mm/sparsemem: Fix ARM64 boot crash when CONFIG_SPARSEMEM_EXTREME=y

Since commit:

  83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")

we allocate the mem_section array dynamically in sparse_memory_present_with_active_regions(),
but some architectures, like arm64, don't call the routine to initialize sparsemem.

Let's move the initialization into memory_present() it should cover all
architectures.

Reported-and-tested-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Fixes: 83e3c48729d9 ("mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y")
Link: http://lkml.kernel.org/r/20171107083337.89952-1-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/mm/sparse.c b/mm/sparse.c
index b00a97398795..d294148ba395 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -206,6 +206,16 @@ void __init memory_present(int nid, unsigned long start, unsigned long end)
 {
         unsigned long pfn;
 
+#ifdef CONFIG_SPARSEMEM_EXTREME
+        if (unlikely(!mem_section)) {
+                unsigned long size, align;
+
+                size = sizeof(struct mem_section) * NR_SECTION_ROOTS;
+                align = 1 << (INTERNODE_CACHE_SHIFT);
+                mem_section = memblock_virt_alloc(size, align);
+        }
+#endif
+
         start &= PAGE_SECTION_MASK;
         mminit_validate_memmodel_limits(&start, &end);
         for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {