xref: /drivers/staging/ramster/zcache-main.c

/*
 * 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
 * and, thus indirectly, for cleancache and frontswap.  Zcache includes two
 * page-accessible memory [1] interfaces, both utilizing lzo1x compression:
 * 1) "compression buddies" ("zbud") is used for ephemeral pages
 * 2) xvmalloc is used for persistent pages.
 * Xvmalloc (based on the TLSF allocator) has very low fragmentation
 * so maximizes space efficiency, while zbud allows pairs (and potentially,
 * in the future, more than a pair of) compressed pages to be closely linked
 * so that reclaiming can be done via the kernel's physical-page-oriented
 * "shrinker" interface.
 *
 * [1] For a definition of page-accessible memory (aka PAM), see:
 *   http://marc.info/?l=linux-mm&m=127811271605009
 *  RAMSTER TODO:
 *   - handle remotifying of buddied pages (see zbud_remotify_zbpg)
 *   - kernel boot params: nocleancache/nofrontswap don't always work?!?
 */

#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/lzo.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/math64.h>
#include "tmem.h"
#include "zcache.h"
#include "ramster.h"
#include "cluster/tcp.h"

#include "xvmalloc.h"	/* temporary until change to zsmalloc */

#define	RAMSTER_TESTING

#if (!defined(CONFIG_CLEANCACHE) && !defined(CONFIG_FRONTSWAP))
#error "ramster is useless without CONFIG_CLEANCACHE or CONFIG_FRONTSWAP"
#endif
#ifdef CONFIG_CLEANCACHE
#include <linux/cleancache.h>
#endif
#ifdef CONFIG_FRONTSWAP
#include <linux/frontswap.h>
#endif

enum ramster_remotify_op {
	RAMSTER_REMOTIFY_EPH_PUT,
	RAMSTER_REMOTIFY_PERS_PUT,
	RAMSTER_REMOTIFY_FLUSH_PAGE,
	RAMSTER_REMOTIFY_FLUSH_OBJ,
	RAMSTER_INTRANSIT_PERS
};

struct ramster_remotify_hdr {
	enum ramster_remotify_op op;
	struct list_head list;
};

#define ZBH_SENTINEL  0x43214321
#define ZBPG_SENTINEL  0xdeadbeef

#define ZBUD_MAX_BUDS 2

struct zbud_hdr {
	struct ramster_remotify_hdr rem_op;
	uint16_t client_id;
	uint16_t pool_id;
	struct tmem_oid oid;
	uint32_t index;
	uint16_t size; /* compressed size in bytes, zero means unused */
	DECL_SENTINEL
};

#define ZVH_SENTINEL  0x43214321
static const int zv_max_page_size = (PAGE_SIZE / 8) * 7;

struct zv_hdr {
	struct ramster_remotify_hdr rem_op;
	uint16_t client_id;
	uint16_t pool_id;
	struct tmem_oid oid;
	uint32_t index;
	DECL_SENTINEL
};

struct flushlist_node {
	struct ramster_remotify_hdr rem_op;
	struct tmem_xhandle xh;
};

union {
	struct ramster_remotify_hdr rem_op;
	struct zv_hdr zv;
	struct zbud_hdr zbud;
	struct flushlist_node flist;
} remotify_list_node;

static LIST_HEAD(zcache_rem_op_list);
static DEFINE_SPINLOCK(zcache_rem_op_list_lock);

#if 0
/* this is more aggressive but may cause other problems? */
#define ZCACHE_GFP_MASK	(GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN)
#else
#define ZCACHE_GFP_MASK \
	(__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC)
#endif

#define MAX_POOLS_PER_CLIENT 16

#define MAX_CLIENTS 16
#define LOCAL_CLIENT ((uint16_t)-1)

MODULE_LICENSE("GPL");

struct zcache_client {
	struct tmem_pool *tmem_pools[MAX_POOLS_PER_CLIENT];
	struct xv_pool *xvpool;
	bool allocated;
	atomic_t refcount;
};

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

static inline uint16_t get_client_id_from_client(struct zcache_client *cli)
{
	BUG_ON(cli == NULL);
	if (cli == &zcache_host)
		return LOCAL_CLIENT;
	return cli - &zcache_clients[0];
}

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

/**********
 * Compression buddies ("zbud") provides for packing two (or, possibly
 * in the future, more) compressed ephemeral pages into a single "raw"
 * (physical) page and tracking them with data structures so that
 * the raw pages can be easily reclaimed.
 *
 * A zbud page ("zbpg") is an aligned page containing a list_head,
 * a lock, and two "zbud headers".  The remainder of the physical
 * page is divided up into aligned 64-byte "chunks" which contain
 * the compressed data for zero, one, or two zbuds.  Each zbpg
 * resides on: (1) an "unused list" if it has no zbuds; (2) a
 * "buddied" list if it is fully populated  with two zbuds; or
 * (3) one of PAGE_SIZE/64 "unbuddied" lists indexed by how many chunks
 * the one unbuddied zbud uses.  The data inside a zbpg cannot be
 * read or written unless the zbpg's lock is held.
 */

struct zbud_page {
	struct list_head bud_list;
	spinlock_t lock;
	struct zbud_hdr buddy[ZBUD_MAX_BUDS];
	DECL_SENTINEL
	/* followed by NUM_CHUNK aligned CHUNK_SIZE-byte chunks */
};

#define CHUNK_SHIFT	6
#define CHUNK_SIZE	(1 << CHUNK_SHIFT)
#define CHUNK_MASK	(~(CHUNK_SIZE-1))
#define NCHUNKS		(((PAGE_SIZE - sizeof(struct zbud_page)) & \
				CHUNK_MASK) >> CHUNK_SHIFT)
#define MAX_CHUNK	(NCHUNKS-1)

static struct {
	struct list_head list;
	unsigned count;
} zbud_unbuddied[NCHUNKS];
/* list N contains pages with N chunks USED and NCHUNKS-N unused */
/* element 0 is never used but optimizing that isn't worth it */
static unsigned long zbud_cumul_chunk_counts[NCHUNKS];

struct list_head zbud_buddied_list;
static unsigned long zcache_zbud_buddied_count;

/* protects the buddied list and all unbuddied lists */
static DEFINE_SPINLOCK(zbud_budlists_spinlock);

static atomic_t zcache_zbud_curr_raw_pages;
static atomic_t zcache_zbud_curr_zpages;
static unsigned long zcache_zbud_curr_zbytes;
static unsigned long zcache_zbud_cumul_zpages;
static unsigned long zcache_zbud_cumul_zbytes;
static unsigned long zcache_compress_poor;
static unsigned long zcache_policy_percent_exceeded;
static unsigned long zcache_mean_compress_poor;

/*
 * RAMster counters
 * - Remote pages are pages with a local pampd but the data is remote
 * - Foreign pages are pages stored locally but belonging to another node
 */
static atomic_t ramster_remote_pers_pages = ATOMIC_INIT(0);
static unsigned long ramster_pers_remotify_enable;
static unsigned long ramster_eph_remotify_enable;
static unsigned long ramster_eph_pages_remoted;
static unsigned long ramster_eph_pages_remote_failed;
static unsigned long ramster_pers_pages_remoted;
static unsigned long ramster_pers_pages_remote_failed;
static unsigned long ramster_pers_pages_remote_nomem;
static unsigned long ramster_remote_objects_flushed;
static unsigned long ramster_remote_object_flushes_failed;
static unsigned long ramster_remote_pages_flushed;
static unsigned long ramster_remote_page_flushes_failed;
static unsigned long ramster_remote_eph_pages_succ_get;
static unsigned long ramster_remote_pers_pages_succ_get;
static unsigned long ramster_remote_eph_pages_unsucc_get;
static unsigned long ramster_remote_pers_pages_unsucc_get;
static atomic_t ramster_curr_flnode_count = ATOMIC_INIT(0);
static unsigned long ramster_curr_flnode_count_max;
static atomic_t ramster_foreign_eph_pampd_count = ATOMIC_INIT(0);
static unsigned long ramster_foreign_eph_pampd_count_max;
static atomic_t ramster_foreign_pers_pampd_count = ATOMIC_INIT(0);
static unsigned long ramster_foreign_pers_pampd_count_max;

/* forward references */
static void *zcache_get_free_page(void);
static void zcache_free_page(void *p);

/*
 * zbud helper functions
 */

static inline unsigned zbud_max_buddy_size(void)
{
	return MAX_CHUNK << CHUNK_SHIFT;
}

static inline unsigned zbud_size_to_chunks(unsigned size)
{
	BUG_ON(size == 0 || size > zbud_max_buddy_size());
	return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
}

static inline int zbud_budnum(struct zbud_hdr *zh)
{
	unsigned offset = (unsigned long)zh & (PAGE_SIZE - 1);
	struct zbud_page *zbpg = NULL;
	unsigned budnum = -1U;
	int i;

	for (i = 0; i < ZBUD_MAX_BUDS; i++)
		if (offset == offsetof(typeof(*zbpg), buddy[i])) {
			budnum = i;
			break;
		}
	BUG_ON(budnum == -1U);
	return budnum;
}

static char *zbud_data(struct zbud_hdr *zh, unsigned size)
{
	struct zbud_page *zbpg;
	char *p;
	unsigned budnum;

	ASSERT_SENTINEL(zh, ZBH);
	budnum = zbud_budnum(zh);
	BUG_ON(size == 0 || size > zbud_max_buddy_size());
	zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
	ASSERT_SPINLOCK(&zbpg->lock);
	p = (char *)zbpg;
	if (budnum == 0)
		p += ((sizeof(struct zbud_page) + CHUNK_SIZE - 1) &
							CHUNK_MASK);
	else if (budnum == 1)
		p += PAGE_SIZE - ((size + CHUNK_SIZE - 1) & CHUNK_MASK);
	return p;
}

static void zbud_copy_from_pampd(char *data, size_t *size, struct zbud_hdr *zh)
{
	struct zbud_page *zbpg;
	char *p;
	unsigned budnum;

	ASSERT_SENTINEL(zh, ZBH);
	budnum = zbud_budnum(zh);
	zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
	spin_lock(&zbpg->lock);
	BUG_ON(zh->size > *size);
	p = (char *)zbpg;
	if (budnum == 0)
		p += ((sizeof(struct zbud_page) + CHUNK_SIZE - 1) &
							CHUNK_MASK);
	else if (budnum == 1)
		p += PAGE_SIZE - ((zh->size + CHUNK_SIZE - 1) & CHUNK_MASK);
	/* client should be filled in by caller */
	memcpy(data, p, zh->size);
	*size = zh->size;
	spin_unlock(&zbpg->lock);
}

/*
 * zbud raw page management
 */

static struct zbud_page *zbud_alloc_raw_page(void)
{
	struct zbud_page *zbpg = NULL;
	struct zbud_hdr *zh0, *zh1;
		zbpg = zcache_get_free_page();
	if (likely(zbpg != NULL)) {
		INIT_LIST_HEAD(&zbpg->bud_list);
		zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1];
		spin_lock_init(&zbpg->lock);
		atomic_inc(&zcache_zbud_curr_raw_pages);
		INIT_LIST_HEAD(&zbpg->bud_list);
		SET_SENTINEL(zbpg, ZBPG);
		zh0->size = 0; zh1->size = 0;
		tmem_oid_set_invalid(&zh0->oid);
		tmem_oid_set_invalid(&zh1->oid);
	}
	return zbpg;
}

static void zbud_free_raw_page(struct zbud_page *zbpg)
{
	struct zbud_hdr *zh0 = &zbpg->buddy[0], *zh1 = &zbpg->buddy[1];

	ASSERT_SENTINEL(zbpg, ZBPG);
	BUG_ON(!list_empty(&zbpg->bud_list));
	ASSERT_SPINLOCK(&zbpg->lock);
	BUG_ON(zh0->size != 0 || tmem_oid_valid(&zh0->oid));
	BUG_ON(zh1->size != 0 || tmem_oid_valid(&zh1->oid));
	INVERT_SENTINEL(zbpg, ZBPG);
	spin_unlock(&zbpg->lock);
	atomic_dec(&zcache_zbud_curr_raw_pages);
	zcache_free_page(zbpg);
}

/*
 * core zbud handling routines
 */

static unsigned zbud_free(struct zbud_hdr *zh)
{
	unsigned size;

	ASSERT_SENTINEL(zh, ZBH);
	BUG_ON(!tmem_oid_valid(&zh->oid));
	size = zh->size;
	BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size());
	zh->size = 0;
	tmem_oid_set_invalid(&zh->oid);
	INVERT_SENTINEL(zh, ZBH);
	zcache_zbud_curr_zbytes -= size;
	atomic_dec(&zcache_zbud_curr_zpages);
	return size;
}

static void zbud_free_and_delist(struct zbud_hdr *zh)
{
	unsigned chunks;
	struct zbud_hdr *zh_other;
	unsigned budnum = zbud_budnum(zh), size;
	struct zbud_page *zbpg =
		container_of(zh, struct zbud_page, buddy[budnum]);

	/* FIXME, should be BUG_ON, pool destruction path doesn't disable
	 * interrupts tmem_destroy_pool()->tmem_pampd_destroy_all_in_obj()->
	 * tmem_objnode_node_destroy()-> zcache_pampd_free() */
	WARN_ON(!irqs_disabled());
	spin_lock(&zbpg->lock);
	if (list_empty(&zbpg->bud_list)) {
		/* ignore zombie page... see zbud_evict_pages() */
		spin_unlock(&zbpg->lock);
		return;
	}
	size = zbud_free(zh);
	ASSERT_SPINLOCK(&zbpg->lock);
	zh_other = &zbpg->buddy[(budnum == 0) ? 1 : 0];
	if (zh_other->size == 0) { /* was unbuddied: unlist and free */
		chunks = zbud_size_to_chunks(size) ;
		spin_lock(&zbud_budlists_spinlock);
		BUG_ON(list_empty(&zbud_unbuddied[chunks].list));
		list_del_init(&zbpg->bud_list);
		zbud_unbuddied[chunks].count--;
		spin_unlock(&zbud_budlists_spinlock);
		zbud_free_raw_page(zbpg);
	} else { /* was buddied: move remaining buddy to unbuddied list */
		chunks = zbud_size_to_chunks(zh_other->size) ;
		spin_lock(&zbud_budlists_spinlock);
		list_del_init(&zbpg->bud_list);
		zcache_zbud_buddied_count--;
		list_add_tail(&zbpg->bud_list, &zbud_unbuddied[chunks].list);
		zbud_unbuddied[chunks].count++;
		spin_unlock(&zbud_budlists_spinlock);
		spin_unlock(&zbpg->lock);
	}
}

static struct zbud_hdr *zbud_create(uint16_t client_id, uint16_t pool_id,
					struct tmem_oid *oid,
					uint32_t index, struct page *page,
					void *cdata, unsigned size)
{
	struct zbud_hdr *zh0, *zh1, *zh = NULL;
	struct zbud_page *zbpg = NULL, *ztmp;
	unsigned nchunks;
	char *to;
	int i, found_good_buddy = 0;

	nchunks = zbud_size_to_chunks(size) ;
	for (i = MAX_CHUNK - nchunks + 1; i > 0; i--) {
		spin_lock(&zbud_budlists_spinlock);
		if (!list_empty(&zbud_unbuddied[i].list)) {
			list_for_each_entry_safe(zbpg, ztmp,
				    &zbud_unbuddied[i].list, bud_list) {
				if (spin_trylock(&zbpg->lock)) {
					found_good_buddy = i;
					goto found_unbuddied;
				}
			}
		}
		spin_unlock(&zbud_budlists_spinlock);
	}
	/* didn't find a good buddy, try allocating a new page */
	zbpg = zbud_alloc_raw_page();
	if (unlikely(zbpg == NULL))
		goto out;
	/* ok, have a page, now compress the data before taking locks */
	spin_lock(&zbud_budlists_spinlock);
	spin_lock(&zbpg->lock);
	list_add_tail(&zbpg->bud_list, &zbud_unbuddied[nchunks].list);
	zbud_unbuddied[nchunks].count++;
	zh = &zbpg->buddy[0];
	goto init_zh;

found_unbuddied:
	ASSERT_SPINLOCK(&zbpg->lock);
	zh0 = &zbpg->buddy[0]; zh1 = &zbpg->buddy[1];
	BUG_ON(!((zh0->size == 0) ^ (zh1->size == 0)));
	if (zh0->size != 0) { /* buddy0 in use, buddy1 is vacant */
		ASSERT_SENTINEL(zh0, ZBH);
		zh = zh1;
	} else if (zh1->size != 0) { /* buddy1 in use, buddy0 is vacant */
		ASSERT_SENTINEL(zh1, ZBH);
		zh = zh0;
	} else
		BUG();
	list_del_init(&zbpg->bud_list);
	zbud_unbuddied[found_good_buddy].count--;
	list_add_tail(&zbpg->bud_list, &zbud_buddied_list);
	zcache_zbud_buddied_count++;

init_zh:
	SET_SENTINEL(zh, ZBH);
	zh->size = size;
	zh->index = index;
	zh->oid = *oid;
	zh->pool_id = pool_id;
	zh->client_id = client_id;
	to = zbud_data(zh, size);
	memcpy(to, cdata, size);
	spin_unlock(&zbpg->lock);
	spin_unlock(&zbud_budlists_spinlock);
	zbud_cumul_chunk_counts[nchunks]++;
	atomic_inc(&zcache_zbud_curr_zpages);
	zcache_zbud_cumul_zpages++;
	zcache_zbud_curr_zbytes += size;
	zcache_zbud_cumul_zbytes += size;
out:
	return zh;
}

static int zbud_decompress(struct page *page, struct zbud_hdr *zh)
{
	struct zbud_page *zbpg;
	unsigned budnum = zbud_budnum(zh);
	size_t out_len = PAGE_SIZE;
	char *to_va, *from_va;
	unsigned size;
	int ret = 0;

	zbpg = container_of(zh, struct zbud_page, buddy[budnum]);
	spin_lock(&zbpg->lock);
	if (list_empty(&zbpg->bud_list)) {
		/* ignore zombie page... see zbud_evict_pages() */
		ret = -EINVAL;
		goto out;
	}
	ASSERT_SENTINEL(zh, ZBH);
	BUG_ON(zh->size == 0 || zh->size > zbud_max_buddy_size());
	to_va = kmap_atomic(page);
	size = zh->size;
	from_va = zbud_data(zh, size);
	ret = lzo1x_decompress_safe(from_va, size, to_va, &out_len);
	BUG_ON(ret != LZO_E_OK);
	BUG_ON(out_len != PAGE_SIZE);
	kunmap_atomic(to_va);
out:
	spin_unlock(&zbpg->lock);
	return ret;
}

/*
 * The following routines handle shrinking of ephemeral pages by evicting
 * pages "least valuable" first.
 */

static unsigned long zcache_evicted_raw_pages;
static unsigned long zcache_evicted_buddied_pages;
static unsigned long zcache_evicted_unbuddied_pages;

static struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id,
						uint16_t poolid);
static void zcache_put_pool(struct tmem_pool *pool);

/*
 * Flush and free all zbuds in a zbpg, then free the pageframe
 */
static void zbud_evict_zbpg(struct zbud_page *zbpg)
{
	struct zbud_hdr *zh;
	int i, j;
	uint32_t pool_id[ZBUD_MAX_BUDS], client_id[ZBUD_MAX_BUDS];
	uint32_t index[ZBUD_MAX_BUDS];
	struct tmem_oid oid[ZBUD_MAX_BUDS];
	struct tmem_pool *pool;
	unsigned long flags;

	ASSERT_SPINLOCK(&zbpg->lock);
	for (i = 0, j = 0; i < ZBUD_MAX_BUDS; i++) {
		zh = &zbpg->buddy[i];
		if (zh->size) {
			client_id[j] = zh->client_id;
			pool_id[j] = zh->pool_id;
			oid[j] = zh->oid;
			index[j] = zh->index;
			j++;
		}
	}
	spin_unlock(&zbpg->lock);
	for (i = 0; i < j; i++) {
		pool = zcache_get_pool_by_id(client_id[i], pool_id[i]);
		BUG_ON(pool == NULL);
		local_irq_save(flags);
		/* these flushes should dispose of any local storage */
		tmem_flush_page(pool, &oid[i], index[i]);
		local_irq_restore(flags);
		zcache_put_pool(pool);
	}
}

/*
 * Free nr pages.  This code is funky because we want to hold the locks
 * protecting various lists for as short a time as possible, and in some
 * circumstances the list may change asynchronously when the list lock is
 * not held.  In some cases we also trylock not only to avoid waiting on a
 * page in use by another cpu, but also to avoid potential deadlock due to
 * lock inversion.
 */
static void zbud_evict_pages(int nr)
{
	struct zbud_page *zbpg;
	int i, newly_unused_pages = 0;


	/* now try freeing unbuddied pages, starting with least space avail */
	for (i = 0; i < MAX_CHUNK; i++) {
retry_unbud_list_i:
		spin_lock_bh(&zbud_budlists_spinlock);
		if (list_empty(&zbud_unbuddied[i].list)) {
			spin_unlock_bh(&zbud_budlists_spinlock);
			continue;
		}
		list_for_each_entry(zbpg, &zbud_unbuddied[i].list, bud_list) {
			if (unlikely(!spin_trylock(&zbpg->lock)))
				continue;
			zbud_unbuddied[i].count--;
			spin_unlock(&zbud_budlists_spinlock);
			zcache_evicted_unbuddied_pages++;
			/* want budlists unlocked when doing zbpg eviction */
			zbud_evict_zbpg(zbpg);
			newly_unused_pages++;
			local_bh_enable();
			if (--nr <= 0)
				goto evict_unused;
			goto retry_unbud_list_i;
		}
		spin_unlock_bh(&zbud_budlists_spinlock);
	}

	/* as a last resort, free buddied pages */
retry_bud_list:
	spin_lock_bh(&zbud_budlists_spinlock);
	if (list_empty(&zbud_buddied_list)) {
		spin_unlock_bh(&zbud_budlists_spinlock);
		goto evict_unused;
	}
	list_for_each_entry(zbpg, &zbud_buddied_list, bud_list) {
		if (unlikely(!spin_trylock(&zbpg->lock)))
			continue;
		zcache_zbud_buddied_count--;
		spin_unlock(&zbud_budlists_spinlock);
		zcache_evicted_buddied_pages++;
		/* want budlists unlocked when doing zbpg eviction */
		zbud_evict_zbpg(zbpg);
		newly_unused_pages++;
		local_bh_enable();
		if (--nr <= 0)
			goto evict_unused;
		goto retry_bud_list;
	}
	spin_unlock_bh(&zbud_budlists_spinlock);

evict_unused:
	return;
}

static DEFINE_PER_CPU(unsigned char *, zcache_remoteputmem);

static int zbud_remotify_zbud(struct tmem_xhandle *xh, char *data,
				size_t size)
{
	struct tmem_pool *pool;
	int i, remotenode, ret = -1;
	unsigned char cksum, *p;
	unsigned long flags;

	for (p = data, cksum = 0, i = 0; i < size; i++)
		cksum += *p;
	ret = ramster_remote_put(xh, data, size, true, &remotenode);
	if (ret == 0) {
		/* data was successfully remoted so change the local version
		 * to point to the remote node where it landed */
		pool = zcache_get_pool_by_id(LOCAL_CLIENT, xh->pool_id);
		BUG_ON(pool == NULL);
		local_irq_save(flags);
		/* tmem_replace will also free up any local space */
		(void)tmem_replace(pool, &xh->oid, xh->index,
			pampd_make_remote(remotenode, size, cksum));
		local_irq_restore(flags);
		zcache_put_pool(pool);
		ramster_eph_pages_remoted++;
		ret = 0;
	} else
		ramster_eph_pages_remote_failed++;
	return ret;
}

static int zbud_remotify_zbpg(struct zbud_page *zbpg)
{
	struct zbud_hdr *zh1, *zh2 = NULL;
	struct tmem_xhandle xh1, xh2 = { 0 };
	char *data1 = NULL, *data2 = NULL;
	size_t size1 = 0, size2 = 0;
	int ret = 0;
	unsigned char *tmpmem = __get_cpu_var(zcache_remoteputmem);

	ASSERT_SPINLOCK(&zbpg->lock);
	if (zbpg->buddy[0].size == 0)
		zh1 = &zbpg->buddy[1];
	else if (zbpg->buddy[1].size == 0)
		zh1 = &zbpg->buddy[0];
	else {
		zh1 = &zbpg->buddy[0];
		zh2 = &zbpg->buddy[1];
	}
	/* don't remotify pages that are already remotified */
	if (zh1->client_id != LOCAL_CLIENT)
		zh1 = NULL;
	if ((zh2 != NULL) && (zh2->client_id != LOCAL_CLIENT))
		zh2 = NULL;

	/* copy the data and metadata so can release lock */
	if (zh1 != NULL) {
		xh1.client_id = zh1->client_id;
		xh1.pool_id = zh1->pool_id;
		xh1.oid = zh1->oid;
		xh1.index = zh1->index;
		size1 = zh1->size;
		data1 = zbud_data(zh1, size1);
		memcpy(tmpmem, zbud_data(zh1, size1), size1);
		data1 = tmpmem;
		tmpmem += size1;
	}
	if (zh2 != NULL) {
		xh2.client_id = zh2->client_id;
		xh2.pool_id = zh2->pool_id;
		xh2.oid = zh2->oid;
		xh2.index = zh2->index;
		size2 = zh2->size;
		memcpy(tmpmem, zbud_data(zh2, size2), size2);
		data2 = tmpmem;
	}
	spin_unlock(&zbpg->lock);
	preempt_enable();

	/* OK, no locks held anymore, remotify one or both zbuds */
	if (zh1 != NULL)
		ret = zbud_remotify_zbud(&xh1, data1, size1);
	if (zh2 != NULL)
		ret |= zbud_remotify_zbud(&xh2, data2, size2);
	return ret;
}

void zbud_remotify_pages(int nr)
{
	struct zbud_page *zbpg;
	int i, ret;

	/*
	 * for now just try remotifying unbuddied pages, starting with
	 * least space avail
	 */
	for (i = 0; i < MAX_CHUNK; i++) {
retry_unbud_list_i:
		preempt_disable();  /* enable in zbud_remotify_zbpg */
		spin_lock_bh(&zbud_budlists_spinlock);
		if (list_empty(&zbud_unbuddied[i].list)) {
			spin_unlock_bh(&zbud_budlists_spinlock);
			preempt_enable();
			continue; /* next i in for loop */
		}
		list_for_each_entry(zbpg, &zbud_unbuddied[i].list, bud_list) {
			if (unlikely(!spin_trylock(&zbpg->lock)))
				continue; /* next list_for_each_entry */
			zbud_unbuddied[i].count--;
			/* want budlists unlocked when doing zbpg remotify */
			spin_unlock_bh(&zbud_budlists_spinlock);
			ret = zbud_remotify_zbpg(zbpg);
			/* preemption is re-enabled in zbud_remotify_zbpg */
			if (ret == 0) {
				if (--nr <= 0)
					goto out;
				goto retry_unbud_list_i;
			}
			/* if fail to remotify any page, quit */
			pr_err("TESTING zbud_remotify_pages failed on page,"
				" trying to re-add\n");
			spin_lock_bh(&zbud_budlists_spinlock);
			spin_lock(&zbpg->lock);
			list_add_tail(&zbpg->bud_list, &zbud_unbuddied[i].list);
			zbud_unbuddied[i].count++;
			spin_unlock(&zbpg->lock);
			spin_unlock_bh(&zbud_budlists_spinlock);
			pr_err("TESTING zbud_remotify_pages failed on page,"
				" finished re-add\n");
			goto out;
		}
		spin_unlock_bh(&zbud_budlists_spinlock);
		preempt_enable();
	}

next_buddied_zbpg:
	preempt_disable();  /* enable in zbud_remotify_zbpg */
	spin_lock_bh(&zbud_budlists_spinlock);
	if (list_empty(&zbud_buddied_list))
		goto unlock_out;
	list_for_each_entry(zbpg, &zbud_buddied_list, bud_list) {
		if (unlikely(!spin_trylock(&zbpg->lock)))
			continue; /* next list_for_each_entry */
		zcache_zbud_buddied_count--;
		/* want budlists unlocked when doing zbpg remotify */
		spin_unlock_bh(&zbud_budlists_spinlock);
		ret = zbud_remotify_zbpg(zbpg);
		/* preemption is re-enabled in zbud_remotify_zbpg */
		if (ret == 0) {
			if (--nr <= 0)
				goto out;
			goto next_buddied_zbpg;
		}
		/* if fail to remotify any page, quit */
		pr_err("TESTING zbud_remotify_pages failed on BUDDIED page,"
			" trying to re-add\n");
		spin_lock_bh(&zbud_budlists_spinlock);
		spin_lock(&zbpg->lock);
		list_add_tail(&zbpg->bud_list, &zbud_buddied_list);
		zcache_zbud_buddied_count++;
		spin_unlock(&zbpg->lock);
		spin_unlock_bh(&zbud_budlists_spinlock);
		pr_err("TESTING zbud_remotify_pages failed on BUDDIED page,"
			" finished re-add\n");
		goto out;
	}
unlock_out:
	spin_unlock_bh(&zbud_budlists_spinlock);
	preempt_enable();
out:
	return;
}

/* the "flush list" asynchronously collects pages to remotely flush */
#define FLUSH_ENTIRE_OBJECT ((uint32_t)-1)
static void ramster_flnode_free(struct flushlist_node *,
				struct tmem_pool *);

static void zcache_remote_flush_page(struct flushlist_node *flnode)
{
	struct tmem_xhandle *xh;
	int remotenode, ret;

	preempt_disable();
	xh = &flnode->xh;
	remotenode = flnode->xh.client_id;
	ret = ramster_remote_flush(xh, remotenode);
	if (ret >= 0)
		ramster_remote_pages_flushed++;
	else
		ramster_remote_page_flushes_failed++;
	preempt_enable_no_resched();
	ramster_flnode_free(flnode, NULL);
}

static void zcache_remote_flush_object(struct flushlist_node *flnode)
{
	struct tmem_xhandle *xh;
	int remotenode, ret;

	preempt_disable();
	xh = &flnode->xh;
	remotenode = flnode->xh.client_id;
	ret = ramster_remote_flush_object(xh, remotenode);
	if (ret >= 0)
		ramster_remote_objects_flushed++;
	else
		ramster_remote_object_flushes_failed++;
	preempt_enable_no_resched();
	ramster_flnode_free(flnode, NULL);
}

static void zcache_remote_eph_put(struct zbud_hdr *zbud)
{
	/* FIXME */
}

static void zcache_remote_pers_put(struct zv_hdr *zv)
{
	struct tmem_xhandle xh;
	uint16_t size;
	bool ephemeral;
	int remotenode, ret = -1;
	char *data;
	struct tmem_pool *pool;
	unsigned long flags;
	unsigned char cksum;
	char *p;
	int i;
	unsigned char *tmpmem = __get_cpu_var(zcache_remoteputmem);

	ASSERT_SENTINEL(zv, ZVH);
	BUG_ON(zv->client_id != LOCAL_CLIENT);
	local_bh_disable();
	xh.client_id = zv->client_id;
	xh.pool_id = zv->pool_id;
	xh.oid = zv->oid;
	xh.index = zv->index;
	size = xv_get_object_size(zv) - sizeof(*zv);
	BUG_ON(size == 0 || size > zv_max_page_size);
	data = (char *)zv + sizeof(*zv);
	for (p = data, cksum = 0, i = 0; i < size; i++)
		cksum += *p;
	memcpy(tmpmem, data, size);
	data = tmpmem;
	pool = zcache_get_pool_by_id(zv->client_id, zv->pool_id);
	ephemeral = is_ephemeral(pool);
	zcache_put_pool(pool);
	/* now OK to release lock set in caller */
	spin_unlock(&zcache_rem_op_list_lock);
	local_bh_enable();
	preempt_disable();
	ret = ramster_remote_put(&xh, data, size, ephemeral, &remotenode);
	preempt_enable_no_resched();
	if (ret != 0) {
		/*
		 * This is some form of a memory leak... if the remote put
		 * fails, there will never be another attempt to remotify
		 * this page.  But since we've dropped the zv pointer,
		 * the page may have been freed or the data replaced
		 * so we can't just "put it back" in the remote op list.
		 * Even if we could, not sure where to put it in the list
		 * because there may be flushes that must be strictly
		 * ordered vs the put.  So leave this as a FIXME for now.
		 * But count them so we know if it becomes a problem.
		 */
		ramster_pers_pages_remote_failed++;
		goto out;
	} else
		atomic_inc(&ramster_remote_pers_pages);
	ramster_pers_pages_remoted++;
	/*
	 * data was successfully remoted so change the local version to
	 * point to the remote node where it landed
	 */
	local_bh_disable();
	pool = zcache_get_pool_by_id(LOCAL_CLIENT, xh.pool_id);
	local_irq_save(flags);
	(void)tmem_replace(pool, &xh.oid, xh.index,
			pampd_make_remote(remotenode, size, cksum));
	local_irq_restore(flags);
	zcache_put_pool(pool);
	local_bh_enable();
out:
	return;
}

static void zcache_do_remotify_ops(int nr)
{
	struct ramster_remotify_hdr *rem_op;
	union remotify_list_node *u;

	while (1) {
		if (!nr)
			goto out;
		spin_lock(&zcache_rem_op_list_lock);
		if (list_empty(&zcache_rem_op_list)) {
			spin_unlock(&zcache_rem_op_list_lock);
			goto out;
		}
		rem_op = list_first_entry(&zcache_rem_op_list,
				struct ramster_remotify_hdr, list);
		list_del_init(&rem_op->list);
		if (rem_op->op != RAMSTER_REMOTIFY_PERS_PUT)
			spin_unlock(&zcache_rem_op_list_lock);
		u = (union remotify_list_node *)rem_op;
		switch (rem_op->op) {
		case RAMSTER_REMOTIFY_EPH_PUT:
BUG();
			zcache_remote_eph_put((struct zbud_hdr *)rem_op);
			break;
		case RAMSTER_REMOTIFY_PERS_PUT:
			zcache_remote_pers_put((struct zv_hdr *)rem_op);
			break;
		case RAMSTER_REMOTIFY_FLUSH_PAGE:
			zcache_remote_flush_page((struct flushlist_node *)u);
			break;
		case RAMSTER_REMOTIFY_FLUSH_OBJ:
			zcache_remote_flush_object((struct flushlist_node *)u);
			break;
		default:
			BUG();
		}
	}
out:
	return;
}

/*
 * Communicate interface revision with userspace
 */
#include "cluster/ramster_nodemanager.h"
static unsigned long ramster_interface_revision  = R2NM_API_VERSION;

/*
 * For now, just push over a few pages every few seconds to
 * ensure that it basically works
 */
static struct workqueue_struct *ramster_remotify_workqueue;
static void ramster_remotify_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(ramster_remotify_worker,
		ramster_remotify_process);

static void ramster_remotify_queue_delayed_work(unsigned long delay)
{
	if (!queue_delayed_work(ramster_remotify_workqueue,
				&ramster_remotify_worker, delay))
		pr_err("ramster_remotify: bad workqueue\n");
}


static int use_frontswap;
static int use_cleancache;
static int ramster_remote_target_nodenum = -1;
static void ramster_remotify_process(struct work_struct *work)
{
	static bool remotify_in_progress;

	BUG_ON(irqs_disabled());
	if (remotify_in_progress)
		ramster_remotify_queue_delayed_work(HZ);
	else if (ramster_remote_target_nodenum != -1) {
		remotify_in_progress = true;
#ifdef CONFIG_CLEANCACHE
	if (use_cleancache && ramster_eph_remotify_enable)
		zbud_remotify_pages(5000); /* FIXME is this a good number? */
#endif
#ifdef CONFIG_FRONTSWAP
	if (use_frontswap && ramster_pers_remotify_enable)
		zcache_do_remotify_ops(500); /* FIXME is this a good number? */
#endif
		remotify_in_progress = false;
		ramster_remotify_queue_delayed_work(HZ);
	}
}

static void ramster_remotify_init(void)
{
	unsigned long n = 60UL;
	ramster_remotify_workqueue =
		create_singlethread_workqueue("ramster_remotify");
	ramster_remotify_queue_delayed_work(n * HZ);
}


static void zbud_init(void)
{
	int i;

	INIT_LIST_HEAD(&zbud_buddied_list);
	zcache_zbud_buddied_count = 0;
	for (i = 0; i < NCHUNKS; i++) {
		INIT_LIST_HEAD(&zbud_unbuddied[i].list);
		zbud_unbuddied[i].count = 0;
	}
}

#ifdef CONFIG_SYSFS
/*
 * These sysfs routines show a nice distribution of how many zbpg's are
 * currently (and have ever been placed) in each unbuddied list.  It's fun
 * to watch but can probably go away before final merge.
 */
static int zbud_show_unbuddied_list_counts(char *buf)
{
	int i;
	char *p = buf;

	for (i = 0; i < NCHUNKS; i++)
		p += sprintf(p, "%u ", zbud_unbuddied[i].count);
	return p - buf;
}

static int zbud_show_cumul_chunk_counts(char *buf)
{
	unsigned long i, chunks = 0, total_chunks = 0, sum_total_chunks = 0;
	unsigned long total_chunks_lte_21 = 0, total_chunks_lte_32 = 0;
	unsigned long total_chunks_lte_42 = 0;
	char *p = buf;

	for (i = 0; i < NCHUNKS; i++) {
		p += sprintf(p, "%lu ", zbud_cumul_chunk_counts[i]);
		chunks += zbud_cumul_chunk_counts[i];
		total_chunks += zbud_cumul_chunk_counts[i];
		sum_total_chunks += i * zbud_cumul_chunk_counts[i];
		if (i == 21)
			total_chunks_lte_21 = total_chunks;
		if (i == 32)
			total_chunks_lte_32 = total_chunks;
		if (i == 42)
			total_chunks_lte_42 = total_chunks;
	}
	p += sprintf(p, "<=21:%lu <=32:%lu <=42:%lu, mean:%lu\n",
		total_chunks_lte_21, total_chunks_lte_32, total_chunks_lte_42,
		chunks == 0 ? 0 : sum_total_chunks / chunks);
	return p - buf;
}
#endif

/**********
 * This "zv" PAM implementation combines the TLSF-based xvMalloc
 * with lzo1x compression to maximize the amount of data that can
 * be packed into a physical page.
 *
 * Zv represents a PAM page with the index and object (plus a "size" value
 * necessary for decompression) immediately preceding the compressed data.
 */

/* rudimentary policy limits */
/* total number of persistent pages may not exceed this percentage */
static unsigned int zv_page_count_policy_percent = 75;
/*
 * byte count defining poor compression; pages with greater zsize will be
 * rejected
 */
static unsigned int zv_max_zsize = (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 zv_max_mean_zsize = (PAGE_SIZE / 8) * 5;

static atomic_t zv_curr_dist_counts[NCHUNKS];
static atomic_t zv_cumul_dist_counts[NCHUNKS];


static struct zv_hdr *zv_create(struct zcache_client *cli, uint32_t pool_id,
				struct tmem_oid *oid, uint32_t index,
				void *cdata, unsigned clen)
{
	struct page *page;
	struct zv_hdr *zv = NULL;
	uint32_t offset;
	int alloc_size = clen + sizeof(struct zv_hdr);
	int chunks = (alloc_size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;
	int ret;

	BUG_ON(!irqs_disabled());
	BUG_ON(chunks >= NCHUNKS);
	ret = xv_malloc(cli->xvpool, clen + sizeof(struct zv_hdr),
			&page, &offset, ZCACHE_GFP_MASK);
	if (unlikely(ret))
		goto out;
	atomic_inc(&zv_curr_dist_counts[chunks]);
	atomic_inc(&zv_cumul_dist_counts[chunks]);
	zv = kmap_atomic(page) + offset;
	zv->index = index;
	zv->oid = *oid;
	zv->pool_id = pool_id;
	SET_SENTINEL(zv, ZVH);
	INIT_LIST_HEAD(&zv->rem_op.list);
	zv->client_id = get_client_id_from_client(cli);
	zv->rem_op.op = RAMSTER_REMOTIFY_PERS_PUT;
	if (zv->client_id == LOCAL_CLIENT) {
		spin_lock(&zcache_rem_op_list_lock);
		list_add_tail(&zv->rem_op.list, &zcache_rem_op_list);
		spin_unlock(&zcache_rem_op_list_lock);
	}
	memcpy((char *)zv + sizeof(struct zv_hdr), cdata, clen);
	kunmap_atomic(zv);
out:
	return zv;
}

/* similar to zv_create, but just reserve space, no data yet */
static struct zv_hdr *zv_alloc(struct tmem_pool *pool,
				struct tmem_oid *oid, uint32_t index,
				unsigned clen)
{
	struct zcache_client *cli = pool->client;
	struct page *page;
	struct zv_hdr *zv = NULL;
	uint32_t offset;
	int ret;

	BUG_ON(!irqs_disabled());
	BUG_ON(!is_local_client(pool->client));
	ret = xv_malloc(cli->xvpool, clen + sizeof(struct zv_hdr),
			&page, &offset, ZCACHE_GFP_MASK);
	if (unlikely(ret))
		goto out;
	zv = kmap_atomic(page) + offset;
	SET_SENTINEL(zv, ZVH);
	INIT_LIST_HEAD(&zv->rem_op.list);
	zv->client_id = LOCAL_CLIENT;
	zv->rem_op.op = RAMSTER_INTRANSIT_PERS;
	zv->index = index;
	zv->oid = *oid;
	zv->pool_id = pool->pool_id;
	kunmap_atomic(zv);
out:
	return zv;
}

static void zv_free(struct xv_pool *xvpool, struct zv_hdr *zv)
{
	unsigned long flags;
	struct page *page;
	uint32_t offset;
	uint16_t size = xv_get_object_size(zv);
	int chunks = (size + (CHUNK_SIZE - 1)) >> CHUNK_SHIFT;

	ASSERT_SENTINEL(zv, ZVH);
	BUG_ON(chunks >= NCHUNKS);
	atomic_dec(&zv_curr_dist_counts[chunks]);
	size -= sizeof(*zv);
	spin_lock(&zcache_rem_op_list_lock);
	size = xv_get_object_size(zv) - sizeof(*zv);
	BUG_ON(size == 0);
	INVERT_SENTINEL(zv, ZVH);
	if (!list_empty(&zv->rem_op.list))
		list_del_init(&zv->rem_op.list);
	spin_unlock(&zcache_rem_op_list_lock);
	page = virt_to_page(zv);
	offset = (unsigned long)zv & ~PAGE_MASK;
	local_irq_save(flags);
	xv_free(xvpool, page, offset);
	local_irq_restore(flags);
}

static void zv_decompress(struct page *page, struct zv_hdr *zv)
{
	size_t clen = PAGE_SIZE;
	char *to_va;
	unsigned size;
	int ret;

	ASSERT_SENTINEL(zv, ZVH);
	size = xv_get_object_size(zv) - sizeof(*zv);
	BUG_ON(size == 0);
	to_va = kmap_atomic(page);
	ret = lzo1x_decompress_safe((char *)zv + sizeof(*zv),
					size, to_va, &clen);
	kunmap_atomic(to_va);
	BUG_ON(ret != LZO_E_OK);
	BUG_ON(clen != PAGE_SIZE);
}

static void zv_copy_from_pampd(char *data, size_t *bufsize, struct zv_hdr *zv)
{
	unsigned size;

	ASSERT_SENTINEL(zv, ZVH);
	size = xv_get_object_size(zv) - sizeof(*zv);
	BUG_ON(size == 0 || size > zv_max_page_size);
	BUG_ON(size > *bufsize);
	memcpy(data, (char *)zv + sizeof(*zv), size);
	*bufsize = size;
}

static void zv_copy_to_pampd(struct zv_hdr *zv, char *data, size_t size)
{
	unsigned zv_size;

	ASSERT_SENTINEL(zv, ZVH);
	zv_size = xv_get_object_size(zv) - sizeof(*zv);
	BUG_ON(zv_size != size);
	BUG_ON(zv_size == 0 || zv_size > zv_max_page_size);
	memcpy((char *)zv + sizeof(*zv), data, size);
}

#ifdef CONFIG_SYSFS
/*
 * show a distribution of compression stats for zv pages.
 */

static int zv_curr_dist_counts_show(char *buf)
{
	unsigned long i, n, chunks = 0, sum_total_chunks = 0;
	char *p = buf;

	for (i = 0; i < NCHUNKS; i++) {
		n = atomic_read(&zv_curr_dist_counts[i]);
		p += sprintf(p, "%lu ", n);
		chunks += n;
		sum_total_chunks += i * n;
	}
	p += sprintf(p, "mean:%lu\n",
		chunks == 0 ? 0 : sum_total_chunks / chunks);
	return p - buf;
}

static int zv_cumul_dist_counts_show(char *buf)
{
	unsigned long i, n, chunks = 0, sum_total_chunks = 0;
	char *p = buf;

	for (i = 0; i < NCHUNKS; i++) {
		n = atomic_read(&zv_cumul_dist_counts[i]);
		p += sprintf(p, "%lu ", n);
		chunks += n;
		sum_total_chunks += i * n;
	}
	p += sprintf(p, "mean:%lu\n",
		chunks == 0 ? 0 : sum_total_chunks / chunks);
	return p - buf;
}

/*
 * setting zv_max_zsize via sysfs causes all persistent (e.g. swap)
 * pages that don't compress to less than this value (including metadata
 * overhead) to be rejected.  We don't allow the value to get too close
 * to PAGE_SIZE.
 */
static ssize_t zv_max_zsize_show(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    char *buf)
{
	return sprintf(buf, "%u\n", zv_max_zsize);
}

static ssize_t zv_max_zsize_store(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    const char *buf, size_t count)
{
	unsigned long val;
	int err;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	err = kstrtoul(buf, 10, &val);
	if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7))
		return -EINVAL;
	zv_max_zsize = val;
	return count;
}

/*
 * setting zv_max_mean_zsize via sysfs causes all persistent (e.g. swap)
 * pages that don't compress to less than this value (including metadata
 * overhead) to be rejected UNLESS the mean compression is also smaller
 * than this value.  In other words, we are load-balancing-by-zsize the
 * accepted pages.  Again, we don't allow the value to get too close
 * to PAGE_SIZE.
 */
static ssize_t zv_max_mean_zsize_show(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    char *buf)
{
	return sprintf(buf, "%u\n", zv_max_mean_zsize);
}

static ssize_t zv_max_mean_zsize_store(struct kobject *kobj,
				    struct kobj_attribute *attr,
				    const char *buf, size_t count)
{
	unsigned long val;
	int err;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	err = kstrtoul(buf, 10, &val);
	if (err || (val == 0) || (val > (PAGE_SIZE / 8) * 7))
		return -EINVAL;
	zv_max_mean_zsize = val;
	return count;
}

/*
 * setting zv_page_count_policy_percent via sysfs sets an upper bound of
 * persistent (e.g. swap) pages that will be retained according to:
 *     (zv_page_count_policy_percent * totalram_pages) / 100)
 * when that limit is reached, further puts will be rejected (until
 * some pages have been flushed).  Note that, due to compression,
 * this number may exceed 100; it defaults to 75 and we set an
 * arbitary limit of 150.  A poor choice will almost certainly result
 * in OOM's, so this value should only be changed prudently.
 */
static ssize_t zv_page_count_policy_percent_show(struct kobject *kobj,
						 struct kobj_attribute *attr,
						 char *buf)
{
	return sprintf(buf, "%u\n", zv_page_count_policy_percent);
}

static ssize_t zv_page_count_policy_percent_store(struct kobject *kobj,
						  struct kobj_attribute *attr,
						  const char *buf, size_t count)
{
	unsigned long val;
	int err;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	err = kstrtoul(buf, 10, &val);
	if (err || (val == 0) || (val > 150))
		return -EINVAL;
	zv_page_count_policy_percent = val;
	return count;
}

static struct kobj_attribute zcache_zv_max_zsize_attr = {
		.attr = { .name = "zv_max_zsize", .mode = 0644 },
		.show = zv_max_zsize_show,
		.store = zv_max_zsize_store,
};

static struct kobj_attribute zcache_zv_max_mean_zsize_attr = {
		.attr = { .name = "zv_max_mean_zsize", .mode = 0644 },
		.show = zv_max_mean_zsize_show,
		.store = zv_max_mean_zsize_store,
};

static struct kobj_attribute zcache_zv_page_count_policy_percent_attr = {
		.attr = { .name = "zv_page_count_policy_percent",
			  .mode = 0644 },
		.show = zv_page_count_policy_percent_show,
		.store = zv_page_count_policy_percent_store,
};
#endif

/*
 * zcache core code starts here
 */

/* useful stats not collected by cleancache or frontswap */
static unsigned long zcache_flush_total;
static unsigned long zcache_flush_found;
static unsigned long zcache_flobj_total;
static unsigned long zcache_flobj_found;
static unsigned long zcache_failed_eph_puts;
static unsigned long zcache_nonactive_puts;
static unsigned long zcache_failed_pers_puts;

/*
 * 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.
 */
static 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;

	if (cli_id == LOCAL_CLIENT)
		cli = &zcache_host;
	else {
		if (cli_id >= MAX_CLIENTS)
			goto out;
		cli = &zcache_clients[cli_id];
		if (cli == NULL)
			goto out;
		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;
}

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

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

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

	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;
	if (cli->allocated)
		goto out;
	cli->allocated = 1;
#ifdef CONFIG_FRONTSWAP
	cli->xvpool = xv_create_pool();
	if (cli->xvpool == NULL)
		goto out;
#endif
	ret = 0;
out:
	return ret;
}

/* counters for debugging */
static unsigned long zcache_failed_get_free_pages;
static unsigned long zcache_failed_alloc;
static unsigned long zcache_put_to_flush;

/*
 * 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 struct kmem_cache *ramster_flnode_cache;
static atomic_t zcache_curr_obj_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_obj_count_max;
static atomic_t zcache_curr_objnode_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_objnode_count_max;

/*
 * to avoid memory allocation recursion (e.g. due to direct reclaim), we
 * preload all necessary data structures so the hostops callbacks never
 * actually do a malloc
 */
struct zcache_preload {
	void *page;
	struct tmem_obj *obj;
	int nr;
	struct tmem_objnode *objnodes[OBJNODE_TREE_MAX_PATH];
	struct flushlist_node *flnode;
};
static DEFINE_PER_CPU(struct zcache_preload, zcache_preloads) = { 0, };

static int zcache_do_preload(struct tmem_pool *pool)
{
	struct zcache_preload *kp;
	struct tmem_objnode *objnode;
	struct tmem_obj *obj;
	struct flushlist_node *flnode;
	void *page;
	int ret = -ENOMEM;

	if (unlikely(zcache_objnode_cache == NULL))
		goto out;
	if (unlikely(zcache_obj_cache == NULL))
		goto out;
	preempt_disable();
	kp = &__get_cpu_var(zcache_preloads);
	while (kp->nr < ARRAY_SIZE(kp->objnodes)) {
		preempt_enable_no_resched();
		objnode = kmem_cache_alloc(zcache_objnode_cache,
				ZCACHE_GFP_MASK);
		if (unlikely(objnode == NULL)) {
			zcache_failed_alloc++;
			goto out;
		}
		preempt_disable();
		kp = &__get_cpu_var(zcache_preloads);
		if (kp->nr < ARRAY_SIZE(kp->objnodes))
			kp->objnodes[kp->nr++] = objnode;
		else
			kmem_cache_free(zcache_objnode_cache, objnode);
	}
	preempt_enable_no_resched();
	obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK);
	if (unlikely(obj == NULL)) {
		zcache_failed_alloc++;
		goto out;
	}
	flnode = kmem_cache_alloc(ramster_flnode_cache, ZCACHE_GFP_MASK);
	if (unlikely(flnode == NULL)) {
		zcache_failed_alloc++;
		goto out;
	}
	if (is_ephemeral(pool)) {
		page = (void *)__get_free_page(ZCACHE_GFP_MASK);
		if (unlikely(page == NULL)) {
			zcache_failed_get_free_pages++;
			kmem_cache_free(zcache_obj_cache, obj);
			kmem_cache_free(ramster_flnode_cache, flnode);
			goto out;
		}
	}
	preempt_disable();
	kp = &__get_cpu_var(zcache_preloads);
	if (kp->obj == NULL)
		kp->obj = obj;
	else
		kmem_cache_free(zcache_obj_cache, obj);
	if (kp->flnode == NULL)
		kp->flnode = flnode;
	else
		kmem_cache_free(ramster_flnode_cache, flnode);
	if (is_ephemeral(pool)) {
		if (kp->page == NULL)
			kp->page = page;
		else
			free_page((unsigned long)page);
	}
	ret = 0;
out:
	return ret;
}

static int ramster_do_preload_flnode_only(struct tmem_pool *pool)
{
	struct zcache_preload *kp;
	struct flushlist_node *flnode;
	int ret = -ENOMEM;

	BUG_ON(!irqs_disabled());
	if (unlikely(ramster_flnode_cache == NULL))
		BUG();
	kp = &__get_cpu_var(zcache_preloads);
	flnode = kmem_cache_alloc(ramster_flnode_cache, GFP_ATOMIC);
	if (unlikely(flnode == NULL) && kp->flnode == NULL)
		BUG();  /* FIXME handle more gracefully, but how??? */
	else if (kp->flnode == NULL)
		kp->flnode = flnode;
	else
		kmem_cache_free(ramster_flnode_cache, flnode);
	return ret;
}

static void *zcache_get_free_page(void)
{
	struct zcache_preload *kp;
	void *page;

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

static void zcache_free_page(void *p)
{
	free_page((unsigned long)p);
}

/*
 * zcache implementation for tmem host ops
 */

static struct tmem_objnode *zcache_objnode_alloc(struct tmem_pool *pool)
{
	struct tmem_objnode *objnode = NULL;
	unsigned long count;
	struct zcache_preload *kp;

	kp = &__get_cpu_var(zcache_preloads);
	if (kp->nr <= 0)
		goto out;
	objnode = kp->objnodes[kp->nr - 1];
	BUG_ON(objnode == NULL);
	kp->objnodes[kp->nr - 1] = NULL;
	kp->nr--;
	count = atomic_inc_return(&zcache_curr_objnode_count);
	if (count > zcache_curr_objnode_count_max)
		zcache_curr_objnode_count_max = count;
out:
	return objnode;
}

static void zcache_objnode_free(struct tmem_objnode *objnode,
					struct tmem_pool *pool)
{
	atomic_dec(&zcache_curr_objnode_count);
	BUG_ON(atomic_read(&zcache_curr_objnode_count) < 0);
	kmem_cache_free(zcache_objnode_cache, objnode);
}

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

	kp = &__get_cpu_var(zcache_preloads);
	obj = kp->obj;
	BUG_ON(obj == NULL);
	kp->obj = NULL;
	count = atomic_inc_return(&zcache_curr_obj_count);
	if (count > zcache_curr_obj_count_max)
		zcache_curr_obj_count_max = count;
	return obj;
}

static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
{
	atomic_dec(&zcache_curr_obj_count);
	BUG_ON(atomic_read(&zcache_curr_obj_count) < 0);
	kmem_cache_free(zcache_obj_cache, obj);
}

static struct flushlist_node *ramster_flnode_alloc(struct tmem_pool *pool)
{
	struct flushlist_node *flnode = NULL;
	struct zcache_preload *kp;
	int count;

	kp = &__get_cpu_var(zcache_preloads);
	flnode = kp->flnode;
	BUG_ON(flnode == NULL);
	kp->flnode = NULL;
	count = atomic_inc_return(&ramster_curr_flnode_count);
	if (count > ramster_curr_flnode_count_max)
		ramster_curr_flnode_count_max = count;
	return flnode;
}

static void ramster_flnode_free(struct flushlist_node *flnode,
				struct tmem_pool *pool)
{
	atomic_dec(&ramster_curr_flnode_count);
	BUG_ON(atomic_read(&ramster_curr_flnode_count) < 0);
	kmem_cache_free(ramster_flnode_cache, flnode);
}

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,
};

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


static inline void dec_and_check(atomic_t *pvar)
{
	atomic_dec(pvar);
	/* later when all accounting is fixed, make this a BUG */
	WARN_ON_ONCE(atomic_read(pvar) < 0);
}

static atomic_t zcache_curr_eph_pampd_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_eph_pampd_count_max;
static atomic_t zcache_curr_pers_pampd_count = ATOMIC_INIT(0);
static unsigned long zcache_curr_pers_pampd_count_max;

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

static int zcache_pampd_eph_create(char *data, size_t size, bool raw,
				struct tmem_pool *pool, struct tmem_oid *oid,
				uint32_t index, void **pampd)
{
	int ret = -1;
	void *cdata = data;
	size_t clen = size;
	struct zcache_client *cli = pool->client;
	uint16_t client_id = get_client_id_from_client(cli);
	struct page *page = NULL;
	unsigned long count;

	if (!raw) {
		page = virt_to_page(data);
		ret = zcache_compress(page, &cdata, &clen);
		if (ret == 0)
			goto out;
		if (clen == 0 || clen > zbud_max_buddy_size()) {
			zcache_compress_poor++;
			goto out;
		}
	}
	*pampd = (void *)zbud_create(client_id, pool->pool_id, oid,
					index, page, cdata, clen);
	if (*pampd == NULL) {
		ret = -ENOMEM;
		goto out;
	}
	ret = 0;
	count = atomic_inc_return(&zcache_curr_eph_pampd_count);
	if (count > zcache_curr_eph_pampd_count_max)
		zcache_curr_eph_pampd_count_max = count;
	if (client_id != LOCAL_CLIENT) {
		count = atomic_inc_return(&ramster_foreign_eph_pampd_count);
		if (count > ramster_foreign_eph_pampd_count_max)
			ramster_foreign_eph_pampd_count_max = count;
	}
out:
	return ret;
}

static int zcache_pampd_pers_create(char *data, size_t size, bool raw,
				struct tmem_pool *pool, struct tmem_oid *oid,
				uint32_t index, void **pampd)
{
	int ret = -1;
	void *cdata = data;
	size_t clen = size;
	struct zcache_client *cli = pool->client;
	struct page *page;
	unsigned long count;
	unsigned long zv_mean_zsize;
	struct zv_hdr *zv;
	long curr_pers_pampd_count;
	u64 total_zsize;
#ifdef RAMSTER_TESTING
	static bool pampd_neg_warned;
#endif

	curr_pers_pampd_count = atomic_read(&zcache_curr_pers_pampd_count) -
			atomic_read(&ramster_remote_pers_pages);
#ifdef RAMSTER_TESTING
	/* should always be positive, but warn if accounting is off */
	if (!pampd_neg_warned) {
		pr_warn("ramster: bad accounting for curr_pers_pampd_count\n");
		pampd_neg_warned = true;
	}
#endif
	if (curr_pers_pampd_count >
		    (zv_page_count_policy_percent * totalram_pages) / 100) {
		zcache_policy_percent_exceeded++;
		goto out;
	}
	if (raw)
		goto ok_to_create;
	page = virt_to_page(data);
	if (zcache_compress(page, &cdata, &clen) == 0)
		goto out;
	/* reject if compression is too poor */
	if (clen > zv_max_zsize) {
		zcache_compress_poor++;
		goto out;
	}
	/* reject if mean compression is too poor */
	if ((clen > zv_max_mean_zsize) && (curr_pers_pampd_count > 0)) {
		total_zsize = xv_get_total_size_bytes(cli->xvpool);
		zv_mean_zsize = div_u64(total_zsize, curr_pers_pampd_count);
		if (zv_mean_zsize > zv_max_mean_zsize) {
			zcache_mean_compress_poor++;
			goto out;
		}
	}
ok_to_create:
	*pampd = (void *)zv_create(cli, pool->pool_id, oid, index, cdata, clen);
	if (*pampd == NULL) {
		ret = -ENOMEM;
		goto out;
	}
	ret = 0;
	count = atomic_inc_return(&zcache_curr_pers_pampd_count);
	if (count > zcache_curr_pers_pampd_count_max)
		zcache_curr_pers_pampd_count_max = count;
	if (is_local_client(cli))
		goto out;
	zv = *(struct zv_hdr **)pampd;
	count = atomic_inc_return(&ramster_foreign_pers_pampd_count);
	if (count > ramster_foreign_pers_pampd_count_max)
		ramster_foreign_pers_pampd_count_max = count;
out:
	return ret;
}

static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph,
				struct tmem_pool *pool, struct tmem_oid *oid,
				uint32_t index)
{
	void *pampd = NULL;
	int ret;
	bool ephemeral;

	BUG_ON(preemptible());
	ephemeral = (eph == 1) || ((eph == 0) && is_ephemeral(pool));
	if (ephemeral)
		ret = zcache_pampd_eph_create(data, size, raw, pool,
						oid, index, &pampd);
	else
		ret = zcache_pampd_pers_create(data, size, raw, pool,
						oid, index, &pampd);
	/* FIXME add some counters here for failed creates? */
	return pampd;
}

/*
 * 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 *bufsize, bool raw,
					void *pampd, struct tmem_pool *pool,
					struct tmem_oid *oid, uint32_t index)
{
	int ret = 0;

	BUG_ON(preemptible());
	BUG_ON(is_ephemeral(pool)); /* Fix later for shared pools? */
	BUG_ON(pampd_is_remote(pampd));
	if (raw)
		zv_copy_from_pampd(data, bufsize, pampd);
	else
		zv_decompress(virt_to_page(data), pampd);
	return ret;
}

static int zcache_pampd_get_data_and_free(char *data, size_t *bufsize, bool raw,
					void *pampd, struct tmem_pool *pool,
					struct tmem_oid *oid, uint32_t index)
{
	int ret = 0;
	unsigned long flags;
	struct zcache_client *cli = pool->client;

	BUG_ON(preemptible());
	BUG_ON(pampd_is_remote(pampd));
	if (is_ephemeral(pool)) {
		local_irq_save(flags);
		if (raw)
			zbud_copy_from_pampd(data, bufsize, pampd);
		else
			ret = zbud_decompress(virt_to_page(data), pampd);
		zbud_free_and_delist((struct zbud_hdr *)pampd);
		local_irq_restore(flags);
		if (!is_local_client(cli))
			dec_and_check(&ramster_foreign_eph_pampd_count);
		dec_and_check(&zcache_curr_eph_pampd_count);
	} else {
		if (is_local_client(cli))
			BUG();
		if (raw)
			zv_copy_from_pampd(data, bufsize, pampd);
		else
			zv_decompress(virt_to_page(data), pampd);
		zv_free(cli->xvpool, pampd);
		if (!is_local_client(cli))
			dec_and_check(&ramster_foreign_pers_pampd_count);
		dec_and_check(&zcache_curr_pers_pampd_count);
		ret = 0;
	}
	return ret;
}

static bool zcache_pampd_is_remote(void *pampd)
{
	return pampd_is_remote(pampd);
}

/*
 * 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 zcache_client *cli = pool->client;
	bool eph = is_ephemeral(pool);
	struct zv_hdr *zv;

	BUG_ON(preemptible());
	if (pampd_is_remote(pampd)) {
		WARN_ON(acct == false);
		if (oid == NULL) {
			/*
			 * a NULL oid means to ignore this pampd free
			 * as the remote freeing will be handled elsewhere
			 */
		} else if (eph) {
			/* FIXME remote flush optional but probably good idea */
			/* FIXME get these working properly again */
			dec_and_check(&zcache_curr_eph_pampd_count);
		} else if (pampd_is_intransit(pampd)) {
			/* did a pers remote get_and_free, so just free local */
			pampd = pampd_mask_intransit_and_remote(pampd);
			goto local_pers;
		} else {
			struct flushlist_node *flnode =
				ramster_flnode_alloc(pool);

			flnode->xh.client_id = pampd_remote_node(pampd);
			flnode->xh.pool_id = pool->pool_id;
			flnode->xh.oid = *oid;
			flnode->xh.index = index;
			flnode->rem_op.op = RAMSTER_REMOTIFY_FLUSH_PAGE;
			spin_lock(&zcache_rem_op_list_lock);
			list_add(&flnode->rem_op.list, &zcache_rem_op_list);
			spin_unlock(&zcache_rem_op_list_lock);
			dec_and_check(&zcache_curr_pers_pampd_count);
			dec_and_check(&ramster_remote_pers_pages);
		}
	} else if (eph) {
		zbud_free_and_delist((struct zbud_hdr *)pampd);
		if (!is_local_client(pool->client))
			dec_and_check(&ramster_foreign_eph_pampd_count);
		if (acct)
			/* FIXME get these working properly again */
			dec_and_check(&zcache_curr_eph_pampd_count);
	} else {
local_pers:
		zv = (struct zv_hdr *)pampd;
		if (!is_local_client(pool->client))
			dec_and_check(&ramster_foreign_pers_pampd_count);
		zv_free(cli->xvpool, zv);
		if (acct)
			/* FIXME get these working properly again */
			dec_and_check(&zcache_curr_pers_pampd_count);
	}
}

static void zcache_pampd_free_obj(struct tmem_pool *pool,
					struct tmem_obj *obj)
{
	struct flushlist_node *flnode;

	BUG_ON(preemptible());
	if (obj->extra == NULL)
		return;
	BUG_ON(!pampd_is_remote(obj->extra));
	flnode = ramster_flnode_alloc(pool);
	flnode->xh.client_id = pampd_remote_node(obj->extra);
	flnode->xh.pool_id = pool->pool_id;
	flnode->xh.oid = obj->oid;
	flnode->xh.index = FLUSH_ENTIRE_OBJECT;
	flnode->rem_op.op = RAMSTER_REMOTIFY_FLUSH_OBJ;
	spin_lock(&zcache_rem_op_list_lock);
	list_add(&flnode->rem_op.list, &zcache_rem_op_list);
	spin_unlock(&zcache_rem_op_list_lock);
}

void zcache_pampd_new_obj(struct tmem_obj *obj)
{
	obj->extra = NULL;
}

int zcache_pampd_replace_in_obj(void *new_pampd, struct tmem_obj *obj)
{
	int ret = -1;

	if (new_pampd != NULL) {
		if (obj->extra == NULL)
			obj->extra = new_pampd;
		/* enforce that all remote pages in an object reside
		 * in the same node! */
		else if (pampd_remote_node(new_pampd) !=
				pampd_remote_node((void *)(obj->extra)))
			BUG();
		ret = 0;
	}
	return ret;
}

/*
 * Called by the message handler after a (still compressed) page has been
 * fetched from the remote machine in response to an "is_remote" tmem_get
 * or persistent tmem_localify.  For a tmem_get, "extra" is the address of
 * the page that is to be filled to succesfully resolve the tmem_get; for
 * a (persistent) tmem_localify, "extra" is NULL (as the data is placed only
 * in the local zcache).  "data" points to "size" bytes of (compressed) data
 * passed in the message.  In the case of a persistent remote get, if
 * pre-allocation was successful (see zcache_repatriate_preload), the page
 * is placed into both local zcache and at "extra".
 */
int zcache_localify(int pool_id, struct tmem_oid *oidp,
			uint32_t index, char *data, size_t size,
			void *extra)
{
	int ret = -ENOENT;
	unsigned long flags;
	struct tmem_pool *pool;
	bool ephemeral, delete = false;
	size_t clen = PAGE_SIZE;
	void *pampd, *saved_hb;
	struct tmem_obj *obj;

	pool = zcache_get_pool_by_id(LOCAL_CLIENT, pool_id);
	if (unlikely(pool == NULL))
		/* pool doesn't exist anymore */
		goto out;
	ephemeral = is_ephemeral(pool);
	local_irq_save(flags);  /* FIXME: maybe only disable softirqs? */
	pampd = tmem_localify_get_pampd(pool, oidp, index, &obj, &saved_hb);
	if (pampd == NULL) {
		/* hmmm... must have been a flush while waiting */
#ifdef RAMSTER_TESTING
		pr_err("UNTESTED pampd==NULL in zcache_localify\n");
#endif
		if (ephemeral)
			ramster_remote_eph_pages_unsucc_get++;
		else
			ramster_remote_pers_pages_unsucc_get++;
		obj = NULL;
		goto finish;
	} else if (unlikely(!pampd_is_remote(pampd))) {
		/* hmmm... must have been a dup put while waiting */
#ifdef RAMSTER_TESTING
		pr_err("UNTESTED dup while waiting in zcache_localify\n");
#endif
		if (ephemeral)
			ramster_remote_eph_pages_unsucc_get++;
		else
			ramster_remote_pers_pages_unsucc_get++;
		obj = NULL;
		pampd = NULL;
		ret = -EEXIST;
		goto finish;
	} else if (size == 0) {
		/* no remote data, delete the local is_remote pampd */
		pampd = NULL;
		if (ephemeral)
			ramster_remote_eph_pages_unsucc_get++;
		else
			BUG();
		delete = true;
		goto finish;
	}
	if (!ephemeral && pampd_is_intransit(pampd)) {
		/* localify to zcache */
		pampd = pampd_mask_intransit_and_remote(pampd);
		zv_copy_to_pampd(pampd, data, size);
	} else {
		pampd = NULL;
		obj = NULL;
	}
	if (extra != NULL) {
		/* decompress direct-to-memory to complete remotify */
		ret = lzo1x_decompress_safe((char *)data, size,
						(char *)extra, &clen);
		BUG_ON(ret != LZO_E_OK);
		BUG_ON(clen != PAGE_SIZE);
	}
	if (ephemeral)
		ramster_remote_eph_pages_succ_get++;
	else
		ramster_remote_pers_pages_succ_get++;
	ret = 0;
finish:
	tmem_localify_finish(obj, index, pampd, saved_hb, delete);
	zcache_put_pool(pool);
	local_irq_restore(flags);
out:
	return ret;
}

/*
 * Called on a remote persistent tmem_get to attempt to preallocate
 * local storage for the data contained in the remote persistent page.
 * If succesfully preallocated, returns the pampd, marked as remote and
 * in_transit.  Else returns NULL.  Note that the appropriate tmem data
 * structure must be locked.
 */
static void *zcache_pampd_repatriate_preload(void *pampd,
						struct tmem_pool *pool,
						struct tmem_oid *oid,
						uint32_t index,
						bool *intransit)
{
	int clen = pampd_remote_size(pampd);
	void *ret_pampd = NULL;
	unsigned long flags;

	if (!pampd_is_remote(pampd))
		BUG();
	if (is_ephemeral(pool))
		BUG();
	if (pampd_is_intransit(pampd)) {
		/*
		 * to avoid multiple allocations (and maybe a memory leak)
		 * don't preallocate if already in the process of being
		 * repatriated
		 */
		*intransit = true;
		goto out;
	}
	*intransit = false;
	local_irq_save(flags);
	ret_pampd = (void *)zv_alloc(pool, oid, index, clen);
	if (ret_pampd != NULL) {
		/*
		 *  a pampd is marked intransit if it is remote and space has
		 *  been allocated for it locally (note, only happens for
		 *  persistent pages, in which case the remote copy is freed)
		 */
		ret_pampd = pampd_mark_intransit(ret_pampd);
		dec_and_check(&ramster_remote_pers_pages);
	} else
		ramster_pers_pages_remote_nomem++;
	local_irq_restore(flags);
out:
	return ret_pampd;
}

/*
 * Called on a remote tmem_get to invoke a message to fetch the page.
 * Might sleep so no tmem locks can be held.  "extra" is passed
 * all the way through the round-trip messaging to zcache_localify.
 */
static int zcache_pampd_repatriate(void *fake_pampd, void *real_pampd,
				   struct tmem_pool *pool,
				   struct tmem_oid *oid, uint32_t index,
				   bool free, void *extra)
{
	struct tmem_xhandle xh;
	int ret;

	if (pampd_is_intransit(real_pampd))
		/* have local space pre-reserved, so free remote copy */
		free = true;
	xh = tmem_xhandle_fill(LOCAL_CLIENT, pool, oid, index);
	/* unreliable request/response for now */
	ret = ramster_remote_async_get(&xh, free,
					pampd_remote_node(fake_pampd),
					pampd_remote_size(fake_pampd),
					pampd_remote_cksum(fake_pampd),
					extra);
#ifdef RAMSTER_TESTING
	if (ret != 0 && ret != -ENOENT)
		pr_err("TESTING zcache_pampd_repatriate returns, ret=%d\n",
			ret);
#endif
	return ret;
}

static struct tmem_pamops zcache_pamops = {
	.create = zcache_pampd_create,
	.get_data = zcache_pampd_get_data,
	.free = zcache_pampd_free,
	.get_data_and_free = zcache_pampd_get_data_and_free,
	.free_obj = zcache_pampd_free_obj,
	.is_remote = zcache_pampd_is_remote,
	.repatriate_preload = zcache_pampd_repatriate_preload,
	.repatriate = zcache_pampd_repatriate,
	.new_obj = zcache_pampd_new_obj,
	.replace_in_obj = zcache_pampd_replace_in_obj,
};

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

#define LZO_WORKMEM_BYTES LZO1X_1_MEM_COMPRESS
#define LZO_DSTMEM_PAGE_ORDER 1
static DEFINE_PER_CPU(unsigned char *, zcache_workmem);
static DEFINE_PER_CPU(unsigned char *, zcache_dstmem);

static int zcache_compress(struct page *from, void **out_va, size_t *out_len)
{
	int ret = 0;
	unsigned char *dmem = __get_cpu_var(zcache_dstmem);
	unsigned char *wmem = __get_cpu_var(zcache_workmem);
	char *from_va;

	BUG_ON(!irqs_disabled());
	if (unlikely(dmem == NULL || wmem == NULL))
		goto out;  /* no buffer, so can't compress */
	from_va = kmap_atomic(from);
	mb();
	ret = lzo1x_1_compress(from_va, PAGE_SIZE, dmem, out_len, wmem);
	BUG_ON(ret != LZO_E_OK);
	*out_va = dmem;
	kunmap_atomic(from_va);
	ret = 1;
out:
	return ret;
}


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

	switch (action) {
	case CPU_UP_PREPARE:
		per_cpu(zcache_dstmem, cpu) = (void *)__get_free_pages(
			GFP_KERNEL | __GFP_REPEAT,
			LZO_DSTMEM_PAGE_ORDER),
		per_cpu(zcache_workmem, cpu) =
			kzalloc(LZO1X_MEM_COMPRESS,
				GFP_KERNEL | __GFP_REPEAT);
		per_cpu(zcache_remoteputmem, cpu) =
			kzalloc(PAGE_SIZE, GFP_KERNEL | __GFP_REPEAT);
		break;
	case CPU_DEAD:
	case CPU_UP_CANCELED:
		kfree(per_cpu(zcache_remoteputmem, cpu));
		per_cpu(zcache_remoteputmem, cpu) = NULL;
		free_pages((unsigned long)per_cpu(zcache_dstmem, cpu),
				LZO_DSTMEM_PAGE_ORDER);
		per_cpu(zcache_dstmem, cpu) = NULL;
		kfree(per_cpu(zcache_workmem, cpu));
		per_cpu(zcache_workmem, cpu) = NULL;
		kp = &per_cpu(zcache_preloads, cpu);
		while (kp->nr) {
			kmem_cache_free(zcache_objnode_cache,
					kp->objnodes[kp->nr - 1]);
			kp->objnodes[kp->nr - 1] = NULL;
			kp->nr--;
		}
		if (kp->obj) {
			kmem_cache_free(zcache_obj_cache, kp->obj);
			kp->obj = NULL;
		}
		if (kp->flnode) {
			kmem_cache_free(ramster_flnode_cache, kp->flnode);
			kp->flnode = NULL;
		}
		if (kp->page) {
			free_page((unsigned long)kp->page);
			kp->page = NULL;
		}
		break;
	default:
		break;
	}
	return NOTIFY_OK;
}

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

#ifdef CONFIG_SYSFS
#define ZCACHE_SYSFS_RO(_name) \
	static ssize_t zcache_##_name##_show(struct kobject *kobj, \
				struct kobj_attribute *attr, char *buf) \
	{ \
		return sprintf(buf, "%lu\n", zcache_##_name); \
	} \
	static struct kobj_attribute zcache_##_name##_attr = { \
		.attr = { .name = __stringify(_name), .mode = 0444 }, \
		.show = zcache_##_name##_show, \
	}

#define ZCACHE_SYSFS_RO_ATOMIC(_name) \
	static ssize_t zcache_##_name##_show(struct kobject *kobj, \
				struct kobj_attribute *attr, char *buf) \
	{ \
	    return sprintf(buf, "%d\n", atomic_read(&zcache_##_name)); \
	} \
	static struct kobj_attribute zcache_##_name##_attr = { \
		.attr = { .name = __stringify(_name), .mode = 0444 }, \
		.show = zcache_##_name##_show, \
	}

#define ZCACHE_SYSFS_RO_CUSTOM(_name, _func) \
	static ssize_t zcache_##_name##_show(struct kobject *kobj, \
				struct kobj_attribute *attr, char *buf) \
	{ \
	    return _func(buf); \
	} \
	static struct kobj_attribute zcache_##_name##_attr = { \
		.attr = { .name = __stringify(_name), .mode = 0444 }, \
		.show = zcache_##_name##_show, \
	}

ZCACHE_SYSFS_RO(curr_obj_count_max);
ZCACHE_SYSFS_RO(curr_objnode_count_max);
ZCACHE_SYSFS_RO(flush_total);
ZCACHE_SYSFS_RO(flush_found);
ZCACHE_SYSFS_RO(flobj_total);
ZCACHE_SYSFS_RO(flobj_found);
ZCACHE_SYSFS_RO(failed_eph_puts);
ZCACHE_SYSFS_RO(nonactive_puts);
ZCACHE_SYSFS_RO(failed_pers_puts);
ZCACHE_SYSFS_RO(zbud_curr_zbytes);
ZCACHE_SYSFS_RO(zbud_cumul_zpages);
ZCACHE_SYSFS_RO(zbud_cumul_zbytes);
ZCACHE_SYSFS_RO(zbud_buddied_count);
ZCACHE_SYSFS_RO(evicted_raw_pages);
ZCACHE_SYSFS_RO(evicted_unbuddied_pages);
ZCACHE_SYSFS_RO(evicted_buddied_pages);
ZCACHE_SYSFS_RO(failed_get_free_pages);
ZCACHE_SYSFS_RO(failed_alloc);
ZCACHE_SYSFS_RO(put_to_flush);
ZCACHE_SYSFS_RO(compress_poor);
ZCACHE_SYSFS_RO(mean_compress_poor);
ZCACHE_SYSFS_RO(policy_percent_exceeded);
ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_raw_pages);
ZCACHE_SYSFS_RO_ATOMIC(zbud_curr_zpages);
ZCACHE_SYSFS_RO_ATOMIC(curr_obj_count);
ZCACHE_SYSFS_RO_ATOMIC(curr_objnode_count);
ZCACHE_SYSFS_RO_CUSTOM(zbud_unbuddied_list_counts,
			zbud_show_unbuddied_list_counts);
ZCACHE_SYSFS_RO_CUSTOM(zbud_cumul_chunk_counts,
			zbud_show_cumul_chunk_counts);
ZCACHE_SYSFS_RO_CUSTOM(zv_curr_dist_counts,
			zv_curr_dist_counts_show);
ZCACHE_SYSFS_RO_CUSTOM(zv_cumul_dist_counts,
			zv_cumul_dist_counts_show);

static struct attribute *zcache_attrs[] = {
	&zcache_curr_obj_count_attr.attr,
	&zcache_curr_obj_count_max_attr.attr,
	&zcache_curr_objnode_count_attr.attr,
	&zcache_curr_objnode_count_max_attr.attr,
	&zcache_flush_total_attr.attr,
	&zcache_flobj_total_attr.attr,
	&zcache_flush_found_attr.attr,
	&zcache_flobj_found_attr.attr,
	&zcache_failed_eph_puts_attr.attr,
	&zcache_nonactive_puts_attr.attr,
	&zcache_failed_pers_puts_attr.attr,
	&zcache_policy_percent_exceeded_attr.attr,
	&zcache_compress_poor_attr.attr,
	&zcache_mean_compress_poor_attr.attr,
	&zcache_zbud_curr_raw_pages_attr.attr,
	&zcache_zbud_curr_zpages_attr.attr,
	&zcache_zbud_curr_zbytes_attr.attr,
	&zcache_zbud_cumul_zpages_attr.attr,
	&zcache_zbud_cumul_zbytes_attr.attr,
	&zcache_zbud_buddied_count_attr.attr,
	&zcache_evicted_raw_pages_attr.attr,
	&zcache_evicted_unbuddied_pages_attr.attr,
	&zcache_evicted_buddied_pages_attr.attr,
	&zcache_failed_get_free_pages_attr.attr,
	&zcache_failed_alloc_attr.attr,
	&zcache_put_to_flush_attr.attr,
	&zcache_zbud_unbuddied_list_counts_attr.attr,
	&zcache_zbud_cumul_chunk_counts_attr.attr,
	&zcache_zv_curr_dist_counts_attr.attr,
	&zcache_zv_cumul_dist_counts_attr.attr,
	&zcache_zv_max_zsize_attr.attr,
	&zcache_zv_max_mean_zsize_attr.attr,
	&zcache_zv_page_count_policy_percent_attr.attr,
	NULL,
};

static struct attribute_group zcache_attr_group = {
	.attrs = zcache_attrs,
	.name = "zcache",
};

#define RAMSTER_SYSFS_RO(_name) \
	static ssize_t ramster_##_name##_show(struct kobject *kobj, \
				struct kobj_attribute *attr, char *buf) \
	{ \
		return sprintf(buf, "%lu\n", ramster_##_name); \
	} \
	static struct kobj_attribute ramster_##_name##_attr = { \
		.attr = { .name = __stringify(_name), .mode = 0444 }, \
		.show = ramster_##_name##_show, \
	}

#define RAMSTER_SYSFS_RW(_name) \
	static ssize_t ramster_##_name##_show(struct kobject *kobj, \
				struct kobj_attribute *attr, char *buf) \
	{ \
		return sprintf(buf, "%lu\n", ramster_##_name); \
	} \
	static ssize_t ramster_##_name##_store(struct kobject *kobj, \
		struct kobj_attribute *attr, const char *buf, size_t count) \
	{ \
		int err; \
		unsigned long enable; \
		err = kstrtoul(buf, 10, &enable); \
		if (err) \
			return -EINVAL; \
		ramster_##_name = enable; \
		return count; \
	} \
	static struct kobj_attribute ramster_##_name##_attr = { \
		.attr = { .name = __stringify(_name), .mode = 0644 }, \
		.show = ramster_##_name##_show, \
		.store = ramster_##_name##_store, \
	}

#define RAMSTER_SYSFS_RO_ATOMIC(_name) \
	static ssize_t ramster_##_name##_show(struct kobject *kobj, \
				struct kobj_attribute *attr, char *buf) \
	{ \
	    return sprintf(buf, "%d\n", atomic_read(&ramster_##_name)); \
	} \
	static struct kobj_attribute ramster_##_name##_attr = { \
		.attr = { .name = __stringify(_name), .mode = 0444 }, \
		.show = ramster_##_name##_show, \
	}

RAMSTER_SYSFS_RO(interface_revision);
RAMSTER_SYSFS_RO_ATOMIC(remote_pers_pages);
RAMSTER_SYSFS_RW(pers_remotify_enable);
RAMSTER_SYSFS_RW(eph_remotify_enable);
RAMSTER_SYSFS_RO(eph_pages_remoted);
RAMSTER_SYSFS_RO(eph_pages_remote_failed);
RAMSTER_SYSFS_RO(pers_pages_remoted);
RAMSTER_SYSFS_RO(pers_pages_remote_failed);
RAMSTER_SYSFS_RO(pers_pages_remote_nomem);
RAMSTER_SYSFS_RO(remote_pages_flushed);
RAMSTER_SYSFS_RO(remote_page_flushes_failed);
RAMSTER_SYSFS_RO(remote_objects_flushed);
RAMSTER_SYSFS_RO(remote_object_flushes_failed);
RAMSTER_SYSFS_RO(remote_eph_pages_succ_get);
RAMSTER_SYSFS_RO(remote_eph_pages_unsucc_get);
RAMSTER_SYSFS_RO(remote_pers_pages_succ_get);
RAMSTER_SYSFS_RO(remote_pers_pages_unsucc_get);
RAMSTER_SYSFS_RO_ATOMIC(foreign_eph_pampd_count);
RAMSTER_SYSFS_RO(foreign_eph_pampd_count_max);
RAMSTER_SYSFS_RO_ATOMIC(foreign_pers_pampd_count);
RAMSTER_SYSFS_RO(foreign_pers_pampd_count_max);
RAMSTER_SYSFS_RO_ATOMIC(curr_flnode_count);
RAMSTER_SYSFS_RO(curr_flnode_count_max);

#define MANUAL_NODES 8
static bool ramster_nodes_manual_up[MANUAL_NODES];
static ssize_t ramster_manual_node_up_show(struct kobject *kobj,
				struct kobj_attribute *attr, char *buf)
{
	int i;
	char *p = buf;
	for (i = 0; i < MANUAL_NODES; i++)
		if (ramster_nodes_manual_up[i])
			p += sprintf(p, "%d ", i);
	p += sprintf(p, "\n");
	return p - buf;
}

static ssize_t ramster_manual_node_up_store(struct kobject *kobj,
		struct kobj_attribute *attr, const char *buf, size_t count)
{
	int err;
	unsigned long node_num;

	err = kstrtoul(buf, 10, &node_num);
	if (err) {
		pr_err("ramster: bad strtoul?\n");
		return -EINVAL;
	}
	if (node_num >= MANUAL_NODES) {
		pr_err("ramster: bad node_num=%lu?\n", node_num);
		return -EINVAL;
	}
	if (ramster_nodes_manual_up[node_num]) {
		pr_err("ramster: node %d already up, ignoring\n",
							(int)node_num);
	} else {
		ramster_nodes_manual_up[node_num] = true;
		r2net_hb_node_up_manual((int)node_num);
	}
	return count;
}

static struct kobj_attribute ramster_manual_node_up_attr = {
	.attr = { .name = "manual_node_up", .mode = 0644 },
	.show = ramster_manual_node_up_show,
	.store = ramster_manual_node_up_store,
};

static ssize_t ramster_remote_target_nodenum_show(struct kobject *kobj,
				struct kobj_attribute *attr, char *buf)
{
	if (ramster_remote_target_nodenum == -1UL)
		return sprintf(buf, "unset\n");
	else
		return sprintf(buf, "%d\n", ramster_remote_target_nodenum);
}

static ssize_t ramster_remote_target_nodenum_store(struct kobject *kobj,
		struct kobj_attribute *attr, const char *buf, size_t count)
{
	int err;
	unsigned long node_num;

	err = kstrtoul(buf, 10, &node_num);
	if (err) {
		pr_err("ramster: bad strtoul?\n");
		return -EINVAL;
	} else if (node_num == -1UL) {
		pr_err("ramster: disabling all remotification, "
			"data may still reside on remote nodes however\n");
		return -EINVAL;
	} else if (node_num >= MANUAL_NODES) {
		pr_err("ramster: bad node_num=%lu?\n", node_num);
		return -EINVAL;
	} else if (!ramster_nodes_manual_up[node_num]) {
		pr_err("ramster: node %d not up, ignoring setting "
			"of remotification target\n", (int)node_num);
	} else if (r2net_remote_target_node_set((int)node_num) >= 0) {
		pr_info("ramster: node %d set as remotification target\n",
				(int)node_num);
		ramster_remote_target_nodenum = (int)node_num;
	} else {
		pr_err("ramster: bad num to node node_num=%d?\n",
				(int)node_num);
		return -EINVAL;
	}
	return count;
}

static struct kobj_attribute ramster_remote_target_nodenum_attr = {
	.attr = { .name = "remote_target_nodenum", .mode = 0644 },
	.show = ramster_remote_target_nodenum_show,
	.store = ramster_remote_target_nodenum_store,
};


static struct attribute *ramster_attrs[] = {
	&ramster_interface_revision_attr.attr,
	&ramster_pers_remotify_enable_attr.attr,
	&ramster_eph_remotify_enable_attr.attr,
	&ramster_remote_pers_pages_attr.attr,
	&ramster_eph_pages_remoted_attr.attr,
	&ramster_eph_pages_remote_failed_attr.attr,
	&ramster_pers_pages_remoted_attr.attr,
	&ramster_pers_pages_remote_failed_attr.attr,
	&ramster_pers_pages_remote_nomem_attr.attr,
	&ramster_remote_pages_flushed_attr.attr,
	&ramster_remote_page_flushes_failed_attr.attr,
	&ramster_remote_objects_flushed_attr.attr,
	&ramster_remote_object_flushes_failed_attr.attr,
	&ramster_remote_eph_pages_succ_get_attr.attr,
	&ramster_remote_eph_pages_unsucc_get_attr.attr,
	&ramster_remote_pers_pages_succ_get_attr.attr,
	&ramster_remote_pers_pages_unsucc_get_attr.attr,
	&ramster_foreign_eph_pampd_count_attr.attr,
	&ramster_foreign_eph_pampd_count_max_attr.attr,
	&ramster_foreign_pers_pampd_count_attr.attr,
	&ramster_foreign_pers_pampd_count_max_attr.attr,
	&ramster_curr_flnode_count_attr.attr,
	&ramster_curr_flnode_count_max_attr.attr,
	&ramster_manual_node_up_attr.attr,
	&ramster_remote_target_nodenum_attr.attr,
	NULL,
};

static struct attribute_group ramster_attr_group = {
	.attrs = ramster_attrs,
	.name = "ramster",
};

#endif /* CONFIG_SYSFS */
/*
 * 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;

/*
 * zcache shrinker interface (only useful for ephemeral pages, so zbud only)
 */
static int shrink_zcache_memory(struct shrinker *shrink,
				struct shrink_control *sc)
{
	int ret = -1;
	int nr = sc->nr_to_scan;
	gfp_t gfp_mask = sc->gfp_mask;

	if (nr >= 0) {
		if (!(gfp_mask & __GFP_FS))
			/* does this case really need to be skipped? */
			goto out;
		zbud_evict_pages(nr);
	}
	ret = (int)atomic_read(&zcache_zbud_curr_raw_pages);
out:
	return ret;
}

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

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

int zcache_put(int cli_id, int pool_id, struct tmem_oid *oidp,
			uint32_t index, char *data, size_t size,
			bool raw, int ephemeral)
{
	struct tmem_pool *pool;
	int ret = -1;

	BUG_ON(!irqs_disabled());
	pool = zcache_get_pool_by_id(cli_id, pool_id);
	if (unlikely(pool == NULL))
		goto out;
	if (!zcache_freeze && zcache_do_preload(pool) == 0) {
		/* preload does preempt_disable on success */
		ret = tmem_put(pool, oidp, index, data, size, raw, ephemeral);
		if (ret < 0) {
			if (is_ephemeral(pool))
				zcache_failed_eph_puts++;
			else
				zcache_failed_pers_puts++;
		}
		zcache_put_pool(pool);
		preempt_enable_no_resched();
	} else {
		zcache_put_to_flush++;
		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(int cli_id, int pool_id, struct tmem_oid *oidp,
			uint32_t index, char *data, 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, data, sizep,
					raw, get_and_free);
		zcache_put_pool(pool);
	}
	WARN_ONCE((!eph && (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
	if (ret == -EAGAIN)
		BUG(); /* FIXME... don't need this anymore??? let's ensure */
	return ret;
}

int zcache_flush(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);
	zcache_flush_total++;
	pool = zcache_get_pool_by_id(cli_id, pool_id);
	ramster_do_preload_flnode_only(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)
		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);
	zcache_flobj_total++;
	pool = zcache_get_pool_by_id(cli_id, pool_id);
	ramster_do_preload_flnode_only(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)
		zcache_flobj_found++;
	local_irq_restore(flags);
	return ret;
}

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);
	pr_info("ramster: destroyed pool id=%d cli_id=%d\n", pool_id, cli_id);
out:
	return ret;
}

static int zcache_destroy_pool(int pool_id)
{
	return zcache_client_destroy_pool(LOCAL_CLIENT, pool_id);
}

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) {
		pr_info("ramster: pool creation failed: out of memory\n");
		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("ramster: pool creation failed: max exceeded\n");
		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("ramster: created %s tmem pool, id=%d, local client\n",
			flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
			poolid);
	else
		pr_info("ramster: created %s tmem pool, id=%d, client=%d\n",
			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(int cli_id, int pool_id, bool ephemeral)
{
	struct tmem_pool *pool;
	struct zcache_client *cli = NULL;
	uint32_t flags = ephemeral ? 0 : TMEM_POOL_PERSIST;
	int ret = -1;

	if (cli_id == LOCAL_CLIENT)
		goto out;
	if (pool_id >= MAX_POOLS_PER_CLIENT)
		goto out;
	else if ((unsigned int)cli_id < MAX_CLIENTS)
		cli = &zcache_clients[cli_id];
	if ((ephemeral && !use_cleancache) || (!ephemeral && !use_frontswap))
		BUG(); /* FIXME, handle more gracefully later */
	if (!cli->allocated) {
		if (zcache_new_client(cli_id))
			BUG(); /* FIXME, handle more gracefully later */
		cli = &zcache_clients[cli_id];
	}
	atomic_inc(&cli->refcount);
	pool = cli->tmem_pools[pool_id];
	if (pool != NULL) {
		if (pool->persistent && ephemeral) {
			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) {
		pr_info("ramster: pool creation failed: out of memory\n");
		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("ramster: AUTOcreated %s tmem poolid=%d, for remote client=%d\n",
		flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
		pool_id, cli_id);
	ret = 0;
out:
	if (cli == NULL)
		BUG(); /* FIXME, handle more gracefully later */
		/* pr_err("zcache_autocreate_pool: failed\n"); */
	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.
 */

#ifdef CONFIG_CLEANCACHE
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;

#ifdef __PG_WAS_ACTIVE
	if (!PageWasActive(page)) {
		zcache_nonactive_puts++;
		return;
	}
#endif
	if (likely(ind == index)) {
		char *kva = page_address(page);

		(void)zcache_put(LOCAL_CLIENT, pool_id, &oid, index,
			kva, PAGE_SIZE, 0, 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;
	int ret = -1;

	preempt_disable();
	if (likely(ind == index)) {
		char *kva = page_address(page);
		size_t size = PAGE_SIZE;

		ret = zcache_get(LOCAL_CLIENT, pool_id, &oid, index,
			kva, &size, 0, 0);
#ifdef __PG_WAS_ACTIVE
		if (ret == 0)
			SetPageWasActive(page);
#endif
	}
	preempt_enable();
	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(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_destroy_pool(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;
}
#endif

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

/*
 * Swizzling increases objects per swaptype, increasing tmem concurrency
 * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
 */
#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;
}

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;
	char *kva;

	BUG_ON(!PageLocked(page));
	if (likely(ind64 == ind)) {
		local_irq_save(flags);
		kva = page_address(page);
		ret = zcache_put(LOCAL_CLIENT, zcache_frontswap_poolid,
				&oid, iswiz(ind), kva, PAGE_SIZE, 0, 0);
		local_irq_restore(flags);
	}
	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);
	int ret = -1;

	preempt_disable(); /* FIXME, remove this? */
	BUG_ON(!PageLocked(page));
	if (likely(ind64 == ind)) {
		char *kva = page_address(page);
		size_t size = PAGE_SIZE;

		ret = zcache_get(LOCAL_CLIENT, zcache_frontswap_poolid,
					&oid, iswiz(ind), kva, &size, 0, -1);
	}
	preempt_enable(); /* FIXME, remove this? */
	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(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 = {
	.put_page = zcache_frontswap_put_page,
	.get_page = 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;
}
#endif

/*
 * frontswap selfshrinking
 */

#ifdef CONFIG_FRONTSWAP
/* In HZ, controls frequency of worker invocation. */
static unsigned int selfshrink_interval __read_mostly = 5;

static void selfshrink_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(selfshrink_worker, selfshrink_process);

/* Enable/disable with sysfs. */
static bool frontswap_selfshrinking __read_mostly;

/* Enable/disable with kernel boot option. */
static bool use_frontswap_selfshrink __initdata = true;

/*
 * The default values for the following parameters were deemed reasonable
 * by experimentation, may be workload-dependent, and can all be
 * adjusted via sysfs.
 */

/* Control rate for frontswap shrinking. Higher hysteresis is slower. */
static unsigned int frontswap_hysteresis __read_mostly = 20;

/*
 * Number of selfshrink worker invocations to wait before observing that
 * frontswap selfshrinking should commence. Note that selfshrinking does
 * not use a separate worker thread.
 */
static unsigned int frontswap_inertia __read_mostly = 3;

/* Countdown to next invocation of frontswap_shrink() */
static unsigned long frontswap_inertia_counter;

/*
 * Invoked by the selfshrink worker thread, uses current number of pages
 * in frontswap (frontswap_curr_pages()), previous status, and control
 * values (hysteresis and inertia) to determine if frontswap should be
 * shrunk and what the new frontswap size should be.  Note that
 * frontswap_shrink is essentially a partial swapoff that immediately
 * transfers pages from the "swap device" (frontswap) back into kernel
 * RAM; despite the name, frontswap "shrinking" is very different from
 * the "shrinker" interface used by the kernel MM subsystem to reclaim
 * memory.
 */
static void frontswap_selfshrink(void)
{
	static unsigned long cur_frontswap_pages;
	static unsigned long last_frontswap_pages;
	static unsigned long tgt_frontswap_pages;

	last_frontswap_pages = cur_frontswap_pages;
	cur_frontswap_pages = frontswap_curr_pages();
	if (!cur_frontswap_pages ||
			(cur_frontswap_pages > last_frontswap_pages)) {
		frontswap_inertia_counter = frontswap_inertia;
		return;
	}
	if (frontswap_inertia_counter && --frontswap_inertia_counter)
		return;
	if (cur_frontswap_pages <= frontswap_hysteresis)
		tgt_frontswap_pages = 0;
	else
		tgt_frontswap_pages = cur_frontswap_pages -
			(cur_frontswap_pages / frontswap_hysteresis);
	frontswap_shrink(tgt_frontswap_pages);
}

static int __init ramster_nofrontswap_selfshrink_setup(char *s)
{
	use_frontswap_selfshrink = false;
	return 1;
}

__setup("noselfshrink", ramster_nofrontswap_selfshrink_setup);

static void selfshrink_process(struct work_struct *work)
{
	if (frontswap_selfshrinking && frontswap_enabled) {
		frontswap_selfshrink();
		schedule_delayed_work(&selfshrink_worker,
			selfshrink_interval * HZ);
	}
}

static int ramster_enabled;

static int __init ramster_selfshrink_init(void)
{
	frontswap_selfshrinking = ramster_enabled && use_frontswap_selfshrink;
	if (frontswap_selfshrinking)
		pr_info("ramster: Initializing frontswap "
					"selfshrinking driver.\n");
	else
		return -ENODEV;

	schedule_delayed_work(&selfshrink_worker, selfshrink_interval * HZ);

	return 0;
}

subsys_initcall(ramster_selfshrink_init);
#endif

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

static int ramster_enabled;

static int __init enable_ramster(char *s)
{
	ramster_enabled = 1;
	return 1;
}
__setup("ramster", enable_ramster);

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

static int use_cleancache = 1;

static int __init no_cleancache(char *s)
{
	pr_info("INIT no_cleancache called\n");
	use_cleancache = 0;
	return 1;
}

/*
 * FIXME: need to guarantee this gets checked before zcache_init is called
 * What is the correct way to achieve this?
 */
early_param("nocleancache", no_cleancache);

static int use_frontswap = 1;

static int __init no_frontswap(char *s)
{
	pr_info("INIT no_frontswap called\n");
	use_frontswap = 0;
	return 1;
}

__setup("nofrontswap", no_frontswap);

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

#ifdef CONFIG_SYSFS
	ret = sysfs_create_group(mm_kobj, &zcache_attr_group);
	ret = sysfs_create_group(mm_kobj, &ramster_attr_group);
	if (ret) {
		pr_err("ramster: can't create sysfs\n");
		goto out;
	}
#endif /* CONFIG_SYSFS */
#if defined(CONFIG_CLEANCACHE) || defined(CONFIG_FRONTSWAP)
	if (ramster_enabled) {
		unsigned int cpu;

		(void)r2net_register_handlers();
		tmem_register_hostops(&zcache_hostops);
		tmem_register_pamops(&zcache_pamops);
		ret = register_cpu_notifier(&zcache_cpu_notifier_block);
		if (ret) {
			pr_err("ramster: can't register cpu notifier\n");
			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);
	ramster_flnode_cache = kmem_cache_create("ramster_flnode",
				sizeof(struct flushlist_node), 0, 0, NULL);
#endif
#ifdef CONFIG_CLEANCACHE
	pr_info("INIT ramster_enabled=%d use_cleancache=%d\n",
					ramster_enabled, use_cleancache);
	if (ramster_enabled && use_cleancache) {
		struct cleancache_ops old_ops;

		zbud_init();
		register_shrinker(&zcache_shrinker);
		old_ops = zcache_cleancache_register_ops();
		pr_info("ramster: cleancache enabled using kernel "
			"transcendent memory and compression buddies\n");
		if (old_ops.init_fs != NULL)
			pr_warning("ramster: cleancache_ops overridden");
	}
#endif
#ifdef CONFIG_FRONTSWAP
	pr_info("INIT ramster_enabled=%d use_frontswap=%d\n",
					ramster_enabled, use_frontswap);
	if (ramster_enabled && use_frontswap) {
		struct frontswap_ops old_ops;

		zcache_new_client(LOCAL_CLIENT);
		old_ops = zcache_frontswap_register_ops();
		pr_info("ramster: frontswap enabled using kernel "
			"transcendent memory and xvmalloc\n");
		if (old_ops.init != NULL)
			pr_warning("ramster: frontswap_ops overridden");
	}
	if (ramster_enabled && (use_frontswap || use_cleancache))
		ramster_remotify_init();
#endif
out:
	return ret;
}

module_init(zcache_init)