Re: [PATCH v3 7/7] mm/mm_init: Use for_each_valid_pfn() in init_unavailable_range()

[Mike Rapoport <rppt@kernel.org>]

On Wed, Apr 23, 2025 at 08:52:49AM +0100, David Woodhouse wrote:
> From: David Woodhouse <dwmw@amazon.co.uk>
> 
> Currently, memmap_init initializes pfn_hole with 0 instead of
> ARCH_PFN_OFFSET. Then init_unavailable_range will start iterating each
> page from the page at address zero to the first available page, but it
> won't do anything for pages below ARCH_PFN_OFFSET because pfn_valid
> won't pass.
> 
> If ARCH_PFN_OFFSET is very large (e.g., something like 2^64-2GiB if the
> kernel is used as a library and loaded at a very high address), the
> pointless iteration for pages below ARCH_PFN_OFFSET will take a very
> long time, and the kernel will look stuck at boot time.
> 
> Use for_each_valid_pfn() to skip the pointless iterations.
> 
> Reported-by: Ruihan Li <lrh2000@pku.edu.cn>
> Suggested-by: Mike Rapoport <rppt@kernel.org>
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

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

> ---
>  mm/mm_init.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 

-- 
Sincerely yours,
Mike.