drivers/block/xen-blkback/blkback.c

   1 /******************************************************************************
   2  *
   3  * Back-end of the driver for virtual block devices. This portion of the
   4  * driver exports a 'unified' block-device interface that can be accessed
   5  * by any operating system that implements a compatible front end. A
   6  * reference front-end implementation can be found in:
   7  *  drivers/block/xen-blkfront.c
   8  *
   9  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
  10  * Copyright (c) 2005, Christopher Clark
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License version 2
  14  * as published by the Free Software Foundation; or, when distributed
  15  * separately from the Linux kernel or incorporated into other
  16  * software packages, subject to the following license:
  17  *
  18  * Permission is hereby granted, free of charge, to any person obtaining a copy
  19  * of this source file (the "Software"), to deal in the Software without
  20  * restriction, including without limitation the rights to use, copy, modify,
  21  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  22  * and to permit persons to whom the Software is furnished to do so, subject to
  23  * the following conditions:
  24  *
  25  * The above copyright notice and this permission notice shall be included in
  26  * all copies or substantial portions of the Software.
  27  *
  28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  29  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  30  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  31  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  32  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  33  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  34  * IN THE SOFTWARE.
  35  */
  36
  37 #include <linux/spinlock.h>
  38 #include <linux/kthread.h>
  39 #include <linux/list.h>
  40 #include <linux/delay.h>
  41 #include <linux/freezer.h>
  42 #include <linux/bitmap.h>
  43
  44 #include <xen/events.h>
  45 #include <xen/page.h>
  46 #include <xen/xen.h>
  47 #include <asm/xen/hypervisor.h>
  48 #include <asm/xen/hypercall.h>
  49 #include <xen/balloon.h>
  50 #include "common.h"
  51
  52 /*
  53  * Maximum number of unused free pages to keep in the internal buffer.
  54  * Setting this to a value too low will reduce memory used in each backend,
  55  * but can have a performance penalty.
  56  *
  57  * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can
  58  * be set to a lower value that might degrade performance on some intensive
  59  * IO workloads.
  60  */
  61
  62 static int xen_blkif_max_buffer_pages = 1024;
  63 module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644);
  64 MODULE_PARM_DESC(max_buffer_pages,
  65 "Maximum number of free pages to keep in each block backend buffer");
  66
  67 /*
  68  * Maximum number of grants to map persistently in blkback. For maximum
  69  * performance this should be the total numbers of grants that can be used
  70  * to fill the ring, but since this might become too high, specially with
  71  * the use of indirect descriptors, we set it to a value that provides good
  72  * performance without using too much memory.
  73  *
  74  * When the list of persistent grants is full we clean it up using a LRU
  75  * algorithm.
  76  */
  77
  78 static int xen_blkif_max_pgrants = 1056;
  79 module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644);
  80 MODULE_PARM_DESC(max_persistent_grants,
  81                  "Maximum number of grants to map persistently");
  82
  83 /*
  84  * The LRU mechanism to clean the lists of persistent grants needs to
  85  * be executed periodically. The time interval between consecutive executions
  86  * of the purge mechanism is set in ms.
  87  */
  88 #define LRU_INTERVAL 100
  89
  90 /*
  91  * When the persistent grants list is full we will remove unused grants
  92  * from the list. The percent number of grants to be removed at each LRU
  93  * execution.
  94  */
  95 #define LRU_PERCENT_CLEAN 5
  96
  97 /* Run-time switchable: /sys/module/blkback/parameters/ */
  98 static unsigned int log_stats;
  99 module_param(log_stats, int, 0644);
 100
 101 #define BLKBACK_INVALID_HANDLE (~0)
 102
 103 /* Number of free pages to remove on each call to free_xenballooned_pages */
 104 #define NUM_BATCH_FREE_PAGES 10
 105
 106 static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
 107 {
 108         unsigned long flags;
 109
 110         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 111         if (list_empty(&blkif->free_pages)) {
 112                 BUG_ON(blkif->free_pages_num != 0);
 113                 spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 114                 return alloc_xenballooned_pages(1, page, false);
 115         }
 116         BUG_ON(blkif->free_pages_num == 0);
 117         page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
 118         list_del(&page[0]->lru);
 119         blkif->free_pages_num--;
 120         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 121
 122         return 0;
 123 }
 124
 125 static inline void put_free_pages(struct xen_blkif *blkif, struct page **page,
 126                                   int num)
 127 {
 128         unsigned long flags;
 129         int i;
 130
 131         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 132         for (i = 0; i < num; i++)
 133                 list_add(&page[i]->lru, &blkif->free_pages);
 134         blkif->free_pages_num += num;
 135         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 136 }
 137
 138 static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
 139 {
 140         /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
 141         struct page *page[NUM_BATCH_FREE_PAGES];
 142         unsigned int num_pages = 0;
 143         unsigned long flags;
 144
 145         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 146         while (blkif->free_pages_num > num) {
 147                 BUG_ON(list_empty(&blkif->free_pages));
 148                 page[num_pages] = list_first_entry(&blkif->free_pages,
 149                                                    struct page, lru);
 150                 list_del(&page[num_pages]->lru);
 151                 blkif->free_pages_num--;
 152                 if (++num_pages == NUM_BATCH_FREE_PAGES) {
 153                         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 154                         free_xenballooned_pages(num_pages, page);
 155                         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 156                         num_pages = 0;
 157                 }
 158         }
 159         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 160         if (num_pages != 0)
 161                 free_xenballooned_pages(num_pages, page);
 162 }
 163
 164 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 165
 166 static int do_block_io_op(struct xen_blkif *blkif);
 167 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 168                                 struct blkif_request *req,
 169                                 struct pending_req *pending_req);
 170 static void make_response(struct xen_blkif *blkif, u64 id,
 171                           unsigned short op, int st);
 172
 173 #define foreach_grant_safe(pos, n, rbtree, node) \
 174         for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
 175              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 176              &(pos)->node != NULL; \
 177              (pos) = container_of(n, typeof(*(pos)), node), \
 178              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
 179
 180
 181 /*
 182  * We don't need locking around the persistent grant helpers
 183  * because blkback uses a single-thread for each backed, so we
 184  * can be sure that this functions will never be called recursively.
 185  *
 186  * The only exception to that is put_persistent_grant, that can be called
 187  * from interrupt context (by xen_blkbk_unmap), so we have to use atomic
 188  * bit operations to modify the flags of a persistent grant and to count
 189  * the number of used grants.
 190  */
 191 static int add_persistent_gnt(struct xen_blkif *blkif,
 192                                struct persistent_gnt *persistent_gnt)
 193 {
 194         struct rb_node **new = NULL, *parent = NULL;
 195         struct persistent_gnt *this;
 196
 197         if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
 198                 if (!blkif->vbd.overflow_max_grants)
 199                         blkif->vbd.overflow_max_grants = 1;
 200                 return -EBUSY;
 201         }
 202         /* Figure out where to put new node */
 203         new = &blkif->persistent_gnts.rb_node;
 204         while (*new) {
 205                 this = container_of(*new, struct persistent_gnt, node);
 206
 207                 parent = *new;
 208                 if (persistent_gnt->gnt < this->gnt)
 209                         new = &((*new)->rb_left);
 210                 else if (persistent_gnt->gnt > this->gnt)
 211                         new = &((*new)->rb_right);
 212                 else {
 213                         pr_alert_ratelimited(DRV_PFX " trying to add a gref that's already in the tree\n");
 214                         return -EINVAL;
 215                 }
 216         }
 217
 218         bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE);
 219         set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 220         /* Add new node and rebalance tree. */
 221         rb_link_node(&(persistent_gnt->node), parent, new);
 222         rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts);
 223         blkif->persistent_gnt_c++;
 224         atomic_inc(&blkif->persistent_gnt_in_use);
 225         return 0;
 226 }
 227
 228 static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif,
 229                                                  grant_ref_t gref)
 230 {
 231         struct persistent_gnt *data;
 232         struct rb_node *node = NULL;
 233
 234         node = blkif->persistent_gnts.rb_node;
 235         while (node) {
 236                 data = container_of(node, struct persistent_gnt, node);
 237
 238                 if (gref < data->gnt)
 239                         node = node->rb_left;
 240                 else if (gref > data->gnt)
 241                         node = node->rb_right;
 242                 else {
 243                         if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) {
 244                                 pr_alert_ratelimited(DRV_PFX " requesting a grant already in use\n");
 245                                 return NULL;
 246                         }
 247                         set_bit(PERSISTENT_GNT_ACTIVE, data->flags);
 248                         atomic_inc(&blkif->persistent_gnt_in_use);
 249                         return data;
 250                 }
 251         }
 252         return NULL;
 253 }
 254
 255 static void put_persistent_gnt(struct xen_blkif *blkif,
 256                                struct persistent_gnt *persistent_gnt)
 257 {
 258         if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 259                   pr_alert_ratelimited(DRV_PFX " freeing a grant already unused");
 260         set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 261         clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 262         atomic_dec(&blkif->persistent_gnt_in_use);
 263 }
 264
 265 static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
 266                                  unsigned int num)
 267 {
 268         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 269         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 270         struct persistent_gnt *persistent_gnt;
 271         struct rb_node *n;
 272         int ret = 0;
 273         int segs_to_unmap = 0;
 274
 275         foreach_grant_safe(persistent_gnt, n, root, node) {
 276                 BUG_ON(persistent_gnt->handle ==
 277                         BLKBACK_INVALID_HANDLE);
 278                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 279                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 280                                 persistent_gnt->page)),
 281                         GNTMAP_host_map,
 282                         persistent_gnt->handle);
 283
 284                 pages[segs_to_unmap] = persistent_gnt->page;
 285
 286                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 287                         !rb_next(&persistent_gnt->node)) {
 288                         ret = gnttab_unmap_refs(unmap, NULL, pages,
 289                                 segs_to_unmap);
 290                         BUG_ON(ret);
 291                         put_free_pages(blkif, pages, segs_to_unmap);
 292                         segs_to_unmap = 0;
 293                 }
 294
 295                 rb_erase(&persistent_gnt->node, root);
 296                 kfree(persistent_gnt);
 297                 num--;
 298         }
 299         BUG_ON(num != 0);
 300 }
 301
 302 static void unmap_purged_grants(struct work_struct *work)
 303 {
 304         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 305         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 306         struct persistent_gnt *persistent_gnt;
 307         int ret, segs_to_unmap = 0;
 308         struct xen_blkif *blkif = container_of(work, typeof(*blkif), persistent_purge_work);
 309
 310         while(!list_empty(&blkif->persistent_purge_list)) {
 311                 persistent_gnt = list_first_entry(&blkif->persistent_purge_list,
 312                                                   struct persistent_gnt,
 313                                                   remove_node);
 314                 list_del(&persistent_gnt->remove_node);
 315
 316                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 317                         vaddr(persistent_gnt->page),
 318                         GNTMAP_host_map,
 319                         persistent_gnt->handle);
 320
 321                 pages[segs_to_unmap] = persistent_gnt->page;
 322
 323                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 324                         ret = gnttab_unmap_refs(unmap, NULL, pages,
 325                                 segs_to_unmap);
 326                         BUG_ON(ret);
 327                         put_free_pages(blkif, pages, segs_to_unmap);
 328                         segs_to_unmap = 0;
 329                 }
 330                 kfree(persistent_gnt);
 331         }
 332         if (segs_to_unmap > 0) {
 333                 ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap);
 334                 BUG_ON(ret);
 335                 put_free_pages(blkif, pages, segs_to_unmap);
 336         }
 337 }
 338
 339 static void purge_persistent_gnt(struct xen_blkif *blkif)
 340 {
 341         struct persistent_gnt *persistent_gnt;
 342         struct rb_node *n;
 343         unsigned int num_clean, total;
 344         bool scan_used = false;
 345         struct rb_root *root;
 346
 347         if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
 348             (blkif->persistent_gnt_c == xen_blkif_max_pgrants &&
 349             !blkif->vbd.overflow_max_grants)) {
 350                 return;
 351         }
 352
 353         if (work_pending(&blkif->persistent_purge_work)) {
 354                 pr_alert_ratelimited(DRV_PFX "Scheduled work from previous purge is still pending, cannot purge list\n");
 355                 return;
 356         }
 357
 358         num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
 359         num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
 360         num_clean = min(blkif->persistent_gnt_c, num_clean);
 361         if (num_clean >
 362             (blkif->persistent_gnt_c -
 363             atomic_read(&blkif->persistent_gnt_in_use)))
 364                 return;
 365
 366         /*
 367          * At this point, we can assure that there will be no calls
 368          * to get_persistent_grant (because we are executing this code from
 369          * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
 370          * which means that the number of currently used grants will go down,
 371          * but never up, so we will always be able to remove the requested
 372          * number of grants.
 373          */
 374
 375         total = num_clean;
 376
 377         pr_debug(DRV_PFX "Going to purge %u persistent grants\n", num_clean);
 378
 379         INIT_LIST_HEAD(&blkif->persistent_purge_list);
 380         root = &blkif->persistent_gnts;
 381 purge_list:
 382         foreach_grant_safe(persistent_gnt, n, root, node) {
 383                 BUG_ON(persistent_gnt->handle ==
 384                         BLKBACK_INVALID_HANDLE);
 385
 386                 if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 387                         continue;
 388                 if (!scan_used &&
 389                     (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags)))
 390                         continue;
 391
 392                 rb_erase(&persistent_gnt->node, root);
 393                 list_add(&persistent_gnt->remove_node,
 394                          &blkif->persistent_purge_list);
 395                 if (--num_clean == 0)
 396                         goto finished;
 397         }
 398         /*
 399          * If we get here it means we also need to start cleaning
 400          * grants that were used since last purge in order to cope
 401          * with the requested num
 402          */
 403         if (!scan_used) {
 404                 pr_debug(DRV_PFX "Still missing %u purged frames\n", num_clean);
 405                 scan_used = true;
 406                 goto purge_list;
 407         }
 408 finished:
 409         /* Remove the "used" flag from all the persistent grants */
 410         foreach_grant_safe(persistent_gnt, n, root, node) {
 411                 BUG_ON(persistent_gnt->handle ==
 412                         BLKBACK_INVALID_HANDLE);
 413                 clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 414         }
 415         blkif->persistent_gnt_c -= (total - num_clean);
 416         blkif->vbd.overflow_max_grants = 0;
 417
 418         /* We can defer this work */
 419         INIT_WORK(&blkif->persistent_purge_work, unmap_purged_grants);
 420         schedule_work(&blkif->persistent_purge_work);
 421         pr_debug(DRV_PFX "Purged %u/%u\n", (total - num_clean), total);
 422         return;
 423 }
 424
 425 /*
 426  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 427  */
 428 static struct pending_req *alloc_req(struct xen_blkif *blkif)
 429 {
 430         struct pending_req *req = NULL;
 431         unsigned long flags;
 432
 433         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 434         if (!list_empty(&blkif->pending_free)) {
 435                 req = list_entry(blkif->pending_free.next, struct pending_req,
 436                                  free_list);
 437                 list_del(&req->free_list);
 438         }
 439         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 440         return req;
 441 }
 442
 443 /*
 444  * Return the 'pending_req' structure back to the freepool. We also
 445  * wake up the thread if it was waiting for a free page.
 446  */
 447 static void free_req(struct xen_blkif *blkif, struct pending_req *req)
 448 {
 449         unsigned long flags;
 450         int was_empty;
 451
 452         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 453         was_empty = list_empty(&blkif->pending_free);
 454         list_add(&req->free_list, &blkif->pending_free);
 455         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 456         if (was_empty)
 457                 wake_up(&blkif->pending_free_wq);
 458 }
 459
 460 /*
 461  * Routines for managing virtual block devices (vbds).
 462  */
 463 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 464                              int operation)
 465 {
 466         struct xen_vbd *vbd = &blkif->vbd;
 467         int rc = -EACCES;
 468
 469         if ((operation != READ) && vbd->readonly)
 470                 goto out;
 471
 472         if (likely(req->nr_sects)) {
 473                 blkif_sector_t end = req->sector_number + req->nr_sects;
 474
 475                 if (unlikely(end < req->sector_number))
 476                         goto out;
 477                 if (unlikely(end > vbd_sz(vbd)))
 478                         goto out;
 479         }
 480
 481         req->dev  = vbd->pdevice;
 482         req->bdev = vbd->bdev;
 483         rc = 0;
 484
 485  out:
 486         return rc;
 487 }
 488
 489 static void xen_vbd_resize(struct xen_blkif *blkif)
 490 {
 491         struct xen_vbd *vbd = &blkif->vbd;
 492         struct xenbus_transaction xbt;
 493         int err;
 494         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 495         unsigned long long new_size = vbd_sz(vbd);
 496
 497         pr_info(DRV_PFX "VBD Resize: Domid: %d, Device: (%d, %d)\n",
 498                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 499         pr_info(DRV_PFX "VBD Resize: new size %llu\n", new_size);
 500         vbd->size = new_size;
 501 again:
 502         err = xenbus_transaction_start(&xbt);
 503         if (err) {
 504                 pr_warn(DRV_PFX "Error starting transaction");
 505                 return;
 506         }
 507         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 508                             (unsigned long long)vbd_sz(vbd));
 509         if (err) {
 510                 pr_warn(DRV_PFX "Error writing new size");
 511                 goto abort;
 512         }
 513         /*
 514          * Write the current state; we will use this to synchronize
 515          * the front-end. If the current state is "connected" the
 516          * front-end will get the new size information online.
 517          */
 518         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 519         if (err) {
 520                 pr_warn(DRV_PFX "Error writing the state");
 521                 goto abort;
 522         }
 523
 524         err = xenbus_transaction_end(xbt, 0);
 525         if (err == -EAGAIN)
 526                 goto again;
 527         if (err)
 528                 pr_warn(DRV_PFX "Error ending transaction");
 529         return;
 530 abort:
 531         xenbus_transaction_end(xbt, 1);
 532 }
 533
 534 /*
 535  * Notification from the guest OS.
 536  */
 537 static void blkif_notify_work(struct xen_blkif *blkif)
 538 {
 539         blkif->waiting_reqs = 1;
 540         wake_up(&blkif->wq);
 541 }
 542
 543 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 544 {
 545         blkif_notify_work(dev_id);
 546         return IRQ_HANDLED;
 547 }
 548
 549 /*
 550  * SCHEDULER FUNCTIONS
 551  */
 552
 553 static void print_stats(struct xen_blkif *blkif)
 554 {
 555         pr_info("xen-blkback (%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
 556                  "  |  ds %4llu | pg: %4u/%4d\n",
 557                  current->comm, blkif->st_oo_req,
 558                  blkif->st_rd_req, blkif->st_wr_req,
 559                  blkif->st_f_req, blkif->st_ds_req,
 560                  blkif->persistent_gnt_c,
 561                  xen_blkif_max_pgrants);
 562         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 563         blkif->st_rd_req = 0;
 564         blkif->st_wr_req = 0;
 565         blkif->st_oo_req = 0;
 566         blkif->st_ds_req = 0;
 567 }
 568
 569 int xen_blkif_schedule(void *arg)
 570 {
 571         struct xen_blkif *blkif = arg;
 572         struct xen_vbd *vbd = &blkif->vbd;
 573         unsigned long timeout;
 574
 575         xen_blkif_get(blkif);
 576
 577         while (!kthread_should_stop()) {
 578                 if (try_to_freeze())
 579                         continue;
 580                 if (unlikely(vbd->size != vbd_sz(vbd)))
 581                         xen_vbd_resize(blkif);
 582
 583                 timeout = msecs_to_jiffies(LRU_INTERVAL);
 584
 585                 timeout = wait_event_interruptible_timeout(
 586                         blkif->wq,
 587                         blkif->waiting_reqs || kthread_should_stop(),
 588                         timeout);
 589                 if (timeout == 0)
 590                         goto purge_gnt_list;
 591                 timeout = wait_event_interruptible_timeout(
 592                         blkif->pending_free_wq,
 593                         !list_empty(&blkif->pending_free) ||
 594                         kthread_should_stop(),
 595                         timeout);
 596                 if (timeout == 0)
 597                         goto purge_gnt_list;
 598
 599                 blkif->waiting_reqs = 0;
 600                 smp_mb(); /* clear flag *before* checking for work */
 601
 602                 if (do_block_io_op(blkif))
 603                         blkif->waiting_reqs = 1;
 604
 605 purge_gnt_list:
 606                 if (blkif->vbd.feature_gnt_persistent &&
 607                     time_after(jiffies, blkif->next_lru)) {
 608                         purge_persistent_gnt(blkif);
 609                         blkif->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
 610                 }
 611
 612                 /* Shrink if we have more than xen_blkif_max_buffer_pages */
 613                 shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
 614
 615                 if (log_stats && time_after(jiffies, blkif->st_print))
 616                         print_stats(blkif);
 617         }
 618
 619         /* Since we are shutting down remove all pages from the buffer */
 620         shrink_free_pagepool(blkif, 0 /* All */);
 621
 622         /* Free all persistent grant pages */
 623         if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
 624                 free_persistent_gnts(blkif, &blkif->persistent_gnts,
 625                         blkif->persistent_gnt_c);
 626
 627         BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 628         blkif->persistent_gnt_c = 0;
 629
 630         if (log_stats)
 631                 print_stats(blkif);
 632
 633         blkif->xenblkd = NULL;
 634         xen_blkif_put(blkif);
 635
 636         return 0;
 637 }
 638
 639 /*
 640  * Unmap the grant references, and also remove the M2P over-rides
 641  * used in the 'pending_req'.
 642  */
 643 static void xen_blkbk_unmap(struct xen_blkif *blkif,
 644                             struct grant_page *pages[],
 645                             int num)
 646 {
 647         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 648         struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 649         unsigned int i, invcount = 0;
 650         int ret;
 651
 652         for (i = 0; i < num; i++) {
 653                 if (pages[i]->persistent_gnt != NULL) {
 654                         put_persistent_gnt(blkif, pages[i]->persistent_gnt);
 655                         continue;
 656                 }
 657                 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
 658                         continue;
 659                 unmap_pages[invcount] = pages[i]->page;
 660                 gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]->page),
 661                                     GNTMAP_host_map, pages[i]->handle);
 662                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
 663                 if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 664                         ret = gnttab_unmap_refs(unmap, NULL, unmap_pages,
 665                                                 invcount);
 666                         BUG_ON(ret);
 667                         put_free_pages(blkif, unmap_pages, invcount);
 668                         invcount = 0;
 669                 }
 670         }
 671         if (invcount) {
 672                 ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
 673                 BUG_ON(ret);
 674                 put_free_pages(blkif, unmap_pages, invcount);
 675         }
 676 }
 677
 678 static int xen_blkbk_map(struct xen_blkif *blkif,
 679                          struct grant_page *pages[],
 680                          int num, bool ro)
 681 {
 682         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 683         struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 684         struct persistent_gnt *persistent_gnt = NULL;
 685         phys_addr_t addr = 0;
 686         int i, seg_idx, new_map_idx;
 687         int segs_to_map = 0;
 688         int ret = 0;
 689         int last_map = 0, map_until = 0;
 690         int use_persistent_gnts;
 691
 692         use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 693
 694         /*
 695          * Fill out preq.nr_sects with proper amount of sectors, and setup
 696          * assign map[..] with the PFN of the page in our domain with the
 697          * corresponding grant reference for each page.
 698          */
 699 again:
 700         for (i = map_until; i < num; i++) {
 701                 uint32_t flags;
 702
 703                 if (use_persistent_gnts)
 704                         persistent_gnt = get_persistent_gnt(
 705                                 blkif,
 706                                 pages[i]->gref);
 707
 708                 if (persistent_gnt) {
 709                         /*
 710                          * We are using persistent grants and
 711                          * the grant is already mapped
 712                          */
 713                         pages[i]->page = persistent_gnt->page;
 714                         pages[i]->persistent_gnt = persistent_gnt;
 715                 } else {
 716                         if (get_free_page(blkif, &pages[i]->page))
 717                                 goto out_of_memory;
 718                         addr = vaddr(pages[i]->page);
 719                         pages_to_gnt[segs_to_map] = pages[i]->page;
 720                         pages[i]->persistent_gnt = NULL;
 721                         flags = GNTMAP_host_map;
 722                         if (!use_persistent_gnts && ro)
 723                                 flags |= GNTMAP_readonly;
 724                         gnttab_set_map_op(&map[segs_to_map++], addr,
 725                                           flags, pages[i]->gref,
 726                                           blkif->domid);
 727                 }
 728                 map_until = i + 1;
 729                 if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
 730                         break;
 731         }
 732
 733         if (segs_to_map) {
 734                 ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
 735                 BUG_ON(ret);
 736         }
 737
 738         /*
 739          * Now swizzle the MFN in our domain with the MFN from the other domain
 740          * so that when we access vaddr(pending_req,i) it has the contents of
 741          * the page from the other domain.
 742          */
 743         for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
 744                 if (!pages[seg_idx]->persistent_gnt) {
 745                         /* This is a newly mapped grant */
 746                         BUG_ON(new_map_idx >= segs_to_map);
 747                         if (unlikely(map[new_map_idx].status != 0)) {
 748                                 pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
 749                                 pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
 750                                 ret |= 1;
 751                                 goto next;
 752                         }
 753                         pages[seg_idx]->handle = map[new_map_idx].handle;
 754                 } else {
 755                         continue;
 756                 }
 757                 if (use_persistent_gnts &&
 758                     blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
 759                         /*
 760                          * We are using persistent grants, the grant is
 761                          * not mapped but we might have room for it.
 762                          */
 763                         persistent_gnt = kmalloc(sizeof(struct persistent_gnt),
 764                                                  GFP_KERNEL);
 765                         if (!persistent_gnt) {
 766                                 /*
 767                                  * If we don't have enough memory to
 768                                  * allocate the persistent_gnt struct
 769                                  * map this grant non-persistenly
 770                                  */
 771                                 goto next;
 772                         }
 773                         persistent_gnt->gnt = map[new_map_idx].ref;
 774                         persistent_gnt->handle = map[new_map_idx].handle;
 775                         persistent_gnt->page = pages[seg_idx]->page;
 776                         if (add_persistent_gnt(blkif,
 777                                                persistent_gnt)) {
 778                                 kfree(persistent_gnt);
 779                                 persistent_gnt = NULL;
 780                                 goto next;
 781                         }
 782                         pages[seg_idx]->persistent_gnt = persistent_gnt;
 783                         pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n",
 784                                  persistent_gnt->gnt, blkif->persistent_gnt_c,
 785                                  xen_blkif_max_pgrants);
 786                         goto next;
 787                 }
 788                 if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
 789                         blkif->vbd.overflow_max_grants = 1;
 790                         pr_debug(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n",
 791                                  blkif->domid, blkif->vbd.handle);
 792                 }
 793                 /*
 794                  * We could not map this grant persistently, so use it as
 795                  * a non-persistent grant.
 796                  */
 797 next:
 798                 new_map_idx++;
 799         }
 800         segs_to_map = 0;
 801         last_map = map_until;
 802         if (map_until != num)
 803                 goto again;
 804
 805         return ret;
 806
 807 out_of_memory:
 808         pr_alert(DRV_PFX "%s: out of memory\n", __func__);
 809         put_free_pages(blkif, pages_to_gnt, segs_to_map);
 810         return -ENOMEM;
 811 }
 812
 813 static int xen_blkbk_map_seg(struct pending_req *pending_req)
 814 {
 815         int rc;
 816
 817         rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
 818                            pending_req->nr_pages,
 819                            (pending_req->operation != BLKIF_OP_READ));
 820
 821         return rc;
 822 }
 823
 824 static int xen_blkbk_parse_indirect(struct blkif_request *req,
 825                                     struct pending_req *pending_req,
 826                                     struct seg_buf seg[],
 827                                     struct phys_req *preq)
 828 {
 829         struct grant_page **pages = pending_req->indirect_pages;
 830         struct xen_blkif *blkif = pending_req->blkif;
 831         int indirect_grefs, rc, n, nseg, i;
 832         struct blkif_request_segment_aligned *segments = NULL;
 833
 834         nseg = pending_req->nr_pages;
 835         indirect_grefs = INDIRECT_PAGES(nseg);
 836         BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 837
 838         for (i = 0; i < indirect_grefs; i++)
 839                 pages[i]->gref = req->u.indirect.indirect_grefs[i];
 840
 841         rc = xen_blkbk_map(blkif, pages, indirect_grefs, true);
 842         if (rc)
 843                 goto unmap;
 844
 845         for (n = 0, i = 0; n < nseg; n++) {
 846                 if ((n % SEGS_PER_INDIRECT_FRAME) == 0) {
 847                         /* Map indirect segments */
 848                         if (segments)
 849                                 kunmap_atomic(segments);
 850                         segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
 851                 }
 852                 i = n % SEGS_PER_INDIRECT_FRAME;
 853                 pending_req->segments[n]->gref = segments[i].gref;
 854                 seg[n].nsec = segments[i].last_sect -
 855                         segments[i].first_sect + 1;
 856                 seg[n].offset = (segments[i].first_sect << 9);
 857                 if ((segments[i].last_sect >= (PAGE_SIZE >> 9)) ||
 858                     (segments[i].last_sect < segments[i].first_sect)) {
 859                         rc = -EINVAL;
 860                         goto unmap;
 861                 }
 862                 preq->nr_sects += seg[n].nsec;
 863         }
 864
 865 unmap:
 866         if (segments)
 867                 kunmap_atomic(segments);
 868         xen_blkbk_unmap(blkif, pages, indirect_grefs);
 869         return rc;
 870 }
 871
 872 static int dispatch_discard_io(struct xen_blkif *blkif,
 873                                 struct blkif_request *req)
 874 {
 875         int err = 0;
 876         int status = BLKIF_RSP_OKAY;
 877         struct block_device *bdev = blkif->vbd.bdev;
 878         unsigned long secure;
 879
 880         blkif->st_ds_req++;
 881
 882         xen_blkif_get(blkif);
 883         secure = (blkif->vbd.discard_secure &&
 884                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
 885                  BLKDEV_DISCARD_SECURE : 0;
 886
 887         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
 888                                    req->u.discard.nr_sectors,
 889                                    GFP_KERNEL, secure);
 890
 891         if (err == -EOPNOTSUPP) {
 892                 pr_debug(DRV_PFX "discard op failed, not supported\n");
 893                 status = BLKIF_RSP_EOPNOTSUPP;
 894         } else if (err)
 895                 status = BLKIF_RSP_ERROR;
 896
 897         make_response(blkif, req->u.discard.id, req->operation, status);
 898         xen_blkif_put(blkif);
 899         return err;
 900 }
 901
 902 static int dispatch_other_io(struct xen_blkif *blkif,
 903                              struct blkif_request *req,
 904                              struct pending_req *pending_req)
 905 {
 906         free_req(blkif, pending_req);
 907         make_response(blkif, req->u.other.id, req->operation,
 908                       BLKIF_RSP_EOPNOTSUPP);
 909         return -EIO;
 910 }
 911
 912 static void xen_blk_drain_io(struct xen_blkif *blkif)
 913 {
 914         atomic_set(&blkif->drain, 1);
 915         do {
 916                 /* The initial value is one, and one refcnt taken at the
 917                  * start of the xen_blkif_schedule thread. */
 918                 if (atomic_read(&blkif->refcnt) <= 2)
 919                         break;
 920                 wait_for_completion_interruptible_timeout(
 921                                 &blkif->drain_complete, HZ);
 922
 923                 if (!atomic_read(&blkif->drain))
 924                         break;
 925         } while (!kthread_should_stop());
 926         atomic_set(&blkif->drain, 0);
 927 }
 928
 929 /*
 930  * Completion callback on the bio's. Called as bh->b_end_io()
 931  */
 932
 933 static void __end_block_io_op(struct pending_req *pending_req, int error)
 934 {
 935         /* An error fails the entire request. */
 936         if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
 937             (error == -EOPNOTSUPP)) {
 938                 pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
 939                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
 940                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 941         } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
 942                     (error == -EOPNOTSUPP)) {
 943                 pr_debug(DRV_PFX "write barrier op failed, not supported\n");
 944                 xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
 945                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 946         } else if (error) {
 947                 pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
 948                          " error=%d\n", error);
 949                 pending_req->status = BLKIF_RSP_ERROR;
 950         }
 951
 952         /*
 953          * If all of the bio's have completed it is time to unmap
 954          * the grant references associated with 'request' and provide
 955          * the proper response on the ring.
 956          */
 957         if (atomic_dec_and_test(&pending_req->pendcnt)) {
 958                 xen_blkbk_unmap(pending_req->blkif,
 959                                 pending_req->segments,
 960                                 pending_req->nr_pages);
 961                 make_response(pending_req->blkif, pending_req->id,
 962                               pending_req->operation, pending_req->status);
 963                 xen_blkif_put(pending_req->blkif);
 964                 if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
 965                         if (atomic_read(&pending_req->blkif->drain))
 966                                 complete(&pending_req->blkif->drain_complete);
 967                 }
 968                 free_req(pending_req->blkif, pending_req);
 969         }
 970 }
 971
 972 /*
 973  * bio callback.
 974  */
 975 static void end_block_io_op(struct bio *bio, int error)
 976 {
 977         __end_block_io_op(bio->bi_private, error);
 978         bio_put(bio);
 979 }
 980
 981
 982
 983 /*
 984  * Function to copy the from the ring buffer the 'struct blkif_request'
 985  * (which has the sectors we want, number of them, grant references, etc),
 986  * and transmute  it to the block API to hand it over to the proper block disk.
 987  */
 988 static int
 989 __do_block_io_op(struct xen_blkif *blkif)
 990 {
 991         union blkif_back_rings *blk_rings = &blkif->blk_rings;
 992         struct blkif_request req;
 993         struct pending_req *pending_req;
 994         RING_IDX rc, rp;
 995         int more_to_do = 0;
 996
 997         rc = blk_rings->common.req_cons;
 998         rp = blk_rings->common.sring->req_prod;
 999         rmb(); /* Ensure we see queued requests up to 'rp'. */
1000
1001         while (rc != rp) {
1002
1003                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1004                         break;
1005
1006                 if (kthread_should_stop()) {
1007                         more_to_do = 1;
1008                         break;
1009                 }
1010
1011                 pending_req = alloc_req(blkif);
1012                 if (NULL == pending_req) {
1013                         blkif->st_oo_req++;
1014                         more_to_do = 1;
1015                         break;
1016                 }
1017
1018                 switch (blkif->blk_protocol) {
1019                 case BLKIF_PROTOCOL_NATIVE:
1020                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1021                         break;
1022                 case BLKIF_PROTOCOL_X86_32:
1023                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1024                         break;
1025                 case BLKIF_PROTOCOL_X86_64:
1026                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1027                         break;
1028                 default:
1029                         BUG();
1030                 }
1031                 blk_rings->common.req_cons = ++rc; /* before make_response() */
1032
1033                 /* Apply all sanity checks to /private copy/ of request. */
1034                 barrier();
1035
1036                 switch (req.operation) {
1037                 case BLKIF_OP_READ:
1038                 case BLKIF_OP_WRITE:
1039                 case BLKIF_OP_WRITE_BARRIER:
1040                 case BLKIF_OP_FLUSH_DISKCACHE:
1041                 case BLKIF_OP_INDIRECT:
1042                         if (dispatch_rw_block_io(blkif, &req, pending_req))
1043                                 goto done;
1044                         break;
1045                 case BLKIF_OP_DISCARD:
1046                         free_req(blkif, pending_req);
1047                         if (dispatch_discard_io(blkif, &req))
1048                                 goto done;
1049                         break;
1050                 default:
1051                         if (dispatch_other_io(blkif, &req, pending_req))
1052                                 goto done;
1053                         break;
1054                 }
1055
1056                 /* Yield point for this unbounded loop. */
1057                 cond_resched();
1058         }
1059 done:
1060         return more_to_do;
1061 }
1062
1063 static int
1064 do_block_io_op(struct xen_blkif *blkif)
1065 {
1066         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1067         int more_to_do;
1068
1069         do {
1070                 more_to_do = __do_block_io_op(blkif);
1071                 if (more_to_do)
1072                         break;
1073
1074                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1075         } while (more_to_do);
1076
1077         return more_to_do;
1078 }
1079 /*
1080  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1081  * and call the 'submit_bio' to pass it to the underlying storage.
1082  */
1083 static int dispatch_rw_block_io(struct xen_blkif *blkif,
1084                                 struct blkif_request *req,
1085                                 struct pending_req *pending_req)
1086 {
1087         struct phys_req preq;
1088         struct seg_buf *seg = pending_req->seg;
1089         unsigned int nseg;
1090         struct bio *bio = NULL;
1091         struct bio **biolist = pending_req->biolist;
1092         int i, nbio = 0;
1093         int operation;
1094         struct blk_plug plug;
1095         bool drain = false;
1096         struct grant_page **pages = pending_req->segments;
1097         unsigned short req_operation;
1098
1099         req_operation = req->operation == BLKIF_OP_INDIRECT ?
1100                         req->u.indirect.indirect_op : req->operation;
1101         if ((req->operation == BLKIF_OP_INDIRECT) &&
1102             (req_operation != BLKIF_OP_READ) &&
1103             (req_operation != BLKIF_OP_WRITE)) {
1104                 pr_debug(DRV_PFX "Invalid indirect operation (%u)\n",
1105                          req_operation);
1106                 goto fail_response;
1107         }
1108
1109         switch (req_operation) {
1110         case BLKIF_OP_READ:
1111                 blkif->st_rd_req++;
1112                 operation = READ;
1113                 break;
1114         case BLKIF_OP_WRITE:
1115                 blkif->st_wr_req++;
1116                 operation = WRITE_ODIRECT;
1117                 break;
1118         case BLKIF_OP_WRITE_BARRIER:
1119                 drain = true;
1120         case BLKIF_OP_FLUSH_DISKCACHE:
1121                 blkif->st_f_req++;
1122                 operation = WRITE_FLUSH;
1123                 break;
1124         default:
1125                 operation = 0; /* make gcc happy */
1126                 goto fail_response;
1127                 break;
1128         }
1129
1130         /* Check that the number of segments is sane. */
1131         nseg = req->operation == BLKIF_OP_INDIRECT ?
1132                req->u.indirect.nr_segments : req->u.rw.nr_segments;
1133
1134         if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
1135             unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1136                      (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1137             unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1138                      (nseg > MAX_INDIRECT_SEGMENTS))) {
1139                 pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
1140                          nseg);
1141                 /* Haven't submitted any bio's yet. */
1142                 goto fail_response;
1143         }
1144
1145         preq.nr_sects      = 0;
1146
1147         pending_req->blkif     = blkif;
1148         pending_req->id        = req->u.rw.id;
1149         pending_req->operation = req_operation;
1150         pending_req->status    = BLKIF_RSP_OKAY;
1151         pending_req->nr_pages  = nseg;
1152
1153         if (req->operation != BLKIF_OP_INDIRECT) {
1154                 preq.dev               = req->u.rw.handle;
1155                 preq.sector_number     = req->u.rw.sector_number;
1156                 for (i = 0; i < nseg; i++) {
1157                         pages[i]->gref = req->u.rw.seg[i].gref;
1158                         seg[i].nsec = req->u.rw.seg[i].last_sect -
1159                                 req->u.rw.seg[i].first_sect + 1;
1160                         seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1161                         if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
1162                             (req->u.rw.seg[i].last_sect <
1163                              req->u.rw.seg[i].first_sect))
1164                                 goto fail_response;
1165                         preq.nr_sects += seg[i].nsec;
1166                 }
1167         } else {
1168                 preq.dev               = req->u.indirect.handle;
1169                 preq.sector_number     = req->u.indirect.sector_number;
1170                 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1171                         goto fail_response;
1172         }
1173
1174         if (xen_vbd_translate(&preq, blkif, operation) != 0) {
1175                 pr_debug(DRV_PFX "access denied: %s of [%llu,%llu] on dev=%04x\n",
1176                          operation == READ ? "read" : "write",
1177                          preq.sector_number,
1178                          preq.sector_number + preq.nr_sects,
1179                          blkif->vbd.pdevice);
1180                 goto fail_response;
1181         }
1182
1183         /*
1184          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1185          * is set there.
1186          */
1187         for (i = 0; i < nseg; i++) {
1188                 if (((int)preq.sector_number|(int)seg[i].nsec) &
1189                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1190                         pr_debug(DRV_PFX "Misaligned I/O request from domain %d",
1191                                  blkif->domid);
1192                         goto fail_response;
1193                 }
1194         }
1195
1196         /* Wait on all outstanding I/O's and once that has been completed
1197          * issue the WRITE_FLUSH.
1198          */
1199         if (drain)
1200                 xen_blk_drain_io(pending_req->blkif);
1201
1202         /*
1203          * If we have failed at this point, we need to undo the M2P override,
1204          * set gnttab_set_unmap_op on all of the grant references and perform
1205          * the hypercall to unmap the grants - that is all done in
1206          * xen_blkbk_unmap.
1207          */
1208         if (xen_blkbk_map_seg(pending_req))
1209                 goto fail_flush;
1210
1211         /*
1212          * This corresponding xen_blkif_put is done in __end_block_io_op, or
1213          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1214          */
1215         xen_blkif_get(blkif);
1216
1217         for (i = 0; i < nseg; i++) {
1218                 while ((bio == NULL) ||
1219                        (bio_add_page(bio,
1220                                      pages[i]->page,
1221                                      seg[i].nsec << 9,
1222                                      seg[i].offset) == 0)) {
1223
1224                         bio = bio_alloc(GFP_KERNEL, nseg-i);
1225                         if (unlikely(bio == NULL))
1226                                 goto fail_put_bio;
1227
1228                         biolist[nbio++] = bio;
1229                         bio->bi_bdev    = preq.bdev;
1230                         bio->bi_private = pending_req;
1231                         bio->bi_end_io  = end_block_io_op;
1232                         bio->bi_sector  = preq.sector_number;
1233                 }
1234
1235                 preq.sector_number += seg[i].nsec;
1236         }
1237
1238         /* This will be hit if the operation was a flush or discard. */
1239         if (!bio) {
1240                 BUG_ON(operation != WRITE_FLUSH);
1241
1242                 bio = bio_alloc(GFP_KERNEL, 0);
1243                 if (unlikely(bio == NULL))
1244                         goto fail_put_bio;
1245
1246                 biolist[nbio++] = bio;
1247                 bio->bi_bdev    = preq.bdev;
1248                 bio->bi_private = pending_req;
1249                 bio->bi_end_io  = end_block_io_op;
1250         }
1251
1252         atomic_set(&pending_req->pendcnt, nbio);
1253         blk_start_plug(&plug);
1254
1255         for (i = 0; i < nbio; i++)
1256                 submit_bio(operation, biolist[i]);
1257
1258         /* Let the I/Os go.. */
1259         blk_finish_plug(&plug);
1260
1261         if (operation == READ)
1262                 blkif->st_rd_sect += preq.nr_sects;
1263         else if (operation & WRITE)
1264                 blkif->st_wr_sect += preq.nr_sects;
1265
1266         return 0;
1267
1268  fail_flush:
1269         xen_blkbk_unmap(blkif, pending_req->segments,
1270                         pending_req->nr_pages);
1271  fail_response:
1272         /* Haven't submitted any bio's yet. */
1273         make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1274         free_req(blkif, pending_req);
1275         msleep(1); /* back off a bit */
1276         return -EIO;
1277
1278  fail_put_bio:
1279         for (i = 0; i < nbio; i++)
1280                 bio_put(biolist[i]);
1281         atomic_set(&pending_req->pendcnt, 1);
1282         __end_block_io_op(pending_req, -EINVAL);
1283         msleep(1); /* back off a bit */
1284         return -EIO;
1285 }
1286
1287
1288
1289 /*
1290  * Put a response on the ring on how the operation fared.
1291  */
1292 static void make_response(struct xen_blkif *blkif, u64 id,
1293                           unsigned short op, int st)
1294 {
1295         struct blkif_response  resp;
1296         unsigned long     flags;
1297         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1298         int notify;
1299
1300         resp.id        = id;
1301         resp.operation = op;
1302         resp.status    = st;
1303
1304         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
1305         /* Place on the response ring for the relevant domain. */
1306         switch (blkif->blk_protocol) {
1307         case BLKIF_PROTOCOL_NATIVE:
1308                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
1309                        &resp, sizeof(resp));
1310                 break;
1311         case BLKIF_PROTOCOL_X86_32:
1312                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
1313                        &resp, sizeof(resp));
1314                 break;
1315         case BLKIF_PROTOCOL_X86_64:
1316                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
1317                        &resp, sizeof(resp));
1318                 break;
1319         default:
1320                 BUG();
1321         }
1322         blk_rings->common.rsp_prod_pvt++;
1323         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1324         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
1325         if (notify)
1326                 notify_remote_via_irq(blkif->irq);
1327 }
1328
1329 static int __init xen_blkif_init(void)
1330 {
1331         int rc = 0;
1332
1333         if (!xen_domain())
1334                 return -ENODEV;
1335
1336         rc = xen_blkif_interface_init();
1337         if (rc)
1338                 goto failed_init;
1339
1340         rc = xen_blkif_xenbus_init();
1341         if (rc)
1342                 goto failed_init;
1343
1344  failed_init:
1345         return rc;
1346 }
1347
1348 module_init(xen_blkif_init);
1349
1350 MODULE_LICENSE("Dual BSD/GPL");
1351 MODULE_ALIAS("xen-backend:vbd");