// SPDX-License-Identifier: GPL-2.0
/*
 * SLUB: A slab allocator that limits cache line use instead of queuing
 * objects in per cpu and per node lists.
 *
 * The allocator synchronizes using per slab locks or atomic operatios
 * and only uses a centralized lock to manage a pool of partial slabs.
 *
 * (C) 2007 SGI, Christoph Lameter
 * (C) 2011 Linux Foundation, Christoph Lameter
 */

#include <linux/mm.h>
#include <linux/swap.h> /* struct reclaim_state */
#include <linux/module.h>
#include <linux/bit_spinlock.h>
#include <linux/interrupt.h>
#include <linux/bitops.h>
#include <linux/slab.h>
#include "slab.h"
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kasan.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/mempolicy.h>
#include <linux/ctype.h>
#include <linux/debugobjects.h>
#include <linux/kallsyms.h>
#include <linux/memory.h>
#include <linux/math64.h>
#include <linux/fault-inject.h>
#include <linux/stacktrace.h>
#include <linux/prefetch.h>
#include <linux/memcontrol.h>
#include <linux/random.h>

#include <trace/events/kmem.h>

#include "internal.h"

/*
 * Lock order:
 *   1. slab_mutex (Global Mutex)
 *   2. node->list_lock
 *   3. slab_lock(page) (Only on some arches and for debugging)
 *
 *   slab_mutex
 *
 *   The role of the slab_mutex is to protect the list of all the slabs
 *   and to synchronize major metadata changes to slab cache structures.
 *
 *   The slab_lock is only used for debugging and on arches that do not
 *   have the ability to do a cmpxchg_double. It only protects:
 *      A. page->freelist       -> List of object free in a page
 *      B. page->inuse          -> Number of objects in use
 *      C. page->objects        -> Number of objects in page
 *      D. page->frozen         -> frozen state
 *
 *   If a slab is frozen then it is exempt from list management. It is not
 *   on any list except per cpu partial list. The processor that froze the
 *   slab is the one who can perform list operations on the page. Other
 *   processors may put objects onto the freelist but the processor that
 *   froze the slab is the only one that can retrieve the objects from the
 *   page's freelist.
 *
 *   The list_lock protects the partial and full list on each node and
 *   the partial slab counter. If taken then no new slabs may be added or
 *   removed from the lists nor make the number of partial slabs be modified.
 *   (Note that the total number of slabs is an atomic value that may be
 *   modified without taking the list lock).
 *
 *   The list_lock is a centralized lock and thus we avoid taking it as
 *   much as possible. As long as SLUB does not have to handle partial
 *   slabs, operations can continue without any centralized lock. F.e.
 *   allocating a long series of objects that fill up slabs does not require
 *   the list lock.
 *   Interrupts are disabled during allocation and deallocation in order to
 *   make the slab allocator safe to use in the context of an irq. In addition
 *   interrupts are disabled to ensure that the processor does not change
 *   while handling per_cpu slabs, due to kernel preemption.
 *
 * SLUB assigns one slab for allocation to each processor.
 * Allocations only occur from these slabs called cpu slabs.
 *
 * Slabs with free elements are kept on a partial list and during regular
 * operations no list for full slabs is used. If an object in a full slab is
 * freed then the slab will show up again on the partial lists.
 * We track full slabs for debugging purposes though because otherwise we
 * cannot scan all objects.
 *
 * Slabs are freed when they become empty. Teardown and setup is
 * minimal so we rely on the page allocators per cpu caches for
 * fast frees and allocs.
 *
 * Overloading of page flags that are otherwise used for LRU management.
 *
 * PageActive           The slab is frozen and exempt from list processing.
 *                      This means that the slab is dedicated to a purpose
 *                      such as satisfying allocations for a specific
 *                      processor. Objects may be freed in the slab while
 *                      it is frozen but slab_free will then skip the usual
 *                      list operations. It is up to the processor holding
 *                      the slab to integrate the slab into the slab lists
 *                      when the slab is no longer needed.
 *
 *                      One use of this flag is to mark slabs that are
 *                      used for allocations. Then such a slab becomes a cpu
 *                      slab. The cpu slab may be equipped with an additional
 *                      freelist that allows lockless access to
 *                      free objects in addition to the regular freelist
 *                      that requires the slab lock.
 *
 * PageError            Slab requires special handling due to debug
 *                      options set. This moves slab handling out of
 *                      the fast path and disables lockless freelists.
 */

static inline int kmem_cache_debug(struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_DEBUG
        return unlikely(s->flags & SLAB_DEBUG_FLAGS);
#else
        return 0;
#endif
}

void *fixup_red_left(struct kmem_cache *s, void *p)
{
        if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
                p += s->red_left_pad;

        return p;
}

static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
{
#ifdef CONFIG_SLUB_CPU_PARTIAL
        return !kmem_cache_debug(s);
#else
        return false;
#endif
}

/*
 * Issues still to be resolved:
 *
 * - Support PAGE_ALLOC_DEBUG. Should be easy to do.
 *
 * - Variable sizing of the per node arrays
 */

/* Enable to test recovery from slab corruption on boot */
#undef SLUB_RESILIENCY_TEST

/* Enable to log cmpxchg failures */
#undef SLUB_DEBUG_CMPXCHG

/*
 * Mininum number of partial slabs. These will be left on the partial
 * lists even if they are empty. kmem_cache_shrink may reclaim them.
 */
#define MIN_PARTIAL 5

/*
 * Maximum number of desirable partial slabs.
 * The existence of more partial slabs makes kmem_cache_shrink
 * sort the partial list by the number of objects in use.
 */
#define MAX_PARTIAL 10

#define DEBUG_DEFAULT_FLAGS (SLAB_CONSISTENCY_CHECKS | SLAB_RED_ZONE | \
                                SLAB_POISON | SLAB_STORE_USER)

/*
 * These debug flags cannot use CMPXCHG because there might be consistency
 * issues when checking or reading debug information
 */
#define SLAB_NO_CMPXCHG (SLAB_CONSISTENCY_CHECKS | SLAB_STORE_USER | \
                                SLAB_TRACE)


/*
 * Debugging flags that require metadata to be stored in the slab.  These get
 * disabled when slub_debug=O is used and a cache's min order increases with
 * metadata.
 */
#define DEBUG_METADATA_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)

#define OO_SHIFT        16
#define OO_MASK         ((1 << OO_SHIFT) - 1)
#define MAX_OBJS_PER_PAGE       32767 /* since page.objects is u15 */

/* Internal SLUB flags */
/* Poison object */
#define __OBJECT_POISON         ((slab_flags_t __force)0x80000000U)
/* Use cmpxchg_double */
#define __CMPXCHG_DOUBLE        ((slab_flags_t __force)0x40000000U)

/*
 * Tracking user of a slab.
 */
#define TRACK_ADDRS_COUNT 16
struct track {
        unsigned long addr;     /* Called from address */
#ifdef CONFIG_STACKTRACE
        unsigned long addrs[TRACK_ADDRS_COUNT]; /* Called from address */
#endif
        int cpu;                /* Was running on cpu */
        int pid;                /* Pid context */
        unsigned long when;     /* When did the operation occur */
};

enum track_item { TRACK_ALLOC, TRACK_FREE };

#ifdef CONFIG_SYSFS
static int sysfs_slab_add(struct kmem_cache *);
static int sysfs_slab_alias(struct kmem_cache *, const char *);
static void memcg_propagate_slab_attrs(struct kmem_cache *s);
static void sysfs_slab_remove(struct kmem_cache *s);
#else
static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; }
static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
                                                        { return 0; }
static inline void memcg_propagate_slab_attrs(struct kmem_cache *s) { }
static inline void sysfs_slab_remove(struct kmem_cache *s) { }
#endif

static inline void stat(const struct kmem_cache *s, enum stat_item si)
{
#ifdef CONFIG_SLUB_STATS
        /*
         * The rmw is racy on a preemptible kernel but this is acceptable, so
         * avoid this_cpu_add()'s irq-disable overhead.
         */
        raw_cpu_inc(s->cpu_slab->stat[si]);
#endif
}

/********************************************************************
 *                      Core slab cache functions
 *******************************************************************/

/*
 * Returns freelist pointer (ptr). With hardening, this is obfuscated
 * with an XOR of the address where the pointer is held and a per-cache
 * random number.
 */
static inline void *freelist_ptr(const struct kmem_cache *s, void *ptr,
                                 unsigned long ptr_addr)
{
#ifdef CONFIG_SLAB_FREELIST_HARDENED
        /*
         * When CONFIG_KASAN_SW_TAGS is enabled, ptr_addr might be tagged.
         * Normally, this doesn't cause any issues, as both set_freepointer()
         * and get_freepointer() are called with a pointer with the same tag.
         * However, there are some issues with CONFIG_SLUB_DEBUG code. For
         * example, when __free_slub() iterates over objects in a cache, it
         * passes untagged pointers to check_object(). check_object() in turns
         * calls get_freepointer() with an untagged pointer, which causes the
         * freepointer to be restored incorrectly.
         */
        return (void *)((unsigned long)ptr ^ s->random ^
                        (unsigned long)kasan_reset_tag((void *)ptr_addr));
#else
        return ptr;
#endif
}

/* Returns the freelist pointer recorded at location ptr_addr. */
static inline void *freelist_dereference(const struct kmem_cache *s,
                                         void *ptr_addr)
{
        return freelist_ptr(s, (void *)*(unsigned long *)(ptr_addr),
                            (unsigned long)ptr_addr);
}

static inline void *get_freepointer(struct kmem_cache *s, void *object)
{
        return freelist_dereference(s, object + s->offset);
}

static void prefetch_freepointer(const struct kmem_cache *s, void *object)
{
        prefetch(object + s->offset);
}

static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)
{
        unsigned long freepointer_addr;
        void *p;

        if (!debug_pagealloc_enabled())
                return get_freepointer(s, object);

        freepointer_addr = (unsigned long)object + s->offset;
        probe_kernel_read(&p, (void **)freepointer_addr, sizeof(p));
        return freelist_ptr(s, p, freepointer_addr);
}

static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
{
        unsigned long freeptr_addr = (unsigned long)object + s->offset;

#ifdef CONFIG_SLAB_FREELIST_HARDENED
        BUG_ON(object == fp); /* naive detection of double free or corruption */
#endif

        *(void **)freeptr_addr = freelist_ptr(s, fp, freeptr_addr);
}

/* Loop over all objects in a slab */
#define for_each_object(__p, __s, __addr, __objects) \
        for (__p = fixup_red_left(__s, __addr); \
                __p < (__addr) + (__objects) * (__s)->size; \
                __p += (__s)->size)

/* Determine object index from a given position */
static inline unsigned int slab_index(void *p, struct kmem_cache *s, void *addr)
{
        return (kasan_reset_tag(p) - addr) / s->size;
}

static inline unsigned int order_objects(unsigned int order, unsigned int size)
{
        return ((unsigned int)PAGE_SIZE << order) / size;
}

static inline struct kmem_cache_order_objects oo_make(unsigned int order,
                unsigned int size)
{
        struct kmem_cache_order_objects x = {
                (order << OO_SHIFT) + order_objects(order, size)
        };

        return x;
}

static inline unsigned int oo_order(struct kmem_cache_order_objects x)
{
        return x.x >> OO_SHIFT;
}

static inline unsigned int oo_objects(struct kmem_cache_order_objects x)
{
        return x.x & OO_MASK;
}

/*
 * Per slab locking using the pagelock
 */
static __always_inline void slab_lock(struct page *page)
{
        VM_BUG_ON_PAGE(PageTail(page), page);
        bit_spin_lock(PG_locked, &page->flags);
}

static __always_inline void slab_unlock(struct page *page)
{
        VM_BUG_ON_PAGE(PageTail(page), page);
        __bit_spin_unlock(PG_locked, &page->flags);
}

/* Interrupts must be disabled (for the fallback code to work right) */
static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
                void *freelist_old, unsigned long counters_old,
                void *freelist_new, unsigned long counters_new,
                const char *n)
{
        VM_BUG_ON(!irqs_disabled());
#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
        if (s->flags & __CMPXCHG_DOUBLE) {
                if (cmpxchg_double(&page->freelist, &page->counters,
                                   freelist_old, counters_old,
                                   freelist_new, counters_new))
                        return true;
        } else
#endif
        {
                slab_lock(page);
                if (page->freelist == freelist_old &&
                                        page->counters == counters_old) {
                        page->freelist = freelist_new;
                        page->counters = counters_new;
                        slab_unlock(page);
                        return true;
                }
                slab_unlock(page);
        }

        cpu_relax();
        stat(s, CMPXCHG_DOUBLE_FAIL);

#ifdef SLUB_DEBUG_CMPXCHG
        pr_info("%s %s: cmpxchg double redo ", n, s->name);
#endif

        return false;
}

static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
                void *freelist_old, unsigned long counters_old,
                void *freelist_new, unsigned long counters_new,
                const char *n)
{
#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
        if (s->flags & __CMPXCHG_DOUBLE) {
                if (cmpxchg_double(&page->freelist, &page->counters,
                                   freelist_old, counters_old,
                                   freelist_new, counters_new))
                        return true;
        } else
#endif
        {
                unsigned long flags;

                local_irq_save(flags);
                slab_lock(page);
                if (page->freelist == freelist_old &&
                                        page->counters == counters_old) {
                        page->freelist = freelist_new;
                        page->counters = counters_new;
                        slab_unlock(page);
                        local_irq_restore(flags);
                        return true;
                }
                slab_unlock(page);
                local_irq_restore(flags);
        }

        cpu_relax();
        stat(s, CMPXCHG_DOUBLE_FAIL);

#ifdef SLUB_DEBUG_CMPXCHG
        pr_info("%s %s: cmpxchg double redo ", n, s->name);
#endif

        return false;
}

#ifdef CONFIG_SLUB_DEBUG
/*
 * Determine a map of object in use on a page.
 *
 * Node listlock must be held to guarantee that the page does
 * not vanish from under us.
 */
static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map)
{
        void *p;
        void *addr = page_address(page);

        for (p = page->freelist; p; p = get_freepointer(s, p))
                set_bit(slab_index(p, s, addr), map);
}

static inline unsigned int size_from_object(struct kmem_cache *s)
{
        if (s->flags & SLAB_RED_ZONE)
                return s->size - s->red_left_pad;

        return s->size;
}

static inline void *restore_red_left(struct kmem_cache *s, void *p)
{
        if (s->flags & SLAB_RED_ZONE)
                p -= s->red_left_pad;

        return p;
}

/*
 * Debug settings:
 */
#if defined(CONFIG_SLUB_DEBUG_ON)
static slab_flags_t slub_debug = DEBUG_DEFAULT_FLAGS;
#else
static slab_flags_t slub_debug;
#endif

static char *slub_debug_slabs;
static int disable_higher_order_debug;

/*
 * slub is about to manipulate internal object metadata.  This memory lies
 * outside the range of the allocated object, so accessing it would normally
 * be reported by kasan as a bounds error.  metadata_access_enable() is used
 * to tell kasan that these accesses are OK.
 */
static inline void metadata_access_enable(void)
{
        kasan_disable_current();
}

static inline void metadata_access_disable(void)
{
        kasan_enable_current();
}

/*
 * Object debugging
 */

/* Verify that a pointer has an address that is valid within a slab page */
static inline int check_valid_pointer(struct kmem_cache *s,
                                struct page *page, void *object)
{
        void *base;

        if (!object)
                return 1;

        base = page_address(page);
        object = kasan_reset_tag(object);
        object = restore_red_left(s, object);
        if (object < base || object >= base + page->objects * s->size ||
                (object - base) % s->size) {
                return 0;
        }

        return 1;
}

static void print_section(char *level, char *text, u8 *addr,
                          unsigned int length)
{
        metadata_access_enable();
        print_hex_dump(level, text, DUMP_PREFIX_ADDRESS, 16, 1, addr,
                        length, 1);
        metadata_access_disable();
}

static struct track *get_track(struct kmem_cache *s, void *object,
        enum track_item alloc)
{
        struct track *p;

        if (s->offset)
                p = object + s->offset + sizeof(void *);
        else
                p = object + s->inuse;

        return p + alloc;
}

static void set_track(struct kmem_cache *s, void *object,
                        enum track_item alloc, unsigned long addr)
{
        struct track *p = get_track(s, object, alloc);

        if (addr) {
#ifdef CONFIG_STACKTRACE
                unsigned int nr_entries;

                metadata_access_enable();
                nr_entries = stack_trace_save(p->addrs, TRACK_ADDRS_COUNT, 3);
                metadata_access_disable();

                if (nr_entries < TRACK_ADDRS_COUNT)
                        p->addrs[nr_entries] = 0;
#endif
                p->addr = addr;
                p->cpu = smp_processor_id();
                p->pid = current->pid;
                p->when = jiffies;
        } else {
                memset(p, 0, sizeof(struct track));
        }
}

static void init_tracking(struct kmem_cache *s, void *object)
{
        if (!(s->flags & SLAB_STORE_USER))
                return;

        set_track(s, object, TRACK_FREE, 0UL);
        set_track(s, object, TRACK_ALLOC, 0UL);
}

static void print_track(const char *s, struct track *t, unsigned long pr_time)
{
        if (!t->addr)
                return;

        pr_err("INFO: %s in %pS age=%lu cpu=%u pid=%d\n",
               s, (void *)t->addr, pr_time - t->when, t->cpu, t->pid);
#ifdef CONFIG_STACKTRACE
        {
                int i;
                for (i = 0; i < TRACK_ADDRS_COUNT; i++)
                        if (t->addrs[i])
                                pr_err("\t%pS\n", (void *)t->addrs[i]);
                        else
                                break;
        }
#endif
}

static void print_tracking(struct kmem_cache *s, void *object)
{
        unsigned long pr_time = jiffies;
        if (!(s->flags & SLAB_STORE_USER))
                return;

        print_track("Allocated", get_track(s, object, TRACK_ALLOC), pr_time);
        print_track("Freed", get_track(s, object, TRACK_FREE), pr_time);
}

static void print_page_info(struct page *page)
{
        pr_err("INFO: Slab 0x%p objects=%u used=%u fp=0x%p flags=0x%04lx\n",
               page, page->objects, page->inuse, page->freelist, page->flags);

}

static void slab_bug(struct kmem_cache *s, char *fmt, ...)
{
        struct va_format vaf;
        va_list args;

        va_start(args, fmt);
        vaf.fmt = fmt;
        vaf.va = &args;
        pr_err("=============================================================================\n");
        pr_err("BUG %s (%s): %pV\n", s->name, print_tainted(), &vaf);
        pr_err("-----------------------------------------------------------------------------\n\n");

        add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
        va_end(args);
}

static void slab_fix(struct kmem_cache *s, char *fmt, ...)
{
        struct va_format vaf;
        va_list args;

        va_start(args, fmt);
        vaf.fmt = fmt;
        vaf.va = &args;
        pr_err("FIX %s: %pV\n", s->name, &vaf);
        va_end(args);
}

static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
{
        unsigned int off;       /* Offset of last byte */
        u8 *addr = page_address(page);

        print_tracking(s, p);

        print_page_info(page);

        pr_err("INFO: Object 0x%p @offset=%tu fp=0x%p\n\n",
               p, p - addr, get_freepointer(s, p));

        if (s->flags & SLAB_RED_ZONE)
                print_section(KERN_ERR, "Redzone ", p - s->red_left_pad,
                              s->red_left_pad);
        else if (p > addr + 16)
                print_section(KERN_ERR, "Bytes b4 ", p - 16, 16);

        print_section(KERN_ERR, "Object ", p,
                      min_t(unsigned int, s->object_size, PAGE_SIZE));
        if (s->flags & SLAB_RED_ZONE)
                print_section(KERN_ERR, "Redzone ", p + s->object_size,
                        s->inuse - s->object_size);

        if (s->offset)
                off = s->offset + sizeof(void *);
        else
                off = s->inuse;

        if (s->flags & SLAB_STORE_USER)
                off += 2 * sizeof(struct track);

        off += kasan_metadata_size(s);

        if (off != size_from_object(s))
                /* Beginning of the filler is the free pointer */
                print_section(KERN_ERR, "Padding ", p + off,
                              size_from_object(s) - off);

        dump_stack();
}

void object_err(struct kmem_cache *s, struct page *page,
                        u8 *object, char *reason)
{
        slab_bug(s, "%s", reason);
        print_trailer(s, page, object);
}

static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
                        const char *fmt, ...)
{
        va_list args;
        char buf[100];

        va_start(args, fmt);
        vsnprintf(buf, sizeof(buf), fmt, args);
        va_end(args);
        slab_bug(s, "%s", buf);
        print_page_info(page);
        dump_stack();
}

static void init_object(struct kmem_cache *s, void *object, u8 val)
{
        u8 *p = object;

        if (s->flags & SLAB_RED_ZONE)
                memset(p - s->red_left_pad, val, s->red_left_pad);

        if (s->flags & __OBJECT_POISON) {
                memset(p, POISON_FREE, s->object_size - 1);
                p[s->object_size - 1] = POISON_END;
        }

        if (s->flags & SLAB_RED_ZONE)
                memset(p + s->object_size, val, s->inuse - s->object_size);
}

static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
                                                void *from, void *to)
{
        slab_fix(s, "Restoring 0x%p-0x%p=0x%x\n", from, to - 1, data);
        memset(from, data, to - from);
}

static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
                        u8 *object, char *what,
                        u8 *start, unsigned int value, unsigned int bytes)
{
        u8 *fault;
        u8 *end;

        metadata_access_enable();
        fault = memchr_inv(start, value, bytes);
        metadata_access_disable();
        if (!fault)
                return 1;

        end = start + bytes;
        while (end > fault && end[-1] == value)
                end--;

        slab_bug(s, "%s overwritten", what);
        pr_err("INFO: 0x%p-0x%p. First byte 0x%x instead of 0x%x\n",
                                        fault, end - 1, fault[0], value);
        print_trailer(s, page, object);

        restore_bytes(s, what, value, fault, end);
        return 0;
}

/*
 * Object layout:
 *
 * object address
 *      Bytes of the object to be managed.
 *      If the freepointer may overlay the object then the free
 *      pointer is the first word of the object.
 *
 *      Poisoning uses 0x6b (POISON_FREE) and the last byte is
 *      0xa5 (POISON_END)
 *
 * object + s->object_size
 *      Padding to reach word boundary. This is also used for Redzoning.
 *      Padding is extended by another word if Redzoning is enabled and
 *      object_size == inuse.
 *
 *      We fill with 0xbb (RED_INACTIVE) for inactive objects and with
 *      0xcc (RED_ACTIVE) for objects in use.
 *
 * object + s->inuse
 *      Meta data starts here.
 *
 *      A. Free pointer (if we cannot overwrite object on free)
 *      B. Tracking data for SLAB_STORE_USER
 *      C. Padding to reach required alignment boundary or at mininum
 *              one word if debugging is on to be able to detect writes
 *              before the word boundary.
 *
 *      Padding is done using 0x5a (POISON_INUSE)
 *
 * object + s->size
 *      Nothing is used beyond s->size.
 *
 * If slabcaches are merged then the object_size and inuse boundaries are mostly
 * ignored. And therefore no slab options that rely on these boundaries
 * may be used with merged slabcaches.
 */

static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
{
        unsigned long off = s->inuse;   /* The end of info */

        if (s->offset)
                /* Freepointer is placed after the object. */
                off += sizeof(void *);

        if (s->flags & SLAB_STORE_USER)
                /* We also have user information there */
                off += 2 * sizeof(struct track);

        off += kasan_metadata_size(s);

        if (size_from_object(s) == off)
                return 1;

        return check_bytes_and_report(s, page, p, "Object padding",
                        p + off, POISON_INUSE, size_from_object(s) - off);
}

/* Check the pad bytes at the end of a slab page */
static int slab_pad_check(struct kmem_cache *s, struct page *page)
{
        u8 *start;
        u8 *fault;
        u8 *end;
        u8 *pad;
        int length;
        int remainder;

        if (!(s->flags & SLAB_POISON))
                return 1;

        start = page_address(page);
        length = PAGE_SIZE << compound_order(page);
        end = start + length;
        remainder = length % s->size;
        if (!remainder)
                return 1;

        pad = end - remainder;
        metadata_access_enable();
        fault = memchr_inv(pad, POISON_INUSE, remainder);
        metadata_access_disable();
        if (!fault)
                return 1;
        while (end > fault && end[-1] == POISON_INUSE)
                end--;

        slab_err(s, page, "Padding overwritten. 0x%p-0x%p", fault, end - 1);
        print_section(KERN_ERR, "Padding ", pad, remainder);

        restore_bytes(s, "slab padding", POISON_INUSE, fault, end);
        return 0;
}

static int check_object(struct kmem_cache *s, struct page *page,
                                        void *object, u8 val)
{
        u8 *p = object;
        u8 *endobject = object + s->object_size;

        if (s->flags & SLAB_RED_ZONE) {
                if (!check_bytes_and_report(s, page, object, "Redzone",
                        object - s->red_left_pad, val, s->red_left_pad))
                        return 0;

                if (!check_bytes_and_report(s, page, object, "Redzone",
                        endobject, val, s->inuse - s->object_size))
                        return 0;
        } else {
                if ((s->flags & SLAB_POISON) && s->object_size < s->inuse) {
                        check_bytes_and_report(s, page, p, "Alignment padding",
                                endobject, POISON_INUSE,
                                s->inuse - s->object_size);
                }
        }

        if (s->flags & SLAB_POISON) {
                if (val != SLUB_RED_ACTIVE && (s->flags & __OBJECT_POISON) &&
                        (!check_bytes_and_report(s, page, p, "Poison", p,
                                        POISON_FREE, s->object_size - 1) ||
                         !check_bytes_and_report(s, page, p, "Poison",
                                p + s->object_size - 1, POISON_END, 1)))
                        return 0;
                /*
                 * check_pad_bytes cleans up on its own.
                 */
                check_pad_bytes(s, page, p);
        }

        if (!s->offset && val == SLUB_RED_ACTIVE)
                /*
                 * Object and freepointer overlap. Cannot check
                 * freepointer while object is allocated.
                 */
                return 1;

        /* Check free pointer validity */
        if (!check_valid_pointer(s, page, get_freepointer(s, p))) {
                object_err(s, page, p, "Freepointer corrupt");
                /*
                 * No choice but to zap it and thus lose the remainder
                 * of the free objects in this slab. May cause
                 * another error because the object count is now wrong.
                 */
                set_freepointer(s, p, NULL);
                return 0;
        }
        return 1;
}

static int check_slab(struct kmem_cache *s, struct page *page)
{
        int maxobj;

        VM_BUG_ON(!irqs_disabled());

        if (!PageSlab(page)) {
                slab_err(s, page, "Not a valid slab page");
                return 0;
        }

        maxobj = order_objects(compound_order(page), s->size);
        if (page->objects > maxobj) {
                slab_err(s, page, "objects %u > max %u",
                        page->objects, maxobj);
                return 0;
        }
        if (page->inuse > page->objects) {
                slab_err(s, page, "inuse %u > max %u",
                        page->inuse, page->objects);
                return 0;
        }
        /* Slab_pad_check fixes things up after itself */
        slab_pad_check(s, page);
        return 1;
}

/*
 * Determine if a certain object on a page is on the freelist. Must hold the
 * slab lock to guarantee that the chains are in a consistent state.
 */
static int on_freelist(struct kmem_cache *s, struct page *page, void *search)
{
        int nr = 0;
        void *fp;
        void *object = NULL;
        int max_objects;

        fp = page->freelist;
        while (fp && nr <= page->objects) {
                if (fp == search)
                        return 1;
                if (!check_valid_pointer(s, page, fp)) {
                        if (object) {
                                object_err(s, page, object,
                                        "Freechain corrupt");
                                set_freepointer(s, object, NULL);
                        } else {
                                slab_err(s, page, "Freepointer corrupt");
                                page->freelist = NULL;
                                page->inuse = page->objects;
                                slab_fix(s, "Freelist cleared");
                                return 0;
                        }
                        break;
                }
                object = fp;
                fp = get_freepointer(s, object);
                nr++;
        }

        max_objects = order_objects(compound_order(page), s->size);
        if (max_objects > MAX_OBJS_PER_PAGE)
                max_objects = MAX_OBJS_PER_PAGE;

        if (page->objects != max_objects) {
                slab_err(s, page, "Wrong number of objects. Found %d but should be %d",
                         page->objects, max_objects);
                page->objects = max_objects;
                slab_fix(s, "Number of objects adjusted.");
        }
        if (page->inuse != page->objects - nr) {
                slab_err(s, page, "Wrong object count. Counter is %d but counted were %d",
                         page->inuse, page->objects - nr);
                page->inuse = page->objects - nr;
                slab_fix(s, "Object count adjusted.");
        }
        return search == NULL;
}

static void trace(struct kmem_cache *s, struct page *page, void *object,
                                                                int alloc)
{
        if (s->flags & SLAB_TRACE) {
                pr_info("TRACE %s %s 0x%p inuse=%d fp=0x%p\n",
                        s->name,
                        alloc ? "alloc" : "free",
                        object, page->inuse,
                        page->freelist);

                if (!alloc)

                        print_section(KERN_INFO, "Object ", (void *)object,
                                        s->object_size);

                dump_stack();
        }
}

/*
 * Tracking of fully allocated slabs for debugging purposes.
 */
static void add_full(struct kmem_cache *s,
        struct kmem_cache_node *n, struct page *page)
{
        if (!(s->flags & SLAB_STORE_USER))
                return;

        lockdep_assert_held(&n->list_lock);
        list_add(&page->slab_list, &n->full);
}

static void remove_full(struct kmem_cache *s, struct kmem_cache_node *n, struct page *page)
{
        if (!(s->flags & SLAB_STORE_USER))
                return;

        lockdep_assert_held(&n->list_lock);
        list_del(&page->slab_list);
}

/* Tracking of the number of slabs for debugging purposes */
static inline unsigned long slabs_node(struct kmem_cache *s, int node)
{
        struct kmem_cache_node *n = get_node(s, node);

        return atomic_long_read(&n->nr_slabs);
}

static inline unsigned long node_nr_slabs(struct kmem_cache_node *n)
{
        return atomic_long_read(&n->nr_slabs);
}

static inline void inc_slabs_node(struct kmem_cache *s, int node, int objects)
{
        struct kmem_cache_node *n = get_node(s, node);

        /*
         * May be called early in order to allocate a slab for the
         * kmem_cache_node structure. Solve the chicken-egg
         * dilemma by deferring the increment of the count during
         * bootstrap (see early_kmem_cache_node_alloc).
         */
        if (likely(n)) {
                atomic_long_inc(&n->nr_slabs);
                atomic_long_add(objects, &n->total_objects);
        }
}
static inline void dec_slabs_node(struct kmem_cache *s, int node, int objects)
{
        struct kmem_cache_node *n = get_node(s, node);

        atomic_long_dec(&n->nr_slabs);
        atomic_long_sub(objects, &n->total_objects);
}

/* Object debug checks for alloc/free paths */
static void setup_object_debug(struct kmem_cache *s, struct page *page,
                                                                void *object)
{
        if (!(s->flags & (SLAB_STORE_USER|SLAB_RED_ZONE|__OBJECT_POISON)))
                return;

        init_object(s, object, SLUB_RED_INACTIVE);
        init_tracking(s, object);
}

static void setup_page_debug(struct kmem_cache *s, void *addr, int order)
{
        if (!(s->flags & SLAB_POISON))
                return;

        metadata_access_enable();
        memset(addr, POISON_INUSE, PAGE_SIZE << order);
        metadata_access_disable();
}

static inline int alloc_consistency_checks(struct kmem_cache *s,
                                        struct page *page, void *object)
{
        if (!check_slab(s, page))
                return 0;

        if (!check_valid_pointer(s, page, object)) {
                object_err(s, page, object, "Freelist Pointer check fails");
                return 0;
        }

        if (!check_object(s, page, object, SLUB_RED_INACTIVE))
                return 0;

        return 1;
}

static noinline int alloc_debug_processing(struct kmem_cache *s,
                                        struct page *page,
                                        void *object, unsigned long addr)
{
        if (s->flags & SLAB_CONSISTENCY_CHECKS) {
                if (!alloc_consistency_checks(s, page, object))
                        goto bad;
        }

        /* Success perform special debug activities for allocs */
        if (s->flags & SLAB_STORE_USER)
                set_track(s, object, TRACK_ALLOC, addr);
        trace(s, page, object, 1);
        init_object(s, object, SLUB_RED_ACTIVE);
        return 1;

bad:
        if (PageSlab(page)) {
                /*
                 * If this is a slab page then lets do the best we can
                 * to avoid issues in the future. Marking all objects
                 * as used avoids touching the remaining objects.
                 */
                slab_fix(s, "Marking all objects used");
                page->inuse = page->objects;
                page->freelist = NULL;
        }
        return 0;
}

static inline int free_consistency_checks(struct kmem_cache *s,
                struct page *page, void *object, unsigned long addr)
{
        if (!check_valid_pointer(s, page, object)) {
                slab_err(s, page, "Invalid object pointer 0x%p", object);
                return 0;
        }

        if (on_freelist(s, page, object)) {
                object_err(s, page, object, "Object already free");
                return 0;
        }

        if (!check_object(s, page, object, SLUB_RED_ACTIVE))
                return 0;

        if (unlikely(s != page->slab_cache)) {
                if (!PageSlab(page)) {
                        slab_err(s, page, "Attempt to free object(0x%p) outside of slab",
                                 object);
                } else if (!page->slab_cache) {
                        pr_err("SLUB <none>: no slab for object 0x%p.\n",
                               object);
                        dump_stack();
                } else
                        object_err(s, page, object,
                                        "page slab pointer corrupt.");
                return 0;
        }
        return 1;
}

/* Supports checking bulk free of a constructed freelist */
static noinline int free_debug_processing(
        struct kmem_cache *s, struct page *page,
        void *head, void *tail, int bulk_cnt,
        unsigned long addr)
{
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));
        void *object = head;
        int cnt = 0;
        unsigned long uninitialized_var(flags);
        int ret = 0;

        spin_lock_irqsave(&n->list_lock, flags);
        slab_lock(page);

        if (s->flags & SLAB_CONSISTENCY_CHECKS) {
                if (!check_slab(s, page))
                        goto out;
        }

next_object:
        cnt++;

        if (s->flags & SLAB_CONSISTENCY_CHECKS) {
                if (!free_consistency_checks(s, page, object, addr))
                        goto out;
        }

        if (s->flags & SLAB_STORE_USER)
                set_track(s, object, TRACK_FREE, addr);
        trace(s, page, object, 0);
        /* Freepointer not overwritten by init_object(), SLAB_POISON moved it */
        init_object(s, object, SLUB_RED_INACTIVE);

        /* Reached end of constructed freelist yet? */
        if (object != tail) {
                object = get_freepointer(s, object);
                goto next_object;
        }
        ret = 1;

out:
        if (cnt != bulk_cnt)
                slab_err(s, page, "Bulk freelist count(%d) invalid(%d)\n",
                         bulk_cnt, cnt);

        slab_unlock(page);
        spin_unlock_irqrestore(&n->list_lock, flags);
        if (!ret)
                slab_fix(s, "Object at 0x%p not freed", object);
        return ret;
}

static int __init setup_slub_debug(char *str)
{
        slub_debug = DEBUG_DEFAULT_FLAGS;
        if (*str++ != '=' || !*str)
                /*
                 * No options specified. Switch on full debugging.
                 */
                goto out;

        if (*str == ',')
                /*
                 * No options but restriction on slabs. This means full
                 * debugging for slabs matching a pattern.
                 */
                goto check_slabs;

        slub_debug = 0;
        if (*str == '-')
                /*
                 * Switch off all debugging measures.
                 */
                goto out;

        /*
         * Determine which debug features should be switched on
         */
        for (; *str && *str != ','; str++) {
                switch (tolower(*str)) {
                case 'f':
                        slub_debug |= SLAB_CONSISTENCY_CHECKS;
                        break;
                case 'z':
                        slub_debug |= SLAB_RED_ZONE;
                        break;
                case 'p':
                        slub_debug |= SLAB_POISON;
                        break;
                case 'u':
                        slub_debug |= SLAB_STORE_USER;
                        break;
                case 't':
                        slub_debug |= SLAB_TRACE;
                        break;
                case 'a':
                        slub_debug |= SLAB_FAILSLAB;
                        break;
                case 'o':
                        /*
                         * Avoid enabling debugging on caches if its minimum
                         * order would increase as a result.
                         */
                        disable_higher_order_debug = 1;
                        break;
                default:
                        pr_err("slub_debug option '%c' unknown. skipped\n",
                               *str);
                }
        }

check_slabs:
        if (*str == ',')
                slub_debug_slabs = str + 1;
out:
        if ((static_branch_unlikely(&init_on_alloc) ||
             static_branch_unlikely(&init_on_free)) &&
            (slub_debug & SLAB_POISON))
                pr_info("mem auto-init: SLAB_POISON will take precedence over init_on_alloc/init_on_free\n");
        return 1;
}

__setup("slub_debug", setup_slub_debug);

/*
 * kmem_cache_flags - apply debugging options to the cache
 * @object_size:        the size of an object without meta data
 * @flags:              flags to set
 * @name:               name of the cache
 * @ctor:               constructor function
 *
 * Debug option(s) are applied to @flags. In addition to the debug
 * option(s), if a slab name (or multiple) is specified i.e.
 * slub_debug=<Debug-Options>,<slab name1>,<slab name2> ...
 * then only the select slabs will receive the debug option(s).
 */
slab_flags_t kmem_cache_flags(unsigned int object_size,
        slab_flags_t flags, const char *name,
        void (*ctor)(void *))
{
        char *iter;
        size_t len;

        /* If slub_debug = 0, it folds into the if conditional. */
        if (!slub_debug_slabs)
                return flags | slub_debug;

        len = strlen(name);
        iter = slub_debug_slabs;
        while (*iter) {
                char *end, *glob;
                size_t cmplen;

                end = strchrnul(iter, ',');

                glob = strnchr(iter, end - iter, '*');
                if (glob)
                        cmplen = glob - iter;
                else
                        cmplen = max_t(size_t, len, (end - iter));

                if (!strncmp(name, iter, cmplen)) {
                        flags |= slub_debug;
                        break;
                }

                if (!*end)
                        break;
                iter = end + 1;
        }

        return flags;
}
#else /* !CONFIG_SLUB_DEBUG */
static inline void setup_object_debug(struct kmem_cache *s,
                        struct page *page, void *object) {}
static inline void setup_page_debug(struct kmem_cache *s,
                        void *addr, int order) {}

static inline int alloc_debug_processing(struct kmem_cache *s,
        struct page *page, void *object, unsigned long addr) { return 0; }

static inline int free_debug_processing(
        struct kmem_cache *s, struct page *page,
        void *head, void *tail, int bulk_cnt,
        unsigned long addr) { return 0; }

static inline int slab_pad_check(struct kmem_cache *s, struct page *page)
                        { return 1; }
static inline int check_object(struct kmem_cache *s, struct page *page,
                        void *object, u8 val) { return 1; }
static inline void add_full(struct kmem_cache *s, struct kmem_cache_node *n,
                                        struct page *page) {}
static inline void remove_full(struct kmem_cache *s, struct kmem_cache_node *n,
                                        struct page *page) {}
slab_flags_t kmem_cache_flags(unsigned int object_size,
        slab_flags_t flags, const char *name,
        void (*ctor)(void *))
{
        return flags;
}
#define slub_debug 0

#define disable_higher_order_debug 0

static inline unsigned long slabs_node(struct kmem_cache *s, int node)
                                                        { return 0; }
static inline unsigned long node_nr_slabs(struct kmem_cache_node *n)
                                                        { return 0; }
static inline void inc_slabs_node(struct kmem_cache *s, int node,
                                                        int objects) {}
static inline void dec_slabs_node(struct kmem_cache *s, int node,
                                                        int objects) {}

#endif /* CONFIG_SLUB_DEBUG */

/*
 * Hooks for other subsystems that check memory allocations. In a typical
 * production configuration these hooks all should produce no code at all.
 */
static inline void *kmalloc_large_node_hook(void *ptr, size_t size, gfp_t flags)
{
        ptr = kasan_kmalloc_large(ptr, size, flags);
        /* As ptr might get tagged, call kmemleak hook after KASAN. */
        kmemleak_alloc(ptr, size, 1, flags);
        return ptr;
}

static __always_inline void kfree_hook(void *x)
{
        kmemleak_free(x);
        kasan_kfree_large(x, _RET_IP_);
}

static __always_inline bool slab_free_hook(struct kmem_cache *s, void *x)
{
        kmemleak_free_recursive(x, s->flags);

        /*
         * Trouble is that we may no longer disable interrupts in the fast path
         * So in order to make the debug calls that expect irqs to be
         * disabled we need to disable interrupts temporarily.
         */
#ifdef CONFIG_LOCKDEP
        {
                unsigned long flags;

                local_irq_save(flags);
                debug_check_no_locks_freed(x, s->object_size);
                local_irq_restore(flags);
        }
#endif
        if (!(s->flags & SLAB_DEBUG_OBJECTS))
                debug_check_no_obj_freed(x, s->object_size);

        /* KASAN might put x into memory quarantine, delaying its reuse */
        return kasan_slab_free(s, x, _RET_IP_);
}

static inline bool slab_free_freelist_hook(struct kmem_cache *s,
                                           void **head, void **tail)
{

        void *object;
        void *next = *head;
        void *old_tail = *tail ? *tail : *head;
        int rsize;

        if (slab_want_init_on_free(s)) {
                void *p = NULL;

                do {
                        object = next;
                        next = get_freepointer(s, object);
                        /*
                         * Clear the object and the metadata, but don't touch
                         * the redzone.
                         */
                        memset(object, 0, s->object_size);
                        rsize = (s->flags & SLAB_RED_ZONE) ? s->red_left_pad
                                                           : 0;
                        memset((char *)object + s->inuse, 0,
                               s->size - s->inuse - rsize);
                        set_freepointer(s, object, p);
                        p = object;
                } while (object != old_tail);
        }

/*
 * Compiler cannot detect this function can be removed if slab_free_hook()
 * evaluates to nothing.  Thus, catch all relevant config debug options here.
 */
#if defined(CONFIG_LOCKDEP)     ||              \
        defined(CONFIG_DEBUG_KMEMLEAK) ||       \
        defined(CONFIG_DEBUG_OBJECTS_FREE) ||   \
        defined(CONFIG_KASAN)

        next = *head;

        /* Head and tail of the reconstructed freelist */
        *head = NULL;
        *tail = NULL;

        do {
                object = next;
                next = get_freepointer(s, object);
                /* If object's reuse doesn't have to be delayed */
                if (!slab_free_hook(s, object)) {
                        /* Move object to the new freelist */
                        set_freepointer(s, object, *head);
                        *head = object;
                        if (!*tail)
                                *tail = object;
                }
        } while (object != old_tail);

        if (*head == *tail)
                *tail = NULL;

        return *head != NULL;
#else
        return true;
#endif
}

static void *setup_object(struct kmem_cache *s, struct page *page,
                                void *object)
{
        setup_object_debug(s, page, object);
        object = kasan_init_slab_obj(s, object);
        if (unlikely(s->ctor)) {
                kasan_unpoison_object_data(s, object);
                s->ctor(object);
                kasan_poison_object_data(s, object);
        }
        return object;
}

/*
 * Slab allocation and freeing
 */
static inline struct page *alloc_slab_page(struct kmem_cache *s,
                gfp_t flags, int node, struct kmem_cache_order_objects oo)
{
        struct page *page;
        unsigned int order = oo_order(oo);

        if (node == NUMA_NO_NODE)
                page = alloc_pages(flags, order);
        else
                page = __alloc_pages_node(node, flags, order);

        if (page && charge_slab_page(page, flags, order, s)) {
                __free_pages(page, order);
                page = NULL;
        }

        return page;
}

#ifdef CONFIG_SLAB_FREELIST_RANDOM
/* Pre-initialize the random sequence cache */
static int init_cache_random_seq(struct kmem_cache *s)
{
        unsigned int count = oo_objects(s->oo);
        int err;

        /* Bailout if already initialised */
        if (s->random_seq)
                return 0;

        err = cache_random_seq_create(s, count, GFP_KERNEL);
        if (err) {
                pr_err("SLUB: Unable to initialize free list for %s\n",
                        s->name);
                return err;
        }

        /* Transform to an offset on the set of pages */
        if (s->random_seq) {
                unsigned int i;

                for (i = 0; i < count; i++)
                        s->random_seq[i] *= s->size;
        }
        return 0;
}

/* Initialize each random sequence freelist per cache */
static void __init init_freelist_randomization(void)
{
        struct kmem_cache *s;

        mutex_lock(&slab_mutex);

        list_for_each_entry(s, &slab_caches, list)
                init_cache_random_seq(s);

        mutex_unlock(&slab_mutex);
}

/* Get the next entry on the pre-computed freelist randomized */
static void *next_freelist_entry(struct kmem_cache *s, struct page *page,
                                unsigned long *pos, void *start,
                                unsigned long page_limit,
                                unsigned long freelist_count)
{
        unsigned int idx;

        /*
         * If the target page allocation failed, the number of objects on the
         * page might be smaller than the usual size defined by the cache.
         */
        do {
                idx = s->random_seq[*pos];
                *pos += 1;
                if (*pos >= freelist_count)
                        *pos = 0;
        } while (unlikely(idx >= page_limit));

        return (char *)start + idx;
}

/* Shuffle the single linked freelist based on a random pre-computed sequence */
static bool shuffle_freelist(struct kmem_cache *s, struct page *page)
{
        void *start;
        void *cur;
        void *next;
        unsigned long idx, pos, page_limit, freelist_count;

        if (page->objects < 2 || !s->random_seq)
                return false;

        freelist_count = oo_objects(s->oo);
        pos = get_random_int() % freelist_count;

        page_limit = page->objects * s->size;
        start = fixup_red_left(s, page_address(page));

        /* First entry is used as the base of the freelist */
        cur = next_freelist_entry(s, page, &pos, start, page_limit,
                                freelist_count);
        cur = setup_object(s, page, cur);
        page->freelist = cur;

        for (idx = 1; idx < page->objects; idx++) {
                next = next_freelist_entry(s, page, &pos, start, page_limit,
                        freelist_count);
                next = setup_object(s, page, next);
                set_freepointer(s, cur, next);
                cur = next;
        }
        set_freepointer(s, cur, NULL);

        return true;
}
#else
static inline int init_cache_random_seq(struct kmem_cache *s)
{
        return 0;
}
static inline void init_freelist_randomization(void) { }
static inline bool shuffle_freelist(struct kmem_cache *s, struct page *page)
{
        return false;
}
#endif /* CONFIG_SLAB_FREELIST_RANDOM */

static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
{
        struct page *page;
        struct kmem_cache_order_objects oo = s->oo;
        gfp_t alloc_gfp;
        void *start, *p, *next;
        int idx, order;
        bool shuffle;

        flags &= gfp_allowed_mask;

        if (gfpflags_allow_blocking(flags))
                local_irq_enable();

        flags |= s->allocflags;

        /*
         * Let the initial higher-order allocation fail under memory pressure
         * so we fall-back to the minimum order allocation.
         */
        alloc_gfp = (flags | __GFP_NOWARN | __GFP_NORETRY) & ~__GFP_NOFAIL;
        if ((alloc_gfp & __GFP_DIRECT_RECLAIM) && oo_order(oo) > oo_order(s->min))
                alloc_gfp = (alloc_gfp | __GFP_NOMEMALLOC) & ~(__GFP_RECLAIM|__GFP_NOFAIL);

        page = alloc_slab_page(s, alloc_gfp, node, oo);
        if (unlikely(!page)) {
                oo = s->min;
                alloc_gfp = flags;
                /*
                 * Allocation may have failed due to fragmentation.
                 * Try a lower order alloc if possible
                 */
                page = alloc_slab_page(s, alloc_gfp, node, oo);
                if (unlikely(!page))
                        goto out;
                stat(s, ORDER_FALLBACK);
        }

        page->objects = oo_objects(oo);

        order = compound_order(page);
        page->slab_cache = s;
        __SetPageSlab(page);
        if (page_is_pfmemalloc(page))
                SetPageSlabPfmemalloc(page);

        kasan_poison_slab(page);

        start = page_address(page);

        setup_page_debug(s, start, order);

        shuffle = shuffle_freelist(s, page);

        if (!shuffle) {
                start = fixup_red_left(s, start);
                start = setup_object(s, page, start);
                page->freelist = start;
                for (idx = 0, p = start; idx < page->objects - 1; idx++) {
                        next = p + s->size;
                        next = setup_object(s, page, next);
                        set_freepointer(s, p, next);
                        p = next;
                }
                set_freepointer(s, p, NULL);
        }

        page->inuse = page->objects;
        page->frozen = 1;

out:
        if (gfpflags_allow_blocking(flags))
                local_irq_disable();
        if (!page)
                return NULL;

        inc_slabs_node(s, page_to_nid(page), page->objects);

        return page;
}

static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
{
        if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
                gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
                flags &= ~GFP_SLAB_BUG_MASK;
                pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n",
                                invalid_mask, &invalid_mask, flags, &flags);
                dump_stack();
        }

        return allocate_slab(s,
                flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
}

static void __free_slab(struct kmem_cache *s, struct page *page)
{
        int order = compound_order(page);
        int pages = 1 << order;

        if (s->flags & SLAB_CONSISTENCY_CHECKS) {
                void *p;

                slab_pad_check(s, page);
                for_each_object(p, s, page_address(page),
                                                page->objects)
                        check_object(s, page, p, SLUB_RED_INACTIVE);
        }

        __ClearPageSlabPfmemalloc(page);
        __ClearPageSlab(page);

        page->mapping = NULL;
        if (current->reclaim_state)
                current->reclaim_state->reclaimed_slab += pages;
        uncharge_slab_page(page, order, s);
        __free_pages(page, order);
}

static void rcu_free_slab(struct rcu_head *h)
{
        struct page *page = container_of(h, struct page, rcu_head);

        __free_slab(page->slab_cache, page);
}

static void free_slab(struct kmem_cache *s, struct page *page)
{
        if (unlikely(s->flags & SLAB_TYPESAFE_BY_RCU)) {
                call_rcu(&page->rcu_head, rcu_free_slab);
        } else
                __free_slab(s, page);
}

static void discard_slab(struct kmem_cache *s, struct page *page)
{
        dec_slabs_node(s, page_to_nid(page), page->objects);
        free_slab(s, page);
}

/*
 * Management of partially allocated slabs.
 */
static inline void
__add_partial(struct kmem_cache_node *n, struct page *page, int tail)
{
        n->nr_partial++;
        if (tail == DEACTIVATE_TO_TAIL)
                list_add_tail(&page->slab_list, &n->partial);
        else
                list_add(&page->slab_list, &n->partial);
}

static inline void add_partial(struct kmem_cache_node *n,
                                struct page *page, int tail)
{
        lockdep_assert_held(&n->list_lock);
        __add_partial(n, page, tail);
}

static inline void remove_partial(struct kmem_cache_node *n,
                                        struct page *page)
{
        lockdep_assert_held(&n->list_lock);
        list_del(&page->slab_list);
        n->nr_partial--;
}

/*
 * Remove slab from the partial list, freeze it and
 * return the pointer to the freelist.
 *
 * Returns a list of objects or NULL if it fails.
 */
static inline void *acquire_slab(struct kmem_cache *s,
                struct kmem_cache_node *n, struct page *page,
                int mode, int *objects)
{
        void *freelist;
        unsigned long counters;
        struct page new;

        lockdep_assert_held(&n->list_lock);

        /*
         * Zap the freelist and set the frozen bit.
         * The old freelist is the list of objects for the
         * per cpu allocation list.
         */
        freelist = page->freelist;
        counters = page->counters;
        new.counters = counters;
        *objects = new.objects - new.inuse;
        if (mode) {
                new.inuse = page->objects;
                new.freelist = NULL;
        } else {
                new.freelist = freelist;
        }

        VM_BUG_ON(new.frozen);
        new.frozen = 1;

        if (!__cmpxchg_double_slab(s, page,
                        freelist, counters,
                        new.freelist, new.counters,
                        "acquire_slab"))
                return NULL;

        remove_partial(n, page);
        WARN_ON(!freelist);
        return freelist;
}

static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain);
static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags);

/*
 * Try to allocate a partial slab from a specific node.
 */
static void *get_partial_node(struct kmem_cache *s, struct kmem_cache_node *n,
                                struct kmem_cache_cpu *c, gfp_t flags)
{
        struct page *page, *page2;
        void *object = NULL;
        unsigned int available = 0;
        int objects;

        /*
         * Racy check. If we mistakenly see no partial slabs then we
         * just allocate an empty slab. If we mistakenly try to get a
         * partial slab and there is none available then get_partials()
         * will return NULL.
         */
        if (!n || !n->nr_partial)
                return NULL;

        spin_lock(&n->list_lock);
        list_for_each_entry_safe(page, page2, &n->partial, slab_list) {
                void *t;

                if (!pfmemalloc_match(page, flags))
                        continue;

                t = acquire_slab(s, n, page, object == NULL, &objects);
                if (!t)
                        break;

                available += objects;
                if (!object) {
                        c->page = page;
                        stat(s, ALLOC_FROM_PARTIAL);
                        object = t;
                } else {
                        put_cpu_partial(s, page, 0);
                        stat(s, CPU_PARTIAL_NODE);
                }
                if (!kmem_cache_has_cpu_partial(s)
                        || available > slub_cpu_partial(s) / 2)
                        break;

        }
        spin_unlock(&n->list_lock);
        return object;
}

/*
 * Get a page from somewhere. Search in increasing NUMA distances.
 */
static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
                struct kmem_cache_cpu *c)
{
#ifdef CONFIG_NUMA
        struct zonelist *zonelist;
        struct zoneref *z;
        struct zone *zone;
        enum zone_type high_zoneidx = gfp_zone(flags);
        void *object;
        unsigned int cpuset_mems_cookie;

        /*
         * The defrag ratio allows a configuration of the tradeoffs between
         * inter node defragmentation and node local allocations. A lower
         * defrag_ratio increases the tendency to do local allocations
         * instead of attempting to obtain partial slabs from other nodes.
         *
         * If the defrag_ratio is set to 0 then kmalloc() always
         * returns node local objects. If the ratio is higher then kmalloc()
         * may return off node objects because partial slabs are obtained
         * from other nodes and filled up.
         *
         * If /sys/kernel/slab/xx/remote_node_defrag_ratio is set to 100
         * (which makes defrag_ratio = 1000) then every (well almost)
         * allocation will first attempt to defrag slab caches on other nodes.
         * This means scanning over all nodes to look for partial slabs which
         * may be expensive if we do it every time we are trying to find a slab
         * with available objects.
         */
        if (!s->remote_node_defrag_ratio ||
                        get_cycles() % 1024 > s->remote_node_defrag_ratio)
                return NULL;

        do {
                cpuset_mems_cookie = read_mems_allowed_begin();
                zonelist = node_zonelist(mempolicy_slab_node(), flags);
                for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
                        struct kmem_cache_node *n;

                        n = get_node(s, zone_to_nid(zone));

                        if (n && cpuset_zone_allowed(zone, flags) &&
                                        n->nr_partial > s->min_partial) {
                                object = get_partial_node(s, n, c, flags);
                                if (object) {
                                        /*
                                         * Don't check read_mems_allowed_retry()
                                         * here - if mems_allowed was updated in
                                         * parallel, that was a harmless race
                                         * between allocation and the cpuset
                                         * update
                                         */
                                        return object;
                                }
                        }
                }
        } while (read_mems_allowed_retry(cpuset_mems_cookie));
#endif  /* CONFIG_NUMA */
        return NULL;
}

/*
 * Get a partial page, lock it and return it.
 */
static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
                struct kmem_cache_cpu *c)
{
        void *object;
        int searchnode = node;

        if (node == NUMA_NO_NODE)
                searchnode = numa_mem_id();
        else if (!node_present_pages(node))
                searchnode = node_to_mem_node(node);

        object = get_partial_node(s, get_node(s, searchnode), c, flags);
        if (object || node != NUMA_NO_NODE)
                return object;

        return get_any_partial(s, flags, c);
}

#ifdef CONFIG_PREEMPT
/*
 * Calculate the next globally unique transaction for disambiguiation
 * during cmpxchg. The transactions start with the cpu number and are then
 * incremented by CONFIG_NR_CPUS.
 */
#define TID_STEP  roundup_pow_of_two(CONFIG_NR_CPUS)
#else
/*
 * No preemption supported therefore also no need to check for
 * different cpus.
 */
#define TID_STEP 1
#endif

static inline unsigned long next_tid(unsigned long tid)
{
        return tid + TID_STEP;
}

static inline unsigned int tid_to_cpu(unsigned long tid)
{
        return tid % TID_STEP;
}

static inline unsigned long tid_to_event(unsigned long tid)
{
        return tid / TID_STEP;
}

static inline unsigned int init_tid(int cpu)
{
        return cpu;
}

static inline void note_cmpxchg_failure(const char *n,
                const struct kmem_cache *s, unsigned long tid)
{
#ifdef SLUB_DEBUG_CMPXCHG
        unsigned long actual_tid = __this_cpu_read(s->cpu_slab->tid);

        pr_info("%s %s: cmpxchg redo ", n, s->name);

#ifdef CONFIG_PREEMPT
        if (tid_to_cpu(tid) != tid_to_cpu(actual_tid))
                pr_warn("due to cpu change %d -> %d\n",
                        tid_to_cpu(tid), tid_to_cpu(actual_tid));
        else
#endif
        if (tid_to_event(tid) != tid_to_event(actual_tid))
                pr_warn("due to cpu running other code. Event %ld->%ld\n",
                        tid_to_event(tid), tid_to_event(actual_tid));
        else
                pr_warn("for unknown reason: actual=%lx was=%lx target=%lx\n",
                        actual_tid, tid, next_tid(tid));
#endif
        stat(s, CMPXCHG_DOUBLE_CPU_FAIL);
}

static void init_kmem_cache_cpus(struct kmem_cache *s)
{
        int cpu;

        for_each_possible_cpu(cpu)
                per_cpu_ptr(s->cpu_slab, cpu)->tid = init_tid(cpu);
}

/*
 * Remove the cpu slab
 */
static void deactivate_slab(struct kmem_cache *s, struct page *page,
                                void *freelist, struct kmem_cache_cpu *c)
{
        enum slab_modes { M_NONE, M_PARTIAL, M_FULL, M_FREE };
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));
        int lock = 0;
        enum slab_modes l = M_NONE, m = M_NONE;
        void *nextfree;
        int tail = DEACTIVATE_TO_HEAD;
        struct page new;
        struct page old;

        if (page->freelist) {
                stat(s, DEACTIVATE_REMOTE_FREES);
                tail = DEACTIVATE_TO_TAIL;
        }

        /*
         * Stage one: Free all available per cpu objects back
         * to the page freelist while it is still frozen. Leave the
         * last one.
         *
         * There is no need to take the list->lock because the page
         * is still frozen.
         */
        while (freelist && (nextfree = get_freepointer(s, freelist))) {
                void *prior;
                unsigned long counters;

                do {
                        prior = page->freelist;
                        counters = page->counters;
                        set_freepointer(s, freelist, prior);
                        new.counters = counters;
                        new.inuse--;
                        VM_BUG_ON(!new.frozen);

                } while (!__cmpxchg_double_slab(s, page,
                        prior, counters,
                        freelist, new.counters,
                        "drain percpu freelist"));

                freelist = nextfree;
        }

        /*
         * Stage two: Ensure that the page is unfrozen while the
         * list presence reflects the actual number of objects
         * during unfreeze.
         *
         * We setup the list membership and then perform a cmpxchg
         * with the count. If there is a mismatch then the page
         * is not unfrozen but the page is on the wrong list.
         *
         * Then we restart the process which may have to remove
         * the page from the list that we just put it on again
         * because the number of objects in the slab may have
         * changed.
         */
redo:

        old.freelist = page->freelist;
        old.counters = page->counters;
        VM_BUG_ON(!old.frozen);

        /* Determine target state of the slab */
        new.counters = old.counters;
        if (freelist) {
                new.inuse--;
                set_freepointer(s, freelist, old.freelist);
                new.freelist = freelist;
        } else
                new.freelist = old.freelist;

        new.frozen = 0;

        if (!new.inuse && n->nr_partial >= s->min_partial)
                m = M_FREE;
        else if (new.freelist) {
                m = M_PARTIAL;
                if (!lock) {
                        lock = 1;
                        /*
                         * Taking the spinlock removes the possibility
                         * that acquire_slab() will see a slab page that
                         * is frozen
                         */
                        spin_lock(&n->list_lock);
                }
        } else {
                m = M_FULL;
                if (kmem_cache_debug(s) && !lock) {
                        lock = 1;
                        /*
                         * This also ensures that the scanning of full
                         * slabs from diagnostic functions will not see
                         * any frozen slabs.
                         */
                        spin_lock(&n->list_lock);
                }
        }

        if (l != m) {
                if (l == M_PARTIAL)
                        remove_partial(n, page);
                else if (l == M_FULL)
                        remove_full(s, n, page);

                if (m == M_PARTIAL)
                        add_partial(n, page, tail);
                else if (m == M_FULL)
                        add_full(s, n, page);
        }

        l = m;
        if (!__cmpxchg_double_slab(s, page,
                                old.freelist, old.counters,
                                new.freelist, new.counters,
                                "unfreezing slab"))
                goto redo;

        if (lock)
                spin_unlock(&n->list_lock);

        if (m == M_PARTIAL)
                stat(s, tail);
        else if (m == M_FULL)
                stat(s, DEACTIVATE_FULL);
        else if (m == M_FREE) {
                stat(s, DEACTIVATE_EMPTY);
                discard_slab(s, page);
                stat(s, FREE_SLAB);
        }

        c->page = NULL;
        c->freelist = NULL;
}

/*
 * Unfreeze all the cpu partial slabs.
 *
 * This function must be called with interrupts disabled
 * for the cpu using c (or some other guarantee must be there
 * to guarantee no concurrent accesses).
 */
static void unfreeze_partials(struct kmem_cache *s,
                struct kmem_cache_cpu *c)
{
#ifdef CONFIG_SLUB_CPU_PARTIAL
        struct kmem_cache_node *n = NULL, *n2 = NULL;
        struct page *page, *discard_page = NULL;

        while ((page = c->partial)) {
                struct page new;
                struct page old;

                c->partial = page->next;

                n2 = get_node(s, page_to_nid(page));
                if (n != n2) {
                        if (n)
                                spin_unlock(&n->list_lock);

                        n = n2;
                        spin_lock(&n->list_lock);
                }

                do {

                        old.freelist = page->freelist;
                        old.counters = page->counters;
                        VM_BUG_ON(!old.frozen);

                        new.counters = old.counters;
                        new.freelist = old.freelist;

                        new.frozen = 0;

                } while (!__cmpxchg_double_slab(s, page,
                                old.freelist, old.counters,
                                new.freelist, new.counters,
                                "unfreezing slab"));

                if (unlikely(!new.inuse && n->nr_partial >= s->min_partial)) {
                        page->next = discard_page;
                        discard_page = page;
                } else {
                        add_partial(n, page, DEACTIVATE_TO_TAIL);
                        stat(s, FREE_ADD_PARTIAL);
                }
        }

        if (n)
                spin_unlock(&n->list_lock);

        while (discard_page) {
                page = discard_page;
                discard_page = discard_page->next;

                stat(s, DEACTIVATE_EMPTY);
                discard_slab(s, page);
                stat(s, FREE_SLAB);
        }
#endif  /* CONFIG_SLUB_CPU_PARTIAL */
}

/*
 * Put a page that was just frozen (in __slab_free|get_partial_node) into a
 * partial page slot if available.
 *
 * If we did not find a slot then simply move all the partials to the
 * per node partial list.
 */
static void put_cpu_partial(struct kmem_cache *s, struct page *page, int drain)
{
#ifdef CONFIG_SLUB_CPU_PARTIAL
        struct page *oldpage;
        int pages;
        int pobjects;

        preempt_disable();
        do {
                pages = 0;
                pobjects = 0;
                oldpage = this_cpu_read(s->cpu_slab->partial);

                if (oldpage) {
                        pobjects = oldpage->pobjects;
                        pages = oldpage->pages;
                        if (drain && pobjects > s->cpu_partial) {
                                unsigned long flags;
                                /*
                                 * partial array is full. Move the existing
                                 * set to the per node partial list.
                                 */
                                local_irq_save(flags);
                                unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
                                local_irq_restore(flags);
                                oldpage = NULL;
                                pobjects = 0;
                                pages = 0;
                                stat(s, CPU_PARTIAL_DRAIN);
                        }
                }

                pages++;
                pobjects += page->objects - page->inuse;

                page->pages = pages;
                page->pobjects = pobjects;
                page->next = oldpage;

        } while (this_cpu_cmpxchg(s->cpu_slab->partial, oldpage, page)
                                                                != oldpage);
        if (unlikely(!s->cpu_partial)) {
                unsigned long flags;

                local_irq_save(flags);
                unfreeze_partials(s, this_cpu_ptr(s->cpu_slab));
                local_irq_restore(flags);
        }
        preempt_enable();
#endif  /* CONFIG_SLUB_CPU_PARTIAL */
}

static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c)
{
        stat(s, CPUSLAB_FLUSH);
        deactivate_slab(s, c->page, c->freelist, c);

        c->tid = next_tid(c->tid);
}

/*
 * Flush cpu slab.
 *
 * Called from IPI handler with interrupts disabled.
 */
static inline void __flush_cpu_slab(struct kmem_cache *s, int cpu)
{
        struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);

        if (c->page)
                flush_slab(s, c);

        unfreeze_partials(s, c);
}

static void flush_cpu_slab(void *d)
{
        struct kmem_cache *s = d;

        __flush_cpu_slab(s, smp_processor_id());
}

static bool has_cpu_slab(int cpu, void *info)
{
        struct kmem_cache *s = info;
        struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);

        return c->page || slub_percpu_partial(c);
}

static void flush_all(struct kmem_cache *s)
{
        on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC);
}

/*
 * Use the cpu notifier to insure that the cpu slabs are flushed when
 * necessary.
 */
static int slub_cpu_dead(unsigned int cpu)
{
        struct kmem_cache *s;
        unsigned long flags;

        mutex_lock(&slab_mutex);
        list_for_each_entry(s, &slab_caches, list) {
                local_irq_save(flags);
                __flush_cpu_slab(s, cpu);
                local_irq_restore(flags);
        }
        mutex_unlock(&slab_mutex);
        return 0;
}

/*
 * Check if the objects in a per cpu structure fit numa
 * locality expectations.
 */
static inline int node_match(struct page *page, int node)
{
#ifdef CONFIG_NUMA
        if (node != NUMA_NO_NODE && page_to_nid(page) != node)
                return 0;
#endif
        return 1;
}

#ifdef CONFIG_SLUB_DEBUG
static int count_free(struct page *page)
{
        return page->objects - page->inuse;
}

static inline unsigned long node_nr_objs(struct kmem_cache_node *n)
{
        return atomic_long_read(&n->total_objects);
}
#endif /* CONFIG_SLUB_DEBUG */

#if defined(CONFIG_SLUB_DEBUG) || defined(CONFIG_SYSFS)
static unsigned long count_partial(struct kmem_cache_node *n,
                                        int (*get_count)(struct page *))
{
        unsigned long flags;
        unsigned long x = 0;
        struct page *page;

        spin_lock_irqsave(&n->list_lock, flags);
        list_for_each_entry(page, &n->partial, slab_list)
                x += get_count(page);
        spin_unlock_irqrestore(&n->list_lock, flags);
        return x;
}
#endif /* CONFIG_SLUB_DEBUG || CONFIG_SYSFS */

static noinline void
slab_out_of_memory(struct kmem_cache *s, gfp_t gfpflags, int nid)
{
#ifdef CONFIG_SLUB_DEBUG
        static DEFINE_RATELIMIT_STATE(slub_oom_rs, DEFAULT_RATELIMIT_INTERVAL,
                                      DEFAULT_RATELIMIT_BURST);
        int node;
        struct kmem_cache_node *n;

        if ((gfpflags & __GFP_NOWARN) || !__ratelimit(&slub_oom_rs))
                return;

        pr_warn("SLUB: Unable to allocate memory on node %d, gfp=%#x(%pGg)\n",
                nid, gfpflags, &gfpflags);
        pr_warn("  cache: %s, object size: %u, buffer size: %u, default order: %u, min order: %u\n",
                s->name, s->object_size, s->size, oo_order(s->oo),
                oo_order(s->min));

        if (oo_order(s->min) > get_order(s->object_size))
                pr_warn("  %s debugging increased min order, use slub_debug=O to disable.\n",
                        s->name);

        for_each_kmem_cache_node(s, node, n) {
                unsigned long nr_slabs;
                unsigned long nr_objs;
                unsigned long nr_free;

                nr_free  = count_partial(n, count_free);
                nr_slabs = node_nr_slabs(n);
                nr_objs  = node_nr_objs(n);

                pr_warn("  node %d: slabs: %ld, objs: %ld, free: %ld\n",
                        node, nr_slabs, nr_objs, nr_free);
        }
#endif
}

static inline void *new_slab_objects(struct kmem_cache *s, gfp_t flags,
                        int node, struct kmem_cache_cpu **pc)
{
        void *freelist;
        struct kmem_cache_cpu *c = *pc;
        struct page *page;

        WARN_ON_ONCE(s->ctor && (flags & __GFP_ZERO));

        freelist = get_partial(s, flags, node, c);

        if (freelist)
                return freelist;

        page = new_slab(s, flags, node);
        if (page) {
                c = raw_cpu_ptr(s->cpu_slab);
                if (c->page)
                        flush_slab(s, c);

                /*
                 * No other reference to the page yet so we can
                 * muck around with it freely without cmpxchg
                 */
                freelist = page->freelist;
                page->freelist = NULL;

                stat(s, ALLOC_SLAB);
                c->page = page;
                *pc = c;
        }

        return freelist;
}

static inline bool pfmemalloc_match(struct page *page, gfp_t gfpflags)
{
        if (unlikely(PageSlabPfmemalloc(page)))
                return gfp_pfmemalloc_allowed(gfpflags);

        return true;
}

/*
 * Check the page->freelist of a page and either transfer the freelist to the
 * per cpu freelist or deactivate the page.
 *
 * The page is still frozen if the return value is not NULL.
 *
 * If this function returns NULL then the page has been unfrozen.
 *
 * This function must be called with interrupt disabled.
 */
static inline void *get_freelist(struct kmem_cache *s, struct page *page)
{
        struct page new;
        unsigned long counters;
        void *freelist;

        do {
                freelist = page->freelist;
                counters = page->counters;

                new.counters = counters;
                VM_BUG_ON(!new.frozen);

                new.inuse = page->objects;
                new.frozen = freelist != NULL;

        } while (!__cmpxchg_double_slab(s, page,
                freelist, counters,
                NULL, new.counters,
                "get_freelist"));

        return freelist;
}

/*
 * Slow path. The lockless freelist is empty or we need to perform
 * debugging duties.
 *
 * Processing is still very fast if new objects have been freed to the
 * regular freelist. In that case we simply take over the regular freelist
 * as the lockless freelist and zap the regular freelist.
 *
 * If that is not working then we fall back to the partial lists. We take the
 * first element of the freelist as the object to allocate now and move the
 * rest of the freelist to the lockless freelist.
 *
 * And if we were unable to get a new slab from the partial slab lists then
 * we need to allocate a new slab. This is the slowest path since it involves
 * a call to the page allocator and the setup of a new slab.
 *
 * Version of __slab_alloc to use when we know that interrupts are
 * already disabled (which is the case for bulk allocation).
 */
static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
                          unsigned long addr, struct kmem_cache_cpu *c)
{
        void *freelist;
        struct page *page;

        page = c->page;
        if (!page)
                goto new_slab;
redo:

        if (unlikely(!node_match(page, node))) {
                int searchnode = node;

                if (node != NUMA_NO_NODE && !node_present_pages(node))
                        searchnode = node_to_mem_node(node);

                if (unlikely(!node_match(page, searchnode))) {
                        stat(s, ALLOC_NODE_MISMATCH);
                        deactivate_slab(s, page, c->freelist, c);
                        goto new_slab;
                }
        }

        /*
         * By rights, we should be searching for a slab page that was
         * PFMEMALLOC but right now, we are losing the pfmemalloc
         * information when the page leaves the per-cpu allocator
         */
        if (unlikely(!pfmemalloc_match(page, gfpflags))) {
                deactivate_slab(s, page, c->freelist, c);
                goto new_slab;
        }

        /* must check again c->freelist in case of cpu migration or IRQ */
        freelist = c->freelist;
        if (freelist)
                goto load_freelist;

        freelist = get_freelist(s, page);

        if (!freelist) {
                c->page = NULL;
                stat(s, DEACTIVATE_BYPASS);
                goto new_slab;
        }

        stat(s, ALLOC_REFILL);

load_freelist:
        /*
         * freelist is pointing to the list of objects to be used.
         * page is pointing to the page from which the objects are obtained.
         * That page must be frozen for per cpu allocations to work.
         */
        VM_BUG_ON(!c->page->frozen);
        c->freelist = get_freepointer(s, freelist);
        c->tid = next_tid(c->tid);
        return freelist;

new_slab:

        if (slub_percpu_partial(c)) {
                page = c->page = slub_percpu_partial(c);
                slub_set_percpu_partial(c, page);
                stat(s, CPU_PARTIAL_ALLOC);
                goto redo;
        }

        freelist = new_slab_objects(s, gfpflags, node, &c);

        if (unlikely(!freelist)) {
                slab_out_of_memory(s, gfpflags, node);
                return NULL;
        }

        page = c->page;
        if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags)))
                goto load_freelist;

        /* Only entered in the debug case */
        if (kmem_cache_debug(s) &&
                        !alloc_debug_processing(s, page, freelist, addr))
                goto new_slab;  /* Slab failed checks. Next slab needed */

        deactivate_slab(s, page, get_freepointer(s, freelist), c);
        return freelist;
}

/*
 * Another one that disabled interrupt and compensates for possible
 * cpu changes by refetching the per cpu area pointer.
 */
static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
                          unsigned long addr, struct kmem_cache_cpu *c)
{
        void *p;
        unsigned long flags;

        local_irq_save(flags);
#ifdef CONFIG_PREEMPT
        /*
         * We may have been preempted and rescheduled on a different
         * cpu before disabling interrupts. Need to reload cpu area
         * pointer.
         */
        c = this_cpu_ptr(s->cpu_slab);
#endif

        p = ___slab_alloc(s, gfpflags, node, addr, c);
        local_irq_restore(flags);
        return p;
}

/*
 * Inlined fastpath so that allocation functions (kmalloc, kmem_cache_alloc)
 * have the fastpath folded into their functions. So no function call
 * overhead for requests that can be satisfied on the fastpath.
 *
 * The fastpath works by first checking if the lockless freelist can be used.
 * If not then __slab_alloc is called for slow processing.
 *
 * Otherwise we can simply pick the next object from the lockless free list.
 */
static __always_inline void *slab_alloc_node(struct kmem_cache *s,
                gfp_t gfpflags, int node, unsigned long addr)
{
        void *object;
        struct kmem_cache_cpu *c;
        struct page *page;
        unsigned long tid;

        s = slab_pre_alloc_hook(s, gfpflags);
        if (!s)
                return NULL;
redo:
        /*
         * Must read kmem_cache cpu data via this cpu ptr. Preemption is
         * enabled. We may switch back and forth between cpus while
         * reading from one cpu area. That does not matter as long
         * as we end up on the original cpu again when doing the cmpxchg.
         *
         * We should guarantee that tid and kmem_cache are retrieved on
         * the same cpu. It could be different if CONFIG_PREEMPT so we need
         * to check if it is matched or not.
         */
        do {
                tid = this_cpu_read(s->cpu_slab->tid);
                c = raw_cpu_ptr(s->cpu_slab);
        } while (IS_ENABLED(CONFIG_PREEMPT) &&
                 unlikely(tid != READ_ONCE(c->tid)));

        /*
         * Irqless object alloc/free algorithm used here depends on sequence
         * of fetching cpu_slab's data. tid should be fetched before anything
         * on c to guarantee that object and page associated with previous tid
         * won't be used with current tid. If we fetch tid first, object and
         * page could be one associated with next tid and our alloc/free
         * request will be failed. In this case, we will retry. So, no problem.
         */
        barrier();

        /*
         * The transaction ids are globally unique per cpu and per operation on
         * a per cpu queue. Thus they can be guarantee that the cmpxchg_double
         * occurs on the right processor and that there was no operation on the
         * linked list in between.
         */

        object = c->freelist;
        page = c->page;
        if (unlikely(!object || !node_match(page, node))) {
                object = __slab_alloc(s, gfpflags, node, addr, c);
                stat(s, ALLOC_SLOWPATH);
        } else {
                void *next_object = get_freepointer_safe(s, object);

                /*
                 * The cmpxchg will only match if there was no additional
                 * operation and if we are on the right processor.
                 *
                 * The cmpxchg does the following atomically (without lock
                 * semantics!)
                 * 1. Relocate first pointer to the current per cpu area.
                 * 2. Verify that tid and freelist have not been changed
                 * 3. If they were not changed replace tid and freelist
                 *
                 * Since this is without lock semantics the protection is only
                 * against code executing on this cpu *not* from access by
                 * other cpus.
                 */
                if (unlikely(!this_cpu_cmpxchg_double(
                                s->cpu_slab->freelist, s->cpu_slab->tid,
                                object, tid,
                                next_object, next_tid(tid)))) {

                        note_cmpxchg_failure("slab_alloc", s, tid);
                        goto redo;
                }
                prefetch_freepointer(s, next_object);
                stat(s, ALLOC_FASTPATH);
        }
        /*
         * If the object has been wiped upon free, make sure it's fully
         * initialized by zeroing out freelist pointer.
         */
        if (unlikely(slab_want_init_on_free(s)) && object)
                memset(object + s->offset, 0, sizeof(void *));

        if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object)
                memset(object, 0, s->object_size);

        slab_post_alloc_hook(s, gfpflags, 1, &object);

        return object;
}

static __always_inline void *slab_alloc(struct kmem_cache *s,
                gfp_t gfpflags, unsigned long addr)
{
        return slab_alloc_node(s, gfpflags, NUMA_NO_NODE, addr);
}

void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags)
{
        void *ret = slab_alloc(s, gfpflags, _RET_IP_);

        trace_kmem_cache_alloc(_RET_IP_, ret, s->object_size,
                                s->size, gfpflags);

        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc);

#ifdef CONFIG_TRACING
void *kmem_cache_alloc_trace(struct kmem_cache *s, gfp_t gfpflags, size_t size)
{
        void *ret = slab_alloc(s, gfpflags, _RET_IP_);
        trace_kmalloc(_RET_IP_, ret, size, s->size, gfpflags);
        ret = kasan_kmalloc(s, ret, size, gfpflags);
        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_trace);
#endif

#ifdef CONFIG_NUMA
void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t gfpflags, int node)
{
        void *ret = slab_alloc_node(s, gfpflags, node, _RET_IP_);

        trace_kmem_cache_alloc_node(_RET_IP_, ret,
                                    s->object_size, s->size, gfpflags, node);

        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node);

#ifdef CONFIG_TRACING
void *kmem_cache_alloc_node_trace(struct kmem_cache *s,
                                    gfp_t gfpflags,
                                    int node, size_t size)
{
        void *ret = slab_alloc_node(s, gfpflags, node, _RET_IP_);

        trace_kmalloc_node(_RET_IP_, ret,
                           size, s->size, gfpflags, node);

        ret = kasan_kmalloc(s, ret, size, gfpflags);
        return ret;
}
EXPORT_SYMBOL(kmem_cache_alloc_node_trace);
#endif
#endif  /* CONFIG_NUMA */

/*
 * Slow path handling. This may still be called frequently since objects
 * have a longer lifetime than the cpu slabs in most processing loads.
 *
 * So we still attempt to reduce cache line usage. Just take the slab
 * lock and free the item. If there is no additional partial page
 * handling required then we can return immediately.
 */
static void __slab_free(struct kmem_cache *s, struct page *page,
                        void *head, void *tail, int cnt,
                        unsigned long addr)

{
        void *prior;
        int was_frozen;
        struct page new;
        unsigned long counters;
        struct kmem_cache_node *n = NULL;
        unsigned long uninitialized_var(flags);

        stat(s, FREE_SLOWPATH);

        if (kmem_cache_debug(s) &&
            !free_debug_processing(s, page, head, tail, cnt, addr))
                return;

        do {
                if (unlikely(n)) {
                        spin_unlock_irqrestore(&n->list_lock, flags);
                        n = NULL;
                }
                prior = page->freelist;
                counters = page->counters;
                set_freepointer(s, tail, prior);
                new.counters = counters;
                was_frozen = new.frozen;
                new.inuse -= cnt;
                if ((!new.inuse || !prior) && !was_frozen) {

                        if (kmem_cache_has_cpu_partial(s) && !prior) {

                                /*
                                 * Slab was on no list before and will be
                                 * partially empty
                                 * We can defer the list move and instead
                                 * freeze it.
                                 */
                                new.frozen = 1;

                        } else { /* Needs to be taken off a list */

                                n = get_node(s, page_to_nid(page));
                                /*
                                 * Speculatively acquire the list_lock.
                                 * If the cmpxchg does not succeed then we may
                                 * drop the list_lock without any processing.
                                 *
                                 * Otherwise the list_lock will synchronize with
                                 * other processors updating the list of slabs.
                                 */
                                spin_lock_irqsave(&n->list_lock, flags);

                        }
                }

        } while (!cmpxchg_double_slab(s, page,
                prior, counters,
                head, new.counters,
                "__slab_free"));

        if (likely(!n)) {

                /*
                 * If we just froze the page then put it onto the
                 * per cpu partial list.
                 */
                if (new.frozen && !was_frozen) {
                        put_cpu_partial(s, page, 1);
                        stat(s, CPU_PARTIAL_FREE);
                }
                /*
                 * The list lock was not taken therefore no list
                 * activity can be necessary.
                 */
                if (was_frozen)
                        stat(s, FREE_FROZEN);
                return;
        }

        if (unlikely(!new.inuse && n->nr_partial >= s->min_partial))
                goto slab_empty;

        /*
         * Objects left in the slab. If it was not on the partial list before
         * then add it.
         */
        if (!kmem_cache_has_cpu_partial(s) && unlikely(!prior)) {
                remove_full(s, n, page);
                add_partial(n, page, DEACTIVATE_TO_TAIL);
                stat(s, FREE_ADD_PARTIAL);
        }
        spin_unlock_irqrestore(&n->list_lock, flags);
        return;

slab_empty:
        if (prior) {
                /*
                 * Slab on the partial list.
                 */
                remove_partial(n, page);
                stat(s, FREE_REMOVE_PARTIAL);
        } else {
                /* Slab must be on the full list */
                remove_full(s, n, page);
        }

        spin_unlock_irqrestore(&n->list_lock, flags);
        stat(s, FREE_SLAB);
        discard_slab(s, page);
}

/*
 * Fastpath with forced inlining to produce a kfree and kmem_cache_free that
 * can perform fastpath freeing without additional function calls.
 *
 * The fastpath is only possible if we are freeing to the current cpu slab
 * of this processor. This typically the case if we have just allocated
 * the item before.
 *
 * If fastpath is not possible then fall back to __slab_free where we deal
 * with all sorts of special processing.
 *
 * Bulk free of a freelist with several objects (all pointing to the
 * same page) possible by specifying head and tail ptr, plus objects
 * count (cnt). Bulk free indicated by tail pointer being set.
 */
static __always_inline void do_slab_free(struct kmem_cache *s,
                                struct page *page, void *head, void *tail,
                                int cnt, unsigned long addr)
{
        void *tail_obj = tail ? : head;
        struct kmem_cache_cpu *c;
        unsigned long tid;
redo:
        /*
         * Determine the currently cpus per cpu slab.
         * The cpu may change afterward. However that does not matter since
         * data is retrieved via this pointer. If we are on the same cpu
         * during the cmpxchg then the free will succeed.
         */
        do {
                tid = this_cpu_read(s->cpu_slab->tid);
                c = raw_cpu_ptr(s->cpu_slab);
        } while (IS_ENABLED(CONFIG_PREEMPT) &&
                 unlikely(tid != READ_ONCE(c->tid)));

        /* Same with comment on barrier() in slab_alloc_node() */
        barrier();

        if (likely(page == c->page)) {
                set_freepointer(s, tail_obj, c->freelist);

                if (unlikely(!this_cpu_cmpxchg_double(
                                s->cpu_slab->freelist, s->cpu_slab->tid,
                                c->freelist, tid,
                                head, next_tid(tid)))) {

                        note_cmpxchg_failure("slab_free", s, tid);
                        goto redo;