linux-kernel - Re: [PATCH v9 4/9] memblock: Unpreserve memory in case of error

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Message-ID: <aQb_bJ2et5rO0k5q@kernel.org>
Date: Sun, 2 Nov 2025 08:51:24 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: akpm@...ux-foundation.org, brauner@...nel.org, corbet@....net,
	graf@...zon.com, jgg@...pe.ca, linux-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
	masahiroy@...nel.org, ojeda@...nel.org, pratyush@...nel.org,
	rdunlap@...radead.org, tj@...nel.org, yanjun.zhu@...ux.dev
Subject: Re: [PATCH v9 4/9] memblock: Unpreserve memory in case of error

On Sat, Nov 01, 2025 at 10:23:20AM -0400, Pasha Tatashin wrote:
> If there is an error half way through KHO memory preservation, we should
> rollback and unpreserve everything that is partially preserved.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> Suggested-by: Pratyush Yadav <pratyush@...nel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

with a small nit below.

> ---
>  mm/memblock.c | 73 ++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 58 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index e3bef9b35d63..f527ad1ca682 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -2445,29 +2445,60 @@ int reserve_mem_release_by_name(const char *name)

...

>  static int __init prepare_kho_fdt(void)
>  {
> -	int err = 0, i;
>  	struct page *fdt_page;
>  	void *fdt;
> +	int err;
>  
>  	fdt_page = alloc_page(GFP_KERNEL);
> -	if (!fdt_page)
> -		return -ENOMEM;
> +	if (!fdt_page) {
> +		err = -ENOMEM;
> +		goto err_no_fdt_page;

Please rename the label to describe what the goto does, say, err_report.
I believe it can be a fixup on top after Andrew merges these.

...

> +err_remove_subtree:
> +	kho_remove_subtree(fdt);
> +err_unpreserve_fdt:
> +	kho_unpreserve_pages(fdt_page, 1);
> +err_free_fdt:
> +	put_page(fdt_page);
> +err_no_fdt_page:
> +	pr_err("failed to prepare memblock FDT for KHO: %d\n", err);
>  
>  	return err;
>  }
> -- 
> 2.51.1.930.gacf6e81ea2-goog
> 

-- 
Sincerely yours,
Mike.