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References: <20240126163032.1613731-1-yoann.congal@smile.fr>
In-Reply-To: <20240126163032.1613731-1-yoann.congal@smile.fr>
From: Masahiro Yamada <masahiroy@kernel.org>
Date: Sat, 27 Jan 2024 04:28:44 +0900
Message-ID: <CAK7LNATBvhcyQXt58j74Q++Y74ZgjdC3r3rtnAuU0YMt_K_A7g@mail.gmail.com>
Subject: Re: [PATCH] treewide: Change CONFIG_BASE_SMALL to bool type
To: Yoann Congal <yoann.congal@smile.fr>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, 
	linux-fsdevel@vger.kernel.org, linux-kbuild@vger.kernel.org, 
	Geert Uytterhoeven <geert@linux-m68k.org>, Thomas Gleixner <tglx@linutronix.de>, 
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, 
	Dave Hansen <dave.hansen@linux.intel.com>, "H. Peter Anvin" <hpa@zytor.com>, 
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Jiri Slaby <jirislaby@kernel.org>, 
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>, Matthew Wilcox <willy@infradead.org>, 
	Peter Zijlstra <peterz@infradead.org>, Darren Hart <dvhart@infradead.org>, 
	Davidlohr Bueso <dave@stgolabs.net>, =?UTF-8?Q?Andr=C3=A9_Almeida?= <andrealmeid@igalia.com>, 
	"Luis R. Rodriguez" <mcgrof@kernel.org>
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(+CC: Luis R. Rodriguez, author of 23b2899f7f194)


On Sat, Jan 27, 2024 at 1:30=E2=80=AFAM Yoann Congal <yoann.congal@smile.fr=
> wrote:
>
> CONFIG_BASE_SMALL is currently a type int but is only used as a boolean:
> CONFIG_BASE_SMALL =3D=3D 0 vs CONFIG_BASE_SMALL !=3D 0.
>
> So change it to the more logical bool type.
>
> Furthermore, recent kconfig changes (see Fixes: tags) revealed that using

Seeing the Fixes tage does not reveal this issue.

The discussion in Closes: thread explains the issue.


>   config SOMETHING
>      default "some value" if X
> does not work as expected if X is not of type bool.
>
> CONFIG_BASE_SMALL is used that way in init/Kconfig:
>   config LOG_CPU_MAX_BUF_SHIFT
>         default 12 if !BASE_SMALL
>         default 0 if BASE_SMALL


Or, an even cleaner way is to remove BASE_SMALL because it is
the same as !BASE_FULL.


    config LOG_CPU_MAX_BUF_SHIFT
           default 12 if BASE_FULL
           default 0

You also need to invert the logic in C as well.


Perhaps, it might be worth mentioning this changes
CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D12 to
CONFIG_LOG_CPU_MAX_BUF_SHIFT=3D0 for some defconfigs,
but that will not be a big impact due to this code:

 /* by default this will only continue through for large > 64 CPUs */
 if (cpu_extra <=3D __LOG_BUF_LEN / 2)
         return;


>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=3D2XUAHascps76YQ=
ac6rdnQGhc8nop_Q@mail.gmail.com/
> Fixes: 6262afa10ef7 ("kconfig: default to zero if int/hex symbol lacks de=
fault property")

This tag is not relevant.


> Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")

This is correct.


> ---
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Ingo Molnar <mingo@redhat.com>
> CC: Borislav Petkov <bp@alien8.de>
> CC: Dave Hansen <dave.hansen@linux.intel.com>
> CC: "H. Peter Anvin" <hpa@zytor.com>
> CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> CC: Jiri Slaby <jirislaby@kernel.org>
> CC: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
> CC: Matthew Wilcox <willy@infradead.org>
> CC: Peter Zijlstra <peterz@infradead.org>
> CC: Darren Hart <dvhart@infradead.org>
> CC: Davidlohr Bueso <dave@stgolabs.net>
> CC: "Andr=C3=A9 Almeida" <andrealmeid@igalia.com>
> CC: Masahiro Yamada <masahiroy@kernel.org>
> CC: x86@kernel.org
> CC: linux-kernel@vger.kernel.org
> CC: linux-serial@vger.kernel.org
> CC: linux-fsdevel@vger.kernel.org
> CC: linux-kbuild@vger.kernel.org
> ---
>  arch/x86/include/asm/mpspec.h | 2 +-
>  drivers/tty/vt/vc_screen.c    | 2 +-
>  include/linux/threads.h       | 4 ++--
>  include/linux/udp.h           | 2 +-
>  include/linux/xarray.h        | 2 +-
>  init/Kconfig                  | 6 +++---
>  kernel/futex/core.c           | 2 +-
>  kernel/user.c                 | 2 +-
>  8 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.=
h
> index 4b0f98a8d338d..ebe4b6121b698 100644
> --- a/arch/x86/include/asm/mpspec.h
> +++ b/arch/x86/include/asm/mpspec.h
> @@ -15,7 +15,7 @@ extern int pic_mode;
>   * Summit or generic (i.e. installer) kernels need lots of bus entries.
>   * Maximum 256 PCI busses, plus 1 ISA bus in each of 4 cabinets.
>   */
> -#if CONFIG_BASE_SMALL =3D=3D 0
> +#ifndef CONFIG_BASE_SMALL
>  # define MAX_MP_BUSSES         260
>  #else
>  # define MAX_MP_BUSSES         32
> diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
> index 67e2cb7c96eec..da33c6c4691c0 100644
> --- a/drivers/tty/vt/vc_screen.c
> +++ b/drivers/tty/vt/vc_screen.c
> @@ -51,7 +51,7 @@
>  #include <asm/unaligned.h>
>
>  #define HEADER_SIZE    4u
> -#define CON_BUF_SIZE (CONFIG_BASE_SMALL ? 256 : PAGE_SIZE)
> +#define CON_BUF_SIZE (IS_ENABLED(CONFIG_BASE_SMALL) ? 256 : PAGE_SIZE)
>
>  /*
>   * Our minor space:
> diff --git a/include/linux/threads.h b/include/linux/threads.h
> index c34173e6c5f18..1674a471b0b4c 100644
> --- a/include/linux/threads.h
> +++ b/include/linux/threads.h
> @@ -25,13 +25,13 @@
>  /*
>   * This controls the default maximum pid allocated to a process
>   */
> -#define PID_MAX_DEFAULT (CONFIG_BASE_SMALL ? 0x1000 : 0x8000)
> +#define PID_MAX_DEFAULT (IS_ENABLED(CONFIG_BASE_SMALL) ? 0x1000 : 0x8000=
)
>
>  /*
>   * A maximum of 4 million PIDs should be enough for a while.
>   * [NOTE: PID/TIDs are limited to 2^30 ~=3D 1 billion, see FUTEX_TID_MAS=
K.]
>   */
> -#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
> +#define PID_MAX_LIMIT (IS_ENABLED(CONFIG_BASE_SMALL) ? PAGE_SIZE * 8 : \
>         (sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))
>
>  /*
> diff --git a/include/linux/udp.h b/include/linux/udp.h
> index d04188714dca1..b456417fb4515 100644
> --- a/include/linux/udp.h
> +++ b/include/linux/udp.h
> @@ -24,7 +24,7 @@ static inline struct udphdr *udp_hdr(const struct sk_bu=
ff *skb)
>  }
>
>  #define UDP_HTABLE_SIZE_MIN_PERNET     128
> -#define UDP_HTABLE_SIZE_MIN            (CONFIG_BASE_SMALL ? 128 : 256)
> +#define UDP_HTABLE_SIZE_MIN            (IS_ENABLED(CONFIG_BASE_SMALL) ? =
128 : 256)
>  #define UDP_HTABLE_SIZE_MAX            65536
>
>  static inline u32 udp_hashfn(const struct net *net, u32 num, u32 mask)
> diff --git a/include/linux/xarray.h b/include/linux/xarray.h
> index cb571dfcf4b16..3f81ee5f9fb9c 100644
> --- a/include/linux/xarray.h
> +++ b/include/linux/xarray.h
> @@ -1141,7 +1141,7 @@ static inline void xa_release(struct xarray *xa, un=
signed long index)
>   * doubled the number of slots per node, we'd get only 3 nodes per 4kB p=
age.
>   */
>  #ifndef XA_CHUNK_SHIFT
> -#define XA_CHUNK_SHIFT         (CONFIG_BASE_SMALL ? 4 : 6)
> +#define XA_CHUNK_SHIFT         (IS_ENABLED(CONFIG_BASE_SMALL) ? 4 : 6)
>  #endif
>  #define XA_CHUNK_SIZE          (1UL << XA_CHUNK_SHIFT)
>  #define XA_CHUNK_MASK          (XA_CHUNK_SIZE - 1)
> diff --git a/init/Kconfig b/init/Kconfig
> index 8d4e836e1b6b1..766a7ac8c5ea4 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1941,9 +1941,9 @@ config RT_MUTEXES
>         default y if PREEMPT_RT
>
>  config BASE_SMALL
> -       int
> -       default 0 if BASE_FULL
> -       default 1 if !BASE_FULL
> +       bool
> +       default n if BASE_FULL
> +       default y if !BASE_FULL
>
>  config MODULE_SIG_FORMAT
>         def_bool n
> diff --git a/kernel/futex/core.c b/kernel/futex/core.c
> index e0e853412c158..5f7aa4fc2f9ee 100644
> --- a/kernel/futex/core.c
> +++ b/kernel/futex/core.c
> @@ -1141,7 +1141,7 @@ static int __init futex_init(void)
>         unsigned int futex_shift;
>         unsigned long i;
>
> -#if CONFIG_BASE_SMALL
> +#ifdef CONFIG_BASE_SMALL
>         futex_hashsize =3D 16;
>  #else
>         futex_hashsize =3D roundup_pow_of_two(256 * num_possible_cpus());
> diff --git a/kernel/user.c b/kernel/user.c
> index 03cedc366dc9e..aa1162deafe49 100644
> --- a/kernel/user.c
> +++ b/kernel/user.c
> @@ -88,7 +88,7 @@ EXPORT_SYMBOL_GPL(init_user_ns);
>   * when changing user ID's (ie setuid() and friends).
>   */
>
> -#define UIDHASH_BITS   (CONFIG_BASE_SMALL ? 3 : 7)
> +#define UIDHASH_BITS   (IS_ENABLED(CONFIG_BASE_SMALL) ? 3 : 7)
>  #define UIDHASH_SZ     (1 << UIDHASH_BITS)
>  #define UIDHASH_MASK           (UIDHASH_SZ - 1)
>  #define __uidhashfn(uid)       (((uid >> UIDHASH_BITS) + uid) & UIDHASH_=
MASK)
> --
> 2.39.2
>


--=20
Best Regards
Masahiro Yamada