/*
 * zcache.c
 *
 * Copyright (c) 2010-2012, Dan Magenheimer, Oracle Corp.
 * Copyright (c) 2010,2011, Nitin Gupta
 *
 * Zcache provides an in-kernel "host implementation" for transcendent memory
 * ("tmem") and, thus indirectly, for cleancache and frontswap.  Zcache uses
 * lzo1x compression to improve density and an embedded allocator called
 * "zbud" which "buddies" two compressed pages semi-optimally in each physical
 * pageframe.  Zbud is integrally tied into tmem to allow pageframes to
 * be "reclaimed" efficiently.
 */

#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/atomic.h>
#include <linux/math64.h>
#include <linux/crypto.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>

#include <linux/cleancache.h>
#include <linux/frontswap.h>
#include "tmem.h"
#include "zcache.h"
#include "zbud.h"
#include "ramster.h"
#include "debug.h"
#ifdef CONFIG_RAMSTER
static bool ramster_enabled __read_mostly;
static int disable_frontswap_selfshrink;
#else
#define ramster_enabled false
#define disable_frontswap_selfshrink 0
#endif

#ifndef __PG_WAS_ACTIVE
static inline bool PageWasActive(struct page *page)
{
        return true;
}

static inline void SetPageWasActive(struct page *page)
{
}
#endif

#ifdef FRONTSWAP_HAS_EXCLUSIVE_GETS
static bool frontswap_has_exclusive_gets __read_mostly = true;
#else
static bool frontswap_has_exclusive_gets __read_mostly;
static inline void frontswap_tmem_exclusive_gets(bool b)
{
}
#endif

/*
 * mark pampd to special value in order that later
 * retrieve will identify zero-filled pages
 */
#define ZERO_FILLED 0x2

/* enable (or fix code) when Seth's patches are accepted upstream */
#define zcache_writeback_enabled 0

static bool zcache_enabled __read_mostly;
static bool disable_cleancache __read_mostly;
static bool disable_frontswap __read_mostly;
static bool disable_frontswap_ignore_nonactive __read_mostly;
static bool disable_cleancache_ignore_nonactive __read_mostly;
static char *namestr __read_mostly = "zcache";

#define ZCACHE_GFP_MASK \
        (__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC)

/* crypto API for zcache  */
#ifdef CONFIG_ZCACHE_MODULE
static char *zcache_comp_name = "lzo";
#else
#define ZCACHE_COMP_NAME_SZ CRYPTO_MAX_ALG_NAME
static char zcache_comp_name[ZCACHE_COMP_NAME_SZ] __read_mostly;
#endif
static struct crypto_comp * __percpu *zcache_comp_pcpu_tfms __read_mostly;

enum comp_op {
        ZCACHE_COMPOP_COMPRESS,
        ZCACHE_COMPOP_DECOMPRESS
};

static inline int zcache_comp_op(enum comp_op op,
                                const u8 *src, unsigned int slen,
                                u8 *dst, unsigned int *dlen)
{
        struct crypto_comp *tfm;
        int ret = -1;

        BUG_ON(!zcache_comp_pcpu_tfms);
        tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, get_cpu());
        BUG_ON(!tfm);
        switch (op) {
        case ZCACHE_COMPOP_COMPRESS:
                ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
                break;
        case ZCACHE_COMPOP_DECOMPRESS:
                ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
                break;
        default:
                ret = -EINVAL;
        }
        put_cpu();
        return ret;
}

/*
 * policy parameters
 */

/*
 * byte count defining poor compression; pages with greater zsize will be
 * rejected
 */
static unsigned int zbud_max_zsize __read_mostly = (PAGE_SIZE / 8) * 7;
/*
 * byte count defining poor *mean* compression; pages with greater zsize
 * will be rejected until sufficient better-compressed pages are accepted
 * driving the mean below this threshold
 */
static unsigned int zbud_max_mean_zsize __read_mostly = (PAGE_SIZE / 8) * 5;

/*
 * for now, used named slabs so can easily track usage; later can
 * either just use kmalloc, or perhaps add a slab-like allocator
 * to more carefully manage total memory utilization
 */
static struct kmem_cache *zcache_objnode_cache;
static struct kmem_cache *zcache_obj_cache;

static DEFINE_PER_CPU(struct zcache_preload, zcache_preloads) = { 0, };

/* Used by debug.c */
ssize_t zcache_pers_zpages;
u64 zcache_pers_zbytes;
ssize_t zcache_eph_pageframes;
ssize_t zcache_pers_pageframes;

/* Used by this code. */
ssize_t zcache_last_active_file_pageframes;
ssize_t zcache_last_inactive_file_pageframes;
ssize_t zcache_last_active_anon_pageframes;
ssize_t zcache_last_inactive_anon_pageframes;
#ifdef CONFIG_ZCACHE_WRITEBACK
ssize_t zcache_writtenback_pages;
ssize_t zcache_outstanding_writeback_pages;
#endif
/*
 * zcache core code starts here
 */

static struct zcache_client zcache_host;
static struct zcache_client zcache_clients[MAX_CLIENTS];

static inline bool is_local_client(struct zcache_client *cli)
{
        return cli == &zcache_host;
}

static struct zcache_client *zcache_get_client_by_id(uint16_t cli_id)
{
        struct zcache_client *cli = &zcache_host;

        if (cli_id != LOCAL_CLIENT) {
                if (cli_id >= MAX_CLIENTS)
                        goto out;
                cli = &zcache_clients[cli_id];
        }
out:
        return cli;
}

/*
 * Tmem operations assume the poolid implies the invoking client.
 * Zcache only has one client (the kernel itself): LOCAL_CLIENT.
 * RAMster has each client numbered by cluster node, and a KVM version
 * of zcache would have one client per guest and each client might
 * have a poolid==N.
 */
struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id, uint16_t poolid)
{
        struct tmem_pool *pool = NULL;
        struct zcache_client *cli = NULL;

        cli = zcache_get_client_by_id(cli_id);
        if (cli == NULL)
                goto out;
        if (!is_local_client(cli))
                atomic_inc(&cli->refcount);
        if (poolid < MAX_POOLS_PER_CLIENT) {
                pool = cli->tmem_pools[poolid];
                if (pool != NULL)
                        atomic_inc(&pool->refcount);
        }
out:
        return pool;
}

void zcache_put_pool(struct tmem_pool *pool)
{
        struct zcache_client *cli = NULL;

        if (pool == NULL)
                BUG();
        cli = pool->client;
        atomic_dec(&pool->refcount);
        if (!is_local_client(cli))
                atomic_dec(&cli->refcount);
}

int zcache_new_client(uint16_t cli_id)
{
        struct zcache_client *cli;
        int ret = -1;

        cli = zcache_get_client_by_id(cli_id);
        if (cli == NULL)
                goto out;
        if (cli->allocated)
                goto out;
        cli->allocated = 1;
        ret = 0;
out:
        return ret;
}

/*
 * zcache implementation for tmem host ops
 */

static struct tmem_objnode *zcache_objnode_alloc(struct tmem_pool *pool)
{
        struct tmem_objnode *objnode = NULL;
        struct zcache_preload *kp;
        int i;

        kp = &__get_cpu_var(zcache_preloads);
        for (i = 0; i < ARRAY_SIZE(kp->objnodes); i++) {
                objnode = kp->objnodes[i];
                if (objnode != NULL) {
                        kp->objnodes[i] = NULL;
                        break;
                }
        }
        BUG_ON(objnode == NULL);
        inc_zcache_objnode_count();
        return objnode;
}

static void zcache_objnode_free(struct tmem_objnode *objnode,
                                        struct tmem_pool *pool)
{
        dec_zcache_objnode_count();
        kmem_cache_free(zcache_objnode_cache, objnode);
}

static struct tmem_obj *zcache_obj_alloc(struct tmem_pool *pool)
{
        struct tmem_obj *obj = NULL;
        struct zcache_preload *kp;

        kp = &__get_cpu_var(zcache_preloads);
        obj = kp->obj;
        BUG_ON(obj == NULL);
        kp->obj = NULL;
        inc_zcache_obj_count();
        return obj;
}

static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
{
        dec_zcache_obj_count();
        kmem_cache_free(zcache_obj_cache, obj);
}

/*
 * Compressing zero-filled pages will waste memory and introduce
 * serious fragmentation, skip it to avoid overhead.
 */
static bool page_is_zero_filled(struct page *p)
{
        unsigned int pos;
        char *page;

        page = kmap_atomic(p);
        for (pos = 0; pos < PAGE_SIZE / sizeof(*page); pos++) {
                if (page[pos]) {
                        kunmap_atomic(page);
                        return false;
                }
        }
        kunmap_atomic(page);

        return true;
}

static void handle_zero_filled_page(void *p)
{
        void *user_mem;
        struct page *page = (struct page *)p;

        user_mem = kmap_atomic(page);
        memset(user_mem, 0, PAGE_SIZE);
        kunmap_atomic(user_mem);

        flush_dcache_page(page);
}

static struct tmem_hostops zcache_hostops = {
        .obj_alloc = zcache_obj_alloc,
        .obj_free = zcache_obj_free,
        .objnode_alloc = zcache_objnode_alloc,
        .objnode_free = zcache_objnode_free,
};

static struct page *zcache_alloc_page(void)
{
        struct page *page = alloc_page(ZCACHE_GFP_MASK);

        if (page != NULL)
                inc_zcache_pageframes_alloced();
        return page;
}

static void zcache_free_page(struct page *page)
{
        long curr_pageframes;
        static long max_pageframes, min_pageframes;

        if (page == NULL)
                BUG();
        __free_page(page);
        inc_zcache_pageframes_freed();
        curr_pageframes = curr_pageframes_count();
        if (curr_pageframes > max_pageframes)
                max_pageframes = curr_pageframes;
        if (curr_pageframes < min_pageframes)
                min_pageframes = curr_pageframes;
#ifdef CONFIG_ZCACHE_DEBUG
        if (curr_pageframes > 2L || curr_pageframes < -2L) {
                /* pr_info here */
        }
#endif
}

/*
 * zcache implementations for PAM page descriptor ops
 */

/* forward reference */
static void zcache_compress(struct page *from,
                                void **out_va, unsigned *out_len);

static struct page *zcache_evict_eph_pageframe(void);

static void *zcache_pampd_eph_create(char *data, size_t size, bool raw,
                                        struct tmem_handle *th)
{
        void *pampd = NULL, *cdata = data;
        unsigned clen = size;
        bool zero_filled = false;
        struct page *page = (struct page *)(data), *newpage;

        if (page_is_zero_filled(page)) {
                clen = 0;
                zero_filled = true;
                inc_zcache_zero_filled_pages();
                goto got_pampd;
        }

        if (!raw) {
                zcache_compress(page, &cdata, &clen);
                if (clen > zbud_max_buddy_size()) {
                        inc_zcache_compress_poor();
                        goto out;
                }
        } else {
                BUG_ON(clen > zbud_max_buddy_size());
        }

        /* look for space via an existing match first */
        pampd = (void *)zbud_match_prep(th, true, cdata, clen);
        if (pampd != NULL)
                goto got_pampd;

        /* no match, now we need to find (or free up) a full page */
        newpage = zcache_alloc_page();
        if (newpage != NULL)
                goto create_in_new_page;

        inc_zcache_failed_getfreepages();
        /* can't allocate a page, evict an ephemeral page via LRU */
        newpage = zcache_evict_eph_pageframe();
        if (newpage == NULL) {
                inc_zcache_eph_ate_tail_failed();
                goto out;
        }
        inc_zcache_eph_ate_tail();

create_in_new_page:
        pampd = (void *)zbud_create_prep(th, true, cdata, clen, newpage);
        BUG_ON(pampd == NULL);
        inc_zcache_eph_pageframes();

got_pampd:
        inc_zcache_eph_zbytes(clen);
        inc_zcache_eph_zpages();
        if (ramster_enabled && raw && !zero_filled)
                ramster_count_foreign_pages(true, 1);
        if (zero_filled)
                pampd = (void *)ZERO_FILLED;
out:
        return pampd;
}

static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
                                        struct tmem_handle *th)
{
        void *pampd = NULL, *cdata = data;
        unsigned clen = size;
        bool zero_filled = false;
        struct page *page = (struct page *)(data), *newpage;
        unsigned long zbud_mean_zsize;
        unsigned long curr_pers_zpages, total_zsize;

        if (data == NULL) {
                BUG_ON(!ramster_enabled);
                goto create_pampd;
        }

        if (page_is_zero_filled(page)) {
                clen = 0;
                zero_filled = true;
                inc_zcache_zero_filled_pages();
                goto got_pampd;
        }

        curr_pers_zpages = zcache_pers_zpages;
/* FIXME CONFIG_RAMSTER... subtract atomic remote_pers_pages here? */
        if (!raw)
                zcache_compress(page, &cdata, &clen);
        /* reject if compression is too poor */
        if (clen > zbud_max_zsize) {
                inc_zcache_compress_poor();
                goto out;
        }
        /* reject if mean compression is too poor */
        if ((clen > zbud_max_mean_zsize) && (curr_pers_zpages > 0)) {
                total_zsize = zcache_pers_zbytes;
                if ((long)total_zsize < 0)
                        total_zsize = 0;
                zbud_mean_zsize = div_u64(total_zsize,
                                        curr_pers_zpages);
                if (zbud_mean_zsize > zbud_max_mean_zsize) {
                        inc_zcache_mean_compress_poor();
                        goto out;
                }
        }

create_pampd:
        /* look for space via an existing match first */
        pampd = (void *)zbud_match_prep(th, false, cdata, clen);
        if (pampd != NULL)
                goto got_pampd;

        /* no match, now we need to find (or free up) a full page */
        newpage = zcache_alloc_page();
        if (newpage != NULL)
                goto create_in_new_page;
        /*
         * FIXME do the following only if eph is oversized?
         * if (zcache_eph_pageframes >
         * (global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE) +
         * global_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE)))
         */
        inc_zcache_failed_getfreepages();
        /* can't allocate a page, evict an ephemeral page via LRU */
        newpage = zcache_evict_eph_pageframe();
        if (newpage == NULL) {
                inc_zcache_pers_ate_eph_failed();
                goto out;
        }
        inc_zcache_pers_ate_eph();

create_in_new_page:
        pampd = (void *)zbud_create_prep(th, false, cdata, clen, newpage);
        BUG_ON(pampd == NULL);
        inc_zcache_pers_pageframes();

got_pampd:
        inc_zcache_pers_zpages();
        inc_zcache_pers_zbytes(clen);
        if (ramster_enabled && raw && !zero_filled)
                ramster_count_foreign_pages(false, 1);
        if (zero_filled)
                pampd = (void *)ZERO_FILLED;
out:
        return pampd;
}

/*
 * This is called directly from zcache_put_page to pre-allocate space
 * to store a zpage.
 */
void *zcache_pampd_create(char *data, unsigned int size, bool raw,
                                        int eph, struct tmem_handle *th)
{
        void *pampd = NULL;
        struct zcache_preload *kp;
        struct tmem_objnode *objnode;
        struct tmem_obj *obj;
        int i;

        BUG_ON(!irqs_disabled());
        /* pre-allocate per-cpu metadata */
        BUG_ON(zcache_objnode_cache == NULL);
        BUG_ON(zcache_obj_cache == NULL);
        kp = &__get_cpu_var(zcache_preloads);
        for (i = 0; i < ARRAY_SIZE(kp->objnodes); i++) {
                objnode = kp->objnodes[i];
                if (objnode == NULL) {
                        objnode = kmem_cache_alloc(zcache_objnode_cache,
                                                        ZCACHE_GFP_MASK);
                        if (unlikely(objnode == NULL)) {
                                inc_zcache_failed_alloc();
                                goto out;
                        }
                        kp->objnodes[i] = objnode;
                }
        }
        if (kp->obj == NULL) {
                obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK);
                kp->obj = obj;
        }
        if (unlikely(kp->obj == NULL)) {
                inc_zcache_failed_alloc();
                goto out;
        }
        /*
         * ok, have all the metadata pre-allocated, now do the data
         * but since how we allocate the data is dependent on ephemeral
         * or persistent, we split the call here to different sub-functions
         */
        if (eph)
                pampd = zcache_pampd_eph_create(data, size, raw, th);
        else
                pampd = zcache_pampd_pers_create(data, size, raw, th);
out:
        return pampd;
}

/*
 * This is a pamops called via tmem_put and is necessary to "finish"
 * a pampd creation.
 */
void zcache_pampd_create_finish(void *pampd, bool eph)
{
        if (pampd != (void *)ZERO_FILLED)
                zbud_create_finish((struct zbudref *)pampd, eph);
}

/*
 * This is passed as a function parameter to zbud_decompress so that
 * zbud need not be familiar with the details of crypto. It assumes that
 * the bytes from_va and to_va through from_va+size-1 and to_va+size-1 are
 * kmapped.  It must be successful, else there is a logic bug somewhere.
 */
static void zcache_decompress(char *from_va, unsigned int size, char *to_va)
{
        int ret;
        unsigned int outlen = PAGE_SIZE;

        ret = zcache_comp_op(ZCACHE_COMPOP_DECOMPRESS, from_va, size,
                                to_va, &outlen);
        BUG_ON(ret);
        BUG_ON(outlen != PAGE_SIZE);
}

/*
 * Decompress from the kernel va to a pageframe
 */
void zcache_decompress_to_page(char *from_va, unsigned int size,
                                        struct page *to_page)
{
        char *to_va = kmap_atomic(to_page);
        zcache_decompress(from_va, size, to_va);
        kunmap_atomic(to_va);
}

/*
 * fill the pageframe corresponding to the struct page with the data
 * from the passed pampd
 */
static int zcache_pampd_get_data(char *data, size_t *sizep, bool raw,
                                        void *pampd, struct tmem_pool *pool,
                                        struct tmem_oid *oid, uint32_t index)
{
        int ret;
        bool eph = !is_persistent(pool);

        BUG_ON(preemptible());
        BUG_ON(eph);    /* fix later if shared pools get implemented */
        BUG_ON(pampd_is_remote(pampd));

        if (pampd == (void *)ZERO_FILLED) {
                handle_zero_filled_page(data);
                if (!raw)
                        *sizep = PAGE_SIZE;
                return 0;
        }

        if (raw)
                ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
                                                sizep, eph);
        else {
                ret = zbud_decompress((struct page *)(data),
                                        (struct zbudref *)pampd, false,
                                        zcache_decompress);
                *sizep = PAGE_SIZE;
        }
        return ret;
}

/*
 * fill the pageframe corresponding to the struct page with the data
 * from the passed pampd
 */
static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
                                        void *pampd, struct tmem_pool *pool,
                                        struct tmem_oid *oid, uint32_t index)
{
        int ret = 0;
        bool eph = !is_persistent(pool), zero_filled = false;
        struct page *page = NULL;
        unsigned int zsize, zpages;

        BUG_ON(preemptible());
        BUG_ON(pampd_is_remote(pampd));

        if (pampd == (void *)ZERO_FILLED) {
                handle_zero_filled_page(data);
                zero_filled = true;
                zsize = 0;
                zpages = 1;
                if (!raw)
                        *sizep = PAGE_SIZE;
                dec_zcache_zero_filled_pages();
                goto zero_fill;
        }

        if (raw)
                ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
                                                sizep, eph);
        else {
                ret = zbud_decompress((struct page *)(data),
                                        (struct zbudref *)pampd, eph,
                                        zcache_decompress);
                *sizep = PAGE_SIZE;
        }
        page = zbud_free_and_delist((struct zbudref *)pampd, eph,
                                        &zsize, &zpages);
zero_fill:
        if (eph) {
                if (page)
                        dec_zcache_eph_pageframes();
                dec_zcache_eph_zpages(zpages);
                dec_zcache_eph_zbytes(zsize);
        } else {
                if (page)
                        dec_zcache_pers_pageframes();
                dec_zcache_pers_zpages(zpages);
                dec_zcache_pers_zbytes(zsize);
        }
        if (!is_local_client(pool->client) && !zero_filled)
                ramster_count_foreign_pages(eph, -1);
        if (page && !zero_filled)
                zcache_free_page(page);
        return ret;
}

/*
 * free the pampd and remove it from any zcache lists
 * pampd must no longer be pointed to from any tmem data structures!
 */
static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
                              struct tmem_oid *oid, uint32_t index, bool acct)
{
        struct page *page = NULL;
        unsigned int zsize, zpages;
        bool zero_filled = false;

        BUG_ON(preemptible());

        if (pampd == (void *)ZERO_FILLED) {
                zero_filled = true;
                zsize = 0;
                zpages = 1;
                dec_zcache_zero_filled_pages();
        }

        if (pampd_is_remote(pampd) && !zero_filled) {
                BUG_ON(!ramster_enabled);
                pampd = ramster_pampd_free(pampd, pool, oid, index, acct);
                if (pampd == NULL)
                        return;
        }
        if (is_ephemeral(pool)) {
                if (!zero_filled)
                        page = zbud_free_and_delist((struct zbudref *)pampd,
                                                true, &zsize, &zpages);
                if (page)
                        dec_zcache_eph_pageframes();
                dec_zcache_eph_zpages(zpages);
                dec_zcache_eph_zbytes(zsize);
                /* FIXME CONFIG_RAMSTER... check acct parameter? */
        } else {
                if (!zero_filled)
                        page = zbud_free_and_delist((struct zbudref *)pampd,
                                                false, &zsize, &zpages);
                if (page)
                        dec_zcache_pers_pageframes();
                dec_zcache_pers_zpages(zpages);
                dec_zcache_pers_zbytes(zsize);
        }
        if (!is_local_client(pool->client) && !zero_filled)
                ramster_count_foreign_pages(is_ephemeral(pool), -1);
        if (page && !zero_filled)
                zcache_free_page(page);
}

static struct tmem_pamops zcache_pamops = {
        .create_finish = zcache_pampd_create_finish,
        .get_data = zcache_pampd_get_data,
        .get_data_and_free = zcache_pampd_get_data_and_free,
        .free = zcache_pampd_free,
};

/*
 * zcache compression/decompression and related per-cpu stuff
 */

static DEFINE_PER_CPU(unsigned char *, zcache_dstmem);
#define ZCACHE_DSTMEM_ORDER 1

static void zcache_compress(struct page *from, void **out_va, unsigned *out_len)
{
        int ret;
        unsigned char *dmem = __get_cpu_var(zcache_dstmem);
        char *from_va;

        BUG_ON(!irqs_disabled());
        /* no buffer or no compressor so can't compress */
        BUG_ON(dmem == NULL);
        *out_len = PAGE_SIZE << ZCACHE_DSTMEM_ORDER;
        from_va = kmap_atomic(from);
        mb();
        ret = zcache_comp_op(ZCACHE_COMPOP_COMPRESS, from_va, PAGE_SIZE, dmem,
                                out_len);
        BUG_ON(ret);
        *out_va = dmem;
        kunmap_atomic(from_va);
}

static int zcache_comp_cpu_up(int cpu)
{
        struct crypto_comp *tfm;

        tfm = crypto_alloc_comp(zcache_comp_name, 0, 0);
        if (IS_ERR(tfm))
                return NOTIFY_BAD;
        *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = tfm;
        return NOTIFY_OK;
}

static void zcache_comp_cpu_down(int cpu)
{
        struct crypto_comp *tfm;

        tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu);
        crypto_free_comp(tfm);
        *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = NULL;
}

static int zcache_cpu_notifier(struct notifier_block *nb,
                                unsigned long action, void *pcpu)
{
        int ret, i, cpu = (long)pcpu;
        struct zcache_preload *kp;

        switch (action) {
        case CPU_UP_PREPARE:
                ret = zcache_comp_cpu_up(cpu);
                if (ret != NOTIFY_OK) {
                        pr_err("%s: can't allocate compressor xform\n",
                                namestr);
                        return ret;
                }
                per_cpu(zcache_dstmem, cpu) = (void *)__get_free_pages(
                        GFP_KERNEL | __GFP_REPEAT, ZCACHE_DSTMEM_ORDER);
                if (ramster_enabled)
                        ramster_cpu_up(cpu);
                break;
        case CPU_DEAD:
        case CPU_UP_CANCELED:
                zcache_comp_cpu_down(cpu);
                free_pages((unsigned long)per_cpu(zcache_dstmem, cpu),
                        ZCACHE_DSTMEM_ORDER);
                per_cpu(zcache_dstmem, cpu) = NULL;
                kp = &per_cpu(zcache_preloads, cpu);
                for (i = 0; i < ARRAY_SIZE(kp->objnodes); i++) {
                        if (kp->objnodes[i])
                                kmem_cache_free(zcache_objnode_cache,
                                                kp->objnodes[i]);
                }
                if (kp->obj) {
                        kmem_cache_free(zcache_obj_cache, kp->obj);
                        kp->obj = NULL;
                }
                if (ramster_enabled)
                        ramster_cpu_down(cpu);
                break;
        default:
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block zcache_cpu_notifier_block = {
        .notifier_call = zcache_cpu_notifier
};

/*
 * The following code interacts with the zbud eviction and zbud
 * zombify code to access LRU pages
 */

static struct page *zcache_evict_eph_pageframe(void)
{
        struct page *page;
        unsigned int zsize = 0, zpages = 0;

        page = zbud_evict_pageframe_lru(&zsize, &zpages);
        if (page == NULL)
                goto out;
        dec_zcache_eph_zbytes(zsize);
        dec_zcache_eph_zpages(zpages);
        inc_zcache_evicted_eph_zpages(zpages);
        dec_zcache_eph_pageframes();
        inc_zcache_evicted_eph_pageframes();
out:
        return page;
}

#ifdef CONFIG_ZCACHE_WRITEBACK

static atomic_t zcache_outstanding_writeback_pages_atomic = ATOMIC_INIT(0);

static inline void inc_zcache_outstanding_writeback_pages(void)
{
        zcache_outstanding_writeback_pages =
            atomic_inc_return(&zcache_outstanding_writeback_pages_atomic);
}
static inline void dec_zcache_outstanding_writeback_pages(void)
{
        zcache_outstanding_writeback_pages =
          atomic_dec_return(&zcache_outstanding_writeback_pages_atomic);
};
static void unswiz(struct tmem_oid oid, u32 index,
                                unsigned *type, pgoff_t *offset);

/*
 *  Choose an LRU persistent pageframe and attempt to write it back to
 *  the backing swap disk by calling frontswap_writeback on both zpages.
 *
 *  This is work-in-progress.
 */

static void zcache_end_swap_write(struct bio *bio, int err)
{
        end_swap_bio_write(bio, err);
        dec_zcache_outstanding_writeback_pages();
        zcache_writtenback_pages++;
}

/*
 * zcache_get_swap_cache_page
 *
 * This is an adaption of read_swap_cache_async()
 *
 * If success, page is returned in retpage
 * Returns 0 if page was already in the swap cache, page is not locked
 * Returns 1 if the new page needs to be populated, page is locked
 */
static int zcache_get_swap_cache_page(int type, pgoff_t offset,
                                struct page *new_page)
{
        struct page *found_page;
        swp_entry_t entry = swp_entry(type, offset);
        int err;

        BUG_ON(new_page == NULL);
        do {
                /*
                 * First check the swap cache.  Since this is normally
                 * called after lookup_swap_cache() failed, re-calling
                 * that would confuse statistics.
                 */
                found_page = find_get_page(&swapper_space, entry.val);
                if (found_page)
                        return 0;

                /*
                 * call radix_tree_preload() while we can wait.
                 */
                err = radix_tree_preload(GFP_KERNEL);
                if (err)
                        break;

                /*
                 * Swap entry may have been freed since our caller observed it.
                 */
                err = swapcache_prepare(entry);
                if (err == -EEXIST) { /* seems racy */
                        radix_tree_preload_end();
                        continue;
                }
                if (err) { /* swp entry is obsolete ? */
                        radix_tree_preload_end();
                        break;
                }

                /* May fail (-ENOMEM) if radix-tree node allocation failed. */
                __set_page_locked(new_page);
                SetPageSwapBacked(new_page);
                err = __add_to_swap_cache(new_page, entry);
                if (likely(!err)) {
                        radix_tree_preload_end();
                        lru_cache_add_anon(new_page);
                        return 1;
                }
                radix_tree_preload_end();
                ClearPageSwapBacked(new_page);
                __clear_page_locked(new_page);
                /*
                 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
                 * clear SWAP_HAS_CACHE flag.
                 */
                swapcache_free(entry, NULL);
                /* FIXME: is it possible to get here without err==-ENOMEM?
                 * If not, we can dispense with the do loop, use goto retry */
        } while (err != -ENOMEM);

        return -ENOMEM;
}

/*
 * Given a frontswap zpage in zcache (identified by type/offset) and
 * an empty page, put the page into the swap cache, use frontswap
 * to get the page from zcache into the empty page, then give it
 * to the swap subsystem to send to disk (carefully avoiding the
 * possibility that frontswap might snatch it back).
 * Returns < 0 if error, 0 if successful, and 1 if successful but
 * the newpage passed in not needed and should be freed.
 */
static int zcache_frontswap_writeback_zpage(int type, pgoff_t offset,
                                        struct page *newpage)
{
        struct page *page = newpage;
        int ret;
        struct writeback_control wbc = {
                .sync_mode = WB_SYNC_NONE,
        };

        ret = zcache_get_swap_cache_page(type, offset, page);
        if (ret < 0)
                return ret;
        else if (ret == 0) {
                /* more uptodate page is already in swapcache */
                __frontswap_invalidate_page(type, offset);
                return 1;
        }

        BUG_ON(!frontswap_has_exclusive_gets); /* load must also invalidate */
        /* FIXME: how is it possible to get here when page is unlocked? */

        __frontswap_load(page);
        SetPageUptodate(page);  /* above does SetPageDirty, is that enough? */

        /* start writeback */
        SetPageReclaim(page);
        /*
         * Return value is ignored here because it doesn't change anything
         * for us.  Page is returned unlocked.
         */
        (void)__swap_writepage(page, &wbc, zcache_end_swap_write);
        page_cache_release(page);
        inc_zcache_outstanding_writeback_pages();

        return 0;
}

/*
 * The following is still a magic number... we want to allow forward progress
 * for writeback because it clears out needed RAM when under pressure, but
 * we don't want to allow writeback to absorb and queue too many GFP_KERNEL
 * pages if the swap device is very slow.
 */
#define ZCACHE_MAX_OUTSTANDING_WRITEBACK_PAGES 6400

/*
 * Try to allocate two free pages, first using a non-aggressive alloc,
 * then by evicting zcache ephemeral (clean pagecache) pages, and last
 * by aggressive GFP_KERNEL alloc.  We allow zbud to choose a pageframe
 * consisting of 1-2 zbuds/zpages, then call the writeback_zpage helper
 * function above for each.
 */
static int zcache_frontswap_writeback(void)
{
        struct tmem_handle th[2];
        int ret = 0;
        int nzbuds, writeback_ret;
        unsigned type;
        struct page *znewpage1 = NULL, *znewpage2 = NULL;
        struct page *evictpage1 = NULL, *evictpage2 = NULL;
        struct page *newpage1 = NULL, *newpage2 = NULL;
        struct page *page1 = NULL, *page2 = NULL;
        pgoff_t offset;

        znewpage1 = alloc_page(ZCACHE_GFP_MASK);
        znewpage2 = alloc_page(ZCACHE_GFP_MASK);
        if (znewpage1 == NULL)
                evictpage1 = zcache_evict_eph_pageframe();
        if (znewpage2 == NULL)
                evictpage2 = zcache_evict_eph_pageframe();

        if ((evictpage1 == NULL || evictpage2 == NULL) &&
            atomic_read(&zcache_outstanding_writeback_pages_atomic) >
                                ZCACHE_MAX_OUTSTANDING_WRITEBACK_PAGES) {
                goto free_and_out;
        }
        if (znewpage1 == NULL && evictpage1 == NULL)
                newpage1 = alloc_page(GFP_KERNEL);
        if (znewpage2 == NULL && evictpage2 == NULL)
                newpage2 = alloc_page(GFP_KERNEL);
        if (newpage1 == NULL || newpage2 == NULL)
                        goto free_and_out;

        /* ok, we have two pageframes pre-allocated, get a pair of zbuds */
        nzbuds = zbud_make_zombie_lru(&th[0], NULL, NULL, false);
        if (nzbuds == 0) {
                ret = -ENOENT;
                goto free_and_out;
        }

        /* process the first zbud */
        unswiz(th[0].oid, th[0].index, &type, &offset);
        page1 = (znewpage1 != NULL) ? znewpage1 :
                        ((newpage1 != NULL) ? newpage1 : evictpage1);
        writeback_ret = zcache_frontswap_writeback_zpage(type, offset, page1);
        if (writeback_ret < 0) {
                ret = -ENOMEM;
                goto free_and_out;
        }
        if (evictpage1 != NULL)
                zcache_pageframes_freed =
                        atomic_inc_return(&zcache_pageframes_freed_atomic);
        if (writeback_ret == 0) {
                /* zcache_get_swap_cache_page will free, don't double free */
                znewpage1 = NULL;
                newpage1 = NULL;
                evictpage1 = NULL;
        }
        if (nzbuds < 2)
                goto free_and_out;

        /* if there is a second zbud, process it */
        unswiz(th[1].oid, th[1].index, &type, &offset);
        page2 = (znewpage2 != NULL) ? znewpage2 :
                        ((newpage2 != NULL) ? newpage2 : evictpage2);
        writeback_ret = zcache_frontswap_writeback_zpage(type, offset, page2);
        if (writeback_ret < 0) {
                ret = -ENOMEM;
                goto free_and_out;
        }
        if (evictpage2 != NULL)
                zcache_pageframes_freed =
                        atomic_inc_return(&zcache_pageframes_freed_atomic);
        if (writeback_ret == 0) {
                znewpage2 = NULL;
                newpage2 = NULL;
                evictpage2 = NULL;
        }

free_and_out:
        if (znewpage1 != NULL)
                page_cache_release(znewpage1);
        if (znewpage2 != NULL)
                page_cache_release(znewpage2);
        if (newpage1 != NULL)
                page_cache_release(newpage1);
        if (newpage2 != NULL)
                page_cache_release(newpage2);
        if (evictpage1 != NULL)
                zcache_free_page(evictpage1);
        if (evictpage2 != NULL)
                zcache_free_page(evictpage2);
        return ret;
}
#endif /* CONFIG_ZCACHE_WRITEBACK */

/*
 * When zcache is disabled ("frozen"), pools can be created and destroyed,
 * but all puts (and thus all other operations that require memory allocation)
 * must fail.  If zcache is unfrozen, accepts puts, then frozen again,
 * data consistency requires all puts while frozen to be converted into
 * flushes.
 */
static bool zcache_freeze;

/*
 * This zcache shrinker interface reduces the number of ephemeral pageframes
 * used by zcache to approximately the same as the total number of LRU_FILE
 * pageframes in use, and now also reduces the number of persistent pageframes
 * used by zcache to approximately the same as the total number of LRU_ANON
 * pageframes in use.  FIXME POLICY: Probably the writeback should only occur
 * if the eviction doesn't free enough pages.
 */
static int shrink_zcache_memory(struct shrinker *shrink,
                                struct shrink_control *sc)
{
        static bool in_progress;
        int ret = -1;
        int nr = sc->nr_to_scan;
        int nr_evict = 0;
        int nr_writeback = 0;
        struct page *page;
        int  file_pageframes_inuse, anon_pageframes_inuse;

        if (nr <= 0)
                goto skip_evict;

        /* don't allow more than one eviction thread at a time */
        if (in_progress)
                goto skip_evict;

        in_progress = true;

        /* we are going to ignore nr, and target a different value */
        zcache_last_active_file_pageframes =
                global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE);
        zcache_last_inactive_file_pageframes =
                global_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE);
        file_pageframes_inuse = zcache_last_active_file_pageframes +
                                zcache_last_inactive_file_pageframes;
        if (zcache_eph_pageframes > file_pageframes_inuse)
                nr_evict = zcache_eph_pageframes - file_pageframes_inuse;
        else
                nr_evict = 0;
        while (nr_evict-- > 0) {
                page = zcache_evict_eph_pageframe();
                if (page == NULL)
                        break;
                zcache_free_page(page);
        }

        zcache_last_active_anon_pageframes =
                global_page_state(NR_LRU_BASE + LRU_ACTIVE_ANON);
        zcache_last_inactive_anon_pageframes =
                global_page_state(NR_LRU_BASE + LRU_INACTIVE_ANON);
        anon_pageframes_inuse = zcache_last_active_anon_pageframes +
                                zcache_last_inactive_anon_pageframes;
        if (zcache_pers_pageframes > anon_pageframes_inuse)
                nr_writeback = zcache_pers_pageframes - anon_pageframes_inuse;
        else
                nr_writeback = 0;
        while (nr_writeback-- > 0) {
#ifdef CONFIG_ZCACHE_WRITEBACK
                int writeback_ret;
                writeback_ret = zcache_frontswap_writeback();
                if (writeback_ret == -ENOMEM)
#endif
                        break;
        }
        in_progress = false;

skip_evict:
        /* resample: has changed, but maybe not all the way yet */
        zcache_last_active_file_pageframes =
                global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE);
        zcache_last_inactive_file_pageframes =
                global_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE);
        ret = zcache_eph_pageframes - zcache_last_active_file_pageframes +
                zcache_last_inactive_file_pageframes;
        if (ret < 0)
                ret = 0;
        return ret;
}

static struct shrinker zcache_shrinker = {
        .shrink = shrink_zcache_memory,
        .seeks = DEFAULT_SEEKS,
};

/*
 * zcache shims between cleancache/frontswap ops and tmem
 */

/* FIXME rename these core routines to zcache_tmemput etc? */
int zcache_put_page(int cli_id, int pool_id, struct tmem_oid *oidp,
                                uint32_t index, void *page,
                                unsigned int size, bool raw, int ephemeral)
{
        struct tmem_pool *pool;
        struct tmem_handle th;
        int ret = -1;
        void *pampd = NULL;

        BUG_ON(!irqs_disabled());
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        if (unlikely(pool == NULL))
                goto out;
        if (!zcache_freeze) {
                ret = 0;
                th.client_id = cli_id;
                th.pool_id = pool_id;
                th.oid = *oidp;
                th.index = index;
                pampd = zcache_pampd_create((char *)page, size, raw,
                                ephemeral, &th);
                if (pampd == NULL) {
                        ret = -ENOMEM;
                        if (ephemeral)
                                inc_zcache_failed_eph_puts();
                        else
                                inc_zcache_failed_pers_puts();
                } else {
                        if (ramster_enabled)
                                ramster_do_preload_flnode(pool);
                        ret = tmem_put(pool, oidp, index, 0, pampd);
                        if (ret < 0)
                                BUG();
                }
                zcache_put_pool(pool);
        } else {
                inc_zcache_put_to_flush();
                if (ramster_enabled)
                        ramster_do_preload_flnode(pool);
                if (atomic_read(&pool->obj_count) > 0)
                        /* the put fails whether the flush succeeds or not */
                        (void)tmem_flush_page(pool, oidp, index);
                zcache_put_pool(pool);
        }
out:
        return ret;
}

int zcache_get_page(int cli_id, int pool_id, struct tmem_oid *oidp,
                                uint32_t index, void *page,
                                size_t *sizep, bool raw, int get_and_free)
{
        struct tmem_pool *pool;
        int ret = -1;
        bool eph;

        if (!raw) {
                BUG_ON(irqs_disabled());
                BUG_ON(in_softirq());
        }
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        eph = is_ephemeral(pool);
        if (likely(pool != NULL)) {
                if (atomic_read(&pool->obj_count) > 0)
                        ret = tmem_get(pool, oidp, index, (char *)(page),
                                        sizep, raw, get_and_free);
                zcache_put_pool(pool);
        }
        WARN_ONCE((!is_ephemeral(pool) && (ret != 0)),
                        "zcache_get fails on persistent pool, "
                        "bad things are very likely to happen soon\n");
#ifdef RAMSTER_TESTING
        if (ret != 0 && ret != -1 && !(ret == -EINVAL && is_ephemeral(pool)))
                pr_err("TESTING zcache_get tmem_get returns ret=%d\n", ret);
#endif
        return ret;
}

int zcache_flush_page(int cli_id, int pool_id,
                                struct tmem_oid *oidp, uint32_t index)
{
        struct tmem_pool *pool;
        int ret = -1;
        unsigned long flags;

        local_irq_save(flags);
        inc_zcache_flush_total();
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        if (ramster_enabled)
                ramster_do_preload_flnode(pool);
        if (likely(pool != NULL)) {
                if (atomic_read(&pool->obj_count) > 0)
                        ret = tmem_flush_page(pool, oidp, index);
                zcache_put_pool(pool);
        }
        if (ret >= 0)
                inc_zcache_flush_found();
        local_irq_restore(flags);
        return ret;
}

int zcache_flush_object(int cli_id, int pool_id,
                                struct tmem_oid *oidp)
{
        struct tmem_pool *pool;
        int ret = -1;
        unsigned long flags;

        local_irq_save(flags);
        inc_zcache_flobj_total();
        pool = zcache_get_pool_by_id(cli_id, pool_id);
        if (ramster_enabled)
                ramster_do_preload_flnode(pool);
        if (likely(pool != NULL)) {
                if (atomic_read(&pool->obj_count) > 0)
                        ret = tmem_flush_object(pool, oidp);
                zcache_put_pool(pool);
        }
        if (ret >= 0)
                inc_zcache_flobj_found();
        local_irq_restore(flags);
        return ret;
}

static int zcache_client_destroy_pool(int cli_id, int pool_id)
{
        struct tmem_pool *pool = NULL;
        struct zcache_client *cli = NULL;
        int ret = -1;

        if (pool_id < 0)
                goto out;
        if (cli_id == LOCAL_CLIENT)
                cli = &zcache_host;
        else if ((unsigned int)cli_id < MAX_CLIENTS)
                cli = &zcache_clients[cli_id];
        if (cli == NULL)
                goto out;
        atomic_inc(&cli->refcount);
        pool = cli->tmem_pools[pool_id];
        if (pool == NULL)
                goto out;
        cli->tmem_pools[pool_id] = NULL;
        /* wait for pool activity on other cpus to quiesce */
        while (atomic_read(&pool->refcount) != 0)
                ;
        atomic_dec(&cli->refcount);
        local_bh_disable();
        ret = tmem_destroy_pool(pool);
        local_bh_enable();
        kfree(pool);
        if (cli_id == LOCAL_CLIENT)
                pr_info("%s: destroyed local pool id=%d\n", namestr, pool_id);
        else
                pr_info("%s: destroyed pool id=%d, client=%d\n",
                                namestr, pool_id, cli_id);
out:
        return ret;
}

int zcache_new_pool(uint16_t cli_id, uint32_t flags)
{
        int poolid = -1;
        struct tmem_pool *pool;
        struct zcache_client *cli = NULL;

        if (cli_id == LOCAL_CLIENT)
                cli = &zcache_host;
        else if ((unsigned int)cli_id < MAX_CLIENTS)
                cli = &zcache_clients[cli_id];
        if (cli == NULL)
                goto out;
        atomic_inc(&cli->refcount);
        pool = kmalloc(sizeof(struct tmem_pool), GFP_ATOMIC);
        if (pool == NULL)
                goto out;

        for (poolid = 0; poolid < MAX_POOLS_PER_CLIENT; poolid++)
                if (cli->tmem_pools[poolid] == NULL)
                        break;
        if (poolid >= MAX_POOLS_PER_CLIENT) {
                pr_info("%s: pool creation failed: max exceeded\n", namestr);
                kfree(pool);
                poolid = -1;
                goto out;
        }
        atomic_set(&pool->refcount, 0);
        pool->client = cli;
        pool->pool_id = poolid;
        tmem_new_pool(pool, flags);
        cli->tmem_pools[poolid] = pool;
        if (cli_id == LOCAL_CLIENT)
                pr_info("%s: created %s local tmem pool, id=%d\n", namestr,
                        flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
                        poolid);
        else
                pr_info("%s: created %s tmem pool, id=%d, client=%d\n", namestr,
                        flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
                        poolid, cli_id);
out:
        if (cli != NULL)
                atomic_dec(&cli->refcount);
        return poolid;
}

static int zcache_local_new_pool(uint32_t flags)
{
        return zcache_new_pool(LOCAL_CLIENT, flags);
}

int zcache_autocreate_pool(unsigned int cli_id, unsigned int pool_id, bool eph)
{
        struct tmem_pool *pool;
        struct zcache_client *cli = NULL;
        uint32_t flags = eph ? 0 : TMEM_POOL_PERSIST;
        int ret = -1;

        BUG_ON(!ramster_enabled);
        if (cli_id == LOCAL_CLIENT)
                goto out;
        if (pool_id >= MAX_POOLS_PER_CLIENT)
                goto out;
        if (cli_id >= MAX_CLIENTS)
                goto out;

        cli = &zcache_clients[cli_id];
        if ((eph && disable_cleancache) || (!eph && disable_frontswap)) {
                pr_err("zcache_autocreate_pool: pool type disabled\n");
                goto out;
        }
        if (!cli->allocated) {
                if (zcache_new_client(cli_id)) {
                        pr_err("zcache_autocreate_pool: can't create client\n");
                        goto out;
                }
                cli = &zcache_clients[cli_id];
        }
        atomic_inc(&cli->refcount);
        pool = cli->tmem_pools[pool_id];
        if (pool != NULL) {
                if (pool->persistent && eph) {
                        pr_err("zcache_autocreate_pool: type mismatch\n");
                        goto out;
                }
                ret = 0;
                goto out;
        }
        pool = kmalloc(sizeof(struct tmem_pool), GFP_KERNEL);
        if (pool == NULL)
                goto out;

        atomic_set(&pool->refcount, 0);
        pool->client = cli;
        pool->pool_id = pool_id;
        tmem_new_pool(pool, flags);
        cli->tmem_pools[pool_id] = pool;
        pr_info("%s: AUTOcreated %s tmem poolid=%d, for remote client=%d\n",
                namestr, flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
                pool_id, cli_id);
        ret = 0;
out:
        if (cli != NULL)
                atomic_dec(&cli->refcount);
        return ret;
}

/**********
 * Two kernel functionalities currently can be layered on top of tmem.
 * These are "cleancache" which is used as a second-chance cache for clean
 * page cache pages; and "frontswap" which is used for swap pages
 * to avoid writes to disk.  A generic "shim" is provided here for each
 * to translate in-kernel semantics to zcache semantics.
 */

static void zcache_cleancache_put_page(int pool_id,
                                        struct cleancache_filekey key,
                                        pgoff_t index, struct page *page)
{
        u32 ind = (u32) index;
        struct tmem_oid oid = *(struct tmem_oid *)&key;

        if (!disable_cleancache_ignore_nonactive && !PageWasActive(page)) {
                inc_zcache_eph_nonactive_puts_ignored();
                return;
        }
        if (likely(ind == index))
                (void)zcache_put_page(LOCAL_CLIENT, pool_id, &oid, index,
                                        page, PAGE_SIZE, false, 1);
}

static int zcache_cleancache_get_page(int pool_id,
                                        struct cleancache_filekey key,
                                        pgoff_t index, struct page *page)
{
        u32 ind = (u32) index;
        struct tmem_oid oid = *(struct tmem_oid *)&key;
        size_t size;
        int ret = -1;

        if (likely(ind == index)) {
                ret = zcache_get_page(LOCAL_CLIENT, pool_id, &oid, index,
                                        page, &size, false, 0);
                BUG_ON(ret >= 0 && size != PAGE_SIZE);
                if (ret == 0)
                        SetPageWasActive(page);
        }
        return ret;
}

static void zcache_cleancache_flush_page(int pool_id,
                                        struct cleancache_filekey key,
                                        pgoff_t index)
{
        u32 ind = (u32) index;
        struct tmem_oid oid = *(struct tmem_oid *)&key;

        if (likely(ind == index))
                (void)zcache_flush_page(LOCAL_CLIENT, pool_id, &oid, ind);
}

static void zcache_cleancache_flush_inode(int pool_id,
                                        struct cleancache_filekey key)
{
        struct tmem_oid oid = *(struct tmem_oid *)&key;

        (void)zcache_flush_object(LOCAL_CLIENT, pool_id, &oid);
}

static void zcache_cleancache_flush_fs(int pool_id)
{
        if (pool_id >= 0)
                (void)zcache_client_destroy_pool(LOCAL_CLIENT, pool_id);
}

static int zcache_cleancache_init_fs(size_t pagesize)
{
        BUG_ON(sizeof(struct cleancache_filekey) !=
                                sizeof(struct tmem_oid));
        BUG_ON(pagesize != PAGE_SIZE);
        return zcache_local_new_pool(0);
}

static int zcache_cleancache_init_shared_fs(char *uuid, size_t pagesize)
{
        /* shared pools are unsupported and map to private */
        BUG_ON(sizeof(struct cleancache_filekey) !=
                                sizeof(struct tmem_oid));
        BUG_ON(pagesize != PAGE_SIZE);
        return zcache_local_new_pool(0);
}

static struct cleancache_ops zcache_cleancache_ops = {
        .put_page = zcache_cleancache_put_page,
        .get_page = zcache_cleancache_get_page,
        .invalidate_page = zcache_cleancache_flush_page,
        .invalidate_inode = zcache_cleancache_flush_inode,
        .invalidate_fs = zcache_cleancache_flush_fs,
        .init_shared_fs = zcache_cleancache_init_shared_fs,
        .init_fs = zcache_cleancache_init_fs
};

struct cleancache_ops *zcache_cleancache_register_ops(void)
{
        struct cleancache_ops *old_ops =
                cleancache_register_ops(&zcache_cleancache_ops);

        return old_ops;
}

/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
static int zcache_frontswap_poolid __read_mostly = -1;

/*
 * Swizzling increases objects per swaptype, increasing tmem concurrency
 * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
 * Setting SWIZ_BITS to 27 basically reconstructs the swap entry from
 * frontswap_get_page(), but has side-effects. Hence using 8.
 */
#define SWIZ_BITS               8
#define SWIZ_MASK               ((1 << SWIZ_BITS) - 1)
#define _oswiz(_type, _ind)     ((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
#define iswiz(_ind)             (_ind >> SWIZ_BITS)

static inline struct tmem_oid oswiz(unsigned type, u32 ind)
{
        struct tmem_oid oid = { .oid = { 0 } };
        oid.oid[0] = _oswiz(type, ind);
        return oid;
}

#ifdef CONFIG_ZCACHE_WRITEBACK
static void unswiz(struct tmem_oid oid, u32 index,
                                unsigned *type, pgoff_t *offset)
{
        *type = (unsigned)(oid.oid[0] >> SWIZ_BITS);
        *offset = (pgoff_t)((index << SWIZ_BITS) |
                        (oid.oid[0] & SWIZ_MASK));
}
#endif

static int zcache_frontswap_put_page(unsigned type, pgoff_t offset,
                                        struct page *page)
{
        u64 ind64 = (u64)offset;
        u32 ind = (u32)offset;
        struct tmem_oid oid = oswiz(type, ind);
        int ret = -1;
        unsigned long flags;

        BUG_ON(!PageLocked(page));
        if (!disable_frontswap_ignore_nonactive && !PageWasActive(page)) {
                inc_zcache_pers_nonactive_puts_ignored();
                ret = -ERANGE;
                goto out;
        }
        if (likely(ind64 == ind)) {
                local_irq_save(flags);
                ret = zcache_put_page(LOCAL_CLIENT, zcache_frontswap_poolid,
                                        &oid, iswiz(ind),
                                        page, PAGE_SIZE, false, 0);
                local_irq_restore(flags);
        }
out:
        return ret;
}

/* returns 0 if the page was successfully gotten from frontswap, -1 if
 * was not present (should never happen!) */
static int zcache_frontswap_get_page(unsigned type, pgoff_t offset,
                                        struct page *page)
{
        u64 ind64 = (u64)offset;
        u32 ind = (u32)offset;
        struct tmem_oid oid = oswiz(type, ind);
        size_t size;
        int ret = -1, get_and_free;

        if (frontswap_has_exclusive_gets)
                get_and_free = 1;
        else
                get_and_free = -1;
        BUG_ON(!PageLocked(page));
        if (likely(ind64 == ind)) {
                ret = zcache_get_page(LOCAL_CLIENT, zcache_frontswap_poolid,
                                        &oid, iswiz(ind),
                                        page, &size, false, get_and_free);
                BUG_ON(ret >= 0 && size != PAGE_SIZE);
        }
        return ret;
}

/* flush a single page from frontswap */
static void zcache_frontswap_flush_page(unsigned type, pgoff_t offset)
{
        u64 ind64 = (u64)offset;
        u32 ind = (u32)offset;
        struct tmem_oid oid = oswiz(type, ind);

        if (likely(ind64 == ind))
                (void)zcache_flush_page(LOCAL_CLIENT, zcache_frontswap_poolid,
                                        &oid, iswiz(ind));
}

/* flush all pages from the passed swaptype */
static void zcache_frontswap_flush_area(unsigned type)
{
        struct tmem_oid oid;
        int ind;

        for (ind = SWIZ_MASK; ind >= 0; ind--) {
                oid = oswiz(type, ind);
                (void)zcache_flush_object(LOCAL_CLIENT,
                                                zcache_frontswap_poolid, &oid);
        }
}

static void zcache_frontswap_init(unsigned ignored)
{
        /* a single tmem poolid is used for all frontswap "types" (swapfiles) */
        if (zcache_frontswap_poolid < 0)
                zcache_frontswap_poolid =
                        zcache_local_new_pool(TMEM_POOL_PERSIST);
}

static struct frontswap_ops zcache_frontswap_ops = {
        .store = zcache_frontswap_put_page,
        .load = zcache_frontswap_get_page,
        .invalidate_page = zcache_frontswap_flush_page,
        .invalidate_area = zcache_frontswap_flush_area,
        .init = zcache_frontswap_init
};

struct frontswap_ops *zcache_frontswap_register_ops(void)
{
        struct frontswap_ops *old_ops =
                frontswap_register_ops(&zcache_frontswap_ops);

        return old_ops;
}

/*
 * zcache initialization
 * NOTE FOR NOW zcache or ramster MUST BE PROVIDED AS A KERNEL BOOT PARAMETER
 * OR NOTHING HAPPENS!
 */

#ifndef CONFIG_ZCACHE_MODULE
static int __init enable_zcache(char *s)
{
        zcache_enabled = true;
        return 1;
}
__setup("zcache", enable_zcache);

static int __init enable_ramster(char *s)
{
        zcache_enabled = true;
#ifdef CONFIG_RAMSTER
        ramster_enabled = true;
#endif
        return 1;
}
__setup("ramster", enable_ramster);

/* allow independent dynamic disabling of cleancache and frontswap */

static int __init no_cleancache(char *s)
{
        disable_cleancache = true;
        return 1;
}

__setup("nocleancache", no_cleancache);

static int __init no_frontswap(char *s)
{
        disable_frontswap = true;
        return 1;
}

__setup("nofrontswap", no_frontswap);

static int __init no_frontswap_exclusive_gets(char *s)
{
        frontswap_has_exclusive_gets = false;
        return 1;
}

__setup("nofrontswapexclusivegets", no_frontswap_exclusive_gets);

static int __init no_frontswap_ignore_nonactive(char *s)
{
        disable_frontswap_ignore_nonactive = true;
        return 1;
}

__setup("nofrontswapignorenonactive", no_frontswap_ignore_nonactive);

static int __init no_cleancache_ignore_nonactive(char *s)
{
        disable_cleancache_ignore_nonactive = true;
        return 1;
}

__setup("nocleancacheignorenonactive", no_cleancache_ignore_nonactive);

static int __init enable_zcache_compressor(char *s)
{
        strlcpy(zcache_comp_name, s, sizeof(zcache_comp_name));
        zcache_enabled = true;
        return 1;
}
__setup("zcache=", enable_zcache_compressor);
#endif


static int zcache_comp_init(void)
{
        int ret = 0;

        /* check crypto algorithm */
#ifdef CONFIG_ZCACHE_MODULE
        ret = crypto_has_comp(zcache_comp_name, 0, 0);
        if (!ret) {
                ret = -1;
                goto out;
        }
#else
        if (*zcache_comp_name != '\0') {
                ret = crypto_has_comp(zcache_comp_name, 0, 0);
                if (!ret)
                        pr_info("zcache: %s not supported\n",
                                        zcache_comp_name);
                goto out;
        }
        if (!ret)
                strcpy(zcache_comp_name, "lzo");
        ret = crypto_has_comp(zcache_comp_name, 0, 0);
        if (!ret) {
                ret = 1;
                goto out;
        }
#endif
        pr_info("zcache: using %s compressor\n", zcache_comp_name);

        /* alloc percpu transforms */
        ret = 0;
        zcache_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
        if (!zcache_comp_pcpu_tfms)
                ret = 1;
out:
        return ret;
}

static int zcache_init(void)
{
        int ret = 0;

#ifdef CONFIG_ZCACHE_MODULE
        zcache_enabled = 1;
#endif
        if (ramster_enabled) {
                namestr = "ramster";
                ramster_register_pamops(&zcache_pamops);
        }
        zcache_debugfs_init();
        if (zcache_enabled) {
                unsigned int cpu;

                tmem_register_hostops(&zcache_hostops);
                tmem_register_pamops(&zcache_pamops);
                ret = register_cpu_notifier(&zcache_cpu_notifier_block);
                if (ret) {
                        pr_err("%s: can't register cpu notifier\n", namestr);
                        goto out;
                }
                ret = zcache_comp_init();
                if (ret) {
                        pr_err("%s: compressor initialization failed\n",
                                namestr);
                        goto out;
                }
                for_each_online_cpu(cpu) {
                        void *pcpu = (void *)(long)cpu;
                        zcache_cpu_notifier(&zcache_cpu_notifier_block,
                                CPU_UP_PREPARE, pcpu);
                }
        }
        zcache_objnode_cache = kmem_cache_create("zcache_objnode",
                                sizeof(struct tmem_objnode), 0, 0, NULL);
        zcache_obj_cache = kmem_cache_create("zcache_obj",
                                sizeof(struct tmem_obj), 0, 0, NULL);
        ret = zcache_new_client(LOCAL_CLIENT);
        if (ret) {
                pr_err("%s: can't create client\n", namestr);
                goto out;
        }
        zbud_init();
        if (zcache_enabled && !disable_cleancache) {
                struct cleancache_ops *old_ops;

                register_shrinker(&zcache_shrinker);
                old_ops = zcache_cleancache_register_ops();
                pr_info("%s: cleancache enabled using kernel transcendent "
                        "memory and compression buddies\n", namestr);
#ifdef CONFIG_ZCACHE_DEBUG
                pr_info("%s: cleancache: ignorenonactive = %d\n",
                        namestr, !disable_cleancache_ignore_nonactive);
#endif
                if (old_ops != NULL)
                        pr_warn("%s: cleancache_ops overridden\n", namestr);
        }
        if (zcache_enabled && !disable_frontswap) {
                struct frontswap_ops *old_ops;

                old_ops = zcache_frontswap_register_ops();
                if (frontswap_has_exclusive_gets)
                        frontswap_tmem_exclusive_gets(true);
                pr_info("%s: frontswap enabled using kernel transcendent "
                        "memory and compression buddies\n", namestr);
#ifdef CONFIG_ZCACHE_DEBUG
                pr_info("%s: frontswap: excl gets = %d active only = %d\n",
                        namestr, frontswap_has_exclusive_gets,
                        !disable_frontswap_ignore_nonactive);
#endif
                if (IS_ERR(old_ops) || old_ops) {
                        if (IS_ERR(old_ops))
                                return PTR_RET(old_ops);
                        pr_warn("%s: frontswap_ops overridden\n", namestr);
                }
        }
        if (ramster_enabled)
                ramster_init(!disable_cleancache, !disable_frontswap,
                                frontswap_has_exclusive_gets,
                                !disable_frontswap_selfshrink);
out:
        return ret;
}

#ifdef CONFIG_ZCACHE_MODULE
#ifdef CONFIG_RAMSTER
module_param(ramster_enabled, bool, S_IRUGO);
module_param(disable_frontswap_selfshrink, int, S_IRUGO);
#endif
module_param(disable_cleancache, bool, S_IRUGO);
module_param(disable_frontswap, bool, S_IRUGO);
#ifdef FRONTSWAP_HAS_EXCLUSIVE_GETS
module_param(frontswap_has_exclusive_gets, bool, S_IRUGO);
#endif
module_param(disable_frontswap_ignore_nonactive, bool, S_IRUGO);
module_param(zcache_comp_name, charp, S_IRUGO);
module_init(zcache_init);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dan Magenheimer <dan.magenheimer@oracle.com>");
MODULE_DESCRIPTION("In-kernel compression of cleancache/frontswap pages");
#else
late_initcall(zcache_init);
#endif