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 #define pr_fmt(fmt) "xen-blkback: " fmt
  38
  39 #include <linux/spinlock.h>
  40 #include <linux/kthread.h>
  41 #include <linux/list.h>
  42 #include <linux/delay.h>
  43 #include <linux/freezer.h>
  44 #include <linux/bitmap.h>
  45
  46 #include <xen/events.h>
  47 #include <xen/page.h>
  48 #include <xen/xen.h>
  49 #include <asm/xen/hypervisor.h>
  50 #include <asm/xen/hypercall.h>
  51 #include <xen/balloon.h>
  52 #include <xen/grant_table.h>
  53 #include "common.h"
  54
  55 /*
  56  * Maximum number of unused free pages to keep in the internal buffer.
  57  * Setting this to a value too low will reduce memory used in each backend,
  58  * but can have a performance penalty.
  59  *
  60  * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can
  61  * be set to a lower value that might degrade performance on some intensive
  62  * IO workloads.
  63  */
  64
  65 static int xen_blkif_max_buffer_pages = 1024;
  66 module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644);
  67 MODULE_PARM_DESC(max_buffer_pages,
  68 "Maximum number of free pages to keep in each block backend buffer");
  69
  70 /*
  71  * Maximum number of grants to map persistently in blkback. For maximum
  72  * performance this should be the total numbers of grants that can be used
  73  * to fill the ring, but since this might become too high, specially with
  74  * the use of indirect descriptors, we set it to a value that provides good
  75  * performance without using too much memory.
  76  *
  77  * When the list of persistent grants is full we clean it up using a LRU
  78  * algorithm.
  79  */
  80
  81 static int xen_blkif_max_pgrants = 1056;
  82 module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644);
  83 MODULE_PARM_DESC(max_persistent_grants,
  84                  "Maximum number of grants to map persistently");
  85
  86 /*
  87  * The LRU mechanism to clean the lists of persistent grants needs to
  88  * be executed periodically. The time interval between consecutive executions
  89  * of the purge mechanism is set in ms.
  90  */
  91 #define LRU_INTERVAL 100
  92
  93 /*
  94  * When the persistent grants list is full we will remove unused grants
  95  * from the list. The percent number of grants to be removed at each LRU
  96  * execution.
  97  */
  98 #define LRU_PERCENT_CLEAN 5
  99
 100 /* Run-time switchable: /sys/module/blkback/parameters/ */
 101 static unsigned int log_stats;
 102 module_param(log_stats, int, 0644);
 103
 104 #define BLKBACK_INVALID_HANDLE (~0)
 105
 106 /* Number of free pages to remove on each call to gnttab_free_pages */
 107 #define NUM_BATCH_FREE_PAGES 10
 108
 109 static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
 110 {
 111         unsigned long flags;
 112
 113         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 114         if (list_empty(&blkif->free_pages)) {
 115                 BUG_ON(blkif->free_pages_num != 0);
 116                 spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 117                 return gnttab_alloc_pages(1, page);
 118         }
 119         BUG_ON(blkif->free_pages_num == 0);
 120         page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
 121         list_del(&page[0]->lru);
 122         blkif->free_pages_num--;
 123         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 124
 125         return 0;
 126 }
 127
 128 static inline void put_free_pages(struct xen_blkif *blkif, struct page **page,
 129                                   int num)
 130 {
 131         unsigned long flags;
 132         int i;
 133
 134         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 135         for (i = 0; i < num; i++)
 136                 list_add(&page[i]->lru, &blkif->free_pages);
 137         blkif->free_pages_num += num;
 138         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 139 }
 140
 141 static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
 142 {
 143         /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
 144         struct page *page[NUM_BATCH_FREE_PAGES];
 145         unsigned int num_pages = 0;
 146         unsigned long flags;
 147
 148         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 149         while (blkif->free_pages_num > num) {
 150                 BUG_ON(list_empty(&blkif->free_pages));
 151                 page[num_pages] = list_first_entry(&blkif->free_pages,
 152                                                    struct page, lru);
 153                 list_del(&page[num_pages]->lru);
 154                 blkif->free_pages_num--;
 155                 if (++num_pages == NUM_BATCH_FREE_PAGES) {
 156                         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 157                         gnttab_free_pages(num_pages, page);
 158                         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 159                         num_pages = 0;
 160                 }
 161         }
 162         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 163         if (num_pages != 0)
 164                 gnttab_free_pages(num_pages, page);
 165 }
 166
 167 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 168
 169 static int do_block_io_op(struct xen_blkif *blkif);
 170 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 171                                 struct blkif_request *req,
 172                                 struct pending_req *pending_req);
 173 static void make_response(struct xen_blkif *blkif, u64 id,
 174                           unsigned short op, int st);
 175
 176 #define foreach_grant_safe(pos, n, rbtree, node) \
 177         for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
 178              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 179              &(pos)->node != NULL; \
 180              (pos) = container_of(n, typeof(*(pos)), node), \
 181              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
 182
 183
 184 /*
 185  * We don't need locking around the persistent grant helpers
 186  * because blkback uses a single-thread for each backed, so we
 187  * can be sure that this functions will never be called recursively.
 188  *
 189  * The only exception to that is put_persistent_grant, that can be called
 190  * from interrupt context (by xen_blkbk_unmap), so we have to use atomic
 191  * bit operations to modify the flags of a persistent grant and to count
 192  * the number of used grants.
 193  */
 194 static int add_persistent_gnt(struct xen_blkif *blkif,
 195                                struct persistent_gnt *persistent_gnt)
 196 {
 197         struct rb_node **new = NULL, *parent = NULL;
 198         struct persistent_gnt *this;
 199
 200         if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
 201                 if (!blkif->vbd.overflow_max_grants)
 202                         blkif->vbd.overflow_max_grants = 1;
 203                 return -EBUSY;
 204         }
 205         /* Figure out where to put new node */
 206         new = &blkif->persistent_gnts.rb_node;
 207         while (*new) {
 208                 this = container_of(*new, struct persistent_gnt, node);
 209
 210                 parent = *new;
 211                 if (persistent_gnt->gnt < this->gnt)
 212                         new = &((*new)->rb_left);
 213                 else if (persistent_gnt->gnt > this->gnt)
 214                         new = &((*new)->rb_right);
 215                 else {
 216                         pr_alert_ratelimited("trying to add a gref that's already in the tree\n");
 217                         return -EINVAL;
 218                 }
 219         }
 220
 221         bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE);
 222         set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 223         /* Add new node and rebalance tree. */
 224         rb_link_node(&(persistent_gnt->node), parent, new);
 225         rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts);
 226         blkif->persistent_gnt_c++;
 227         atomic_inc(&blkif->persistent_gnt_in_use);
 228         return 0;
 229 }
 230
 231 static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif,
 232                                                  grant_ref_t gref)
 233 {
 234         struct persistent_gnt *data;
 235         struct rb_node *node = NULL;
 236
 237         node = blkif->persistent_gnts.rb_node;
 238         while (node) {
 239                 data = container_of(node, struct persistent_gnt, node);
 240
 241                 if (gref < data->gnt)
 242                         node = node->rb_left;
 243                 else if (gref > data->gnt)
 244                         node = node->rb_right;
 245                 else {
 246                         if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) {
 247                                 pr_alert_ratelimited("requesting a grant already in use\n");
 248                                 return NULL;
 249                         }
 250                         set_bit(PERSISTENT_GNT_ACTIVE, data->flags);
 251                         atomic_inc(&blkif->persistent_gnt_in_use);
 252                         return data;
 253                 }
 254         }
 255         return NULL;
 256 }
 257
 258 static void put_persistent_gnt(struct xen_blkif *blkif,
 259                                struct persistent_gnt *persistent_gnt)
 260 {
 261         if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 262                 pr_alert_ratelimited("freeing a grant already unused\n");
 263         set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 264         clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 265         atomic_dec(&blkif->persistent_gnt_in_use);
 266 }
 267
 268 static void free_persistent_gnts_unmap_callback(int result,
 269                                                 struct gntab_unmap_queue_data *data)
 270 {
 271         struct completion *c = data->data;
 272
 273         /* BUG_ON used to reproduce existing behaviour,
 274            but is this the best way to deal with this? */
 275         BUG_ON(result);
 276         complete(c);
 277 }
 278
 279 static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
 280                                  unsigned int num)
 281 {
 282         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 283         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 284         struct persistent_gnt *persistent_gnt;
 285         struct rb_node *n;
 286         int segs_to_unmap = 0;
 287         struct gntab_unmap_queue_data unmap_data;
 288         struct completion unmap_completion;
 289
 290         init_completion(&unmap_completion);
 291
 292         unmap_data.data = &unmap_completion;
 293         unmap_data.done = &free_persistent_gnts_unmap_callback;
 294         unmap_data.pages = pages;
 295         unmap_data.unmap_ops = unmap;
 296         unmap_data.kunmap_ops = NULL;
 297
 298         foreach_grant_safe(persistent_gnt, n, root, node) {
 299                 BUG_ON(persistent_gnt->handle ==
 300                         BLKBACK_INVALID_HANDLE);
 301                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 302                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 303                                 persistent_gnt->page)),
 304                         GNTMAP_host_map,
 305                         persistent_gnt->handle);
 306
 307                 pages[segs_to_unmap] = persistent_gnt->page;
 308
 309                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 310                         !rb_next(&persistent_gnt->node)) {
 311
 312                         unmap_data.count = segs_to_unmap;
 313                         gnttab_unmap_refs_async(&unmap_data);
 314                         wait_for_completion(&unmap_completion);
 315
 316                         put_free_pages(blkif, pages, segs_to_unmap);
 317                         segs_to_unmap = 0;
 318                 }
 319
 320                 rb_erase(&persistent_gnt->node, root);
 321                 kfree(persistent_gnt);
 322                 num--;
 323         }
 324         BUG_ON(num != 0);
 325 }
 326
 327 void xen_blkbk_unmap_purged_grants(struct work_struct *work)
 328 {
 329         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 330         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 331         struct persistent_gnt *persistent_gnt;
 332         int ret, segs_to_unmap = 0;
 333         struct xen_blkif *blkif = container_of(work, typeof(*blkif), persistent_purge_work);
 334
 335         while(!list_empty(&blkif->persistent_purge_list)) {
 336                 persistent_gnt = list_first_entry(&blkif->persistent_purge_list,
 337                                                   struct persistent_gnt,
 338                                                   remove_node);
 339                 list_del(&persistent_gnt->remove_node);
 340
 341                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 342                         vaddr(persistent_gnt->page),
 343                         GNTMAP_host_map,
 344                         persistent_gnt->handle);
 345
 346                 pages[segs_to_unmap] = persistent_gnt->page;
 347
 348                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 349                         ret = gnttab_unmap_refs(unmap, NULL, pages,
 350                                 segs_to_unmap);
 351                         BUG_ON(ret);
 352                         put_free_pages(blkif, pages, segs_to_unmap);
 353                         segs_to_unmap = 0;
 354                 }
 355                 kfree(persistent_gnt);
 356         }
 357         if (segs_to_unmap > 0) {
 358                 ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap);
 359                 BUG_ON(ret);
 360                 put_free_pages(blkif, pages, segs_to_unmap);
 361         }
 362 }
 363
 364 static void purge_persistent_gnt(struct xen_blkif *blkif)
 365 {
 366         struct persistent_gnt *persistent_gnt;
 367         struct rb_node *n;
 368         unsigned int num_clean, total;
 369         bool scan_used = false, clean_used = false;
 370         struct rb_root *root;
 371
 372         if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
 373             (blkif->persistent_gnt_c == xen_blkif_max_pgrants &&
 374             !blkif->vbd.overflow_max_grants)) {
 375                 return;
 376         }
 377
 378         if (work_pending(&blkif->persistent_purge_work)) {
 379                 pr_alert_ratelimited("Scheduled work from previous purge is still pending, cannot purge list\n");
 380                 return;
 381         }
 382
 383         num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
 384         num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
 385         num_clean = min(blkif->persistent_gnt_c, num_clean);
 386         if ((num_clean == 0) ||
 387             (num_clean > (blkif->persistent_gnt_c - atomic_read(&blkif->persistent_gnt_in_use))))
 388                 return;
 389
 390         /*
 391          * At this point, we can assure that there will be no calls
 392          * to get_persistent_grant (because we are executing this code from
 393          * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
 394          * which means that the number of currently used grants will go down,
 395          * but never up, so we will always be able to remove the requested
 396          * number of grants.
 397          */
 398
 399         total = num_clean;
 400
 401         pr_debug("Going to purge %u persistent grants\n", num_clean);
 402
 403         BUG_ON(!list_empty(&blkif->persistent_purge_list));
 404         root = &blkif->persistent_gnts;
 405 purge_list:
 406         foreach_grant_safe(persistent_gnt, n, root, node) {
 407                 BUG_ON(persistent_gnt->handle ==
 408                         BLKBACK_INVALID_HANDLE);
 409
 410                 if (clean_used) {
 411                         clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 412                         continue;
 413                 }
 414
 415                 if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 416                         continue;
 417                 if (!scan_used &&
 418                     (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags)))
 419                         continue;
 420
 421                 rb_erase(&persistent_gnt->node, root);
 422                 list_add(&persistent_gnt->remove_node,
 423                          &blkif->persistent_purge_list);
 424                 if (--num_clean == 0)
 425                         goto finished;
 426         }
 427         /*
 428          * If we get here it means we also need to start cleaning
 429          * grants that were used since last purge in order to cope
 430          * with the requested num
 431          */
 432         if (!scan_used && !clean_used) {
 433                 pr_debug("Still missing %u purged frames\n", num_clean);
 434                 scan_used = true;
 435                 goto purge_list;
 436         }
 437 finished:
 438         if (!clean_used) {
 439                 pr_debug("Finished scanning for grants to clean, removing used flag\n");
 440                 clean_used = true;
 441                 goto purge_list;
 442         }
 443
 444         blkif->persistent_gnt_c -= (total - num_clean);
 445         blkif->vbd.overflow_max_grants = 0;
 446
 447         /* We can defer this work */
 448         schedule_work(&blkif->persistent_purge_work);
 449         pr_debug("Purged %u/%u\n", (total - num_clean), total);
 450         return;
 451 }
 452
 453 /*
 454  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 455  */
 456 static struct pending_req *alloc_req(struct xen_blkif *blkif)
 457 {
 458         struct pending_req *req = NULL;
 459         unsigned long flags;
 460
 461         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 462         if (!list_empty(&blkif->pending_free)) {
 463                 req = list_entry(blkif->pending_free.next, struct pending_req,
 464                                  free_list);
 465                 list_del(&req->free_list);
 466         }
 467         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 468         return req;
 469 }
 470
 471 /*
 472  * Return the 'pending_req' structure back to the freepool. We also
 473  * wake up the thread if it was waiting for a free page.
 474  */
 475 static void free_req(struct xen_blkif *blkif, struct pending_req *req)
 476 {
 477         unsigned long flags;
 478         int was_empty;
 479
 480         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 481         was_empty = list_empty(&blkif->pending_free);
 482         list_add(&req->free_list, &blkif->pending_free);
 483         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 484         if (was_empty)
 485                 wake_up(&blkif->pending_free_wq);
 486 }
 487
 488 /*
 489  * Routines for managing virtual block devices (vbds).
 490  */
 491 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 492                              int operation)
 493 {
 494         struct xen_vbd *vbd = &blkif->vbd;
 495         int rc = -EACCES;
 496
 497         if ((operation != READ) && vbd->readonly)
 498                 goto out;
 499
 500         if (likely(req->nr_sects)) {
 501                 blkif_sector_t end = req->sector_number + req->nr_sects;
 502
 503                 if (unlikely(end < req->sector_number))
 504                         goto out;
 505                 if (unlikely(end > vbd_sz(vbd)))
 506                         goto out;
 507         }
 508
 509         req->dev  = vbd->pdevice;
 510         req->bdev = vbd->bdev;
 511         rc = 0;
 512
 513  out:
 514         return rc;
 515 }
 516
 517 static void xen_vbd_resize(struct xen_blkif *blkif)
 518 {
 519         struct xen_vbd *vbd = &blkif->vbd;
 520         struct xenbus_transaction xbt;
 521         int err;
 522         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 523         unsigned long long new_size = vbd_sz(vbd);
 524
 525         pr_info("VBD Resize: Domid: %d, Device: (%d, %d)\n",
 526                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 527         pr_info("VBD Resize: new size %llu\n", new_size);
 528         vbd->size = new_size;
 529 again:
 530         err = xenbus_transaction_start(&xbt);
 531         if (err) {
 532                 pr_warn("Error starting transaction\n");
 533                 return;
 534         }
 535         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 536                             (unsigned long long)vbd_sz(vbd));
 537         if (err) {
 538                 pr_warn("Error writing new size\n");
 539                 goto abort;
 540         }
 541         /*
 542          * Write the current state; we will use this to synchronize
 543          * the front-end. If the current state is "connected" the
 544          * front-end will get the new size information online.
 545          */
 546         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 547         if (err) {
 548                 pr_warn("Error writing the state\n");
 549                 goto abort;
 550         }
 551
 552         err = xenbus_transaction_end(xbt, 0);
 553         if (err == -EAGAIN)
 554                 goto again;
 555         if (err)
 556                 pr_warn("Error ending transaction\n");
 557         return;
 558 abort:
 559         xenbus_transaction_end(xbt, 1);
 560 }
 561
 562 /*
 563  * Notification from the guest OS.
 564  */
 565 static void blkif_notify_work(struct xen_blkif *blkif)
 566 {
 567         blkif->waiting_reqs = 1;
 568         wake_up(&blkif->wq);
 569 }
 570
 571 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 572 {
 573         blkif_notify_work(dev_id);
 574         return IRQ_HANDLED;
 575 }
 576
 577 /*
 578  * SCHEDULER FUNCTIONS
 579  */
 580
 581 static void print_stats(struct xen_blkif *blkif)
 582 {
 583         pr_info("(%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
 584                  "  |  ds %4llu | pg: %4u/%4d\n",
 585                  current->comm, blkif->st_oo_req,
 586                  blkif->st_rd_req, blkif->st_wr_req,
 587                  blkif->st_f_req, blkif->st_ds_req,
 588                  blkif->persistent_gnt_c,
 589                  xen_blkif_max_pgrants);
 590         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 591         blkif->st_rd_req = 0;
 592         blkif->st_wr_req = 0;
 593         blkif->st_oo_req = 0;
 594         blkif->st_ds_req = 0;
 595 }
 596
 597 int xen_blkif_schedule(void *arg)
 598 {
 599         struct xen_blkif *blkif = arg;
 600         struct xen_vbd *vbd = &blkif->vbd;
 601         unsigned long timeout;
 602         int ret;
 603
 604         xen_blkif_get(blkif);
 605
 606         while (!kthread_should_stop()) {
 607                 if (try_to_freeze())
 608                         continue;
 609                 if (unlikely(vbd->size != vbd_sz(vbd)))
 610                         xen_vbd_resize(blkif);
 611
 612                 timeout = msecs_to_jiffies(LRU_INTERVAL);
 613
 614                 timeout = wait_event_interruptible_timeout(
 615                         blkif->wq,
 616                         blkif->waiting_reqs || kthread_should_stop(),
 617                         timeout);
 618                 if (timeout == 0)
 619                         goto purge_gnt_list;
 620                 timeout = wait_event_interruptible_timeout(
 621                         blkif->pending_free_wq,
 622                         !list_empty(&blkif->pending_free) ||
 623                         kthread_should_stop(),
 624                         timeout);
 625                 if (timeout == 0)
 626                         goto purge_gnt_list;
 627
 628                 blkif->waiting_reqs = 0;
 629                 smp_mb(); /* clear flag *before* checking for work */
 630
 631                 ret = do_block_io_op(blkif);
 632                 if (ret > 0)
 633                         blkif->waiting_reqs = 1;
 634                 if (ret == -EACCES)
 635                         wait_event_interruptible(blkif->shutdown_wq,
 636                                                  kthread_should_stop());
 637
 638 purge_gnt_list:
 639                 if (blkif->vbd.feature_gnt_persistent &&
 640                     time_after(jiffies, blkif->next_lru)) {
 641                         purge_persistent_gnt(blkif);
 642                         blkif->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
 643                 }
 644
 645                 /* Shrink if we have more than xen_blkif_max_buffer_pages */
 646                 shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
 647
 648                 if (log_stats && time_after(jiffies, blkif->st_print))
 649                         print_stats(blkif);
 650         }
 651
 652         /* Drain pending purge work */
 653         flush_work(&blkif->persistent_purge_work);
 654
 655         if (log_stats)
 656                 print_stats(blkif);
 657
 658         blkif->xenblkd = NULL;
 659         xen_blkif_put(blkif);
 660
 661         return 0;
 662 }
 663
 664 /*
 665  * Remove persistent grants and empty the pool of free pages
 666  */
 667 void xen_blkbk_free_caches(struct xen_blkif *blkif)
 668 {
 669         /* Free all persistent grant pages */
 670         if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
 671                 free_persistent_gnts(blkif, &blkif->persistent_gnts,
 672                         blkif->persistent_gnt_c);
 673
 674         BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 675         blkif->persistent_gnt_c = 0;
 676
 677         /* Since we are shutting down remove all pages from the buffer */
 678         shrink_free_pagepool(blkif, 0 /* All */);
 679 }
 680
 681 static unsigned int xen_blkbk_unmap_prepare(
 682         struct xen_blkif *blkif,
 683         struct grant_page **pages,
 684         unsigned int num,
 685         struct gnttab_unmap_grant_ref *unmap_ops,
 686         struct page **unmap_pages)
 687 {
 688         unsigned int i, invcount = 0;
 689
 690         for (i = 0; i < num; i++) {
 691                 if (pages[i]->persistent_gnt != NULL) {
 692                         put_persistent_gnt(blkif, pages[i]->persistent_gnt);
 693                         continue;
 694                 }
 695                 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
 696                         continue;
 697                 unmap_pages[invcount] = pages[i]->page;
 698                 gnttab_set_unmap_op(&unmap_ops[invcount], vaddr(pages[i]->page),
 699                                     GNTMAP_host_map, pages[i]->handle);
 700                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
 701                 invcount++;
 702        }
 703
 704        return invcount;
 705 }
 706
 707 static void xen_blkbk_unmap_and_respond_callback(int result, struct gntab_unmap_queue_data *data)
 708 {
 709         struct pending_req* pending_req = (struct pending_req*) (data->data);
 710         struct xen_blkif *blkif = pending_req->blkif;
 711
 712         /* BUG_ON used to reproduce existing behaviour,
 713            but is this the best way to deal with this? */
 714         BUG_ON(result);
 715
 716         put_free_pages(blkif, data->pages, data->count);
 717         make_response(blkif, pending_req->id,
 718                       pending_req->operation, pending_req->status);
 719         free_req(blkif, pending_req);
 720         /*
 721          * Make sure the request is freed before releasing blkif,
 722          * or there could be a race between free_req and the
 723          * cleanup done in xen_blkif_free during shutdown.
 724          *
 725          * NB: The fact that we might try to wake up pending_free_wq
 726          * before drain_complete (in case there's a drain going on)
 727          * it's not a problem with our current implementation
 728          * because we can assure there's no thread waiting on
 729          * pending_free_wq if there's a drain going on, but it has
 730          * to be taken into account if the current model is changed.
 731          */
 732         if (atomic_dec_and_test(&blkif->inflight) && atomic_read(&blkif->drain)) {
 733                 complete(&blkif->drain_complete);
 734         }
 735         xen_blkif_put(blkif);
 736 }
 737
 738 static void xen_blkbk_unmap_and_respond(struct pending_req *req)
 739 {
 740         struct gntab_unmap_queue_data* work = &req->gnttab_unmap_data;
 741         struct xen_blkif *blkif = req->blkif;
 742         struct grant_page **pages = req->segments;
 743         unsigned int invcount;
 744
 745         invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_pages,
 746                                            req->unmap, req->unmap_pages);
 747
 748         work->data = req;
 749         work->done = xen_blkbk_unmap_and_respond_callback;
 750         work->unmap_ops = req->unmap;
 751         work->kunmap_ops = NULL;
 752         work->pages = req->unmap_pages;
 753         work->count = invcount;
 754
 755         gnttab_unmap_refs_async(&req->gnttab_unmap_data);
 756 }
 757
 758
 759 /*
 760  * Unmap the grant references.
 761  *
 762  * This could accumulate ops up to the batch size to reduce the number
 763  * of hypercalls, but since this is only used in error paths there's
 764  * no real need.
 765  */
 766 static void xen_blkbk_unmap(struct xen_blkif *blkif,
 767                             struct grant_page *pages[],
 768                             int num)
 769 {
 770         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 771         struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 772         unsigned int invcount = 0;
 773         int ret;
 774
 775         while (num) {
 776                 unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
 777
 778                 invcount = xen_blkbk_unmap_prepare(blkif, pages, batch,
 779                                                    unmap, unmap_pages);
 780                 if (invcount) {
 781                         ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
 782                         BUG_ON(ret);
 783                         put_free_pages(blkif, unmap_pages, invcount);
 784                 }
 785                 pages += batch;
 786                 num -= batch;
 787         }
 788 }
 789
 790 static int xen_blkbk_map(struct xen_blkif *blkif,
 791                          struct grant_page *pages[],
 792                          int num, bool ro)
 793 {
 794         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 795         struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 796         struct persistent_gnt *persistent_gnt = NULL;
 797         phys_addr_t addr = 0;
 798         int i, seg_idx, new_map_idx;
 799         int segs_to_map = 0;
 800         int ret = 0;
 801         int last_map = 0, map_until = 0;
 802         int use_persistent_gnts;
 803
 804         use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 805
 806         /*
 807          * Fill out preq.nr_sects with proper amount of sectors, and setup
 808          * assign map[..] with the PFN of the page in our domain with the
 809          * corresponding grant reference for each page.
 810          */
 811 again:
 812         for (i = map_until; i < num; i++) {
 813                 uint32_t flags;
 814
 815                 if (use_persistent_gnts)
 816                         persistent_gnt = get_persistent_gnt(
 817                                 blkif,
 818                                 pages[i]->gref);
 819
 820                 if (persistent_gnt) {
 821                         /*
 822                          * We are using persistent grants and
 823                          * the grant is already mapped
 824                          */
 825                         pages[i]->page = persistent_gnt->page;
 826                         pages[i]->persistent_gnt = persistent_gnt;
 827                 } else {
 828                         if (get_free_page(blkif, &pages[i]->page))
 829                                 goto out_of_memory;
 830                         addr = vaddr(pages[i]->page);
 831                         pages_to_gnt[segs_to_map] = pages[i]->page;
 832                         pages[i]->persistent_gnt = NULL;
 833                         flags = GNTMAP_host_map;
 834                         if (!use_persistent_gnts && ro)
 835                                 flags |= GNTMAP_readonly;
 836                         gnttab_set_map_op(&map[segs_to_map++], addr,
 837                                           flags, pages[i]->gref,
 838                                           blkif->domid);
 839                 }
 840                 map_until = i + 1;
 841                 if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
 842                         break;
 843         }
 844
 845         if (segs_to_map) {
 846                 ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
 847                 BUG_ON(ret);
 848         }
 849
 850         /*
 851          * Now swizzle the MFN in our domain with the MFN from the other domain
 852          * so that when we access vaddr(pending_req,i) it has the contents of
 853          * the page from the other domain.
 854          */
 855         for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
 856                 if (!pages[seg_idx]->persistent_gnt) {
 857                         /* This is a newly mapped grant */
 858                         BUG_ON(new_map_idx >= segs_to_map);
 859                         if (unlikely(map[new_map_idx].status != 0)) {
 860                                 pr_debug("invalid buffer -- could not remap it\n");
 861                                 put_free_pages(blkif, &pages[seg_idx]->page, 1);
 862                                 pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
 863                                 ret |= 1;
 864                                 goto next;
 865                         }
 866                         pages[seg_idx]->handle = map[new_map_idx].handle;
 867                 } else {
 868                         continue;
 869                 }
 870                 if (use_persistent_gnts &&
 871                     blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
 872                         /*
 873                          * We are using persistent grants, the grant is
 874                          * not mapped but we might have room for it.
 875                          */
 876                         persistent_gnt = kmalloc(sizeof(struct persistent_gnt),
 877                                                  GFP_KERNEL);
 878                         if (!persistent_gnt) {
 879                                 /*
 880                                  * If we don't have enough memory to
 881                                  * allocate the persistent_gnt struct
 882                                  * map this grant non-persistenly
 883                                  */
 884                                 goto next;
 885                         }
 886                         persistent_gnt->gnt = map[new_map_idx].ref;
 887                         persistent_gnt->handle = map[new_map_idx].handle;
 888                         persistent_gnt->page = pages[seg_idx]->page;
 889                         if (add_persistent_gnt(blkif,
 890                                                persistent_gnt)) {
 891                                 kfree(persistent_gnt);
 892                                 persistent_gnt = NULL;
 893                                 goto next;
 894                         }
 895                         pages[seg_idx]->persistent_gnt = persistent_gnt;
 896                         pr_debug("grant %u added to the tree of persistent grants, using %u/%u\n",
 897                                  persistent_gnt->gnt, blkif->persistent_gnt_c,
 898                                  xen_blkif_max_pgrants);
 899                         goto next;
 900                 }
 901                 if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
 902                         blkif->vbd.overflow_max_grants = 1;
 903                         pr_debug("domain %u, device %#x is using maximum number of persistent grants\n",
 904                                  blkif->domid, blkif->vbd.handle);
 905                 }
 906                 /*
 907                  * We could not map this grant persistently, so use it as
 908                  * a non-persistent grant.
 909                  */
 910 next:
 911                 new_map_idx++;
 912         }
 913         segs_to_map = 0;
 914         last_map = map_until;
 915         if (map_until != num)
 916                 goto again;
 917
 918         return ret;
 919
 920 out_of_memory:
 921         pr_alert("%s: out of memory\n", __func__);
 922         put_free_pages(blkif, pages_to_gnt, segs_to_map);
 923         return -ENOMEM;
 924 }
 925
 926 static int xen_blkbk_map_seg(struct pending_req *pending_req)
 927 {
 928         int rc;
 929
 930         rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
 931                            pending_req->nr_pages,
 932                            (pending_req->operation != BLKIF_OP_READ));
 933
 934         return rc;
 935 }
 936
 937 static int xen_blkbk_parse_indirect(struct blkif_request *req,
 938                                     struct pending_req *pending_req,
 939                                     struct seg_buf seg[],
 940                                     struct phys_req *preq)
 941 {
 942         struct grant_page **pages = pending_req->indirect_pages;
 943         struct xen_blkif *blkif = pending_req->blkif;
 944         int indirect_grefs, rc, n, nseg, i;
 945         struct blkif_request_segment *segments = NULL;
 946
 947         nseg = pending_req->nr_pages;
 948         indirect_grefs = INDIRECT_PAGES(nseg);
 949         BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 950
 951         for (i = 0; i < indirect_grefs; i++)
 952                 pages[i]->gref = req->u.indirect.indirect_grefs[i];
 953
 954         rc = xen_blkbk_map(blkif, pages, indirect_grefs, true);
 955         if (rc)
 956                 goto unmap;
 957
 958         for (n = 0, i = 0; n < nseg; n++) {
 959                 if ((n % SEGS_PER_INDIRECT_FRAME) == 0) {
 960                         /* Map indirect segments */
 961                         if (segments)
 962                                 kunmap_atomic(segments);
 963                         segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
 964                 }
 965                 i = n % SEGS_PER_INDIRECT_FRAME;
 966                 pending_req->segments[n]->gref = segments[i].gref;
 967                 seg[n].nsec = segments[i].last_sect -
 968                         segments[i].first_sect + 1;
 969                 seg[n].offset = (segments[i].first_sect << 9);
 970                 if ((segments[i].last_sect >= (PAGE_SIZE >> 9)) ||
 971                     (segments[i].last_sect < segments[i].first_sect)) {
 972                         rc = -EINVAL;
 973                         goto unmap;
 974                 }
 975                 preq->nr_sects += seg[n].nsec;
 976         }
 977
 978 unmap:
 979         if (segments)
 980                 kunmap_atomic(segments);
 981         xen_blkbk_unmap(blkif, pages, indirect_grefs);
 982         return rc;
 983 }
 984
 985 static int dispatch_discard_io(struct xen_blkif *blkif,
 986                                 struct blkif_request *req)
 987 {
 988         int err = 0;
 989         int status = BLKIF_RSP_OKAY;
 990         struct block_device *bdev = blkif->vbd.bdev;
 991         unsigned long secure;
 992         struct phys_req preq;
 993
 994         xen_blkif_get(blkif);
 995
 996         preq.sector_number = req->u.discard.sector_number;
 997         preq.nr_sects      = req->u.discard.nr_sectors;
 998
 999         err = xen_vbd_translate(&preq, blkif, WRITE);
1000         if (err) {
1001                 pr_warn("access denied: DISCARD [%llu->%llu] on dev=%04x\n",
1002                         preq.sector_number,
1003                         preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
1004                 goto fail_response;
1005         }
1006         blkif->st_ds_req++;
1007
1008         secure = (blkif->vbd.discard_secure &&
1009                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
1010                  BLKDEV_DISCARD_SECURE : 0;
1011
1012         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
1013                                    req->u.discard.nr_sectors,
1014                                    GFP_KERNEL, secure);
1015 fail_response:
1016         if (err == -EOPNOTSUPP) {
1017                 pr_debug("discard op failed, not supported\n");
1018                 status = BLKIF_RSP_EOPNOTSUPP;
1019         } else if (err)
1020                 status = BLKIF_RSP_ERROR;
1021
1022         make_response(blkif, req->u.discard.id, req->operation, status);
1023         xen_blkif_put(blkif);
1024         return err;
1025 }
1026
1027 static int dispatch_other_io(struct xen_blkif *blkif,
1028                              struct blkif_request *req,
1029                              struct pending_req *pending_req)
1030 {
1031         free_req(blkif, pending_req);
1032         make_response(blkif, req->u.other.id, req->operation,
1033                       BLKIF_RSP_EOPNOTSUPP);
1034         return -EIO;
1035 }
1036
1037 static void xen_blk_drain_io(struct xen_blkif *blkif)
1038 {
1039         atomic_set(&blkif->drain, 1);
1040         do {
1041                 if (atomic_read(&blkif->inflight) == 0)
1042                         break;
1043                 wait_for_completion_interruptible_timeout(
1044                                 &blkif->drain_complete, HZ);
1045
1046                 if (!atomic_read(&blkif->drain))
1047                         break;
1048         } while (!kthread_should_stop());
1049         atomic_set(&blkif->drain, 0);
1050 }
1051
1052 /*
1053  * Completion callback on the bio's. Called as bh->b_end_io()
1054  */
1055
1056 static void __end_block_io_op(struct pending_req *pending_req, int error)
1057 {
1058         /* An error fails the entire request. */
1059         if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
1060             (error == -EOPNOTSUPP)) {
1061                 pr_debug("flush diskcache op failed, not supported\n");
1062                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
1063                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1064         } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
1065                     (error == -EOPNOTSUPP)) {
1066                 pr_debug("write barrier op failed, not supported\n");
1067                 xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
1068                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1069         } else if (error) {
1070                 pr_debug("Buffer not up-to-date at end of operation,"
1071                          " error=%d\n", error);
1072                 pending_req->status = BLKIF_RSP_ERROR;
1073         }
1074
1075         /*
1076          * If all of the bio's have completed it is time to unmap
1077          * the grant references associated with 'request' and provide
1078          * the proper response on the ring.
1079          */
1080         if (atomic_dec_and_test(&pending_req->pendcnt))
1081                 xen_blkbk_unmap_and_respond(pending_req);
1082 }
1083
1084 /*
1085  * bio callback.
1086  */
1087 static void end_block_io_op(struct bio *bio, int error)
1088 {
1089         __end_block_io_op(bio->bi_private, error);
1090         bio_put(bio);
1091 }
1092
1093
1094
1095 /*
1096  * Function to copy the from the ring buffer the 'struct blkif_request'
1097  * (which has the sectors we want, number of them, grant references, etc),
1098  * and transmute  it to the block API to hand it over to the proper block disk.
1099  */
1100 static int
1101 __do_block_io_op(struct xen_blkif *blkif)
1102 {
1103         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1104         struct blkif_request req;
1105         struct pending_req *pending_req;
1106         RING_IDX rc, rp;
1107         int more_to_do = 0;
1108
1109         rc = blk_rings->common.req_cons;
1110         rp = blk_rings->common.sring->req_prod;
1111         rmb(); /* Ensure we see queued requests up to 'rp'. */
1112
1113         if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
1114                 rc = blk_rings->common.rsp_prod_pvt;
1115                 pr_warn("Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n",
1116                         rp, rc, rp - rc, blkif->vbd.pdevice);
1117                 return -EACCES;
1118         }
1119         while (rc != rp) {
1120
1121                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1122                         break;
1123
1124                 if (kthread_should_stop()) {
1125                         more_to_do = 1;
1126                         break;
1127                 }
1128
1129                 pending_req = alloc_req(blkif);
1130                 if (NULL == pending_req) {
1131                         blkif->st_oo_req++;
1132                         more_to_do = 1;
1133                         break;
1134                 }
1135
1136                 switch (blkif->blk_protocol) {
1137                 case BLKIF_PROTOCOL_NATIVE:
1138                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1139                         break;
1140                 case BLKIF_PROTOCOL_X86_32:
1141                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1142                         break;
1143                 case BLKIF_PROTOCOL_X86_64:
1144                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1145                         break;
1146                 default:
1147                         BUG();
1148                 }
1149                 blk_rings->common.req_cons = ++rc; /* before make_response() */
1150
1151                 /* Apply all sanity checks to /private copy/ of request. */
1152                 barrier();
1153
1154                 switch (req.operation) {
1155                 case BLKIF_OP_READ:
1156                 case BLKIF_OP_WRITE:
1157                 case BLKIF_OP_WRITE_BARRIER:
1158                 case BLKIF_OP_FLUSH_DISKCACHE:
1159                 case BLKIF_OP_INDIRECT:
1160                         if (dispatch_rw_block_io(blkif, &req, pending_req))
1161                                 goto done;
1162                         break;
1163                 case BLKIF_OP_DISCARD:
1164                         free_req(blkif, pending_req);
1165                         if (dispatch_discard_io(blkif, &req))
1166                                 goto done;
1167                         break;
1168                 default:
1169                         if (dispatch_other_io(blkif, &req, pending_req))
1170                                 goto done;
1171                         break;
1172                 }
1173
1174                 /* Yield point for this unbounded loop. */
1175                 cond_resched();
1176         }
1177 done:
1178         return more_to_do;
1179 }
1180
1181 static int
1182 do_block_io_op(struct xen_blkif *blkif)
1183 {
1184         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1185         int more_to_do;
1186
1187         do {
1188                 more_to_do = __do_block_io_op(blkif);
1189                 if (more_to_do)
1190                         break;
1191
1192                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1193         } while (more_to_do);
1194
1195         return more_to_do;
1196 }
1197 /*
1198  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1199  * and call the 'submit_bio' to pass it to the underlying storage.
1200  */
1201 static int dispatch_rw_block_io(struct xen_blkif *blkif,
1202                                 struct blkif_request *req,
1203                                 struct pending_req *pending_req)
1204 {
1205         struct phys_req preq;
1206         struct seg_buf *seg = pending_req->seg;
1207         unsigned int nseg;
1208         struct bio *bio = NULL;
1209         struct bio **biolist = pending_req->biolist;
1210         int i, nbio = 0;
1211         int operation;
1212         struct blk_plug plug;
1213         bool drain = false;
1214         struct grant_page **pages = pending_req->segments;
1215         unsigned short req_operation;
1216
1217         req_operation = req->operation == BLKIF_OP_INDIRECT ?
1218                         req->u.indirect.indirect_op : req->operation;
1219         if ((req->operation == BLKIF_OP_INDIRECT) &&
1220             (req_operation != BLKIF_OP_READ) &&
1221             (req_operation != BLKIF_OP_WRITE)) {
1222                 pr_debug("Invalid indirect operation (%u)\n", req_operation);
1223                 goto fail_response;
1224         }
1225
1226         switch (req_operation) {
1227         case BLKIF_OP_READ:
1228                 blkif->st_rd_req++;
1229                 operation = READ;
1230                 break;
1231         case BLKIF_OP_WRITE:
1232                 blkif->st_wr_req++;
1233                 operation = WRITE_ODIRECT;
1234                 break;
1235         case BLKIF_OP_WRITE_BARRIER:
1236                 drain = true;
1237         case BLKIF_OP_FLUSH_DISKCACHE:
1238                 blkif->st_f_req++;
1239                 operation = WRITE_FLUSH;
1240                 break;
1241         default:
1242                 operation = 0; /* make gcc happy */
1243                 goto fail_response;
1244                 break;
1245         }
1246
1247         /* Check that the number of segments is sane. */
1248         nseg = req->operation == BLKIF_OP_INDIRECT ?
1249                req->u.indirect.nr_segments : req->u.rw.nr_segments;
1250
1251         if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
1252             unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1253                      (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1254             unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1255                      (nseg > MAX_INDIRECT_SEGMENTS))) {
1256                 pr_debug("Bad number of segments in request (%d)\n", nseg);
1257                 /* Haven't submitted any bio's yet. */
1258                 goto fail_response;
1259         }
1260
1261         preq.nr_sects      = 0;
1262
1263         pending_req->blkif     = blkif;
1264         pending_req->id        = req->u.rw.id;
1265         pending_req->operation = req_operation;
1266         pending_req->status    = BLKIF_RSP_OKAY;
1267         pending_req->nr_pages  = nseg;
1268
1269         if (req->operation != BLKIF_OP_INDIRECT) {
1270                 preq.dev               = req->u.rw.handle;
1271                 preq.sector_number     = req->u.rw.sector_number;
1272                 for (i = 0; i < nseg; i++) {
1273                         pages[i]->gref = req->u.rw.seg[i].gref;
1274                         seg[i].nsec = req->u.rw.seg[i].last_sect -
1275                                 req->u.rw.seg[i].first_sect + 1;
1276                         seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1277                         if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
1278                             (req->u.rw.seg[i].last_sect <
1279                              req->u.rw.seg[i].first_sect))
1280                                 goto fail_response;
1281                         preq.nr_sects += seg[i].nsec;
1282                 }
1283         } else {
1284                 preq.dev               = req->u.indirect.handle;
1285                 preq.sector_number     = req->u.indirect.sector_number;
1286                 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1287                         goto fail_response;
1288         }
1289
1290         if (xen_vbd_translate(&preq, blkif, operation) != 0) {
1291                 pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n",
1292                          operation == READ ? "read" : "write",
1293                          preq.sector_number,
1294                          preq.sector_number + preq.nr_sects,
1295                          blkif->vbd.pdevice);
1296                 goto fail_response;
1297         }
1298
1299         /*
1300          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1301          * is set there.
1302          */
1303         for (i = 0; i < nseg; i++) {
1304                 if (((int)preq.sector_number|(int)seg[i].nsec) &
1305                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1306                         pr_debug("Misaligned I/O request from domain %d\n",
1307                                  blkif->domid);
1308                         goto fail_response;
1309                 }
1310         }
1311
1312         /* Wait on all outstanding I/O's and once that has been completed
1313          * issue the WRITE_FLUSH.
1314          */
1315         if (drain)
1316                 xen_blk_drain_io(pending_req->blkif);
1317
1318         /*
1319          * If we have failed at this point, we need to undo the M2P override,
1320          * set gnttab_set_unmap_op on all of the grant references and perform
1321          * the hypercall to unmap the grants - that is all done in
1322          * xen_blkbk_unmap.
1323          */
1324         if (xen_blkbk_map_seg(pending_req))
1325                 goto fail_flush;
1326
1327         /*
1328          * This corresponding xen_blkif_put is done in __end_block_io_op, or
1329          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1330          */
1331         xen_blkif_get(blkif);
1332         atomic_inc(&blkif->inflight);
1333
1334         for (i = 0; i < nseg; i++) {
1335                 while ((bio == NULL) ||
1336                        (bio_add_page(bio,
1337                                      pages[i]->page,
1338                                      seg[i].nsec << 9,
1339                                      seg[i].offset) == 0)) {
1340
1341                         int nr_iovecs = min_t(int, (nseg-i), BIO_MAX_PAGES);
1342                         bio = bio_alloc(GFP_KERNEL, nr_iovecs);
1343                         if (unlikely(bio == NULL))
1344                                 goto fail_put_bio;
1345
1346                         biolist[nbio++] = bio;
1347                         bio->bi_bdev    = preq.bdev;
1348                         bio->bi_private = pending_req;
1349                         bio->bi_end_io  = end_block_io_op;
1350                         bio->bi_iter.bi_sector  = preq.sector_number;
1351                 }
1352
1353                 preq.sector_number += seg[i].nsec;
1354         }
1355
1356         /* This will be hit if the operation was a flush or discard. */
1357         if (!bio) {
1358                 BUG_ON(operation != WRITE_FLUSH);
1359
1360                 bio = bio_alloc(GFP_KERNEL, 0);
1361                 if (unlikely(bio == NULL))
1362                         goto fail_put_bio;
1363
1364                 biolist[nbio++] = bio;
1365                 bio->bi_bdev    = preq.bdev;
1366                 bio->bi_private = pending_req;
1367                 bio->bi_end_io  = end_block_io_op;
1368         }
1369
1370         atomic_set(&pending_req->pendcnt, nbio);
1371         blk_start_plug(&plug);
1372
1373         for (i = 0; i < nbio; i++)
1374                 submit_bio(operation, biolist[i]);
1375
1376         /* Let the I/Os go.. */
1377         blk_finish_plug(&plug);
1378
1379         if (operation == READ)
1380                 blkif->st_rd_sect += preq.nr_sects;
1381         else if (operation & WRITE)
1382                 blkif->st_wr_sect += preq.nr_sects;
1383
1384         return 0;
1385
1386  fail_flush:
1387         xen_blkbk_unmap(blkif, pending_req->segments,
1388                         pending_req->nr_pages);
1389  fail_response:
1390         /* Haven't submitted any bio's yet. */
1391         make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1392         free_req(blkif, pending_req);
1393         msleep(1); /* back off a bit */
1394         return -EIO;
1395
1396  fail_put_bio:
1397         for (i = 0; i < nbio; i++)
1398                 bio_put(biolist[i]);
1399         atomic_set(&pending_req->pendcnt, 1);
1400         __end_block_io_op(pending_req, -EINVAL);
1401         msleep(1); /* back off a bit */
1402         return -EIO;
1403 }
1404
1405
1406
1407 /*
1408  * Put a response on the ring on how the operation fared.
1409  */
1410 static void make_response(struct xen_blkif *blkif, u64 id,
1411                           unsigned short op, int st)
1412 {
1413         struct blkif_response  resp;
1414         unsigned long     flags;
1415         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1416         int notify;
1417
1418         resp.id        = id;
1419         resp.operation = op;
1420         resp.status    = st;
1421
1422         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
1423         /* Place on the response ring for the relevant domain. */
1424         switch (blkif->blk_protocol) {
1425         case BLKIF_PROTOCOL_NATIVE:
1426                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
1427                        &resp, sizeof(resp));
1428                 break;
1429         case BLKIF_PROTOCOL_X86_32:
1430                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
1431                        &resp, sizeof(resp));
1432                 break;
1433         case BLKIF_PROTOCOL_X86_64:
1434                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
1435                        &resp, sizeof(resp));
1436                 break;
1437         default:
1438                 BUG();
1439         }
1440         blk_rings->common.rsp_prod_pvt++;
1441         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1442         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
1443         if (notify)
1444                 notify_remote_via_irq(blkif->irq);
1445 }
1446
1447 static int __init xen_blkif_init(void)
1448 {
1449         int rc = 0;
1450
1451         if (!xen_domain())
1452                 return -ENODEV;
1453
1454         rc = xen_blkif_interface_init();
1455         if (rc)
1456                 goto failed_init;
1457
1458         rc = xen_blkif_xenbus_init();
1459         if (rc)
1460                 goto failed_init;
1461
1462  failed_init:
1463         return rc;
1464 }
1465
1466 module_init(xen_blkif_init);
1467
1468 MODULE_LICENSE("Dual BSD/GPL");
1469 MODULE_ALIAS("xen-backend:vbd");