drivers/staging/zcache/tmem.c

   1 /*
   2  * In-kernel transcendent memory (generic implementation)
   3  *
   4  * Copyright (c) 2009-2011, Dan Magenheimer, Oracle Corp.
   5  *
   6  * The primary purpose of Transcedent Memory ("tmem") is to map object-oriented
   7  * "handles" (triples containing a pool id, and object id, and an index), to
   8  * pages in a page-accessible memory (PAM).  Tmem references the PAM pages via
   9  * an abstract "pampd" (PAM page-descriptor), which can be operated on by a
  10  * set of functions (pamops).  Each pampd contains some representation of
  11  * PAGE_SIZE bytes worth of data. Tmem must support potentially millions of
  12  * pages and must be able to insert, find, and delete these pages at a
  13  * potential frequency of thousands per second concurrently across many CPUs,
  14  * (and, if used with KVM, across many vcpus across many guests).
  15  * Tmem is tracked with a hierarchy of data structures, organized by
  16  * the elements in a handle-tuple: pool_id, object_id, and page index.
  17  * One or more "clients" (e.g. guests) each provide one or more tmem_pools.
  18  * Each pool, contains a hash table of rb_trees of tmem_objs.  Each
  19  * tmem_obj contains a radix-tree-like tree of pointers, with intermediate
  20  * nodes called tmem_objnodes.  Each leaf pointer in this tree points to
  21  * a pampd, which is accessible only through a small set of callbacks
  22  * registered by the PAM implementation (see tmem_register_pamops). Tmem
  23  * does all memory allocation via a set of callbacks registered by the tmem
  24  * host implementation (e.g. see tmem_register_hostops).
  25  */
  26
  27 #include <linux/list.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/atomic.h>
  30
  31 #include "tmem.h"
  32
  33 /* data structure sentinels used for debugging... see tmem.h */
  34 #define POOL_SENTINEL 0x87658765
  35 #define OBJ_SENTINEL 0x12345678
  36 #define OBJNODE_SENTINEL 0xfedcba09
  37
  38 /*
  39  * A tmem host implementation must use this function to register callbacks
  40  * for memory allocation.
  41  */
  42 static struct tmem_hostops tmem_hostops;
  43
  44 static void tmem_objnode_tree_init(void);
  45
  46 void tmem_register_hostops(struct tmem_hostops *m)
  47 {
  48         tmem_objnode_tree_init();
  49         tmem_hostops = *m;
  50 }
  51
  52 /*
  53  * A tmem host implementation must use this function to register
  54  * callbacks for a page-accessible memory (PAM) implementation
  55  */
  56 static struct tmem_pamops tmem_pamops;
  57
  58 void tmem_register_pamops(struct tmem_pamops *m)
  59 {
  60         tmem_pamops = *m;
  61 }
  62
  63 /*
  64  * Oid's are potentially very sparse and tmem_objs may have an indeterminately
  65  * short life, being added and deleted at a relatively high frequency.
  66  * So an rb_tree is an ideal data structure to manage tmem_objs.  But because
  67  * of the potentially huge number of tmem_objs, each pool manages a hashtable
  68  * of rb_trees to reduce search, insert, delete, and rebalancing time.
  69  * Each hashbucket also has a lock to manage concurrent access.
  70  *
  71  * The following routines manage tmem_objs.  When any tmem_obj is accessed,
  72  * the hashbucket lock must be held.
  73  */
  74
  75 /* searches for object==oid in pool, returns locked object if found */
  76 static struct tmem_obj *tmem_obj_find(struct tmem_hashbucket *hb,
  77                                         struct tmem_oid *oidp)
  78 {
  79         struct rb_node *rbnode;
  80         struct tmem_obj *obj;
  81
  82         rbnode = hb->obj_rb_root.rb_node;
  83         while (rbnode) {
  84                 BUG_ON(RB_EMPTY_NODE(rbnode));
  85                 obj = rb_entry(rbnode, struct tmem_obj, rb_tree_node);
  86                 switch (tmem_oid_compare(oidp, &obj->oid)) {
  87                 case 0: /* equal */
  88                         goto out;
  89                 case -1:
  90                         rbnode = rbnode->rb_left;
  91                         break;
  92                 case 1:
  93                         rbnode = rbnode->rb_right;
  94                         break;
  95                 }
  96         }
  97         obj = NULL;
  98 out:
  99         return obj;
 100 }
 101
 102 static void tmem_pampd_destroy_all_in_obj(struct tmem_obj *);
 103
 104 /* free an object that has no more pampds in it */
 105 static void tmem_obj_free(struct tmem_obj *obj, struct tmem_hashbucket *hb)
 106 {
 107         struct tmem_pool *pool;
 108
 109         BUG_ON(obj == NULL);
 110         ASSERT_SENTINEL(obj, OBJ);
 111         BUG_ON(obj->pampd_count > 0);
 112         pool = obj->pool;
 113         BUG_ON(pool == NULL);
 114         if (obj->objnode_tree_root != NULL) /* may be "stump" with no leaves */
 115                 tmem_pampd_destroy_all_in_obj(obj);
 116         BUG_ON(obj->objnode_tree_root != NULL);
 117         BUG_ON((long)obj->objnode_count != 0);
 118         atomic_dec(&pool->obj_count);
 119         BUG_ON(atomic_read(&pool->obj_count) < 0);
 120         INVERT_SENTINEL(obj, OBJ);
 121         obj->pool = NULL;
 122         tmem_oid_set_invalid(&obj->oid);
 123         rb_erase(&obj->rb_tree_node, &hb->obj_rb_root);
 124 }
 125
 126 /*
 127  * initialize, and insert an tmem_object_root (called only if find failed)
 128  */
 129 static void tmem_obj_init(struct tmem_obj *obj, struct tmem_hashbucket *hb,
 130                                         struct tmem_pool *pool,
 131                                         struct tmem_oid *oidp)
 132 {
 133         struct rb_root *root = &hb->obj_rb_root;
 134         struct rb_node **new = &(root->rb_node), *parent = NULL;
 135         struct tmem_obj *this;
 136
 137         BUG_ON(pool == NULL);
 138         atomic_inc(&pool->obj_count);
 139         obj->objnode_tree_height = 0;
 140         obj->objnode_tree_root = NULL;
 141         obj->pool = pool;
 142         obj->oid = *oidp;
 143         obj->objnode_count = 0;
 144         obj->pampd_count = 0;
 145         (*tmem_pamops.new_obj)(obj);
 146         SET_SENTINEL(obj, OBJ);
 147         while (*new) {
 148                 BUG_ON(RB_EMPTY_NODE(*new));
 149                 this = rb_entry(*new, struct tmem_obj, rb_tree_node);
 150                 parent = *new;
 151                 switch (tmem_oid_compare(oidp, &this->oid)) {
 152                 case 0:
 153                         BUG(); /* already present; should never happen! */
 154                         break;
 155                 case -1:
 156                         new = &(*new)->rb_left;
 157                         break;
 158                 case 1:
 159                         new = &(*new)->rb_right;
 160                         break;
 161                 }
 162         }
 163         rb_link_node(&obj->rb_tree_node, parent, new);
 164         rb_insert_color(&obj->rb_tree_node, root);
 165 }
 166
 167 /*
 168  * Tmem is managed as a set of tmem_pools with certain attributes, such as
 169  * "ephemeral" vs "persistent".  These attributes apply to all tmem_objs
 170  * and all pampds that belong to a tmem_pool.  A tmem_pool is created
 171  * or deleted relatively rarely (for example, when a filesystem is
 172  * mounted or unmounted.
 173  */
 174
 175 /* flush all data from a pool and, optionally, free it */
 176 static void tmem_pool_flush(struct tmem_pool *pool, bool destroy)
 177 {
 178         struct rb_node *rbnode;
 179         struct tmem_obj *obj;
 180         struct tmem_hashbucket *hb = &pool->hashbucket[0];
 181         int i;
 182
 183         BUG_ON(pool == NULL);
 184         for (i = 0; i < TMEM_HASH_BUCKETS; i++, hb++) {
 185                 spin_lock(&hb->lock);
 186                 rbnode = rb_first(&hb->obj_rb_root);
 187                 while (rbnode != NULL) {
 188                         obj = rb_entry(rbnode, struct tmem_obj, rb_tree_node);
 189                         rbnode = rb_next(rbnode);
 190                         tmem_pampd_destroy_all_in_obj(obj);
 191                         tmem_obj_free(obj, hb);
 192                         (*tmem_hostops.obj_free)(obj, pool);
 193                 }
 194                 spin_unlock(&hb->lock);
 195         }
 196         if (destroy)
 197                 list_del(&pool->pool_list);
 198 }
 199
 200 /*
 201  * A tmem_obj contains a radix-tree-like tree in which the intermediate
 202  * nodes are called tmem_objnodes.  (The kernel lib/radix-tree.c implementation
 203  * is very specialized and tuned for specific uses and is not particularly
 204  * suited for use from this code, though some code from the core algorithms has
 205  * been reused, thus the copyright notices below).  Each tmem_objnode contains
 206  * a set of pointers which point to either a set of intermediate tmem_objnodes
 207  * or a set of of pampds.
 208  *
 209  * Portions Copyright (C) 2001 Momchil Velikov
 210  * Portions Copyright (C) 2001 Christoph Hellwig
 211  * Portions Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
 212  */
 213
 214 struct tmem_objnode_tree_path {
 215         struct tmem_objnode *objnode;
 216         int offset;
 217 };
 218
 219 /* objnode height_to_maxindex translation */
 220 static unsigned long tmem_objnode_tree_h2max[OBJNODE_TREE_MAX_PATH + 1];
 221
 222 static void tmem_objnode_tree_init(void)
 223 {
 224         unsigned int ht, tmp;
 225
 226         for (ht = 0; ht < ARRAY_SIZE(tmem_objnode_tree_h2max); ht++) {
 227                 tmp = ht * OBJNODE_TREE_MAP_SHIFT;
 228                 if (tmp >= OBJNODE_TREE_INDEX_BITS)
 229                         tmem_objnode_tree_h2max[ht] = ~0UL;
 230                 else
 231                         tmem_objnode_tree_h2max[ht] =
 232                             (~0UL >> (OBJNODE_TREE_INDEX_BITS - tmp - 1)) >> 1;
 233         }
 234 }
 235
 236 static struct tmem_objnode *tmem_objnode_alloc(struct tmem_obj *obj)
 237 {
 238         struct tmem_objnode *objnode;
 239
 240         ASSERT_SENTINEL(obj, OBJ);
 241         BUG_ON(obj->pool == NULL);
 242         ASSERT_SENTINEL(obj->pool, POOL);
 243         objnode = (*tmem_hostops.objnode_alloc)(obj->pool);
 244         if (unlikely(objnode == NULL))
 245                 goto out;
 246         objnode->obj = obj;
 247         SET_SENTINEL(objnode, OBJNODE);
 248         memset(&objnode->slots, 0, sizeof(objnode->slots));
 249         objnode->slots_in_use = 0;
 250         obj->objnode_count++;
 251 out:
 252         return objnode;
 253 }
 254
 255 static void tmem_objnode_free(struct tmem_objnode *objnode)
 256 {
 257         struct tmem_pool *pool;
 258         int i;
 259
 260         BUG_ON(objnode == NULL);
 261         for (i = 0; i < OBJNODE_TREE_MAP_SIZE; i++)
 262                 BUG_ON(objnode->slots[i] != NULL);
 263         ASSERT_SENTINEL(objnode, OBJNODE);
 264         INVERT_SENTINEL(objnode, OBJNODE);
 265         BUG_ON(objnode->obj == NULL);
 266         ASSERT_SENTINEL(objnode->obj, OBJ);
 267         pool = objnode->obj->pool;
 268         BUG_ON(pool == NULL);
 269         ASSERT_SENTINEL(pool, POOL);
 270         objnode->obj->objnode_count--;
 271         objnode->obj = NULL;
 272         (*tmem_hostops.objnode_free)(objnode, pool);
 273 }
 274
 275 /*
 276  * lookup index in object and return associated pampd (or NULL if not found)
 277  */
 278 static void **__tmem_pampd_lookup_in_obj(struct tmem_obj *obj, uint32_t index)
 279 {
 280         unsigned int height, shift;
 281         struct tmem_objnode **slot = NULL;
 282
 283         BUG_ON(obj == NULL);
 284         ASSERT_SENTINEL(obj, OBJ);
 285         BUG_ON(obj->pool == NULL);
 286         ASSERT_SENTINEL(obj->pool, POOL);
 287
 288         height = obj->objnode_tree_height;
 289         if (index > tmem_objnode_tree_h2max[obj->objnode_tree_height])
 290                 goto out;
 291         if (height == 0 && obj->objnode_tree_root) {
 292                 slot = &obj->objnode_tree_root;
 293                 goto out;
 294         }
 295         shift = (height-1) * OBJNODE_TREE_MAP_SHIFT;
 296         slot = &obj->objnode_tree_root;
 297         while (height > 0) {
 298                 if (*slot == NULL)
 299                         goto out;
 300                 slot = (struct tmem_objnode **)
 301                         ((*slot)->slots +
 302                          ((index >> shift) & OBJNODE_TREE_MAP_MASK));
 303                 shift -= OBJNODE_TREE_MAP_SHIFT;
 304                 height--;
 305         }
 306 out:
 307         return slot != NULL ? (void **)slot : NULL;
 308 }
 309
 310 static void *tmem_pampd_lookup_in_obj(struct tmem_obj *obj, uint32_t index)
 311 {
 312         struct tmem_objnode **slot;
 313
 314         slot = (struct tmem_objnode **)__tmem_pampd_lookup_in_obj(obj, index);
 315         return slot != NULL ? *slot : NULL;
 316 }
 317
 318 static void *tmem_pampd_replace_in_obj(struct tmem_obj *obj, uint32_t index,
 319                                         void *new_pampd)
 320 {
 321         struct tmem_objnode **slot;
 322         void *ret = NULL;
 323
 324         slot = (struct tmem_objnode **)__tmem_pampd_lookup_in_obj(obj, index);
 325         if ((slot != NULL) && (*slot != NULL)) {
 326                 void *old_pampd = *(void **)slot;
 327                 *(void **)slot = new_pampd;
 328                 (*tmem_pamops.free)(old_pampd, obj->pool, NULL, 0);
 329                 ret = new_pampd;
 330         }
 331         return ret;
 332 }
 333
 334 static int tmem_pampd_add_to_obj(struct tmem_obj *obj, uint32_t index,
 335                                         void *pampd)
 336 {
 337         int ret = 0;
 338         struct tmem_objnode *objnode = NULL, *newnode, *slot;
 339         unsigned int height, shift;
 340         int offset = 0;
 341
 342         /* if necessary, extend the tree to be higher  */
 343         if (index > tmem_objnode_tree_h2max[obj->objnode_tree_height]) {
 344                 height = obj->objnode_tree_height + 1;
 345                 if (index > tmem_objnode_tree_h2max[height])
 346                         while (index > tmem_objnode_tree_h2max[height])
 347                                 height++;
 348                 if (obj->objnode_tree_root == NULL) {
 349                         obj->objnode_tree_height = height;
 350                         goto insert;
 351                 }
 352                 do {
 353                         newnode = tmem_objnode_alloc(obj);
 354                         if (!newnode) {
 355                                 ret = -ENOMEM;
 356                                 goto out;
 357                         }
 358                         newnode->slots[0] = obj->objnode_tree_root;
 359                         newnode->slots_in_use = 1;
 360                         obj->objnode_tree_root = newnode;
 361                         obj->objnode_tree_height++;
 362                 } while (height > obj->objnode_tree_height);
 363         }
 364 insert:
 365         slot = obj->objnode_tree_root;
 366         height = obj->objnode_tree_height;
 367         shift = (height-1) * OBJNODE_TREE_MAP_SHIFT;
 368         while (height > 0) {
 369                 if (slot == NULL) {
 370                         /* add a child objnode.  */
 371                         slot = tmem_objnode_alloc(obj);
 372                         if (!slot) {
 373                                 ret = -ENOMEM;
 374                                 goto out;
 375                         }
 376                         if (objnode) {
 377
 378                                 objnode->slots[offset] = slot;
 379                                 objnode->slots_in_use++;
 380                         } else
 381                                 obj->objnode_tree_root = slot;
 382                 }
 383                 /* go down a level */
 384                 offset = (index >> shift) & OBJNODE_TREE_MAP_MASK;
 385                 objnode = slot;
 386                 slot = objnode->slots[offset];
 387                 shift -= OBJNODE_TREE_MAP_SHIFT;
 388                 height--;
 389         }
 390         BUG_ON(slot != NULL);
 391         if (objnode) {
 392                 objnode->slots_in_use++;
 393                 objnode->slots[offset] = pampd;
 394         } else
 395                 obj->objnode_tree_root = pampd;
 396         obj->pampd_count++;
 397 out:
 398         return ret;
 399 }
 400
 401 static void *tmem_pampd_delete_from_obj(struct tmem_obj *obj, uint32_t index)
 402 {
 403         struct tmem_objnode_tree_path path[OBJNODE_TREE_MAX_PATH + 1];
 404         struct tmem_objnode_tree_path *pathp = path;
 405         struct tmem_objnode *slot = NULL;
 406         unsigned int height, shift;
 407         int offset;
 408
 409         BUG_ON(obj == NULL);
 410         ASSERT_SENTINEL(obj, OBJ);
 411         BUG_ON(obj->pool == NULL);
 412         ASSERT_SENTINEL(obj->pool, POOL);
 413         height = obj->objnode_tree_height;
 414         if (index > tmem_objnode_tree_h2max[height])
 415                 goto out;
 416         slot = obj->objnode_tree_root;
 417         if (height == 0 && obj->objnode_tree_root) {
 418                 obj->objnode_tree_root = NULL;
 419                 goto out;
 420         }
 421         shift = (height - 1) * OBJNODE_TREE_MAP_SHIFT;
 422         pathp->objnode = NULL;
 423         do {
 424                 if (slot == NULL)
 425                         goto out;
 426                 pathp++;
 427                 offset = (index >> shift) & OBJNODE_TREE_MAP_MASK;
 428                 pathp->offset = offset;
 429                 pathp->objnode = slot;
 430                 slot = slot->slots[offset];
 431                 shift -= OBJNODE_TREE_MAP_SHIFT;
 432                 height--;
 433         } while (height > 0);
 434         if (slot == NULL)
 435                 goto out;
 436         while (pathp->objnode) {
 437                 pathp->objnode->slots[pathp->offset] = NULL;
 438                 pathp->objnode->slots_in_use--;
 439                 if (pathp->objnode->slots_in_use) {
 440                         if (pathp->objnode == obj->objnode_tree_root) {
 441                                 while (obj->objnode_tree_height > 0 &&
 442                                   obj->objnode_tree_root->slots_in_use == 1 &&
 443                                   obj->objnode_tree_root->slots[0]) {
 444                                         struct tmem_objnode *to_free =
 445                                                 obj->objnode_tree_root;
 446
 447                                         obj->objnode_tree_root =
 448                                                         to_free->slots[0];
 449                                         obj->objnode_tree_height--;
 450                                         to_free->slots[0] = NULL;
 451                                         to_free->slots_in_use = 0;
 452                                         tmem_objnode_free(to_free);
 453                                 }
 454                         }
 455                         goto out;
 456                 }
 457                 tmem_objnode_free(pathp->objnode); /* 0 slots used, free it */
 458                 pathp--;
 459         }
 460         obj->objnode_tree_height = 0;
 461         obj->objnode_tree_root = NULL;
 462
 463 out:
 464         if (slot != NULL)
 465                 obj->pampd_count--;
 466         BUG_ON(obj->pampd_count < 0);
 467         return slot;
 468 }
 469
 470 /* recursively walk the objnode_tree destroying pampds and objnodes */
 471 static void tmem_objnode_node_destroy(struct tmem_obj *obj,
 472                                         struct tmem_objnode *objnode,
 473                                         unsigned int ht)
 474 {
 475         int i;
 476
 477         if (ht == 0)
 478                 return;
 479         for (i = 0; i < OBJNODE_TREE_MAP_SIZE; i++) {
 480                 if (objnode->slots[i]) {
 481                         if (ht == 1) {
 482                                 obj->pampd_count--;
 483                                 (*tmem_pamops.free)(objnode->slots[i],
 484                                                 obj->pool, NULL, 0);
 485                                 objnode->slots[i] = NULL;
 486                                 continue;
 487                         }
 488                         tmem_objnode_node_destroy(obj, objnode->slots[i], ht-1);
 489                         tmem_objnode_free(objnode->slots[i]);
 490                         objnode->slots[i] = NULL;
 491                 }
 492         }
 493 }
 494
 495 static void tmem_pampd_destroy_all_in_obj(struct tmem_obj *obj)
 496 {
 497         if (obj->objnode_tree_root == NULL)
 498                 return;
 499         if (obj->objnode_tree_height == 0) {
 500                 obj->pampd_count--;
 501                 (*tmem_pamops.free)(obj->objnode_tree_root, obj->pool, NULL, 0);
 502         } else {
 503                 tmem_objnode_node_destroy(obj, obj->objnode_tree_root,
 504                                         obj->objnode_tree_height);
 505                 tmem_objnode_free(obj->objnode_tree_root);
 506                 obj->objnode_tree_height = 0;
 507         }
 508         obj->objnode_tree_root = NULL;
 509         (*tmem_pamops.free_obj)(obj->pool, obj);
 510 }
 511
 512 /*
 513  * Tmem is operated on by a set of well-defined actions:
 514  * "put", "get", "flush", "flush_object", "new pool" and "destroy pool".
 515  * (The tmem ABI allows for subpages and exchanges but these operations
 516  * are not included in this implementation.)
 517  *
 518  * These "tmem core" operations are implemented in the following functions.
 519  */
 520
 521 /*
 522  * "Put" a page, e.g. copy a page from the kernel into newly allocated
 523  * PAM space (if such space is available).  Tmem_put is complicated by
 524  * a corner case: What if a page with matching handle already exists in
 525  * tmem?  To guarantee coherency, one of two actions is necessary: Either
 526  * the data for the page must be overwritten, or the page must be
 527  * "flushed" so that the data is not accessible to a subsequent "get".
 528  * Since these "duplicate puts" are relatively rare, this implementation
 529  * always flushes for simplicity.
 530  */
 531 int tmem_put(struct tmem_pool *pool, struct tmem_oid *oidp, uint32_t index,
 532                 char *data, size_t size, bool raw, bool ephemeral)
 533 {
 534         struct tmem_obj *obj = NULL, *objfound = NULL, *objnew = NULL;
 535         void *pampd = NULL, *pampd_del = NULL;
 536         int ret = -ENOMEM;
 537         struct tmem_hashbucket *hb;
 538
 539         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 540         spin_lock(&hb->lock);
 541         obj = objfound = tmem_obj_find(hb, oidp);
 542         if (obj != NULL) {
 543                 pampd = tmem_pampd_lookup_in_obj(objfound, index);
 544                 if (pampd != NULL) {
 545                         /* if found, is a dup put, flush the old one */
 546                         pampd_del = tmem_pampd_delete_from_obj(obj, index);
 547                         BUG_ON(pampd_del != pampd);
 548                         (*tmem_pamops.free)(pampd, pool, oidp, index);
 549                         if (obj->pampd_count == 0) {
 550                                 objnew = obj;
 551                                 objfound = NULL;
 552                         }
 553                         pampd = NULL;
 554                 }
 555         } else {
 556                 obj = objnew = (*tmem_hostops.obj_alloc)(pool);
 557                 if (unlikely(obj == NULL)) {
 558                         ret = -ENOMEM;
 559                         goto out;
 560                 }
 561                 tmem_obj_init(obj, hb, pool, oidp);
 562         }
 563         BUG_ON(obj == NULL);
 564         BUG_ON(((objnew != obj) && (objfound != obj)) || (objnew == objfound));
 565         pampd = (*tmem_pamops.create)(data, size, raw, ephemeral,
 566                                         obj->pool, &obj->oid, index);
 567         if (unlikely(pampd == NULL))
 568                 goto free;
 569         ret = tmem_pampd_add_to_obj(obj, index, pampd);
 570         if (unlikely(ret == -ENOMEM))
 571                 /* may have partially built objnode tree ("stump") */
 572                 goto delete_and_free;
 573         goto out;
 574
 575 delete_and_free:
 576         (void)tmem_pampd_delete_from_obj(obj, index);
 577 free:
 578         if (pampd)
 579                 (*tmem_pamops.free)(pampd, pool, NULL, 0);
 580         if (objnew) {
 581                 tmem_obj_free(objnew, hb);
 582                 (*tmem_hostops.obj_free)(objnew, pool);
 583         }
 584 out:
 585         spin_unlock(&hb->lock);
 586         return ret;
 587 }
 588
 589 /*
 590  * "Get" a page, e.g. if one can be found, copy the tmem page with the
 591  * matching handle from PAM space to the kernel.  By tmem definition,
 592  * when a "get" is successful on an ephemeral page, the page is "flushed",
 593  * and when a "get" is successful on a persistent page, the page is retained
 594  * in tmem.  Note that to preserve
 595  * coherency, "get" can never be skipped if tmem contains the data.
 596  * That is, if a get is done with a certain handle and fails, any
 597  * subsequent "get" must also fail (unless of course there is a
 598  * "put" done with the same handle).
 599
 600  */
 601 int tmem_get(struct tmem_pool *pool, struct tmem_oid *oidp, uint32_t index,
 602                 char *data, size_t *size, bool raw, int get_and_free)
 603 {
 604         struct tmem_obj *obj;
 605         void *pampd;
 606         bool ephemeral = is_ephemeral(pool);
 607         int ret = -1;
 608         struct tmem_hashbucket *hb;
 609         bool free = (get_and_free == 1) || ((get_and_free == 0) && ephemeral);
 610         bool lock_held = false;
 611
 612         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 613         spin_lock(&hb->lock);
 614         lock_held = true;
 615         obj = tmem_obj_find(hb, oidp);
 616         if (obj == NULL)
 617                 goto out;
 618         if (free)
 619                 pampd = tmem_pampd_delete_from_obj(obj, index);
 620         else
 621                 pampd = tmem_pampd_lookup_in_obj(obj, index);
 622         if (pampd == NULL)
 623                 goto out;
 624         if (free) {
 625                 if (obj->pampd_count == 0) {
 626                         tmem_obj_free(obj, hb);
 627                         (*tmem_hostops.obj_free)(obj, pool);
 628                         obj = NULL;
 629                 }
 630         }
 631         if (tmem_pamops.is_remote(pampd)) {
 632                 lock_held = false;
 633                 spin_unlock(&hb->lock);
 634         }
 635         if (free)
 636                 ret = (*tmem_pamops.get_data_and_free)(
 637                                 data, size, raw, pampd, pool, oidp, index);
 638         else
 639                 ret = (*tmem_pamops.get_data)(
 640                                 data, size, raw, pampd, pool, oidp, index);
 641         if (ret < 0)
 642                 goto out;
 643         ret = 0;
 644 out:
 645         if (lock_held)
 646                 spin_unlock(&hb->lock);
 647         return ret;
 648 }
 649
 650 /*
 651  * If a page in tmem matches the handle, "flush" this page from tmem such
 652  * that any subsequent "get" does not succeed (unless, of course, there
 653  * was another "put" with the same handle).
 654  */
 655 int tmem_flush_page(struct tmem_pool *pool,
 656                                 struct tmem_oid *oidp, uint32_t index)
 657 {
 658         struct tmem_obj *obj;
 659         void *pampd;
 660         int ret = -1;
 661         struct tmem_hashbucket *hb;
 662
 663         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 664         spin_lock(&hb->lock);
 665         obj = tmem_obj_find(hb, oidp);
 666         if (obj == NULL)
 667                 goto out;
 668         pampd = tmem_pampd_delete_from_obj(obj, index);
 669         if (pampd == NULL)
 670                 goto out;
 671         (*tmem_pamops.free)(pampd, pool, oidp, index);
 672         if (obj->pampd_count == 0) {
 673                 tmem_obj_free(obj, hb);
 674                 (*tmem_hostops.obj_free)(obj, pool);
 675         }
 676         ret = 0;
 677
 678 out:
 679         spin_unlock(&hb->lock);
 680         return ret;
 681 }
 682
 683 /*
 684  * If a page in tmem matches the handle, replace the page so that any
 685  * subsequent "get" gets the new page.  Returns 0 if
 686  * there was a page to replace, else returns -1.
 687  */
 688 int tmem_replace(struct tmem_pool *pool, struct tmem_oid *oidp,
 689                         uint32_t index, void *new_pampd)
 690 {
 691         struct tmem_obj *obj;
 692         int ret = -1;
 693         struct tmem_hashbucket *hb;
 694
 695         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 696         spin_lock(&hb->lock);
 697         obj = tmem_obj_find(hb, oidp);
 698         if (obj == NULL)
 699                 goto out;
 700         new_pampd = tmem_pampd_replace_in_obj(obj, index, new_pampd);
 701         ret = (*tmem_pamops.replace_in_obj)(new_pampd, obj);
 702 out:
 703         spin_unlock(&hb->lock);
 704         return ret;
 705 }
 706
 707 /*
 708  * "Flush" all pages in tmem matching this oid.
 709  */
 710 int tmem_flush_object(struct tmem_pool *pool, struct tmem_oid *oidp)
 711 {
 712         struct tmem_obj *obj;
 713         struct tmem_hashbucket *hb;
 714         int ret = -1;
 715
 716         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 717         spin_lock(&hb->lock);
 718         obj = tmem_obj_find(hb, oidp);
 719         if (obj == NULL)
 720                 goto out;
 721         tmem_pampd_destroy_all_in_obj(obj);
 722         tmem_obj_free(obj, hb);
 723         (*tmem_hostops.obj_free)(obj, pool);
 724         ret = 0;
 725
 726 out:
 727         spin_unlock(&hb->lock);
 728         return ret;
 729 }
 730
 731 /*
 732  * "Flush" all pages (and tmem_objs) from this tmem_pool and disable
 733  * all subsequent access to this tmem_pool.
 734  */
 735 int tmem_destroy_pool(struct tmem_pool *pool)
 736 {
 737         int ret = -1;
 738
 739         if (pool == NULL)
 740                 goto out;
 741         tmem_pool_flush(pool, 1);
 742         ret = 0;
 743 out:
 744         return ret;
 745 }
 746
 747 static LIST_HEAD(tmem_global_pool_list);
 748
 749 /*
 750  * Create a new tmem_pool with the provided flag and return
 751  * a pool id provided by the tmem host implementation.
 752  */
 753 void tmem_new_pool(struct tmem_pool *pool, uint32_t flags)
 754 {
 755         int persistent = flags & TMEM_POOL_PERSIST;
 756         int shared = flags & TMEM_POOL_SHARED;
 757         struct tmem_hashbucket *hb = &pool->hashbucket[0];
 758         int i;
 759
 760         for (i = 0; i < TMEM_HASH_BUCKETS; i++, hb++) {
 761                 hb->obj_rb_root = RB_ROOT;
 762                 spin_lock_init(&hb->lock);
 763         }
 764         INIT_LIST_HEAD(&pool->pool_list);
 765         atomic_set(&pool->obj_count, 0);
 766         SET_SENTINEL(pool, POOL);
 767         list_add_tail(&pool->pool_list, &tmem_global_pool_list);
 768         pool->persistent = persistent;
 769         pool->shared = shared;
 770 }