linux-kernel - Re: [PATCH] maple_tree: fix MAPLE_PARENT

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Message-ID: <a3nqea7xewezigtvnan6okktz5l27p74fquqcyuxdgtbwvogew@kbrjh2yqsdzs>
Date: Tue, 26 Aug 2025 11:24:06 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Sidhartha Kumar <sidhartha.kumar@...cle.com>
Cc: linux-kernel@...r.kernel.org, maple-tree@...ts.infradead.org,
        akpm@...ux-foundation.org, willy@...radead.org
Subject: Re: [PATCH] maple_tree: fix MAPLE_PARENT_RANGE32 and parent pointer
 docs

* Sidhartha Kumar <sidhartha.kumar@...cle.com> [250826 11:13]:
> MAPLE_PARENT_RANGE32 should be 0x02 as a 32 bit node is
> indicated by the bit pattern 0b010 which is the hex value 0x02.
> There are no users currently, so there is no associated bug with this
> wrong value.
> 
> Fix typo Note -> Node and replace x with b to indicate binary
> values.
> 
> Fixes: 54a611b60590 ("Maple Tree: add new data structure")
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@...cle.com>

Thanks!

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

> ---
>  include/linux/maple_tree.h | 16 ++++++++--------
>  lib/maple_tree.c           | 12 ++++++------
>  2 files changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/include/linux/maple_tree.h b/include/linux/maple_tree.h
> index bafe143b1f78..41e633264e51 100644
> --- a/include/linux/maple_tree.h
> +++ b/include/linux/maple_tree.h
> @@ -57,17 +57,17 @@
>   * MT_FLAGS_ALLOC_RANGE flag.
>   *
>   *  Node types:
> - *   0x??1 = Root
> - *   0x?00 = 16 bit nodes
> - *   0x010 = 32 bit nodes
> - *   0x110 = 64 bit nodes
> + *   0b??1 = Root
> + *   0b?00 = 16 bit nodes
> + *   0b010 = 32 bit nodes
> + *   0b110 = 64 bit nodes
>   *
>   *  Slot size and location in the parent pointer:
>   *   type  : slot location
> - *   0x??1 : Root
> - *   0x?00 : 16 bit values, type in 0-1, slot in 2-6
> - *   0x010 : 32 bit values, type in 0-2, slot in 3-6
> - *   0x110 : 64 bit values, type in 0-2, slot in 3-6
> + *   0b??1 : Root
> + *   0b?00 : 16 bit values, type in 0-1, slot in 2-6
> + *   0b010 : 32 bit values, type in 0-2, slot in 3-6
> + *   0b110 : 64 bit values, type in 0-2, slot in 3-6
>   */
>  
>  /*
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 38fb68c08291..d1d513bb6e95 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -405,11 +405,11 @@ static __always_inline bool mt_is_alloc(struct maple_tree *mt)
>   * a reuse of the last bit in the node type.  This is possible by using bit 1 to
>   * indicate if bit 2 is part of the type or the slot.
>   *
> - * Note types:
> - *  0x??1 = Root
> - *  0x?00 = 16 bit nodes
> - *  0x010 = 32 bit nodes
> - *  0x110 = 64 bit nodes
> + * Node types:
> + *  0b??1 = Root
> + *  0b?00 = 16 bit nodes
> + *  0b010 = 32 bit nodes
> + *  0b110 = 64 bit nodes
>   *
>   * Slot size and alignment
>   *  0b??1 : Root
> @@ -427,7 +427,7 @@ static __always_inline bool mt_is_alloc(struct maple_tree *mt)
>  #define MAPLE_PARENT_16B_SLOT_MASK	0xFC
>  
>  #define MAPLE_PARENT_RANGE64		0x06
> -#define MAPLE_PARENT_RANGE32		0x04
> +#define MAPLE_PARENT_RANGE32		0x02
>  #define MAPLE_PARENT_NOT_RANGE16	0x02
>  
>  /*
> -- 
> 2.43.0
>