Pileus Git - ~andy/linux/blob - drivers/block/xen-blkback/blkback.c

   1 /******************************************************************************
   2  *
   3  * Back-end of the driver for virtual block devices. This portion of the
   4  * driver exports a 'unified' block-device interface that can be accessed
   5  * by any operating system that implements a compatible front end. A
   6  * reference front-end implementation can be found in:
   7  *  drivers/block/xen-blkfront.c
   8  *
   9  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
  10  * Copyright (c) 2005, Christopher Clark
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License version 2
  14  * as published by the Free Software Foundation; or, when distributed
  15  * separately from the Linux kernel or incorporated into other
  16  * software packages, subject to the following license:
  17  *
  18  * Permission is hereby granted, free of charge, to any person obtaining a copy
  19  * of this source file (the "Software"), to deal in the Software without
  20  * restriction, including without limitation the rights to use, copy, modify,
  21  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  22  * and to permit persons to whom the Software is furnished to do so, subject to
  23  * the following conditions:
  24  *
  25  * The above copyright notice and this permission notice shall be included in
  26  * all copies or substantial portions of the Software.
  27  *
  28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  29  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  30  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  31  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  32  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  33  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  34  * IN THE SOFTWARE.
  35  */
  36
  37 #include <linux/spinlock.h>
  38 #include <linux/kthread.h>
  39 #include <linux/list.h>
  40 #include <linux/delay.h>
  41 #include <linux/freezer.h>
  42 #include <linux/bitmap.h>
  43
  44 #include <xen/events.h>
  45 #include <xen/page.h>
  46 #include <xen/xen.h>
  47 #include <asm/xen/hypervisor.h>
  48 #include <asm/xen/hypercall.h>
  49 #include <xen/balloon.h>
  50 #include "common.h"
  51
  52 /*
  53  * Maximum number of unused free pages to keep in the internal buffer.
  54  * Setting this to a value too low will reduce memory used in each backend,
  55  * but can have a performance penalty.
  56  *
  57  * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can
  58  * be set to a lower value that might degrade performance on some intensive
  59  * IO workloads.
  60  */
  61
  62 static int xen_blkif_max_buffer_pages = 1024;
  63 module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644);
  64 MODULE_PARM_DESC(max_buffer_pages,
  65 "Maximum number of free pages to keep in each block backend buffer");
  66
  67 /*
  68  * Maximum number of grants to map persistently in blkback. For maximum
  69  * performance this should be the total numbers of grants that can be used
  70  * to fill the ring, but since this might become too high, specially with
  71  * the use of indirect descriptors, we set it to a value that provides good
  72  * performance without using too much memory.
  73  *
  74  * When the list of persistent grants is full we clean it up using a LRU
  75  * algorithm.
  76  */
  77
  78 static int xen_blkif_max_pgrants = 1056;
  79 module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644);
  80 MODULE_PARM_DESC(max_persistent_grants,
  81                  "Maximum number of grants to map persistently");
  82
  83 /*
  84  * The LRU mechanism to clean the lists of persistent grants needs to
  85  * be executed periodically. The time interval between consecutive executions
  86  * of the purge mechanism is set in ms.
  87  */
  88 #define LRU_INTERVAL 100
  89
  90 /*
  91  * When the persistent grants list is full we will remove unused grants
  92  * from the list. The percent number of grants to be removed at each LRU
  93  * execution.
  94  */
  95 #define LRU_PERCENT_CLEAN 5
  96
  97 /* Run-time switchable: /sys/module/blkback/parameters/ */
  98 static unsigned int log_stats;
  99 module_param(log_stats, int, 0644);
 100
 101 #define BLKBACK_INVALID_HANDLE (~0)
 102
 103 /* Number of free pages to remove on each call to free_xenballooned_pages */
 104 #define NUM_BATCH_FREE_PAGES 10
 105
 106 static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
 107 {
 108         unsigned long flags;
 109
 110         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 111         if (list_empty(&blkif->free_pages)) {
 112                 BUG_ON(blkif->free_pages_num != 0);
 113                 spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 114                 return alloc_xenballooned_pages(1, page, false);
 115         }
 116         BUG_ON(blkif->free_pages_num == 0);
 117         page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
 118         list_del(&page[0]->lru);
 119         blkif->free_pages_num--;
 120         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 121
 122         return 0;
 123 }
 124
 125 static inline void put_free_pages(struct xen_blkif *blkif, struct page **page,
 126                                   int num)
 127 {
 128         unsigned long flags;
 129         int i;
 130
 131         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 132         for (i = 0; i < num; i++)
 133                 list_add(&page[i]->lru, &blkif->free_pages);
 134         blkif->free_pages_num += num;
 135         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 136 }
 137
 138 static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
 139 {
 140         /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
 141         struct page *page[NUM_BATCH_FREE_PAGES];
 142         unsigned int num_pages = 0;
 143         unsigned long flags;
 144
 145         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 146         while (blkif->free_pages_num > num) {
 147                 BUG_ON(list_empty(&blkif->free_pages));
 148                 page[num_pages] = list_first_entry(&blkif->free_pages,
 149                                                    struct page, lru);
 150                 list_del(&page[num_pages]->lru);
 151                 blkif->free_pages_num--;
 152                 if (++num_pages == NUM_BATCH_FREE_PAGES) {
 153                         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 154                         free_xenballooned_pages(num_pages, page);
 155                         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 156                         num_pages = 0;
 157                 }
 158         }
 159         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 160         if (num_pages != 0)
 161                 free_xenballooned_pages(num_pages, page);
 162 }
 163
 164 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 165
 166 static int do_block_io_op(struct xen_blkif *blkif);
 167 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 168                                 struct blkif_request *req,
 169                                 struct pending_req *pending_req);
 170 static void make_response(struct xen_blkif *blkif, u64 id,
 171                           unsigned short op, int st);
 172
 173 #define foreach_grant_safe(pos, n, rbtree, node) \
 174         for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
 175              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 176              &(pos)->node != NULL; \
 177              (pos) = container_of(n, typeof(*(pos)), node), \
 178              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
 179
 180
 181 /*
 182  * We don't need locking around the persistent grant helpers
 183  * because blkback uses a single-thread for each backed, so we
 184  * can be sure that this functions will never be called recursively.
 185  *
 186  * The only exception to that is put_persistent_grant, that can be called
 187  * from interrupt context (by xen_blkbk_unmap), so we have to use atomic
 188  * bit operations to modify the flags of a persistent grant and to count
 189  * the number of used grants.
 190  */
 191 static int add_persistent_gnt(struct xen_blkif *blkif,
 192                                struct persistent_gnt *persistent_gnt)
 193 {
 194         struct rb_node **new = NULL, *parent = NULL;
 195         struct persistent_gnt *this;
 196
 197         if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
 198                 if (!blkif->vbd.overflow_max_grants)
 199                         blkif->vbd.overflow_max_grants = 1;
 200                 return -EBUSY;
 201         }
 202         /* Figure out where to put new node */
 203         new = &blkif->persistent_gnts.rb_node;
 204         while (*new) {
 205                 this = container_of(*new, struct persistent_gnt, node);
 206
 207                 parent = *new;
 208                 if (persistent_gnt->gnt < this->gnt)
 209                         new = &((*new)->rb_left);
 210                 else if (persistent_gnt->gnt > this->gnt)
 211                         new = &((*new)->rb_right);
 212                 else {
 213                         pr_alert_ratelimited(DRV_PFX " trying to add a gref that's already in the tree\n");
 214                         return -EINVAL;
 215                 }
 216         }
 217
 218         bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE);
 219         set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 220         /* Add new node and rebalance tree. */
 221         rb_link_node(&(persistent_gnt->node), parent, new);
 222         rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts);
 223         blkif->persistent_gnt_c++;
 224         atomic_inc(&blkif->persistent_gnt_in_use);
 225         return 0;
 226 }
 227
 228 static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif,
 229                                                  grant_ref_t gref)
 230 {
 231         struct persistent_gnt *data;
 232         struct rb_node *node = NULL;
 233
 234         node = blkif->persistent_gnts.rb_node;
 235         while (node) {
 236                 data = container_of(node, struct persistent_gnt, node);
 237
 238                 if (gref < data->gnt)
 239                         node = node->rb_left;
 240                 else if (gref > data->gnt)
 241                         node = node->rb_right;
 242                 else {
 243                         if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) {
 244                                 pr_alert_ratelimited(DRV_PFX " requesting a grant already in use\n");
 245                                 return NULL;
 246                         }
 247                         set_bit(PERSISTENT_GNT_ACTIVE, data->flags);
 248                         atomic_inc(&blkif->persistent_gnt_in_use);
 249                         return data;
 250                 }
 251         }
 252         return NULL;
 253 }
 254
 255 static void put_persistent_gnt(struct xen_blkif *blkif,
 256                                struct persistent_gnt *persistent_gnt)
 257 {
 258         if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 259                   pr_alert_ratelimited(DRV_PFX " freeing a grant already unused");
 260         set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 261         clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 262         atomic_dec(&blkif->persistent_gnt_in_use);
 263 }
 264
 265 static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
 266                                  unsigned int num)
 267 {
 268         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 269         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 270         struct persistent_gnt *persistent_gnt;
 271         struct rb_node *n;
 272         int ret = 0;
 273         int segs_to_unmap = 0;
 274
 275         foreach_grant_safe(persistent_gnt, n, root, node) {
 276                 BUG_ON(persistent_gnt->handle ==
 277                         BLKBACK_INVALID_HANDLE);
 278                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 279                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 280                                 persistent_gnt->page)),
 281                         GNTMAP_host_map,
 282                         persistent_gnt->handle);
 283
 284                 pages[segs_to_unmap] = persistent_gnt->page;
 285
 286                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 287                         !rb_next(&persistent_gnt->node)) {
 288                         ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
 289                         BUG_ON(ret);
 290                         put_free_pages(blkif, pages, segs_to_unmap);
 291                         segs_to_unmap = 0;
 292                 }
 293
 294                 rb_erase(&persistent_gnt->node, root);
 295                 kfree(persistent_gnt);
 296                 num--;
 297         }
 298         BUG_ON(num != 0);
 299 }
 300
 301 static void unmap_purged_grants(struct work_struct *work)
 302 {
 303         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 304         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 305         struct persistent_gnt *persistent_gnt;
 306         int ret, segs_to_unmap = 0;
 307         struct xen_blkif *blkif = container_of(work, typeof(*blkif), persistent_purge_work);
 308
 309         while(!list_empty(&blkif->persistent_purge_list)) {
 310                 persistent_gnt = list_first_entry(&blkif->persistent_purge_list,
 311                                                   struct persistent_gnt,
 312                                                   remove_node);
 313                 list_del(&persistent_gnt->remove_node);
 314
 315                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 316                         vaddr(persistent_gnt->page),
 317                         GNTMAP_host_map,
 318                         persistent_gnt->handle);
 319
 320                 pages[segs_to_unmap] = persistent_gnt->page;
 321
 322                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 323                         ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
 324                         BUG_ON(ret);
 325                         put_free_pages(blkif, pages, segs_to_unmap);
 326                         segs_to_unmap = 0;
 327                 }
 328                 kfree(persistent_gnt);
 329         }
 330         if (segs_to_unmap > 0) {
 331                 ret = gnttab_unmap_refs(unmap, pages, segs_to_unmap);
 332                 BUG_ON(ret);
 333                 put_free_pages(blkif, pages, segs_to_unmap);
 334         }
 335 }
 336
 337 static void purge_persistent_gnt(struct xen_blkif *blkif)
 338 {
 339         struct persistent_gnt *persistent_gnt;
 340         struct rb_node *n;
 341         unsigned int num_clean, total;
 342         bool scan_used = false, clean_used = false;
 343         struct rb_root *root;
 344
 345         if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
 346             (blkif->persistent_gnt_c == xen_blkif_max_pgrants &&
 347             !blkif->vbd.overflow_max_grants)) {
 348                 return;
 349         }
 350
 351         if (work_pending(&blkif->persistent_purge_work)) {
 352                 pr_alert_ratelimited(DRV_PFX "Scheduled work from previous purge is still pending, cannot purge list\n");
 353                 return;
 354         }
 355
 356         num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
 357         num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
 358         num_clean = min(blkif->persistent_gnt_c, num_clean);
 359         if ((num_clean == 0) ||
 360             (num_clean > (blkif->persistent_gnt_c - atomic_read(&blkif->persistent_gnt_in_use))))
 361                 return;
 362
 363         /*
 364          * At this point, we can assure that there will be no calls
 365          * to get_persistent_grant (because we are executing this code from
 366          * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
 367          * which means that the number of currently used grants will go down,
 368          * but never up, so we will always be able to remove the requested
 369          * number of grants.
 370          */
 371
 372         total = num_clean;
 373
 374         pr_debug(DRV_PFX "Going to purge %u persistent grants\n", num_clean);
 375
 376         INIT_LIST_HEAD(&blkif->persistent_purge_list);
 377         root = &blkif->persistent_gnts;
 378 purge_list:
 379         foreach_grant_safe(persistent_gnt, n, root, node) {
 380                 BUG_ON(persistent_gnt->handle ==
 381                         BLKBACK_INVALID_HANDLE);
 382
 383                 if (clean_used) {
 384                         clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 385                         continue;
 386                 }
 387
 388                 if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 389                         continue;
 390                 if (!scan_used &&
 391                     (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags)))
 392                         continue;
 393
 394                 rb_erase(&persistent_gnt->node, root);
 395                 list_add(&persistent_gnt->remove_node,
 396                          &blkif->persistent_purge_list);
 397                 if (--num_clean == 0)
 398                         goto finished;
 399         }
 400         /*
 401          * If we get here it means we also need to start cleaning
 402          * grants that were used since last purge in order to cope
 403          * with the requested num
 404          */
 405         if (!scan_used && !clean_used) {
 406                 pr_debug(DRV_PFX "Still missing %u purged frames\n", num_clean);
 407                 scan_used = true;
 408                 goto purge_list;
 409         }
 410 finished:
 411         if (!clean_used) {
 412                 pr_debug(DRV_PFX "Finished scanning for grants to clean, removing used flag\n");
 413                 clean_used = true;
 414                 goto purge_list;
 415         }
 416
 417         blkif->persistent_gnt_c -= (total - num_clean);
 418         blkif->vbd.overflow_max_grants = 0;
 419
 420         /* We can defer this work */
 421         INIT_WORK(&blkif->persistent_purge_work, unmap_purged_grants);
 422         schedule_work(&blkif->persistent_purge_work);
 423         pr_debug(DRV_PFX "Purged %u/%u\n", (total - num_clean), total);
 424         return;
 425 }
 426
 427 /*
 428  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 429  */
 430 static struct pending_req *alloc_req(struct xen_blkif *blkif)
 431 {
 432         struct pending_req *req = NULL;
 433         unsigned long flags;
 434
 435         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 436         if (!list_empty(&blkif->pending_free)) {
 437                 req = list_entry(blkif->pending_free.next, struct pending_req,
 438                                  free_list);
 439                 list_del(&req->free_list);
 440         }
 441         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 442         return req;
 443 }
 444
 445 /*
 446  * Return the 'pending_req' structure back to the freepool. We also
 447  * wake up the thread if it was waiting for a free page.
 448  */
 449 static void free_req(struct xen_blkif *blkif, struct pending_req *req)
 450 {
 451         unsigned long flags;
 452         int was_empty;
 453
 454         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 455         was_empty = list_empty(&blkif->pending_free);
 456         list_add(&req->free_list, &blkif->pending_free);
 457         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 458         if (was_empty)
 459                 wake_up(&blkif->pending_free_wq);
 460 }
 461
 462 /*
 463  * Routines for managing virtual block devices (vbds).
 464  */
 465 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 466                              int operation)
 467 {
 468         struct xen_vbd *vbd = &blkif->vbd;
 469         int rc = -EACCES;
 470
 471         if ((operation != READ) && vbd->readonly)
 472                 goto out;
 473
 474         if (likely(req->nr_sects)) {
 475                 blkif_sector_t end = req->sector_number + req->nr_sects;
 476
 477                 if (unlikely(end < req->sector_number))
 478                         goto out;
 479                 if (unlikely(end > vbd_sz(vbd)))
 480                         goto out;
 481         }
 482
 483         req->dev  = vbd->pdevice;
 484         req->bdev = vbd->bdev;
 485         rc = 0;
 486
 487  out:
 488         return rc;
 489 }
 490
 491 static void xen_vbd_resize(struct xen_blkif *blkif)
 492 {
 493         struct xen_vbd *vbd = &blkif->vbd;
 494         struct xenbus_transaction xbt;
 495         int err;
 496         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 497         unsigned long long new_size = vbd_sz(vbd);
 498
 499         pr_info(DRV_PFX "VBD Resize: Domid: %d, Device: (%d, %d)\n",
 500                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 501         pr_info(DRV_PFX "VBD Resize: new size %llu\n", new_size);
 502         vbd->size = new_size;
 503 again:
 504         err = xenbus_transaction_start(&xbt);
 505         if (err) {
 506                 pr_warn(DRV_PFX "Error starting transaction");
 507                 return;
 508         }
 509         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 510                             (unsigned long long)vbd_sz(vbd));
 511         if (err) {
 512                 pr_warn(DRV_PFX "Error writing new size");
 513                 goto abort;
 514         }
 515         /*
 516          * Write the current state; we will use this to synchronize
 517          * the front-end. If the current state is "connected" the
 518          * front-end will get the new size information online.
 519          */
 520         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 521         if (err) {
 522                 pr_warn(DRV_PFX "Error writing the state");
 523                 goto abort;
 524         }
 525
 526         err = xenbus_transaction_end(xbt, 0);
 527         if (err == -EAGAIN)
 528                 goto again;
 529         if (err)
 530                 pr_warn(DRV_PFX "Error ending transaction");
 531         return;
 532 abort:
 533         xenbus_transaction_end(xbt, 1);
 534 }
 535
 536 /*
 537  * Notification from the guest OS.
 538  */
 539 static void blkif_notify_work(struct xen_blkif *blkif)
 540 {
 541         blkif->waiting_reqs = 1;
 542         wake_up(&blkif->wq);
 543 }
 544
 545 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 546 {
 547         blkif_notify_work(dev_id);
 548         return IRQ_HANDLED;
 549 }
 550
 551 /*
 552  * SCHEDULER FUNCTIONS
 553  */
 554
 555 static void print_stats(struct xen_blkif *blkif)
 556 {
 557         pr_info("xen-blkback (%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
 558                  "  |  ds %4llu | pg: %4u/%4d\n",
 559                  current->comm, blkif->st_oo_req,
 560                  blkif->st_rd_req, blkif->st_wr_req,
 561                  blkif->st_f_req, blkif->st_ds_req,
 562                  blkif->persistent_gnt_c,
 563                  xen_blkif_max_pgrants);
 564         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 565         blkif->st_rd_req = 0;
 566         blkif->st_wr_req = 0;
 567         blkif->st_oo_req = 0;
 568         blkif->st_ds_req = 0;
 569 }
 570
 571 int xen_blkif_schedule(void *arg)
 572 {
 573         struct xen_blkif *blkif = arg;
 574         struct xen_vbd *vbd = &blkif->vbd;
 575         unsigned long timeout;
 576         int ret;
 577
 578         xen_blkif_get(blkif);
 579
 580         while (!kthread_should_stop()) {
 581                 if (try_to_freeze())
 582                         continue;
 583                 if (unlikely(vbd->size != vbd_sz(vbd)))
 584                         xen_vbd_resize(blkif);
 585
 586                 timeout = msecs_to_jiffies(LRU_INTERVAL);
 587
 588                 timeout = wait_event_interruptible_timeout(
 589                         blkif->wq,
 590                         blkif->waiting_reqs || kthread_should_stop(),
 591                         timeout);
 592                 if (timeout == 0)
 593                         goto purge_gnt_list;
 594                 timeout = wait_event_interruptible_timeout(
 595                         blkif->pending_free_wq,
 596                         !list_empty(&blkif->pending_free) ||
 597                         kthread_should_stop(),
 598                         timeout);
 599                 if (timeout == 0)
 600                         goto purge_gnt_list;
 601
 602                 blkif->waiting_reqs = 0;
 603                 smp_mb(); /* clear flag *before* checking for work */
 604
 605                 ret = do_block_io_op(blkif);
 606                 if (ret > 0)
 607                         blkif->waiting_reqs = 1;
 608                 if (ret == -EACCES)
 609                         wait_event_interruptible(blkif->shutdown_wq,
 610                                                  kthread_should_stop());
 611
 612 purge_gnt_list:
 613                 if (blkif->vbd.feature_gnt_persistent &&
 614                     time_after(jiffies, blkif->next_lru)) {
 615                         purge_persistent_gnt(blkif);
 616                         blkif->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
 617                 }
 618
 619                 /* Shrink if we have more than xen_blkif_max_buffer_pages */
 620                 shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
 621
 622                 if (log_stats && time_after(jiffies, blkif->st_print))
 623                         print_stats(blkif);
 624         }
 625
 626         /* Since we are shutting down remove all pages from the buffer */
 627         shrink_free_pagepool(blkif, 0 /* All */);
 628
 629         /* Free all persistent grant pages */
 630         if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
 631                 free_persistent_gnts(blkif, &blkif->persistent_gnts,
 632                         blkif->persistent_gnt_c);
 633
 634         BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 635         blkif->persistent_gnt_c = 0;
 636
 637         if (log_stats)
 638                 print_stats(blkif);
 639
 640         blkif->xenblkd = NULL;
 641         xen_blkif_put(blkif);
 642
 643         return 0;
 644 }
 645
 646 /*
 647  * Unmap the grant references, and also remove the M2P over-rides
 648  * used in the 'pending_req'.
 649  */
 650 static void xen_blkbk_unmap(struct xen_blkif *blkif,
 651                             struct grant_page *pages[],
 652                             int num)
 653 {
 654         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 655         struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 656         unsigned int i, invcount = 0;
 657         int ret;
 658
 659         for (i = 0; i < num; i++) {
 660                 if (pages[i]->persistent_gnt != NULL) {
 661                         put_persistent_gnt(blkif, pages[i]->persistent_gnt);
 662                         continue;
 663                 }
 664                 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
 665                         continue;
 666                 unmap_pages[invcount] = pages[i]->page;
 667                 gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[i]->page),
 668                                     GNTMAP_host_map, pages[i]->handle);
 669                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
 670                 if (++invcount == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 671                         ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);
 672                         BUG_ON(ret);
 673                         put_free_pages(blkif, unmap_pages, invcount);
 674                         invcount = 0;
 675                 }
 676         }
 677         if (invcount) {
 678                 ret = gnttab_unmap_refs(unmap, unmap_pages, invcount);
 679                 BUG_ON(ret);
 680                 put_free_pages(blkif, unmap_pages, invcount);
 681         }
 682 }
 683
 684 static int xen_blkbk_map(struct xen_blkif *blkif,
 685                          struct grant_page *pages[],
 686                          int num, bool ro)
 687 {
 688         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 689         struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 690         struct persistent_gnt *persistent_gnt = NULL;
 691         phys_addr_t addr = 0;
 692         int i, seg_idx, new_map_idx;
 693         int segs_to_map = 0;
 694         int ret = 0;
 695         int last_map = 0, map_until = 0;
 696         int use_persistent_gnts;
 697
 698         use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 699
 700         /*
 701          * Fill out preq.nr_sects with proper amount of sectors, and setup
 702          * assign map[..] with the PFN of the page in our domain with the
 703          * corresponding grant reference for each page.
 704          */
 705 again:
 706         for (i = map_until; i < num; i++) {
 707                 uint32_t flags;
 708
 709                 if (use_persistent_gnts)
 710                         persistent_gnt = get_persistent_gnt(
 711                                 blkif,
 712                                 pages[i]->gref);
 713
 714                 if (persistent_gnt) {
 715                         /*
 716                          * We are using persistent grants and
 717                          * the grant is already mapped
 718                          */
 719                         pages[i]->page = persistent_gnt->page;
 720                         pages[i]->persistent_gnt = persistent_gnt;
 721                 } else {
 722                         if (get_free_page(blkif, &pages[i]->page))
 723                                 goto out_of_memory;
 724                         addr = vaddr(pages[i]->page);
 725                         pages_to_gnt[segs_to_map] = pages[i]->page;
 726                         pages[i]->persistent_gnt = NULL;
 727                         flags = GNTMAP_host_map;
 728                         if (!use_persistent_gnts && ro)
 729                                 flags |= GNTMAP_readonly;
 730                         gnttab_set_map_op(&map[segs_to_map++], addr,
 731                                           flags, pages[i]->gref,
 732                                           blkif->domid);
 733                 }
 734                 map_until = i + 1;
 735                 if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
 736                         break;
 737         }
 738
 739         if (segs_to_map) {
 740                 ret = gnttab_map_refs(map, pages_to_gnt, segs_to_map);
 741                 BUG_ON(ret);
 742         }
 743
 744         /*
 745          * Now swizzle the MFN in our domain with the MFN from the other domain
 746          * so that when we access vaddr(pending_req,i) it has the contents of
 747          * the page from the other domain.
 748          */
 749         for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
 750                 if (!pages[seg_idx]->persistent_gnt) {
 751                         /* This is a newly mapped grant */
 752                         BUG_ON(new_map_idx >= segs_to_map);
 753                         if (unlikely(map[new_map_idx].status != 0)) {
 754                                 pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
 755                                 pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
 756                                 ret |= 1;
 757                                 goto next;
 758                         }
 759                         pages[seg_idx]->handle = map[new_map_idx].handle;
 760                 } else {
 761                         continue;
 762                 }
 763                 if (use_persistent_gnts &&
 764                     blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
 765                         /*
 766                          * We are using persistent grants, the grant is
 767                          * not mapped but we might have room for it.
 768                          */
 769                         persistent_gnt = kmalloc(sizeof(struct persistent_gnt),
 770                                                  GFP_KERNEL);
 771                         if (!persistent_gnt) {
 772                                 /*
 773                                  * If we don't have enough memory to
 774                                  * allocate the persistent_gnt struct
 775                                  * map this grant non-persistenly
 776                                  */
 777                                 goto next;
 778                         }
 779                         persistent_gnt->gnt = map[new_map_idx].ref;
 780                         persistent_gnt->handle = map[new_map_idx].handle;
 781                         persistent_gnt->page = pages[seg_idx]->page;
 782                         if (add_persistent_gnt(blkif,
 783                                                persistent_gnt)) {
 784                                 kfree(persistent_gnt);
 785                                 persistent_gnt = NULL;
 786                                 goto next;
 787                         }
 788                         pages[seg_idx]->persistent_gnt = persistent_gnt;
 789                         pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n",
 790                                  persistent_gnt->gnt, blkif->persistent_gnt_c,
 791                                  xen_blkif_max_pgrants);
 792                         goto next;
 793                 }
 794                 if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
 795                         blkif->vbd.overflow_max_grants = 1;
 796                         pr_debug(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n",
 797                                  blkif->domid, blkif->vbd.handle);
 798                 }
 799                 /*
 800                  * We could not map this grant persistently, so use it as
 801                  * a non-persistent grant.
 802                  */
 803 next:
 804                 new_map_idx++;
 805         }
 806         segs_to_map = 0;
 807         last_map = map_until;
 808         if (map_until != num)
 809                 goto again;
 810
 811         return ret;
 812
 813 out_of_memory:
 814         pr_alert(DRV_PFX "%s: out of memory\n", __func__);
 815         put_free_pages(blkif, pages_to_gnt, segs_to_map);
 816         return -ENOMEM;
 817 }
 818
 819 static int xen_blkbk_map_seg(struct pending_req *pending_req)
 820 {
 821         int rc;
 822
 823         rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
 824                            pending_req->nr_pages,
 825                            (pending_req->operation != BLKIF_OP_READ));
 826
 827         return rc;
 828 }
 829
 830 static int xen_blkbk_parse_indirect(struct blkif_request *req,
 831                                     struct pending_req *pending_req,
 832                                     struct seg_buf seg[],
 833                                     struct phys_req *preq)
 834 {
 835         struct grant_page **pages = pending_req->indirect_pages;
 836         struct xen_blkif *blkif = pending_req->blkif;
 837         int indirect_grefs, rc, n, nseg, i;
 838         struct blkif_request_segment_aligned *segments = NULL;
 839
 840         nseg = pending_req->nr_pages;
 841         indirect_grefs = INDIRECT_PAGES(nseg);
 842         BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 843
 844         for (i = 0; i < indirect_grefs; i++)
 845                 pages[i]->gref = req->u.indirect.indirect_grefs[i];
 846
 847         rc = xen_blkbk_map(blkif, pages, indirect_grefs, true);
 848         if (rc)
 849                 goto unmap;
 850
 851         for (n = 0, i = 0; n < nseg; n++) {
 852                 if ((n % SEGS_PER_INDIRECT_FRAME) == 0) {
 853                         /* Map indirect segments */
 854                         if (segments)
 855                                 kunmap_atomic(segments);
 856                         segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
 857                 }
 858                 i = n % SEGS_PER_INDIRECT_FRAME;
 859                 pending_req->segments[n]->gref = segments[i].gref;
 860                 seg[n].nsec = segments[i].last_sect -
 861                         segments[i].first_sect + 1;
 862                 seg[n].offset = (segments[i].first_sect << 9);
 863                 if ((segments[i].last_sect >= (PAGE_SIZE >> 9)) ||
 864                     (segments[i].last_sect < segments[i].first_sect)) {
 865                         rc = -EINVAL;
 866                         goto unmap;
 867                 }
 868                 preq->nr_sects += seg[n].nsec;
 869         }
 870
 871 unmap:
 872         if (segments)
 873                 kunmap_atomic(segments);
 874         xen_blkbk_unmap(blkif, pages, indirect_grefs);
 875         return rc;
 876 }
 877
 878 static int dispatch_discard_io(struct xen_blkif *blkif,
 879                                 struct blkif_request *req)
 880 {
 881         int err = 0;
 882         int status = BLKIF_RSP_OKAY;
 883         struct block_device *bdev = blkif->vbd.bdev;
 884         unsigned long secure;
 885         struct phys_req preq;
 886
 887         xen_blkif_get(blkif);
 888
 889         preq.sector_number = req->u.discard.sector_number;
 890         preq.nr_sects      = req->u.discard.nr_sectors;
 891
 892         err = xen_vbd_translate(&preq, blkif, WRITE);
 893         if (err) {
 894                 pr_warn(DRV_PFX "access denied: DISCARD [%llu->%llu] on dev=%04x\n",
 895                         preq.sector_number,
 896                         preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
 897                 goto fail_response;
 898         }
 899         blkif->st_ds_req++;
 900
 901         secure = (blkif->vbd.discard_secure &&
 902                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
 903                  BLKDEV_DISCARD_SECURE : 0;
 904
 905         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
 906                                    req->u.discard.nr_sectors,
 907                                    GFP_KERNEL, secure);
 908 fail_response:
 909         if (err == -EOPNOTSUPP) {
 910                 pr_debug(DRV_PFX "discard op failed, not supported\n");
 911                 status = BLKIF_RSP_EOPNOTSUPP;
 912         } else if (err)
 913                 status = BLKIF_RSP_ERROR;
 914
 915         make_response(blkif, req->u.discard.id, req->operation, status);
 916         xen_blkif_put(blkif);
 917         return err;
 918 }
 919
 920 static int dispatch_other_io(struct xen_blkif *blkif,
 921                              struct blkif_request *req,
 922                              struct pending_req *pending_req)
 923 {
 924         free_req(blkif, pending_req);
 925         make_response(blkif, req->u.other.id, req->operation,
 926                       BLKIF_RSP_EOPNOTSUPP);
 927         return -EIO;
 928 }
 929
 930 static void xen_blk_drain_io(struct xen_blkif *blkif)
 931 {
 932         atomic_set(&blkif->drain, 1);
 933         do {
 934                 /* The initial value is one, and one refcnt taken at the
 935                  * start of the xen_blkif_schedule thread. */
 936                 if (atomic_read(&blkif->refcnt) <= 2)
 937                         break;
 938                 wait_for_completion_interruptible_timeout(
 939                                 &blkif->drain_complete, HZ);
 940
 941                 if (!atomic_read(&blkif->drain))
 942                         break;
 943         } while (!kthread_should_stop());
 944         atomic_set(&blkif->drain, 0);
 945 }
 946
 947 /*
 948  * Completion callback on the bio's. Called as bh->b_end_io()
 949  */
 950
 951 static void __end_block_io_op(struct pending_req *pending_req, int error)
 952 {
 953         /* An error fails the entire request. */
 954         if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
 955             (error == -EOPNOTSUPP)) {
 956                 pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
 957                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
 958                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 959         } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
 960                     (error == -EOPNOTSUPP)) {
 961                 pr_debug(DRV_PFX "write barrier op failed, not supported\n");
 962                 xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
 963                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 964         } else if (error) {
 965                 pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
 966                          " error=%d\n", error);
 967                 pending_req->status = BLKIF_RSP_ERROR;
 968         }
 969
 970         /*
 971          * If all of the bio's have completed it is time to unmap
 972          * the grant references associated with 'request' and provide
 973          * the proper response on the ring.
 974          */
 975         if (atomic_dec_and_test(&pending_req->pendcnt)) {
 976                 xen_blkbk_unmap(pending_req->blkif,
 977                                 pending_req->segments,
 978                                 pending_req->nr_pages);
 979                 make_response(pending_req->blkif, pending_req->id,
 980                               pending_req->operation, pending_req->status);
 981                 xen_blkif_put(pending_req->blkif);
 982                 if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
 983                         if (atomic_read(&pending_req->blkif->drain))
 984                                 complete(&pending_req->blkif->drain_complete);
 985                 }
 986                 free_req(pending_req->blkif, pending_req);
 987         }
 988 }
 989
 990 /*
 991  * bio callback.
 992  */
 993 static void end_block_io_op(struct bio *bio, int error)
 994 {
 995         __end_block_io_op(bio->bi_private, error);
 996         bio_put(bio);
 997 }
 998
 999
1000
1001 /*
1002  * Function to copy the from the ring buffer the 'struct blkif_request'
1003  * (which has the sectors we want, number of them, grant references, etc),
1004  * and transmute  it to the block API to hand it over to the proper block disk.
1005  */
1006 static int
1007 __do_block_io_op(struct xen_blkif *blkif)
1008 {
1009         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1010         struct blkif_request req;
1011         struct pending_req *pending_req;
1012         RING_IDX rc, rp;
1013         int more_to_do = 0;
1014
1015         rc = blk_rings->common.req_cons;
1016         rp = blk_rings->common.sring->req_prod;
1017         rmb(); /* Ensure we see queued requests up to 'rp'. */
1018
1019         if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
1020                 rc = blk_rings->common.rsp_prod_pvt;
1021                 pr_warn(DRV_PFX "Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n",
1022                         rp, rc, rp - rc, blkif->vbd.pdevice);
1023                 return -EACCES;
1024         }
1025         while (rc != rp) {
1026
1027                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1028                         break;
1029
1030                 if (kthread_should_stop()) {
1031                         more_to_do = 1;
1032                         break;
1033                 }
1034
1035                 pending_req = alloc_req(blkif);
1036                 if (NULL == pending_req) {
1037                         blkif->st_oo_req++;
1038                         more_to_do = 1;
1039                         break;
1040                 }
1041
1042                 switch (blkif->blk_protocol) {
1043                 case BLKIF_PROTOCOL_NATIVE:
1044                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1045                         break;
1046                 case BLKIF_PROTOCOL_X86_32:
1047                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1048                         break;
1049                 case BLKIF_PROTOCOL_X86_64:
1050                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1051                         break;
1052                 default:
1053                         BUG();
1054                 }
1055                 blk_rings->common.req_cons = ++rc; /* before make_response() */
1056
1057                 /* Apply all sanity checks to /private copy/ of request. */
1058                 barrier();
1059
1060                 switch (req.operation) {
1061                 case BLKIF_OP_READ:
1062                 case BLKIF_OP_WRITE:
1063                 case BLKIF_OP_WRITE_BARRIER:
1064                 case BLKIF_OP_FLUSH_DISKCACHE:
1065                 case BLKIF_OP_INDIRECT:
1066                         if (dispatch_rw_block_io(blkif, &req, pending_req))
1067                                 goto done;
1068                         break;
1069                 case BLKIF_OP_DISCARD:
1070                         free_req(blkif, pending_req);
1071                         if (dispatch_discard_io(blkif, &req))
1072                                 goto done;
1073                         break;
1074                 default:
1075                         if (dispatch_other_io(blkif, &req, pending_req))
1076                                 goto done;
1077                         break;
1078                 }
1079
1080                 /* Yield point for this unbounded loop. */
1081                 cond_resched();
1082         }
1083 done:
1084         return more_to_do;
1085 }
1086
1087 static int
1088 do_block_io_op(struct xen_blkif *blkif)
1089 {
1090         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1091         int more_to_do;
1092
1093         do {
1094                 more_to_do = __do_block_io_op(blkif);
1095                 if (more_to_do)
1096                         break;
1097
1098                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1099         } while (more_to_do);
1100
1101         return more_to_do;
1102 }
1103 /*
1104  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1105  * and call the 'submit_bio' to pass it to the underlying storage.
1106  */
1107 static int dispatch_rw_block_io(struct xen_blkif *blkif,
1108                                 struct blkif_request *req,
1109                                 struct pending_req *pending_req)
1110 {
1111         struct phys_req preq;
1112         struct seg_buf *seg = pending_req->seg;
1113         unsigned int nseg;
1114         struct bio *bio = NULL;
1115         struct bio **biolist = pending_req->biolist;
1116         int i, nbio = 0;
1117         int operation;
1118         struct blk_plug plug;
1119         bool drain = false;
1120         struct grant_page **pages = pending_req->segments;
1121         unsigned short req_operation;
1122
1123         req_operation = req->operation == BLKIF_OP_INDIRECT ?
1124                         req->u.indirect.indirect_op : req->operation;
1125         if ((req->operation == BLKIF_OP_INDIRECT) &&
1126             (req_operation != BLKIF_OP_READ) &&
1127             (req_operation != BLKIF_OP_WRITE)) {
1128                 pr_debug(DRV_PFX "Invalid indirect operation (%u)\n",
1129                          req_operation);
1130                 goto fail_response;
1131         }
1132
1133         switch (req_operation) {
1134         case BLKIF_OP_READ:
1135                 blkif->st_rd_req++;
1136                 operation = READ;
1137                 break;
1138         case BLKIF_OP_WRITE:
1139                 blkif->st_wr_req++;
1140                 operation = WRITE_ODIRECT;
1141                 break;
1142         case BLKIF_OP_WRITE_BARRIER:
1143                 drain = true;
1144         case BLKIF_OP_FLUSH_DISKCACHE:
1145                 blkif->st_f_req++;
1146                 operation = WRITE_FLUSH;
1147                 break;
1148         default:
1149                 operation = 0; /* make gcc happy */
1150                 goto fail_response;
1151                 break;
1152         }
1153
1154         /* Check that the number of segments is sane. */
1155         nseg = req->operation == BLKIF_OP_INDIRECT ?
1156                req->u.indirect.nr_segments : req->u.rw.nr_segments;
1157
1158         if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
1159             unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1160                      (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1161             unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1162                      (nseg > MAX_INDIRECT_SEGMENTS))) {
1163                 pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
1164                          nseg);
1165                 /* Haven't submitted any bio's yet. */
1166                 goto fail_response;
1167         }
1168
1169         preq.nr_sects      = 0;
1170
1171         pending_req->blkif     = blkif;
1172         pending_req->id        = req->u.rw.id;
1173         pending_req->operation = req_operation;
1174         pending_req->status    = BLKIF_RSP_OKAY;
1175         pending_req->nr_pages  = nseg;
1176
1177         if (req->operation != BLKIF_OP_INDIRECT) {
1178                 preq.dev               = req->u.rw.handle;
1179                 preq.sector_number     = req->u.rw.sector_number;
1180                 for (i = 0; i < nseg; i++) {
1181                         pages[i]->gref = req->u.rw.seg[i].gref;
1182                         seg[i].nsec = req->u.rw.seg[i].last_sect -
1183                                 req->u.rw.seg[i].first_sect + 1;
1184                         seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1185                         if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
1186                             (req->u.rw.seg[i].last_sect <
1187                              req->u.rw.seg[i].first_sect))
1188                                 goto fail_response;
1189                         preq.nr_sects += seg[i].nsec;
1190                 }
1191         } else {
1192                 preq.dev               = req->u.indirect.handle;
1193                 preq.sector_number     = req->u.indirect.sector_number;
1194                 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1195                         goto fail_response;
1196         }
1197
1198         if (xen_vbd_translate(&preq, blkif, operation) != 0) {
1199                 pr_debug(DRV_PFX "access denied: %s of [%llu,%llu] on dev=%04x\n",
1200                          operation == READ ? "read" : "write",
1201                          preq.sector_number,
1202                          preq.sector_number + preq.nr_sects,
1203                          blkif->vbd.pdevice);
1204                 goto fail_response;
1205         }
1206
1207         /*
1208          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1209          * is set there.
1210          */
1211         for (i = 0; i < nseg; i++) {
1212                 if (((int)preq.sector_number|(int)seg[i].nsec) &
1213                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1214                         pr_debug(DRV_PFX "Misaligned I/O request from domain %d",
1215                                  blkif->domid);
1216                         goto fail_response;
1217                 }
1218         }
1219
1220         /* Wait on all outstanding I/O's and once that has been completed
1221          * issue the WRITE_FLUSH.
1222          */
1223         if (drain)
1224                 xen_blk_drain_io(pending_req->blkif);
1225
1226         /*
1227          * If we have failed at this point, we need to undo the M2P override,
1228          * set gnttab_set_unmap_op on all of the grant references and perform
1229          * the hypercall to unmap the grants - that is all done in
1230          * xen_blkbk_unmap.
1231          */
1232         if (xen_blkbk_map_seg(pending_req))
1233                 goto fail_flush;
1234
1235         /*
1236          * This corresponding xen_blkif_put is done in __end_block_io_op, or
1237          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1238          */
1239         xen_blkif_get(blkif);
1240
1241         for (i = 0; i < nseg; i++) {
1242                 while ((bio == NULL) ||
1243                        (bio_add_page(bio,
1244                                      pages[i]->page,
1245                                      seg[i].nsec << 9,
1246                                      seg[i].offset) == 0)) {
1247
1248                         int nr_iovecs = min_t(int, (nseg-i), BIO_MAX_PAGES);
1249                         bio = bio_alloc(GFP_KERNEL, nr_iovecs);
1250                         if (unlikely(bio == NULL))
1251                                 goto fail_put_bio;
1252
1253                         biolist[nbio++] = bio;
1254                         bio->bi_bdev    = preq.bdev;
1255                         bio->bi_private = pending_req;
1256                         bio->bi_end_io  = end_block_io_op;
1257                         bio->bi_iter.bi_sector  = preq.sector_number;
1258                 }
1259
1260                 preq.sector_number += seg[i].nsec;
1261         }
1262
1263         /* This will be hit if the operation was a flush or discard. */
1264         if (!bio) {
1265                 BUG_ON(operation != WRITE_FLUSH);
1266
1267                 bio = bio_alloc(GFP_KERNEL, 0);
1268                 if (unlikely(bio == NULL))
1269                         goto fail_put_bio;
1270
1271                 biolist[nbio++] = bio;
1272                 bio->bi_bdev    = preq.bdev;
1273                 bio->bi_private = pending_req;
1274                 bio->bi_end_io  = end_block_io_op;
1275         }
1276
1277         atomic_set(&pending_req->pendcnt, nbio);
1278         blk_start_plug(&plug);
1279
1280         for (i = 0; i < nbio; i++)
1281                 submit_bio(operation, biolist[i]);
1282
1283         /* Let the I/Os go.. */
1284         blk_finish_plug(&plug);
1285
1286         if (operation == READ)
1287                 blkif->st_rd_sect += preq.nr_sects;
1288         else if (operation & WRITE)
1289                 blkif->st_wr_sect += preq.nr_sects;
1290
1291         return 0;
1292
1293  fail_flush:
1294         xen_blkbk_unmap(blkif, pending_req->segments,
1295                         pending_req->nr_pages);
1296  fail_response:
1297         /* Haven't submitted any bio's yet. */
1298         make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1299         free_req(blkif, pending_req);
1300         msleep(1); /* back off a bit */
1301         return -EIO;
1302
1303  fail_put_bio:
1304         for (i = 0; i < nbio; i++)
1305                 bio_put(biolist[i]);
1306         atomic_set(&pending_req->pendcnt, 1);
1307         __end_block_io_op(pending_req, -EINVAL);
1308         msleep(1); /* back off a bit */
1309         return -EIO;
1310 }
1311
1312
1313
1314 /*
1315  * Put a response on the ring on how the operation fared.
1316  */
1317 static void make_response(struct xen_blkif *blkif, u64 id,
1318                           unsigned short op, int st)
1319 {
1320         struct blkif_response  resp;
1321         unsigned long     flags;
1322         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1323         int notify;
1324
1325         resp.id        = id;
1326         resp.operation = op;
1327         resp.status    = st;
1328
1329         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
1330         /* Place on the response ring for the relevant domain. */
1331         switch (blkif->blk_protocol) {
1332         case BLKIF_PROTOCOL_NATIVE:
1333                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
1334                        &resp, sizeof(resp));
1335                 break;
1336         case BLKIF_PROTOCOL_X86_32:
1337                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
1338                        &resp, sizeof(resp));
1339                 break;
1340         case BLKIF_PROTOCOL_X86_64:
1341                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
1342                        &resp, sizeof(resp));
1343                 break;
1344         default:
1345                 BUG();
1346         }
1347         blk_rings->common.rsp_prod_pvt++;
1348         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1349         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
1350         if (notify)
1351                 notify_remote_via_irq(blkif->irq);
1352 }
1353
1354 static int __init xen_blkif_init(void)
1355 {
1356         int rc = 0;
1357
1358         if (!xen_domain())
1359                 return -ENODEV;
1360
1361         rc = xen_blkif_interface_init();
1362         if (rc)
1363                 goto failed_init;
1364
1365         rc = xen_blkif_xenbus_init();
1366         if (rc)
1367                 goto failed_init;
1368
1369  failed_init:
1370         return rc;
1371 }
1372
1373 module_init(xen_blkif_init);
1374
1375 MODULE_LICENSE("Dual BSD/GPL");
1376 MODULE_ALIAS("xen-backend:vbd");