Commit daa6afa6 authored by Dan Magenheimer's avatar Dan Magenheimer Committed by Greg Kroah-Hartman
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staging: zcache: in-kernel tmem code 



[PATCH V2 1/3] drivers/staging: zcache: in-kernel tmem code

Transcendent memory ("tmem") is a clean API/ABI that provides
for an efficient address translation and a set of highly
concurrent access methods to copy data between a page-oriented
data source (e.g. cleancache or frontswap) and a page-addressable
memory ("PAM") data store.  Of critical importance, the PAM data
store is of unknown (and possibly varying) size so any individual
access may succeed or fail as defined by the API/ABI.

Tmem exports a basic set of access methods (e.g. put, get,
flush, flush object, new pool, and destroy pool) which are
normally called from a "host" (e.g. zcache).

To be functional, two sets of "ops" must be registered by the
host, one to provide "host services" (memory allocation) and
one to provide page-addressable memory ("PAM") hooks.

Tmem supports one or more "clients", each which can provide
a set of "pools" to partition pages.  Each pool contains
a set of "objects"; each object holds pointers to some number
of PAM page descriptors ("pampd"), indexed by an "index" number.
This triple <pool id, object id, index> is sometimes referred
to as a "handle".  Tmem's primary function is to essentially
provide address translation of handles into pampds and move
data appropriately.

As an example, for cleancache, a pool maps to a filesystem,
an object maps to a file, and the index is the page offset
into the file.  And in this patch, zcache is the host and
each PAM descriptor points to a compressed page of data.

Tmem supports two kinds of pages: "ephemeral" and "persistent".
Ephemeral pages may be asynchronously reclaimed "bottoms up"
so the data structures and concurrency model must allow for
this.  For example, each pampd must retain sufficient information
to invalidate tmem's handle-to-pampd translation.
its containing object so that, on reclaim, all tmem data
structures can be made consistent.

Signed-off-by: default avatarDan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent ea707584

drivers/staging/zcache/tmem.c

0 → 100644
+710 −0
Original line number Diff line number Diff line 
/*

 * In-kernel transcendent memory (generic implementation)

 *

 * Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp.

 *

 * The primary purpose of Transcedent Memory ("tmem") is to map object-oriented

 * "handles" (triples containing a pool id, and object id, and an index), to

 * pages in a page-accessible memory (PAM).  Tmem references the PAM pages via

 * an abstract "pampd" (PAM page-descriptor), which can be operated on by a

 * set of functions (pamops).  Each pampd contains some representation of

 * PAGE_SIZE bytes worth of data. Tmem must support potentially millions of

 * pages and must be able to insert, find, and delete these pages at a

 * potential frequency of thousands per second concurrently across many CPUs,

 * (and, if used with KVM, across many vcpus across many guests).

 * Tmem is tracked with a hierarchy of data structures, organized by

 * the elements in a handle-tuple: pool_id, object_id, and page index.

 * One or more "clients" (e.g. guests) each provide one or more tmem_pools.

 * Each pool, contains a hash table of rb_trees of tmem_objs.  Each

 * tmem_obj contains a radix-tree-like tree of pointers, with intermediate

 * nodes called tmem_objnodes.  Each leaf pointer in this tree points to

 * a pampd, which is accessible only through a small set of callbacks

 * registered by the PAM implementation (see tmem_register_pamops). Tmem

 * does all memory allocation via a set of callbacks registered by the tmem

 * host implementation (e.g. see tmem_register_hostops).

 */



#include <linux/list.h>

#include <linux/spinlock.h>

#include <linux/atomic.h>



#include "tmem.h"



/* data structure sentinels used for debugging... see tmem.h */

#define POOL_SENTINEL 0x87658765

#define OBJ_SENTINEL 0x12345678

#define OBJNODE_SENTINEL 0xfedcba09



/*

 * A tmem host implementation must use this function to register callbacks

 * for memory allocation.

 */

static struct tmem_hostops tmem_hostops;



static void tmem_objnode_tree_init(void);



void tmem_register_hostops(struct tmem_hostops *m)

{

	tmem_objnode_tree_init();

	tmem_hostops = *m;

}



/*

 * A tmem host implementation must use this function to register

 * callbacks for a page-accessible memory (PAM) implementation

 */

static struct tmem_pamops tmem_pamops;



void tmem_register_pamops(struct tmem_pamops *m)

{

	tmem_pamops = *m;

}



/*

 * Oid's are potentially very sparse and tmem_objs may have an indeterminately

 * short life, being added and deleted at a relatively high frequency.

 * So an rb_tree is an ideal data structure to manage tmem_objs.  But because

 * of the potentially huge number of tmem_objs, each pool manages a hashtable

 * of rb_trees to reduce search, insert, delete, and rebalancing time.

 * Each hashbucket also has a lock to manage concurrent access.

 *

 * The following routines manage tmem_objs.  When any tmem_obj is accessed,

 * the hashbucket lock must be held.

 */



/* searches for object==oid in pool, returns locked object if found */

static struct tmem_obj *tmem_obj_find(struct tmem_hashbucket *hb,

					struct tmem_oid *oidp)

{

	struct rb_node *rbnode;

	struct tmem_obj *obj;



	rbnode = hb->obj_rb_root.rb_node;

	while (rbnode) {

		BUG_ON(RB_EMPTY_NODE(rbnode));

		obj = rb_entry(rbnode, struct tmem_obj, rb_tree_node);

		switch (tmem_oid_compare(oidp, &obj->oid)) {

		case 0: /* equal */

			goto out;

		case -1:

			rbnode = rbnode->rb_left;

			break;

		case 1:

			rbnode = rbnode->rb_right;

			break;

		}

	}

	obj = NULL;

out:

	return obj;

}



static void tmem_pampd_destroy_all_in_obj(struct tmem_obj *);



/* free an object that has no more pampds in it */

static void tmem_obj_free(struct tmem_obj *obj, struct tmem_hashbucket *hb)

{

	struct tmem_pool *pool;



	BUG_ON(obj == NULL);

	ASSERT_SENTINEL(obj, OBJ);

	BUG_ON(obj->pampd_count > 0);

	pool = obj->pool;

	BUG_ON(pool == NULL);

	if (obj->objnode_tree_root != NULL) /* may be "stump" with no leaves */

		tmem_pampd_destroy_all_in_obj(obj);

	BUG_ON(obj->objnode_tree_root != NULL);

	BUG_ON((long)obj->objnode_count != 0);

	atomic_dec(&pool->obj_count);

	BUG_ON(atomic_read(&pool->obj_count) < 0);

	INVERT_SENTINEL(obj, OBJ);

	obj->pool = NULL;

	tmem_oid_set_invalid(&obj->oid);

	rb_erase(&obj->rb_tree_node, &hb->obj_rb_root);

}



/*

 * initialize, and insert an tmem_object_root (called only if find failed)

 */

static void tmem_obj_init(struct tmem_obj *obj, struct tmem_hashbucket *hb,

					struct tmem_pool *pool,

					struct tmem_oid *oidp)

{

	struct rb_root *root = &hb->obj_rb_root;

	struct rb_node **new = &(root->rb_node), *parent = NULL;

	struct tmem_obj *this;



	BUG_ON(pool == NULL);

	atomic_inc(&pool->obj_count);

	obj->objnode_tree_height = 0;

	obj->objnode_tree_root = NULL;

	obj->pool = pool;

	obj->oid = *oidp;

	obj->objnode_count = 0;

	obj->pampd_count = 0;

	SET_SENTINEL(obj, OBJ);

	while (*new) {

		BUG_ON(RB_EMPTY_NODE(*new));

		this = rb_entry(*new, struct tmem_obj, rb_tree_node);

		parent = *new;

		switch (tmem_oid_compare(oidp, &this->oid)) {

		case 0:

			BUG(); /* already present; should never happen! */

			break;

		case -1:

			new = &(*new)->rb_left;

			break;

		case 1:

			new = &(*new)->rb_right;

			break;

		}

	}

	rb_link_node(&obj->rb_tree_node, parent, new);

	rb_insert_color(&obj->rb_tree_node, root);

}



/*

 * Tmem is managed as a set of tmem_pools with certain attributes, such as

 * "ephemeral" vs "persistent".  These attributes apply to all tmem_objs

 * and all pampds that belong to a tmem_pool.  A tmem_pool is created

 * or deleted relatively rarely (for example, when a filesystem is

 * mounted or unmounted.

 */



/* flush all data from a pool and, optionally, free it */

static void tmem_pool_flush(struct tmem_pool *pool, bool destroy)

{

	struct rb_node *rbnode;

	struct tmem_obj *obj;

	struct tmem_hashbucket *hb = &pool->hashbucket[0];

	int i;



	BUG_ON(pool == NULL);

	for (i = 0; i < TMEM_HASH_BUCKETS; i++, hb++) {

		spin_lock(&hb->lock);

		rbnode = rb_first(&hb->obj_rb_root);

		while (rbnode != NULL) {

			obj = rb_entry(rbnode, struct tmem_obj, rb_tree_node);

			rbnode = rb_next(rbnode);

			tmem_pampd_destroy_all_in_obj(obj);

			tmem_obj_free(obj, hb);

			(*tmem_hostops.obj_free)(obj, pool);

		}

		spin_unlock(&hb->lock);

	}

	if (destroy)

		list_del(&pool->pool_list);

}



/*

 * A tmem_obj contains a radix-tree-like tree in which the intermediate

 * nodes are called tmem_objnodes.  (The kernel lib/radix-tree.c implementation

 * is very specialized and tuned for specific uses and is not particularly

 * suited for use from this code, though some code from the core algorithms has

 * been reused, thus the copyright notices below).  Each tmem_objnode contains

 * a set of pointers which point to either a set of intermediate tmem_objnodes

 * or a set of of pampds.

 *

 * Portions Copyright (C) 2001 Momchil Velikov

 * Portions Copyright (C) 2001 Christoph Hellwig

 * Portions Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>

 */



struct tmem_objnode_tree_path {

	struct tmem_objnode *objnode;

	int offset;

};



/* objnode height_to_maxindex translation */

static unsigned long tmem_objnode_tree_h2max[OBJNODE_TREE_MAX_PATH + 1];



static void tmem_objnode_tree_init(void)

{

	unsigned int ht, tmp;



	for (ht = 0; ht < ARRAY_SIZE(tmem_objnode_tree_h2max); ht++) {

		tmp = ht * OBJNODE_TREE_MAP_SHIFT;

		if (tmp >= OBJNODE_TREE_INDEX_BITS)

			tmem_objnode_tree_h2max[ht] = ~0UL;

		else

			tmem_objnode_tree_h2max[ht] =

			    (~0UL >> (OBJNODE_TREE_INDEX_BITS - tmp - 1)) >> 1;

	}

}



static struct tmem_objnode *tmem_objnode_alloc(struct tmem_obj *obj)

{

	struct tmem_objnode *objnode;



	ASSERT_SENTINEL(obj, OBJ);

	BUG_ON(obj->pool == NULL);

	ASSERT_SENTINEL(obj->pool, POOL);

	objnode = (*tmem_hostops.objnode_alloc)(obj->pool);

	if (unlikely(objnode == NULL))

		goto out;

	objnode->obj = obj;

	SET_SENTINEL(objnode, OBJNODE);

	memset(&objnode->slots, 0, sizeof(objnode->slots));

	objnode->slots_in_use = 0;

	obj->objnode_count++;

out:

	return objnode;

}



static void tmem_objnode_free(struct tmem_objnode *objnode)

{

	struct tmem_pool *pool;

	int i;



	BUG_ON(objnode == NULL);

	for (i = 0; i < OBJNODE_TREE_MAP_SIZE; i++)

		BUG_ON(objnode->slots[i] != NULL);

	ASSERT_SENTINEL(objnode, OBJNODE);

	INVERT_SENTINEL(objnode, OBJNODE);

	BUG_ON(objnode->obj == NULL);

	ASSERT_SENTINEL(objnode->obj, OBJ);

	pool = objnode->obj->pool;

	BUG_ON(pool == NULL);

	ASSERT_SENTINEL(pool, POOL);

	objnode->obj->objnode_count--;

	objnode->obj = NULL;

	(*tmem_hostops.objnode_free)(objnode, pool);

}



/*

 * lookup index in object and return associated pampd (or NULL if not found)

 */

static void *tmem_pampd_lookup_in_obj(struct tmem_obj *obj, uint32_t index)

{

	unsigned int height, shift;

	struct tmem_objnode **slot = NULL;



	BUG_ON(obj == NULL);

	ASSERT_SENTINEL(obj, OBJ);

	BUG_ON(obj->pool == NULL);

	ASSERT_SENTINEL(obj->pool, POOL);



	height = obj->objnode_tree_height;

	if (index > tmem_objnode_tree_h2max[obj->objnode_tree_height])

		goto out;

	if (height == 0 && obj->objnode_tree_root) {

		slot = &obj->objnode_tree_root;

		goto out;

	}

	shift = (height-1) * OBJNODE_TREE_MAP_SHIFT;

	slot = &obj->objnode_tree_root;

	while (height > 0) {

		if (*slot == NULL)

			goto out;

		slot = (struct tmem_objnode **)

			((*slot)->slots +

			 ((index >> shift) & OBJNODE_TREE_MAP_MASK));

		shift -= OBJNODE_TREE_MAP_SHIFT;

		height--;

	}

out:

	return slot != NULL ? *slot : NULL;

}



static int tmem_pampd_add_to_obj(struct tmem_obj *obj, uint32_t index,

					void *pampd)

{

	int ret = 0;

	struct tmem_objnode *objnode = NULL, *newnode, *slot;

	unsigned int height, shift;

	int offset = 0;



	/* if necessary, extend the tree to be higher  */

	if (index > tmem_objnode_tree_h2max[obj->objnode_tree_height]) {

		height = obj->objnode_tree_height + 1;

		if (index > tmem_objnode_tree_h2max[height])

			while (index > tmem_objnode_tree_h2max[height])

				height++;

		if (obj->objnode_tree_root == NULL) {

			obj->objnode_tree_height = height;

			goto insert;

		}

		do {

			newnode = tmem_objnode_alloc(obj);

			if (!newnode) {

				ret = -ENOMEM;

				goto out;

			}

			newnode->slots[0] = obj->objnode_tree_root;

			newnode->slots_in_use = 1;

			obj->objnode_tree_root = newnode;

			obj->objnode_tree_height++;

		} while (height > obj->objnode_tree_height);

	}

insert:

	slot = obj->objnode_tree_root;

	height = obj->objnode_tree_height;

	shift = (height-1) * OBJNODE_TREE_MAP_SHIFT;

	while (height > 0) {

		if (slot == NULL) {

			/* add a child objnode.  */

			slot = tmem_objnode_alloc(obj);

			if (!slot) {

				ret = -ENOMEM;

				goto out;

			}

			if (objnode) {



				objnode->slots[offset] = slot;

				objnode->slots_in_use++;

			} else

				obj->objnode_tree_root = slot;

		}

		/* go down a level */

		offset = (index >> shift) & OBJNODE_TREE_MAP_MASK;

		objnode = slot;

		slot = objnode->slots[offset];

		shift -= OBJNODE_TREE_MAP_SHIFT;

		height--;

	}

	BUG_ON(slot != NULL);

	if (objnode) {

		objnode->slots_in_use++;

		objnode->slots[offset] = pampd;

	} else

		obj->objnode_tree_root = pampd;

	obj->pampd_count++;

out:

	return ret;

}



static void *tmem_pampd_delete_from_obj(struct tmem_obj *obj, uint32_t index)

{

	struct tmem_objnode_tree_path path[OBJNODE_TREE_MAX_PATH + 1];

	struct tmem_objnode_tree_path *pathp = path;

	struct tmem_objnode *slot = NULL;

	unsigned int height, shift;

	int offset;



	BUG_ON(obj == NULL);

	ASSERT_SENTINEL(obj, OBJ);

	BUG_ON(obj->pool == NULL);

	ASSERT_SENTINEL(obj->pool, POOL);

	height = obj->objnode_tree_height;

	if (index > tmem_objnode_tree_h2max[height])

		goto out;

	slot = obj->objnode_tree_root;

	if (height == 0 && obj->objnode_tree_root) {

		obj->objnode_tree_root = NULL;

		goto out;

	}

	shift = (height - 1) * OBJNODE_TREE_MAP_SHIFT;

	pathp->objnode = NULL;

	do {

		if (slot == NULL)

			goto out;

		pathp++;

		offset = (index >> shift) & OBJNODE_TREE_MAP_MASK;

		pathp->offset = offset;

		pathp->objnode = slot;

		slot = slot->slots[offset];

		shift -= OBJNODE_TREE_MAP_SHIFT;

		height--;

	} while (height > 0);

	if (slot == NULL)

		goto out;

	while (pathp->objnode) {

		pathp->objnode->slots[pathp->offset] = NULL;

		pathp->objnode->slots_in_use--;

		if (pathp->objnode->slots_in_use) {

			if (pathp->objnode == obj->objnode_tree_root) {

				while (obj->objnode_tree_height > 0 &&

				  obj->objnode_tree_root->slots_in_use == 1 &&

				  obj->objnode_tree_root->slots[0]) {

					struct tmem_objnode *to_free =

						obj->objnode_tree_root;



					obj->objnode_tree_root =

							to_free->slots[0];

					obj->objnode_tree_height--;

					to_free->slots[0] = NULL;

					to_free->slots_in_use = 0;

					tmem_objnode_free(to_free);

				}

			}

			goto out;

		}

		tmem_objnode_free(pathp->objnode); /* 0 slots used, free it */

		pathp--;

	}

	obj->objnode_tree_height = 0;

	obj->objnode_tree_root = NULL;



out:

	if (slot != NULL)

		obj->pampd_count--;

	BUG_ON(obj->pampd_count < 0);

	return slot;

}



/* recursively walk the objnode_tree destroying pampds and objnodes */

static void tmem_objnode_node_destroy(struct tmem_obj *obj,

					struct tmem_objnode *objnode,

					unsigned int ht)

{

	int i;



	if (ht == 0)

		return;

	for (i = 0; i < OBJNODE_TREE_MAP_SIZE; i++) {

		if (objnode->slots[i]) {

			if (ht == 1) {

				obj->pampd_count--;

				(*tmem_pamops.free)(objnode->slots[i],

								obj->pool);

				objnode->slots[i] = NULL;

				continue;

			}

			tmem_objnode_node_destroy(obj, objnode->slots[i], ht-1);

			tmem_objnode_free(objnode->slots[i]);

			objnode->slots[i] = NULL;

		}

	}

}



static void tmem_pampd_destroy_all_in_obj(struct tmem_obj *obj)

{

	if (obj->objnode_tree_root == NULL)

		return;

	if (obj->objnode_tree_height == 0) {

		obj->pampd_count--;

		(*tmem_pamops.free)(obj->objnode_tree_root, obj->pool);

	} else {

		tmem_objnode_node_destroy(obj, obj->objnode_tree_root,

					obj->objnode_tree_height);

		tmem_objnode_free(obj->objnode_tree_root);

		obj->objnode_tree_height = 0;

	}

	obj->objnode_tree_root = NULL;

}



/*

 * Tmem is operated on by a set of well-defined actions:

 * "put", "get", "flush", "flush_object", "new pool" and "destroy pool".

 * (The tmem ABI allows for subpages and exchanges but these operations

 * are not included in this implementation.)

 *

 * These "tmem core" operations are implemented in the following functions.

 */



/*

 * "Put" a page, e.g. copy a page from the kernel into newly allocated

 * PAM space (if such space is available).  Tmem_put is complicated by

 * a corner case: What if a page with matching handle already exists in

 * tmem?  To guarantee coherency, one of two actions is necessary: Either

 * the data for the page must be overwritten, or the page must be

 * "flushed" so that the data is not accessible to a subsequent "get".

 * Since these "duplicate puts" are relatively rare, this implementation

 * always flushes for simplicity.

 */

int tmem_put(struct tmem_pool *pool, struct tmem_oid *oidp, uint32_t index,

		struct page *page)

{

	struct tmem_obj *obj = NULL, *objfound = NULL, *objnew = NULL;

	void *pampd = NULL, *pampd_del = NULL;

	int ret = -ENOMEM;

	bool ephemeral;

	struct tmem_hashbucket *hb;



	ephemeral = is_ephemeral(pool);

	hb = &pool->hashbucket[tmem_oid_hash(oidp)];

	spin_lock(&hb->lock);

	obj = objfound = tmem_obj_find(hb, oidp);

	if (obj != NULL) {

		pampd = tmem_pampd_lookup_in_obj(objfound, index);

		if (pampd != NULL) {

			/* if found, is a dup put, flush the old one */

			pampd_del = tmem_pampd_delete_from_obj(obj, index);

			BUG_ON(pampd_del != pampd);

			(*tmem_pamops.free)(pampd, pool);

			if (obj->pampd_count == 0) {

				objnew = obj;

				objfound = NULL;

			}

			pampd = NULL;

		}

	} else {

		obj = objnew = (*tmem_hostops.obj_alloc)(pool);

		if (unlikely(obj == NULL)) {

			ret = -ENOMEM;

			goto out;

		}

		tmem_obj_init(obj, hb, pool, oidp);

	}

	BUG_ON(obj == NULL);

	BUG_ON(((objnew != obj) && (objfound != obj)) || (objnew == objfound));

	pampd = (*tmem_pamops.create)(obj->pool, &obj->oid, index, page);

	if (unlikely(pampd == NULL))

		goto free;

	ret = tmem_pampd_add_to_obj(obj, index, pampd);

	if (unlikely(ret == -ENOMEM))

		/* may have partially built objnode tree ("stump") */

		goto delete_and_free;

	goto out;



delete_and_free:

	(void)tmem_pampd_delete_from_obj(obj, index);

free:

	if (pampd)

		(*tmem_pamops.free)(pampd, pool);

	if (objnew) {

		tmem_obj_free(objnew, hb);

		(*tmem_hostops.obj_free)(objnew, pool);

	}

out:

	spin_unlock(&hb->lock);

	return ret;

}



/*

 * "Get" a page, e.g. if one can be found, copy the tmem page with the

 * matching handle from PAM space to the kernel.  By tmem definition,

 * when a "get" is successful on an ephemeral page, the page is "flushed",

 * and when a "get" is successful on a persistent page, the page is retained

 * in tmem.  Note that to preserve

 * coherency, "get" can never be skipped if tmem contains the data.

 * That is, if a get is done with a certain handle and fails, any

 * subsequent "get" must also fail (unless of course there is a

 * "put" done with the same handle).



 */

int tmem_get(struct tmem_pool *pool, struct tmem_oid *oidp,

				uint32_t index, struct page *page)

{

	struct tmem_obj *obj;

	void *pampd;

	bool ephemeral = is_ephemeral(pool);

	uint32_t ret = -1;

	struct tmem_hashbucket *hb;



	hb = &pool->hashbucket[tmem_oid_hash(oidp)];

	spin_lock(&hb->lock);

	obj = tmem_obj_find(hb, oidp);

	if (obj == NULL)

		goto out;

	ephemeral = is_ephemeral(pool);

	if (ephemeral)

		pampd = tmem_pampd_delete_from_obj(obj, index);

	else

		pampd = tmem_pampd_lookup_in_obj(obj, index);

	if (pampd == NULL)

		goto out;

	ret = (*tmem_pamops.get_data)(page, pampd, pool);

	if (ret < 0)

		goto out;

	if (ephemeral) {

		(*tmem_pamops.free)(pampd, pool);

		if (obj->pampd_count == 0) {

			tmem_obj_free(obj, hb);

			(*tmem_hostops.obj_free)(obj, pool);

			obj = NULL;

		}

	}

	ret = 0;

out:

	spin_unlock(&hb->lock);

	return ret;

}



/*

 * If a page in tmem matches the handle, "flush" this page from tmem such

 * that any subsequent "get" does not succeed (unless, of course, there

 * was another "put" with the same handle).

 */

int tmem_flush_page(struct tmem_pool *pool,

				struct tmem_oid *oidp, uint32_t index)

{

	struct tmem_obj *obj;

	void *pampd;

	int ret = -1;

	struct tmem_hashbucket *hb;



	hb = &pool->hashbucket[tmem_oid_hash(oidp)];

	spin_lock(&hb->lock);

	obj = tmem_obj_find(hb, oidp);

	if (obj == NULL)

		goto out;

	pampd = tmem_pampd_delete_from_obj(obj, index);

	if (pampd == NULL)

		goto out;

	(*tmem_pamops.free)(pampd, pool);

	if (obj->pampd_count == 0) {

		tmem_obj_free(obj, hb);

		(*tmem_hostops.obj_free)(obj, pool);

	}

	ret = 0;



out:

	spin_unlock(&hb->lock);

	return ret;

}



/*

 * "Flush" all pages in tmem matching this oid.

 */

int tmem_flush_object(struct tmem_pool *pool, struct tmem_oid *oidp)

{

	struct tmem_obj *obj;

	struct tmem_hashbucket *hb;

	int ret = -1;



	hb = &pool->hashbucket[tmem_oid_hash(oidp)];

	spin_lock(&hb->lock);

	obj = tmem_obj_find(hb, oidp);

	if (obj == NULL)

		goto out;

	tmem_pampd_destroy_all_in_obj(obj);

	tmem_obj_free(obj, hb);

	(*tmem_hostops.obj_free)(obj, pool);

	ret = 0;



out:

	spin_unlock(&hb->lock);

	return ret;

}



/*

 * "Flush" all pages (and tmem_objs) from this tmem_pool and disable

 * all subsequent access to this tmem_pool.

 */

int tmem_destroy_pool(struct tmem_pool *pool)

{

	int ret = -1;



	if (pool == NULL)

		goto out;

	tmem_pool_flush(pool, 1);

	ret = 0;

out:

	return ret;

}



static LIST_HEAD(tmem_global_pool_list);



/*

 * Create a new tmem_pool with the provided flag and return

 * a pool id provided by the tmem host implementation.

 */

void tmem_new_pool(struct tmem_pool *pool, uint32_t flags)

{

	int persistent = flags & TMEM_POOL_PERSIST;

	int shared = flags & TMEM_POOL_SHARED;

	struct tmem_hashbucket *hb = &pool->hashbucket[0];

	int i;



	for (i = 0; i < TMEM_HASH_BUCKETS; i++, hb++) {

		hb->obj_rb_root = RB_ROOT;

		spin_lock_init(&hb->lock);

	}

	INIT_LIST_HEAD(&pool->pool_list);

	atomic_set(&pool->obj_count, 0);

	SET_SENTINEL(pool, POOL);

	list_add_tail(&pool->pool_list, &tmem_global_pool_list);

	pool->persistent = persistent;

	pool->shared = shared;

}

drivers/staging/zcache/tmem.h

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