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

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Message-ID: <aQH-TewXFLUsK3nN@kernel.org>
Date: Wed, 29 Oct 2025 13:45:17 +0200
From: Mike Rapoport <rppt@...nel.org>
To: "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 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 Tue, Oct 28, 2025 at 12:10:12PM -0700, 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+
> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>

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

> ---
>  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,
>  		virt ? (huge ? "vmalloc hugepage" : "vmalloc") : "linear");
>  
>  	if (_hash_shift)
> -- 
> 2.51.1.851.g4ebd6896fd-goog
> 

-- 
Sincerely yours,
Mike.