mm, treewide: redefine MAX_ORDER sanely

MAX_ORDER currently defined as number of orders page allocator supports:
user can ask buddy allocator for page order between 0 and MAX_ORDER-1.

This definition is counter-intuitive and lead to number of bugs all over
the kernel.

Change the definition of MAX_ORDER to be inclusive: the range of orders
user can ask from buddy allocator is 0..MAX_ORDER now.

[kirill@shutemov.name: fix min() warning]
  Link: https://lkml.kernel.org/r/20230315153800.32wib3n5rickolvh@box
[akpm@linux-foundation.org: fix another min_t warning]
[kirill@shutemov.name: fixups per Zi Yan]
  Link: https://lkml.kernel.org/r/20230316232144.b7ic4cif4kjiabws@box.shutemov.name
[akpm@linux-foundation.org: fix underlining in docs]
  Link: https://lore.kernel.org/oe-kbuild-all/202303191025.VRCTk6mP-lkp@intel.com/
Link: https://lkml.kernel.org/r/20230315113133.11326-11-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>	[powerpc]
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

7 files changed, 9 insertions, 12 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index e24a9820e12f..929e646e84b9 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1355,9 +1355,9 @@ config ARM_MODULE_PLTS
 
 config ARCH_FORCE_MAX_ORDER
 	int "Maximum zone order"
-	default "12" if SOC_AM33XX
-	default "9" if SA1111
-	default "11"
+	default "11" if SOC_AM33XX
+	default "8" if SA1111
+	default "10"
 	help
 	  The kernel memory allocator divides physically contiguous memory
 	  blocks into "zones", where each zone is a power of two number of
@@ -1366,9 +1366,6 @@ config ARCH_FORCE_MAX_ORDER
 	  blocks of physically contiguous memory, then you may need to
 	  increase this value.
 
-	  This config option is actually maximum order plus one. For example,
-	  a value of 11 means that the largest free memory block is 2^10 pages.
-
 config ALIGNMENT_TRAP
 	def_bool CPU_CP15_MMU
 	select HAVE_PROC_CPU if PROC_FS
diff --git a/arch/arm/configs/imx_v6_v7_defconfig b/arch/arm/configs/imx_v6_v7_defconfig
index 6dc6fed12af8..345a67e67dbd 100644
--- a/arch/arm/configs/imx_v6_v7_defconfig
+++ b/arch/arm/configs/imx_v6_v7_defconfig
@@ -31,7 +31,7 @@ CONFIG_SOC_VF610=y
 CONFIG_SMP=y
 CONFIG_ARM_PSCI=y
 CONFIG_HIGHMEM=y
-CONFIG_ARCH_FORCE_MAX_ORDER=14
+CONFIG_ARCH_FORCE_MAX_ORDER=13
 CONFIG_CMDLINE="noinitrd console=ttymxc0,115200"
 CONFIG_KEXEC=y
 CONFIG_CPU_FREQ=y
diff --git a/arch/arm/configs/milbeaut_m10v_defconfig b/arch/arm/configs/milbeaut_m10v_defconfig
index bd29e5012cb0..385ad0f391a8 100644
--- a/arch/arm/configs/milbeaut_m10v_defconfig
+++ b/arch/arm/configs/milbeaut_m10v_defconfig
@@ -26,7 +26,7 @@ CONFIG_THUMB2_KERNEL=y
 # CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11 is not set
 # CONFIG_ARM_PATCH_IDIV is not set
 CONFIG_HIGHMEM=y
-CONFIG_ARCH_FORCE_MAX_ORDER=12
+CONFIG_ARCH_FORCE_MAX_ORDER=11
 CONFIG_SECCOMP=y
 CONFIG_KEXEC=y
 CONFIG_EFI=y
diff --git a/arch/arm/configs/oxnas_v6_defconfig b/arch/arm/configs/oxnas_v6_defconfig
index 70a67b3fc91b..90779812c6dd 100644
--- a/arch/arm/configs/oxnas_v6_defconfig
+++ b/arch/arm/configs/oxnas_v6_defconfig
@@ -12,7 +12,7 @@ CONFIG_ARCH_OXNAS=y
 CONFIG_MACH_OX820=y
 CONFIG_SMP=y
 CONFIG_NR_CPUS=16
-CONFIG_ARCH_FORCE_MAX_ORDER=12
+CONFIG_ARCH_FORCE_MAX_ORDER=11
 CONFIG_SECCOMP=y
 CONFIG_ARM_APPENDED_DTB=y
 CONFIG_ARM_ATAG_DTB_COMPAT=y
diff --git a/arch/arm/configs/pxa_defconfig b/arch/arm/configs/pxa_defconfig
index e656d3af2266..b46e39369dbb 100644
--- a/arch/arm/configs/pxa_defconfig
+++ b/arch/arm/configs/pxa_defconfig
@@ -20,7 +20,7 @@ CONFIG_PXA_SHARPSL=y
 CONFIG_MACH_AKITA=y
 CONFIG_MACH_BORZOI=y
 CONFIG_AEABI=y
-CONFIG_ARCH_FORCE_MAX_ORDER=9
+CONFIG_ARCH_FORCE_MAX_ORDER=8
 CONFIG_CMDLINE="root=/dev/ram0 ro"
 CONFIG_KEXEC=y
 CONFIG_CPU_FREQ=y
diff --git a/arch/arm/configs/sama7_defconfig b/arch/arm/configs/sama7_defconfig
index 0d964c613d71..954112041403 100644
--- a/arch/arm/configs/sama7_defconfig
+++ b/arch/arm/configs/sama7_defconfig
@@ -19,7 +19,7 @@ CONFIG_ATMEL_CLOCKSOURCE_TCB=y
 # CONFIG_CACHE_L2X0 is not set
 # CONFIG_ARM_PATCH_IDIV is not set
 # CONFIG_CPU_SW_DOMAIN_PAN is not set
-CONFIG_ARCH_FORCE_MAX_ORDER=15
+CONFIG_ARCH_FORCE_MAX_ORDER=14
 CONFIG_UACCESS_WITH_MEMCPY=y
 # CONFIG_ATAGS is not set
 CONFIG_CMDLINE="console=ttyS0,115200 earlyprintk ignore_loglevel"
diff --git a/arch/arm/configs/sp7021_defconfig b/arch/arm/configs/sp7021_defconfig
index 5bca2eb59b86..c6448ac860b6 100644
--- a/arch/arm/configs/sp7021_defconfig
+++ b/arch/arm/configs/sp7021_defconfig
@@ -17,7 +17,7 @@ CONFIG_ARCH_SUNPLUS=y
 # CONFIG_VDSO is not set
 CONFIG_SMP=y
 CONFIG_THUMB2_KERNEL=y
-CONFIG_ARCH_FORCE_MAX_ORDER=12
+CONFIG_ARCH_FORCE_MAX_ORDER=11
 CONFIG_VFP=y
 CONFIG_NEON=y
 CONFIG_MODULES=y