staging: ramster: move to new zcache2 codebase

[V2: rebased to apply to 20120905 staging-next, no other changes]

The original zcache in staging is a "demo" version, and this is a massive
rewrite.  This was intended to result in a merged zcache and ramster, but
that option has been blocked so, to continue forward progress on ramster
and future related projects, only ramster moves to the new codebase.
To differentiate between the old demo zcache and the rewrite, we refer
to the latter as zcache2, config'd as CONFIG_ZCACHE2.  Zcache and zcache2
cannot be built in the same kernel, so CONFIG_ZCACHE2 implies !CONFIG_ZCACHE.

This developer still has hope that zcache and zcache2 will be merged
into one codebase.  Until then, zcache2 can be considered a one-node
version of ramster.

No history of changes was recorded during the zcache2 rewrite and recreating
a sane one would be a Sisyphean task but, since ramster is still in
staging and has been unchanged since it was merged, presumably this
is acceptable.

This commit also provides the hooks in zcache2 for ramster, but all
ramster-specific code is provided in a separate commit.

Some of the highlights of this rewritten codebase for zcache2:
(Note: If you are not familiar with the tmem terminology, you can review
it here: http://lwn.net/Articles/454795/ )
 1. Merge of "demo" zcache and the v1.1 version of zcache in ramster.  Zcache
    and ramster had a great deal of duplicate code which is now merged.
    In essence, zcache2 *is* ramster but with no remote machine available,
    but !CONFIG_RAMSTER will avoid compiling lots of ramster-specific code.
 2. Allocator.  Previously, persistent pools used zsmalloc and ephemeral pools
    used zbud.  Now a completely rewritten zbud is used for both.  Notably
    this zbud maintains all persistent (frontswap) and ephemeral (cleancache)
    pageframes in separate queues in LRU order.
 3. Interaction with page allocator.  Zbud does no page allocation/freeing,
    it is done entirely in zcache2 where it can be tracked more effectively.
 4. Better pre-allocation.  Previously, on put, if a new pageframe could not be
    pre-allocated, the put would fail, even if the allocator had plenty of
    partial pages where the data could be stored; this is now fixed.
 5. Ouroboros ("eating its own tail") allocation.  If no pageframe can be
    allocated AND no partial pages are available, the least-recently-used
    ephemeral pageframe is reclaimed immediately (including flushing tmem
    pointers to it) and re-used.  This ensures that most-recently-used
    cleancache pages are more likely to be retained than LRU pages and also
    that, as in the core mm subsystem, anonymous pages have a higher priority
    than clean page cache pages.
 6. Zcache and zbud now use debugfs instead of sysfs.  Ramster uses debugfs
    where possible and sysfs where necessary.  (Some ramster configuration
    is done from userspace so some sysfs is necessary.)
 7. Modularization.  As some have observed, the monolithic zcache-main.c code
    included zbud code, which has now been separated into its own code module.
    Much ramster-specific code in the old ramster zcache-main.c has also been
    moved into ramster.c so that it does not get compiled with !CONFIG_RAMSTER.
 8. Rebased to 3.5.

This new codebase also provides hooks for several future new features:
 A. WasActive patch, requires some mm/frontswap changes previously posted.
    A new version of this patch will be provided separately.
    See ifdef __PG_WAS_ACTIVE
 B. Exclusive gets.  It seems tmem _can_ support exclusive gets with a
    minor change to both zcache2 and a small backwards-compatible change
    to frontswap.c.  Explanation and frontswap patch will be provided
    separately.  See ifdef FRONTSWAP_HAS_EXCLUSIVE_GETS
 C. Ouroboros writeback.  Since persistent (frontswap) pages may now also be
    reclaimed in LRU order, the foundation is in place to properly writeback
    these pages back into the swap cache and then the swap disk.  This is still
    under development and requires some other mm changes which are prototyped.
    See ifdef FRONTSWAP_HAS_UNUSE.

A new feature that desperately needs attention (if someone is looking for
a way to contribute) is kernel module support.  A preliminary version of
a patch was posted by Erlangen University and needs to be integrated and
tested for zcache2 and brought up to kernel standards.

If anybody is interested on helping out with any of these, let me know!

Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1812 insertions, 0 deletions

diff --git a/drivers/staging/ramster/zcache-main.c b/drivers/staging/ramster/zcache-main.c
new file mode 100644
index 0000000..24b3d4a
--- /dev/null
+++ b/drivers/staging/ramster/zcache-main.c
@@ -0,0 +1,1812 @@
+/*
+ * zcache.c
+ *
+ * Copyright (c) 2010-2012, Dan Magenheimer, Oracle Corp.
+ * Copyright (c) 2010,2011, Nitin Gupta
+ *
+ * Zcache provides an in-kernel "host implementation" for transcendent memory
+ * ("tmem") and, thus indirectly, for cleancache and frontswap.  Zcache uses
+ * lzo1x compression to improve density and an embedded allocator called
+ * "zbud" which "buddies" two compressed pages semi-optimally in each physical
+ * pageframe.  Zbud is integrally tied into tmem to allow pageframes to
+ * be "reclaimed" efficiently.
+ */
+
+#include <linux/module.h>
+#include <linux/cpu.h>
+#include <linux/highmem.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <linux/math64.h>
+#include <linux/crypto.h>
+
+#include <linux/cleancache.h>
+#include <linux/frontswap.h>
+#include "tmem.h"
+#include "zcache.h"
+#include "zbud.h"
+#include "ramster.h"
+#ifdef CONFIG_RAMSTER
+static int ramster_enabled;
+#else
+#define ramster_enabled 0
+#endif
+
+#ifndef __PG_WAS_ACTIVE
+static inline bool PageWasActive(struct page *page)
+{
+	return true;
+}
+
+static inline void SetPageWasActive(struct page *page)
+{
+}
+#endif
+
+#ifdef FRONTSWAP_HAS_EXCLUSIVE_GETS
+static bool frontswap_has_exclusive_gets __read_mostly = true;
+#else
+static bool frontswap_has_exclusive_gets __read_mostly;
+static inline void frontswap_tmem_exclusive_gets(bool b)
+{
+}
+#endif
+
+static int zcache_enabled __read_mostly;
+static int disable_cleancache __read_mostly;
+static int disable_frontswap __read_mostly;
+static int disable_frontswap_ignore_nonactive __read_mostly;
+static int disable_cleancache_ignore_nonactive __read_mostly;
+static char *namestr __read_mostly = "zcache";
+
+#define ZCACHE_GFP_MASK \
+	(__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC)
+
+MODULE_LICENSE("GPL");
+
+/* crypto API for zcache  */
+#define ZCACHE_COMP_NAME_SZ CRYPTO_MAX_ALG_NAME
+static char zcache_comp_name[ZCACHE_COMP_NAME_SZ] __read_mostly;
+static struct crypto_comp * __percpu *zcache_comp_pcpu_tfms __read_mostly;
+
+enum comp_op {
+	ZCACHE_COMPOP_COMPRESS,
+	ZCACHE_COMPOP_DECOMPRESS
+};
+
+static inline int zcache_comp_op(enum comp_op op,
+				const u8 *src, unsigned int slen,
+				u8 *dst, unsigned int *dlen)
+{
+	struct crypto_comp *tfm;
+	int ret = -1;
+
+	BUG_ON(!zcache_comp_pcpu_tfms);
+	tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, get_cpu());
+	BUG_ON(!tfm);
+	switch (op) {
+	case ZCACHE_COMPOP_COMPRESS:
+		ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
+		break;
+	case ZCACHE_COMPOP_DECOMPRESS:
+		ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	put_cpu();
+	return ret;
+}
+
+/*
+ * policy parameters
+ */
+
+/*
+ * byte count defining poor compression; pages with greater zsize will be
+ * rejected
+ */
+static unsigned int zbud_max_zsize __read_mostly = (PAGE_SIZE / 8) * 7;
+/*
+ * byte count defining poor *mean* compression; pages with greater zsize
+ * will be rejected until sufficient better-compressed pages are accepted
+ * driving the mean below this threshold
+ */
+static unsigned int zbud_max_mean_zsize __read_mostly = (PAGE_SIZE / 8) * 5;
+
+/*
+ * for now, used named slabs so can easily track usage; later can
+ * either just use kmalloc, or perhaps add a slab-like allocator
+ * to more carefully manage total memory utilization
+ */
+static struct kmem_cache *zcache_objnode_cache;
+static struct kmem_cache *zcache_obj_cache;
+
+static DEFINE_PER_CPU(struct zcache_preload, zcache_preloads) = { 0, };
+
+/* we try to keep these statistics SMP-consistent */
+static long zcache_obj_count;
+static atomic_t zcache_obj_atomic = ATOMIC_INIT(0);
+static long zcache_obj_count_max;
+static long zcache_objnode_count;
+static atomic_t zcache_objnode_atomic = ATOMIC_INIT(0);
+static long zcache_objnode_count_max;
+static u64 zcache_eph_zbytes;
+static atomic_long_t zcache_eph_zbytes_atomic = ATOMIC_INIT(0);
+static u64 zcache_eph_zbytes_max;
+static u64 zcache_pers_zbytes;
+static atomic_long_t zcache_pers_zbytes_atomic = ATOMIC_INIT(0);
+static u64 zcache_pers_zbytes_max;
+static long zcache_eph_pageframes;
+static atomic_t zcache_eph_pageframes_atomic = ATOMIC_INIT(0);
+static long zcache_eph_pageframes_max;
+static long zcache_pers_pageframes;
+static atomic_t zcache_pers_pageframes_atomic = ATOMIC_INIT(0);
+static long zcache_pers_pageframes_max;
+static long zcache_pageframes_alloced;
+static atomic_t zcache_pageframes_alloced_atomic = ATOMIC_INIT(0);
+static long zcache_pageframes_freed;
+static atomic_t zcache_pageframes_freed_atomic = ATOMIC_INIT(0);
+static long zcache_eph_zpages;
+static atomic_t zcache_eph_zpages_atomic = ATOMIC_INIT(0);
+static long zcache_eph_zpages_max;
+static long zcache_pers_zpages;
+static atomic_t zcache_pers_zpages_atomic = ATOMIC_INIT(0);
+static long zcache_pers_zpages_max;
+
+/* but for the rest of these, counting races are ok */
+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_failed_pers_puts;
+static unsigned long zcache_failed_getfreepages;
+static unsigned long zcache_failed_alloc;
+static unsigned long zcache_put_to_flush;
+static unsigned long zcache_compress_poor;
+static unsigned long zcache_mean_compress_poor;
+static unsigned long zcache_eph_ate_tail;
+static unsigned long zcache_eph_ate_tail_failed;
+static unsigned long zcache_pers_ate_eph;
+static unsigned long zcache_pers_ate_eph_failed;
+static unsigned long zcache_evicted_eph_zpages;
+static unsigned long zcache_evicted_eph_pageframes;
+static unsigned long zcache_last_active_file_pageframes;
+static unsigned long zcache_last_inactive_file_pageframes;
+static unsigned long zcache_last_active_anon_pageframes;
+static unsigned long zcache_last_inactive_anon_pageframes;
+static unsigned long zcache_eph_nonactive_puts_ignored;
+static unsigned long zcache_pers_nonactive_puts_ignored;
+
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+#define	zdfs	debugfs_create_size_t
+#define	zdfs64	debugfs_create_u64
+static int zcache_debugfs_init(void)
+{
+	struct dentry *root = debugfs_create_dir("zcache", NULL);
+	if (root == NULL)
+		return -ENXIO;
+
+	zdfs("obj_count", S_IRUGO, root, &zcache_obj_count);
+	zdfs("obj_count_max", S_IRUGO, root, &zcache_obj_count_max);
+	zdfs("objnode_count", S_IRUGO, root, &zcache_objnode_count);
+	zdfs("objnode_count_max", S_IRUGO, root, &zcache_objnode_count_max);
+	zdfs("flush_total", S_IRUGO, root, &zcache_flush_total);
+	zdfs("flush_found", S_IRUGO, root, &zcache_flush_found);
+	zdfs("flobj_total", S_IRUGO, root, &zcache_flobj_total);
+	zdfs("flobj_found", S_IRUGO, root, &zcache_flobj_found);
+	zdfs("failed_eph_puts", S_IRUGO, root, &zcache_failed_eph_puts);
+	zdfs("failed_pers_puts", S_IRUGO, root, &zcache_failed_pers_puts);
+	zdfs("failed_get_free_pages", S_IRUGO, root,
+				&zcache_failed_getfreepages);
+	zdfs("failed_alloc", S_IRUGO, root, &zcache_failed_alloc);
+	zdfs("put_to_flush", S_IRUGO, root, &zcache_put_to_flush);
+	zdfs("compress_poor", S_IRUGO, root, &zcache_compress_poor);
+	zdfs("mean_compress_poor", S_IRUGO, root, &zcache_mean_compress_poor);
+	zdfs("eph_ate_tail", S_IRUGO, root, &zcache_eph_ate_tail);
+	zdfs("eph_ate_tail_failed", S_IRUGO, root, &zcache_eph_ate_tail_failed);
+	zdfs("pers_ate_eph", S_IRUGO, root, &zcache_pers_ate_eph);
+	zdfs("pers_ate_eph_failed", S_IRUGO, root, &zcache_pers_ate_eph_failed);
+	zdfs("evicted_eph_zpages", S_IRUGO, root, &zcache_evicted_eph_zpages);
+	zdfs("evicted_eph_pageframes", S_IRUGO, root,
+				&zcache_evicted_eph_pageframes);
+	zdfs("eph_pageframes", S_IRUGO, root, &zcache_eph_pageframes);
+	zdfs("eph_pageframes_max", S_IRUGO, root, &zcache_eph_pageframes_max);
+	zdfs("pers_pageframes", S_IRUGO, root, &zcache_pers_pageframes);
+	zdfs("pers_pageframes_max", S_IRUGO, root, &zcache_pers_pageframes_max);
+	zdfs("eph_zpages", S_IRUGO, root, &zcache_eph_zpages);
+	zdfs("eph_zpages_max", S_IRUGO, root, &zcache_eph_zpages_max);
+	zdfs("pers_zpages", S_IRUGO, root, &zcache_pers_zpages);
+	zdfs("pers_zpages_max", S_IRUGO, root, &zcache_pers_zpages_max);
+	zdfs("last_active_file_pageframes", S_IRUGO, root,
+				&zcache_last_active_file_pageframes);
+	zdfs("last_inactive_file_pageframes", S_IRUGO, root,
+				&zcache_last_inactive_file_pageframes);
+	zdfs("last_active_anon_pageframes", S_IRUGO, root,
+				&zcache_last_active_anon_pageframes);
+	zdfs("last_inactive_anon_pageframes", S_IRUGO, root,
+				&zcache_last_inactive_anon_pageframes);
+	zdfs("eph_nonactive_puts_ignored", S_IRUGO, root,
+				&zcache_eph_nonactive_puts_ignored);
+	zdfs("pers_nonactive_puts_ignored", S_IRUGO, root,
+				&zcache_pers_nonactive_puts_ignored);
+	zdfs64("eph_zbytes", S_IRUGO, root, &zcache_eph_zbytes);
+	zdfs64("eph_zbytes_max", S_IRUGO, root, &zcache_eph_zbytes_max);
+	zdfs64("pers_zbytes", S_IRUGO, root, &zcache_pers_zbytes);
+	zdfs64("pers_zbytes_max", S_IRUGO, root, &zcache_pers_zbytes_max);
+	return 0;
+}
+#undef	zdebugfs
+#undef	zdfs64
+#endif
+
+#define ZCACHE_DEBUG
+#ifdef ZCACHE_DEBUG
+/* developers can call this in case of ooms, e.g. to find memory leaks */
+void zcache_dump(void)
+{
+	pr_info("zcache: obj_count=%lu\n", zcache_obj_count);
+	pr_info("zcache: obj_count_max=%lu\n", zcache_obj_count_max);
+	pr_info("zcache: objnode_count=%lu\n", zcache_objnode_count);
+	pr_info("zcache: objnode_count_max=%lu\n", zcache_objnode_count_max);
+	pr_info("zcache: flush_total=%lu\n", zcache_flush_total);
+	pr_info("zcache: flush_found=%lu\n", zcache_flush_found);
+	pr_info("zcache: flobj_total=%lu\n", zcache_flobj_total);
+	pr_info("zcache: flobj_found=%lu\n", zcache_flobj_found);
+	pr_info("zcache: failed_eph_puts=%lu\n", zcache_failed_eph_puts);
+	pr_info("zcache: failed_pers_puts=%lu\n", zcache_failed_pers_puts);
+	pr_info("zcache: failed_get_free_pages=%lu\n",
+				zcache_failed_getfreepages);
+	pr_info("zcache: failed_alloc=%lu\n", zcache_failed_alloc);
+	pr_info("zcache: put_to_flush=%lu\n", zcache_put_to_flush);
+	pr_info("zcache: compress_poor=%lu\n", zcache_compress_poor);
+	pr_info("zcache: mean_compress_poor=%lu\n",
+				zcache_mean_compress_poor);
+	pr_info("zcache: eph_ate_tail=%lu\n", zcache_eph_ate_tail);
+	pr_info("zcache: eph_ate_tail_failed=%lu\n",
+				zcache_eph_ate_tail_failed);
+	pr_info("zcache: pers_ate_eph=%lu\n", zcache_pers_ate_eph);
+	pr_info("zcache: pers_ate_eph_failed=%lu\n",
+				zcache_pers_ate_eph_failed);
+	pr_info("zcache: evicted_eph_zpages=%lu\n", zcache_evicted_eph_zpages);
+	pr_info("zcache: evicted_eph_pageframes=%lu\n",
+				zcache_evicted_eph_pageframes);
+	pr_info("zcache: eph_pageframes=%lu\n", zcache_eph_pageframes);
+	pr_info("zcache: eph_pageframes_max=%lu\n", zcache_eph_pageframes_max);
+	pr_info("zcache: pers_pageframes=%lu\n", zcache_pers_pageframes);
+	pr_info("zcache: pers_pageframes_max=%lu\n",
+				zcache_pers_pageframes_max);
+	pr_info("zcache: eph_zpages=%lu\n", zcache_eph_zpages);
+	pr_info("zcache: eph_zpages_max=%lu\n", zcache_eph_zpages_max);
+	pr_info("zcache: pers_zpages=%lu\n", zcache_pers_zpages);
+	pr_info("zcache: pers_zpages_max=%lu\n", zcache_pers_zpages_max);
+	pr_info("zcache: eph_zbytes=%llu\n",
+				(unsigned long long)zcache_eph_zbytes);
+	pr_info("zcache: eph_zbytes_max=%llu\n",
+				(unsigned long long)zcache_eph_zbytes_max);
+	pr_info("zcache: pers_zbytes=%llu\n",
+				(unsigned long long)zcache_pers_zbytes);
+	pr_info("zcache: pers_zbytes_max=%llu\n",
+			(unsigned long long)zcache_pers_zbytes_max);
+}
+#endif
+
+/*
+ * zcache core code starts here
+ */
+
+static struct zcache_client zcache_host;
+static struct zcache_client zcache_clients[MAX_CLIENTS];
+
+static inline bool is_local_client(struct zcache_client *cli)
+{
+	return cli == &zcache_host;
+}
+
+static struct zcache_client *zcache_get_client_by_id(uint16_t cli_id)
+{
+	struct zcache_client *cli = &zcache_host;
+
+	if (cli_id != LOCAL_CLIENT) {
+		if (cli_id >= MAX_CLIENTS)
+			goto out;
+		cli = &zcache_clients[cli_id];
+	}
+out:
+	return cli;
+}
+
+/*
+ * Tmem operations assume the poolid implies the invoking client.
+ * Zcache only has one client (the kernel itself): LOCAL_CLIENT.
+ * RAMster has each client numbered by cluster node, and a KVM version
+ * of zcache would have one client per guest and each client might
+ * have a poolid==N.
+ */
+struct tmem_pool *zcache_get_pool_by_id(uint16_t cli_id, uint16_t poolid)
+{
+	struct tmem_pool *pool = NULL;
+	struct zcache_client *cli = NULL;
+
+	cli = zcache_get_client_by_id(cli_id);
+	if (cli == NULL)
+		goto out;
+	if (!is_local_client(cli))
+		atomic_inc(&cli->refcount);
+	if (poolid < MAX_POOLS_PER_CLIENT) {
+		pool = cli->tmem_pools[poolid];
+		if (pool != NULL)
+			atomic_inc(&pool->refcount);
+	}
+out:
+	return pool;
+}
+
+void zcache_put_pool(struct tmem_pool *pool)
+{
+	struct zcache_client *cli = NULL;
+
+	if (pool == NULL)
+		BUG();
+	cli = pool->client;
+	atomic_dec(&pool->refcount);
+	if (!is_local_client(cli))
+		atomic_dec(&cli->refcount);
+}
+
+int zcache_new_client(uint16_t cli_id)
+{
+	struct zcache_client *cli;
+	int ret = -1;
+
+	cli = zcache_get_client_by_id(cli_id);
+	if (cli == NULL)
+		goto out;
+	if (cli->allocated)
+		goto out;
+	cli->allocated = 1;
+	ret = 0;
+out:
+	return ret;
+}
+
+/*
+ * zcache implementation for tmem host ops
+ */
+
+static struct tmem_objnode *zcache_objnode_alloc(struct tmem_pool *pool)
+{
+	struct tmem_objnode *objnode = NULL;
+	struct zcache_preload *kp;
+	int i;
+
+	kp = &__get_cpu_var(zcache_preloads);
+	for (i = 0; i < ARRAY_SIZE(kp->objnodes); i++) {
+		objnode = kp->objnodes[i];
+		if (objnode != NULL) {
+			kp->objnodes[i] = NULL;
+			break;
+		}
+	}
+	BUG_ON(objnode == NULL);
+	zcache_objnode_count = atomic_inc_return(&zcache_objnode_atomic);
+	if (zcache_objnode_count > zcache_objnode_count_max)
+		zcache_objnode_count_max = zcache_objnode_count;
+	return objnode;
+}
+
+static void zcache_objnode_free(struct tmem_objnode *objnode,
+					struct tmem_pool *pool)
+{
+	zcache_objnode_count =
+		atomic_dec_return(&zcache_objnode_atomic);
+	BUG_ON(zcache_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;
+	struct zcache_preload *kp;
+
+	kp = &__get_cpu_var(zcache_preloads);
+	obj = kp->obj;
+	BUG_ON(obj == NULL);
+	kp->obj = NULL;
+	zcache_obj_count = atomic_inc_return(&zcache_obj_atomic);
+	if (zcache_obj_count > zcache_obj_count_max)
+		zcache_obj_count_max = zcache_obj_count;
+	return obj;
+}
+
+static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
+{
+	zcache_obj_count =
+		atomic_dec_return(&zcache_obj_atomic);
+	BUG_ON(zcache_obj_count < 0);
+	kmem_cache_free(zcache_obj_cache, obj);
+}
+
+static struct tmem_hostops zcache_hostops = {
+	.obj_alloc = zcache_obj_alloc,
+	.obj_free = zcache_obj_free,
+	.objnode_alloc = zcache_objnode_alloc,
+	.objnode_free = zcache_objnode_free,
+};
+
+static struct page *zcache_alloc_page(void)
+{
+	struct page *page = alloc_page(ZCACHE_GFP_MASK);
+
+	if (page != NULL)
+		zcache_pageframes_alloced =
+			atomic_inc_return(&zcache_pageframes_alloced_atomic);
+	return page;
+}
+
+static void zcache_unacct_page(void)
+{
+	zcache_pageframes_freed =
+		atomic_inc_return(&zcache_pageframes_freed_atomic);
+}
+
+static void zcache_free_page(struct page *page)
+{
+	long curr_pageframes;
+	static long max_pageframes, min_pageframes, total_freed;
+
+	if (page == NULL)
+		BUG();
+	__free_page(page);
+	zcache_pageframes_freed =
+		atomic_inc_return(&zcache_pageframes_freed_atomic);
+	curr_pageframes = zcache_pageframes_alloced -
+			atomic_read(&zcache_pageframes_freed_atomic) -
+			atomic_read(&zcache_eph_pageframes_atomic) -
+			atomic_read(&zcache_pers_pageframes_atomic);
+	if (curr_pageframes > max_pageframes)
+		max_pageframes = curr_pageframes;
+	if (curr_pageframes < min_pageframes)
+		min_pageframes = curr_pageframes;
+#ifdef ZCACHE_DEBUG
+	if (curr_pageframes > 2L || curr_pageframes < -2L) {
+		/* pr_info here */
+	}
+#endif
+}
+
+/*
+ * zcache implementations for PAM page descriptor ops
+ */
+
+/* forward reference */
+static void zcache_compress(struct page *from,
+				void **out_va, unsigned *out_len);
+
+static struct page *zcache_evict_eph_pageframe(void);
+
+static void *zcache_pampd_eph_create(char *data, size_t size, bool raw,
+					struct tmem_handle *th)
+{
+	void *pampd = NULL, *cdata = data;
+	unsigned clen = size;
+	struct page *page = (struct page *)(data), *newpage;
+
+	if (!raw) {
+		zcache_compress(page, &cdata, &clen);
+		if (clen > zbud_max_buddy_size()) {
+			zcache_compress_poor++;
+			goto out;
+		}
+	} else {
+		BUG_ON(clen > zbud_max_buddy_size());
+	}
+
+	/* look for space via an existing match first */
+	pampd = (void *)zbud_match_prep(th, true, cdata, clen);
+	if (pampd != NULL)
+		goto got_pampd;
+
+	/* no match, now we need to find (or free up) a full page */
+	newpage = zcache_alloc_page();
+	if (newpage != NULL)
+		goto create_in_new_page;
+
+	zcache_failed_getfreepages++;
+	/* can't allocate a page, evict an ephemeral page via LRU */
+	newpage = zcache_evict_eph_pageframe();
+	if (newpage == NULL) {
+		zcache_eph_ate_tail_failed++;
+		goto out;
+	}
+	zcache_eph_ate_tail++;
+
+create_in_new_page:
+	pampd = (void *)zbud_create_prep(th, true, cdata, clen, newpage);
+	BUG_ON(pampd == NULL);
+	zcache_eph_pageframes =
+		atomic_inc_return(&zcache_eph_pageframes_atomic);
+	if (zcache_eph_pageframes > zcache_eph_pageframes_max)
+		zcache_eph_pageframes_max = zcache_eph_pageframes;
+
+got_pampd:
+	zcache_eph_zbytes =
+		atomic_long_add_return(clen, &zcache_eph_zbytes_atomic);
+	if (zcache_eph_zbytes > zcache_eph_zbytes_max)
+		zcache_eph_zbytes_max = zcache_eph_zbytes;
+	zcache_eph_zpages = atomic_inc_return(&zcache_eph_zpages_atomic);
+	if (zcache_eph_zpages > zcache_eph_zpages_max)
+		zcache_eph_zpages_max = zcache_eph_zpages;
+	if (ramster_enabled && raw)
+		ramster_count_foreign_pages(true, 1);
+out:
+	return pampd;
+}
+
+static void *zcache_pampd_pers_create(char *data, size_t size, bool raw,
+					struct tmem_handle *th)
+{
+	void *pampd = NULL, *cdata = data;
+	unsigned clen = size;
+	struct page *page = (struct page *)(data), *newpage;
+	unsigned long zbud_mean_zsize;
+	unsigned long curr_pers_zpages, total_zsize;
+
+	if (data == NULL) {
+		BUG_ON(!ramster_enabled);
+		goto create_pampd;
+	}
+	curr_pers_zpages = zcache_pers_zpages;
+/* FIXME CONFIG_RAMSTER... subtract atomic remote_pers_pages here? */
+	if (!raw)
+		zcache_compress(page, &cdata, &clen);
+	/* reject if compression is too poor */
+	if (clen > zbud_max_zsize) {
+		zcache_compress_poor++;
+		goto out;
+	}
+	/* reject if mean compression is too poor */
+	if ((clen > zbud_max_mean_zsize) && (curr_pers_zpages > 0)) {
+		total_zsize = zcache_pers_zbytes;
+		if ((long)total_zsize < 0)
+			total_zsize = 0;
+		zbud_mean_zsize = div_u64(total_zsize,
+					curr_pers_zpages);
+		if (zbud_mean_zsize > zbud_max_mean_zsize) {
+			zcache_mean_compress_poor++;
+			goto out;
+		}
+	}
+
+create_pampd:
+	/* look for space via an existing match first */
+	pampd = (void *)zbud_match_prep(th, false, cdata, clen);
+	if (pampd != NULL)
+		goto got_pampd;
+
+	/* no match, now we need to find (or free up) a full page */
+	newpage = zcache_alloc_page();
+	if (newpage != NULL)
+		goto create_in_new_page;
+	/*
+	 * FIXME do the following only if eph is oversized?
+	 * if (zcache_eph_pageframes >
+	 * (global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE) +
+	 * global_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE)))
+	 */
+	zcache_failed_getfreepages++;
+	/* can't allocate a page, evict an ephemeral page via LRU */
+	newpage = zcache_evict_eph_pageframe();
+	if (newpage == NULL) {
+		zcache_pers_ate_eph_failed++;
+		goto out;
+	}
+	zcache_pers_ate_eph++;
+
+create_in_new_page:
+	pampd = (void *)zbud_create_prep(th, false, cdata, clen, newpage);
+	BUG_ON(pampd == NULL);
+	zcache_pers_pageframes =
+		atomic_inc_return(&zcache_pers_pageframes_atomic);
+	if (zcache_pers_pageframes > zcache_pers_pageframes_max)
+		zcache_pers_pageframes_max = zcache_pers_pageframes;
+
+got_pampd:
+	zcache_pers_zpages = atomic_inc_return(&zcache_pers_zpages_atomic);
+	if (zcache_pers_zpages > zcache_pers_zpages_max)
+		zcache_pers_zpages_max = zcache_pers_zpages;
+	zcache_pers_zbytes =
+		atomic_long_add_return(clen, &zcache_pers_zbytes_atomic);
+	if (zcache_pers_zbytes > zcache_pers_zbytes_max)
+		zcache_pers_zbytes_max = zcache_pers_zbytes;
+	if (ramster_enabled && raw)
+		ramster_count_foreign_pages(false, 1);
+out:
+	return pampd;
+}
+
+/*
+ * This is called directly from zcache_put_page to pre-allocate space
+ * to store a zpage.
+ */
+void *zcache_pampd_create(char *data, unsigned int size, bool raw,
+					int eph, struct tmem_handle *th)
+{
+	void *pampd = NULL;
+	struct zcache_preload *kp;
+	struct tmem_objnode *objnode;
+	struct tmem_obj *obj;
+	int i;
+
+	BUG_ON(!irqs_disabled());
+	/* pre-allocate per-cpu metadata */
+	BUG_ON(zcache_objnode_cache == NULL);
+	BUG_ON(zcache_obj_cache == NULL);
+	kp = &__get_cpu_var(zcache_preloads);
+	for (i = 0; i < ARRAY_SIZE(kp->objnodes); i++) {
+		objnode = kp->objnodes[i];
+		if (objnode == NULL) {
+			objnode = kmem_cache_alloc(zcache_objnode_cache,
+							ZCACHE_GFP_MASK);
+			if (unlikely(objnode == NULL)) {
+				zcache_failed_alloc++;
+				goto out;
+			}
+			kp->objnodes[i] = objnode;
+		}
+	}
+	if (kp->obj == NULL) {
+		obj = kmem_cache_alloc(zcache_obj_cache, ZCACHE_GFP_MASK);
+		kp->obj = obj;
+	}
+	if (unlikely(kp->obj == NULL)) {
+		zcache_failed_alloc++;
+		goto out;
+	}
+	/*
+	 * ok, have all the metadata pre-allocated, now do the data
+	 * but since how we allocate the data is dependent on ephemeral
+	 * or persistent, we split the call here to different sub-functions
+	 */
+	if (eph)
+		pampd = zcache_pampd_eph_create(data, size, raw, th);
+	else
+		pampd = zcache_pampd_pers_create(data, size, raw, th);
+out:
+	return pampd;
+}
+
+/*
+ * This is a pamops called via tmem_put and is necessary to "finish"
+ * a pampd creation.
+ */
+void zcache_pampd_create_finish(void *pampd, bool eph)
+{
+	zbud_create_finish((struct zbudref *)pampd, eph);
+}
+
+/*
+ * This is passed as a function parameter to zbud_decompress so that
+ * zbud need not be familiar with the details of crypto. It assumes that
+ * the bytes from_va and to_va through from_va+size-1 and to_va+size-1 are
+ * kmapped.  It must be successful, else there is a logic bug somewhere.
+ */
+static void zcache_decompress(char *from_va, unsigned int size, char *to_va)
+{
+	int ret;
+	unsigned int outlen = PAGE_SIZE;
+
+	ret = zcache_comp_op(ZCACHE_COMPOP_DECOMPRESS, from_va, size,
+				to_va, &outlen);
+	BUG_ON(ret);
+	BUG_ON(outlen != PAGE_SIZE);
+}
+
+/*
+ * Decompress from the kernel va to a pageframe
+ */
+void zcache_decompress_to_page(char *from_va, unsigned int size,
+					struct page *to_page)
+{
+	char *to_va = kmap_atomic(to_page);
+	zcache_decompress(from_va, size, to_va);
+	kunmap_atomic(to_va);
+}
+
+/*
+ * fill the pageframe corresponding to the struct page with the data
+ * from the passed pampd
+ */
+static int zcache_pampd_get_data(char *data, size_t *sizep, bool raw,
+					void *pampd, struct tmem_pool *pool,
+					struct tmem_oid *oid, uint32_t index)
+{
+	int ret;
+	bool eph = !is_persistent(pool);
+
+	BUG_ON(preemptible());
+	BUG_ON(eph);	/* fix later if shared pools get implemented */
+	BUG_ON(pampd_is_remote(pampd));
+	if (raw)
+		ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
+						sizep, eph);
+	else {
+		ret = zbud_decompress((struct page *)(data),
+					(struct zbudref *)pampd, false,
+					zcache_decompress);
+		*sizep = PAGE_SIZE;
+	}
+	return ret;
+}
+
+/*
+ * fill the pageframe corresponding to the struct page with the data
+ * from the passed pampd
+ */
+static int zcache_pampd_get_data_and_free(char *data, size_t *sizep, bool raw,
+					void *pampd, struct tmem_pool *pool,
+					struct tmem_oid *oid, uint32_t index)
+{
+	int ret;
+	bool eph = !is_persistent(pool);
+	struct page *page = NULL;
+	unsigned int zsize, zpages;
+
+	BUG_ON(preemptible());
+	BUG_ON(pampd_is_remote(pampd));
+	if (raw)
+		ret = zbud_copy_from_zbud(data, (struct zbudref *)pampd,
+						sizep, eph);
+	else {
+		ret = zbud_decompress((struct page *)(data),
+					(struct zbudref *)pampd, eph,
+					zcache_decompress);
+		*sizep = PAGE_SIZE;
+	}
+	page = zbud_free_and_delist((struct zbudref *)pampd, eph,
+					&zsize, &zpages);
+	if (eph) {
+		if (page)
+			zcache_eph_pageframes =
+			    atomic_dec_return(&zcache_eph_pageframes_atomic);
+		zcache_eph_zpages =
+		    atomic_sub_return(zpages, &zcache_eph_zpages_atomic);
+		zcache_eph_zbytes =
+		    atomic_long_sub_return(zsize, &zcache_eph_zbytes_atomic);
+	} else {
+		if (page)
+			zcache_pers_pageframes =
+			    atomic_dec_return(&zcache_pers_pageframes_atomic);
+		zcache_pers_zpages =
+		    atomic_sub_return(zpages, &zcache_pers_zpages_atomic);
+		zcache_pers_zbytes =
+		    atomic_long_sub_return(zsize, &zcache_pers_zbytes_atomic);
+	}
+	if (!is_local_client(pool->client))
+		ramster_count_foreign_pages(eph, -1);
+	if (page)
+		zcache_free_page(page);
+	return ret;
+}
+
+/*
+ * free the pampd and remove it from any zcache lists
+ * pampd must no longer be pointed to from any tmem data structures!
+ */
+static void zcache_pampd_free(void *pampd, struct tmem_pool *pool,
+			      struct tmem_oid *oid, uint32_t index, bool acct)
+{
+	struct page *page = NULL;
+	unsigned int zsize, zpages;
+
+	BUG_ON(preemptible());
+	if (pampd_is_remote(pampd)) {
+		BUG_ON(!ramster_enabled);
+		pampd = ramster_pampd_free(pampd, pool, oid, index, acct);
+		if (pampd == NULL)
+			return;
+	}
+	if (is_ephemeral(pool)) {
+		page = zbud_free_and_delist((struct zbudref *)pampd,
+						true, &zsize, &zpages);
+		if (page)
+			zcache_eph_pageframes =
+			    atomic_dec_return(&zcache_eph_pageframes_atomic);
+		zcache_eph_zpages =
+		    atomic_sub_return(zpages, &zcache_eph_zpages_atomic);
+		zcache_eph_zbytes =
+		    atomic_long_sub_return(zsize, &zcache_eph_zbytes_atomic);
+		/* FIXME CONFIG_RAMSTER... check acct parameter? */
+	} else {
+		page = zbud_free_and_delist((struct zbudref *)pampd,
+						false, &zsize, &zpages);
+		if (page)
+			zcache_pers_pageframes =
+			    atomic_dec_return(&zcache_pers_pageframes_atomic);
+		zcache_pers_zpages =
+		     atomic_sub_return(zpages, &zcache_pers_zpages_atomic);
+		zcache_pers_zbytes =
+		    atomic_long_sub_return(zsize, &zcache_pers_zbytes_atomic);
+	}
+	if (!is_local_client(pool->client))
+		ramster_count_foreign_pages(is_ephemeral(pool), -1);
+	if (page)
+		zcache_free_page(page);
+}
+
+static struct tmem_pamops zcache_pamops = {
+	.create_finish = zcache_pampd_create_finish,
+	.get_data = zcache_pampd_get_data,
+	.get_data_and_free = zcache_pampd_get_data_and_free,
+	.free = zcache_pampd_free,
+};
+
+/*
+ * zcache compression/decompression and related per-cpu stuff
+ */
+
+static DEFINE_PER_CPU(unsigned char *, zcache_dstmem);
+#define ZCACHE_DSTMEM_ORDER 1
+
+static void zcache_compress(struct page *from, void **out_va, unsigned *out_len)
+{
+	int ret;
+	unsigned char *dmem = __get_cpu_var(zcache_dstmem);
+	char *from_va;
+
+	BUG_ON(!irqs_disabled());
+	/* no buffer or no compressor so can't compress */
+	BUG_ON(dmem == NULL);
+	*out_len = PAGE_SIZE << ZCACHE_DSTMEM_ORDER;
+	from_va = kmap_atomic(from);
+	mb();
+	ret = zcache_comp_op(ZCACHE_COMPOP_COMPRESS, from_va, PAGE_SIZE, dmem,
+				out_len);
+	BUG_ON(ret);
+	*out_va = dmem;
+	kunmap_atomic(from_va);
+}
+
+static int zcache_comp_cpu_up(int cpu)
+{
+	struct crypto_comp *tfm;
+
+	tfm = crypto_alloc_comp(zcache_comp_name, 0, 0);
+	if (IS_ERR(tfm))
+		return NOTIFY_BAD;
+	*per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = tfm;
+	return NOTIFY_OK;
+}
+
+static void zcache_comp_cpu_down(int cpu)
+{
+	struct crypto_comp *tfm;
+
+	tfm = *per_cpu_ptr(zcache_comp_pcpu_tfms, cpu);
+	crypto_free_comp(tfm);
+	*per_cpu_ptr(zcache_comp_pcpu_tfms, cpu) = NULL;
+}
+
+static int zcache_cpu_notifier(struct notifier_block *nb,
+				unsigned long action, void *pcpu)
+{
+	int ret, i, cpu = (long)pcpu;
+	struct zcache_preload *kp;
+
+	switch (action) {
+	case CPU_UP_PREPARE:
+		ret = zcache_comp_cpu_up(cpu);
+		if (ret != NOTIFY_OK) {
+			pr_err("%s: can't allocate compressor xform\n",
+				namestr);
+			return ret;
+		}
+		per_cpu(zcache_dstmem, cpu) = (void *)__get_free_pages(
+			GFP_KERNEL | __GFP_REPEAT, ZCACHE_DSTMEM_ORDER);
+		if (ramster_enabled)
+			ramster_cpu_up(cpu);
+		break;
+	case CPU_DEAD:
+	case CPU_UP_CANCELED:
+		zcache_comp_cpu_down(cpu);
+		free_pages((unsigned long)per_cpu(zcache_dstmem, cpu),
+			ZCACHE_DSTMEM_ORDER);
+		per_cpu(zcache_dstmem, cpu) = NULL;
+		kp = &per_cpu(zcache_preloads, cpu);
+		for (i = 0; i < ARRAY_SIZE(kp->objnodes); i++) {
+			if (kp->objnodes[i])
+				kmem_cache_free(zcache_objnode_cache,
+						kp->objnodes[i]);
+		}
+		if (kp->obj) {
+			kmem_cache_free(zcache_obj_cache, kp->obj);
+			kp->obj = NULL;
+		}
+		if (ramster_enabled)
+			ramster_cpu_down(cpu);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block zcache_cpu_notifier_block = {
+	.notifier_call = zcache_cpu_notifier
+};
+
+/*
+ * The following code interacts with the zbud eviction and zbud
+ * zombify code to access LRU pages
+ */
+
+static struct page *zcache_evict_eph_pageframe(void)
+{
+	struct page *page;
+	unsigned int zsize = 0, zpages = 0;
+
+	page = zbud_evict_pageframe_lru(&zsize, &zpages);
+	if (page == NULL)
+		goto out;
+	zcache_eph_zbytes = atomic_long_sub_return(zsize,
+					&zcache_eph_zbytes_atomic);
+	zcache_eph_zpages = atomic_sub_return(zpages,
+					&zcache_eph_zpages_atomic);
+	zcache_evicted_eph_zpages++;
+	zcache_eph_pageframes =
+		atomic_dec_return(&zcache_eph_pageframes_atomic);
+	zcache_evicted_eph_pageframes++;
+out:
+	return page;
+}
+
+static void unswiz(struct tmem_oid oid, u32 index,
+				unsigned *type, pgoff_t *offset);
+#ifdef FRONTSWAP_HAS_UNUSE
+/*
+ *  Choose an LRU persistent pageframe and attempt to "unuse" it by
+ *  calling frontswap_unuse on both zpages.
+ *
+ *  This is work-in-progress.
+ */
+
+static int zcache_frontswap_unuse(void)
+{
+	struct tmem_handle th[2];
+	int ret = -ENOMEM;
+	int nzbuds, unuse_ret;
+	unsigned type;
+	struct page *newpage1 = NULL, *newpage2 = NULL;
+	struct page *evictpage1 = NULL, *evictpage2 = NULL;
+	pgoff_t offset;
+
+	newpage1 = alloc_page(ZCACHE_GFP_MASK);
+	newpage2 = alloc_page(ZCACHE_GFP_MASK);
+	if (newpage1 == NULL)
+		evictpage1 = zcache_evict_eph_pageframe();
+	if (newpage2 == NULL)
+		evictpage2 = zcache_evict_eph_pageframe();
+	if (evictpage1 == NULL || evictpage2 == NULL)
+		goto free_and_out;
+	/* ok, we have two pages pre-allocated */
+	nzbuds = zbud_make_zombie_lru(&th[0], NULL, NULL, false);
+	if (nzbuds == 0) {
+		ret = -ENOENT;
+		goto free_and_out;
+	}
+	unswiz(th[0].oid, th[0].index, &type, &offset);
+	unuse_ret = frontswap_unuse(type, offset,
+				newpage1 != NULL ? newpage1 : evictpage1,
+				ZCACHE_GFP_MASK);
+	if (unuse_ret != 0)
+		goto free_and_out;
+	else if (evictpage1 != NULL)
+		zcache_unacct_page();
+	newpage1 = NULL;
+	evictpage1 = NULL;
+	if (nzbuds == 2) {
+		unswiz(th[1].oid, th[1].index, &type, &offset);
+		unuse_ret = frontswap_unuse(type, offset,
+				newpage2 != NULL ? newpage2 : evictpage2,
+				ZCACHE_GFP_MASK);
+		if (unuse_ret != 0) {
+			goto free_and_out;
+		} else if (evictpage2 != NULL) {
+			zcache_unacct_page();
+		}
+	}
+	ret = 0;
+	goto out;
+
+free_and_out:
+	if (newpage1 != NULL)
+		__free_page(newpage1);
+	if (newpage2 != NULL)
+		__free_page(newpage2);
+	if (evictpage1 != NULL)
+		zcache_free_page(evictpage1);
+	if (evictpage2 != NULL)
+		zcache_free_page(evictpage2);
+out:
+	return ret;
+}
+#endif
+
+/*
+ * When zcache is disabled ("frozen"), pools can be created and destroyed,
+ * but all puts (and thus all other operations that require memory allocation)
+ * must fail.  If zcache is unfrozen, accepts puts, then frozen again,
+ * data consistency requires all puts while frozen to be converted into
+ * flushes.
+ */
+static bool zcache_freeze;
+
+/*
+ * This zcache shrinker interface reduces the number of ephemeral pageframes
+ * used by zcache to approximately the same as the total number of LRU_FILE
+ * pageframes in use.
+ */
+static int shrink_zcache_memory(struct shrinker *shrink,
+				struct shrink_control *sc)
+{
+	static bool in_progress;
+	int ret = -1;
+	int nr = sc->nr_to_scan;
+	int nr_evict = 0;
+	int nr_unuse = 0;
+	struct page *page;
+	int unuse_ret;
+
+	if (nr <= 0)
+		goto skip_evict;
+
+	/* don't allow more than one eviction thread at a time */
+	if (in_progress)
+		goto skip_evict;
+
+	in_progress = true;
+
+	/* we are going to ignore nr, and target a different value */
+	zcache_last_active_file_pageframes =
+		global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE);
+	zcache_last_inactive_file_pageframes =
+		global_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE);
+	nr_evict = zcache_eph_pageframes - zcache_last_active_file_pageframes +
+		zcache_last_inactive_file_pageframes;
+	while (nr_evict-- > 0) {
+		page = zcache_evict_eph_pageframe();
+		if (page == NULL)
+			break;
+		zcache_free_page(page);
+	}
+
+	zcache_last_active_anon_pageframes =
+		global_page_state(NR_LRU_BASE + LRU_ACTIVE_ANON);
+	zcache_last_inactive_anon_pageframes =
+		global_page_state(NR_LRU_BASE + LRU_INACTIVE_ANON);
+	nr_unuse = zcache_pers_pageframes - zcache_last_active_anon_pageframes +
+		zcache_last_inactive_anon_pageframes;
+#ifdef FRONTSWAP_HAS_UNUSE
+	/* rate limit for testing */
+	if (nr_unuse > 32)
+		nr_unuse = 32;
+	while (nr_unuse-- > 0) {
+		unuse_ret = zcache_frontswap_unuse();
+		if (unuse_ret == -ENOMEM)
+			break;
+	}
+#endif
+	in_progress = false;
+
+skip_evict:
+	/* resample: has changed, but maybe not all the way yet */
+	zcache_last_active_file_pageframes =
+		global_page_state(NR_LRU_BASE + LRU_ACTIVE_FILE);
+	zcache_last_inactive_file_pageframes =
+		global_page_state(NR_LRU_BASE + LRU_INACTIVE_FILE);
+	ret = zcache_eph_pageframes - zcache_last_active_file_pageframes +
+		zcache_last_inactive_file_pageframes;
+	if (ret < 0)
+		ret = 0;
+	return ret;
+}
+
+static struct shrinker zcache_shrinker = {
+	.shrink = shrink_zcache_memory,
+	.seeks = DEFAULT_SEEKS,
+};
+
+/*
+ * zcache shims between cleancache/frontswap ops and tmem
+ */
+
+/* FIXME rename these core routines to zcache_tmemput etc? */
+int zcache_put_page(int cli_id, int pool_id, struct tmem_oid *oidp,
+				uint32_t index, void *page,
+				unsigned int size, bool raw, int ephemeral)
+{
+	struct tmem_pool *pool;
+	struct tmem_handle th;
+	int ret = -1;
+	void *pampd = NULL;
+
+	BUG_ON(!irqs_disabled());
+	pool = zcache_get_pool_by_id(cli_id, pool_id);
+	if (unlikely(pool == NULL))
+		goto out;
+	if (!zcache_freeze) {
+		ret = 0;
+		th.client_id = cli_id;
+		th.pool_id = pool_id;
+		th.oid = *oidp;
+		th.index = index;
+		pampd = zcache_pampd_create((char *)page, size, raw,
+				ephemeral, &th);
+		if (pampd == NULL) {
+			ret = -ENOMEM;
+			if (ephemeral)
+				zcache_failed_eph_puts++;
+			else
+				zcache_failed_pers_puts++;
+		} else {
+			if (ramster_enabled)
+				ramster_do_preload_flnode(pool);
+			ret = tmem_put(pool, oidp, index, 0, pampd);
+			if (ret < 0)
+				BUG();
+		}
+		zcache_put_pool(pool);
+	} else {
+		zcache_put_to_flush++;
+		if (ramster_enabled)
+			ramster_do_preload_flnode(pool);
+		if (atomic_read(&pool->obj_count) > 0)
+			/* the put fails whether the flush succeeds or not */
+			(void)tmem_flush_page(pool, oidp, index);
+		zcache_put_pool(pool);
+	}
+out:
+	return ret;
+}
+
+int zcache_get_page(int cli_id, int pool_id, struct tmem_oid *oidp,
+				uint32_t index, void *page,
+				size_t *sizep, bool raw, int get_and_free)
+{
+	struct tmem_pool *pool;
+	int ret = -1;
+	bool eph;
+
+	if (!raw) {
+		BUG_ON(irqs_disabled());
+		BUG_ON(in_softirq());
+	}
+	pool = zcache_get_pool_by_id(cli_id, pool_id);
+	eph = is_ephemeral(pool);
+	if (likely(pool != NULL)) {
+		if (atomic_read(&pool->obj_count) > 0)
+			ret = tmem_get(pool, oidp, index, (char *)(page),
+					sizep, raw, get_and_free);
+		zcache_put_pool(pool);
+	}
+	WARN_ONCE((!is_ephemeral(pool) && (ret != 0)),
+			"zcache_get fails on persistent pool, "
+			"bad things are very likely to happen soon\n");
+#ifdef RAMSTER_TESTING
+	if (ret != 0 && ret != -1 && !(ret == -EINVAL && is_ephemeral(pool)))
+		pr_err("TESTING zcache_get tmem_get returns ret=%d\n", ret);
+#endif
+	return ret;
+}
+
+int zcache_flush_page(int cli_id, int pool_id,
+				struct tmem_oid *oidp, uint32_t index)
+{
+	struct tmem_pool *pool;
+	int ret = -1;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	zcache_flush_total++;
+	pool = zcache_get_pool_by_id(cli_id, pool_id);
+	if (ramster_enabled)
+		ramster_do_preload_flnode(pool);
+	if (likely(pool != NULL)) {
+		if (atomic_read(&pool->obj_count) > 0)
+			ret = tmem_flush_page(pool, oidp, index);
+		zcache_put_pool(pool);
+	}
+	if (ret >= 0)
+		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);
+	if (ramster_enabled)
+		ramster_do_preload_flnode(pool);
+	if (likely(pool != NULL)) {
+		if (atomic_read(&pool->obj_count) > 0)
+			ret = tmem_flush_object(pool, oidp);
+		zcache_put_pool(pool);
+	}
+	if (ret >= 0)
+		zcache_flobj_found++;
+	local_irq_restore(flags);
+	return ret;
+}
+
+static int zcache_client_destroy_pool(int cli_id, int pool_id)
+{
+	struct tmem_pool *pool = NULL;
+	struct zcache_client *cli = NULL;
+	int ret = -1;
+
+	if (pool_id < 0)
+		goto out;
+	if (cli_id == LOCAL_CLIENT)
+		cli = &zcache_host;
+	else if ((unsigned int)cli_id < MAX_CLIENTS)
+		cli = &zcache_clients[cli_id];
+	if (cli == NULL)
+		goto out;
+	atomic_inc(&cli->refcount);
+	pool = cli->tmem_pools[pool_id];
+	if (pool == NULL)
+		goto out;
+	cli->tmem_pools[pool_id] = NULL;
+	/* wait for pool activity on other cpus to quiesce */
+	while (atomic_read(&pool->refcount) != 0)
+		;
+	atomic_dec(&cli->refcount);
+	local_bh_disable();
+	ret = tmem_destroy_pool(pool);
+	local_bh_enable();
+	kfree(pool);
+	if (cli_id == LOCAL_CLIENT)
+		pr_info("%s: destroyed local pool id=%d\n", namestr, pool_id);
+	else
+		pr_info("%s: destroyed pool id=%d, client=%d\n",
+				namestr, pool_id, cli_id);
+out:
+	return ret;
+}
+
+int zcache_new_pool(uint16_t cli_id, uint32_t flags)
+{
+	int poolid = -1;
+	struct tmem_pool *pool;
+	struct zcache_client *cli = NULL;
+
+	if (cli_id == LOCAL_CLIENT)
+		cli = &zcache_host;
+	else if ((unsigned int)cli_id < MAX_CLIENTS)
+		cli = &zcache_clients[cli_id];
+	if (cli == NULL)
+		goto out;
+	atomic_inc(&cli->refcount);
+	pool = kmalloc(sizeof(struct tmem_pool), GFP_ATOMIC);
+	if (pool == NULL) {
+		pr_info("%s: pool creation failed: out of memory\n", namestr);
+		goto out;
+	}
+
+	for (poolid = 0; poolid < MAX_POOLS_PER_CLIENT; poolid++)
+		if (cli->tmem_pools[poolid] == NULL)
+			break;
+	if (poolid >= MAX_POOLS_PER_CLIENT) {
+		pr_info("%s: pool creation failed: max exceeded\n", namestr);
+		kfree(pool);
+		poolid = -1;
+		goto out;
+	}
+	atomic_set(&pool->refcount, 0);
+	pool->client = cli;
+	pool->pool_id = poolid;
+	tmem_new_pool(pool, flags);
+	cli->tmem_pools[poolid] = pool;
+	if (cli_id == LOCAL_CLIENT)
+		pr_info("%s: created %s local tmem pool, id=%d\n", namestr,
+			flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
+			poolid);
+	else
+		pr_info("%s: created %s tmem pool, id=%d, client=%d\n", namestr,
+			flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
+			poolid, cli_id);
+out:
+	if (cli != NULL)
+		atomic_dec(&cli->refcount);
+	return poolid;
+}
+
+static int zcache_local_new_pool(uint32_t flags)
+{
+	return zcache_new_pool(LOCAL_CLIENT, flags);
+}
+
+int zcache_autocreate_pool(int cli_id, int pool_id, bool eph)
+{
+	struct tmem_pool *pool;
+	struct zcache_client *cli = NULL;
+	uint32_t flags = eph ? 0 : TMEM_POOL_PERSIST;
+	int ret = -1;
+
+	BUG_ON(!ramster_enabled);
+	if (cli_id == LOCAL_CLIENT)
+		goto out;
+	if (pool_id >= MAX_POOLS_PER_CLIENT)
+		goto out;
+	else if ((unsigned int)cli_id < MAX_CLIENTS)
+		cli = &zcache_clients[cli_id];
+	if ((eph && disable_cleancache) || (!eph && disable_frontswap)) {
+		pr_err("zcache_autocreate_pool: pool type disabled\n");
+		goto out;
+	}
+	if (!cli->allocated) {
+		if (zcache_new_client(cli_id)) {
+			pr_err("zcache_autocreate_pool: can't create client\n");
+			goto out;
+		}
+		cli = &zcache_clients[cli_id];
+	}
+	atomic_inc(&cli->refcount);
+	pool = cli->tmem_pools[pool_id];
+	if (pool != NULL) {
+		if (pool->persistent && eph) {
+			pr_err("zcache_autocreate_pool: type mismatch\n");
+			goto out;
+		}
+		ret = 0;
+		goto out;
+	}
+	pool = kmalloc(sizeof(struct tmem_pool), GFP_KERNEL);
+	if (pool == NULL) {
+		pr_info("%s: pool creation failed: out of memory\n", namestr);
+		goto out;
+	}
+	atomic_set(&pool->refcount, 0);
+	pool->client = cli;
+	pool->pool_id = pool_id;
+	tmem_new_pool(pool, flags);
+	cli->tmem_pools[pool_id] = pool;
+	pr_info("%s: AUTOcreated %s tmem poolid=%d, for remote client=%d\n",
+		namestr, flags & TMEM_POOL_PERSIST ? "persistent" : "ephemeral",
+		pool_id, cli_id);
+	ret = 0;
+out:
+	if (cli != NULL)
+		atomic_dec(&cli->refcount);
+	return ret;
+}
+
+/**********
+ * Two kernel functionalities currently can be layered on top of tmem.
+ * These are "cleancache" which is used as a second-chance cache for clean
+ * page cache pages; and "frontswap" which is used for swap pages
+ * to avoid writes to disk.  A generic "shim" is provided here for each
+ * to translate in-kernel semantics to zcache semantics.
+ */
+
+static void zcache_cleancache_put_page(int pool_id,
+					struct cleancache_filekey key,
+					pgoff_t index, struct page *page)
+{
+	u32 ind = (u32) index;
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+	if (!disable_cleancache_ignore_nonactive && !PageWasActive(page)) {
+		zcache_eph_nonactive_puts_ignored++;
+		return;
+	}
+	if (likely(ind == index))
+		(void)zcache_put_page(LOCAL_CLIENT, pool_id, &oid, index,
+					page, PAGE_SIZE, false, 1);
+}
+
+static int zcache_cleancache_get_page(int pool_id,
+					struct cleancache_filekey key,
+					pgoff_t index, struct page *page)
+{
+	u32 ind = (u32) index;
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+	size_t size;
+	int ret = -1;
+
+	if (likely(ind == index)) {
+		ret = zcache_get_page(LOCAL_CLIENT, pool_id, &oid, index,
+					page, &size, false, 0);
+		BUG_ON(ret >= 0 && size != PAGE_SIZE);
+		if (ret == 0)
+			SetPageWasActive(page);
+	}
+	return ret;
+}
+
+static void zcache_cleancache_flush_page(int pool_id,
+					struct cleancache_filekey key,
+					pgoff_t index)
+{
+	u32 ind = (u32) index;
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+	if (likely(ind == index))
+		(void)zcache_flush_page(LOCAL_CLIENT, pool_id, &oid, ind);
+}
+
+static void zcache_cleancache_flush_inode(int pool_id,
+					struct cleancache_filekey key)
+{
+	struct tmem_oid oid = *(struct tmem_oid *)&key;
+
+	(void)zcache_flush_object(LOCAL_CLIENT, pool_id, &oid);
+}
+
+static void zcache_cleancache_flush_fs(int pool_id)
+{
+	if (pool_id >= 0)
+		(void)zcache_client_destroy_pool(LOCAL_CLIENT, pool_id);
+}
+
+static int zcache_cleancache_init_fs(size_t pagesize)
+{
+	BUG_ON(sizeof(struct cleancache_filekey) !=
+				sizeof(struct tmem_oid));
+	BUG_ON(pagesize != PAGE_SIZE);
+	return zcache_local_new_pool(0);
+}
+
+static int zcache_cleancache_init_shared_fs(char *uuid, size_t pagesize)
+{
+	/* shared pools are unsupported and map to private */
+	BUG_ON(sizeof(struct cleancache_filekey) !=
+				sizeof(struct tmem_oid));
+	BUG_ON(pagesize != PAGE_SIZE);
+	return zcache_local_new_pool(0);
+}
+
+static struct cleancache_ops zcache_cleancache_ops = {
+	.put_page = zcache_cleancache_put_page,
+	.get_page = zcache_cleancache_get_page,
+	.invalidate_page = zcache_cleancache_flush_page,
+	.invalidate_inode = zcache_cleancache_flush_inode,
+	.invalidate_fs = zcache_cleancache_flush_fs,
+	.init_shared_fs = zcache_cleancache_init_shared_fs,
+	.init_fs = zcache_cleancache_init_fs
+};
+
+struct cleancache_ops zcache_cleancache_register_ops(void)
+{
+	struct cleancache_ops old_ops =
+		cleancache_register_ops(&zcache_cleancache_ops);
+
+	return old_ops;
+}
+
+/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
+static int zcache_frontswap_poolid __read_mostly = -1;
+
+/*
+ * Swizzling increases objects per swaptype, increasing tmem concurrency
+ * for heavy swaploads.  Later, larger nr_cpus -> larger SWIZ_BITS
+ * Setting SWIZ_BITS to 27 basically reconstructs the swap entry from
+ * frontswap_get_page(), but has side-effects. Hence using 8.
+ */
+#define SWIZ_BITS		8
+#define SWIZ_MASK		((1 << SWIZ_BITS) - 1)
+#define _oswiz(_type, _ind)	((_type << SWIZ_BITS) | (_ind & SWIZ_MASK))
+#define iswiz(_ind)		(_ind >> SWIZ_BITS)
+
+static inline struct tmem_oid oswiz(unsigned type, u32 ind)
+{
+	struct tmem_oid oid = { .oid = { 0 } };
+	oid.oid[0] = _oswiz(type, ind);
+	return oid;
+}
+
+static void unswiz(struct tmem_oid oid, u32 index,
+				unsigned *type, pgoff_t *offset)
+{
+	*type = (unsigned)(oid.oid[0] >> SWIZ_BITS);
+	*offset = (pgoff_t)((index << SWIZ_BITS) |
+			(oid.oid[0] & SWIZ_MASK));
+}
+
+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;
+	int unuse_ret;
+
+	BUG_ON(!PageLocked(page));
+	if (!disable_frontswap_ignore_nonactive && !PageWasActive(page)) {
+		zcache_pers_nonactive_puts_ignored++;
+		ret = -ERANGE;
+		goto out;
+	}
+	if (likely(ind64 == ind)) {
+		local_irq_save(flags);
+		ret = zcache_put_page(LOCAL_CLIENT, zcache_frontswap_poolid,
+					&oid, iswiz(ind),
+					page, PAGE_SIZE, false, 0);
+		local_irq_restore(flags);
+	}
+out:
+	return ret;
+}
+
+/* returns 0 if the page was successfully gotten from frontswap, -1 if
+ * was not present (should never happen!) */
+static int zcache_frontswap_get_page(unsigned type, pgoff_t offset,
+					struct page *page)
+{
+	u64 ind64 = (u64)offset;
+	u32 ind = (u32)offset;
+	struct tmem_oid oid = oswiz(type, ind);
+	size_t size;
+	int ret = -1, get_and_free;
+
+	if (frontswap_has_exclusive_gets)
+		get_and_free = 1;
+	else
+		get_and_free = -1;
+	BUG_ON(!PageLocked(page));
+	if (likely(ind64 == ind)) {
+		ret = zcache_get_page(LOCAL_CLIENT, zcache_frontswap_poolid,
+					&oid, iswiz(ind),
+					page, &size, false, get_and_free);
+		BUG_ON(ret >= 0 && size != PAGE_SIZE);
+	}
+	return ret;
+}
+
+/* flush a single page from frontswap */
+static void zcache_frontswap_flush_page(unsigned type, pgoff_t offset)
+{
+	u64 ind64 = (u64)offset;
+	u32 ind = (u32)offset;
+	struct tmem_oid oid = oswiz(type, ind);
+
+	if (likely(ind64 == ind))
+		(void)zcache_flush_page(LOCAL_CLIENT, zcache_frontswap_poolid,
+					&oid, iswiz(ind));
+}
+
+/* flush all pages from the passed swaptype */
+static void zcache_frontswap_flush_area(unsigned type)
+{
+	struct tmem_oid oid;
+	int ind;
+
+	for (ind = SWIZ_MASK; ind >= 0; ind--) {
+		oid = oswiz(type, ind);
+		(void)zcache_flush_object(LOCAL_CLIENT,
+						zcache_frontswap_poolid, &oid);
+	}
+}
+
+static void zcache_frontswap_init(unsigned ignored)
+{
+	/* a single tmem poolid is used for all frontswap "types" (swapfiles) */
+	if (zcache_frontswap_poolid < 0)
+		zcache_frontswap_poolid =
+			zcache_local_new_pool(TMEM_POOL_PERSIST);
+}
+
+static struct frontswap_ops zcache_frontswap_ops = {
+	.store = zcache_frontswap_put_page,
+	.load = zcache_frontswap_get_page,
+	.invalidate_page = zcache_frontswap_flush_page,
+	.invalidate_area = zcache_frontswap_flush_area,
+	.init = zcache_frontswap_init
+};
+
+struct frontswap_ops zcache_frontswap_register_ops(void)
+{
+	struct frontswap_ops old_ops =
+		frontswap_register_ops(&zcache_frontswap_ops);
+
+	return old_ops;
+}
+
+/*
+ * zcache initialization
+ * NOTE FOR NOW zcache or ramster MUST BE PROVIDED AS A KERNEL BOOT PARAMETER
+ * OR NOTHING HAPPENS!
+ */
+
+static int __init enable_zcache(char *s)
+{
+	zcache_enabled = 1;
+	return 1;
+}
+__setup("zcache", enable_zcache);
+
+static int __init enable_ramster(char *s)
+{
+	zcache_enabled = 1;
+#ifdef CONFIG_RAMSTER
+	ramster_enabled = 1;
+#endif
+	return 1;
+}
+__setup("ramster", enable_ramster);
+
+/* allow independent dynamic disabling of cleancache and frontswap */
+
+static int __init no_cleancache(char *s)
+{
+	disable_cleancache = 1;
+	return 1;
+}
+
+__setup("nocleancache", no_cleancache);
+
+static int __init no_frontswap(char *s)
+{
+	disable_frontswap = 1;
+	return 1;
+}
+
+__setup("nofrontswap", no_frontswap);
+
+static int __init no_frontswap_exclusive_gets(char *s)
+{
+	frontswap_has_exclusive_gets = false;
+	return 1;
+}
+
+__setup("nofrontswapexclusivegets", no_frontswap_exclusive_gets);
+
+static int __init no_frontswap_ignore_nonactive(char *s)
+{
+	disable_frontswap_ignore_nonactive = 1;
+	return 1;
+}
+
+__setup("nofrontswapignorenonactive", no_frontswap_ignore_nonactive);
+
+static int __init no_cleancache_ignore_nonactive(char *s)
+{
+	disable_cleancache_ignore_nonactive = 1;
+	return 1;
+}
+
+__setup("nocleancacheignorenonactive", no_cleancache_ignore_nonactive);
+
+static int __init enable_zcache_compressor(char *s)
+{
+	strncpy(zcache_comp_name, s, ZCACHE_COMP_NAME_SZ);
+	zcache_enabled = 1;
+	return 1;
+}
+__setup("zcache=", enable_zcache_compressor);
+
+
+static int __init zcache_comp_init(void)
+{
+	int ret = 0;
+
+	/* check crypto algorithm */
+	if (*zcache_comp_name != '\0') {
+		ret = crypto_has_comp(zcache_comp_name, 0, 0);
+		if (!ret)
+			pr_info("zcache: %s not supported\n",
+					zcache_comp_name);
+	}
+	if (!ret)
+		strcpy(zcache_comp_name, "lzo");
+	ret = crypto_has_comp(zcache_comp_name, 0, 0);
+	if (!ret) {
+		ret = 1;
+		goto out;
+	}
+	pr_info("zcache: using %s compressor\n", zcache_comp_name);
+
+	/* alloc percpu transforms */
+	ret = 0;
+	zcache_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
+	if (!zcache_comp_pcpu_tfms)
+		ret = 1;
+out:
+	return ret;
+}
+
+static int __init zcache_init(void)
+{
+	int ret = 0;
+
+	if (ramster_enabled) {
+		namestr = "ramster";
+		ramster_register_pamops(&zcache_pamops);
+	}
+#ifdef CONFIG_DEBUG_FS
+	zcache_debugfs_init();
+#endif
+	if (zcache_enabled) {
+		unsigned int cpu;
+
+		tmem_register_hostops(&zcache_hostops);
+		tmem_register_pamops(&zcache_pamops);
+		ret = register_cpu_notifier(&zcache_cpu_notifier_block);
+		if (ret) {
+			pr_err("%s: can't register cpu notifier\n", namestr);
+			goto out;
+		}
+		ret = zcache_comp_init();
+		if (ret) {
+			pr_err("%s: compressor initialization failed\n",
+				namestr);
+			goto out;
+		}
+		for_each_online_cpu(cpu) {
+			void *pcpu = (void *)(long)cpu;
+			zcache_cpu_notifier(&zcache_cpu_notifier_block,
+				CPU_UP_PREPARE, pcpu);
+		}
+	}
+	zcache_objnode_cache = kmem_cache_create("zcache_objnode",
+				sizeof(struct tmem_objnode), 0, 0, NULL);
+	zcache_obj_cache = kmem_cache_create("zcache_obj",
+				sizeof(struct tmem_obj), 0, 0, NULL);
+	ret = zcache_new_client(LOCAL_CLIENT);
+	if (ret) {
+		pr_err("%s: can't create client\n", namestr);
+		goto out;
+	}
+	zbud_init();
+	if (zcache_enabled && !disable_cleancache) {
+		struct cleancache_ops old_ops;
+
+		register_shrinker(&zcache_shrinker);
+		old_ops = zcache_cleancache_register_ops();
+		pr_info("%s: cleancache enabled using kernel transcendent "
+			"memory and compression buddies\n", namestr);
+#ifdef ZCACHE_DEBUG
+		pr_info("%s: cleancache: ignorenonactive = %d\n",
+			namestr, !disable_cleancache_ignore_nonactive);
+#endif
+		if (old_ops.init_fs != NULL)
+			pr_warn("%s: cleancache_ops overridden\n", namestr);
+	}
+	if (zcache_enabled && !disable_frontswap) {
+		struct frontswap_ops old_ops;
+
+		old_ops = zcache_frontswap_register_ops();
+		if (frontswap_has_exclusive_gets)
+			frontswap_tmem_exclusive_gets(true);
+		pr_info("%s: frontswap enabled using kernel transcendent "
+			"memory and compression buddies\n", namestr);
+#ifdef ZCACHE_DEBUG
+		pr_info("%s: frontswap: excl gets = %d active only = %d\n",
+			namestr, frontswap_has_exclusive_gets,
+			!disable_frontswap_ignore_nonactive);
+#endif
+		if (old_ops.init != NULL)
+			pr_warn("%s: frontswap_ops overridden\n", namestr);
+	}
+	if (ramster_enabled)
+		ramster_init(!disable_cleancache, !disable_frontswap,
+				frontswap_has_exclusive_gets);
+out:
+	return ret;
+}
+
+late_initcall(zcache_init);