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