linux-stable/arch/ia64/mm/init.c
Dan Williams 033fbae988 mm: ZONE_DEVICE for "device memory"
While pmem is usable as a block device or via DAX mappings to userspace
there are several usage scenarios that can not target pmem due to its
lack of struct page coverage. In preparation for "hot plugging" pmem
into the vmemmap add ZONE_DEVICE as a new zone to tag these pages
separately from the ones that are subject to standard page allocations.
Importantly "device memory" can be removed at will by userspace
unbinding the driver of the device.

Having a separate zone prevents allocation and otherwise marks these
pages that are distinct from typical uniform memory.  Device memory has
different lifetime and performance characteristics than RAM.  However,
since we have run out of ZONES_SHIFT bits this functionality currently
depends on sacrificing ZONE_DMA.

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Jerome Glisse <j.glisse@gmail.com>
[hch: various simplifications in the arch interface]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
2015-08-27 19:40:58 -04:00

734 lines
19 KiB
C

/*
* Initialize MMU support.
*
* Copyright (C) 1998-2003 Hewlett-Packard Co
* David Mosberger-Tang <davidm@hpl.hp.com>
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/efi.h>
#include <linux/elf.h>
#include <linux/memblock.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/module.h>
#include <linux/personality.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/proc_fs.h>
#include <linux/bitops.h>
#include <linux/kexec.h>
#include <asm/dma.h>
#include <asm/io.h>
#include <asm/machvec.h>
#include <asm/numa.h>
#include <asm/patch.h>
#include <asm/pgalloc.h>
#include <asm/sal.h>
#include <asm/sections.h>
#include <asm/tlb.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/mca.h>
extern void ia64_tlb_init (void);
unsigned long MAX_DMA_ADDRESS = PAGE_OFFSET + 0x100000000UL;
#ifdef CONFIG_VIRTUAL_MEM_MAP
unsigned long VMALLOC_END = VMALLOC_END_INIT;
EXPORT_SYMBOL(VMALLOC_END);
struct page *vmem_map;
EXPORT_SYMBOL(vmem_map);
#endif
struct page *zero_page_memmap_ptr; /* map entry for zero page */
EXPORT_SYMBOL(zero_page_memmap_ptr);
void
__ia64_sync_icache_dcache (pte_t pte)
{
unsigned long addr;
struct page *page;
page = pte_page(pte);
addr = (unsigned long) page_address(page);
if (test_bit(PG_arch_1, &page->flags))
return; /* i-cache is already coherent with d-cache */
flush_icache_range(addr, addr + (PAGE_SIZE << compound_order(page)));
set_bit(PG_arch_1, &page->flags); /* mark page as clean */
}
/*
* Since DMA is i-cache coherent, any (complete) pages that were written via
* DMA can be marked as "clean" so that lazy_mmu_prot_update() doesn't have to
* flush them when they get mapped into an executable vm-area.
*/
void
dma_mark_clean(void *addr, size_t size)
{
unsigned long pg_addr, end;
pg_addr = PAGE_ALIGN((unsigned long) addr);
end = (unsigned long) addr + size;
while (pg_addr + PAGE_SIZE <= end) {
struct page *page = virt_to_page(pg_addr);
set_bit(PG_arch_1, &page->flags);
pg_addr += PAGE_SIZE;
}
}
inline void
ia64_set_rbs_bot (void)
{
unsigned long stack_size = rlimit_max(RLIMIT_STACK) & -16;
if (stack_size > MAX_USER_STACK_SIZE)
stack_size = MAX_USER_STACK_SIZE;
current->thread.rbs_bot = PAGE_ALIGN(current->mm->start_stack - stack_size);
}
/*
* This performs some platform-dependent address space initialization.
* On IA-64, we want to setup the VM area for the register backing
* store (which grows upwards) and install the gateway page which is
* used for signal trampolines, etc.
*/
void
ia64_init_addr_space (void)
{
struct vm_area_struct *vma;
ia64_set_rbs_bot();
/*
* If we're out of memory and kmem_cache_alloc() returns NULL, we simply ignore
* the problem. When the process attempts to write to the register backing store
* for the first time, it will get a SEGFAULT in this case.
*/
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (vma) {
INIT_LIST_HEAD(&vma->anon_vma_chain);
vma->vm_mm = current->mm;
vma->vm_start = current->thread.rbs_bot & PAGE_MASK;
vma->vm_end = vma->vm_start + PAGE_SIZE;
vma->vm_flags = VM_DATA_DEFAULT_FLAGS|VM_GROWSUP|VM_ACCOUNT;
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
down_write(&current->mm->mmap_sem);
if (insert_vm_struct(current->mm, vma)) {
up_write(&current->mm->mmap_sem);
kmem_cache_free(vm_area_cachep, vma);
return;
}
up_write(&current->mm->mmap_sem);
}
/* map NaT-page at address zero to speed up speculative dereferencing of NULL: */
if (!(current->personality & MMAP_PAGE_ZERO)) {
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (vma) {
INIT_LIST_HEAD(&vma->anon_vma_chain);
vma->vm_mm = current->mm;
vma->vm_end = PAGE_SIZE;
vma->vm_page_prot = __pgprot(pgprot_val(PAGE_READONLY) | _PAGE_MA_NAT);
vma->vm_flags = VM_READ | VM_MAYREAD | VM_IO |
VM_DONTEXPAND | VM_DONTDUMP;
down_write(&current->mm->mmap_sem);
if (insert_vm_struct(current->mm, vma)) {
up_write(&current->mm->mmap_sem);
kmem_cache_free(vm_area_cachep, vma);
return;
}
up_write(&current->mm->mmap_sem);
}
}
}
void
free_initmem (void)
{
free_reserved_area(ia64_imva(__init_begin), ia64_imva(__init_end),
-1, "unused kernel");
}
void __init
free_initrd_mem (unsigned long start, unsigned long end)
{
/*
* EFI uses 4KB pages while the kernel can use 4KB or bigger.
* Thus EFI and the kernel may have different page sizes. It is
* therefore possible to have the initrd share the same page as
* the end of the kernel (given current setup).
*
* To avoid freeing/using the wrong page (kernel sized) we:
* - align up the beginning of initrd
* - align down the end of initrd
*
* | |
* |=============| a000
* | |
* | |
* | | 9000
* |/////////////|
* |/////////////|
* |=============| 8000
* |///INITRD////|
* |/////////////|
* |/////////////| 7000
* | |
* |KKKKKKKKKKKKK|
* |=============| 6000
* |KKKKKKKKKKKKK|
* |KKKKKKKKKKKKK|
* K=kernel using 8KB pages
*
* In this example, we must free page 8000 ONLY. So we must align up
* initrd_start and keep initrd_end as is.
*/
start = PAGE_ALIGN(start);
end = end & PAGE_MASK;
if (start < end)
printk(KERN_INFO "Freeing initrd memory: %ldkB freed\n", (end - start) >> 10);
for (; start < end; start += PAGE_SIZE) {
if (!virt_addr_valid(start))
continue;
free_reserved_page(virt_to_page(start));
}
}
/*
* This installs a clean page in the kernel's page table.
*/
static struct page * __init
put_kernel_page (struct page *page, unsigned long address, pgprot_t pgprot)
{
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
pgd = pgd_offset_k(address); /* note: this is NOT pgd_offset()! */
{
pud = pud_alloc(&init_mm, pgd, address);
if (!pud)
goto out;
pmd = pmd_alloc(&init_mm, pud, address);
if (!pmd)
goto out;
pte = pte_alloc_kernel(pmd, address);
if (!pte)
goto out;
if (!pte_none(*pte))
goto out;
set_pte(pte, mk_pte(page, pgprot));
}
out:
/* no need for flush_tlb */
return page;
}
static void __init
setup_gate (void)
{
struct page *page;
/*
* Map the gate page twice: once read-only to export the ELF
* headers etc. and once execute-only page to enable
* privilege-promotion via "epc":
*/
page = virt_to_page(ia64_imva(__start_gate_section));
put_kernel_page(page, GATE_ADDR, PAGE_READONLY);
#ifdef HAVE_BUGGY_SEGREL
page = virt_to_page(ia64_imva(__start_gate_section + PAGE_SIZE));
put_kernel_page(page, GATE_ADDR + PAGE_SIZE, PAGE_GATE);
#else
put_kernel_page(page, GATE_ADDR + PERCPU_PAGE_SIZE, PAGE_GATE);
/* Fill in the holes (if any) with read-only zero pages: */
{
unsigned long addr;
for (addr = GATE_ADDR + PAGE_SIZE;
addr < GATE_ADDR + PERCPU_PAGE_SIZE;
addr += PAGE_SIZE)
{
put_kernel_page(ZERO_PAGE(0), addr,
PAGE_READONLY);
put_kernel_page(ZERO_PAGE(0), addr + PERCPU_PAGE_SIZE,
PAGE_READONLY);
}
}
#endif
ia64_patch_gate();
}
static struct vm_area_struct gate_vma;
static int __init gate_vma_init(void)
{
gate_vma.vm_mm = NULL;
gate_vma.vm_start = FIXADDR_USER_START;
gate_vma.vm_end = FIXADDR_USER_END;
gate_vma.vm_flags = VM_READ | VM_MAYREAD | VM_EXEC | VM_MAYEXEC;
gate_vma.vm_page_prot = __P101;
return 0;
}
__initcall(gate_vma_init);
struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
{
return &gate_vma;
}
int in_gate_area_no_mm(unsigned long addr)
{
if ((addr >= FIXADDR_USER_START) && (addr < FIXADDR_USER_END))
return 1;
return 0;
}
int in_gate_area(struct mm_struct *mm, unsigned long addr)
{
return in_gate_area_no_mm(addr);
}
void ia64_mmu_init(void *my_cpu_data)
{
unsigned long pta, impl_va_bits;
extern void tlb_init(void);
#ifdef CONFIG_DISABLE_VHPT
# define VHPT_ENABLE_BIT 0
#else
# define VHPT_ENABLE_BIT 1
#endif
/*
* Check if the virtually mapped linear page table (VMLPT) overlaps with a mapped
* address space. The IA-64 architecture guarantees that at least 50 bits of
* virtual address space are implemented but if we pick a large enough page size
* (e.g., 64KB), the mapped address space is big enough that it will overlap with
* VMLPT. I assume that once we run on machines big enough to warrant 64KB pages,
* IMPL_VA_MSB will be significantly bigger, so this is unlikely to become a
* problem in practice. Alternatively, we could truncate the top of the mapped
* address space to not permit mappings that would overlap with the VMLPT.
* --davidm 00/12/06
*/
# define pte_bits 3
# define mapped_space_bits (3*(PAGE_SHIFT - pte_bits) + PAGE_SHIFT)
/*
* The virtual page table has to cover the entire implemented address space within
* a region even though not all of this space may be mappable. The reason for
* this is that the Access bit and Dirty bit fault handlers perform
* non-speculative accesses to the virtual page table, so the address range of the
* virtual page table itself needs to be covered by virtual page table.
*/
# define vmlpt_bits (impl_va_bits - PAGE_SHIFT + pte_bits)
# define POW2(n) (1ULL << (n))
impl_va_bits = ffz(~(local_cpu_data->unimpl_va_mask | (7UL << 61)));
if (impl_va_bits < 51 || impl_va_bits > 61)
panic("CPU has bogus IMPL_VA_MSB value of %lu!\n", impl_va_bits - 1);
/*
* mapped_space_bits - PAGE_SHIFT is the total number of ptes we need,
* which must fit into "vmlpt_bits - pte_bits" slots. Second half of
* the test makes sure that our mapped space doesn't overlap the
* unimplemented hole in the middle of the region.
*/
if ((mapped_space_bits - PAGE_SHIFT > vmlpt_bits - pte_bits) ||
(mapped_space_bits > impl_va_bits - 1))
panic("Cannot build a big enough virtual-linear page table"
" to cover mapped address space.\n"
" Try using a smaller page size.\n");
/* place the VMLPT at the end of each page-table mapped region: */
pta = POW2(61) - POW2(vmlpt_bits);
/*
* Set the (virtually mapped linear) page table address. Bit
* 8 selects between the short and long format, bits 2-7 the
* size of the table, and bit 0 whether the VHPT walker is
* enabled.
*/
ia64_set_pta(pta | (0 << 8) | (vmlpt_bits << 2) | VHPT_ENABLE_BIT);
ia64_tlb_init();
#ifdef CONFIG_HUGETLB_PAGE
ia64_set_rr(HPAGE_REGION_BASE, HPAGE_SHIFT << 2);
ia64_srlz_d();
#endif
}
#ifdef CONFIG_VIRTUAL_MEM_MAP
int vmemmap_find_next_valid_pfn(int node, int i)
{
unsigned long end_address, hole_next_pfn;
unsigned long stop_address;
pg_data_t *pgdat = NODE_DATA(node);
end_address = (unsigned long) &vmem_map[pgdat->node_start_pfn + i];
end_address = PAGE_ALIGN(end_address);
stop_address = (unsigned long) &vmem_map[pgdat_end_pfn(pgdat)];
do {
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
pgd = pgd_offset_k(end_address);
if (pgd_none(*pgd)) {
end_address += PGDIR_SIZE;
continue;
}
pud = pud_offset(pgd, end_address);
if (pud_none(*pud)) {
end_address += PUD_SIZE;
continue;
}
pmd = pmd_offset(pud, end_address);
if (pmd_none(*pmd)) {
end_address += PMD_SIZE;
continue;
}
pte = pte_offset_kernel(pmd, end_address);
retry_pte:
if (pte_none(*pte)) {
end_address += PAGE_SIZE;
pte++;
if ((end_address < stop_address) &&
(end_address != ALIGN(end_address, 1UL << PMD_SHIFT)))
goto retry_pte;
continue;
}
/* Found next valid vmem_map page */
break;
} while (end_address < stop_address);
end_address = min(end_address, stop_address);
end_address = end_address - (unsigned long) vmem_map + sizeof(struct page) - 1;
hole_next_pfn = end_address / sizeof(struct page);
return hole_next_pfn - pgdat->node_start_pfn;
}
int __init create_mem_map_page_table(u64 start, u64 end, void *arg)
{
unsigned long address, start_page, end_page;
struct page *map_start, *map_end;
int node;
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
map_start = vmem_map + (__pa(start) >> PAGE_SHIFT);
map_end = vmem_map + (__pa(end) >> PAGE_SHIFT);
start_page = (unsigned long) map_start & PAGE_MASK;
end_page = PAGE_ALIGN((unsigned long) map_end);
node = paddr_to_nid(__pa(start));
for (address = start_page; address < end_page; address += PAGE_SIZE) {
pgd = pgd_offset_k(address);
if (pgd_none(*pgd))
pgd_populate(&init_mm, pgd, alloc_bootmem_pages_node(NODE_DATA(node), PAGE_SIZE));
pud = pud_offset(pgd, address);
if (pud_none(*pud))
pud_populate(&init_mm, pud, alloc_bootmem_pages_node(NODE_DATA(node), PAGE_SIZE));
pmd = pmd_offset(pud, address);
if (pmd_none(*pmd))
pmd_populate_kernel(&init_mm, pmd, alloc_bootmem_pages_node(NODE_DATA(node), PAGE_SIZE));
pte = pte_offset_kernel(pmd, address);
if (pte_none(*pte))
set_pte(pte, pfn_pte(__pa(alloc_bootmem_pages_node(NODE_DATA(node), PAGE_SIZE)) >> PAGE_SHIFT,
PAGE_KERNEL));
}
return 0;
}
struct memmap_init_callback_data {
struct page *start;
struct page *end;
int nid;
unsigned long zone;
};
static int __meminit
virtual_memmap_init(u64 start, u64 end, void *arg)
{
struct memmap_init_callback_data *args;
struct page *map_start, *map_end;
args = (struct memmap_init_callback_data *) arg;
map_start = vmem_map + (__pa(start) >> PAGE_SHIFT);
map_end = vmem_map + (__pa(end) >> PAGE_SHIFT);
if (map_start < args->start)
map_start = args->start;
if (map_end > args->end)
map_end = args->end;
/*
* We have to initialize "out of bounds" struct page elements that fit completely
* on the same pages that were allocated for the "in bounds" elements because they
* may be referenced later (and found to be "reserved").
*/
map_start -= ((unsigned long) map_start & (PAGE_SIZE - 1)) / sizeof(struct page);
map_end += ((PAGE_ALIGN((unsigned long) map_end) - (unsigned long) map_end)
/ sizeof(struct page));
if (map_start < map_end)
memmap_init_zone((unsigned long)(map_end - map_start),
args->nid, args->zone, page_to_pfn(map_start),
MEMMAP_EARLY);
return 0;
}
void __meminit
memmap_init (unsigned long size, int nid, unsigned long zone,
unsigned long start_pfn)
{
if (!vmem_map)
memmap_init_zone(size, nid, zone, start_pfn, MEMMAP_EARLY);
else {
struct page *start;
struct memmap_init_callback_data args;
start = pfn_to_page(start_pfn);
args.start = start;
args.end = start + size;
args.nid = nid;
args.zone = zone;
efi_memmap_walk(virtual_memmap_init, &args);
}
}
int
ia64_pfn_valid (unsigned long pfn)
{
char byte;
struct page *pg = pfn_to_page(pfn);
return (__get_user(byte, (char __user *) pg) == 0)
&& ((((u64)pg & PAGE_MASK) == (((u64)(pg + 1) - 1) & PAGE_MASK))
|| (__get_user(byte, (char __user *) (pg + 1) - 1) == 0));
}
EXPORT_SYMBOL(ia64_pfn_valid);
int __init find_largest_hole(u64 start, u64 end, void *arg)
{
u64 *max_gap = arg;
static u64 last_end = PAGE_OFFSET;
/* NOTE: this algorithm assumes efi memmap table is ordered */
if (*max_gap < (start - last_end))
*max_gap = start - last_end;
last_end = end;
return 0;
}
#endif /* CONFIG_VIRTUAL_MEM_MAP */
int __init register_active_ranges(u64 start, u64 len, int nid)
{
u64 end = start + len;
#ifdef CONFIG_KEXEC
if (start > crashk_res.start && start < crashk_res.end)
start = crashk_res.end;
if (end > crashk_res.start && end < crashk_res.end)
end = crashk_res.start;
#endif
if (start < end)
memblock_add_node(__pa(start), end - start, nid);
return 0;
}
int
find_max_min_low_pfn (u64 start, u64 end, void *arg)
{
unsigned long pfn_start, pfn_end;
#ifdef CONFIG_FLATMEM
pfn_start = (PAGE_ALIGN(__pa(start))) >> PAGE_SHIFT;
pfn_end = (PAGE_ALIGN(__pa(end - 1))) >> PAGE_SHIFT;
#else
pfn_start = GRANULEROUNDDOWN(__pa(start)) >> PAGE_SHIFT;
pfn_end = GRANULEROUNDUP(__pa(end - 1)) >> PAGE_SHIFT;
#endif
min_low_pfn = min(min_low_pfn, pfn_start);
max_low_pfn = max(max_low_pfn, pfn_end);
return 0;
}
/*
* Boot command-line option "nolwsys" can be used to disable the use of any light-weight
* system call handler. When this option is in effect, all fsyscalls will end up bubbling
* down into the kernel and calling the normal (heavy-weight) syscall handler. This is
* useful for performance testing, but conceivably could also come in handy for debugging
* purposes.
*/
static int nolwsys __initdata;
static int __init
nolwsys_setup (char *s)
{
nolwsys = 1;
return 1;
}
__setup("nolwsys", nolwsys_setup);
void __init
mem_init (void)
{
int i;
BUG_ON(PTRS_PER_PGD * sizeof(pgd_t) != PAGE_SIZE);
BUG_ON(PTRS_PER_PMD * sizeof(pmd_t) != PAGE_SIZE);
BUG_ON(PTRS_PER_PTE * sizeof(pte_t) != PAGE_SIZE);
#ifdef CONFIG_PCI
/*
* This needs to be called _after_ the command line has been parsed but _before_
* any drivers that may need the PCI DMA interface are initialized or bootmem has
* been freed.
*/
platform_dma_init();
#endif
#ifdef CONFIG_FLATMEM
BUG_ON(!mem_map);
#endif
set_max_mapnr(max_low_pfn);
high_memory = __va(max_low_pfn * PAGE_SIZE);
free_all_bootmem();
mem_init_print_info(NULL);
/*
* For fsyscall entrpoints with no light-weight handler, use the ordinary
* (heavy-weight) handler, but mark it by setting bit 0, so the fsyscall entry
* code can tell them apart.
*/
for (i = 0; i < NR_syscalls; ++i) {
extern unsigned long fsyscall_table[NR_syscalls];
extern unsigned long sys_call_table[NR_syscalls];
if (!fsyscall_table[i] || nolwsys)
fsyscall_table[i] = sys_call_table[i] | 1;
}
setup_gate();
}
#ifdef CONFIG_MEMORY_HOTPLUG
int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
{
pg_data_t *pgdat;
struct zone *zone;
unsigned long start_pfn = start >> PAGE_SHIFT;
unsigned long nr_pages = size >> PAGE_SHIFT;
int ret;
pgdat = NODE_DATA(nid);
zone = pgdat->node_zones +
zone_for_memory(nid, start, size, ZONE_NORMAL, for_device);
ret = __add_pages(nid, zone, start_pfn, nr_pages);
if (ret)
printk("%s: Problem encountered in __add_pages() as ret=%d\n",
__func__, ret);
return ret;
}
#ifdef CONFIG_MEMORY_HOTREMOVE
int arch_remove_memory(u64 start, u64 size)
{
unsigned long start_pfn = start >> PAGE_SHIFT;
unsigned long nr_pages = size >> PAGE_SHIFT;
struct zone *zone;
int ret;
zone = page_zone(pfn_to_page(start_pfn));
ret = __remove_pages(zone, start_pfn, nr_pages);
if (ret)
pr_warn("%s: Problem encountered in __remove_pages() as"
" ret=%d\n", __func__, ret);
return ret;
}
#endif
#endif
/**
* show_mem - give short summary of memory stats
*
* Shows a simple page count of reserved and used pages in the system.
* For discontig machines, it does this on a per-pgdat basis.
*/
void show_mem(unsigned int filter)
{
int total_reserved = 0;
unsigned long total_present = 0;
pg_data_t *pgdat;
printk(KERN_INFO "Mem-info:\n");
show_free_areas(filter);
printk(KERN_INFO "Node memory in pages:\n");
for_each_online_pgdat(pgdat) {
unsigned long present;
unsigned long flags;
int reserved = 0;
int nid = pgdat->node_id;
int zoneid;
if (skip_free_areas_node(filter, nid))
continue;
pgdat_resize_lock(pgdat, &flags);
for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
struct zone *zone = &pgdat->node_zones[zoneid];
if (!populated_zone(zone))
continue;
reserved += zone->present_pages - zone->managed_pages;
}
present = pgdat->node_present_pages;
pgdat_resize_unlock(pgdat, &flags);
total_present += present;
total_reserved += reserved;
printk(KERN_INFO "Node %4d: RAM: %11ld, rsvd: %8d, ",
nid, present, reserved);
}
printk(KERN_INFO "%ld pages of RAM\n", total_present);
printk(KERN_INFO "%d reserved pages\n", total_reserved);
printk(KERN_INFO "Total of %ld pages in page table cache\n",
quicklist_total_size());
printk(KERN_INFO "%ld free buffer pages\n", nr_free_buffer_pages());
}