really required (or true) anymore.
>
> To avoid #ifdef in the caller we can instead use IS_ENABLED() and make
> the compiler happy by only providing the function declaration.
>
> Signed-off-by: David Hildenbrand (Red Hat) <david@...nel.org>

Seems reasonable to me, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  drivers/misc/vmw_balloon.c | 30 +++++-------------------------
>  1 file changed, 5 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
> index 2cc34c4968fac..07e60a4b846aa 100644
> --- a/drivers/misc/vmw_balloon.c
> +++ b/drivers/misc/vmw_balloon.c
> @@ -1833,27 +1833,10 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
>  	up_read(&b->conf_sem);
>  	return ret;
>  }
> -
> -/**
> - * vmballoon_compaction_init() - initialized compaction for the balloon.
> - *
> - * @b: pointer to the balloon.
> - *
> - * If during the initialization a failure occurred, this function does not
> - * perform cleanup. The caller must call vmballoon_compaction_deinit() in this
> - * case.
> - *
> - * Return: zero on success or error code on failure.
> - */
> -static __init void vmballoon_compaction_init(struct vmballoon *b)
> -{
> -	b->b_dev_info.migratepage = vmballoon_migratepage;
> -}
> -
>  #else /* CONFIG_BALLOON_COMPACTION */
> -static inline void vmballoon_compaction_init(struct vmballoon *b)
> -{
> -}
> +int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
> +			  struct page *newpage, struct page *page,
> +			  enum migrate_mode mode);
>  #endif /* CONFIG_BALLOON_COMPACTION */
>
>  static int __init vmballoon_init(void)
> @@ -1873,12 +1856,9 @@ static int __init vmballoon_init(void)
>  	if (error)
>  		return error;
>
> -	/*
> -	 * Initialization of compaction must be done after the call to
> -	 * balloon_devinfo_init() .
> -	 */
>  	balloon_devinfo_init(&balloon.b_dev_info);
> -	vmballoon_compaction_init(&balloon);
> +	if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
> +		balloon.b_dev_info.migratepage = vmballoon_migratepage;
>
>  	INIT_LIST_HEAD(&balloon.huge_pages);
>  	spin_lock_init(&balloon.comm_lock);
> --
> 2.52.0
>