[PATCH v3 0/2] printk: CONFIG_BASE_SMALL fix for LOG_CPU_MAX_BUF_SHIFT and removal

[PATCH v3 0/2] printk: CONFIG_BASE_SMALL fix for LOG_CPU_MAX_BUF_SHIFT and removal

[Yoann Congal]

This series focuses on CONFIG_BASE_SMALL.
The first patch fixes LOG_CPU_MAX_BUF_SHIFT when CONFIG_BASE_SMALL is
used.
The second patch globally replace CONFIG_BASE_SMALL usages by the
equivalent !CONFIG_BASE_FULL.

Patch history:
v2 -> v3: Applied Luis Chamberlain's comments (Thanks!):
* Split the single commit in two : one functional fix, one global
  removal.

v2 patch was named "printk: Remove redundant CONFIG_BASE_SMALL"
https://lore.kernel.org/all/20240127220026.1722399-1-yoann.congal@smile.fr/
* Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
* Reviewed-by: John Ogness <john.ogness@linutronix.de>

v1 -> v2: Applied Masahiro Yamada's comments (Thanks!):
* Changed from "Change CONFIG_BASE_SMALL to type bool" to
  "Remove it and switch usage to !CONFIG_BASE_FULL"
* Fixed "Fixes:" tag and reference to the mailing list thread.
* Added a note about CONFIG_LOG_CPU_MAX_BUF_SHIFT changing.

v1 patch was named "treewide: Change CONFIG_BASE_SMALL to bool type"
https://lore.kernel.org/all/20240126163032.1613731-1-yoann.congal@smile.fr/

Yoann Congal (2):
  printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled
  printk: Remove redundant CONFIG_BASE_SMALL

 arch/x86/include/asm/mpspec.h | 2 +-
 drivers/tty/vt/vc_screen.c    | 2 +-
 include/linux/threads.h       | 6 +++---
 include/linux/udp.h           | 2 +-
 include/linux/xarray.h        | 2 +-
 init/Kconfig                  | 9 ++-------
 kernel/futex/core.c           | 6 +++---
 kernel/user.c                 | 2 +-
 8 files changed, 13 insertions(+), 18 deletions(-)

-- 
2.39.2

[PATCH v3 1/2] printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled

[Yoann Congal]

LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL:
  config LOG_CPU_MAX_BUF_SHIFT
  	default 12 if !BASE_SMALL
  	default 0 if BASE_SMALL
But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always
evaluated to true whatever is the value of BASE_SMALL.

This patch fixes this by using BASE_FULL (type bool) which is equivalent
to BASE_SMALL==0.

Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to
CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will
not be a big impact due to this code in kernel/printk/printk.c:
  /* by default this will only continue through for large > 64 CPUs */
  if (cpu_extra <= __LOG_BUF_LEN / 2)
          return;
Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite
rare.

John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote:
> For printk this will mean that BASE_SMALL systems were probably
> previously allocating/using the dynamic ringbuffer and now they will
> just continue to use the static ringbuffer. Which is fine and saves
> memory (as it should).

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/
Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")
---
 init/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index deda3d14135bb..73efb76f38734 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -734,8 +734,8 @@ config LOG_CPU_MAX_BUF_SHIFT
 	int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
 	depends on SMP
 	range 0 21
-	default 12 if !BASE_SMALL
-	default 0 if BASE_SMALL
+	default 12 if BASE_FULL
+	default 0
 	depends on PRINTK
 	help
 	  This option allows to increase the default ring buffer size
-- 
2.39.2

Re: [PATCH v3 1/2] printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled

[Masahiro Yamada]

On Mon, Feb 5, 2024 at 8:30 AM Yoann Congal <yoann.congal@smile.fr> wrote:
>
> LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL:
>   config LOG_CPU_MAX_BUF_SHIFT
>         default 12 if !BASE_SMALL
>         default 0 if BASE_SMALL
> But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always
> evaluated to true whatever is the value of BASE_SMALL.
>
> This patch fixes this by using BASE_FULL (type bool) which is equivalent
> to BASE_SMALL==0.
>
> Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to
> CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will
> not be a big impact due to this code in kernel/printk/printk.c:
>   /* by default this will only continue through for large > 64 CPUs */
>   if (cpu_extra <= __LOG_BUF_LEN / 2)
>           return;
> Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite
> rare.
>
> John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote:
> > For printk this will mean that BASE_SMALL systems were probably
> > previously allocating/using the dynamic ringbuffer and now they will
> > just continue to use the static ringbuffer. Which is fine and saves
> > memory (as it should).
>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
> Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
> Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/
> Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")
> ---
>  init/Kconfig | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)



Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>



-- 
Best Regards
Masahiro Yamada

Re: [PATCH v3 1/2] printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled

[John Ogness]

On 2024-02-05, Yoann Congal <yoann.congal@smile.fr> wrote:
> LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL:
>   config LOG_CPU_MAX_BUF_SHIFT
>   	default 12 if !BASE_SMALL
>   	default 0 if BASE_SMALL
> But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always
> evaluated to true whatever is the value of BASE_SMALL.
>
> This patch fixes this by using BASE_FULL (type bool) which is equivalent
> to BASE_SMALL==0.
>
> Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to
> CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will
> not be a big impact due to this code in kernel/printk/printk.c:
>   /* by default this will only continue through for large > 64 CPUs */
>   if (cpu_extra <= __LOG_BUF_LEN / 2)
>           return;
> Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite
> rare.
>
> John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote:
>> For printk this will mean that BASE_SMALL systems were probably
>> previously allocating/using the dynamic ringbuffer and now they will
>> just continue to use the static ringbuffer. Which is fine and saves
>> memory (as it should).
>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
> Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
> Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/
> Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")

Reviewed-by: John Ogness <john.ogness@linutronix.de>

Re: [PATCH v3 1/2] printk: Fix LOG_CPU_MAX_BUF_SHIFT when BASE_SMALL is enabled

[Petr Mladek]

On Mon 2024-02-05 00:29:44, Yoann Congal wrote:
> LOG_CPU_MAX_BUF_SHIFT default value depends on BASE_SMALL:
>   config LOG_CPU_MAX_BUF_SHIFT
>   	default 12 if !BASE_SMALL
>   	default 0 if BASE_SMALL
> But, BASE_SMALL is a config of type int and "!BASE_SMALL" is always
> evaluated to true whatever is the value of BASE_SMALL.
> 
> This patch fixes this by using BASE_FULL (type bool) which is equivalent
> to BASE_SMALL==0.
> 
> Note: This changes CONFIG_LOG_CPU_MAX_BUF_SHIFT=12 to
> CONFIG_LOG_CPU_MAX_BUF_SHIFT=0 for BASE_SMALL defconfigs, but that will
> not be a big impact due to this code in kernel/printk/printk.c:
>   /* by default this will only continue through for large > 64 CPUs */
>   if (cpu_extra <= __LOG_BUF_LEN / 2)
>           return;
> Systems using CONFIG_BASE_SMALL and having 64+ CPUs should be quite
> rare.
> 
> John Ogness <john.ogness@linutronix.de> (printk reviewer) wrote:
> > For printk this will mean that BASE_SMALL systems were probably
> > previously allocating/using the dynamic ringbuffer and now they will
> > just continue to use the static ringbuffer. Which is fine and saves
> > memory (as it should).

More precisely, it allocated the buffer dynamically when the sum
of per-CPU-extra space exceeded half of the default static ring
buffer. This happened for systems with more than 64 CPUs with
the default config values.

I believe that this patch won't have any effect in practice.
It is hard to imagine a system with >64 CPUs which would require
BASE_SMALL kernel. Well, never say never ;-)

> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Closes: https://lore.kernel.org/all/CAMuHMdWm6u1wX7efZQf=2XUAHascps76YQac6rdnQGhc8nop_Q@mail.gmail.com/
> Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
> Closes: https://lore.kernel.org/all/f6856be8-54b7-0fa0-1d17-39632bf29ada@oracle.com/
> Fixes: 4e244c10eab3 ("kconfig: remove unneeded symbol_empty variable")

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

[PATCH v3 2/2] printk: Remove redundant CONFIG_BASE_SMALL

[Yoann Congal]

CONFIG_BASE_SMALL is currently a type int but is only used as a boolean
equivalent to !CONFIG_BASE_FULL.

So, remove it entirely and move every usage to !CONFIG_BASE_FULL:
Since CONFIG_BASE_FULL is a type bool config,
CONFIG_BASE_SMALL == 0 becomes  IS_ENABLED(CONFIG_BASE_FULL) and
CONFIG_BASE_SMALL != 0 becomes !IS_ENABLED(CONFIG_BASE_FULL).

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
 arch/x86/include/asm/mpspec.h | 2 +-
 drivers/tty/vt/vc_screen.c    | 2 +-
 include/linux/threads.h       | 6 +++---
 include/linux/udp.h           | 2 +-
 include/linux/xarray.h        | 2 +-
 init/Kconfig                  | 5 -----
 kernel/futex/core.c           | 6 +++---
 kernel/user.c                 | 2 +-
 8 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index 4b0f98a8d338d..44307fb37fa25 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 == 0
+#ifdef CONFIG_BASE_FULL
 # 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..d0e4fcd1bd8b5 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_FULL) ? PAGE_SIZE : 256)
 
 /*
  * Our minor space:
diff --git a/include/linux/threads.h b/include/linux/threads.h
index c34173e6c5f18..f0f7a8aaba77d 100644
--- a/include/linux/threads.h
+++ b/include/linux/threads.h
@@ -25,14 +25,14 @@
 /*
  * 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_FULL) ? 0x8000 : 0x1000)
 
 /*
  * A maximum of 4 million PIDs should be enough for a while.
  * [NOTE: PID/TIDs are limited to 2^30 ~= 1 billion, see FUTEX_TID_MASK.]
  */
-#define PID_MAX_LIMIT (CONFIG_BASE_SMALL ? PAGE_SIZE * 8 : \
-	(sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT))
+#define PID_MAX_LIMIT (IS_ENABLED(CONFIG_BASE_FULL) ? \
+	(sizeof(long) > 4 ? 4 * 1024 * 1024 : PID_MAX_DEFAULT) : PAGE_SIZE * 8)
 
 /*
  * Define a minimum number of pids per cpu.  Heuristically based
diff --git a/include/linux/udp.h b/include/linux/udp.h
index d04188714dca1..ca8a172169019 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -24,7 +24,7 @@ static inline struct udphdr *udp_hdr(const struct sk_buff *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_FULL) ? 256 : 128)
 #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..7e00e71c2d266 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -1141,7 +1141,7 @@ static inline void xa_release(struct xarray *xa, unsigned long index)
  * doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
  */
 #ifndef XA_CHUNK_SHIFT
-#define XA_CHUNK_SHIFT		(CONFIG_BASE_SMALL ? 4 : 6)
+#define XA_CHUNK_SHIFT		(IS_ENABLED(CONFIG_BASE_FULL) ? 6 : 4)
 #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 73efb76f38734..3c1654fc770b5 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1940,11 +1940,6 @@ config RT_MUTEXES
 	bool
 	default y if PREEMPT_RT
 
-config BASE_SMALL
-	int
-	default 0 if BASE_FULL
-	default 1 if !BASE_FULL
-
 config MODULE_SIG_FORMAT
 	def_bool n
 	select SYSTEM_DATA_VERIFICATION
diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index 1e78ef24321e8..8488d3a23e2fd 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -1150,10 +1150,10 @@ static int __init futex_init(void)
 	unsigned int futex_shift;
 	unsigned long i;
 
-#if CONFIG_BASE_SMALL
-	futex_hashsize = 16;
-#else
+#ifdef CONFIG_BASE_FULL
 	futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus());
+#else
+	futex_hashsize = 16;
 #endif
 
 	futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues),
diff --git a/kernel/user.c b/kernel/user.c
index 03cedc366dc9e..8f39fd0236fa0 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_FULL) ? 7 : 3)
 #define UIDHASH_SZ	(1 << UIDHASH_BITS)
 #define UIDHASH_MASK		(UIDHASH_SZ - 1)
 #define __uidhashfn(uid)	(((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
-- 
2.39.2

Re: [PATCH v3 2/2] printk: Remove redundant CONFIG_BASE_SMALL

[Masahiro Yamada]

On Mon, Feb 5, 2024 at 8:30 AM Yoann Congal <yoann.congal@smile.fr> wrote:
>
> CONFIG_BASE_SMALL is currently a type int but is only used as a boolean
> equivalent to !CONFIG_BASE_FULL.
>
> So, remove it entirely and move every usage to !CONFIG_BASE_FULL:
> Since CONFIG_BASE_FULL is a type bool config,
> CONFIG_BASE_SMALL == 0 becomes  IS_ENABLED(CONFIG_BASE_FULL) and
> CONFIG_BASE_SMALL != 0 becomes !IS_ENABLED(CONFIG_BASE_FULL).
>
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>



Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>




-- 
Best Regards
Masahiro Yamada

Re: [PATCH v3 2/2] printk: Remove redundant CONFIG_BASE_SMALL

[Petr Mladek]

On Mon 2024-02-05 00:29:45, Yoann Congal wrote:
> CONFIG_BASE_SMALL is currently a type int but is only used as a boolean
> equivalent to !CONFIG_BASE_FULL.
> 
> So, remove it entirely and move every usage to !CONFIG_BASE_FULL:
> Since CONFIG_BASE_FULL is a type bool config,
> CONFIG_BASE_SMALL == 0 becomes  IS_ENABLED(CONFIG_BASE_FULL) and
> CONFIG_BASE_SMALL != 0 becomes !IS_ENABLED(CONFIG_BASE_FULL).
> 
> Signed-off-by: Yoann Congal <yoann.congal@smile.fr>

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

Re: [PATCH v3 0/2] printk: CONFIG_BASE_SMALL fix for LOG_CPU_MAX_BUF_SHIFT and removal

[Petr Mladek]

On Mon 2024-02-05 00:29:43, Yoann Congal wrote:
> This series focuses on CONFIG_BASE_SMALL.
> The first patch fixes LOG_CPU_MAX_BUF_SHIFT when CONFIG_BASE_SMALL is
> used.
> The second patch globally replace CONFIG_BASE_SMALL usages by the
> equivalent !CONFIG_BASE_FULL.

Nit: I would personally do it the other way around and get rid of
     CONFIG_BASE_SMALL.

     CONFIG_BASE_FULL is the default and is used by most users. It is
     the CONFIG_BASE_SMALL which needs special treating.

     That said, I do not want to block this patchset because
     of my preferences.

Best Regards,
Petr