lustre/lov/lov_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 (c) 2008, 2010, Oracle and/or its affiliates. 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/lov/lov_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 #ifdef __KERNEL__
  46 #include <libcfs/libcfs.h>
  47 #else
  48 #include <liblustre.h>
  49 #endif
  50
  51 #include <obd.h>
  52 #include "lov_internal.h"
  53
  54 static void lov_pool_getref(struct pool_desc *pool)
  55 {
  56         CDEBUG(D_INFO, "pool %p\n", pool);
  57         cfs_atomic_inc(&pool->pool_refcount);
  58 }
  59
  60 void lov_pool_putref(struct pool_desc *pool)
  61 {
  62         CDEBUG(D_INFO, "pool %p\n", pool);
  63         if (cfs_atomic_dec_and_test(&pool->pool_refcount)) {
  64                 LASSERT(cfs_hlist_unhashed(&pool->pool_hash));
  65                 LASSERT(cfs_list_empty(&pool->pool_list));
  66                 LASSERT(pool->pool_proc_entry == NULL);
  67                 lov_ost_pool_free(&(pool->pool_rr.lqr_pool));
  68                 lov_ost_pool_free(&(pool->pool_obds));
  69                 OBD_FREE_PTR(pool);
  70                 EXIT;
  71         }
  72 }
  73
  74 void lov_pool_putref_locked(struct pool_desc *pool)
  75 {
  76         CDEBUG(D_INFO, "pool %p\n", pool);
  77         LASSERT(cfs_atomic_read(&pool->pool_refcount) > 1);
  78
  79         cfs_atomic_dec(&pool->pool_refcount);
  80 }
  81
  82 /*
  83  * hash function using a Rotating Hash algorithm
  84  * Knuth, D. The Art of Computer Programming,
  85  * Volume 3: Sorting and Searching,
  86  * Chapter 6.4.
  87  * Addison Wesley, 1973
  88  */
  89 static __u32 pool_hashfn(cfs_hash_t *hash_body, const void *key, unsigned mask)
  90 {
  91         int i;
  92         __u32 result;
  93         char *poolname;
  94
  95         result = 0;
  96         poolname = (char *)key;
  97         for (i = 0; i < LOV_MAXPOOLNAME; i++) {
  98                 if (poolname[i] == '\0')
  99                         break;
 100                 result = (result << 4)^(result >> 28) ^  poolname[i];
 101         }
 102         return (result % mask);
 103 }
 104
 105 static void *pool_key(cfs_hlist_node_t *hnode)
 106 {
 107         struct pool_desc *pool;
 108
 109         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 110         return (pool->pool_name);
 111 }
 112
 113 static int pool_hashkey_keycmp(const void *key, cfs_hlist_node_t *compared_hnode)
 114 {
 115         char *pool_name;
 116         struct pool_desc *pool;
 117
 118         pool_name = (char *)key;
 119         pool = cfs_hlist_entry(compared_hnode, struct pool_desc, pool_hash);
 120         return !strncmp(pool_name, pool->pool_name, LOV_MAXPOOLNAME);
 121 }
 122
 123 static void *pool_hashobject(cfs_hlist_node_t *hnode)
 124 {
 125         return cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 126 }
 127
 128 static void pool_hashrefcount_get(cfs_hash_t *hs, cfs_hlist_node_t *hnode)
 129 {
 130         struct pool_desc *pool;
 131
 132         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 133         lov_pool_getref(pool);
 134 }
 135
 136 static void pool_hashrefcount_put_locked(cfs_hash_t *hs,
 137                                          cfs_hlist_node_t *hnode)
 138 {
 139         struct pool_desc *pool;
 140
 141         pool = cfs_hlist_entry(hnode, struct pool_desc, pool_hash);
 142         lov_pool_putref_locked(pool);
 143 }
 144
 145 cfs_hash_ops_t pool_hash_operations = {
 146         .hs_hash        = pool_hashfn,
 147         .hs_key         = pool_key,
 148         .hs_keycmp      = pool_hashkey_keycmp,
 149         .hs_object      = pool_hashobject,
 150         .hs_get         = pool_hashrefcount_get,
 151         .hs_put_locked  = pool_hashrefcount_put_locked,
 152
 153 };
 154
 155 #ifdef LPROCFS
 156 /* ifdef needed for liblustre support */
 157 /*
 158  * pool /proc seq_file methods
 159  */
 160 /*
 161  * iterator is used to go through the target pool entries
 162  * index is the current entry index in the lp_array[] array
 163  * index >= pos returned to the seq_file interface
 164  * pos is from 0 to (pool->pool_obds.op_count - 1)
 165  */
 166 #define POOL_IT_MAGIC 0xB001CEA0
 167 struct pool_iterator {
 168         int magic;
 169         struct pool_desc *pool;
 170         int idx;        /* from 0 to pool_tgt_size - 1 */
 171 };
 172
 173 static void *pool_proc_next(struct seq_file *s, void *v, loff_t *pos)
 174 {
 175         struct pool_iterator *iter = (struct pool_iterator *)s->private;
 176         int prev_idx;
 177
 178         LASSERTF(iter->magic == POOL_IT_MAGIC, "%08X", iter->magic);
 179
 180         /* test if end of file */
 181         if (*pos >= pool_tgt_count(iter->pool))
 182                 return NULL;
 183
 184         /* iterate to find a non empty entry */
 185         prev_idx = iter->idx;
 186         cfs_down_read(&pool_tgt_rw_sem(iter->pool));
 187         iter->idx++;
 188         if (iter->idx == pool_tgt_count(iter->pool)) {
 189                 iter->idx = prev_idx; /* we stay on the last entry */
 190                 cfs_up_read(&pool_tgt_rw_sem(iter->pool));
 191                 return NULL;
 192         }
 193         cfs_up_read(&pool_tgt_rw_sem(iter->pool));
 194         (*pos)++;
 195         /* return != NULL to continue */
 196         return iter;
 197 }
 198
 199 static void *pool_proc_start(struct seq_file *s, loff_t *pos)
 200 {
 201         struct pool_desc *pool = (struct pool_desc *)s->private;
 202         struct pool_iterator *iter;
 203
 204         lov_pool_getref(pool);
 205         if ((pool_tgt_count(pool) == 0) ||
 206             (*pos >= pool_tgt_count(pool))) {
 207                 /* iter is not created, so stop() has no way to
 208                  * find pool to dec ref */
 209                 lov_pool_putref(pool);
 210                 return NULL;
 211         }
 212
 213         OBD_ALLOC_PTR(iter);
 214         if (!iter)
 215                 return ERR_PTR(-ENOMEM);
 216         iter->magic = POOL_IT_MAGIC;
 217         iter->pool = pool;
 218         iter->idx = 0;
 219
 220         /* we use seq_file private field to memorized iterator so
 221          * we can free it at stop() */
 222         /* /!\ do not forget to restore it to pool before freeing it */
 223         s->private = iter;
 224         if (*pos > 0) {
 225                 loff_t i;
 226                 void *ptr;
 227
 228                 i = 0;
 229                 do {
 230                      ptr = pool_proc_next(s, &iter, &i);
 231                 } while ((i < *pos) && (ptr != NULL));
 232                 return ptr;
 233         }
 234         return iter;
 235 }
 236
 237 static void pool_proc_stop(struct seq_file *s, void *v)
 238 {
 239         struct pool_iterator *iter = (struct pool_iterator *)s->private;
 240
 241         /* in some cases stop() method is called 2 times, without
 242          * calling start() method (see seq_read() from fs/seq_file.c)
 243          * we have to free only if s->private is an iterator */
 244         if ((iter) && (iter->magic == POOL_IT_MAGIC)) {
 245                 /* we restore s->private so next call to pool_proc_start()
 246                  * will work */
 247                 s->private = iter->pool;
 248                 lov_pool_putref(iter->pool);
 249                 OBD_FREE_PTR(iter);
 250         }
 251         return;
 252 }
 253
 254 static int pool_proc_show(struct seq_file *s, void *v)
 255 {
 256         struct pool_iterator *iter = (struct pool_iterator *)v;
 257         struct lov_tgt_desc *tgt;
 258
 259         LASSERTF(iter->magic == POOL_IT_MAGIC, "%08X", iter->magic);
 260         LASSERT(iter->pool != NULL);
 261         LASSERT(iter->idx <= pool_tgt_count(iter->pool));
 262
 263         cfs_down_read(&pool_tgt_rw_sem(iter->pool));
 264         tgt = pool_tgt(iter->pool, iter->idx);
 265         cfs_up_read(&pool_tgt_rw_sem(iter->pool));
 266         if (tgt)
 267                 seq_printf(s, "%s\n", obd_uuid2str(&(tgt->ltd_uuid)));
 268
 269         return 0;
 270 }
 271
 272 static struct seq_operations pool_proc_ops = {
 273         .start          = pool_proc_start,
 274         .next           = pool_proc_next,
 275         .stop           = pool_proc_stop,
 276         .show           = pool_proc_show,
 277 };
 278
 279 static int pool_proc_open(struct inode *inode, struct file *file)
 280 {
 281         int rc;
 282
 283         rc = seq_open(file, &pool_proc_ops);
 284         if (!rc) {
 285                 struct seq_file *s = file->private_data;
 286                 s->private = PROC_I(inode)->pde->data;
 287         }
 288         return rc;
 289 }
 290
 291 static struct file_operations pool_proc_operations = {
 292         .open           = pool_proc_open,
 293         .read           = seq_read,
 294         .llseek         = seq_lseek,
 295         .release        = seq_release,
 296 };
 297 #endif /* LPROCFS */
 298
 299 void lov_dump_pool(int level, struct pool_desc *pool)
 300 {
 301         int i;
 302
 303         lov_pool_getref(pool);
 304
 305         CDEBUG(level, "pool "LOV_POOLNAMEF" has %d members\n",
 306                pool->pool_name, pool->pool_obds.op_count);
 307         cfs_down_read(&pool_tgt_rw_sem(pool));
 308
 309         for (i = 0; i < pool_tgt_count(pool) ; i++) {
 310                 if (!pool_tgt(pool, i) || !(pool_tgt(pool, i))->ltd_exp)
 311                         continue;
 312                 CDEBUG(level, "pool "LOV_POOLNAMEF"[%d] = %s\n",
 313                        pool->pool_name, i,
 314                        obd_uuid2str(&((pool_tgt(pool, i))->ltd_uuid)));
 315         }
 316
 317         cfs_up_read(&pool_tgt_rw_sem(pool));
 318         lov_pool_putref(pool);
 319 }
 320
 321 #define LOV_POOL_INIT_COUNT 2
 322 int lov_ost_pool_init(struct ost_pool *op, unsigned int count)
 323 {
 324         ENTRY;
 325
 326         if (count == 0)
 327                 count = LOV_POOL_INIT_COUNT;
 328         op->op_array = NULL;
 329         op->op_count = 0;
 330         cfs_init_rwsem(&op->op_rw_sem);
 331         op->op_size = count;
 332         OBD_ALLOC(op->op_array, op->op_size * sizeof(op->op_array[0]));
 333         if (op->op_array == NULL) {
 334                 op->op_size = 0;
 335                 RETURN(-ENOMEM);
 336         }
 337         EXIT;
 338         return 0;
 339 }
 340
 341 /* Caller must hold write op_rwlock */
 342 int lov_ost_pool_extend(struct ost_pool *op, unsigned int min_count)
 343 {
 344         __u32 *new;
 345         int new_size;
 346
 347         LASSERT(min_count != 0);
 348
 349         if (op->op_count < op->op_size)
 350                 return 0;
 351
 352         new_size = max(min_count, 2 * op->op_size);
 353         OBD_ALLOC(new, new_size * sizeof(op->op_array[0]));
 354         if (new == NULL)
 355                 return -ENOMEM;
 356
 357         /* copy old array to new one */
 358         memcpy(new, op->op_array, op->op_size * sizeof(op->op_array[0]));
 359         OBD_FREE(op->op_array, op->op_size * sizeof(op->op_array[0]));
 360         op->op_array = new;
 361         op->op_size = new_size;
 362         return 0;
 363 }
 364
 365 int lov_ost_pool_add(struct ost_pool *op, __u32 idx, unsigned int min_count)
 366 {
 367         int rc = 0, i;
 368         ENTRY;
 369
 370         cfs_down_write(&op->op_rw_sem);
 371
 372         rc = lov_ost_pool_extend(op, min_count);
 373         if (rc)
 374                 GOTO(out, rc);
 375
 376         /* search ost in pool array */
 377         for (i = 0; i < op->op_count; i++) {
 378                 if (op->op_array[i] == idx)
 379                         GOTO(out, rc = -EEXIST);
 380         }
 381         /* ost not found we add it */
 382         op->op_array[op->op_count] = idx;
 383         op->op_count++;
 384         EXIT;
 385 out:
 386         cfs_up_write(&op->op_rw_sem);
 387         return rc;
 388 }
 389
 390 int lov_ost_pool_remove(struct ost_pool *op, __u32 idx)
 391 {
 392         int i;
 393         ENTRY;
 394
 395         cfs_down_write(&op->op_rw_sem);
 396
 397         for (i = 0; i < op->op_count; i++) {
 398                 if (op->op_array[i] == idx) {
 399                         memmove(&op->op_array[i], &op->op_array[i + 1],
 400                                 (op->op_count - i - 1) * sizeof(op->op_array[0]));
 401                         op->op_count--;
 402                         cfs_up_write(&op->op_rw_sem);
 403                         EXIT;
 404                         return 0;
 405                 }
 406         }
 407
 408         cfs_up_write(&op->op_rw_sem);
 409         RETURN(-EINVAL);
 410 }
 411
 412 int lov_ost_pool_free(struct ost_pool *op)
 413 {
 414         ENTRY;
 415
 416         if (op->op_size == 0)
 417                 RETURN(0);
 418
 419         cfs_down_write(&op->op_rw_sem);
 420
 421         OBD_FREE(op->op_array, op->op_size * sizeof(op->op_array[0]));
 422         op->op_array = NULL;
 423         op->op_count = 0;
 424         op->op_size = 0;
 425
 426         cfs_up_write(&op->op_rw_sem);
 427         RETURN(0);
 428 }
 429
 430
 431 int lov_pool_new(struct obd_device *obd, char *poolname)
 432 {
 433         struct lov_obd *lov;
 434         struct pool_desc *new_pool;
 435         int rc;
 436         ENTRY;
 437
 438         lov = &(obd->u.lov);
 439
 440         if (strlen(poolname) > LOV_MAXPOOLNAME)
 441                 RETURN(-ENAMETOOLONG);
 442
 443         OBD_ALLOC_PTR(new_pool);
 444         if (new_pool == NULL)
 445                 RETURN(-ENOMEM);
 446
 447         strncpy(new_pool->pool_name, poolname, LOV_MAXPOOLNAME);
 448         new_pool->pool_name[LOV_MAXPOOLNAME] = '\0';
 449         new_pool->pool_lov = lov;
 450         /* ref count init to 1 because when created a pool is always used
 451          * up to deletion
 452          */
 453         cfs_atomic_set(&new_pool->pool_refcount, 1);
 454         rc = lov_ost_pool_init(&new_pool->pool_obds, 0);
 455         if (rc)
 456                GOTO(out_err, rc);
 457
 458         memset(&(new_pool->pool_rr), 0, sizeof(struct lov_qos_rr));
 459         rc = lov_ost_pool_init(&new_pool->pool_rr.lqr_pool, 0);
 460         if (rc)
 461                 GOTO(out_free_pool_obds, rc);
 462
 463         CFS_INIT_HLIST_NODE(&new_pool->pool_hash);
 464
 465 #ifdef LPROCFS
 466         /* we need this assert seq_file is not implementated for liblustre */
 467         /* get ref for /proc file */
 468         lov_pool_getref(new_pool);
 469         new_pool->pool_proc_entry = lprocfs_add_simple(lov->lov_pool_proc_entry,
 470                                                        poolname, NULL, NULL,
 471                                                        new_pool,
 472                                                        &pool_proc_operations);
 473         if (IS_ERR(new_pool->pool_proc_entry)) {
 474                 CWARN("Cannot add proc pool entry "LOV_POOLNAMEF"\n", poolname);
 475                 new_pool->pool_proc_entry = NULL;
 476                 lov_pool_putref(new_pool);
 477         }
 478         CDEBUG(D_INFO, "pool %p - proc %p\n", new_pool, new_pool->pool_proc_entry);
 479 #endif
 480
 481         cfs_spin_lock(&obd->obd_dev_lock);
 482         cfs_list_add_tail(&new_pool->pool_list, &lov->lov_pool_list);
 483         lov->lov_pool_count++;
 484         cfs_spin_unlock(&obd->obd_dev_lock);
 485
 486         /* add to find only when it fully ready  */
 487         rc = cfs_hash_add_unique(lov->lov_pools_hash_body, poolname,
 488                                  &new_pool->pool_hash);
 489         if (rc)
 490                 GOTO(out_err, rc = -EEXIST);
 491
 492         CDEBUG(D_CONFIG, LOV_POOLNAMEF" is pool #%d\n",
 493                poolname, lov->lov_pool_count);
 494
 495         RETURN(0);
 496
 497 out_err:
 498         cfs_spin_lock(&obd->obd_dev_lock);
 499         cfs_list_del_init(&new_pool->pool_list);
 500         lov->lov_pool_count--;
 501         cfs_spin_unlock(&obd->obd_dev_lock);
 502
 503         lprocfs_remove(&new_pool->pool_proc_entry);
 504
 505         lov_ost_pool_free(&new_pool->pool_rr.lqr_pool);
 506 out_free_pool_obds:
 507         lov_ost_pool_free(&new_pool->pool_obds);
 508         OBD_FREE_PTR(new_pool);
 509         return rc;
 510 }
 511
 512 int lov_pool_del(struct obd_device *obd, char *poolname)
 513 {
 514         struct lov_obd *lov;
 515         struct pool_desc *pool;
 516         ENTRY;
 517
 518         lov = &(obd->u.lov);
 519
 520         /* lookup and kill hash reference */
 521         pool = cfs_hash_del_key(lov->lov_pools_hash_body, poolname);
 522         if (pool == NULL)
 523                 RETURN(-ENOENT);
 524
 525         if (pool->pool_proc_entry != NULL) {
 526                 CDEBUG(D_INFO, "proc entry %p\n", pool->pool_proc_entry);
 527                 lprocfs_remove(&pool->pool_proc_entry);
 528                 lov_pool_putref(pool);
 529         }
 530
 531         cfs_spin_lock(&obd->obd_dev_lock);
 532         cfs_list_del_init(&pool->pool_list);
 533         lov->lov_pool_count--;
 534         cfs_spin_unlock(&obd->obd_dev_lock);
 535
 536         /* release last reference */
 537         lov_pool_putref(pool);
 538
 539         RETURN(0);
 540 }
 541
 542
 543 int lov_pool_add(struct obd_device *obd, char *poolname, char *ostname)
 544 {
 545         struct obd_uuid ost_uuid;
 546         struct lov_obd *lov;
 547         struct pool_desc *pool;
 548         unsigned int lov_idx;
 549         int rc;
 550         ENTRY;
 551
 552         lov = &(obd->u.lov);
 553
 554         pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
 555         if (pool == NULL)
 556                 RETURN(-ENOENT);
 557
 558         obd_str2uuid(&ost_uuid, ostname);
 559
 560
 561         /* search ost in lov array */
 562         obd_getref(obd);
 563         for (lov_idx = 0; lov_idx < lov->desc.ld_tgt_count; lov_idx++) {
 564                 if (!lov->lov_tgts[lov_idx])
 565                         continue;
 566                 if (obd_uuid_equals(&ost_uuid,
 567                                     &(lov->lov_tgts[lov_idx]->ltd_uuid)))
 568                         break;
 569         }
 570         /* test if ost found in lov */
 571         if (lov_idx == lov->desc.ld_tgt_count)
 572                 GOTO(out, rc = -EINVAL);
 573
 574         rc = lov_ost_pool_add(&pool->pool_obds, lov_idx, lov->lov_tgt_size);
 575         if (rc)
 576                 GOTO(out, rc);
 577
 578         pool->pool_rr.lqr_dirty = 1;
 579
 580         CDEBUG(D_CONFIG, "Added %s to "LOV_POOLNAMEF" as member %d\n",
 581                ostname, poolname,  pool_tgt_count(pool));
 582
 583         EXIT;
 584 out:
 585         obd_putref(obd);
 586         lov_pool_putref(pool);
 587         return rc;
 588 }
 589
 590 int lov_pool_remove(struct obd_device *obd, char *poolname, char *ostname)
 591 {
 592         struct obd_uuid ost_uuid;
 593         struct lov_obd *lov;
 594         struct pool_desc *pool;
 595         unsigned int lov_idx;
 596         int rc = 0;
 597         ENTRY;
 598
 599         lov = &(obd->u.lov);
 600
 601         pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
 602         if (pool == NULL)
 603                 RETURN(-ENOENT);
 604
 605         obd_str2uuid(&ost_uuid, ostname);
 606
 607         obd_getref(obd);
 608         /* search ost in lov array, to get index */
 609         for (lov_idx = 0; lov_idx < lov->desc.ld_tgt_count; lov_idx++) {
 610                 if (!lov->lov_tgts[lov_idx])
 611                         continue;
 612
 613                 if (obd_uuid_equals(&ost_uuid,
 614                                     &(lov->lov_tgts[lov_idx]->ltd_uuid)))
 615                         break;
 616         }
 617
 618         /* test if ost found in lov */
 619         if (lov_idx == lov->desc.ld_tgt_count)
 620                 GOTO(out, rc = -EINVAL);
 621
 622         lov_ost_pool_remove(&pool->pool_obds, lov_idx);
 623
 624         pool->pool_rr.lqr_dirty = 1;
 625
 626         CDEBUG(D_CONFIG, "%s removed from "LOV_POOLNAMEF"\n", ostname,
 627                poolname);
 628
 629         EXIT;
 630 out:
 631         obd_putref(obd);
 632         lov_pool_putref(pool);
 633         return rc;
 634 }
 635
 636 int lov_check_index_in_pool(__u32 idx, struct pool_desc *pool)
 637 {
 638         int i, rc;
 639         ENTRY;
 640
 641         /* caller may no have a ref on pool if it got the pool
 642          * without calling lov_find_pool() (e.g. go through the lov pool
 643          * list)
 644          */
 645         lov_pool_getref(pool);
 646
 647         cfs_down_read(&pool_tgt_rw_sem(pool));
 648
 649         for (i = 0; i < pool_tgt_count(pool); i++) {
 650                 if (pool_tgt_array(pool)[i] == idx)
 651                         GOTO(out, rc = 0);
 652         }
 653         rc = -ENOENT;
 654         EXIT;
 655 out:
 656         cfs_up_read(&pool_tgt_rw_sem(pool));
 657
 658         lov_pool_putref(pool);
 659         return rc;
 660 }
 661
 662 struct pool_desc *lov_find_pool(struct lov_obd *lov, char *poolname)
 663 {
 664         struct pool_desc *pool;
 665
 666         pool = NULL;
 667         if (poolname[0] != '\0') {
 668                 pool = cfs_hash_lookup(lov->lov_pools_hash_body, poolname);
 669                 if (pool == NULL)
 670                         CWARN("Request for an unknown pool ("LOV_POOLNAMEF")\n",
 671                               poolname);
 672                 if ((pool != NULL) && (pool_tgt_count(pool) == 0)) {
 673                         CWARN("Request for an empty pool ("LOV_POOLNAMEF")\n",
 674                                poolname);
 675                         /* pool is ignored, so we remove ref on it */
 676                         lov_pool_putref(pool);
 677                         pool = NULL;
 678                 }
 679         }
 680         return pool;
 681 }
 682