linux-kernel - Re: [PATCH v1] mm/mm_init: Fix hash table order logging in alloc_large_system

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Message-ID: <dcceca48-bbdc-4318-8c07-94bb7c2f75ff@redhat.com>
Date: Wed, 29 Oct 2025 11:03:18 +0100
From: David Hildenbrand <david@...hat.com>
To: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>,
 Mike Rapoport <rppt@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc: stable@...r.kernel.org, kernel-team@...roid.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] mm/mm_init: Fix hash table order logging in
 alloc_large_system_hash()

On 28.10.25 20:10, Isaac J. Manjarres wrote:
> When emitting the order of the allocation for a hash table,
> alloc_large_system_hash() unconditionally subtracts PAGE_SHIFT from
> log base 2 of the allocation size. This is not correct if the
> allocation size is smaller than a page, and yields a negative value
> for the order as seen below:
> 
> TCP established hash table entries: 32 (order: -4, 256 bytes, linear)
> TCP bind hash table entries: 32 (order: -2, 1024 bytes, linear)
> 
> Use get_order() to compute the order when emitting the hash table
> information to correctly handle cases where the allocation size is
> smaller than a page:
> 
> TCP established hash table entries: 32 (order: 0, 256 bytes, linear)
> TCP bind hash table entries: 32 (order: 0, 1024 bytes, linear)
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@...r.kernel.org # v5.4+

This is a pr_info(), why do you think this is stable material? Just 
curious, intuitively I'd have said that it's not that critical.

> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
> ---
>   mm/mm_init.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 3db2dea7db4c..7712d887b696 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -2469,7 +2469,7 @@ void *__init alloc_large_system_hash(const char *tablename,
>   		panic("Failed to allocate %s hash table\n", tablename);
>   
>   	pr_info("%s hash table entries: %ld (order: %d, %lu bytes, %s)\n",
> -		tablename, 1UL << log2qty, ilog2(size) - PAGE_SHIFT, size,
> +		tablename, 1UL << log2qty, get_order(size), size,

So in case it's smaller than a page we now correctly return "0".

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers

David / dhildenb