kernel/drivers/block/xen-blkback/blkback.c

   1 /******************************************************************************
   2  *
   3  * Back-end of the driver for virtual block devices. This portion of the
   4  * driver exports a 'unified' block-device interface that can be accessed
   5  * by any operating system that implements a compatible front end. A
   6  * reference front-end implementation can be found in:
   7  *  drivers/block/xen-blkfront.c
   8  *
   9  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
  10  * Copyright (c) 2005, Christopher Clark
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License version 2
  14  * as published by the Free Software Foundation; or, when distributed
  15  * separately from the Linux kernel or incorporated into other
  16  * software packages, subject to the following license:
  17  *
  18  * Permission is hereby granted, free of charge, to any person obtaining a copy
  19  * of this source file (the "Software"), to deal in the Software without
  20  * restriction, including without limitation the rights to use, copy, modify,
  21  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  22  * and to permit persons to whom the Software is furnished to do so, subject to
  23  * the following conditions:
  24  *
  25  * The above copyright notice and this permission notice shall be included in
  26  * all copies or substantial portions of the Software.
  27  *
  28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  29  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  30  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  31  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  32  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  33  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  34  * IN THE SOFTWARE.
  35  */
  36
  37 #define pr_fmt(fmt) "xen-blkback: " fmt
  38
  39 #include <linux/spinlock.h>
  40 #include <linux/kthread.h>
  41 #include <linux/list.h>
  42 #include <linux/delay.h>
  43 #include <linux/freezer.h>
  44 #include <linux/bitmap.h>
  45
  46 #include <xen/events.h>
  47 #include <xen/page.h>
  48 #include <xen/xen.h>
  49 #include <asm/xen/hypervisor.h>
  50 #include <asm/xen/hypercall.h>
  51 #include <xen/balloon.h>
  52 #include <xen/grant_table.h>
  53 #include "common.h"
  54
  55 /*
  56  * Maximum number of unused free pages to keep in the internal buffer.
  57  * Setting this to a value too low will reduce memory used in each backend,
  58  * but can have a performance penalty.
  59  *
  60  * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can
  61  * be set to a lower value that might degrade performance on some intensive
  62  * IO workloads.
  63  */
  64
  65 static int xen_blkif_max_buffer_pages = 1024;
  66 module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644);
  67 MODULE_PARM_DESC(max_buffer_pages,
  68 "Maximum number of free pages to keep in each block backend buffer");
  69
  70 /*
  71  * Maximum number of grants to map persistently in blkback. For maximum
  72  * performance this should be the total numbers of grants that can be used
  73  * to fill the ring, but since this might become too high, specially with
  74  * the use of indirect descriptors, we set it to a value that provides good
  75  * performance without using too much memory.
  76  *
  77  * When the list of persistent grants is full we clean it up using a LRU
  78  * algorithm.
  79  */
  80
  81 static int xen_blkif_max_pgrants = 1056;
  82 module_param_named(max_persistent_grants, xen_blkif_max_pgrants, int, 0644);
  83 MODULE_PARM_DESC(max_persistent_grants,
  84                  "Maximum number of grants to map persistently");
  85
  86 /*
  87  * The LRU mechanism to clean the lists of persistent grants needs to
  88  * be executed periodically. The time interval between consecutive executions
  89  * of the purge mechanism is set in ms.
  90  */
  91 #define LRU_INTERVAL 100
  92
  93 /*
  94  * When the persistent grants list is full we will remove unused grants
  95  * from the list. The percent number of grants to be removed at each LRU
  96  * execution.
  97  */
  98 #define LRU_PERCENT_CLEAN 5
  99
 100 /* Run-time switchable: /sys/module/blkback/parameters/ */
 101 static unsigned int log_stats;
 102 module_param(log_stats, int, 0644);
 103
 104 #define BLKBACK_INVALID_HANDLE (~0)
 105
 106 /* Number of free pages to remove on each call to gnttab_free_pages */
 107 #define NUM_BATCH_FREE_PAGES 10
 108
 109 static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
 110 {
 111         unsigned long flags;
 112
 113         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 114         if (list_empty(&blkif->free_pages)) {
 115                 BUG_ON(blkif->free_pages_num != 0);
 116                 spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 117                 return gnttab_alloc_pages(1, page);
 118         }
 119         BUG_ON(blkif->free_pages_num == 0);
 120         page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
 121         list_del(&page[0]->lru);
 122         blkif->free_pages_num--;
 123         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 124
 125         return 0;
 126 }
 127
 128 static inline void put_free_pages(struct xen_blkif *blkif, struct page **page,
 129                                   int num)
 130 {
 131         unsigned long flags;
 132         int i;
 133
 134         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 135         for (i = 0; i < num; i++)
 136                 list_add(&page[i]->lru, &blkif->free_pages);
 137         blkif->free_pages_num += num;
 138         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 139 }
 140
 141 static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
 142 {
 143         /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
 144         struct page *page[NUM_BATCH_FREE_PAGES];
 145         unsigned int num_pages = 0;
 146         unsigned long flags;
 147
 148         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 149         while (blkif->free_pages_num > num) {
 150                 BUG_ON(list_empty(&blkif->free_pages));
 151                 page[num_pages] = list_first_entry(&blkif->free_pages,
 152                                                    struct page, lru);
 153                 list_del(&page[num_pages]->lru);
 154                 blkif->free_pages_num--;
 155                 if (++num_pages == NUM_BATCH_FREE_PAGES) {
 156                         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 157                         gnttab_free_pages(num_pages, page);
 158                         spin_lock_irqsave(&blkif->free_pages_lock, flags);
 159                         num_pages = 0;
 160                 }
 161         }
 162         spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
 163         if (num_pages != 0)
 164                 gnttab_free_pages(num_pages, page);
 165 }
 166
 167 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 168
 169 static int do_block_io_op(struct xen_blkif *blkif);
 170 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 171                                 struct blkif_request *req,
 172                                 struct pending_req *pending_req);
 173 static void make_response(struct xen_blkif *blkif, u64 id,
 174                           unsigned short op, int st);
 175
 176 #define foreach_grant_safe(pos, n, rbtree, node) \
 177         for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
 178              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 179              &(pos)->node != NULL; \
 180              (pos) = container_of(n, typeof(*(pos)), node), \
 181              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
 182
 183
 184 /*
 185  * We don't need locking around the persistent grant helpers
 186  * because blkback uses a single-thread for each backed, so we
 187  * can be sure that this functions will never be called recursively.
 188  *
 189  * The only exception to that is put_persistent_grant, that can be called
 190  * from interrupt context (by xen_blkbk_unmap), so we have to use atomic
 191  * bit operations to modify the flags of a persistent grant and to count
 192  * the number of used grants.
 193  */
 194 static int add_persistent_gnt(struct xen_blkif *blkif,
 195                                struct persistent_gnt *persistent_gnt)
 196 {
 197         struct rb_node **new = NULL, *parent = NULL;
 198         struct persistent_gnt *this;
 199
 200         if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
 201                 if (!blkif->vbd.overflow_max_grants)
 202                         blkif->vbd.overflow_max_grants = 1;
 203                 return -EBUSY;
 204         }
 205         /* Figure out where to put new node */
 206         new = &blkif->persistent_gnts.rb_node;
 207         while (*new) {
 208                 this = container_of(*new, struct persistent_gnt, node);
 209
 210                 parent = *new;
 211                 if (persistent_gnt->gnt < this->gnt)
 212                         new = &((*new)->rb_left);
 213                 else if (persistent_gnt->gnt > this->gnt)
 214                         new = &((*new)->rb_right);
 215                 else {
 216                         pr_alert_ratelimited("trying to add a gref that's already in the tree\n");
 217                         return -EINVAL;
 218                 }
 219         }
 220
 221         bitmap_zero(persistent_gnt->flags, PERSISTENT_GNT_FLAGS_SIZE);
 222         set_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 223         /* Add new node and rebalance tree. */
 224         rb_link_node(&(persistent_gnt->node), parent, new);
 225         rb_insert_color(&(persistent_gnt->node), &blkif->persistent_gnts);
 226         blkif->persistent_gnt_c++;
 227         atomic_inc(&blkif->persistent_gnt_in_use);
 228         return 0;
 229 }
 230
 231 static struct persistent_gnt *get_persistent_gnt(struct xen_blkif *blkif,
 232                                                  grant_ref_t gref)
 233 {
 234         struct persistent_gnt *data;
 235         struct rb_node *node = NULL;
 236
 237         node = blkif->persistent_gnts.rb_node;
 238         while (node) {
 239                 data = container_of(node, struct persistent_gnt, node);
 240
 241                 if (gref < data->gnt)
 242                         node = node->rb_left;
 243                 else if (gref > data->gnt)
 244                         node = node->rb_right;
 245                 else {
 246                         if(test_bit(PERSISTENT_GNT_ACTIVE, data->flags)) {
 247                                 pr_alert_ratelimited("requesting a grant already in use\n");
 248                                 return NULL;
 249                         }
 250                         set_bit(PERSISTENT_GNT_ACTIVE, data->flags);
 251                         atomic_inc(&blkif->persistent_gnt_in_use);
 252                         return data;
 253                 }
 254         }
 255         return NULL;
 256 }
 257
 258 static void put_persistent_gnt(struct xen_blkif *blkif,
 259                                struct persistent_gnt *persistent_gnt)
 260 {
 261         if(!test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 262                 pr_alert_ratelimited("freeing a grant already unused\n");
 263         set_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 264         clear_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags);
 265         atomic_dec(&blkif->persistent_gnt_in_use);
 266 }
 267
 268 static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root,
 269                                  unsigned int num)
 270 {
 271         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 272         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 273         struct persistent_gnt *persistent_gnt;
 274         struct rb_node *n;
 275         int segs_to_unmap = 0;
 276         struct gntab_unmap_queue_data unmap_data;
 277
 278         unmap_data.pages = pages;
 279         unmap_data.unmap_ops = unmap;
 280         unmap_data.kunmap_ops = NULL;
 281
 282         foreach_grant_safe(persistent_gnt, n, root, node) {
 283                 BUG_ON(persistent_gnt->handle ==
 284                         BLKBACK_INVALID_HANDLE);
 285                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 286                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 287                                 persistent_gnt->page)),
 288                         GNTMAP_host_map,
 289                         persistent_gnt->handle);
 290
 291                 pages[segs_to_unmap] = persistent_gnt->page;
 292
 293                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 294                         !rb_next(&persistent_gnt->node)) {
 295
 296                         unmap_data.count = segs_to_unmap;
 297                         BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 298
 299                         put_free_pages(blkif, pages, segs_to_unmap);
 300                         segs_to_unmap = 0;
 301                 }
 302
 303                 rb_erase(&persistent_gnt->node, root);
 304                 kfree(persistent_gnt);
 305                 num--;
 306         }
 307         BUG_ON(num != 0);
 308 }
 309
 310 void xen_blkbk_unmap_purged_grants(struct work_struct *work)
 311 {
 312         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 313         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 314         struct persistent_gnt *persistent_gnt;
 315         int segs_to_unmap = 0;
 316         struct xen_blkif *blkif = container_of(work, typeof(*blkif), persistent_purge_work);
 317         struct gntab_unmap_queue_data unmap_data;
 318
 319         unmap_data.pages = pages;
 320         unmap_data.unmap_ops = unmap;
 321         unmap_data.kunmap_ops = NULL;
 322
 323         while(!list_empty(&blkif->persistent_purge_list)) {
 324                 persistent_gnt = list_first_entry(&blkif->persistent_purge_list,
 325                                                   struct persistent_gnt,
 326                                                   remove_node);
 327                 list_del(&persistent_gnt->remove_node);
 328
 329                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 330                         vaddr(persistent_gnt->page),
 331                         GNTMAP_host_map,
 332                         persistent_gnt->handle);
 333
 334                 pages[segs_to_unmap] = persistent_gnt->page;
 335
 336                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 337                         unmap_data.count = segs_to_unmap;
 338                         BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 339                         put_free_pages(blkif, pages, segs_to_unmap);
 340                         segs_to_unmap = 0;
 341                 }
 342                 kfree(persistent_gnt);
 343         }
 344         if (segs_to_unmap > 0) {
 345                 unmap_data.count = segs_to_unmap;
 346                 BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 347                 put_free_pages(blkif, pages, segs_to_unmap);
 348         }
 349 }
 350
 351 static void purge_persistent_gnt(struct xen_blkif *blkif)
 352 {
 353         struct persistent_gnt *persistent_gnt;
 354         struct rb_node *n;
 355         unsigned int num_clean, total;
 356         bool scan_used = false, clean_used = false;
 357         struct rb_root *root;
 358
 359         if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
 360             (blkif->persistent_gnt_c == xen_blkif_max_pgrants &&
 361             !blkif->vbd.overflow_max_grants)) {
 362                 return;
 363         }
 364
 365         if (work_pending(&blkif->persistent_purge_work)) {
 366                 pr_alert_ratelimited("Scheduled work from previous purge is still pending, cannot purge list\n");
 367                 return;
 368         }
 369
 370         num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
 371         num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
 372         num_clean = min(blkif->persistent_gnt_c, num_clean);
 373         if ((num_clean == 0) ||
 374             (num_clean > (blkif->persistent_gnt_c - atomic_read(&blkif->persistent_gnt_in_use))))
 375                 return;
 376
 377         /*
 378          * At this point, we can assure that there will be no calls
 379          * to get_persistent_grant (because we are executing this code from
 380          * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
 381          * which means that the number of currently used grants will go down,
 382          * but never up, so we will always be able to remove the requested
 383          * number of grants.
 384          */
 385
 386         total = num_clean;
 387
 388         pr_debug("Going to purge %u persistent grants\n", num_clean);
 389
 390         BUG_ON(!list_empty(&blkif->persistent_purge_list));
 391         root = &blkif->persistent_gnts;
 392 purge_list:
 393         foreach_grant_safe(persistent_gnt, n, root, node) {
 394                 BUG_ON(persistent_gnt->handle ==
 395                         BLKBACK_INVALID_HANDLE);
 396
 397                 if (clean_used) {
 398                         clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
 399                         continue;
 400                 }
 401
 402                 if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
 403                         continue;
 404                 if (!scan_used &&
 405                     (test_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags)))
 406                         continue;
 407
 408                 rb_erase(&persistent_gnt->node, root);
 409                 list_add(&persistent_gnt->remove_node,
 410                          &blkif->persistent_purge_list);
 411                 if (--num_clean == 0)
 412                         goto finished;
 413         }
 414         /*
 415          * If we get here it means we also need to start cleaning
 416          * grants that were used since last purge in order to cope
 417          * with the requested num
 418          */
 419         if (!scan_used && !clean_used) {
 420                 pr_debug("Still missing %u purged frames\n", num_clean);
 421                 scan_used = true;
 422                 goto purge_list;
 423         }
 424 finished:
 425         if (!clean_used) {
 426                 pr_debug("Finished scanning for grants to clean, removing used flag\n");
 427                 clean_used = true;
 428                 goto purge_list;
 429         }
 430
 431         blkif->persistent_gnt_c -= (total - num_clean);
 432         blkif->vbd.overflow_max_grants = 0;
 433
 434         /* We can defer this work */
 435         schedule_work(&blkif->persistent_purge_work);
 436         pr_debug("Purged %u/%u\n", (total - num_clean), total);
 437         return;
 438 }
 439
 440 /*
 441  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 442  */
 443 static struct pending_req *alloc_req(struct xen_blkif *blkif)
 444 {
 445         struct pending_req *req = NULL;
 446         unsigned long flags;
 447
 448         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 449         if (!list_empty(&blkif->pending_free)) {
 450                 req = list_entry(blkif->pending_free.next, struct pending_req,
 451                                  free_list);
 452                 list_del(&req->free_list);
 453         }
 454         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 455         return req;
 456 }
 457
 458 /*
 459  * Return the 'pending_req' structure back to the freepool. We also
 460  * wake up the thread if it was waiting for a free page.
 461  */
 462 static void free_req(struct xen_blkif *blkif, struct pending_req *req)
 463 {
 464         unsigned long flags;
 465         int was_empty;
 466
 467         spin_lock_irqsave(&blkif->pending_free_lock, flags);
 468         was_empty = list_empty(&blkif->pending_free);
 469         list_add(&req->free_list, &blkif->pending_free);
 470         spin_unlock_irqrestore(&blkif->pending_free_lock, flags);
 471         if (was_empty)
 472                 wake_up(&blkif->pending_free_wq);
 473 }
 474
 475 /*
 476  * Routines for managing virtual block devices (vbds).
 477  */
 478 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 479                              int operation)
 480 {
 481         struct xen_vbd *vbd = &blkif->vbd;
 482         int rc = -EACCES;
 483
 484         if ((operation != READ) && vbd->readonly)
 485                 goto out;
 486
 487         if (likely(req->nr_sects)) {
 488                 blkif_sector_t end = req->sector_number + req->nr_sects;
 489
 490                 if (unlikely(end < req->sector_number))
 491                         goto out;
 492                 if (unlikely(end > vbd_sz(vbd)))
 493                         goto out;
 494         }
 495
 496         req->dev  = vbd->pdevice;
 497         req->bdev = vbd->bdev;
 498         rc = 0;
 499
 500  out:
 501         return rc;
 502 }
 503
 504 static void xen_vbd_resize(struct xen_blkif *blkif)
 505 {
 506         struct xen_vbd *vbd = &blkif->vbd;
 507         struct xenbus_transaction xbt;
 508         int err;
 509         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 510         unsigned long long new_size = vbd_sz(vbd);
 511
 512         pr_info("VBD Resize: Domid: %d, Device: (%d, %d)\n",
 513                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 514         pr_info("VBD Resize: new size %llu\n", new_size);
 515         vbd->size = new_size;
 516 again:
 517         err = xenbus_transaction_start(&xbt);
 518         if (err) {
 519                 pr_warn("Error starting transaction\n");
 520                 return;
 521         }
 522         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 523                             (unsigned long long)vbd_sz(vbd));
 524         if (err) {
 525                 pr_warn("Error writing new size\n");
 526                 goto abort;
 527         }
 528         /*
 529          * Write the current state; we will use this to synchronize
 530          * the front-end. If the current state is "connected" the
 531          * front-end will get the new size information online.
 532          */
 533         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 534         if (err) {
 535                 pr_warn("Error writing the state\n");
 536                 goto abort;
 537         }
 538
 539         err = xenbus_transaction_end(xbt, 0);
 540         if (err == -EAGAIN)
 541                 goto again;
 542         if (err)
 543                 pr_warn("Error ending transaction\n");
 544         return;
 545 abort:
 546         xenbus_transaction_end(xbt, 1);
 547 }
 548
 549 /*
 550  * Notification from the guest OS.
 551  */
 552 static void blkif_notify_work(struct xen_blkif *blkif)
 553 {
 554         blkif->waiting_reqs = 1;
 555         wake_up(&blkif->wq);
 556 }
 557
 558 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 559 {
 560         blkif_notify_work(dev_id);
 561         return IRQ_HANDLED;
 562 }
 563
 564 /*
 565  * SCHEDULER FUNCTIONS
 566  */
 567
 568 static void print_stats(struct xen_blkif *blkif)
 569 {
 570         pr_info("(%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
 571                  "  |  ds %4llu | pg: %4u/%4d\n",
 572                  current->comm, blkif->st_oo_req,
 573                  blkif->st_rd_req, blkif->st_wr_req,
 574                  blkif->st_f_req, blkif->st_ds_req,
 575                  blkif->persistent_gnt_c,
 576                  xen_blkif_max_pgrants);
 577         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 578         blkif->st_rd_req = 0;
 579         blkif->st_wr_req = 0;
 580         blkif->st_oo_req = 0;
 581         blkif->st_ds_req = 0;
 582 }
 583
 584 int xen_blkif_schedule(void *arg)
 585 {
 586         struct xen_blkif *blkif = arg;
 587         struct xen_vbd *vbd = &blkif->vbd;
 588         unsigned long timeout;
 589         int ret;
 590
 591         xen_blkif_get(blkif);
 592
 593         while (!kthread_should_stop()) {
 594                 if (try_to_freeze())
 595                         continue;
 596                 if (unlikely(vbd->size != vbd_sz(vbd)))
 597                         xen_vbd_resize(blkif);
 598
 599                 timeout = msecs_to_jiffies(LRU_INTERVAL);
 600
 601                 timeout = wait_event_interruptible_timeout(
 602                         blkif->wq,
 603                         blkif->waiting_reqs || kthread_should_stop(),
 604                         timeout);
 605                 if (timeout == 0)
 606                         goto purge_gnt_list;
 607                 timeout = wait_event_interruptible_timeout(
 608                         blkif->pending_free_wq,
 609                         !list_empty(&blkif->pending_free) ||
 610                         kthread_should_stop(),
 611                         timeout);
 612                 if (timeout == 0)
 613                         goto purge_gnt_list;
 614
 615                 blkif->waiting_reqs = 0;
 616                 smp_mb(); /* clear flag *before* checking for work */
 617
 618                 ret = do_block_io_op(blkif);
 619                 if (ret > 0)
 620                         blkif->waiting_reqs = 1;
 621                 if (ret == -EACCES)
 622                         wait_event_interruptible(blkif->shutdown_wq,
 623                                                  kthread_should_stop());
 624
 625 purge_gnt_list:
 626                 if (blkif->vbd.feature_gnt_persistent &&
 627                     time_after(jiffies, blkif->next_lru)) {
 628                         purge_persistent_gnt(blkif);
 629                         blkif->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
 630                 }
 631
 632                 /* Shrink if we have more than xen_blkif_max_buffer_pages */
 633                 shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages);
 634
 635                 if (log_stats && time_after(jiffies, blkif->st_print))
 636                         print_stats(blkif);
 637         }
 638
 639         /* Drain pending purge work */
 640         flush_work(&blkif->persistent_purge_work);
 641
 642         if (log_stats)
 643                 print_stats(blkif);
 644
 645         blkif->xenblkd = NULL;
 646         xen_blkif_put(blkif);
 647
 648         return 0;
 649 }
 650
 651 /*
 652  * Remove persistent grants and empty the pool of free pages
 653  */
 654 void xen_blkbk_free_caches(struct xen_blkif *blkif)
 655 {
 656         /* Free all persistent grant pages */
 657         if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
 658                 free_persistent_gnts(blkif, &blkif->persistent_gnts,
 659                         blkif->persistent_gnt_c);
 660
 661         BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 662         blkif->persistent_gnt_c = 0;
 663
 664         /* Since we are shutting down remove all pages from the buffer */
 665         shrink_free_pagepool(blkif, 0 /* All */);
 666 }
 667
 668 static unsigned int xen_blkbk_unmap_prepare(
 669         struct xen_blkif *blkif,
 670         struct grant_page **pages,
 671         unsigned int num,
 672         struct gnttab_unmap_grant_ref *unmap_ops,
 673         struct page **unmap_pages)
 674 {
 675         unsigned int i, invcount = 0;
 676
 677         for (i = 0; i < num; i++) {
 678                 if (pages[i]->persistent_gnt != NULL) {
 679                         put_persistent_gnt(blkif, pages[i]->persistent_gnt);
 680                         continue;
 681                 }
 682                 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
 683                         continue;
 684                 unmap_pages[invcount] = pages[i]->page;
 685                 gnttab_set_unmap_op(&unmap_ops[invcount], vaddr(pages[i]->page),
 686                                     GNTMAP_host_map, pages[i]->handle);
 687                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
 688                 invcount++;
 689        }
 690
 691        return invcount;
 692 }
 693
 694 static void xen_blkbk_unmap_and_respond_callback(int result, struct gntab_unmap_queue_data *data)
 695 {
 696         struct pending_req* pending_req = (struct pending_req*) (data->data);
 697         struct xen_blkif *blkif = pending_req->blkif;
 698
 699         /* BUG_ON used to reproduce existing behaviour,
 700            but is this the best way to deal with this? */
 701         BUG_ON(result);
 702
 703         put_free_pages(blkif, data->pages, data->count);
 704         make_response(blkif, pending_req->id,
 705                       pending_req->operation, pending_req->status);
 706         free_req(blkif, pending_req);
 707         /*
 708          * Make sure the request is freed before releasing blkif,
 709          * or there could be a race between free_req and the
 710          * cleanup done in xen_blkif_free during shutdown.
 711          *
 712          * NB: The fact that we might try to wake up pending_free_wq
 713          * before drain_complete (in case there's a drain going on)
 714          * it's not a problem with our current implementation
 715          * because we can assure there's no thread waiting on
 716          * pending_free_wq if there's a drain going on, but it has
 717          * to be taken into account if the current model is changed.
 718          */
 719         if (atomic_dec_and_test(&blkif->inflight) && atomic_read(&blkif->drain)) {
 720                 complete(&blkif->drain_complete);
 721         }
 722         xen_blkif_put(blkif);
 723 }
 724
 725 static void xen_blkbk_unmap_and_respond(struct pending_req *req)
 726 {
 727         struct gntab_unmap_queue_data* work = &req->gnttab_unmap_data;
 728         struct xen_blkif *blkif = req->blkif;
 729         struct grant_page **pages = req->segments;
 730         unsigned int invcount;
 731
 732         invcount = xen_blkbk_unmap_prepare(blkif, pages, req->nr_pages,
 733                                            req->unmap, req->unmap_pages);
 734
 735         work->data = req;
 736         work->done = xen_blkbk_unmap_and_respond_callback;
 737         work->unmap_ops = req->unmap;
 738         work->kunmap_ops = NULL;
 739         work->pages = req->unmap_pages;
 740         work->count = invcount;
 741
 742         gnttab_unmap_refs_async(&req->gnttab_unmap_data);
 743 }
 744
 745
 746 /*
 747  * Unmap the grant references.
 748  *
 749  * This could accumulate ops up to the batch size to reduce the number
 750  * of hypercalls, but since this is only used in error paths there's
 751  * no real need.
 752  */
 753 static void xen_blkbk_unmap(struct xen_blkif *blkif,
 754                             struct grant_page *pages[],
 755                             int num)
 756 {
 757         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 758         struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 759         unsigned int invcount = 0;
 760         int ret;
 761
 762         while (num) {
 763                 unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
 764
 765                 invcount = xen_blkbk_unmap_prepare(blkif, pages, batch,
 766                                                    unmap, unmap_pages);
 767                 if (invcount) {
 768                         ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
 769                         BUG_ON(ret);
 770                         put_free_pages(blkif, unmap_pages, invcount);
 771                 }
 772                 pages += batch;
 773                 num -= batch;
 774         }
 775 }
 776
 777 static int xen_blkbk_map(struct xen_blkif *blkif,
 778                          struct grant_page *pages[],
 779                          int num, bool ro)
 780 {
 781         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 782         struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 783         struct persistent_gnt *persistent_gnt = NULL;
 784         phys_addr_t addr = 0;
 785         int i, seg_idx, new_map_idx;
 786         int segs_to_map = 0;
 787         int ret = 0;
 788         int last_map = 0, map_until = 0;
 789         int use_persistent_gnts;
 790
 791         use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 792
 793         /*
 794          * Fill out preq.nr_sects with proper amount of sectors, and setup
 795          * assign map[..] with the PFN of the page in our domain with the
 796          * corresponding grant reference for each page.
 797          */
 798 again:
 799         for (i = map_until; i < num; i++) {
 800                 uint32_t flags;
 801
 802                 if (use_persistent_gnts)
 803                         persistent_gnt = get_persistent_gnt(
 804                                 blkif,
 805                                 pages[i]->gref);
 806
 807                 if (persistent_gnt) {
 808                         /*
 809                          * We are using persistent grants and
 810                          * the grant is already mapped
 811                          */
 812                         pages[i]->page = persistent_gnt->page;
 813                         pages[i]->persistent_gnt = persistent_gnt;
 814                 } else {
 815                         if (get_free_page(blkif, &pages[i]->page))
 816                                 goto out_of_memory;
 817                         addr = vaddr(pages[i]->page);
 818                         pages_to_gnt[segs_to_map] = pages[i]->page;
 819                         pages[i]->persistent_gnt = NULL;
 820                         flags = GNTMAP_host_map;
 821                         if (!use_persistent_gnts && ro)
 822                                 flags |= GNTMAP_readonly;
 823                         gnttab_set_map_op(&map[segs_to_map++], addr,
 824                                           flags, pages[i]->gref,
 825                                           blkif->domid);
 826                 }
 827                 map_until = i + 1;
 828                 if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
 829                         break;
 830         }
 831
 832         if (segs_to_map) {
 833                 ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
 834                 BUG_ON(ret);
 835         }
 836
 837         /*
 838          * Now swizzle the MFN in our domain with the MFN from the other domain
 839          * so that when we access vaddr(pending_req,i) it has the contents of
 840          * the page from the other domain.
 841          */
 842         for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
 843                 if (!pages[seg_idx]->persistent_gnt) {
 844                         /* This is a newly mapped grant */
 845                         BUG_ON(new_map_idx >= segs_to_map);
 846                         if (unlikely(map[new_map_idx].status != 0)) {
 847                                 pr_debug("invalid buffer -- could not remap it\n");
 848                                 put_free_pages(blkif, &pages[seg_idx]->page, 1);
 849                                 pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
 850                                 ret |= 1;
 851                                 goto next;
 852                         }
 853                         pages[seg_idx]->handle = map[new_map_idx].handle;
 854                 } else {
 855                         continue;
 856                 }
 857                 if (use_persistent_gnts &&
 858                     blkif->persistent_gnt_c < xen_blkif_max_pgrants) {
 859                         /*
 860                          * We are using persistent grants, the grant is
 861                          * not mapped but we might have room for it.
 862                          */
 863                         persistent_gnt = kmalloc(sizeof(struct persistent_gnt),
 864                                                  GFP_KERNEL);
 865                         if (!persistent_gnt) {
 866                                 /*
 867                                  * If we don't have enough memory to
 868                                  * allocate the persistent_gnt struct
 869                                  * map this grant non-persistenly
 870                                  */
 871                                 goto next;
 872                         }
 873                         persistent_gnt->gnt = map[new_map_idx].ref;
 874                         persistent_gnt->handle = map[new_map_idx].handle;
 875                         persistent_gnt->page = pages[seg_idx]->page;
 876                         if (add_persistent_gnt(blkif,
 877                                                persistent_gnt)) {
 878                                 kfree(persistent_gnt);
 879                                 persistent_gnt = NULL;
 880                                 goto next;
 881                         }
 882                         pages[seg_idx]->persistent_gnt = persistent_gnt;
 883                         pr_debug("grant %u added to the tree of persistent grants, using %u/%u\n",
 884                                  persistent_gnt->gnt, blkif->persistent_gnt_c,
 885                                  xen_blkif_max_pgrants);
 886                         goto next;
 887                 }
 888                 if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
 889                         blkif->vbd.overflow_max_grants = 1;
 890                         pr_debug("domain %u, device %#x is using maximum number of persistent grants\n",
 891                                  blkif->domid, blkif->vbd.handle);
 892                 }
 893                 /*
 894                  * We could not map this grant persistently, so use it as
 895                  * a non-persistent grant.
 896                  */
 897 next:
 898                 new_map_idx++;
 899         }
 900         segs_to_map = 0;
 901         last_map = map_until;
 902         if (map_until != num)
 903                 goto again;
 904
 905         return ret;
 906
 907 out_of_memory:
 908         pr_alert("%s: out of memory\n", __func__);
 909         put_free_pages(blkif, pages_to_gnt, segs_to_map);
 910         return -ENOMEM;
 911 }
 912
 913 static int xen_blkbk_map_seg(struct pending_req *pending_req)
 914 {
 915         int rc;
 916
 917         rc = xen_blkbk_map(pending_req->blkif, pending_req->segments,
 918                            pending_req->nr_pages,
 919                            (pending_req->operation != BLKIF_OP_READ));
 920
 921         return rc;
 922 }
 923
 924 static int xen_blkbk_parse_indirect(struct blkif_request *req,
 925                                     struct pending_req *pending_req,
 926                                     struct seg_buf seg[],
 927                                     struct phys_req *preq)
 928 {
 929         struct grant_page **pages = pending_req->indirect_pages;
 930         struct xen_blkif *blkif = pending_req->blkif;
 931         int indirect_grefs, rc, n, nseg, i;
 932         struct blkif_request_segment *segments = NULL;
 933
 934         nseg = pending_req->nr_pages;
 935         indirect_grefs = INDIRECT_PAGES(nseg);
 936         BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 937
 938         for (i = 0; i < indirect_grefs; i++)
 939                 pages[i]->gref = req->u.indirect.indirect_grefs[i];
 940
 941         rc = xen_blkbk_map(blkif, pages, indirect_grefs, true);
 942         if (rc)
 943                 goto unmap;
 944
 945         for (n = 0, i = 0; n < nseg; n++) {
 946                 if ((n % SEGS_PER_INDIRECT_FRAME) == 0) {
 947                         /* Map indirect segments */
 948                         if (segments)
 949                                 kunmap_atomic(segments);
 950                         segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
 951                 }
 952                 i = n % SEGS_PER_INDIRECT_FRAME;
 953                 pending_req->segments[n]->gref = segments[i].gref;
 954                 seg[n].nsec = segments[i].last_sect -
 955                         segments[i].first_sect + 1;
 956                 seg[n].offset = (segments[i].first_sect << 9);
 957                 if ((segments[i].last_sect >= (PAGE_SIZE >> 9)) ||
 958                     (segments[i].last_sect < segments[i].first_sect)) {
 959                         rc = -EINVAL;
 960                         goto unmap;
 961                 }
 962                 preq->nr_sects += seg[n].nsec;
 963         }
 964
 965 unmap:
 966         if (segments)
 967                 kunmap_atomic(segments);
 968         xen_blkbk_unmap(blkif, pages, indirect_grefs);
 969         return rc;
 970 }
 971
 972 static int dispatch_discard_io(struct xen_blkif *blkif,
 973                                 struct blkif_request *req)
 974 {
 975         int err = 0;
 976         int status = BLKIF_RSP_OKAY;
 977         struct block_device *bdev = blkif->vbd.bdev;
 978         unsigned long secure;
 979         struct phys_req preq;
 980
 981         xen_blkif_get(blkif);
 982
 983         preq.sector_number = req->u.discard.sector_number;
 984         preq.nr_sects      = req->u.discard.nr_sectors;
 985
 986         err = xen_vbd_translate(&preq, blkif, WRITE);
 987         if (err) {
 988                 pr_warn("access denied: DISCARD [%llu->%llu] on dev=%04x\n",
 989                         preq.sector_number,
 990                         preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
 991                 goto fail_response;
 992         }
 993         blkif->st_ds_req++;
 994
 995         secure = (blkif->vbd.discard_secure &&
 996                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
 997                  BLKDEV_DISCARD_SECURE : 0;
 998
 999         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
1000                                    req->u.discard.nr_sectors,
1001                                    GFP_KERNEL, secure);
1002 fail_response:
1003         if (err == -EOPNOTSUPP) {
1004                 pr_debug("discard op failed, not supported\n");
1005                 status = BLKIF_RSP_EOPNOTSUPP;
1006         } else if (err)
1007                 status = BLKIF_RSP_ERROR;
1008
1009         make_response(blkif, req->u.discard.id, req->operation, status);
1010         xen_blkif_put(blkif);
1011         return err;
1012 }
1013
1014 static int dispatch_other_io(struct xen_blkif *blkif,
1015                              struct blkif_request *req,
1016                              struct pending_req *pending_req)
1017 {
1018         free_req(blkif, pending_req);
1019         make_response(blkif, req->u.other.id, req->operation,
1020                       BLKIF_RSP_EOPNOTSUPP);
1021         return -EIO;
1022 }
1023
1024 static void xen_blk_drain_io(struct xen_blkif *blkif)
1025 {
1026         atomic_set(&blkif->drain, 1);
1027         do {
1028                 if (atomic_read(&blkif->inflight) == 0)
1029                         break;
1030                 wait_for_completion_interruptible_timeout(
1031                                 &blkif->drain_complete, HZ);
1032
1033                 if (!atomic_read(&blkif->drain))
1034                         break;
1035         } while (!kthread_should_stop());
1036         atomic_set(&blkif->drain, 0);
1037 }
1038
1039 /*
1040  * Completion callback on the bio's. Called as bh->b_end_io()
1041  */
1042
1043 static void __end_block_io_op(struct pending_req *pending_req, int error)
1044 {
1045         /* An error fails the entire request. */
1046         if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
1047             (error == -EOPNOTSUPP)) {
1048                 pr_debug("flush diskcache op failed, not supported\n");
1049                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
1050                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1051         } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
1052                     (error == -EOPNOTSUPP)) {
1053                 pr_debug("write barrier op failed, not supported\n");
1054                 xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
1055                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1056         } else if (error) {
1057                 pr_debug("Buffer not up-to-date at end of operation,"
1058                          " error=%d\n", error);
1059                 pending_req->status = BLKIF_RSP_ERROR;
1060         }
1061
1062         /*
1063          * If all of the bio's have completed it is time to unmap
1064          * the grant references associated with 'request' and provide
1065          * the proper response on the ring.
1066          */
1067         if (atomic_dec_and_test(&pending_req->pendcnt))
1068                 xen_blkbk_unmap_and_respond(pending_req);
1069 }
1070
1071 /*
1072  * bio callback.
1073  */
1074 static void end_block_io_op(struct bio *bio, int error)
1075 {
1076         __end_block_io_op(bio->bi_private, error);
1077         bio_put(bio);
1078 }
1079
1080
1081
1082 /*
1083  * Function to copy the from the ring buffer the 'struct blkif_request'
1084  * (which has the sectors we want, number of them, grant references, etc),
1085  * and transmute  it to the block API to hand it over to the proper block disk.
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         struct blkif_request req;
1092         struct pending_req *pending_req;
1093         RING_IDX rc, rp;
1094         int more_to_do = 0;
1095
1096         rc = blk_rings->common.req_cons;
1097         rp = blk_rings->common.sring->req_prod;
1098         rmb(); /* Ensure we see queued requests up to 'rp'. */
1099
1100         if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
1101                 rc = blk_rings->common.rsp_prod_pvt;
1102                 pr_warn("Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n",
1103                         rp, rc, rp - rc, blkif->vbd.pdevice);
1104                 return -EACCES;
1105         }
1106         while (rc != rp) {
1107
1108                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1109                         break;
1110
1111                 if (kthread_should_stop()) {
1112                         more_to_do = 1;
1113                         break;
1114                 }
1115
1116                 pending_req = alloc_req(blkif);
1117                 if (NULL == pending_req) {
1118                         blkif->st_oo_req++;
1119                         more_to_do = 1;
1120                         break;
1121                 }
1122
1123                 switch (blkif->blk_protocol) {
1124                 case BLKIF_PROTOCOL_NATIVE:
1125                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1126                         break;
1127                 case BLKIF_PROTOCOL_X86_32:
1128                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1129                         break;
1130                 case BLKIF_PROTOCOL_X86_64:
1131                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1132                         break;
1133                 default:
1134                         BUG();
1135                 }
1136                 blk_rings->common.req_cons = ++rc; /* before make_response() */
1137
1138                 /* Apply all sanity checks to /private copy/ of request. */
1139                 barrier();
1140
1141                 switch (req.operation) {
1142                 case BLKIF_OP_READ:
1143                 case BLKIF_OP_WRITE:
1144                 case BLKIF_OP_WRITE_BARRIER:
1145                 case BLKIF_OP_FLUSH_DISKCACHE:
1146                 case BLKIF_OP_INDIRECT:
1147                         if (dispatch_rw_block_io(blkif, &req, pending_req))
1148                                 goto done;
1149                         break;
1150                 case BLKIF_OP_DISCARD:
1151                         free_req(blkif, pending_req);
1152                         if (dispatch_discard_io(blkif, &req))
1153                                 goto done;
1154                         break;
1155                 default:
1156                         if (dispatch_other_io(blkif, &req, pending_req))
1157                                 goto done;
1158                         break;
1159                 }
1160
1161                 /* Yield point for this unbounded loop. */
1162                 cond_resched();
1163         }
1164 done:
1165         return more_to_do;
1166 }
1167
1168 static int
1169 do_block_io_op(struct xen_blkif *blkif)
1170 {
1171         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1172         int more_to_do;
1173
1174         do {
1175                 more_to_do = __do_block_io_op(blkif);
1176                 if (more_to_do)
1177                         break;
1178
1179                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1180         } while (more_to_do);
1181
1182         return more_to_do;
1183 }
1184 /*
1185  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1186  * and call the 'submit_bio' to pass it to the underlying storage.
1187  */
1188 static int dispatch_rw_block_io(struct xen_blkif *blkif,
1189                                 struct blkif_request *req,
1190                                 struct pending_req *pending_req)
1191 {
1192         struct phys_req preq;
1193         struct seg_buf *seg = pending_req->seg;
1194         unsigned int nseg;
1195         struct bio *bio = NULL;
1196         struct bio **biolist = pending_req->biolist;
1197         int i, nbio = 0;
1198         int operation;
1199         struct blk_plug plug;
1200         bool drain = false;
1201         struct grant_page **pages = pending_req->segments;
1202         unsigned short req_operation;
1203
1204         req_operation = req->operation == BLKIF_OP_INDIRECT ?
1205                         req->u.indirect.indirect_op : req->operation;
1206         if ((req->operation == BLKIF_OP_INDIRECT) &&
1207             (req_operation != BLKIF_OP_READ) &&
1208             (req_operation != BLKIF_OP_WRITE)) {
1209                 pr_debug("Invalid indirect operation (%u)\n", req_operation);
1210                 goto fail_response;
1211         }
1212
1213         switch (req_operation) {
1214         case BLKIF_OP_READ:
1215                 blkif->st_rd_req++;
1216                 operation = READ;
1217                 break;
1218         case BLKIF_OP_WRITE:
1219                 blkif->st_wr_req++;
1220                 operation = WRITE_ODIRECT;
1221                 break;
1222         case BLKIF_OP_WRITE_BARRIER:
1223                 drain = true;
1224         case BLKIF_OP_FLUSH_DISKCACHE:
1225                 blkif->st_f_req++;
1226                 operation = WRITE_FLUSH;
1227                 break;
1228         default:
1229                 operation = 0; /* make gcc happy */
1230                 goto fail_response;
1231                 break;
1232         }
1233
1234         /* Check that the number of segments is sane. */
1235         nseg = req->operation == BLKIF_OP_INDIRECT ?
1236                req->u.indirect.nr_segments : req->u.rw.nr_segments;
1237
1238         if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
1239             unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1240                      (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1241             unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1242                      (nseg > MAX_INDIRECT_SEGMENTS))) {
1243                 pr_debug("Bad number of segments in request (%d)\n", nseg);
1244                 /* Haven't submitted any bio's yet. */
1245                 goto fail_response;
1246         }
1247
1248         preq.nr_sects      = 0;
1249
1250         pending_req->blkif     = blkif;
1251         pending_req->id        = req->u.rw.id;
1252         pending_req->operation = req_operation;
1253         pending_req->status    = BLKIF_RSP_OKAY;
1254         pending_req->nr_pages  = nseg;
1255
1256         if (req->operation != BLKIF_OP_INDIRECT) {
1257                 preq.dev               = req->u.rw.handle;
1258                 preq.sector_number     = req->u.rw.sector_number;
1259                 for (i = 0; i < nseg; i++) {
1260                         pages[i]->gref = req->u.rw.seg[i].gref;
1261                         seg[i].nsec = req->u.rw.seg[i].last_sect -
1262                                 req->u.rw.seg[i].first_sect + 1;
1263                         seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1264                         if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
1265                             (req->u.rw.seg[i].last_sect <
1266                              req->u.rw.seg[i].first_sect))
1267                                 goto fail_response;
1268                         preq.nr_sects += seg[i].nsec;
1269                 }
1270         } else {
1271                 preq.dev               = req->u.indirect.handle;
1272                 preq.sector_number     = req->u.indirect.sector_number;
1273                 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1274                         goto fail_response;
1275         }
1276
1277         if (xen_vbd_translate(&preq, blkif, operation) != 0) {
1278                 pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n",
1279                          operation == READ ? "read" : "write",
1280                          preq.sector_number,
1281                          preq.sector_number + preq.nr_sects,
1282                          blkif->vbd.pdevice);
1283                 goto fail_response;
1284         }
1285
1286         /*
1287          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1288          * is set there.
1289          */
1290         for (i = 0; i < nseg; i++) {
1291                 if (((int)preq.sector_number|(int)seg[i].nsec) &
1292                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1293                         pr_debug("Misaligned I/O request from domain %d\n",
1294                                  blkif->domid);
1295                         goto fail_response;
1296                 }
1297         }
1298
1299         /* Wait on all outstanding I/O's and once that has been completed
1300          * issue the WRITE_FLUSH.
1301          */
1302         if (drain)
1303                 xen_blk_drain_io(pending_req->blkif);
1304
1305         /*
1306          * If we have failed at this point, we need to undo the M2P override,
1307          * set gnttab_set_unmap_op on all of the grant references and perform
1308          * the hypercall to unmap the grants - that is all done in
1309          * xen_blkbk_unmap.
1310          */
1311         if (xen_blkbk_map_seg(pending_req))
1312                 goto fail_flush;
1313
1314         /*
1315          * This corresponding xen_blkif_put is done in __end_block_io_op, or
1316          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1317          */
1318         xen_blkif_get(blkif);
1319         atomic_inc(&blkif->inflight);
1320
1321         for (i = 0; i < nseg; i++) {
1322                 while ((bio == NULL) ||
1323                        (bio_add_page(bio,
1324                                      pages[i]->page,
1325                                      seg[i].nsec << 9,
1326                                      seg[i].offset) == 0)) {
1327
1328                         int nr_iovecs = min_t(int, (nseg-i), BIO_MAX_PAGES);
1329                         bio = bio_alloc(GFP_KERNEL, nr_iovecs);
1330                         if (unlikely(bio == NULL))
1331                                 goto fail_put_bio;
1332
1333                         biolist[nbio++] = bio;
1334                         bio->bi_bdev    = preq.bdev;
1335                         bio->bi_private = pending_req;
1336                         bio->bi_end_io  = end_block_io_op;
1337                         bio->bi_iter.bi_sector  = preq.sector_number;
1338                 }
1339
1340                 preq.sector_number += seg[i].nsec;
1341         }
1342
1343         /* This will be hit if the operation was a flush or discard. */
1344         if (!bio) {
1345                 BUG_ON(operation != WRITE_FLUSH);
1346
1347                 bio = bio_alloc(GFP_KERNEL, 0);
1348                 if (unlikely(bio == NULL))
1349                         goto fail_put_bio;
1350
1351                 biolist[nbio++] = bio;
1352                 bio->bi_bdev    = preq.bdev;
1353                 bio->bi_private = pending_req;
1354                 bio->bi_end_io  = end_block_io_op;
1355         }
1356
1357         atomic_set(&pending_req->pendcnt, nbio);
1358         blk_start_plug(&plug);
1359
1360         for (i = 0; i < nbio; i++)
1361                 submit_bio(operation, biolist[i]);
1362
1363         /* Let the I/Os go.. */
1364         blk_finish_plug(&plug);
1365
1366         if (operation == READ)
1367                 blkif->st_rd_sect += preq.nr_sects;
1368         else if (operation & WRITE)
1369                 blkif->st_wr_sect += preq.nr_sects;
1370
1371         return 0;
1372
1373  fail_flush:
1374         xen_blkbk_unmap(blkif, pending_req->segments,
1375                         pending_req->nr_pages);
1376  fail_response:
1377         /* Haven't submitted any bio's yet. */
1378         make_response(blkif, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1379         free_req(blkif, pending_req);
1380         msleep(1); /* back off a bit */
1381         return -EIO;
1382
1383  fail_put_bio:
1384         for (i = 0; i < nbio; i++)
1385                 bio_put(biolist[i]);
1386         atomic_set(&pending_req->pendcnt, 1);
1387         __end_block_io_op(pending_req, -EINVAL);
1388         msleep(1); /* back off a bit */
1389         return -EIO;
1390 }
1391
1392
1393
1394 /*
1395  * Put a response on the ring on how the operation fared.
1396  */
1397 static void make_response(struct xen_blkif *blkif, u64 id,
1398                           unsigned short op, int st)
1399 {
1400         struct blkif_response  resp;
1401         unsigned long     flags;
1402         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1403         int notify;
1404
1405         resp.id        = id;
1406         resp.operation = op;
1407         resp.status    = st;
1408
1409         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
1410         /* Place on the response ring for the relevant domain. */
1411         switch (blkif->blk_protocol) {
1412         case BLKIF_PROTOCOL_NATIVE:
1413                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
1414                        &resp, sizeof(resp));
1415                 break;
1416         case BLKIF_PROTOCOL_X86_32:
1417                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
1418                        &resp, sizeof(resp));
1419                 break;
1420         case BLKIF_PROTOCOL_X86_64:
1421                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
1422                        &resp, sizeof(resp));
1423                 break;
1424         default:
1425                 BUG();
1426         }
1427         blk_rings->common.rsp_prod_pvt++;
1428         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1429         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
1430         if (notify)
1431                 notify_remote_via_irq(blkif->irq);
1432 }
1433
1434 static int __init xen_blkif_init(void)
1435 {
1436         int rc = 0;
1437
1438         if (!xen_domain())
1439                 return -ENODEV;
1440
1441         rc = xen_blkif_interface_init();
1442         if (rc)
1443                 goto failed_init;
1444
1445         rc = xen_blkif_xenbus_init();
1446         if (rc)
1447                 goto failed_init;
1448
1449  failed_init:
1450         return rc;
1451 }
1452
1453 module_init(xen_blkif_init);
1454
1455 MODULE_LICENSE("Dual BSD/GPL");
1456 MODULE_ALIAS("xen-backend:vbd");