mm: remove CONFIG_DISCONTIGMEM

There are no architectures that support DISCONTIGMEM left.

Remove the configuration option and the dead code it was guarding in the
generic memory management code.

Link: https://lkml.kernel.org/r/20210608091316.3622-6-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 35 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index 02d44e3420f5..218b96ccc84a 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -19,7 +19,7 @@ choice
 
 config FLATMEM_MANUAL
 	bool "Flat Memory"
-	depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
+	depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
 	help
 	  This option is best suited for non-NUMA systems with
 	  flat address space. The FLATMEM is the most efficient
@@ -32,21 +32,6 @@ config FLATMEM_MANUAL
 
 	  If unsure, choose this option (Flat Memory) over any other.
 
-config DISCONTIGMEM_MANUAL
-	bool "Discontiguous Memory"
-	depends on ARCH_DISCONTIGMEM_ENABLE
-	help
-	  This option provides enhanced support for discontiguous
-	  memory systems, over FLATMEM.  These systems have holes
-	  in their physical address spaces, and this option provides
-	  more efficient handling of these holes.
-
-	  Although "Discontiguous Memory" is still used by several
-	  architectures, it is considered deprecated in favor of
-	  "Sparse Memory".
-
-	  If unsure, choose "Sparse Memory" over this option.
-
 config SPARSEMEM_MANUAL
 	bool "Sparse Memory"
 	depends on ARCH_SPARSEMEM_ENABLE
@@ -62,17 +47,13 @@ config SPARSEMEM_MANUAL
 
 endchoice
 
-config DISCONTIGMEM
-	def_bool y
-	depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
-
 config SPARSEMEM
 	def_bool y
 	depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
 
 config FLATMEM
 	def_bool y
-	depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
+	depends on !SPARSEMEM || FLATMEM_MANUAL
 
 config FLAT_NODE_MEM_MAP
 	def_bool y
@@ -85,7 +66,7 @@ config FLAT_NODE_MEM_MAP
 #
 config NEED_MULTIPLE_NODES
 	def_bool y
-	depends on DISCONTIGMEM || NUMA
+	depends on NUMA
 
 #
 # SPARSEMEM_EXTREME (which is the default) does some bootmem
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 58f7a321598f..8926f3fd3bcf 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -349,20 +349,7 @@ compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
 
 int min_free_kbytes = 1024;
 int user_min_free_kbytes = -1;
-#ifdef CONFIG_DISCONTIGMEM
-/*
- * DiscontigMem defines memory ranges as separate pg_data_t even if the ranges
- * are not on separate NUMA nodes. Functionally this works but with
- * watermark_boost_factor, it can reclaim prematurely as the ranges can be
- * quite small. By default, do not boost watermarks on discontigmem as in
- * many cases very high-order allocations like THP are likely to be
- * unsupported and the premature reclaim offsets the advantage of long-term
- * fragmentation avoidance.
- */
-int watermark_boost_factor __read_mostly;
-#else
 int watermark_boost_factor __read_mostly = 15000;
-#endif
 int watermark_scale_factor = 10;
 
 static unsigned long nr_kernel_pages __initdata;