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>
diff --git a/arch/sh/mm/Kconfig b/arch/sh/mm/Kconfig
index 411fdc0..4027109 100644
--- a/arch/sh/mm/Kconfig
+++ b/arch/sh/mm/Kconfig
@@ -20,13 +20,13 @@
config ARCH_FORCE_MAX_ORDER
int "Maximum zone order"
- range 9 64 if PAGE_SIZE_16KB
- default "9" if PAGE_SIZE_16KB
- range 7 64 if PAGE_SIZE_64KB
- default "7" if PAGE_SIZE_64KB
- range 11 64
- default "14" if !MMU
- default "11"
+ range 8 63 if PAGE_SIZE_16KB
+ default "8" if PAGE_SIZE_16KB
+ range 6 63 if PAGE_SIZE_64KB
+ default "6" if PAGE_SIZE_64KB
+ range 10 63
+ default "13" if !MMU
+ default "10"
help
The kernel memory allocator divides physically contiguous memory
blocks into "zones", where each zone is a power of two number of
@@ -35,9 +35,6 @@
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.
-
The page size is not necessarily 4KB. Keep this in mind when
choosing a value for this option.
