Re: [PATCH] [RFC] maple_tree: reduce stack usage with gcc-9 and earlier

["Liam R. Howlett" <Liam.Howlett@Oracle.com>]

* Arnd Bergmann <arnd@kernel.org> [230214 05:30]:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> gcc-10 changed the way inlining works to be less aggressive, but
> older versions run into an oversized stack frame warning whenever
> CONFIG_KASAN_STACK is enabled, as that forces variables from
> inlined callees to be non-overlapping:
> 
> lib/maple_tree.c: In function 'mas_wr_bnode':
> lib/maple_tree.c:4320:1: error: the frame size of 1424 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
> 
> Change the annotations on mas_store_b_node() and mas_commit_b_node()
> to explicitly forbid inlining in this configuration, which is
> the same behavior that newer versions already have.
> 
> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Cc: kasan-dev@googlegroups.com
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  lib/maple_tree.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index 5e9703189259..646297cae5d1 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -146,6 +146,13 @@ struct maple_subtree_state {
>  	struct maple_big_node *bn;
>  };
>  
> +#ifdef CONFIG_KASAN_STACK
> +/* Prevent mas_wr_bnode() from exceeding the stack frame limit */

nit: Should there be more info in here?  You did add it to two functions
and it's a problem for frame-larger-than=1024

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


> +#define noinline_for_kasan noinline_for_stack
> +#else
> +#define noinline_for_kasan inline
> +#endif
> +
>  /* Functions */
>  static inline struct maple_node *mt_alloc_one(gfp_t gfp)
>  {
> @@ -2107,7 +2114,7 @@ static inline void mas_bulk_rebalance(struct ma_state *mas, unsigned char end,
>   *
>   * Return: The actual end of the data stored in @b_node
>   */
> -static inline void mas_store_b_node(struct ma_wr_state *wr_mas,
> +static noinline_for_kasan void mas_store_b_node(struct ma_wr_state *wr_mas,
>  		struct maple_big_node *b_node, unsigned char offset_end)
>  {
>  	unsigned char slot;
> @@ -3579,7 +3586,7 @@ static inline bool mas_reuse_node(struct ma_wr_state *wr_mas,
>   * @b_node: The maple big node
>   * @end: The end of the data.
>   */
> -static inline int mas_commit_b_node(struct ma_wr_state *wr_mas,
> +static noinline_for_kasan int mas_commit_b_node(struct ma_wr_state *wr_mas,
>  			    struct maple_big_node *b_node, unsigned char end)
>  {
>  	struct maple_node *node;
> -- 
> 2.39.1
>