drivers/xen/blkback/blkback.c

   1 /******************************************************************************
   2  * arch/xen/drivers/blkif/backend/main.c
   3  *
   4  * Back-end of the driver for virtual block devices. This portion of the
   5  * driver exports a 'unified' block-device interface that can be accessed
   6  * by any operating system that implements a compatible front end. A
   7  * reference front-end implementation can be found in:
   8  *  arch/xen/drivers/blkif/frontend
   9  *
  10  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
  11  * Copyright (c) 2005, Christopher Clark
  12  *
  13  * This program is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU General Public License version 2
  15  * as published by the Free Software Foundation; or, when distributed
  16  * separately from the Linux kernel or incorporated into other
  17  * software packages, subject to the following license:
  18  *
  19  * Permission is hereby granted, free of charge, to any person obtaining a copy
  20  * of this source file (the "Software"), to deal in the Software without
  21  * restriction, including without limitation the rights to use, copy, modify,
  22  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  23  * and to permit persons to whom the Software is furnished to do so, subject to
  24  * the following conditions:
  25  *
  26  * The above copyright notice and this permission notice shall be included in
  27  * all copies or substantial portions of the Software.
  28  *
  29  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  30  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  31  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  32  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  33  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  34  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  35  * IN THE SOFTWARE.
  36  */
  37
  38 #include <linux/spinlock.h>
  39 #include <linux/kthread.h>
  40 #include <linux/list.h>
  41 #include <linux/delay.h>
  42 #include <xen/balloon.h>
  43 #include <asm/hypervisor.h>
  44 #include "common.h"
  45
  46 /*
  47  * These are rather arbitrary. They are fairly large because adjacent requests
  48  * pulled from a communication ring are quite likely to end up being part of
  49  * the same scatter/gather request at the disc.
  50  *
  51  * ** TRY INCREASING 'blkif_reqs' IF WRITE SPEEDS SEEM TOO LOW **
  52  *
  53  * This will increase the chances of being able to write whole tracks.
  54  * 64 should be enough to keep us competitive with Linux.
  55  */
  56 static int blkif_reqs = 64;
  57 module_param_named(reqs, blkif_reqs, int, 0);
  58 MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate");
  59
  60 /* Run-time switchable: /sys/module/blkback/parameters/ */
  61 static unsigned int log_stats = 0;
  62 static unsigned int debug_lvl = 0;
  63 module_param(log_stats, int, 0644);
  64 module_param(debug_lvl, int, 0644);
  65
  66 /*
  67  * Each outstanding request that we've passed to the lower device layers has a
  68  * 'pending_req' allocated to it. Each buffer_head that completes decrements
  69  * the pendcnt towards zero. When it hits zero, the specified domain has a
  70  * response queued for it, with the saved 'id' passed back.
  71  */
  72 typedef struct {
  73         blkif_t       *blkif;
  74         u64            id;
  75         int            nr_pages;
  76         atomic_t       pendcnt;
  77         unsigned short operation;
  78         int            status;
  79         struct list_head free_list;
  80 } pending_req_t;
  81
  82 static pending_req_t *pending_reqs;
  83 static struct list_head pending_free;
  84 static DEFINE_SPINLOCK(pending_free_lock);
  85 static DECLARE_WAIT_QUEUE_HEAD(pending_free_wq);
  86
  87 #define BLKBACK_INVALID_HANDLE (~0)
  88
  89 static struct page **pending_pages;
  90 static grant_handle_t *pending_grant_handles;
  91
  92 static inline int vaddr_pagenr(pending_req_t *req, int seg)
  93 {
  94         return (req - pending_reqs) * BLKIF_MAX_SEGMENTS_PER_REQUEST + seg;
  95 }
  96
  97 static inline unsigned long vaddr(pending_req_t *req, int seg)
  98 {
  99         unsigned long pfn = page_to_pfn(pending_pages[vaddr_pagenr(req, seg)]);
 100         return (unsigned long)pfn_to_kaddr(pfn);
 101 }
 102
 103 #define pending_handle(_req, _seg) \
 104         (pending_grant_handles[vaddr_pagenr(_req, _seg)])
 105
 106
 107 static int do_block_io_op(blkif_t *blkif);
 108 static void dispatch_rw_block_io(blkif_t *blkif,
 109                                  blkif_request_t *req,
 110                                  pending_req_t *pending_req);
 111 static void make_response(blkif_t *blkif, u64 id,
 112                           unsigned short op, int st);
 113
 114 /******************************************************************
 115  * misc small helpers
 116  */
 117 static pending_req_t* alloc_req(void)
 118 {
 119         pending_req_t *req = NULL;
 120         unsigned long flags;
 121
 122         spin_lock_irqsave(&pending_free_lock, flags);
 123         if (!list_empty(&pending_free)) {
 124                 req = list_entry(pending_free.next, pending_req_t, free_list);
 125                 list_del(&req->free_list);
 126         }
 127         spin_unlock_irqrestore(&pending_free_lock, flags);
 128         return req;
 129 }
 130
 131 static void free_req(pending_req_t *req)
 132 {
 133         unsigned long flags;
 134         int was_empty;
 135
 136         spin_lock_irqsave(&pending_free_lock, flags);
 137         was_empty = list_empty(&pending_free);
 138         list_add(&req->free_list, &pending_free);
 139         spin_unlock_irqrestore(&pending_free_lock, flags);
 140         if (was_empty)
 141                 wake_up(&pending_free_wq);
 142 }
 143
 144 static void unplug_queue(blkif_t *blkif)
 145 {
 146         if (blkif->plug == NULL)
 147                 return;
 148         if (blkif->plug->unplug_fn)
 149                 blkif->plug->unplug_fn(blkif->plug);
 150         blk_put_queue(blkif->plug);
 151         blkif->plug = NULL;
 152 }
 153
 154 static void plug_queue(blkif_t *blkif, struct block_device *bdev)
 155 {
 156         request_queue_t *q = bdev_get_queue(bdev);
 157
 158         if (q == blkif->plug)
 159                 return;
 160         unplug_queue(blkif);
 161         blk_get_queue(q);
 162         blkif->plug = q;
 163 }
 164
 165 static void fast_flush_area(pending_req_t *req)
 166 {
 167         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 168         unsigned int i, invcount = 0;
 169         grant_handle_t handle;
 170         int ret;
 171
 172         for (i = 0; i < req->nr_pages; i++) {
 173                 handle = pending_handle(req, i);
 174                 if (handle == BLKBACK_INVALID_HANDLE)
 175                         continue;
 176                 gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
 177                                     GNTMAP_host_map, handle);
 178                 pending_handle(req, i) = BLKBACK_INVALID_HANDLE;
 179                 invcount++;
 180         }
 181
 182         ret = HYPERVISOR_grant_table_op(
 183                 GNTTABOP_unmap_grant_ref, unmap, invcount);
 184         BUG_ON(ret);
 185 }
 186
 187 /******************************************************************
 188  * SCHEDULER FUNCTIONS
 189  */
 190
 191 static void print_stats(blkif_t *blkif)
 192 {
 193         printk(KERN_DEBUG "%s: oo %3d  |  rd %4d  |  wr %4d  |  br %4d\n",
 194                current->comm, blkif->st_oo_req,
 195                blkif->st_rd_req, blkif->st_wr_req, blkif->st_br_req);
 196         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 197         blkif->st_rd_req = 0;
 198         blkif->st_wr_req = 0;
 199         blkif->st_oo_req = 0;
 200 }
 201
 202 int blkif_schedule(void *arg)
 203 {
 204         blkif_t *blkif = arg;
 205
 206         blkif_get(blkif);
 207
 208         if (debug_lvl)
 209                 printk(KERN_DEBUG "%s: started\n", current->comm);
 210
 211         while (!kthread_should_stop()) {
 212                 if (try_to_freeze())
 213                         continue;
 214
 215                 wait_event_interruptible(
 216                         blkif->wq,
 217                         blkif->waiting_reqs || kthread_should_stop());
 218                 wait_event_interruptible(
 219                         pending_free_wq,
 220                         !list_empty(&pending_free) || kthread_should_stop());
 221
 222                 blkif->waiting_reqs = 0;
 223                 smp_mb(); /* clear flag *before* checking for work */
 224
 225                 if (do_block_io_op(blkif))
 226                         blkif->waiting_reqs = 1;
 227                 unplug_queue(blkif);
 228
 229                 if (log_stats && time_after(jiffies, blkif->st_print))
 230                         print_stats(blkif);
 231         }
 232
 233         if (log_stats)
 234                 print_stats(blkif);
 235         if (debug_lvl)
 236                 printk(KERN_DEBUG "%s: exiting\n", current->comm);
 237
 238         blkif->xenblkd = NULL;
 239         blkif_put(blkif);
 240
 241         return 0;
 242 }
 243
 244 /******************************************************************
 245  * COMPLETION CALLBACK -- Called as bh->b_end_io()
 246  */
 247
 248 static void __end_block_io_op(pending_req_t *pending_req, int error)
 249 {
 250         /* An error fails the entire request. */
 251         if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
 252             (error == -EOPNOTSUPP)) {
 253                 DPRINTK("blkback: write barrier op failed, not supported\n");
 254                 blkback_barrier(XBT_NIL, pending_req->blkif->be, 0);
 255                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 256         } else if (error) {
 257                 DPRINTK("Buffer not up-to-date at end of operation, "
 258                         "error=%d\n", error);
 259                 pending_req->status = BLKIF_RSP_ERROR;
 260         }
 261
 262         if (atomic_dec_and_test(&pending_req->pendcnt)) {
 263                 fast_flush_area(pending_req);
 264                 make_response(pending_req->blkif, pending_req->id,
 265                               pending_req->operation, pending_req->status);
 266                 blkif_put(pending_req->blkif);
 267                 free_req(pending_req);
 268         }
 269 }
 270
 271 static int end_block_io_op(struct bio *bio, unsigned int done, int error)
 272 {
 273         if (bio->bi_size != 0)
 274                 return 1;
 275         __end_block_io_op(bio->bi_private, error);
 276         bio_put(bio);
 277         return error;
 278 }
 279
 280
 281 /******************************************************************************
 282  * NOTIFICATION FROM GUEST OS.
 283  */
 284
 285 static void blkif_notify_work(blkif_t *blkif)
 286 {
 287         blkif->waiting_reqs = 1;
 288         wake_up(&blkif->wq);
 289 }
 290
 291 irqreturn_t blkif_be_int(int irq, void *dev_id, struct pt_regs *regs)
 292 {
 293         blkif_notify_work(dev_id);
 294         return IRQ_HANDLED;
 295 }
 296
 297
 298
 299 /******************************************************************
 300  * DOWNWARD CALLS -- These interface with the block-device layer proper.
 301  */
 302
 303 static int do_block_io_op(blkif_t *blkif)
 304 {
 305         blkif_back_rings_t *blk_rings = &blkif->blk_rings;
 306         blkif_request_t req;
 307         pending_req_t *pending_req;
 308         RING_IDX rc, rp;
 309         int more_to_do = 0;
 310
 311         rc = blk_rings->common.req_cons;
 312         rp = blk_rings->common.sring->req_prod;
 313         rmb(); /* Ensure we see queued requests up to 'rp'. */
 314
 315         while (rc != rp) {
 316
 317                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
 318                         break;
 319
 320                 pending_req = alloc_req();
 321                 if (NULL == pending_req) {
 322                         blkif->st_oo_req++;
 323                         more_to_do = 1;
 324                         break;
 325                 }
 326
 327                 if (kthread_should_stop()) {
 328                         more_to_do = 1;
 329                         break;
 330                 }
 331
 332                 switch (blkif->blk_protocol) {
 333                 case BLKIF_PROTOCOL_NATIVE:
 334                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
 335                         break;
 336                 case BLKIF_PROTOCOL_X86_32:
 337                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
 338                         break;
 339                 case BLKIF_PROTOCOL_X86_64:
 340                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
 341                         break;
 342                 default:
 343                         BUG();
 344                 }
 345                 blk_rings->common.req_cons = ++rc; /* before make_response() */
 346
 347                 /* Apply all sanity checks to /private copy/ of request. */
 348                 barrier();
 349
 350                 switch (req.operation) {
 351                 case BLKIF_OP_READ:
 352                         blkif->st_rd_req++;
 353                         dispatch_rw_block_io(blkif, &req, pending_req);
 354                         break;
 355                 case BLKIF_OP_WRITE_BARRIER:
 356                         blkif->st_br_req++;
 357                         /* fall through */
 358                 case BLKIF_OP_WRITE:
 359                         blkif->st_wr_req++;
 360                         dispatch_rw_block_io(blkif, &req, pending_req);
 361                         break;
 362                 default:
 363                         /* A good sign something is wrong: sleep for a while to
 364                          * avoid excessive CPU consumption by a bad guest. */
 365                         msleep(1);
 366                         DPRINTK("error: unknown block io operation [%d]\n",
 367                                 req.operation);
 368                         make_response(blkif, req.id, req.operation,
 369                                       BLKIF_RSP_ERROR);
 370                         free_req(pending_req);
 371                         break;
 372                 }
 373
 374                 /* Yield point for this unbounded loop. */
 375                 cond_resched();
 376         }
 377
 378         return more_to_do;
 379 }
 380
 381 static void dispatch_rw_block_io(blkif_t *blkif,
 382                                  blkif_request_t *req,
 383                                  pending_req_t *pending_req)
 384 {
 385         extern void ll_rw_block(int rw, int nr, struct buffer_head * bhs[]);
 386         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 387         struct phys_req preq;
 388         struct {
 389                 unsigned long buf; unsigned int nsec;
 390         } seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 391         unsigned int nseg;
 392         struct bio *bio = NULL;
 393         int ret, i;
 394         int operation;
 395
 396         switch (req->operation) {
 397         case BLKIF_OP_READ:
 398                 operation = READ;
 399                 break;
 400         case BLKIF_OP_WRITE:
 401                 operation = WRITE;
 402                 break;
 403         case BLKIF_OP_WRITE_BARRIER:
 404                 operation = WRITE_BARRIER;
 405                 break;
 406         default:
 407                 operation = 0; /* make gcc happy */
 408                 BUG();
 409         }
 410
 411         /* Check that number of segments is sane. */
 412         nseg = req->nr_segments;
 413         if (unlikely(nseg == 0 && operation != WRITE_BARRIER) ||
 414             unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
 415                 DPRINTK("Bad number of segments in request (%d)\n", nseg);
 416                 goto fail_response;
 417         }
 418
 419         preq.dev           = req->handle;
 420         preq.sector_number = req->sector_number;
 421         preq.nr_sects      = 0;
 422
 423         pending_req->blkif     = blkif;
 424         pending_req->id        = req->id;
 425         pending_req->operation = req->operation;
 426         pending_req->status    = BLKIF_RSP_OKAY;
 427         pending_req->nr_pages  = nseg;
 428
 429         for (i = 0; i < nseg; i++) {
 430                 uint32_t flags;
 431
 432                 seg[i].nsec = req->seg[i].last_sect -
 433                         req->seg[i].first_sect + 1;
 434
 435                 if ((req->seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
 436                     (req->seg[i].last_sect < req->seg[i].first_sect))
 437                         goto fail_response;
 438                 preq.nr_sects += seg[i].nsec;
 439
 440                 flags = GNTMAP_host_map;
 441                 if (operation != READ)
 442                         flags |= GNTMAP_readonly;
 443                 gnttab_set_map_op(&map[i], vaddr(pending_req, i), flags,
 444                                   req->seg[i].gref, blkif->domid);
 445         }
 446
 447         ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, nseg);
 448         BUG_ON(ret);
 449
 450         for (i = 0; i < nseg; i++) {
 451                 if (unlikely(map[i].status != 0)) {
 452                         DPRINTK("invalid buffer -- could not remap it\n");
 453                         map[i].handle = BLKBACK_INVALID_HANDLE;
 454                         ret |= 1;
 455                 }
 456
 457                 pending_handle(pending_req, i) = map[i].handle;
 458
 459                 if (ret)
 460                         continue;
 461
 462                 set_phys_to_machine(__pa(vaddr(
 463                         pending_req, i)) >> PAGE_SHIFT,
 464                         FOREIGN_FRAME(map[i].dev_bus_addr >> PAGE_SHIFT));
 465                 seg[i].buf  = map[i].dev_bus_addr |
 466                         (req->seg[i].first_sect << 9);
 467         }
 468
 469         if (ret)
 470                 goto fail_flush;
 471
 472         if (vbd_translate(&preq, blkif, operation) != 0) {
 473                 DPRINTK("access denied: %s of [%llu,%llu] on dev=%04x\n",
 474                         operation == READ ? "read" : "write",
 475                         preq.sector_number,
 476                         preq.sector_number + preq.nr_sects, preq.dev);
 477                 goto fail_flush;
 478         }
 479
 480         plug_queue(blkif, preq.bdev);
 481         atomic_set(&pending_req->pendcnt, 1);
 482         blkif_get(blkif);
 483
 484         for (i = 0; i < nseg; i++) {
 485                 if (((int)preq.sector_number|(int)seg[i].nsec) &
 486                     ((bdev_hardsect_size(preq.bdev) >> 9) - 1)) {
 487                         DPRINTK("Misaligned I/O request from domain %d",
 488                                 blkif->domid);
 489                         goto fail_put_bio;
 490                 }
 491
 492                 while ((bio == NULL) ||
 493                        (bio_add_page(bio,
 494                                      virt_to_page(vaddr(pending_req, i)),
 495                                      seg[i].nsec << 9,
 496                                      seg[i].buf & ~PAGE_MASK) == 0)) {
 497                         if (bio) {
 498                                 atomic_inc(&pending_req->pendcnt);
 499                                 submit_bio(operation, bio);
 500                         }
 501
 502                         bio = bio_alloc(GFP_KERNEL, nseg-i);
 503                         if (unlikely(bio == NULL))
 504                                 goto fail_put_bio;
 505
 506                         bio->bi_bdev    = preq.bdev;
 507                         bio->bi_private = pending_req;
 508                         bio->bi_end_io  = end_block_io_op;
 509                         bio->bi_sector  = preq.sector_number;
 510                 }
 511
 512                 preq.sector_number += seg[i].nsec;
 513         }
 514
 515         if (!bio) {
 516                 BUG_ON(operation != WRITE_BARRIER);
 517                 bio = bio_alloc(GFP_KERNEL, 0);
 518                 if (unlikely(bio == NULL))
 519                         goto fail_put_bio;
 520
 521                 bio->bi_bdev    = preq.bdev;
 522                 bio->bi_private = pending_req;
 523                 bio->bi_end_io  = end_block_io_op;
 524                 bio->bi_sector  = -1;
 525         }
 526
 527         submit_bio(operation, bio);
 528
 529         if (operation == READ)
 530                 blkif->st_rd_sect += preq.nr_sects;
 531         else if (operation == WRITE || operation == WRITE_BARRIER)
 532                 blkif->st_wr_sect += preq.nr_sects;
 533
 534         return;
 535
 536  fail_flush:
 537         fast_flush_area(pending_req);
 538  fail_response:
 539         make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
 540         free_req(pending_req);
 541         msleep(1); /* back off a bit */
 542         return;
 543
 544  fail_put_bio:
 545         __end_block_io_op(pending_req, -EINVAL);
 546         if (bio)
 547                 bio_put(bio);
 548         unplug_queue(blkif);
 549         msleep(1); /* back off a bit */
 550         return;
 551 }
 552
 553
 554
 555 /******************************************************************
 556  * MISCELLANEOUS SETUP / TEARDOWN / DEBUGGING
 557  */
 558
 559
 560 static void make_response(blkif_t *blkif, u64 id,
 561                           unsigned short op, int st)
 562 {
 563         blkif_response_t  resp;
 564         unsigned long     flags;
 565         blkif_back_rings_t *blk_rings = &blkif->blk_rings;
 566         int more_to_do = 0;
 567         int notify;
 568
 569         resp.id        = id;
 570         resp.operation = op;
 571         resp.status    = st;
 572
 573         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
 574         /* Place on the response ring for the relevant domain. */
 575         switch (blkif->blk_protocol) {
 576         case BLKIF_PROTOCOL_NATIVE:
 577                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
 578                        &resp, sizeof(resp));
 579                 break;
 580         case BLKIF_PROTOCOL_X86_32:
 581                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
 582                        &resp, sizeof(resp));
 583                 break;
 584         case BLKIF_PROTOCOL_X86_64:
 585                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
 586                        &resp, sizeof(resp));
 587                 break;
 588         default:
 589                 BUG();
 590         }
 591         blk_rings->common.rsp_prod_pvt++;
 592         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
 593         if (blk_rings->common.rsp_prod_pvt == blk_rings->common.req_cons) {
 594                 /*
 595                  * Tail check for pending requests. Allows frontend to avoid
 596                  * notifications if requests are already in flight (lower
 597                  * overheads and promotes batching).
 598                  */
 599                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
 600
 601         } else if (RING_HAS_UNCONSUMED_REQUESTS(&blk_rings->common)) {
 602                 more_to_do = 1;
 603         }
 604
 605         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
 606
 607         if (more_to_do)
 608                 blkif_notify_work(blkif);
 609         if (notify)
 610                 notify_remote_via_irq(blkif->irq);
 611 }
 612
 613 static int __init blkif_init(void)
 614 {
 615         int i, mmap_pages;
 616
 617         if (!is_running_on_xen())
 618                 return -ENODEV;
 619
 620         mmap_pages = blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST;
 621
 622         pending_reqs          = kmalloc(sizeof(pending_reqs[0]) *
 623                                         blkif_reqs, GFP_KERNEL);
 624         pending_grant_handles = kmalloc(sizeof(pending_grant_handles[0]) *
 625                                         mmap_pages, GFP_KERNEL);
 626         pending_pages         = alloc_empty_pages_and_pagevec(mmap_pages);
 627
 628         if (!pending_reqs || !pending_grant_handles || !pending_pages)
 629                 goto out_of_memory;
 630
 631         for (i = 0; i < mmap_pages; i++)
 632                 pending_grant_handles[i] = BLKBACK_INVALID_HANDLE;
 633
 634         blkif_interface_init();
 635
 636         memset(pending_reqs, 0, sizeof(pending_reqs));
 637         INIT_LIST_HEAD(&pending_free);
 638
 639         for (i = 0; i < blkif_reqs; i++)
 640                 list_add_tail(&pending_reqs[i].free_list, &pending_free);
 641
 642         blkif_xenbus_init();
 643
 644         return 0;
 645
 646  out_of_memory:
 647         kfree(pending_reqs);
 648         kfree(pending_grant_handles);
 649         free_empty_pages_and_pagevec(pending_pages, mmap_pages);
 650         printk("%s: out of memory\n", __FUNCTION__);
 651         return -ENOMEM;
 652 }
 653
 654 module_init(blkif_init);
 655
 656 MODULE_LICENSE("Dual BSD/GPL");