mm: provide a saner PTE walking API for modules

[mirror_ubuntu-hirsute-kernel.git] / mm / page_ext.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/memblock.h>
#include <linux/page_ext.h>
#include <linux/memory.h>
#include <linux/vmalloc.h>
#include <linux/kmemleak.h>
#include <linux/page_owner.h>
#include <linux/page_idle.h>

/*
 * struct page extension
 *
 * This is the feature to manage memory for extended data per page.
 *
 * Until now, we must modify struct page itself to store extra data per page.
 * This requires rebuilding the kernel and it is really time consuming process.
 * And, sometimes, rebuild is impossible due to third party module dependency.
 * At last, enlarging struct page could cause un-wanted system behaviour change.
 *
 * This feature is intended to overcome above mentioned problems. This feature
 * allocates memory for extended data per page in certain place rather than
 * the struct page itself. This memory can be accessed by the accessor
 * functions provided by this code. During the boot process, it checks whether
 * allocation of huge chunk of memory is needed or not. If not, it avoids
 * allocating memory at all. With this advantage, we can include this feature
 * into the kernel in default and can avoid rebuild and solve related problems.
 *
 * To help these things to work well, there are two callbacks for clients. One
 * is the need callback which is mandatory if user wants to avoid useless
 * memory allocation at boot-time. The other is optional, init callback, which
 * is used to do proper initialization after memory is allocated.
 *
 * The need callback is used to decide whether extended memory allocation is
 * needed or not. Sometimes users want to deactivate some features in this
 * boot and extra memory would be unnecessary. In this case, to avoid
 * allocating huge chunk of memory, each clients represent their need of
 * extra memory through the need callback. If one of the need callbacks
 * returns true, it means that someone needs extra memory so that
 * page extension core should allocates memory for page extension. If
 * none of need callbacks return true, memory isn't needed at all in this boot
 * and page extension core can skip to allocate memory. As result,
 * none of memory is wasted.
 *
 * When need callback returns true, page_ext checks if there is a request for
 * extra memory through size in struct page_ext_operations. If it is non-zero,
 * extra space is allocated for each page_ext entry and offset is returned to
 * user through offset in struct page_ext_operations.
 *
 * The init callback is used to do proper initialization after page extension
 * is completely initialized. In sparse memory system, extra memory is
 * allocated some time later than memmap is allocated. In other words, lifetime
 * of memory for page extension isn't same with memmap for struct page.
 * Therefore, clients can't store extra data until page extension is
 * initialized, even if pages are allocated and used freely. This could
 * cause inadequate state of extra data per page, so, to prevent it, client
 * can utilize this callback to initialize the state of it correctly.
 */

static struct page_ext_operations *page_ext_ops[] = {
#ifdef CONFIG_PAGE_OWNER
        &page_owner_ops,
#endif
#if defined(CONFIG_IDLE_PAGE_TRACKING) && !defined(CONFIG_64BIT)
        &page_idle_ops,
#endif
};

unsigned long page_ext_size = sizeof(struct page_ext);

static unsigned long total_usage;

static bool __init invoke_need_callbacks(void)
{
        int i;
        int entries = ARRAY_SIZE(page_ext_ops);
        bool need = false;

        for (i = 0; i < entries; i++) {
                if (page_ext_ops[i]->need && page_ext_ops[i]->need()) {
                        page_ext_ops[i]->offset = page_ext_size;
                        page_ext_size += page_ext_ops[i]->size;
                        need = true;
                }
        }

        return need;
}

static void __init invoke_init_callbacks(void)
{
        int i;
        int entries = ARRAY_SIZE(page_ext_ops);

        for (i = 0; i < entries; i++) {
                if (page_ext_ops[i]->init)
                        page_ext_ops[i]->init();
        }
}

#ifndef CONFIG_SPARSEMEM
void __init page_ext_init_flatmem_late(void)
{
        invoke_init_callbacks();
}
#endif

static inline struct page_ext *get_entry(void *base, unsigned long index)
{
        return base + page_ext_size * index;
}

#ifndef CONFIG_SPARSEMEM


void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
{
        pgdat->node_page_ext = NULL;
}

struct page_ext *lookup_page_ext(const struct page *page)
{
        unsigned long pfn = page_to_pfn(page);
        unsigned long index;
        struct page_ext *base;

        base = NODE_DATA(page_to_nid(page))->node_page_ext;
        /*
         * The sanity checks the page allocator does upon freeing a
         * page can reach here before the page_ext arrays are
         * allocated when feeding a range of pages to the allocator
         * for the first time during bootup or memory hotplug.
         */
        if (unlikely(!base))
                return NULL;
        index = pfn - round_down(node_start_pfn(page_to_nid(page)),
                                        MAX_ORDER_NR_PAGES);
        return get_entry(base, index);
}

static int __init alloc_node_page_ext(int nid)
{
        struct page_ext *base;
        unsigned long table_size;
        unsigned long nr_pages;

        nr_pages = NODE_DATA(nid)->node_spanned_pages;
        if (!nr_pages)
                return 0;

        /*
         * Need extra space if node range is not aligned with
         * MAX_ORDER_NR_PAGES. When page allocator's buddy algorithm
         * checks buddy's status, range could be out of exact node range.
         */
        if (!IS_ALIGNED(node_start_pfn(nid), MAX_ORDER_NR_PAGES) ||
                !IS_ALIGNED(node_end_pfn(nid), MAX_ORDER_NR_PAGES))
                nr_pages += MAX_ORDER_NR_PAGES;

        table_size = page_ext_size * nr_pages;

        base = memblock_alloc_try_nid(
                        table_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS),
                        MEMBLOCK_ALLOC_ACCESSIBLE, nid);
        if (!base)
                return -ENOMEM;
        NODE_DATA(nid)->node_page_ext = base;
        total_usage += table_size;
        return 0;
}

void __init page_ext_init_flatmem(void)
{

        int nid, fail;

        if (!invoke_need_callbacks())
                return;

        for_each_online_node(nid)  {
                fail = alloc_node_page_ext(nid);
                if (fail)
                        goto fail;
        }
        pr_info("allocated %ld bytes of page_ext\n", total_usage);
        return;

fail:
        pr_crit("allocation of page_ext failed.\n");
        panic("Out of memory");
}

#else /* CONFIG_FLAT_NODE_MEM_MAP */

struct page_ext *lookup_page_ext(const struct page *page)
{
        unsigned long pfn = page_to_pfn(page);
        struct mem_section *section = __pfn_to_section(pfn);
        /*
         * The sanity checks the page allocator does upon freeing a
         * page can reach here before the page_ext arrays are
         * allocated when feeding a range of pages to the allocator
         * for the first time during bootup or memory hotplug.
         */
        if (!section->page_ext)
                return NULL;
        return get_entry(section->page_ext, pfn);
}

static void *__meminit alloc_page_ext(size_t size, int nid)
{
        gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
        void *addr = NULL;

        addr = alloc_pages_exact_nid(nid, size, flags);
        if (addr) {
                kmemleak_alloc(addr, size, 1, flags);
                return addr;
        }

        addr = vzalloc_node(size, nid);

        return addr;
}

static int __meminit init_section_page_ext(unsigned long pfn, int nid)
{
        struct mem_section *section;
        struct page_ext *base;
        unsigned long table_size;

        section = __pfn_to_section(pfn);

        if (section->page_ext)
                return 0;

        table_size = page_ext_size * PAGES_PER_SECTION;
        base = alloc_page_ext(table_size, nid);

        /*
         * The value stored in section->page_ext is (base - pfn)
         * and it does not point to the memory block allocated above,
         * causing kmemleak false positives.
         */
        kmemleak_not_leak(base);

        if (!base) {
                pr_err("page ext allocation failure\n");
                return -ENOMEM;
        }

        /*
         * The passed "pfn" may not be aligned to SECTION.  For the calculation
         * we need to apply a mask.
         */
        pfn &= PAGE_SECTION_MASK;
        section->page_ext = (void *)base - page_ext_size * pfn;
        total_usage += table_size;
        return 0;
}
#ifdef CONFIG_MEMORY_HOTPLUG
static void free_page_ext(void *addr)
{
        if (is_vmalloc_addr(addr)) {
                vfree(addr);
        } else {
                struct page *page = virt_to_page(addr);
                size_t table_size;

                table_size = page_ext_size * PAGES_PER_SECTION;

                BUG_ON(PageReserved(page));
                kmemleak_free(addr);
                free_pages_exact(addr, table_size);
        }
}

static void __free_page_ext(unsigned long pfn)
{
        struct mem_section *ms;
        struct page_ext *base;

        ms = __pfn_to_section(pfn);
        if (!ms || !ms->page_ext)
                return;
        base = get_entry(ms->page_ext, pfn);
        free_page_ext(base);
        ms->page_ext = NULL;
}

static int __meminit online_page_ext(unsigned long start_pfn,
                                unsigned long nr_pages,
                                int nid)
{
        unsigned long start, end, pfn;
        int fail = 0;

        start = SECTION_ALIGN_DOWN(start_pfn);
        end = SECTION_ALIGN_UP(start_pfn + nr_pages);

        if (nid == NUMA_NO_NODE) {
                /*
                 * In this case, "nid" already exists and contains valid memory.
                 * "start_pfn" passed to us is a pfn which is an arg for
                 * online__pages(), and start_pfn should exist.
                 */
                nid = pfn_to_nid(start_pfn);
                VM_BUG_ON(!node_state(nid, N_ONLINE));
        }

        for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION)
                fail = init_section_page_ext(pfn, nid);
        if (!fail)
                return 0;

        /* rollback */
        for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
                __free_page_ext(pfn);

        return -ENOMEM;
}

static int __meminit offline_page_ext(unsigned long start_pfn,
                                unsigned long nr_pages, int nid)
{
        unsigned long start, end, pfn;

        start = SECTION_ALIGN_DOWN(start_pfn);
        end = SECTION_ALIGN_UP(start_pfn + nr_pages);

        for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
                __free_page_ext(pfn);
        return 0;

}

static int __meminit page_ext_callback(struct notifier_block *self,
                               unsigned long action, void *arg)
{
        struct memory_notify *mn = arg;
        int ret = 0;

        switch (action) {
        case MEM_GOING_ONLINE:
                ret = online_page_ext(mn->start_pfn,
                                   mn->nr_pages, mn->status_change_nid);
                break;
        case MEM_OFFLINE:
                offline_page_ext(mn->start_pfn,
                                mn->nr_pages, mn->status_change_nid);
                break;
        case MEM_CANCEL_ONLINE:
                offline_page_ext(mn->start_pfn,
                                mn->nr_pages, mn->status_change_nid);
                break;
        case MEM_GOING_OFFLINE:
                break;
        case MEM_ONLINE:
        case MEM_CANCEL_OFFLINE:
                break;
        }

        return notifier_from_errno(ret);
}

#endif

void __init page_ext_init(void)
{
        unsigned long pfn;
        int nid;

        if (!invoke_need_callbacks())
                return;

        for_each_node_state(nid, N_MEMORY) {
                unsigned long start_pfn, end_pfn;

                start_pfn = node_start_pfn(nid);
                end_pfn = node_end_pfn(nid);
                /*
                 * start_pfn and end_pfn may not be aligned to SECTION and the
                 * page->flags of out of node pages are not initialized.  So we
                 * scan [start_pfn, the biggest section's pfn < end_pfn) here.
                 */
                for (pfn = start_pfn; pfn < end_pfn;
                        pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {

                        if (!pfn_valid(pfn))
                                continue;
                        /*
                         * Nodes's pfns can be overlapping.
                         * We know some arch can have a nodes layout such as
                         * -------------pfn-------------->
                         * N0 | N1 | N2 | N0 | N1 | N2|....
                         */
                        if (pfn_to_nid(pfn) != nid)
                                continue;
                        if (init_section_page_ext(pfn, nid))
                                goto oom;
                        cond_resched();
                }
        }
        hotplug_memory_notifier(page_ext_callback, 0);
        pr_info("allocated %ld bytes of page_ext\n", total_usage);
        invoke_init_callbacks();
        return;

oom:
        panic("Out of memory");
}

void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
{
}

#endif