[PATCH] hugepage: serialize hugepage allocation and instantiation

[mirror_ubuntu-bionic-kernel.git] / mm / hugetlb.c

/*
 * Generic hugetlb support.
 * (C) William Irwin, April 2004
 */
#include <linux/gfp.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/sysctl.h>
#include <linux/highmem.h>
#include <linux/nodemask.h>
#include <linux/pagemap.h>
#include <linux/mempolicy.h>
#include <linux/cpuset.h>
#include <linux/mutex.h>

#include <asm/page.h>
#include <asm/pgtable.h>

#include <linux/hugetlb.h>
#include "internal.h"

const unsigned long hugetlb_zero = 0, hugetlb_infinity = ~0UL;
static unsigned long nr_huge_pages, free_huge_pages;
unsigned long max_huge_pages;
static struct list_head hugepage_freelists[MAX_NUMNODES];
static unsigned int nr_huge_pages_node[MAX_NUMNODES];
static unsigned int free_huge_pages_node[MAX_NUMNODES];
/*
 * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages
 */
static DEFINE_SPINLOCK(hugetlb_lock);

static void clear_huge_page(struct page *page, unsigned long addr)
{
        int i;

        might_sleep();
        for (i = 0; i < (HPAGE_SIZE/PAGE_SIZE); i++) {
                cond_resched();
                clear_user_highpage(page + i, addr);
        }
}

static void copy_huge_page(struct page *dst, struct page *src,
                           unsigned long addr)
{
        int i;

        might_sleep();
        for (i = 0; i < HPAGE_SIZE/PAGE_SIZE; i++) {
                cond_resched();
                copy_user_highpage(dst + i, src + i, addr + i*PAGE_SIZE);
        }
}

static void enqueue_huge_page(struct page *page)
{
        int nid = page_to_nid(page);
        list_add(&page->lru, &hugepage_freelists[nid]);
        free_huge_pages++;
        free_huge_pages_node[nid]++;
}

static struct page *dequeue_huge_page(struct vm_area_struct *vma,
                                unsigned long address)
{
        int nid = numa_node_id();
        struct page *page = NULL;
        struct zonelist *zonelist = huge_zonelist(vma, address);
        struct zone **z;

        for (z = zonelist->zones; *z; z++) {
                nid = (*z)->zone_pgdat->node_id;
                if (cpuset_zone_allowed(*z, GFP_HIGHUSER) &&
                    !list_empty(&hugepage_freelists[nid]))
                        break;
        }

        if (*z) {
                page = list_entry(hugepage_freelists[nid].next,
                                  struct page, lru);
                list_del(&page->lru);
                free_huge_pages--;
                free_huge_pages_node[nid]--;
        }
        return page;
}

static int alloc_fresh_huge_page(void)
{
        static int nid = 0;
        struct page *page;
        page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
                                        HUGETLB_PAGE_ORDER);
        nid = (nid + 1) % num_online_nodes();
        if (page) {
                page[1].lru.next = (void *)free_huge_page;      /* dtor */
                spin_lock(&hugetlb_lock);
                nr_huge_pages++;
                nr_huge_pages_node[page_to_nid(page)]++;
                spin_unlock(&hugetlb_lock);
                put_page(page); /* free it into the hugepage allocator */
                return 1;
        }
        return 0;
}

void free_huge_page(struct page *page)
{
        BUG_ON(page_count(page));

        INIT_LIST_HEAD(&page->lru);

        spin_lock(&hugetlb_lock);
        enqueue_huge_page(page);
        spin_unlock(&hugetlb_lock);
}

struct page *alloc_huge_page(struct vm_area_struct *vma, unsigned long addr)
{
        struct page *page;

        spin_lock(&hugetlb_lock);
        page = dequeue_huge_page(vma, addr);
        if (!page) {
                spin_unlock(&hugetlb_lock);
                return NULL;
        }
        spin_unlock(&hugetlb_lock);
        set_page_refcounted(page);
        return page;
}

static int __init hugetlb_init(void)
{
        unsigned long i;

        if (HPAGE_SHIFT == 0)
                return 0;

        for (i = 0; i < MAX_NUMNODES; ++i)
                INIT_LIST_HEAD(&hugepage_freelists[i]);

        for (i = 0; i < max_huge_pages; ++i) {
                if (!alloc_fresh_huge_page())
                        break;
        }
        max_huge_pages = free_huge_pages = nr_huge_pages = i;
        printk("Total HugeTLB memory allocated, %ld\n", free_huge_pages);
        return 0;
}
module_init(hugetlb_init);

static int __init hugetlb_setup(char *s)
{
        if (sscanf(s, "%lu", &max_huge_pages) <= 0)
                max_huge_pages = 0;
        return 1;
}
__setup("hugepages=", hugetlb_setup);

#ifdef CONFIG_SYSCTL
static void update_and_free_page(struct page *page)
{
        int i;
        nr_huge_pages--;
        nr_huge_pages_node[page_zone(page)->zone_pgdat->node_id]--;
        for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++) {
                page[i].flags &= ~(1 << PG_locked | 1 << PG_error | 1 << PG_referenced |
                                1 << PG_dirty | 1 << PG_active | 1 << PG_reserved |
                                1 << PG_private | 1<< PG_writeback);
        }
        page[1].lru.next = NULL;
        set_page_refcounted(page);
        __free_pages(page, HUGETLB_PAGE_ORDER);
}

#ifdef CONFIG_HIGHMEM
static void try_to_free_low(unsigned long count)
{
        int i, nid;
        for (i = 0; i < MAX_NUMNODES; ++i) {
                struct page *page, *next;
                list_for_each_entry_safe(page, next, &hugepage_freelists[i], lru) {
                        if (PageHighMem(page))
                                continue;
                        list_del(&page->lru);
                        update_and_free_page(page);
                        nid = page_zone(page)->zone_pgdat->node_id;
                        free_huge_pages--;
                        free_huge_pages_node[nid]--;
                        if (count >= nr_huge_pages)
                                return;
                }
        }
}
#else
static inline void try_to_free_low(unsigned long count)
{
}
#endif

static unsigned long set_max_huge_pages(unsigned long count)
{
        while (count > nr_huge_pages) {
                if (!alloc_fresh_huge_page())
                        return nr_huge_pages;
        }
        if (count >= nr_huge_pages)
                return nr_huge_pages;

        spin_lock(&hugetlb_lock);
        try_to_free_low(count);
        while (count < nr_huge_pages) {
                struct page *page = dequeue_huge_page(NULL, 0);
                if (!page)
                        break;
                update_and_free_page(page);
        }
        spin_unlock(&hugetlb_lock);
        return nr_huge_pages;
}

int hugetlb_sysctl_handler(struct ctl_table *table, int write,
                           struct file *file, void __user *buffer,
                           size_t *length, loff_t *ppos)
{
        proc_doulongvec_minmax(table, write, file, buffer, length, ppos);
        max_huge_pages = set_max_huge_pages(max_huge_pages);
        return 0;
}
#endif /* CONFIG_SYSCTL */

int hugetlb_report_meminfo(char *buf)
{
        return sprintf(buf,
                        "HugePages_Total: %5lu\n"
                        "HugePages_Free:  %5lu\n"
                        "Hugepagesize:    %5lu kB\n",
                        nr_huge_pages,
                        free_huge_pages,
                        HPAGE_SIZE/1024);
}

int hugetlb_report_node_meminfo(int nid, char *buf)
{
        return sprintf(buf,
                "Node %d HugePages_Total: %5u\n"
                "Node %d HugePages_Free:  %5u\n",
                nid, nr_huge_pages_node[nid],
                nid, free_huge_pages_node[nid]);
}

int is_hugepage_mem_enough(size_t size)
{
        return (size + ~HPAGE_MASK)/HPAGE_SIZE <= free_huge_pages;
}

/* Return the number pages of memory we physically have, in PAGE_SIZE units. */
unsigned long hugetlb_total_pages(void)
{
        return nr_huge_pages * (HPAGE_SIZE / PAGE_SIZE);
}

/*
 * We cannot handle pagefaults against hugetlb pages at all.  They cause
 * handle_mm_fault() to try to instantiate regular-sized pages in the
 * hugegpage VMA.  do_page_fault() is supposed to trap this, so BUG is we get
 * this far.
 */
static struct page *hugetlb_nopage(struct vm_area_struct *vma,
                                unsigned long address, int *unused)
{
        BUG();
        return NULL;
}

struct vm_operations_struct hugetlb_vm_ops = {
        .nopage = hugetlb_nopage,
};

static pte_t make_huge_pte(struct vm_area_struct *vma, struct page *page,
                                int writable)
{
        pte_t entry;

        if (writable) {
                entry =
                    pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
        } else {
                entry = pte_wrprotect(mk_pte(page, vma->vm_page_prot));
        }
        entry = pte_mkyoung(entry);
        entry = pte_mkhuge(entry);

        return entry;
}

static void set_huge_ptep_writable(struct vm_area_struct *vma,
                                   unsigned long address, pte_t *ptep)
{
        pte_t entry;

        entry = pte_mkwrite(pte_mkdirty(*ptep));
        ptep_set_access_flags(vma, address, ptep, entry, 1);
        update_mmu_cache(vma, address, entry);
        lazy_mmu_prot_update(entry);
}


int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
                            struct vm_area_struct *vma)
{
        pte_t *src_pte, *dst_pte, entry;
        struct page *ptepage;
        unsigned long addr;
        int cow;

        cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;

        for (addr = vma->vm_start; addr < vma->vm_end; addr += HPAGE_SIZE) {
                src_pte = huge_pte_offset(src, addr);
                if (!src_pte)
                        continue;
                dst_pte = huge_pte_alloc(dst, addr);
                if (!dst_pte)
                        goto nomem;
                spin_lock(&dst->page_table_lock);
                spin_lock(&src->page_table_lock);
                if (!pte_none(*src_pte)) {
                        if (cow)
                                ptep_set_wrprotect(src, addr, src_pte);
                        entry = *src_pte;
                        ptepage = pte_page(entry);
                        get_page(ptepage);
                        add_mm_counter(dst, file_rss, HPAGE_SIZE / PAGE_SIZE);
                        set_huge_pte_at(dst, addr, dst_pte, entry);
                }
                spin_unlock(&src->page_table_lock);
                spin_unlock(&dst->page_table_lock);
        }
        return 0;

nomem:
        return -ENOMEM;
}

void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
                          unsigned long end)
{
        struct mm_struct *mm = vma->vm_mm;
        unsigned long address;
        pte_t *ptep;
        pte_t pte;
        struct page *page;

        WARN_ON(!is_vm_hugetlb_page(vma));
        BUG_ON(start & ~HPAGE_MASK);
        BUG_ON(end & ~HPAGE_MASK);

        spin_lock(&mm->page_table_lock);

        /* Update high watermark before we lower rss */
        update_hiwater_rss(mm);

        for (address = start; address < end; address += HPAGE_SIZE) {
                ptep = huge_pte_offset(mm, address);
                if (!ptep)
                        continue;

                pte = huge_ptep_get_and_clear(mm, address, ptep);
                if (pte_none(pte))
                        continue;

                page = pte_page(pte);
                put_page(page);
                add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
        }

        spin_unlock(&mm->page_table_lock);
        flush_tlb_range(vma, start, end);
}

static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
                        unsigned long address, pte_t *ptep, pte_t pte)
{
        struct page *old_page, *new_page;
        int avoidcopy;

        old_page = pte_page(pte);

        /* If no-one else is actually using this page, avoid the copy
         * and just make the page writable */
        avoidcopy = (page_count(old_page) == 1);
        if (avoidcopy) {
                set_huge_ptep_writable(vma, address, ptep);
                return VM_FAULT_MINOR;
        }

        page_cache_get(old_page);
        new_page = alloc_huge_page(vma, address);

        if (!new_page) {
                page_cache_release(old_page);
                return VM_FAULT_OOM;
        }

        spin_unlock(&mm->page_table_lock);
        copy_huge_page(new_page, old_page, address);
        spin_lock(&mm->page_table_lock);

        ptep = huge_pte_offset(mm, address & HPAGE_MASK);
        if (likely(pte_same(*ptep, pte))) {
                /* Break COW */
                set_huge_pte_at(mm, address, ptep,
                                make_huge_pte(vma, new_page, 1));
                /* Make the old page be freed below */
                new_page = old_page;
        }
        page_cache_release(new_page);
        page_cache_release(old_page);
        return VM_FAULT_MINOR;
}

int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
                        unsigned long address, pte_t *ptep, int write_access)
{
        int ret = VM_FAULT_SIGBUS;
        unsigned long idx;
        unsigned long size;
        struct page *page;
        struct address_space *mapping;
        pte_t new_pte;

        mapping = vma->vm_file->f_mapping;
        idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
                + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));

        /*
         * Use page lock to guard against racing truncation
         * before we get page_table_lock.
         */
retry:
        page = find_lock_page(mapping, idx);
        if (!page) {
                if (hugetlb_get_quota(mapping))
                        goto out;
                page = alloc_huge_page(vma, address);
                if (!page) {
                        hugetlb_put_quota(mapping);
                        ret = VM_FAULT_OOM;
                        goto out;
                }
                clear_huge_page(page, address);

                if (vma->vm_flags & VM_SHARED) {
                        int err;

                        err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
                        if (err) {
                                put_page(page);
                                hugetlb_put_quota(mapping);
                                if (err == -EEXIST)
                                        goto retry;
                                goto out;
                        }
                } else
                        lock_page(page);
        }

        spin_lock(&mm->page_table_lock);
        size = i_size_read(mapping->host) >> HPAGE_SHIFT;
        if (idx >= size)
                goto backout;

        ret = VM_FAULT_MINOR;
        if (!pte_none(*ptep))
                goto backout;

        add_mm_counter(mm, file_rss, HPAGE_SIZE / PAGE_SIZE);
        new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)
                                && (vma->vm_flags & VM_SHARED)));
        set_huge_pte_at(mm, address, ptep, new_pte);

        if (write_access && !(vma->vm_flags & VM_SHARED)) {
                /* Optimization, do the COW without a second fault */
                ret = hugetlb_cow(mm, vma, address, ptep, new_pte);
        }

        spin_unlock(&mm->page_table_lock);
        unlock_page(page);
out:
        return ret;

backout:
        spin_unlock(&mm->page_table_lock);
        hugetlb_put_quota(mapping);
        unlock_page(page);
        put_page(page);
        goto out;
}

int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                        unsigned long address, int write_access)
{
        pte_t *ptep;
        pte_t entry;
        int ret;
        static DEFINE_MUTEX(hugetlb_instantiation_mutex);

        ptep = huge_pte_alloc(mm, address);
        if (!ptep)
                return VM_FAULT_OOM;

        /*
         * Serialize hugepage allocation and instantiation, so that we don't
         * get spurious allocation failures if two CPUs race to instantiate
         * the same page in the page cache.
         */
        mutex_lock(&hugetlb_instantiation_mutex);
        entry = *ptep;
        if (pte_none(entry)) {
                ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
                mutex_unlock(&hugetlb_instantiation_mutex);
                return ret;
        }

        ret = VM_FAULT_MINOR;

        spin_lock(&mm->page_table_lock);
        /* Check for a racing update before calling hugetlb_cow */
        if (likely(pte_same(entry, *ptep)))
                if (write_access && !pte_write(entry))
                        ret = hugetlb_cow(mm, vma, address, ptep, entry);
        spin_unlock(&mm->page_table_lock);
        mutex_unlock(&hugetlb_instantiation_mutex);

        return ret;
}

int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                        struct page **pages, struct vm_area_struct **vmas,
                        unsigned long *position, int *length, int i)
{
        unsigned long vpfn, vaddr = *position;
        int remainder = *length;

        vpfn = vaddr/PAGE_SIZE;
        spin_lock(&mm->page_table_lock);
        while (vaddr < vma->vm_end && remainder) {
                pte_t *pte;
                struct page *page;

                /*
                 * Some archs (sparc64, sh*) have multiple pte_ts to
                 * each hugepage.  We have to make * sure we get the
                 * first, for the page indexing below to work.
                 */
                pte = huge_pte_offset(mm, vaddr & HPAGE_MASK);

                if (!pte || pte_none(*pte)) {
                        int ret;

                        spin_unlock(&mm->page_table_lock);
                        ret = hugetlb_fault(mm, vma, vaddr, 0);
                        spin_lock(&mm->page_table_lock);
                        if (ret == VM_FAULT_MINOR)
                                continue;

                        remainder = 0;
                        if (!i)
                                i = -EFAULT;
                        break;
                }

                if (pages) {
                        page = &pte_page(*pte)[vpfn % (HPAGE_SIZE/PAGE_SIZE)];
                        get_page(page);
                        pages[i] = page;
                }

                if (vmas)
                        vmas[i] = vma;

                vaddr += PAGE_SIZE;
                ++vpfn;
                --remainder;
                ++i;
        }
        spin_unlock(&mm->page_table_lock);
        *length = remainder;
        *position = vaddr;

        return i;
}

void hugetlb_change_protection(struct vm_area_struct *vma,
                unsigned long address, unsigned long end, pgprot_t newprot)
{
        struct mm_struct *mm = vma->vm_mm;
        unsigned long start = address;
        pte_t *ptep;
        pte_t pte;

        BUG_ON(address >= end);
        flush_cache_range(vma, address, end);

        spin_lock(&mm->page_table_lock);
        for (; address < end; address += HPAGE_SIZE) {
                ptep = huge_pte_offset(mm, address);
                if (!ptep)
                        continue;
                if (!pte_none(*ptep)) {
                        pte = huge_ptep_get_and_clear(mm, address, ptep);
                        pte = pte_mkhuge(pte_modify(pte, newprot));
                        set_huge_pte_at(mm, address, ptep, pte);
                        lazy_mmu_prot_update(pte);
                }
        }
        spin_unlock(&mm->page_table_lock);

        flush_tlb_range(vma, start, end);
}