lustre/lod/lod_pool.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see [sun.com URL with a
  18  * copy of GPLv2].
  19  *
  20  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  21  * CA 95054 USA or visit www.sun.com if you need additional information or
  22  * have any questions.
  23  *
  24  * GPL HEADER END
  25  */
  26 /*
  27  * Copyright  2008 Sun Microsystems, Inc. All rights reserved
  28  * Use is subject to license terms.
  29  */
  30 /*
  31  * This file is part of Lustre, http://www.lustre.org/
  32  * Lustre is a trademark of Sun Microsystems, Inc.
  33  *
  34  * lustre/lod/lod_pool.c
  35  *
  36  * OST pool methods
  37  *
  38  * Author: Jacques-Charles LAFOUCRIERE <jc.lafoucriere@cea.fr>
  39  * Author: Alex Lyashkov <Alexey.Lyashkov@Sun.COM>
  40  * Author: Nathaniel Rutman <Nathan.Rutman@Sun.COM>
  41  */
  42
  43 #define DEBUG_SUBSYSTEM S_LOV
  44
  45 #include <libcfs/libcfs.h>
  46 #include <obd.h>
  47 #include "lod_internal.h"
  48
  49 #define pool_tgt(_p, _i) \
  50         OST_TGT(lu2lod_dev((_p)->pool_lobd->obd_lu_dev),(_p)->pool_obds.op_array[_i])
  51
  52 static void lod_pool_getref(struct pool_desc *pool)
  53 {
  54         CDEBUG(D_INFO, "pool %p\n", pool);
  55         atomic_inc(&pool->pool_refcount);
  56 }
  57
  58 void lod_pool_putref(struct pool_desc *pool)
  59 {
  60         CDEBUG(D_INFO, "pool %p\n", pool);
  61         if (atomic_dec_and_test(&pool->pool_refcount)) {
  62                 LASSERT(cfs_hlist_unhashed(&pool->pool_hash));
  63                 LASSERT(cfs_list_empty(&pool->pool_list));
  64                 LASSERT(pool->pool_proc_entry == NULL);
  65                 lod_ost_pool_free(&(pool->pool_rr.lqr_pool));
  66                 lod_ost_pool_free(&(pool->pool_obds));
  67                 OBD_FREE_PTR(pool);
  68                 EXIT;
  69         }
  70 }
  71
  72 void lod_pool_putref_locked(struct pool_desc *pool)
  73 {
  74         CDEBUG(D_INFO, "pool %p\n", pool);
  75         LASSERT(cfs_atomic_read(&pool->pool_refcount) > 1);
  76
  77         cfs_atomic_dec(&pool->pool_refcount);
  78 }
  79
  80
  81 /*
  82  * hash function using a Rotating Hash algorithm
  83  * Knuth, D. The Art of Computer Programming,
  84  * Volume 3: Sorting and Searching,
  85  * Chapter 6.4.
  86  * Addison Wesley, 1973
  87  */
  88 static __u32 pool_hashfn(cfs_hash_t *hash_body, const void *key, unsigned mask)
  89 {
  90         int i;
  91         __u32 result;
  92         char *poolname;
  93
  94         result = 0;
  95         poolname = (char *)key;
  96         for (i = 0; i < LOV_MAXPOOLNAME; i++) {
  97                 if (poolname[i] == '\0')
  98                         break;
  99                 result = (result << 4)^(result >> 28) ^  poolname[i];
 100         }
 101         return (result % mask);
 102 }
 103
 104 static void *pool_key(cfs_hlist_node_t *hnode)
 105 {
 106         struct pool_desc *pool;
 107
 108         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 109         return (pool->pool_name);
 110 }
 111
 112 static int pool_hashkey_keycmp(const void *key, cfs_hlist_node_t *compared_hnode)
 113 {
 114         char *pool_name;
 115         struct pool_desc *pool;
 116
 117         pool_name = (char *)key;
 118         pool = cfs_hlist_entry(compared_hnode, struct pool_desc, pool_hash);
 119         return !strncmp(pool_name, pool->pool_name, LOV_MAXPOOLNAME);
 120 }
 121
 122 static void *pool_hashobject(cfs_hlist_node_t *hnode)
 123 {
 124         return cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 125 }
 126
 127 static void pool_hashrefcount_get(cfs_hash_t *hs, cfs_hlist_node_t *hnode)
 128 {
 129         struct pool_desc *pool;
 130
 131         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 132         lod_pool_getref(pool);
 133 }
 134
 135 static void pool_hashrefcount_put_locked(cfs_hash_t *hs,
 136                 cfs_hlist_node_t *hnode)
 137 {
 138         struct pool_desc *pool;
 139
 140         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 141         lod_pool_putref_locked(pool);
 142 }
 143
 144 cfs_hash_ops_t pool_hash_operations = {
 145         .hs_hash        = pool_hashfn,
 146         .hs_key         = pool_key,
 147         .hs_keycmp      = pool_hashkey_keycmp,
 148         .hs_object      = pool_hashobject,
 149         .hs_get         = pool_hashrefcount_get,
 150         .hs_put_locked  = pool_hashrefcount_put_locked,
 151 };
 152
 153 #ifdef LPROCFS
 154 /* ifdef needed for liblustre support */
 155 /*
 156  * pool /proc seq_file methods
 157  */
 158 /*
 159  * iterator is used to go through the target pool entries
 160  * index is the current entry index in the lp_array[] array
 161  * index >= pos returned to the seq_file interface
 162  * pos is from 0 to (pool->pool_obds.op_count - 1)
 163  */
 164 #define POOL_IT_MAGIC 0xB001CEA0
 165 struct pool_iterator {
 166         int magic;
 167         struct pool_desc *pool;
 168         int idx;        /* from 0 to pool_tgt_size - 1 */
 169 };
 170
 171 static void *pool_proc_next(struct seq_file *s, void *v, loff_t *pos)
 172 {
 173         struct pool_iterator *iter = (struct pool_iterator *)s->private;
 174         int prev_idx;
 175
 176         LASSERTF(iter->magic == POOL_IT_MAGIC, "%08X", iter->magic);
 177
 178         /* test if end of file */
 179         if (*pos >= pool_tgt_count(iter->pool))
 180                 return NULL;
 181
 182         /* iterate to find a non empty entry */
 183         prev_idx = iter->idx;
 184         down_read(&pool_tgt_rw_sem(iter->pool));
 185         iter->idx++;
 186         if (iter->idx == pool_tgt_count(iter->pool)) {
 187                 iter->idx = prev_idx; /* we stay on the last entry */
 188                 up_read(&pool_tgt_rw_sem(iter->pool));
 189                 return NULL;
 190         }
 191         up_read(&pool_tgt_rw_sem(iter->pool));
 192         (*pos)++;
 193         /* return != NULL to continue */
 194         return iter;
 195 }
 196
 197 static void *pool_proc_start(struct seq_file *s, loff_t *pos)
 198 {
 199         struct pool_desc *pool = (struct pool_desc *)s->private;
 200         struct pool_iterator *iter;
 201
 202         lod_pool_getref(pool);
 203         if ((pool_tgt_count(pool) == 0) ||
 204             (*pos >= pool_tgt_count(pool))) {
 205                 /* iter is not created, so stop() has no way to
 206                  * find pool to dec ref */
 207                 lod_pool_putref(pool);
 208                 return NULL;
 209         }
 210
 211         OBD_ALLOC_PTR(iter);
 212         if (!iter)
 213                 return ERR_PTR(-ENOMEM);
 214         iter->magic = POOL_IT_MAGIC;
 215         iter->pool = pool;
 216         iter->idx = 0;
 217
 218         /* we use seq_file private field to memorized iterator so
 219          * we can free it at stop() */
 220         /* /!\ do not forget to restore it to pool before freeing it */
 221         s->private = iter;
 222         if (*pos > 0) {
 223                 loff_t i;
 224                 void *ptr;
 225
 226                 i = 0;
 227                 do {
 228                         ptr = pool_proc_next(s, &iter, &i);
 229                 } while ((i < *pos) && (ptr != NULL));
 230                 return ptr;
 231         }
 232         return iter;
 233 }
 234
 235 static void pool_proc_stop(struct seq_file *s, void *v)
 236 {
 237         struct pool_iterator *iter = (struct pool_iterator *)s->private;
 238
 239         /* in some cases stop() method is called 2 times, without
 240          * calling start() method (see seq_read() from fs/seq_file.c)
 241          * we have to free only if s->private is an iterator */
 242         if ((iter) && (iter->magic == POOL_IT_MAGIC)) {
 243                 /* we restore s->private so next call to pool_proc_start()
 244                  * will work */
 245                 s->private = iter->pool;
 246                 lod_pool_putref(iter->pool);
 247                 OBD_FREE_PTR(iter);
 248         }
 249         return;
 250 }
 251
 252 static int pool_proc_show(struct seq_file *s, void *v)
 253 {
 254         struct pool_iterator *iter = (struct pool_iterator *)v;
 255         struct lod_ost_desc  *osc_desc;
 256
 257         LASSERTF(iter->magic == POOL_IT_MAGIC, "%08X", iter->magic);
 258         LASSERT(iter->pool != NULL);
 259         LASSERT(iter->idx <= pool_tgt_count(iter->pool));
 260
 261         down_read(&pool_tgt_rw_sem(iter->pool));
 262         osc_desc = pool_tgt(iter->pool, iter->idx);
 263         up_read(&pool_tgt_rw_sem(iter->pool));
 264         if (osc_desc)
 265                 seq_printf(s, "%s\n", obd_uuid2str(&(osc_desc->ltd_uuid)));
 266
 267         return 0;
 268 }
 269
 270 static struct seq_operations pool_proc_ops = {
 271         .start  = pool_proc_start,
 272         .next   = pool_proc_next,
 273         .stop   = pool_proc_stop,
 274         .show   = pool_proc_show,
 275 };
 276
 277 static int pool_proc_open(struct inode *inode, struct file *file)
 278 {
 279         int rc;
 280
 281         rc = seq_open(file, &pool_proc_ops);
 282         if (!rc) {
 283                 struct seq_file *s = file->private_data;
 284                 s->private = PROC_I(inode)->pde->data;
 285         }
 286         return rc;
 287 }
 288
 289 static struct file_operations pool_proc_operations = {
 290         .open           = pool_proc_open,
 291         .read           = seq_read,
 292         .llseek         = seq_lseek,
 293         .release        = seq_release,
 294 };
 295 #endif /* LPROCFS */
 296
 297 void lod_dump_pool(int level, struct pool_desc *pool)
 298 {
 299         int i;
 300
 301         lod_pool_getref(pool);
 302
 303         CDEBUG(level, "pool "LOV_POOLNAMEF" has %d members\n",
 304                pool->pool_name, pool->pool_obds.op_count);
 305         down_read(&pool_tgt_rw_sem(pool));
 306
 307         for (i = 0; i < pool_tgt_count(pool) ; i++) {
 308                 if (!pool_tgt(pool, i) || !(pool_tgt(pool, i))->ltd_exp)
 309                         continue;
 310                 CDEBUG(level, "pool "LOV_POOLNAMEF"[%d] = %s\n",
 311                        pool->pool_name, i,
 312                        obd_uuid2str(&((pool_tgt(pool, i))->ltd_uuid)));
 313         }
 314
 315         up_read(&pool_tgt_rw_sem(pool));
 316         lod_pool_putref(pool);
 317 }
 318
 319 #define LOD_POOL_INIT_COUNT 2
 320 int lod_ost_pool_init(struct ost_pool *op, unsigned int count)
 321 {
 322         ENTRY;
 323
 324         if (count == 0)
 325                 count = LOD_POOL_INIT_COUNT;
 326         op->op_array = NULL;
 327         op->op_count = 0;
 328         init_rwsem(&op->op_rw_sem);
 329         op->op_size = count;
 330         OBD_ALLOC(op->op_array, op->op_size * sizeof(op->op_array[0]));
 331         if (op->op_array == NULL) {
 332                 op->op_size = 0;
 333                 RETURN(-ENOMEM);
 334         }
 335         EXIT;
 336         return 0;
 337 }
 338
 339 /* Caller must hold write op_rwlock */
 340 int lod_ost_pool_extend(struct ost_pool *op, unsigned int min_count)
 341 {
 342         __u32 *new;
 343         int new_size;
 344
 345         LASSERT(min_count != 0);
 346
 347         if (op->op_count < op->op_size)
 348                 return 0;
 349
 350         new_size = max(min_count, 2 * op->op_size);
 351         OBD_ALLOC(new, new_size * sizeof(op->op_array[0]));
 352         if (new == NULL)
 353                 return -ENOMEM;
 354
 355         /* copy old array to new one */
 356         memcpy(new, op->op_array, op->op_size * sizeof(op->op_array[0]));
 357         OBD_FREE(op->op_array, op->op_size * sizeof(op->op_array[0]));
 358         op->op_array = new;
 359         op->op_size = new_size;
 360         return 0;
 361 }
 362
 363 int lod_ost_pool_add(struct ost_pool *op, __u32 idx, unsigned int min_count)
 364 {
 365         int rc = 0, i;
 366         ENTRY;
 367
 368         down_write(&op->op_rw_sem);
 369
 370         rc = lod_ost_pool_extend(op, min_count);
 371         if (rc)
 372                 GOTO(out, rc);
 373
 374         /* search ost in pool array */
 375         for (i = 0; i < op->op_count; i++) {
 376                 if (op->op_array[i] == idx)
 377                         GOTO(out, rc = -EEXIST);
 378         }
 379         /* ost not found we add it */
 380         op->op_array[op->op_count] = idx;
 381         op->op_count++;
 382         EXIT;
 383 out:
 384         up_write(&op->op_rw_sem);
 385         return rc;
 386 }
 387
 388 int lod_ost_pool_remove(struct ost_pool *op, __u32 idx)
 389 {
 390         int i;
 391         ENTRY;
 392
 393         down_write(&op->op_rw_sem);
 394
 395         for (i = 0; i < op->op_count; i++) {
 396                 if (op->op_array[i] == idx) {
 397                         memmove(&op->op_array[i], &op->op_array[i + 1],
 398                                 (op->op_count - i - 1) * sizeof(op->op_array[0]));
 399                         op->op_count--;
 400                         up_write(&op->op_rw_sem);
 401                         EXIT;
 402                         return 0;
 403                 }
 404         }
 405
 406         up_write(&op->op_rw_sem);
 407         RETURN(-EINVAL);
 408 }
 409
 410 int lod_ost_pool_free(struct ost_pool *op)
 411 {
 412         ENTRY;
 413
 414         if (op->op_size == 0)
 415                 RETURN(0);
 416
 417         down_write(&op->op_rw_sem);
 418
 419         OBD_FREE(op->op_array, op->op_size * sizeof(op->op_array[0]));
 420         op->op_array = NULL;
 421         op->op_count = 0;
 422         op->op_size = 0;
 423
 424         up_write(&op->op_rw_sem);
 425         RETURN(0);
 426 }
 427
 428 int lod_pool_new(struct obd_device *obd, char *poolname)
 429 {
 430         struct lod_device *lod = lu2lod_dev(obd->obd_lu_dev);
 431         struct pool_desc  *new_pool;
 432         int rc;
 433         ENTRY;
 434
 435         if (strlen(poolname) > LOV_MAXPOOLNAME)
 436                 RETURN(-ENAMETOOLONG);
 437
 438         OBD_ALLOC_PTR(new_pool);
 439         if (new_pool == NULL)
 440                 RETURN(-ENOMEM);
 441
 442         strncpy(new_pool->pool_name, poolname, LOV_MAXPOOLNAME);
 443         new_pool->pool_name[LOV_MAXPOOLNAME] = '\0';
 444         new_pool->pool_lobd = obd;
 445         /* ref count init to 1 because when created a pool is always used
 446          * up to deletion
 447          */
 448         atomic_set(&new_pool->pool_refcount, 1);
 449         rc = lod_ost_pool_init(&new_pool->pool_obds, 0);
 450         if (rc)
 451                 GOTO(out_err, rc);
 452
 453         memset(&(new_pool->pool_rr), 0, sizeof(struct lov_qos_rr));
 454         rc = lod_ost_pool_init(&new_pool->pool_rr.lqr_pool, 0);
 455         if (rc)
 456                 GOTO(out_free_pool_obds, rc);
 457
 458         INIT_HLIST_NODE(&new_pool->pool_hash);
 459
 460 #ifdef LPROCFS
 461         lod_pool_getref(new_pool);
 462         new_pool->pool_proc_entry = lprocfs_add_simple(lod->lod_pool_proc_entry,
 463                                                        poolname, NULL, NULL,
 464                                                        new_pool,
 465                                                        &pool_proc_operations);
 466         if (IS_ERR(new_pool->pool_proc_entry)) {
 467                 CWARN("Cannot add proc pool entry "LOV_POOLNAMEF"\n", poolname);
 468                 new_pool->pool_proc_entry = NULL;
 469                 lod_pool_putref(new_pool);
 470         }
 471         CDEBUG(D_INFO, "pool %p - proc %p\n", new_pool, new_pool->pool_proc_entry);
 472 #endif
 473
 474         spin_lock(&obd->obd_dev_lock);
 475         cfs_list_add_tail(&new_pool->pool_list, &lod->lod_pool_list);
 476         lod->lod_pool_count++;
 477         spin_unlock(&obd->obd_dev_lock);
 478
 479         /* add to find only when it fully ready  */
 480         rc = cfs_hash_add_unique(lod->lod_pools_hash_body, poolname,
 481                                  &new_pool->pool_hash);
 482         if (rc)
 483                 GOTO(out_err, rc = -EEXIST);
 484
 485         CDEBUG(D_CONFIG, LOV_POOLNAMEF" is pool #%d\n",
 486                         poolname, lod->lod_pool_count);
 487
 488         RETURN(0);
 489
 490 out_err:
 491         spin_lock(&obd->obd_dev_lock);
 492         cfs_list_del_init(&new_pool->pool_list);
 493         lod->lod_pool_count--;
 494         spin_unlock(&obd->obd_dev_lock);
 495
 496         lprocfs_remove(&new_pool->pool_proc_entry);
 497
 498         lod_ost_pool_free(&new_pool->pool_rr.lqr_pool);
 499 out_free_pool_obds:
 500         lod_ost_pool_free(&new_pool->pool_obds);
 501         OBD_FREE_PTR(new_pool);
 502         return rc;
 503 }
 504
 505 int lod_pool_del(struct obd_device *obd, char *poolname)
 506 {
 507         struct lod_device *lod = lu2lod_dev(obd->obd_lu_dev);
 508         struct pool_desc  *pool;
 509         ENTRY;
 510
 511         /* lookup and kill hash reference */
 512         pool = cfs_hash_del_key(lod->lod_pools_hash_body, poolname);
 513         if (pool == NULL)
 514                 RETURN(-ENOENT);
 515
 516         if (pool->pool_proc_entry != NULL) {
 517                 CDEBUG(D_INFO, "proc entry %p\n", pool->pool_proc_entry);
 518                 lprocfs_remove(&pool->pool_proc_entry);
 519                 lod_pool_putref(pool);
 520         }
 521
 522         spin_lock(&obd->obd_dev_lock);
 523         cfs_list_del_init(&pool->pool_list);
 524         lod->lod_pool_count--;
 525         spin_unlock(&obd->obd_dev_lock);
 526
 527         /* release last reference */
 528         lod_pool_putref(pool);
 529
 530         RETURN(0);
 531 }
 532
 533
 534 int lod_pool_add(struct obd_device *obd, char *poolname, char *ostname)
 535 {
 536         struct lod_device *lod = lu2lod_dev(obd->obd_lu_dev);
 537         struct obd_uuid    ost_uuid;
 538         struct pool_desc  *pool;
 539         unsigned int       idx;
 540         int                rc = -EINVAL;
 541         ENTRY;
 542
 543         pool = cfs_hash_lookup(lod->lod_pools_hash_body, poolname);
 544         if (pool == NULL)
 545                 RETURN(-ENOENT);
 546
 547         obd_str2uuid(&ost_uuid, ostname);
 548
 549         /* search ost in lod array */
 550         lod_getref(lod);
 551         lod_foreach_ost(lod, idx) {
 552                 if (obd_uuid_equals(&ost_uuid, &OST_TGT(lod, idx)->ltd_uuid)) {
 553                         rc = 0;
 554                         break;
 555                 }
 556         }
 557
 558         if (rc)
 559                 GOTO(out, rc);
 560
 561         rc = lod_ost_pool_add(&pool->pool_obds, idx, lod->lod_osts_size);
 562         if (rc)
 563                 GOTO(out, rc);
 564
 565         pool->pool_rr.lqr_dirty = 1;
 566
 567         CDEBUG(D_CONFIG, "Added %s to "LOV_POOLNAMEF" as member %d\n",
 568                         ostname, poolname,  pool_tgt_count(pool));
 569
 570         EXIT;
 571 out:
 572         lod_putref(lod);
 573         lod_pool_putref(pool);
 574         return rc;
 575 }
 576
 577 int lod_pool_remove(struct obd_device *obd, char *poolname, char *ostname)
 578 {
 579         struct lod_device *lod = lu2lod_dev(obd->obd_lu_dev);
 580         struct obd_uuid    ost_uuid;
 581         struct pool_desc  *pool;
 582         unsigned int       idx;
 583         int                rc = -EINVAL;
 584         ENTRY;
 585
 586         pool = cfs_hash_lookup(lod->lod_pools_hash_body, poolname);
 587         if (pool == NULL)
 588                 RETURN(-ENOENT);
 589
 590         obd_str2uuid(&ost_uuid, ostname);
 591
 592         lod_getref(lod);
 593         /* search ost in lod array, to get index */
 594         cfs_foreach_bit(lod->lod_ost_bitmap, idx) {
 595                 if (obd_uuid_equals(&ost_uuid, &OST_TGT(lod, idx)->ltd_uuid)) {
 596                         rc = 0;
 597                         break;
 598                 }
 599         }
 600
 601         /* test if ost found in lod array */
 602         if (rc)
 603                 GOTO(out, rc);
 604
 605         lod_ost_pool_remove(&pool->pool_obds, idx);
 606
 607         pool->pool_rr.lqr_dirty = 1;
 608
 609         CDEBUG(D_CONFIG, "%s removed from "LOV_POOLNAMEF"\n", ostname,
 610                poolname);
 611
 612         EXIT;
 613 out:
 614         lod_putref(lod);
 615         lod_pool_putref(pool);
 616         return rc;
 617 }
 618
 619 int lod_check_index_in_pool(__u32 idx, struct pool_desc *pool)
 620 {
 621         int i, rc;
 622         ENTRY;
 623
 624         /* caller may no have a ref on pool if it got the pool
 625          * without calling lod_find_pool() (e.g. go through the lod pool
 626          * list)
 627          */
 628         lod_pool_getref(pool);
 629
 630         down_read(&pool_tgt_rw_sem(pool));
 631
 632         for (i = 0; i < pool_tgt_count(pool); i++) {
 633                 if (pool_tgt_array(pool)[i] == idx)
 634                         GOTO(out, rc = 0);
 635         }
 636         rc = -ENOENT;
 637         EXIT;
 638 out:
 639         up_read(&pool_tgt_rw_sem(pool));
 640
 641         lod_pool_putref(pool);
 642         return rc;
 643 }
 644
 645 struct pool_desc *lod_find_pool(struct lod_device *lod, char *poolname)
 646 {
 647         struct pool_desc *pool;
 648
 649         pool = NULL;
 650         if (poolname[0] != '\0') {
 651                 pool = cfs_hash_lookup(lod->lod_pools_hash_body, poolname);
 652                 if (pool == NULL)
 653                         CWARN("Request for an unknown pool ("LOV_POOLNAMEF")\n",
 654                               poolname);
 655                 if ((pool != NULL) && (pool_tgt_count(pool) == 0)) {
 656                         CWARN("Request for an empty pool ("LOV_POOLNAMEF")\n",
 657                               poolname);
 658                         /* pool is ignored, so we remove ref on it */
 659                         lod_pool_putref(pool);
 660                         pool = NULL;
 661                 }
 662         }
 663         return pool;
 664 }
 665