lustre/lov/lov_pool.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * GPL HEADER START
   5  *
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 only,
  10  * as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License version 2 for more details (a copy is included
  16  * in the LICENSE file that accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * version 2 along with this program; If not, see [sun.com URL with a
  20  * copy of GPLv2].
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  23  * CA 95054 USA or visit www.sun.com if you need additional information or
  24  * have any questions.
  25  *
  26  * GPL HEADER END
  27  */
  28 /*
  29  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  30  * Use is subject to license terms.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  *
  36  * lustre/lov/lov_pool.c
  37  *
  38  * OST pool methods
  39  *
  40  * Author: Jacques-Charles LAFOUCRIERE <jc.lafoucriere@cea.fr>
  41  * Author: Alex Lyashkov <Alexey.Lyashkov@Sun.COM>
  42  * Author: Nathaniel Rutman <Nathan.Rutman@Sun.COM>
  43  */
  44
  45 #define DEBUG_SUBSYSTEM S_LOV
  46
  47 #ifdef __KERNEL__
  48 #include <libcfs/libcfs.h>
  49 #else
  50 #include <liblustre.h>
  51 #endif
  52
  53 #include <obd.h>
  54 #include "lov_internal.h"
  55
  56 static void lov_pool_getref(struct pool_desc *pool)
  57 {
  58         CDEBUG(D_INFO, "pool %p\n", pool);
  59         cfs_atomic_inc(&pool->pool_refcount);
  60 }
  61
  62 void lov_pool_putref(struct pool_desc *pool)
  63 {
  64         CDEBUG(D_INFO, "pool %p\n", pool);
  65         if (cfs_atomic_dec_and_test(&pool->pool_refcount)) {
  66                 LASSERT(cfs_hlist_unhashed(&pool->pool_hash));
  67                 LASSERT(cfs_list_empty(&pool->pool_list));
  68                 LASSERT(pool->pool_proc_entry == NULL);
  69                 lov_ost_pool_free(&(pool->pool_rr.lqr_pool));
  70                 lov_ost_pool_free(&(pool->pool_obds));
  71                 OBD_FREE_PTR(pool);
  72                 EXIT;
  73         }
  74 }
  75
  76
  77 /*
  78  * hash function using a Rotating Hash algorithm
  79  * Knuth, D. The Art of Computer Programming,
  80  * Volume 3: Sorting and Searching,
  81  * Chapter 6.4.
  82  * Addison Wesley, 1973
  83  */
  84 static __u32 pool_hashfn(cfs_hash_t *hash_body, void *key, unsigned mask)
  85 {
  86         int i;
  87         __u32 result;
  88         char *poolname;
  89
  90         result = 0;
  91         poolname = (char *)key;
  92         for (i = 0; i < LOV_MAXPOOLNAME; i++) {
  93                 if (poolname[i] == '\0')
  94                         break;
  95                 result = (result << 4)^(result >> 28) ^  poolname[i];
  96         }
  97         return (result % mask);
  98 }
  99
 100 static void *pool_key(cfs_hlist_node_t *hnode)
 101 {
 102         struct pool_desc *pool;
 103
 104         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 105         return (pool->pool_name);
 106 }
 107
 108 static int pool_hashkey_compare(void *key, cfs_hlist_node_t *compared_hnode)
 109 {
 110         char *pool_name;
 111         struct pool_desc *pool;
 112         int rc;
 113
 114         pool_name = (char *)key;
 115         pool = cfs_hlist_entry(compared_hnode, struct pool_desc, pool_hash);
 116         rc = strncmp(pool_name, pool->pool_name, LOV_MAXPOOLNAME);
 117         return (!rc);
 118 }
 119
 120 static void *pool_hashrefcount_get(cfs_hlist_node_t *hnode)
 121 {
 122         struct pool_desc *pool;
 123
 124         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 125         lov_pool_getref(pool);
 126         return (pool);
 127 }
 128
 129 static void *pool_hashrefcount_put(cfs_hlist_node_t *hnode)
 130 {
 131         struct pool_desc *pool;
 132
 133         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 134         lov_pool_putref(pool);
 135         return (pool);
 136 }
 137
 138 cfs_hash_ops_t pool_hash_operations = {
 139         .hs_hash        = pool_hashfn,
 140         .hs_key         = pool_key,
 141         .hs_compare     = pool_hashkey_compare,
 142         .hs_get         = pool_hashrefcount_get,
 143         .hs_put         = pool_hashrefcount_put,
 144 };
 145
 146 #ifdef LPROCFS
 147 /* ifdef needed for liblustre support */
 148 /*
 149  * pool /proc seq_file methods
 150  */
 151 /*
 152  * iterator is used to go through the target pool entries
 153  * index is the current entry index in the lp_array[] array
 154  * index >= pos returned to the seq_file interface
 155  * pos is from 0 to (pool->pool_obds.op_count - 1)
 156  */
 157 #define POOL_IT_MAGIC 0xB001CEA0
 158 struct pool_iterator {
 159         int magic;
 160         struct pool_desc *pool;
 161         int idx;        /* from 0 to pool_tgt_size - 1 */
 162 };
 163
 164 static void *pool_proc_next(struct seq_file *s, void *v, loff_t *pos)
 165 {
 166         struct pool_iterator *iter = (struct pool_iterator *)s->private;
 167         int prev_idx;
 168
 169         LASSERTF(iter->magic == POOL_IT_MAGIC, "%08X", iter->magic);
 170
 171         /* test if end of file */
 172         if (*pos >= pool_tgt_count(iter->pool))
 173                 return NULL;
 174
 175         /* iterate to find a non empty entry */
 176         prev_idx = iter->idx;
 177         cfs_down_read(&pool_tgt_rw_sem(iter->pool));
 178         iter->idx++;
 179         if (iter->idx == pool_tgt_count(iter->pool)) {
 180                 iter->idx = prev_idx; /* we stay on the last entry */
 181                 cfs_up_read(&pool_tgt_rw_sem(iter->pool));
 182                 return NULL;
 183         }
 184         cfs_up_read(&pool_tgt_rw_sem(iter->pool));
 185         (*pos)++;
 186         /* return != NULL to continue */
 187         return iter;
 188 }
 189
 190 static void *pool_proc_start(struct seq_file *s, loff_t *pos)
 191 {
 192         struct pool_desc *pool = (struct pool_desc *)s->private;
 193         struct pool_iterator *iter;
 194
 195         lov_pool_getref(pool);
 196         if ((pool_tgt_count(pool) == 0) ||
 197             (*pos >= pool_tgt_count(pool))) {
 198                 /* iter is not created, so stop() has no way to
 199                  * find pool to dec ref */
 200                 lov_pool_putref(pool);
 201                 return NULL;
 202         }
 203
 204         OBD_ALLOC_PTR(iter);
 205         if (!iter)
 206                 return ERR_PTR(-ENOMEM);
 207         iter->magic = POOL_IT_MAGIC;
 208         iter->pool = pool;
 209         iter->idx = 0;
 210
 211         /* we use seq_file private field to memorized iterator so
 212          * we can free it at stop() */
 213         /* /!\ do not forget to restore it to pool before freeing it */
 214         s->private = iter;
 215         if (*pos > 0) {
 216                 loff_t i;
 217                 void *ptr;
 218
 219                 i = 0;
 220                 do {
 221                      ptr = pool_proc_next(s, &iter, &i);
 222                 } while ((i < *pos) && (ptr != NULL));
 223                 return ptr;
 224         }
 225         return iter;
 226 }
 227
 228 static void pool_proc_stop(struct seq_file *s, void *v)
 229 {
 230         struct pool_iterator *iter = (struct pool_iterator *)s->private;
 231
 232         /* in some cases stop() method is called 2 times, without
 233          * calling start() method (see seq_read() from fs/seq_file.c)
 234          * we have to free only if s->private is an iterator */
 235         if ((iter) && (iter->magic == POOL_IT_MAGIC)) {
 236                 /* we restore s->private so next call to pool_proc_start()
 237                  * will work */
 238                 s->private = iter->pool;
 239                 lov_pool_putref(iter->pool);
 240                 OBD_FREE_PTR(iter);
 241         }
 242         return;
 243 }
 244
 245 static int pool_proc_show(struct seq_file *s, void *v)
 246 {
 247         struct pool_iterator *iter = (struct pool_iterator *)v;
 248         struct lov_tgt_desc *tgt;
 249
 250         LASSERTF(iter->magic == POOL_IT_MAGIC, "%08X", iter->magic);
 251         LASSERT(iter->pool != NULL);
 252         LASSERT(iter->idx <= pool_tgt_count(iter->pool));
 253
 254         cfs_down_read(&pool_tgt_rw_sem(iter->pool));
 255         tgt = pool_tgt(iter->pool, iter->idx);
 256         cfs_up_read(&pool_tgt_rw_sem(iter->pool));
 257         if (tgt)
 258                 seq_printf(s, "%s\n", obd_uuid2str(&(tgt->ltd_uuid)));
 259
 260         return 0;
 261 }
 262
 263 static struct seq_operations pool_proc_ops = {
 264         .start          = pool_proc_start,
 265         .next           = pool_proc_next,
 266         .stop           = pool_proc_stop,
 267         .show           = pool_proc_show,
 268 };
 269
 270 static int pool_proc_open(struct inode *inode, struct file *file)
 271 {
 272         int rc;
 273
 274         rc = seq_open(file, &pool_proc_ops);
 275         if (!rc) {
 276                 struct seq_file *s = file->private_data;
 277                 s->private = PROC_I(inode)->pde->data;
 278         }
 279         return rc;
 280 }
 281
 282 static struct file_operations pool_proc_operations = {
 283         .open           = pool_proc_open,
 284         .read           = seq_read,
 285         .llseek         = seq_lseek,
 286         .release        = seq_release,
 287 };
 288 #endif /* LPROCFS */
 289
 290 void lov_dump_pool(int level, struct pool_desc *pool)
 291 {
 292         int i;
 293
 294         lov_pool_getref(pool);
 295
 296         CDEBUG(level, "pool "LOV_POOLNAMEF" has %d members\n",
 297                pool->pool_name, pool->pool_obds.op_count);
 298         cfs_down_read(&pool_tgt_rw_sem(pool));
 299
 300         for (i = 0; i < pool_tgt_count(pool) ; i++) {
 301                 if (!pool_tgt(pool, i) || !(pool_tgt(pool, i))->ltd_exp)
 302                         continue;
 303                 CDEBUG(level, "pool "LOV_POOLNAMEF"[%d] = %s\n",
 304                        pool->pool_name, i,
 305                        obd_uuid2str(&((pool_tgt(pool, i))->ltd_uuid)));
 306         }
 307
 308         cfs_up_read(&pool_tgt_rw_sem(pool));
 309         lov_pool_putref(pool);
 310 }
 311
 312 #define LOV_POOL_INIT_COUNT 2
 313 int lov_ost_pool_init(struct ost_pool *op, unsigned int count)
 314 {
 315         ENTRY;
 316
 317         if (count == 0)
 318                 count = LOV_POOL_INIT_COUNT;
 319         op->op_array = NULL;
 320         op->op_count = 0;
 321         cfs_init_rwsem(&op->op_rw_sem);
 322         op->op_size = count;
 323         OBD_ALLOC(op->op_array, op->op_size * sizeof(op->op_array[0]));
 324         if (op->op_array == NULL) {
 325                 op->op_size = 0;
 326                 RETURN(-ENOMEM);
 327         }
 328         EXIT;
 329         return 0;
 330 }
 331
 332 /* Caller must hold write op_rwlock */
 333 int lov_ost_pool_extend(struct ost_pool *op, unsigned int min_count)
 334 {
 335         __u32 *new;
 336         int new_size;
 337
 338         LASSERT(min_count != 0);
 339
 340         if (op->op_count < op->op_size)
 341                 return 0;
 342
 343         new_size = max(min_count, 2 * op->op_size);
 344         OBD_ALLOC(new, new_size * sizeof(op->op_array[0]));
 345         if (new == NULL)
 346                 return -ENOMEM;
 347
 348         /* copy old array to new one */
 349         memcpy(new, op->op_array, op->op_size * sizeof(op->op_array[0]));
 350         OBD_FREE(op->op_array, op->op_size * sizeof(op->op_array[0]));
 351         op->op_array = new;
 352         op->op_size = new_size;
 353         return 0;
 354 }
 355
 356 int lov_ost_pool_add(struct ost_pool *op, __u32 idx, unsigned int min_count)
 357 {
 358         int rc = 0, i;
 359         ENTRY;
 360
 361         cfs_down_write(&op->op_rw_sem);
 362
 363         rc = lov_ost_pool_extend(op, min_count);
 364         if (rc)
 365                 GOTO(out, rc);
 366
 367         /* search ost in pool array */
 368         for (i = 0; i < op->op_count; i++) {
 369                 if (op->op_array[i] == idx)
 370                         GOTO(out, rc = -EEXIST);
 371         }
 372         /* ost not found we add it */
 373         op->op_array[op->op_count] = idx;
 374         op->op_count++;
 375         EXIT;
 376 out:
 377         cfs_up_write(&op->op_rw_sem);
 378         return rc;
 379 }
 380
 381 int lov_ost_pool_remove(struct ost_pool *op, __u32 idx)
 382 {
 383         int i;
 384         ENTRY;
 385
 386         cfs_down_write(&op->op_rw_sem);
 387
 388         for (i = 0; i < op->op_count; i++) {
 389                 if (op->op_array[i] == idx) {
 390                         memmove(&op->op_array[i], &op->op_array[i + 1],
 391                                 (op->op_count - i - 1) * sizeof(op->op_array[0]));
 392                         op->op_count--;
 393                         cfs_up_write(&op->op_rw_sem);
 394                         EXIT;
 395                         return 0;
 396                 }
 397         }
 398
 399         cfs_up_write(&op->op_rw_sem);
 400         RETURN(-EINVAL);
 401 }
 402
 403 int lov_ost_pool_free(struct ost_pool *op)
 404 {
 405         ENTRY;
 406
 407         if (op->op_size == 0)
 408                 RETURN(0);
 409
 410         cfs_down_write(&op->op_rw_sem);
 411
 412         OBD_FREE(op->op_array, op->op_size * sizeof(op->op_array[0]));
 413         op->op_array = NULL;
 414         op->op_count = 0;
 415         op->op_size = 0;
 416
 417         cfs_up_write(&op->op_rw_sem);
 418         RETURN(0);
 419 }
 420
 421
 422 int lov_pool_new(struct obd_device *obd, char *poolname)
 423 {
 424         struct lov_obd *lov;
 425         struct pool_desc *new_pool;
 426         int rc;
 427         ENTRY;
 428
 429         lov = &(obd->u.lov);
 430
 431         if (strlen(poolname) > LOV_MAXPOOLNAME)
 432                 RETURN(-ENAMETOOLONG);
 433
 434         OBD_ALLOC_PTR(new_pool);
 435         if (new_pool == NULL)
 436                 RETURN(-ENOMEM);
 437
 438         strncpy(new_pool->pool_name, poolname, LOV_MAXPOOLNAME);
 439         new_pool->pool_name[LOV_MAXPOOLNAME] = '\0';
 440         new_pool->pool_lov = lov;
 441         /* ref count init to 1 because when created a pool is always used
 442          * up to deletion
 443          */
 444         cfs_atomic_set(&new_pool->pool_refcount, 1);
 445         rc = lov_ost_pool_init(&new_pool->pool_obds, 0);
 446         if (rc)
 447                GOTO(out_err, rc);
 448
 449         memset(&(new_pool->pool_rr), 0, sizeof(struct lov_qos_rr));
 450         rc = lov_ost_pool_init(&new_pool->pool_rr.lqr_pool, 0);
 451         if (rc)
 452                 GOTO(out_free_pool_obds, rc);
 453
 454         CFS_INIT_HLIST_NODE(&new_pool->pool_hash);
 455
 456 #ifdef LPROCFS
 457         /* we need this assert seq_file is not implementated for liblustre */
 458         /* get ref for /proc file */
 459         lov_pool_getref(new_pool);
 460         new_pool->pool_proc_entry = lprocfs_add_simple(lov->lov_pool_proc_entry,
 461                                                        poolname, NULL, NULL,
 462                                                        new_pool,
 463                                                        &pool_proc_operations);
 464         if (IS_ERR(new_pool->pool_proc_entry)) {
 465                 CWARN("Cannot add proc pool entry "LOV_POOLNAMEF"\n", poolname);
 466                 new_pool->pool_proc_entry = NULL;
 467                 lov_pool_putref(new_pool);
 468         }
 469         CDEBUG(D_INFO, "pool %p - proc %p\n", new_pool, new_pool->pool_proc_entry);
 470 #endif
 471
 472         cfs_spin_lock(&obd->obd_dev_lock);
 473         cfs_list_add_tail(&new_pool->pool_list, &lov->lov_pool_list);
 474         lov->lov_pool_count++;
 475         cfs_spin_unlock(&obd->obd_dev_lock);
 476
 477         /* add to find only when it fully ready  */
 478         rc = cfs_hash_add_unique(lov->lov_pools_hash_body, poolname,
 479                                  &new_pool->pool_hash);
 480         if (rc)
 481                 GOTO(out_err, rc = -EEXIST);
 482
 483         CDEBUG(D_CONFIG, LOV_POOLNAMEF" is pool #%d\n",
 484                poolname, lov->lov_pool_count);
 485
 486         RETURN(0);
 487
 488 out_err:
 489         cfs_spin_lock(&obd->obd_dev_lock);
 490         cfs_list_del_init(&new_pool->pool_list);
 491         lov->lov_pool_count--;
 492         cfs_spin_unlock(&obd->obd_dev_lock);
 493
 494         lprocfs_remove(&new_pool->pool_proc_entry);
 495
 496         lov_ost_pool_free(&new_pool->pool_rr.lqr_pool);
 497 out_free_pool_obds:
 498         lov_ost_pool_free(&new_pool->pool_obds);
 499         OBD_FREE_PTR(new_pool);
 500         return rc;
 501 }
 502
 503 int lov_pool_del(struct obd_device *obd, char *poolname)
 504 {
 505         struct lov_obd *lov;
 506         struct pool_desc *pool;
 507         ENTRY;
 508
 509         lov = &(obd->u.lov);
 510
 511         /* lookup and kill hash reference */
 512         pool = cfs_hash_del_key(lov->lov_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                 lov_pool_putref(pool);
 520         }
 521
 522         cfs_spin_lock(&obd->obd_dev_lock);
 523         cfs_list_del_init(&pool->pool_list);
 524         lov->lov_pool_count--;
 525         cfs_spin_unlock(&obd->obd_dev_lock);
 526
 527         /* release last reference */
 528         lov_pool_putref(pool);
 529
 530         RETURN(0);
 531 }
 532
 533
 534 int lov_pool_add(struct obd_device *obd, char *poolname, char *ostname)
 535 {
 536         struct obd_uuid ost_uuid;
 537         struct lov_obd *lov;
 538         struct pool_desc *pool;
 539         unsigned int lov_idx;
 540         int rc;
 541         ENTRY;
 542
 543         lov = &(obd->u.lov);
 544
 545         pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
 546         if (pool == NULL)
 547                 RETURN(-ENOENT);
 548
 549         obd_str2uuid(&ost_uuid, ostname);
 550
 551
 552         /* search ost in lov array */
 553         obd_getref(obd);
 554         for (lov_idx = 0; lov_idx < lov->desc.ld_tgt_count; lov_idx++) {
 555                 if (!lov->lov_tgts[lov_idx])
 556                         continue;
 557                 if (obd_uuid_equals(&ost_uuid,
 558                                     &(lov->lov_tgts[lov_idx]->ltd_uuid)))
 559                         break;
 560         }
 561         /* test if ost found in lov */
 562         if (lov_idx == lov->desc.ld_tgt_count)
 563                 GOTO(out, rc = -EINVAL);
 564
 565         rc = lov_ost_pool_add(&pool->pool_obds, lov_idx, lov->lov_tgt_size);
 566         if (rc)
 567                 GOTO(out, rc);
 568
 569         pool->pool_rr.lqr_dirty = 1;
 570
 571         CDEBUG(D_CONFIG, "Added %s to "LOV_POOLNAMEF" as member %d\n",
 572                ostname, poolname,  pool_tgt_count(pool));
 573
 574         EXIT;
 575 out:
 576         obd_putref(obd);
 577         lov_pool_putref(pool);
 578         return rc;
 579 }
 580
 581 int lov_pool_remove(struct obd_device *obd, char *poolname, char *ostname)
 582 {
 583         struct obd_uuid ost_uuid;
 584         struct lov_obd *lov;
 585         struct pool_desc *pool;
 586         unsigned int lov_idx;
 587         int rc = 0;
 588         ENTRY;
 589
 590         lov = &(obd->u.lov);
 591
 592         pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
 593         if (pool == NULL)
 594                 RETURN(-ENOENT);
 595
 596         obd_str2uuid(&ost_uuid, ostname);
 597
 598         obd_getref(obd);
 599         /* search ost in lov array, to get index */
 600         for (lov_idx = 0; lov_idx < lov->desc.ld_tgt_count; lov_idx++) {
 601                 if (!lov->lov_tgts[lov_idx])
 602                         continue;
 603
 604                 if (obd_uuid_equals(&ost_uuid,
 605                                     &(lov->lov_tgts[lov_idx]->ltd_uuid)))
 606                         break;
 607         }
 608
 609         /* test if ost found in lov */
 610         if (lov_idx == lov->desc.ld_tgt_count)
 611                 GOTO(out, rc = -EINVAL);
 612
 613         lov_ost_pool_remove(&pool->pool_obds, lov_idx);
 614
 615         pool->pool_rr.lqr_dirty = 1;
 616
 617         CDEBUG(D_CONFIG, "%s removed from "LOV_POOLNAMEF"\n", ostname,
 618                poolname);
 619
 620         EXIT;
 621 out:
 622         obd_putref(obd);
 623         lov_pool_putref(pool);
 624         return rc;
 625 }
 626
 627 int lov_check_index_in_pool(__u32 idx, struct pool_desc *pool)
 628 {
 629         int i, rc;
 630         ENTRY;
 631
 632         /* caller may no have a ref on pool if it got the pool
 633          * without calling lov_find_pool() (e.g. go through the lov pool
 634          * list)
 635          */
 636         lov_pool_getref(pool);
 637
 638         cfs_down_read(&pool_tgt_rw_sem(pool));
 639
 640         for (i = 0; i < pool_tgt_count(pool); i++) {
 641                 if (pool_tgt_array(pool)[i] == idx)
 642                         GOTO(out, rc = 0);
 643         }
 644         rc = -ENOENT;
 645         EXIT;
 646 out:
 647         cfs_up_read(&pool_tgt_rw_sem(pool));
 648
 649         lov_pool_putref(pool);
 650         return rc;
 651 }
 652
 653 struct pool_desc *lov_find_pool(struct lov_obd *lov, char *poolname)
 654 {
 655         struct pool_desc *pool;
 656
 657         pool = NULL;
 658         if (poolname[0] != '\0') {
 659                 pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
 660                 if (pool == NULL)
 661                         CWARN("Request for an unknown pool ("LOV_POOLNAMEF")\n",
 662                               poolname);
 663                 if ((pool != NULL) && (pool_tgt_count(pool) == 0)) {
 664                         CWARN("Request for an empty pool ("LOV_POOLNAMEF")\n",
 665                                poolname);
 666                         /* pool is ignored, so we remove ref on it */
 667                         lov_pool_putref(pool);
 668                         pool = NULL;
 669                 }
 670         }
 671         return pool;
 672 }
 673