drivers/staging/pohmelfs/trans.c

   1 /*
   2  * 2007+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
   3  * All rights reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/crypto.h>
  18 #include <linux/fs.h>
  19 #include <linux/jhash.h>
  20 #include <linux/hash.h>
  21 #include <linux/ktime.h>
  22 #include <linux/mempool.h>
  23 #include <linux/mm.h>
  24 #include <linux/mount.h>
  25 #include <linux/pagemap.h>
  26 #include <linux/parser.h>
  27 #include <linux/poll.h>
  28 #include <linux/swap.h>
  29 #include <linux/slab.h>
  30 #include <linux/statfs.h>
  31 #include <linux/writeback.h>
  32
  33 #include "netfs.h"
  34
  35 static struct kmem_cache *netfs_trans_dst;
  36 static mempool_t *netfs_trans_dst_pool;
  37
  38 static void netfs_trans_init_static(struct netfs_trans *t, int num, int size)
  39 {
  40         t->page_num = num;
  41         t->total_size = size;
  42         atomic_set(&t->refcnt, 1);
  43
  44         spin_lock_init(&t->dst_lock);
  45         INIT_LIST_HEAD(&t->dst_list);
  46 }
  47
  48 static int netfs_trans_send_pages(struct netfs_trans *t, struct netfs_state *st)
  49 {
  50         int err = 0;
  51         unsigned int i, attached_pages = t->attached_pages, ci;
  52         struct msghdr msg;
  53         struct page **pages = (t->eng)?t->eng->pages:t->pages;
  54         struct page *p;
  55         unsigned int size;
  56
  57         msg.msg_name = NULL;
  58         msg.msg_namelen = 0;
  59         msg.msg_control = NULL;
  60         msg.msg_controllen = 0;
  61         msg.msg_flags = MSG_WAITALL | MSG_MORE;
  62
  63         ci = 0;
  64         for (i=0; i<t->page_num; ++i) {
  65                 struct page *page = pages[ci];
  66                 struct netfs_cmd cmd;
  67                 struct iovec io;
  68
  69                 p = t->pages[i];
  70
  71                 if (!p)
  72                         continue;
  73
  74                 size = page_private(p);
  75
  76                 io.iov_base = &cmd;
  77                 io.iov_len = sizeof(struct netfs_cmd);
  78
  79                 cmd.cmd = NETFS_WRITE_PAGE;
  80                 cmd.ext = 0;
  81                 cmd.id = 0;
  82                 cmd.size = size;
  83                 cmd.start = p->index;
  84                 cmd.start <<= PAGE_CACHE_SHIFT;
  85                 cmd.csize = 0;
  86                 cmd.cpad = 0;
  87                 cmd.iv = pohmelfs_gen_iv(t);
  88
  89                 netfs_convert_cmd(&cmd);
  90
  91                 msg.msg_iov = &io;
  92                 msg.msg_iovlen = 1;
  93                 msg.msg_flags = MSG_WAITALL | MSG_MORE;
  94
  95                 err = kernel_sendmsg(st->socket, &msg, (struct kvec *)msg.msg_iov, 1, sizeof(struct netfs_cmd));
  96                 if (err <= 0) {
  97                         printk("%s: %d/%d failed to send transaction header: t: %p, gen: %u, err: %d.\n",
  98                                         __func__, i, t->page_num, t, t->gen, err);
  99                         if (err == 0)
 100                                 err = -ECONNRESET;
 101                         goto err_out;
 102                 }
 103
 104                 msg.msg_flags = MSG_WAITALL | (attached_pages == 1 ? 0 :
 105                                 MSG_MORE);
 106
 107                 err = kernel_sendpage(st->socket, page, 0, size, msg.msg_flags);
 108                 if (err <= 0) {
 109                         printk("%s: %d/%d failed to send transaction page: t: %p, gen: %u, size: %u, err: %d.\n",
 110                                         __func__, i, t->page_num, t, t->gen, size, err);
 111                         if (err == 0)
 112                                 err = -ECONNRESET;
 113                         goto err_out;
 114                 }
 115
 116                 dprintk("%s: %d/%d sent t: %p, gen: %u, page: %p/%p, size: %u.\n",
 117                         __func__, i, t->page_num, t, t->gen, page, p, size);
 118
 119                 err = 0;
 120                 attached_pages--;
 121                 if (!attached_pages)
 122                         break;
 123                 ci++;
 124
 125                 continue;
 126
 127 err_out:
 128                 printk("%s: t: %p, gen: %u, err: %d.\n", __func__, t, t->gen, err);
 129                 netfs_state_exit(st);
 130                 break;
 131         }
 132
 133         return err;
 134 }
 135
 136 int netfs_trans_send(struct netfs_trans *t, struct netfs_state *st)
 137 {
 138         int err;
 139         struct msghdr msg;
 140
 141         BUG_ON(!t->iovec.iov_len);
 142         BUG_ON(t->iovec.iov_len > 1024*1024*1024);
 143
 144         netfs_state_lock_send(st);
 145         if (!st->socket) {
 146                 err = netfs_state_init(st);
 147                 if (err)
 148                         goto err_out_unlock_return;
 149         }
 150
 151         msg.msg_iov = &t->iovec;
 152         msg.msg_iovlen = 1;
 153         msg.msg_name = NULL;
 154         msg.msg_namelen = 0;
 155         msg.msg_control = NULL;
 156         msg.msg_controllen = 0;
 157         msg.msg_flags = MSG_WAITALL;
 158
 159         if (t->attached_pages)
 160                 msg.msg_flags |= MSG_MORE;
 161
 162         err = kernel_sendmsg(st->socket, &msg, (struct kvec *)msg.msg_iov, 1, t->iovec.iov_len);
 163         if (err <= 0) {
 164                 printk("%s: failed to send contig transaction: t: %p, gen: %u, size: %zu, err: %d.\n",
 165                                 __func__, t, t->gen, t->iovec.iov_len, err);
 166                 if (err == 0)
 167                         err = -ECONNRESET;
 168                 goto err_out_unlock_return;
 169         }
 170
 171         dprintk("%s: sent %s transaction: t: %p, gen: %u, size: %zu, page_num: %u.\n",
 172                         __func__, (t->page_num)?"partial":"full",
 173                         t, t->gen, t->iovec.iov_len, t->page_num);
 174
 175         err = 0;
 176         if (t->attached_pages)
 177                 err = netfs_trans_send_pages(t, st);
 178
 179 err_out_unlock_return:
 180
 181         if (st->need_reset)
 182                 netfs_state_exit(st);
 183
 184         netfs_state_unlock_send(st);
 185
 186         dprintk("%s: t: %p, gen: %u, err: %d.\n",
 187                 __func__, t, t->gen, err);
 188
 189         t->result = err;
 190         return err;
 191 }
 192
 193 static inline int netfs_trans_cmp(unsigned int gen, unsigned int new)
 194 {
 195         if (gen < new)
 196                 return 1;
 197         if (gen > new)
 198                 return -1;
 199         return 0;
 200 }
 201
 202 struct netfs_trans_dst *netfs_trans_search(struct netfs_state *st, unsigned int gen)
 203 {
 204         struct rb_root *root = &st->trans_root;
 205         struct rb_node *n = root->rb_node;
 206         struct netfs_trans_dst *tmp, *ret = NULL;
 207         struct netfs_trans *t;
 208         int cmp;
 209
 210         while (n) {
 211                 tmp = rb_entry(n, struct netfs_trans_dst, state_entry);
 212                 t = tmp->trans;
 213
 214                 cmp = netfs_trans_cmp(t->gen, gen);
 215                 if (cmp < 0)
 216                         n = n->rb_left;
 217                 else if (cmp > 0)
 218                         n = n->rb_right;
 219                 else {
 220                         ret = tmp;
 221                         break;
 222                 }
 223         }
 224
 225         return ret;
 226 }
 227
 228 static int netfs_trans_insert(struct netfs_trans_dst *ndst, struct netfs_state *st)
 229 {
 230         struct rb_root *root = &st->trans_root;
 231         struct rb_node **n = &root->rb_node, *parent = NULL;
 232         struct netfs_trans_dst *ret = NULL, *tmp;
 233         struct netfs_trans *t = NULL, *new = ndst->trans;
 234         int cmp;
 235
 236         while (*n) {
 237                 parent = *n;
 238
 239                 tmp = rb_entry(parent, struct netfs_trans_dst, state_entry);
 240                 t = tmp->trans;
 241
 242                 cmp = netfs_trans_cmp(t->gen, new->gen);
 243                 if (cmp < 0)
 244                         n = &parent->rb_left;
 245                 else if (cmp > 0)
 246                         n = &parent->rb_right;
 247                 else {
 248                         ret = tmp;
 249                         break;
 250                 }
 251         }
 252
 253         if (ret) {
 254                 printk("%s: exist: old: gen: %u, flags: %x, send_time: %lu, "
 255                                 "new: gen: %u, flags: %x, send_time: %lu.\n",
 256                         __func__, t->gen, t->flags, ret->send_time,
 257                         new->gen, new->flags, ndst->send_time);
 258                 return -EEXIST;
 259         }
 260
 261         rb_link_node(&ndst->state_entry, parent, n);
 262         rb_insert_color(&ndst->state_entry, root);
 263         ndst->send_time = jiffies;
 264
 265         return 0;
 266 }
 267
 268 int netfs_trans_remove_nolock(struct netfs_trans_dst *dst, struct netfs_state *st)
 269 {
 270         if (dst && dst->state_entry.rb_parent_color) {
 271                 rb_erase(&dst->state_entry, &st->trans_root);
 272                 dst->state_entry.rb_parent_color = 0;
 273                 return 1;
 274         }
 275         return 0;
 276 }
 277
 278 static int netfs_trans_remove_state(struct netfs_trans_dst *dst)
 279 {
 280         int ret;
 281         struct netfs_state *st = dst->state;
 282
 283         mutex_lock(&st->trans_lock);
 284         ret = netfs_trans_remove_nolock(dst, st);
 285         mutex_unlock(&st->trans_lock);
 286
 287         return ret;
 288 }
 289
 290 /*
 291  * Create new destination for given transaction associated with given network state.
 292  * Transaction's reference counter is bumped and will be dropped when either
 293  * reply is received or when async timeout detection task will fail resending
 294  * and drop transaction.
 295  */
 296 static int netfs_trans_push_dst(struct netfs_trans *t, struct netfs_state *st)
 297 {
 298         struct netfs_trans_dst *dst;
 299         int err;
 300
 301         dst = mempool_alloc(netfs_trans_dst_pool, GFP_KERNEL);
 302         if (!dst)
 303                 return -ENOMEM;
 304
 305         dst->retries = 0;
 306         dst->send_time = 0;
 307         dst->state = st;
 308         dst->trans = t;
 309         netfs_trans_get(t);
 310
 311         mutex_lock(&st->trans_lock);
 312         err = netfs_trans_insert(dst, st);
 313         mutex_unlock(&st->trans_lock);
 314
 315         if (err)
 316                 goto err_out_free;
 317
 318         spin_lock(&t->dst_lock);
 319         list_add_tail(&dst->trans_entry, &t->dst_list);
 320         spin_unlock(&t->dst_lock);
 321
 322         return 0;
 323
 324 err_out_free:
 325         t->result = err;
 326         netfs_trans_put(t);
 327         mempool_free(dst, netfs_trans_dst_pool);
 328         return err;
 329 }
 330
 331 static void netfs_trans_free_dst(struct netfs_trans_dst *dst)
 332 {
 333         netfs_trans_put(dst->trans);
 334         mempool_free(dst, netfs_trans_dst_pool);
 335 }
 336
 337 static void netfs_trans_remove_dst(struct netfs_trans_dst *dst)
 338 {
 339         if (netfs_trans_remove_state(dst))
 340                 netfs_trans_free_dst(dst);
 341 }
 342
 343 /*
 344  * Drop destination transaction entry when we know it.
 345  */
 346 void netfs_trans_drop_dst(struct netfs_trans_dst *dst)
 347 {
 348         struct netfs_trans *t = dst->trans;
 349
 350         spin_lock(&t->dst_lock);
 351         list_del_init(&dst->trans_entry);
 352         spin_unlock(&t->dst_lock);
 353
 354         netfs_trans_remove_dst(dst);
 355 }
 356
 357 /*
 358  * Drop destination transaction entry when we know it and when we
 359  * already removed dst from state tree.
 360  */
 361 void netfs_trans_drop_dst_nostate(struct netfs_trans_dst *dst)
 362 {
 363         struct netfs_trans *t = dst->trans;
 364
 365         spin_lock(&t->dst_lock);
 366         list_del_init(&dst->trans_entry);
 367         spin_unlock(&t->dst_lock);
 368
 369         netfs_trans_free_dst(dst);
 370 }
 371
 372 /*
 373  * This drops destination transaction entry from appropriate network state
 374  * tree and drops related reference counter. It is possible that transaction
 375  * will be freed here if its reference counter hits zero.
 376  * Destination transaction entry will be freed.
 377  */
 378 void netfs_trans_drop_trans(struct netfs_trans *t, struct netfs_state *st)
 379 {
 380         struct netfs_trans_dst *dst, *tmp, *ret = NULL;
 381
 382         spin_lock(&t->dst_lock);
 383         list_for_each_entry_safe(dst, tmp, &t->dst_list, trans_entry) {
 384                 if (dst->state == st) {
 385                         ret = dst;
 386                         list_del(&dst->trans_entry);
 387                         break;
 388                 }
 389         }
 390         spin_unlock(&t->dst_lock);
 391
 392         if (ret)
 393                 netfs_trans_remove_dst(ret);
 394 }
 395
 396 /*
 397  * This drops destination transaction entry from appropriate network state
 398  * tree and drops related reference counter. It is possible that transaction
 399  * will be freed here if its reference counter hits zero.
 400  * Destination transaction entry will be freed.
 401  */
 402 void netfs_trans_drop_last(struct netfs_trans *t, struct netfs_state *st)
 403 {
 404         struct netfs_trans_dst *dst, *tmp, *ret;
 405
 406         spin_lock(&t->dst_lock);
 407         ret = list_entry(t->dst_list.prev, struct netfs_trans_dst, trans_entry);
 408         if (ret->state != st) {
 409                 ret = NULL;
 410                 list_for_each_entry_safe(dst, tmp, &t->dst_list, trans_entry) {
 411                         if (dst->state == st) {
 412                                 ret = dst;
 413                                 list_del_init(&dst->trans_entry);
 414                                 break;
 415                         }
 416                 }
 417         } else {
 418                 list_del(&ret->trans_entry);
 419         }
 420         spin_unlock(&t->dst_lock);
 421
 422         if (ret)
 423                 netfs_trans_remove_dst(ret);
 424 }
 425
 426 static int netfs_trans_push(struct netfs_trans *t, struct netfs_state *st)
 427 {
 428         int err;
 429
 430         err = netfs_trans_push_dst(t, st);
 431         if (err)
 432                 return err;
 433
 434         err = netfs_trans_send(t, st);
 435         if (err)
 436                 goto err_out_free;
 437
 438         if (t->flags & NETFS_TRANS_SINGLE_DST)
 439                 pohmelfs_switch_active(st->psb);
 440
 441         return 0;
 442
 443 err_out_free:
 444         t->result = err;
 445         netfs_trans_drop_last(t, st);
 446
 447         return err;
 448 }
 449
 450 int netfs_trans_finish_send(struct netfs_trans *t, struct pohmelfs_sb *psb)
 451 {
 452         struct pohmelfs_config *c;
 453         int err = -ENODEV;
 454         struct netfs_state *st;
 455 #if 0
 456         dprintk("%s: t: %p, gen: %u, size: %u, page_num: %u, active: %p.\n",
 457                 __func__, t, t->gen, t->iovec.iov_len, t->page_num, psb->active_state);
 458 #endif
 459         mutex_lock(&psb->state_lock);
 460         list_for_each_entry(c, &psb->state_list, config_entry) {
 461                 st = &c->state;
 462
 463                 if (t->flags & NETFS_TRANS_SINGLE_DST) {
 464                         if (!(st->ctl.perm & POHMELFS_IO_PERM_READ))
 465                                 continue;
 466                 } else {
 467                         if (!(st->ctl.perm & POHMELFS_IO_PERM_WRITE))
 468                                 continue;
 469                 }
 470
 471                 if (psb->active_state && (psb->active_state->state.ctl.prio >= st->ctl.prio) &&
 472                                 (t->flags & NETFS_TRANS_SINGLE_DST))
 473                         st = &psb->active_state->state;
 474
 475                 err = netfs_trans_push(t, st);
 476                 if (!err && (t->flags & NETFS_TRANS_SINGLE_DST))
 477                         break;
 478         }
 479
 480         mutex_unlock(&psb->state_lock);
 481 #if 0
 482         dprintk("%s: fully sent t: %p, gen: %u, size: %u, page_num: %u, err: %d.\n",
 483                 __func__, t, t->gen, t->iovec.iov_len, t->page_num, err);
 484 #endif
 485         if (err)
 486                 t->result = err;
 487         return err;
 488 }
 489
 490 int netfs_trans_finish(struct netfs_trans *t, struct pohmelfs_sb *psb)
 491 {
 492         int err;
 493         struct netfs_cmd *cmd = t->iovec.iov_base;
 494
 495         t->gen = atomic_inc_return(&psb->trans_gen);
 496
 497         cmd->size = t->iovec.iov_len - sizeof(struct netfs_cmd) +
 498                 t->attached_size + t->attached_pages * sizeof(struct netfs_cmd);
 499         cmd->cmd = NETFS_TRANS;
 500         cmd->start = t->gen;
 501         cmd->id = 0;
 502
 503         if (psb->perform_crypto) {
 504                 cmd->ext = psb->crypto_attached_size;
 505                 cmd->csize = psb->crypto_attached_size;
 506         }
 507
 508         dprintk("%s: t: %u, size: %u, iov_len: %zu, attached_size: %u, attached_pages: %u.\n",
 509                         __func__, t->gen, cmd->size, t->iovec.iov_len, t->attached_size, t->attached_pages);
 510         err = pohmelfs_trans_crypt(t, psb);
 511         if (err) {
 512                 t->result = err;
 513                 netfs_convert_cmd(cmd);
 514                 dprintk("%s: trans: %llu, crypto_attached_size: %u, attached_size: %u, attached_pages: %d, trans_size: %u, err: %d.\n",
 515                         __func__, cmd->start, psb->crypto_attached_size, t->attached_size, t->attached_pages, cmd->size, err);
 516         }
 517         netfs_trans_put(t);
 518         return err;
 519 }
 520
 521 /*
 522  * Resend transaction to remote server(s).
 523  * If new servers were added into superblock, we can try to send data
 524  * to them too.
 525  *
 526  * It is called under superblock's state_lock, so we can safely
 527  * dereference psb->state_list. Also, transaction's reference counter is
 528  * bumped, so it can not go away under us, thus we can safely access all
 529  * its members. State is locked.
 530  *
 531  * This function returns 0 if transaction was successfully sent to at
 532  * least one destination target.
 533  */
 534 int netfs_trans_resend(struct netfs_trans *t, struct pohmelfs_sb *psb)
 535 {
 536         struct netfs_trans_dst *dst;
 537         struct netfs_state *st;
 538         struct pohmelfs_config *c;
 539         int err, exist, error = -ENODEV;
 540
 541         list_for_each_entry(c, &psb->state_list, config_entry) {
 542                 st = &c->state;
 543
 544                 exist = 0;
 545                 spin_lock(&t->dst_lock);
 546                 list_for_each_entry(dst, &t->dst_list, trans_entry) {
 547                         if (st == dst->state) {
 548                                 exist = 1;
 549                                 break;
 550                         }
 551                 }
 552                 spin_unlock(&t->dst_lock);
 553
 554                 if (exist) {
 555                         if (!(t->flags & NETFS_TRANS_SINGLE_DST) ||
 556                                         (c->config_entry.next == &psb->state_list)) {
 557                                 dprintk("%s: resending st: %p, t: %p, gen: %u.\n",
 558                                                 __func__, st, t, t->gen);
 559                                 err = netfs_trans_send(t, st);
 560                                 if (!err)
 561                                         error = 0;
 562                         }
 563                         continue;
 564                 }
 565
 566                 dprintk("%s: pushing/resending st: %p, t: %p, gen: %u.\n",
 567                                 __func__, st, t, t->gen);
 568                 err = netfs_trans_push(t, st);
 569                 if (err)
 570                         continue;
 571                 error = 0;
 572                 if (t->flags & NETFS_TRANS_SINGLE_DST)
 573                         break;
 574         }
 575
 576         t->result = error;
 577         return error;
 578 }
 579
 580 void *netfs_trans_add(struct netfs_trans *t, unsigned int size)
 581 {
 582         struct iovec *io = &t->iovec;
 583         void *ptr;
 584
 585         if (size > t->total_size) {
 586                 ptr = ERR_PTR(-EINVAL);
 587                 goto out;
 588         }
 589
 590         if (io->iov_len + size > t->total_size) {
 591                 dprintk("%s: too big size t: %p, gen: %u, iov_len: %zu, size: %u, total: %u.\n",
 592                                 __func__, t, t->gen, io->iov_len, size, t->total_size);
 593                 ptr = ERR_PTR(-E2BIG);
 594                 goto out;
 595         }
 596
 597         ptr = io->iov_base + io->iov_len;
 598         io->iov_len += size;
 599
 600 out:
 601         dprintk("%s: t: %p, gen: %u, size: %u, total: %zu.\n",
 602                 __func__, t, t->gen, size, io->iov_len);
 603         return ptr;
 604 }
 605
 606 void netfs_trans_free(struct netfs_trans *t)
 607 {
 608         if (t->eng)
 609                 pohmelfs_crypto_thread_make_ready(t->eng->thread);
 610         kfree(t);
 611 }
 612
 613 struct netfs_trans *netfs_trans_alloc(struct pohmelfs_sb *psb, unsigned int size,
 614                 unsigned int flags, unsigned int nr)
 615 {
 616         struct netfs_trans *t;
 617         unsigned int num, cont, pad, size_no_trans;
 618         unsigned int crypto_added = 0;
 619         struct netfs_cmd *cmd;
 620
 621         if (psb->perform_crypto)
 622                 crypto_added = psb->crypto_attached_size;
 623
 624         /*
 625          * |sizeof(struct netfs_trans)|
 626          * |sizeof(struct netfs_cmd)| - transaction header
 627          * |size| - buffer with requested size
 628          * |padding| - crypto padding, zero bytes
 629          * |nr * sizeof(struct page *)| - array of page pointers
 630          *
 631          * Overall size should be less than PAGE_SIZE for guaranteed allocation.
 632          */
 633
 634         cont = size;
 635         size = ALIGN(size, psb->crypto_align_size);
 636         pad = size - cont;
 637
 638         size_no_trans = size + sizeof(struct netfs_cmd) * 2 + crypto_added;
 639
 640         cont = sizeof(struct netfs_trans) + size_no_trans;
 641
 642         num = (PAGE_SIZE - cont)/sizeof(struct page *);
 643
 644         if (nr > num)
 645                 nr = num;
 646
 647         t = kzalloc(cont + nr*sizeof(struct page *), GFP_NOIO);
 648         if (!t)
 649                 goto err_out_exit;
 650
 651         t->iovec.iov_base = (void *)(t + 1);
 652         t->pages = (struct page **)(t->iovec.iov_base + size_no_trans);
 653
 654         /*
 655          * Reserving space for transaction header.
 656          */
 657         t->iovec.iov_len = sizeof(struct netfs_cmd) + crypto_added;
 658
 659         netfs_trans_init_static(t, nr, size_no_trans);
 660
 661         t->flags = flags;
 662         t->psb = psb;
 663
 664         cmd = (struct netfs_cmd *)t->iovec.iov_base;
 665
 666         cmd->size = size;
 667         cmd->cpad = pad;
 668         cmd->csize = crypto_added;
 669
 670         dprintk("%s: t: %p, gen: %u, size: %u, padding: %u, align_size: %u, flags: %x, "
 671                         "page_num: %u, base: %p, pages: %p.\n",
 672                         __func__, t, t->gen, size, pad, psb->crypto_align_size, flags, nr,
 673                         t->iovec.iov_base, t->pages);
 674
 675         return t;
 676
 677 err_out_exit:
 678         return NULL;
 679 }
 680
 681 int netfs_trans_init(void)
 682 {
 683         int err = -ENOMEM;
 684
 685         netfs_trans_dst = kmem_cache_create("netfs_trans_dst", sizeof(struct netfs_trans_dst),
 686                         0, 0, NULL);
 687         if (!netfs_trans_dst)
 688                 goto err_out_exit;
 689
 690         netfs_trans_dst_pool = mempool_create_slab_pool(256, netfs_trans_dst);
 691         if (!netfs_trans_dst_pool)
 692                 goto err_out_free;
 693
 694         return 0;
 695
 696 err_out_free:
 697         kmem_cache_destroy(netfs_trans_dst);
 698 err_out_exit:
 699         return err;
 700 }
 701
 702 void netfs_trans_exit(void)
 703 {
 704         mempool_destroy(netfs_trans_dst_pool);
 705         kmem_cache_destroy(netfs_trans_dst);
 706 }