memblock: align freed memory map on pageblock boundaries with SPARSEMEM

stable inclusion
from stable-v5.10.87
commit 74551f13c62fed411ea47457a31bbfc160e5d3fb
bugzilla: 186049 https://gitee.com/openeuler/kernel/issues/I4QVYL

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=74551f13c62fed411ea47457a31bbfc160e5d3fb

--------------------------------

[ Upstream commit f921f53e ]

When CONFIG_SPARSEMEM=y the ranges of the memory map that are freed are not
aligned to the pageblock boundaries which breaks assumptions about
homogeneity of the memory map throughout core mm code.

Make sure that the freed memory map is always aligned on pageblock
boundaries regardless of the memory model selection.
Signed-off-by: NMike Rapoport <rppt@linux.ibm.com>
Tested-by: NTony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/lkml/20210630071211.21011-1-rppt@kernel.org/
[backport upstream modification in mm/memblock.c to arch/arm/mm/init.c]
Signed-off-by: NMark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm/mm/init.c

@@ -313,14 +313,14 @@ static void __init free_unused_memmap(void)
 		 */
 		start = min(start,
 				 ALIGN(prev_end, PAGES_PER_SECTION));
-#else
+#endif
 		/*
 		 * Align down here since many operations in VM subsystem
 		 * presume that there are no holes in the memory map inside
 		 * a pageblock
 		 */
 		start = round_down(start, pageblock_nr_pages);
-#endif
+
 		/*
 		 * If we had a previous bank, and there is a space
 		 * between the current bank and the previous, free it.
@@ -337,9 +337,11 @@ static void __init free_unused_memmap(void)
 	}
 
 #ifdef CONFIG_SPARSEMEM
-	if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION))
+	if (!IS_ALIGNED(prev_end, PAGES_PER_SECTION)) {
+		prev_end = ALIGN(end, pageblock_nr_pages);
 		free_memmap(prev_end,
 			    ALIGN(prev_end, PAGES_PER_SECTION));
+	}
 #endif
 }