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 static struct tmem_obj
  76 *__tmem_obj_find(struct tmem_hashbucket*hb, struct tmem_oid *oidp,
  77                  struct rb_node **parent, struct rb_node ***link)
  78 {
  79         struct rb_node *_parent = NULL, **rbnode;
  80         struct tmem_obj *obj = NULL;
  81
  82         rbnode = &hb->obj_rb_root.rb_node;
  83         while (*rbnode) {
  84                 BUG_ON(RB_EMPTY_NODE(*rbnode));
  85                 _parent = *rbnode;
  86                 obj = rb_entry(*rbnode, struct tmem_obj,
  87                                rb_tree_node);
  88                 switch (tmem_oid_compare(oidp, &obj->oid)) {
  89                 case 0: /* equal */
  90                         goto out;
  91                 case -1:
  92                         rbnode = &(*rbnode)->rb_left;
  93                         break;
  94                 case 1:
  95                         rbnode = &(*rbnode)->rb_right;
  96                         break;
  97                 }
  98         }
  99
 100         if (parent)
 101                 *parent = _parent;
 102         if (link)
 103                 *link = rbnode;
 104
 105         obj = NULL;
 106 out:
 107         return obj;
 108 }
 109
 110
 111 /* searches for object==oid in pool, returns locked object if found */
 112 static struct tmem_obj *tmem_obj_find(struct tmem_hashbucket *hb,
 113                                         struct tmem_oid *oidp)
 114 {
 115         return __tmem_obj_find(hb, oidp, NULL, NULL);
 116 }
 117
 118 static void tmem_pampd_destroy_all_in_obj(struct tmem_obj *);
 119
 120 /* free an object that has no more pampds in it */
 121 static void tmem_obj_free(struct tmem_obj *obj, struct tmem_hashbucket *hb)
 122 {
 123         struct tmem_pool *pool;
 124
 125         BUG_ON(obj == NULL);
 126         ASSERT_SENTINEL(obj, OBJ);
 127         BUG_ON(obj->pampd_count > 0);
 128         pool = obj->pool;
 129         BUG_ON(pool == NULL);
 130         if (obj->objnode_tree_root != NULL) /* may be "stump" with no leaves */
 131                 tmem_pampd_destroy_all_in_obj(obj);
 132         BUG_ON(obj->objnode_tree_root != NULL);
 133         BUG_ON((long)obj->objnode_count != 0);
 134         atomic_dec(&pool->obj_count);
 135         BUG_ON(atomic_read(&pool->obj_count) < 0);
 136         INVERT_SENTINEL(obj, OBJ);
 137         obj->pool = NULL;
 138         tmem_oid_set_invalid(&obj->oid);
 139         rb_erase(&obj->rb_tree_node, &hb->obj_rb_root);
 140 }
 141
 142 /*
 143  * initialize, and insert an tmem_object_root (called only if find failed)
 144  */
 145 static void tmem_obj_init(struct tmem_obj *obj, struct tmem_hashbucket *hb,
 146                                         struct tmem_pool *pool,
 147                                         struct tmem_oid *oidp)
 148 {
 149         struct rb_root *root = &hb->obj_rb_root;
 150         struct rb_node **new = NULL, *parent = NULL;
 151
 152         BUG_ON(pool == NULL);
 153         atomic_inc(&pool->obj_count);
 154         obj->objnode_tree_height = 0;
 155         obj->objnode_tree_root = NULL;
 156         obj->pool = pool;
 157         obj->oid = *oidp;
 158         obj->objnode_count = 0;
 159         obj->pampd_count = 0;
 160         (*tmem_pamops.new_obj)(obj);
 161         SET_SENTINEL(obj, OBJ);
 162
 163         if (__tmem_obj_find(hb, oidp, &parent, &new))
 164                 BUG();
 165
 166         rb_link_node(&obj->rb_tree_node, parent, new);
 167         rb_insert_color(&obj->rb_tree_node, root);
 168 }
 169
 170 /*
 171  * Tmem is managed as a set of tmem_pools with certain attributes, such as
 172  * "ephemeral" vs "persistent".  These attributes apply to all tmem_objs
 173  * and all pampds that belong to a tmem_pool.  A tmem_pool is created
 174  * or deleted relatively rarely (for example, when a filesystem is
 175  * mounted or unmounted.
 176  */
 177
 178 /* flush all data from a pool and, optionally, free it */
 179 static void tmem_pool_flush(struct tmem_pool *pool, bool destroy)
 180 {
 181         struct rb_node *rbnode;
 182         struct tmem_obj *obj;
 183         struct tmem_hashbucket *hb = &pool->hashbucket[0];
 184         int i;
 185
 186         BUG_ON(pool == NULL);
 187         for (i = 0; i < TMEM_HASH_BUCKETS; i++, hb++) {
 188                 spin_lock(&hb->lock);
 189                 rbnode = rb_first(&hb->obj_rb_root);
 190                 while (rbnode != NULL) {
 191                         obj = rb_entry(rbnode, struct tmem_obj, rb_tree_node);
 192                         rbnode = rb_next(rbnode);
 193                         tmem_pampd_destroy_all_in_obj(obj);
 194                         tmem_obj_free(obj, hb);
 195                         (*tmem_hostops.obj_free)(obj, pool);
 196                 }
 197                 spin_unlock(&hb->lock);
 198         }
 199         if (destroy)
 200                 list_del(&pool->pool_list);
 201 }
 202
 203 /*
 204  * A tmem_obj contains a radix-tree-like tree in which the intermediate
 205  * nodes are called tmem_objnodes.  (The kernel lib/radix-tree.c implementation
 206  * is very specialized and tuned for specific uses and is not particularly
 207  * suited for use from this code, though some code from the core algorithms has
 208  * been reused, thus the copyright notices below).  Each tmem_objnode contains
 209  * a set of pointers which point to either a set of intermediate tmem_objnodes
 210  * or a set of of pampds.
 211  *
 212  * Portions Copyright (C) 2001 Momchil Velikov
 213  * Portions Copyright (C) 2001 Christoph Hellwig
 214  * Portions Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
 215  */
 216
 217 struct tmem_objnode_tree_path {
 218         struct tmem_objnode *objnode;
 219         int offset;
 220 };
 221
 222 /* objnode height_to_maxindex translation */
 223 static unsigned long tmem_objnode_tree_h2max[OBJNODE_TREE_MAX_PATH + 1];
 224
 225 static void tmem_objnode_tree_init(void)
 226 {
 227         unsigned int ht, tmp;
 228
 229         for (ht = 0; ht < ARRAY_SIZE(tmem_objnode_tree_h2max); ht++) {
 230                 tmp = ht * OBJNODE_TREE_MAP_SHIFT;
 231                 if (tmp >= OBJNODE_TREE_INDEX_BITS)
 232                         tmem_objnode_tree_h2max[ht] = ~0UL;
 233                 else
 234                         tmem_objnode_tree_h2max[ht] =
 235                             (~0UL >> (OBJNODE_TREE_INDEX_BITS - tmp - 1)) >> 1;
 236         }
 237 }
 238
 239 static struct tmem_objnode *tmem_objnode_alloc(struct tmem_obj *obj)
 240 {
 241         struct tmem_objnode *objnode;
 242
 243         ASSERT_SENTINEL(obj, OBJ);
 244         BUG_ON(obj->pool == NULL);
 245         ASSERT_SENTINEL(obj->pool, POOL);
 246         objnode = (*tmem_hostops.objnode_alloc)(obj->pool);
 247         if (unlikely(objnode == NULL))
 248                 goto out;
 249         objnode->obj = obj;
 250         SET_SENTINEL(objnode, OBJNODE);
 251         memset(&objnode->slots, 0, sizeof(objnode->slots));
 252         objnode->slots_in_use = 0;
 253         obj->objnode_count++;
 254 out:
 255         return objnode;
 256 }
 257
 258 static void tmem_objnode_free(struct tmem_objnode *objnode)
 259 {
 260         struct tmem_pool *pool;
 261         int i;
 262
 263         BUG_ON(objnode == NULL);
 264         for (i = 0; i < OBJNODE_TREE_MAP_SIZE; i++)
 265                 BUG_ON(objnode->slots[i] != NULL);
 266         ASSERT_SENTINEL(objnode, OBJNODE);
 267         INVERT_SENTINEL(objnode, OBJNODE);
 268         BUG_ON(objnode->obj == NULL);
 269         ASSERT_SENTINEL(objnode->obj, OBJ);
 270         pool = objnode->obj->pool;
 271         BUG_ON(pool == NULL);
 272         ASSERT_SENTINEL(pool, POOL);
 273         objnode->obj->objnode_count--;
 274         objnode->obj = NULL;
 275         (*tmem_hostops.objnode_free)(objnode, pool);
 276 }
 277
 278 /*
 279  * lookup index in object and return associated pampd (or NULL if not found)
 280  */
 281 static void **__tmem_pampd_lookup_in_obj(struct tmem_obj *obj, uint32_t index)
 282 {
 283         unsigned int height, shift;
 284         struct tmem_objnode **slot = NULL;
 285
 286         BUG_ON(obj == NULL);
 287         ASSERT_SENTINEL(obj, OBJ);
 288         BUG_ON(obj->pool == NULL);
 289         ASSERT_SENTINEL(obj->pool, POOL);
 290
 291         height = obj->objnode_tree_height;
 292         if (index > tmem_objnode_tree_h2max[obj->objnode_tree_height])
 293                 goto out;
 294         if (height == 0 && obj->objnode_tree_root) {
 295                 slot = &obj->objnode_tree_root;
 296                 goto out;
 297         }
 298         shift = (height-1) * OBJNODE_TREE_MAP_SHIFT;
 299         slot = &obj->objnode_tree_root;
 300         while (height > 0) {
 301                 if (*slot == NULL)
 302                         goto out;
 303                 slot = (struct tmem_objnode **)
 304                         ((*slot)->slots +
 305                          ((index >> shift) & OBJNODE_TREE_MAP_MASK));
 306                 shift -= OBJNODE_TREE_MAP_SHIFT;
 307                 height--;
 308         }
 309 out:
 310         return slot != NULL ? (void **)slot : NULL;
 311 }
 312
 313 static void *tmem_pampd_lookup_in_obj(struct tmem_obj *obj, uint32_t index)
 314 {
 315         struct tmem_objnode **slot;
 316
 317         slot = (struct tmem_objnode **)__tmem_pampd_lookup_in_obj(obj, index);
 318         return slot != NULL ? *slot : NULL;
 319 }
 320
 321 static void *tmem_pampd_replace_in_obj(struct tmem_obj *obj, uint32_t index,
 322                                         void *new_pampd)
 323 {
 324         struct tmem_objnode **slot;
 325         void *ret = NULL;
 326
 327         slot = (struct tmem_objnode **)__tmem_pampd_lookup_in_obj(obj, index);
 328         if ((slot != NULL) && (*slot != NULL)) {
 329                 void *old_pampd = *(void **)slot;
 330                 *(void **)slot = new_pampd;
 331                 (*tmem_pamops.free)(old_pampd, obj->pool, NULL, 0);
 332                 ret = new_pampd;
 333         }
 334         return ret;
 335 }
 336
 337 static int tmem_pampd_add_to_obj(struct tmem_obj *obj, uint32_t index,
 338                                         void *pampd)
 339 {
 340         int ret = 0;
 341         struct tmem_objnode *objnode = NULL, *newnode, *slot;
 342         unsigned int height, shift;
 343         int offset = 0;
 344
 345         /* if necessary, extend the tree to be higher  */
 346         if (index > tmem_objnode_tree_h2max[obj->objnode_tree_height]) {
 347                 height = obj->objnode_tree_height + 1;
 348                 if (index > tmem_objnode_tree_h2max[height])
 349                         while (index > tmem_objnode_tree_h2max[height])
 350                                 height++;
 351                 if (obj->objnode_tree_root == NULL) {
 352                         obj->objnode_tree_height = height;
 353                         goto insert;
 354                 }
 355                 do {
 356                         newnode = tmem_objnode_alloc(obj);
 357                         if (!newnode) {
 358                                 ret = -ENOMEM;
 359                                 goto out;
 360                         }
 361                         newnode->slots[0] = obj->objnode_tree_root;
 362                         newnode->slots_in_use = 1;
 363                         obj->objnode_tree_root = newnode;
 364                         obj->objnode_tree_height++;
 365                 } while (height > obj->objnode_tree_height);
 366         }
 367 insert:
 368         slot = obj->objnode_tree_root;
 369         height = obj->objnode_tree_height;
 370         shift = (height-1) * OBJNODE_TREE_MAP_SHIFT;
 371         while (height > 0) {
 372                 if (slot == NULL) {
 373                         /* add a child objnode.  */
 374                         slot = tmem_objnode_alloc(obj);
 375                         if (!slot) {
 376                                 ret = -ENOMEM;
 377                                 goto out;
 378                         }
 379                         if (objnode) {
 380
 381                                 objnode->slots[offset] = slot;
 382                                 objnode->slots_in_use++;
 383                         } else
 384                                 obj->objnode_tree_root = slot;
 385                 }
 386                 /* go down a level */
 387                 offset = (index >> shift) & OBJNODE_TREE_MAP_MASK;
 388                 objnode = slot;
 389                 slot = objnode->slots[offset];
 390                 shift -= OBJNODE_TREE_MAP_SHIFT;
 391                 height--;
 392         }
 393         BUG_ON(slot != NULL);
 394         if (objnode) {
 395                 objnode->slots_in_use++;
 396                 objnode->slots[offset] = pampd;
 397         } else
 398                 obj->objnode_tree_root = pampd;
 399         obj->pampd_count++;
 400 out:
 401         return ret;
 402 }
 403
 404 static void *tmem_pampd_delete_from_obj(struct tmem_obj *obj, uint32_t index)
 405 {
 406         struct tmem_objnode_tree_path path[OBJNODE_TREE_MAX_PATH + 1];
 407         struct tmem_objnode_tree_path *pathp = path;
 408         struct tmem_objnode *slot = NULL;
 409         unsigned int height, shift;
 410         int offset;
 411
 412         BUG_ON(obj == NULL);
 413         ASSERT_SENTINEL(obj, OBJ);
 414         BUG_ON(obj->pool == NULL);
 415         ASSERT_SENTINEL(obj->pool, POOL);
 416         height = obj->objnode_tree_height;
 417         if (index > tmem_objnode_tree_h2max[height])
 418                 goto out;
 419         slot = obj->objnode_tree_root;
 420         if (height == 0 && obj->objnode_tree_root) {
 421                 obj->objnode_tree_root = NULL;
 422                 goto out;
 423         }
 424         shift = (height - 1) * OBJNODE_TREE_MAP_SHIFT;
 425         pathp->objnode = NULL;
 426         do {
 427                 if (slot == NULL)
 428                         goto out;
 429                 pathp++;
 430                 offset = (index >> shift) & OBJNODE_TREE_MAP_MASK;
 431                 pathp->offset = offset;
 432                 pathp->objnode = slot;
 433                 slot = slot->slots[offset];
 434                 shift -= OBJNODE_TREE_MAP_SHIFT;
 435                 height--;
 436         } while (height > 0);
 437         if (slot == NULL)
 438                 goto out;
 439         while (pathp->objnode) {
 440                 pathp->objnode->slots[pathp->offset] = NULL;
 441                 pathp->objnode->slots_in_use--;
 442                 if (pathp->objnode->slots_in_use) {
 443                         if (pathp->objnode == obj->objnode_tree_root) {
 444                                 while (obj->objnode_tree_height > 0 &&
 445                                   obj->objnode_tree_root->slots_in_use == 1 &&
 446                                   obj->objnode_tree_root->slots[0]) {
 447                                         struct tmem_objnode *to_free =
 448                                                 obj->objnode_tree_root;
 449
 450                                         obj->objnode_tree_root =
 451                                                         to_free->slots[0];
 452                                         obj->objnode_tree_height--;
 453                                         to_free->slots[0] = NULL;
 454                                         to_free->slots_in_use = 0;
 455                                         tmem_objnode_free(to_free);
 456                                 }
 457                         }
 458                         goto out;
 459                 }
 460                 tmem_objnode_free(pathp->objnode); /* 0 slots used, free it */
 461                 pathp--;
 462         }
 463         obj->objnode_tree_height = 0;
 464         obj->objnode_tree_root = NULL;
 465
 466 out:
 467         if (slot != NULL)
 468                 obj->pampd_count--;
 469         BUG_ON(obj->pampd_count < 0);
 470         return slot;
 471 }
 472
 473 /* recursively walk the objnode_tree destroying pampds and objnodes */
 474 static void tmem_objnode_node_destroy(struct tmem_obj *obj,
 475                                         struct tmem_objnode *objnode,
 476                                         unsigned int ht)
 477 {
 478         int i;
 479
 480         if (ht == 0)
 481                 return;
 482         for (i = 0; i < OBJNODE_TREE_MAP_SIZE; i++) {
 483                 if (objnode->slots[i]) {
 484                         if (ht == 1) {
 485                                 obj->pampd_count--;
 486                                 (*tmem_pamops.free)(objnode->slots[i],
 487                                                 obj->pool, NULL, 0);
 488                                 objnode->slots[i] = NULL;
 489                                 continue;
 490                         }
 491                         tmem_objnode_node_destroy(obj, objnode->slots[i], ht-1);
 492                         tmem_objnode_free(objnode->slots[i]);
 493                         objnode->slots[i] = NULL;
 494                 }
 495         }
 496 }
 497
 498 static void tmem_pampd_destroy_all_in_obj(struct tmem_obj *obj)
 499 {
 500         if (obj->objnode_tree_root == NULL)
 501                 return;
 502         if (obj->objnode_tree_height == 0) {
 503                 obj->pampd_count--;
 504                 (*tmem_pamops.free)(obj->objnode_tree_root, obj->pool, NULL, 0);
 505         } else {
 506                 tmem_objnode_node_destroy(obj, obj->objnode_tree_root,
 507                                         obj->objnode_tree_height);
 508                 tmem_objnode_free(obj->objnode_tree_root);
 509                 obj->objnode_tree_height = 0;
 510         }
 511         obj->objnode_tree_root = NULL;
 512         (*tmem_pamops.free_obj)(obj->pool, obj);
 513 }
 514
 515 /*
 516  * Tmem is operated on by a set of well-defined actions:
 517  * "put", "get", "flush", "flush_object", "new pool" and "destroy pool".
 518  * (The tmem ABI allows for subpages and exchanges but these operations
 519  * are not included in this implementation.)
 520  *
 521  * These "tmem core" operations are implemented in the following functions.
 522  */
 523
 524 /*
 525  * "Put" a page, e.g. copy a page from the kernel into newly allocated
 526  * PAM space (if such space is available).  Tmem_put is complicated by
 527  * a corner case: What if a page with matching handle already exists in
 528  * tmem?  To guarantee coherency, one of two actions is necessary: Either
 529  * the data for the page must be overwritten, or the page must be
 530  * "flushed" so that the data is not accessible to a subsequent "get".
 531  * Since these "duplicate puts" are relatively rare, this implementation
 532  * always flushes for simplicity.
 533  */
 534 int tmem_put(struct tmem_pool *pool, struct tmem_oid *oidp, uint32_t index,
 535                 char *data, size_t size, bool raw, bool ephemeral)
 536 {
 537         struct tmem_obj *obj = NULL, *objfound = NULL, *objnew = NULL;
 538         void *pampd = NULL, *pampd_del = NULL;
 539         int ret = -ENOMEM;
 540         struct tmem_hashbucket *hb;
 541
 542         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 543         spin_lock(&hb->lock);
 544         obj = objfound = tmem_obj_find(hb, oidp);
 545         if (obj != NULL) {
 546                 pampd = tmem_pampd_lookup_in_obj(objfound, index);
 547                 if (pampd != NULL) {
 548                         /* if found, is a dup put, flush the old one */
 549                         pampd_del = tmem_pampd_delete_from_obj(obj, index);
 550                         BUG_ON(pampd_del != pampd);
 551                         (*tmem_pamops.free)(pampd, pool, oidp, index);
 552                         if (obj->pampd_count == 0) {
 553                                 objnew = obj;
 554                                 objfound = NULL;
 555                         }
 556                         pampd = NULL;
 557                 }
 558         } else {
 559                 obj = objnew = (*tmem_hostops.obj_alloc)(pool);
 560                 if (unlikely(obj == NULL)) {
 561                         ret = -ENOMEM;
 562                         goto out;
 563                 }
 564                 tmem_obj_init(obj, hb, pool, oidp);
 565         }
 566         BUG_ON(obj == NULL);
 567         BUG_ON(((objnew != obj) && (objfound != obj)) || (objnew == objfound));
 568         pampd = (*tmem_pamops.create)(data, size, raw, ephemeral,
 569                                         obj->pool, &obj->oid, index);
 570         if (unlikely(pampd == NULL))
 571                 goto free;
 572         ret = tmem_pampd_add_to_obj(obj, index, pampd);
 573         if (unlikely(ret == -ENOMEM))
 574                 /* may have partially built objnode tree ("stump") */
 575                 goto delete_and_free;
 576         goto out;
 577
 578 delete_and_free:
 579         (void)tmem_pampd_delete_from_obj(obj, index);
 580 free:
 581         if (pampd)
 582                 (*tmem_pamops.free)(pampd, pool, NULL, 0);
 583         if (objnew) {
 584                 tmem_obj_free(objnew, hb);
 585                 (*tmem_hostops.obj_free)(objnew, pool);
 586         }
 587 out:
 588         spin_unlock(&hb->lock);
 589         return ret;
 590 }
 591
 592 /*
 593  * "Get" a page, e.g. if one can be found, copy the tmem page with the
 594  * matching handle from PAM space to the kernel.  By tmem definition,
 595  * when a "get" is successful on an ephemeral page, the page is "flushed",
 596  * and when a "get" is successful on a persistent page, the page is retained
 597  * in tmem.  Note that to preserve
 598  * coherency, "get" can never be skipped if tmem contains the data.
 599  * That is, if a get is done with a certain handle and fails, any
 600  * subsequent "get" must also fail (unless of course there is a
 601  * "put" done with the same handle).
 602
 603  */
 604 int tmem_get(struct tmem_pool *pool, struct tmem_oid *oidp, uint32_t index,
 605                 char *data, size_t *size, bool raw, int get_and_free)
 606 {
 607         struct tmem_obj *obj;
 608         void *pampd;
 609         bool ephemeral = is_ephemeral(pool);
 610         int ret = -1;
 611         struct tmem_hashbucket *hb;
 612         bool free = (get_and_free == 1) || ((get_and_free == 0) && ephemeral);
 613         bool lock_held = false;
 614
 615         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 616         spin_lock(&hb->lock);
 617         lock_held = true;
 618         obj = tmem_obj_find(hb, oidp);
 619         if (obj == NULL)
 620                 goto out;
 621         if (free)
 622                 pampd = tmem_pampd_delete_from_obj(obj, index);
 623         else
 624                 pampd = tmem_pampd_lookup_in_obj(obj, index);
 625         if (pampd == NULL)
 626                 goto out;
 627         if (free) {
 628                 if (obj->pampd_count == 0) {
 629                         tmem_obj_free(obj, hb);
 630                         (*tmem_hostops.obj_free)(obj, pool);
 631                         obj = NULL;
 632                 }
 633         }
 634         if (tmem_pamops.is_remote(pampd)) {
 635                 lock_held = false;
 636                 spin_unlock(&hb->lock);
 637         }
 638         if (free)
 639                 ret = (*tmem_pamops.get_data_and_free)(
 640                                 data, size, raw, pampd, pool, oidp, index);
 641         else
 642                 ret = (*tmem_pamops.get_data)(
 643                                 data, size, raw, pampd, pool, oidp, index);
 644         if (ret < 0)
 645                 goto out;
 646         ret = 0;
 647 out:
 648         if (lock_held)
 649                 spin_unlock(&hb->lock);
 650         return ret;
 651 }
 652
 653 /*
 654  * If a page in tmem matches the handle, "flush" this page from tmem such
 655  * that any subsequent "get" does not succeed (unless, of course, there
 656  * was another "put" with the same handle).
 657  */
 658 int tmem_flush_page(struct tmem_pool *pool,
 659                                 struct tmem_oid *oidp, uint32_t index)
 660 {
 661         struct tmem_obj *obj;
 662         void *pampd;
 663         int ret = -1;
 664         struct tmem_hashbucket *hb;
 665
 666         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 667         spin_lock(&hb->lock);
 668         obj = tmem_obj_find(hb, oidp);
 669         if (obj == NULL)
 670                 goto out;
 671         pampd = tmem_pampd_delete_from_obj(obj, index);
 672         if (pampd == NULL)
 673                 goto out;
 674         (*tmem_pamops.free)(pampd, pool, oidp, index);
 675         if (obj->pampd_count == 0) {
 676                 tmem_obj_free(obj, hb);
 677                 (*tmem_hostops.obj_free)(obj, pool);
 678         }
 679         ret = 0;
 680
 681 out:
 682         spin_unlock(&hb->lock);
 683         return ret;
 684 }
 685
 686 /*
 687  * If a page in tmem matches the handle, replace the page so that any
 688  * subsequent "get" gets the new page.  Returns 0 if
 689  * there was a page to replace, else returns -1.
 690  */
 691 int tmem_replace(struct tmem_pool *pool, struct tmem_oid *oidp,
 692                         uint32_t index, void *new_pampd)
 693 {
 694         struct tmem_obj *obj;
 695         int ret = -1;
 696         struct tmem_hashbucket *hb;
 697
 698         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 699         spin_lock(&hb->lock);
 700         obj = tmem_obj_find(hb, oidp);
 701         if (obj == NULL)
 702                 goto out;
 703         new_pampd = tmem_pampd_replace_in_obj(obj, index, new_pampd);
 704         ret = (*tmem_pamops.replace_in_obj)(new_pampd, obj);
 705 out:
 706         spin_unlock(&hb->lock);
 707         return ret;
 708 }
 709
 710 /*
 711  * "Flush" all pages in tmem matching this oid.
 712  */
 713 int tmem_flush_object(struct tmem_pool *pool, struct tmem_oid *oidp)
 714 {
 715         struct tmem_obj *obj;
 716         struct tmem_hashbucket *hb;
 717         int ret = -1;
 718
 719         hb = &pool->hashbucket[tmem_oid_hash(oidp)];
 720         spin_lock(&hb->lock);
 721         obj = tmem_obj_find(hb, oidp);
 722         if (obj == NULL)
 723                 goto out;
 724         tmem_pampd_destroy_all_in_obj(obj);
 725         tmem_obj_free(obj, hb);
 726         (*tmem_hostops.obj_free)(obj, pool);
 727         ret = 0;
 728
 729 out:
 730         spin_unlock(&hb->lock);
 731         return ret;
 732 }
 733
 734 /*
 735  * "Flush" all pages (and tmem_objs) from this tmem_pool and disable
 736  * all subsequent access to this tmem_pool.
 737  */
 738 int tmem_destroy_pool(struct tmem_pool *pool)
 739 {
 740         int ret = -1;
 741
 742         if (pool == NULL)
 743                 goto out;
 744         tmem_pool_flush(pool, 1);
 745         ret = 0;
 746 out:
 747         return ret;
 748 }
 749
 750 static LIST_HEAD(tmem_global_pool_list);
 751
 752 /*
 753  * Create a new tmem_pool with the provided flag and return
 754  * a pool id provided by the tmem host implementation.
 755  */
 756 void tmem_new_pool(struct tmem_pool *pool, uint32_t flags)
 757 {
 758         int persistent = flags & TMEM_POOL_PERSIST;
 759         int shared = flags & TMEM_POOL_SHARED;
 760         struct tmem_hashbucket *hb = &pool->hashbucket[0];
 761         int i;
 762
 763         for (i = 0; i < TMEM_HASH_BUCKETS; i++, hb++) {
 764                 hb->obj_rb_root = RB_ROOT;
 765                 spin_lock_init(&hb->lock);
 766         }
 767         INIT_LIST_HEAD(&pool->pool_list);
 768         atomic_set(&pool->obj_count, 0);
 769         SET_SENTINEL(pool, POOL);
 770         list_add_tail(&pool->pool_list, &tmem_global_pool_list);
 771         pool->persistent = persistent;
 772         pool->shared = shared;
 773 }