This is a note to let you know that I've just added the patch titled

mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mm-sparsemem-allocate-mem_section-at-runtime-for-config_sparsemem_extreme-y.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 83e3c48729d9ebb7af5a31a504f3fd6aff0348c4 Mon Sep 17 00:00:00 2001

From: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Date: Fri, 29 Sep 2017 17:08:16 +0300 Subject: mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y

From: Kirill A. Shutemov kirill.shutemov@linux.intel.com

commit 83e3c48729d9ebb7af5a31a504f3fd6aff0348c4 upstream.

Size of the mem_section[] array depends on the size of the physical address space.

In preparation for boot-time switching between paging modes on x86-64 we need to make the allocation of mem_section[] dynamic, because otherwise we waste a lot of RAM: with CONFIG_NODE_SHIFT=10, mem_section[] size is 32kB for 4-level paging and 2MB for 5-level paging mode.

The patch allocates the array on the first call to sparse_memory_present_with_active_regions().

Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Andy Lutomirski luto@amacapital.net Cc: Borislav Petkov bp@suse.de Cc: Cyrill Gorcunov gorcunov@openvz.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 Link: http://lkml.kernel.org/r/20170929140821.37654-2-kirill.shutemov@linux.intel.... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- include/linux/mmzone.h | 6 +++++- mm/page_alloc.c | 10 ++++++++++ mm/sparse.c | 17 +++++++++++------ 3 files changed, 26 insertions(+), 7 deletions(-)

--- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1152,13 +1152,17 @@ struct mem_section { #define SECTION_ROOT_MASK (SECTIONS_PER_ROOT - 1)

#ifdef CONFIG_SPARSEMEM_EXTREME -extern struct mem_section *mem_section[NR_SECTION_ROOTS]; +extern struct mem_section **mem_section; #else extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]; #endif

static inline struct mem_section *__nr_to_section(unsigned long nr) { +#ifdef CONFIG_SPARSEMEM_EXTREME + if (!mem_section) + return NULL; +#endif if (!mem_section[SECTION_NR_TO_ROOT(nr)]) return NULL; return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK]; --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5651,6 +5651,16 @@ void __init sparse_memory_present_with_a unsigned long start_pfn, end_pfn; int i, this_nid;

+#ifdef CONFIG_SPARSEMEM_EXTREME + if (!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 + for_each_mem_pfn_range(i, nid, &start_pfn, &end_pfn, &this_nid) memory_present(this_nid, start_pfn, end_pfn); } --- a/mm/sparse.c +++ b/mm/sparse.c @@ -23,8 +23,7 @@ * 1) mem_section - memory sections, mem_map's for valid memory */ #ifdef CONFIG_SPARSEMEM_EXTREME -struct mem_section *mem_section[NR_SECTION_ROOTS] - ____cacheline_internodealigned_in_smp; +struct mem_section **mem_section; #else struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT] ____cacheline_internodealigned_in_smp; @@ -101,7 +100,7 @@ static inline int sparse_index_init(unsi int __section_nr(struct mem_section* ms) { unsigned long root_nr; - struct mem_section* root; + struct mem_section *root = NULL;

for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) { root = __nr_to_section(root_nr * SECTIONS_PER_ROOT); @@ -112,7 +111,7 @@ int __section_nr(struct mem_section* ms) break; }

- VM_BUG_ON(root_nr == NR_SECTION_ROOTS); + VM_BUG_ON(!root);

return (root_nr * SECTIONS_PER_ROOT) + (ms - root); } @@ -330,11 +329,17 @@ again: static void __init check_usemap_section_nr(int nid, unsigned long *usemap) { unsigned long usemap_snr, pgdat_snr; - static unsigned long old_usemap_snr = NR_MEM_SECTIONS; - static unsigned long old_pgdat_snr = NR_MEM_SECTIONS; + static unsigned long old_usemap_snr; + static unsigned long old_pgdat_snr; struct pglist_data *pgdat = NODE_DATA(nid); int usemap_nid;

+ /* First call */ + if (!old_usemap_snr) { + old_usemap_snr = NR_MEM_SECTIONS; + old_pgdat_snr = NR_MEM_SECTIONS; + } + usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT); pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT); if (usemap_snr == pgdat_snr)

Patches currently in stable-queue which might be from kirill.shutemov@linux.intel.com are

queue-4.14/x86-xen-provide-pre-built-page-tables-only-for-config_xen_pv-y-and-config_xen_pvh-y.patch queue-4.14/x86-xen-drop-5-level-paging-support-code-from-the-xen_pv-code.patch queue-4.14/x86-kasan-use-the-same-shadow-offset-for-4-and-5-level-paging.patch queue-4.14/mm-sparsemem-allocate-mem_section-at-runtime-for-config_sparsemem_extreme-y.patch queue-4.14/x86-mm-relocate-page-fault-error-codes-to-traps.h.patch