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 max_buffer_pages = 1024;
  66 module_param_named(max_buffer_pages, 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 max_pgrants = 1056;
  82 module_param_named(max_persistent_grants, max_pgrants, int, 0644);
  83 MODULE_PARM_DESC(max_persistent_grants,
  84                  "Maximum number of grants to map persistently");
  85
  86 /*
  87  * How long a persistent grant is allowed to remain allocated without being in
  88  * use. The time is in seconds, 0 means indefinitely long.
  89  */
  90
  91 static unsigned int pgrant_timeout = 60;
  92 module_param_named(persistent_grant_unused_seconds, pgrant_timeout,
  93                    uint, 0644);
  94 MODULE_PARM_DESC(persistent_grant_unused_seconds,
  95                  "Time in seconds an unused persistent grant is allowed to "
  96                  "remain allocated. Default is 60, 0 means unlimited.");
  97
  98 /*
  99  * Maximum number of rings/queues blkback supports, allow as many queues as there
 100  * are CPUs if user has not specified a value.
 101  */
 102 unsigned int xenblk_max_queues;
 103 module_param_named(max_queues, xenblk_max_queues, uint, 0644);
 104 MODULE_PARM_DESC(max_queues,
 105                  "Maximum number of hardware queues per virtual disk." \
 106                  "By default it is the number of online CPUs.");
 107
 108 /*
 109  * Maximum order of pages to be used for the shared ring between front and
 110  * backend, 4KB page granularity is used.
 111  */
 112 unsigned int xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
 113 module_param_named(max_ring_page_order, xen_blkif_max_ring_order, int, 0444);
 114 MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the shared ring");
 115 /*
 116  * The LRU mechanism to clean the lists of persistent grants needs to
 117  * be executed periodically. The time interval between consecutive executions
 118  * of the purge mechanism is set in ms.
 119  */
 120 #define LRU_INTERVAL 100
 121
 122 /*
 123  * When the persistent grants list is full we will remove unused grants
 124  * from the list. The percent number of grants to be removed at each LRU
 125  * execution.
 126  */
 127 #define LRU_PERCENT_CLEAN 5
 128
 129 /* Run-time switchable: /sys/module/blkback/parameters/ */
 130 static unsigned int log_stats;
 131 module_param(log_stats, int, 0644);
 132
 133 #define BLKBACK_INVALID_HANDLE (~0)
 134
 135 static inline bool persistent_gnt_timeout(struct persistent_gnt *persistent_gnt)
 136 {
 137         return pgrant_timeout && (jiffies - persistent_gnt->last_used >=
 138                         HZ * pgrant_timeout);
 139 }
 140
 141 #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
 142
 143 static int do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags);
 144 static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 145                                 struct blkif_request *req,
 146                                 struct pending_req *pending_req);
 147 static void make_response(struct xen_blkif_ring *ring, u64 id,
 148                           unsigned short op, int st);
 149
 150 #define foreach_grant_safe(pos, n, rbtree, node) \
 151         for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node), \
 152              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL; \
 153              &(pos)->node != NULL; \
 154              (pos) = container_of(n, typeof(*(pos)), node), \
 155              (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL)
 156
 157
 158 /*
 159  * We don't need locking around the persistent grant helpers
 160  * because blkback uses a single-thread for each backend, so we
 161  * can be sure that this functions will never be called recursively.
 162  *
 163  * The only exception to that is put_persistent_grant, that can be called
 164  * from interrupt context (by xen_blkbk_unmap), so we have to use atomic
 165  * bit operations to modify the flags of a persistent grant and to count
 166  * the number of used grants.
 167  */
 168 static int add_persistent_gnt(struct xen_blkif_ring *ring,
 169                                struct persistent_gnt *persistent_gnt)
 170 {
 171         struct rb_node **new = NULL, *parent = NULL;
 172         struct persistent_gnt *this;
 173         struct xen_blkif *blkif = ring->blkif;
 174
 175         if (ring->persistent_gnt_c >= max_pgrants) {
 176                 if (!blkif->vbd.overflow_max_grants)
 177                         blkif->vbd.overflow_max_grants = 1;
 178                 return -EBUSY;
 179         }
 180         /* Figure out where to put new node */
 181         new = &ring->persistent_gnts.rb_node;
 182         while (*new) {
 183                 this = container_of(*new, struct persistent_gnt, node);
 184
 185                 parent = *new;
 186                 if (persistent_gnt->gnt < this->gnt)
 187                         new = &((*new)->rb_left);
 188                 else if (persistent_gnt->gnt > this->gnt)
 189                         new = &((*new)->rb_right);
 190                 else {
 191                         pr_alert_ratelimited("trying to add a gref that's already in the tree\n");
 192                         return -EINVAL;
 193                 }
 194         }
 195
 196         persistent_gnt->active = true;
 197         /* Add new node and rebalance tree. */
 198         rb_link_node(&(persistent_gnt->node), parent, new);
 199         rb_insert_color(&(persistent_gnt->node), &ring->persistent_gnts);
 200         ring->persistent_gnt_c++;
 201         atomic_inc(&ring->persistent_gnt_in_use);
 202         return 0;
 203 }
 204
 205 static struct persistent_gnt *get_persistent_gnt(struct xen_blkif_ring *ring,
 206                                                  grant_ref_t gref)
 207 {
 208         struct persistent_gnt *data;
 209         struct rb_node *node = NULL;
 210
 211         node = ring->persistent_gnts.rb_node;
 212         while (node) {
 213                 data = container_of(node, struct persistent_gnt, node);
 214
 215                 if (gref < data->gnt)
 216                         node = node->rb_left;
 217                 else if (gref > data->gnt)
 218                         node = node->rb_right;
 219                 else {
 220                         if (data->active) {
 221                                 pr_alert_ratelimited("requesting a grant already in use\n");
 222                                 return NULL;
 223                         }
 224                         data->active = true;
 225                         atomic_inc(&ring->persistent_gnt_in_use);
 226                         return data;
 227                 }
 228         }
 229         return NULL;
 230 }
 231
 232 static void put_persistent_gnt(struct xen_blkif_ring *ring,
 233                                struct persistent_gnt *persistent_gnt)
 234 {
 235         if (!persistent_gnt->active)
 236                 pr_alert_ratelimited("freeing a grant already unused\n");
 237         persistent_gnt->last_used = jiffies;
 238         persistent_gnt->active = false;
 239         atomic_dec(&ring->persistent_gnt_in_use);
 240 }
 241
 242 static void free_persistent_gnts(struct xen_blkif_ring *ring, struct rb_root *root,
 243                                  unsigned int num)
 244 {
 245         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 246         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 247         struct persistent_gnt *persistent_gnt;
 248         struct rb_node *n;
 249         int segs_to_unmap = 0;
 250         struct gntab_unmap_queue_data unmap_data;
 251
 252         unmap_data.pages = pages;
 253         unmap_data.unmap_ops = unmap;
 254         unmap_data.kunmap_ops = NULL;
 255
 256         foreach_grant_safe(persistent_gnt, n, root, node) {
 257                 BUG_ON(persistent_gnt->handle ==
 258                         BLKBACK_INVALID_HANDLE);
 259                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 260                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 261                                 persistent_gnt->page)),
 262                         GNTMAP_host_map,
 263                         persistent_gnt->handle);
 264
 265                 pages[segs_to_unmap] = persistent_gnt->page;
 266
 267                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 268                         !rb_next(&persistent_gnt->node)) {
 269
 270                         unmap_data.count = segs_to_unmap;
 271                         BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 272
 273                         gnttab_page_cache_put(&ring->free_pages, pages,
 274                                               segs_to_unmap);
 275                         segs_to_unmap = 0;
 276                 }
 277
 278                 rb_erase(&persistent_gnt->node, root);
 279                 kfree(persistent_gnt);
 280                 num--;
 281         }
 282         BUG_ON(num != 0);
 283 }
 284
 285 void xen_blkbk_unmap_purged_grants(struct work_struct *work)
 286 {
 287         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 288         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 289         struct persistent_gnt *persistent_gnt;
 290         int segs_to_unmap = 0;
 291         struct xen_blkif_ring *ring = container_of(work, typeof(*ring), persistent_purge_work);
 292         struct gntab_unmap_queue_data unmap_data;
 293
 294         unmap_data.pages = pages;
 295         unmap_data.unmap_ops = unmap;
 296         unmap_data.kunmap_ops = NULL;
 297
 298         while(!list_empty(&ring->persistent_purge_list)) {
 299                 persistent_gnt = list_first_entry(&ring->persistent_purge_list,
 300                                                   struct persistent_gnt,
 301                                                   remove_node);
 302                 list_del(&persistent_gnt->remove_node);
 303
 304                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 305                         vaddr(persistent_gnt->page),
 306                         GNTMAP_host_map,
 307                         persistent_gnt->handle);
 308
 309                 pages[segs_to_unmap] = persistent_gnt->page;
 310
 311                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 312                         unmap_data.count = segs_to_unmap;
 313                         BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 314                         gnttab_page_cache_put(&ring->free_pages, pages,
 315                                               segs_to_unmap);
 316                         segs_to_unmap = 0;
 317                 }
 318                 kfree(persistent_gnt);
 319         }
 320         if (segs_to_unmap > 0) {
 321                 unmap_data.count = segs_to_unmap;
 322                 BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 323                 gnttab_page_cache_put(&ring->free_pages, pages, segs_to_unmap);
 324         }
 325 }
 326
 327 static void purge_persistent_gnt(struct xen_blkif_ring *ring)
 328 {
 329         struct persistent_gnt *persistent_gnt;
 330         struct rb_node *n;
 331         unsigned int num_clean, total;
 332         bool scan_used = false;
 333         struct rb_root *root;
 334
 335         if (work_busy(&ring->persistent_purge_work)) {
 336                 pr_alert_ratelimited("Scheduled work from previous purge is still busy, cannot purge list\n");
 337                 goto out;
 338         }
 339
 340         if (ring->persistent_gnt_c < max_pgrants ||
 341             (ring->persistent_gnt_c == max_pgrants &&
 342             !ring->blkif->vbd.overflow_max_grants)) {
 343                 num_clean = 0;
 344         } else {
 345                 num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN;
 346                 num_clean = ring->persistent_gnt_c - max_pgrants + num_clean;
 347                 num_clean = min(ring->persistent_gnt_c, num_clean);
 348                 pr_debug("Going to purge at least %u persistent grants\n",
 349                          num_clean);
 350         }
 351
 352         /*
 353          * At this point, we can assure that there will be no calls
 354          * to get_persistent_grant (because we are executing this code from
 355          * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
 356          * which means that the number of currently used grants will go down,
 357          * but never up, so we will always be able to remove the requested
 358          * number of grants.
 359          */
 360
 361         total = 0;
 362
 363         BUG_ON(!list_empty(&ring->persistent_purge_list));
 364         root = &ring->persistent_gnts;
 365 purge_list:
 366         foreach_grant_safe(persistent_gnt, n, root, node) {
 367                 BUG_ON(persistent_gnt->handle ==
 368                         BLKBACK_INVALID_HANDLE);
 369
 370                 if (persistent_gnt->active)
 371                         continue;
 372                 if (!scan_used && !persistent_gnt_timeout(persistent_gnt))
 373                         continue;
 374                 if (scan_used && total >= num_clean)
 375                         continue;
 376
 377                 rb_erase(&persistent_gnt->node, root);
 378                 list_add(&persistent_gnt->remove_node,
 379                          &ring->persistent_purge_list);
 380                 total++;
 381         }
 382         /*
 383          * Check whether we also need to start cleaning
 384          * grants that were used since last purge in order to cope
 385          * with the requested num
 386          */
 387         if (!scan_used && total < num_clean) {
 388                 pr_debug("Still missing %u purged frames\n", num_clean - total);
 389                 scan_used = true;
 390                 goto purge_list;
 391         }
 392
 393         if (total) {
 394                 ring->persistent_gnt_c -= total;
 395                 ring->blkif->vbd.overflow_max_grants = 0;
 396
 397                 /* We can defer this work */
 398                 schedule_work(&ring->persistent_purge_work);
 399                 pr_debug("Purged %u/%u\n", num_clean, total);
 400         }
 401
 402 out:
 403         return;
 404 }
 405
 406 /*
 407  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 408  */
 409 static struct pending_req *alloc_req(struct xen_blkif_ring *ring)
 410 {
 411         struct pending_req *req = NULL;
 412         unsigned long flags;
 413
 414         spin_lock_irqsave(&ring->pending_free_lock, flags);
 415         if (!list_empty(&ring->pending_free)) {
 416                 req = list_entry(ring->pending_free.next, struct pending_req,
 417                                  free_list);
 418                 list_del(&req->free_list);
 419         }
 420         spin_unlock_irqrestore(&ring->pending_free_lock, flags);
 421         return req;
 422 }
 423
 424 /*
 425  * Return the 'pending_req' structure back to the freepool. We also
 426  * wake up the thread if it was waiting for a free page.
 427  */
 428 static void free_req(struct xen_blkif_ring *ring, struct pending_req *req)
 429 {
 430         unsigned long flags;
 431         int was_empty;
 432
 433         spin_lock_irqsave(&ring->pending_free_lock, flags);
 434         was_empty = list_empty(&ring->pending_free);
 435         list_add(&req->free_list, &ring->pending_free);
 436         spin_unlock_irqrestore(&ring->pending_free_lock, flags);
 437         if (was_empty)
 438                 wake_up(&ring->pending_free_wq);
 439 }
 440
 441 /*
 442  * Routines for managing virtual block devices (vbds).
 443  */
 444 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 445                              int operation)
 446 {
 447         struct xen_vbd *vbd = &blkif->vbd;
 448         int rc = -EACCES;
 449
 450         if ((operation != REQ_OP_READ) && vbd->readonly)
 451                 goto out;
 452
 453         if (likely(req->nr_sects)) {
 454                 blkif_sector_t end = req->sector_number + req->nr_sects;
 455
 456                 if (unlikely(end < req->sector_number))
 457                         goto out;
 458                 if (unlikely(end > vbd_sz(vbd)))
 459                         goto out;
 460         }
 461
 462         req->dev  = vbd->pdevice;
 463         req->bdev = vbd->bdev;
 464         rc = 0;
 465
 466  out:
 467         return rc;
 468 }
 469
 470 static void xen_vbd_resize(struct xen_blkif *blkif)
 471 {
 472         struct xen_vbd *vbd = &blkif->vbd;
 473         struct xenbus_transaction xbt;
 474         int err;
 475         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 476         unsigned long long new_size = vbd_sz(vbd);
 477
 478         pr_info("VBD Resize: Domid: %d, Device: (%d, %d)\n",
 479                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 480         pr_info("VBD Resize: new size %llu\n", new_size);
 481         vbd->size = new_size;
 482 again:
 483         err = xenbus_transaction_start(&xbt);
 484         if (err) {
 485                 pr_warn("Error starting transaction\n");
 486                 return;
 487         }
 488         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 489                             (unsigned long long)vbd_sz(vbd));
 490         if (err) {
 491                 pr_warn("Error writing new size\n");
 492                 goto abort;
 493         }
 494         /*
 495          * Write the current state; we will use this to synchronize
 496          * the front-end. If the current state is "connected" the
 497          * front-end will get the new size information online.
 498          */
 499         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 500         if (err) {
 501                 pr_warn("Error writing the state\n");
 502                 goto abort;
 503         }
 504
 505         err = xenbus_transaction_end(xbt, 0);
 506         if (err == -EAGAIN)
 507                 goto again;
 508         if (err)
 509                 pr_warn("Error ending transaction\n");
 510         return;
 511 abort:
 512         xenbus_transaction_end(xbt, 1);
 513 }
 514
 515 /*
 516  * Notification from the guest OS.
 517  */
 518 static void blkif_notify_work(struct xen_blkif_ring *ring)
 519 {
 520         ring->waiting_reqs = 1;
 521         wake_up(&ring->wq);
 522 }
 523
 524 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 525 {
 526         blkif_notify_work(dev_id);
 527         return IRQ_HANDLED;
 528 }
 529
 530 /*
 531  * SCHEDULER FUNCTIONS
 532  */
 533
 534 static void print_stats(struct xen_blkif_ring *ring)
 535 {
 536         pr_info("(%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
 537                  "  |  ds %4llu | pg: %4u/%4d\n",
 538                  current->comm, ring->st_oo_req,
 539                  ring->st_rd_req, ring->st_wr_req,
 540                  ring->st_f_req, ring->st_ds_req,
 541                  ring->persistent_gnt_c, max_pgrants);
 542         ring->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 543         ring->st_rd_req = 0;
 544         ring->st_wr_req = 0;
 545         ring->st_oo_req = 0;
 546         ring->st_ds_req = 0;
 547 }
 548
 549 int xen_blkif_schedule(void *arg)
 550 {
 551         struct xen_blkif_ring *ring = arg;
 552         struct xen_blkif *blkif = ring->blkif;
 553         struct xen_vbd *vbd = &blkif->vbd;
 554         unsigned long timeout;
 555         int ret;
 556         bool do_eoi;
 557         unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
 558
 559         set_freezable();
 560         while (!kthread_should_stop()) {
 561                 if (try_to_freeze())
 562                         continue;
 563                 if (unlikely(vbd->size != vbd_sz(vbd)))
 564                         xen_vbd_resize(blkif);
 565
 566                 timeout = msecs_to_jiffies(LRU_INTERVAL);
 567
 568                 timeout = wait_event_interruptible_timeout(
 569                         ring->wq,
 570                         ring->waiting_reqs || kthread_should_stop(),
 571                         timeout);
 572                 if (timeout == 0)
 573                         goto purge_gnt_list;
 574                 timeout = wait_event_interruptible_timeout(
 575                         ring->pending_free_wq,
 576                         !list_empty(&ring->pending_free) ||
 577                         kthread_should_stop(),
 578                         timeout);
 579                 if (timeout == 0)
 580                         goto purge_gnt_list;
 581
 582                 do_eoi = ring->waiting_reqs;
 583
 584                 ring->waiting_reqs = 0;
 585                 smp_mb(); /* clear flag *before* checking for work */
 586
 587                 ret = do_block_io_op(ring, &eoi_flags);
 588                 if (ret > 0)
 589                         ring->waiting_reqs = 1;
 590                 if (ret == -EACCES)
 591                         wait_event_interruptible(ring->shutdown_wq,
 592                                                  kthread_should_stop());
 593
 594                 if (do_eoi && !ring->waiting_reqs) {
 595                         xen_irq_lateeoi(ring->irq, eoi_flags);
 596                         eoi_flags |= XEN_EOI_FLAG_SPURIOUS;
 597                 }
 598
 599 purge_gnt_list:
 600                 if (blkif->vbd.feature_gnt_persistent &&
 601                     time_after(jiffies, ring->next_lru)) {
 602                         purge_persistent_gnt(ring);
 603                         ring->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
 604                 }
 605
 606                 /* Shrink the free pages pool if it is too large. */
 607                 if (time_before(jiffies, blkif->buffer_squeeze_end))
 608                         gnttab_page_cache_shrink(&ring->free_pages, 0);
 609                 else
 610                         gnttab_page_cache_shrink(&ring->free_pages,
 611                                                  max_buffer_pages);
 612
 613                 if (log_stats && time_after(jiffies, ring->st_print))
 614                         print_stats(ring);
 615         }
 616
 617         /* Drain pending purge work */
 618         flush_work(&ring->persistent_purge_work);
 619
 620         if (log_stats)
 621                 print_stats(ring);
 622
 623         ring->xenblkd = NULL;
 624
 625         return 0;
 626 }
 627
 628 /*
 629  * Remove persistent grants and empty the pool of free pages
 630  */
 631 void xen_blkbk_free_caches(struct xen_blkif_ring *ring)
 632 {
 633         /* Free all persistent grant pages */
 634         if (!RB_EMPTY_ROOT(&ring->persistent_gnts))
 635                 free_persistent_gnts(ring, &ring->persistent_gnts,
 636                         ring->persistent_gnt_c);
 637
 638         BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
 639         ring->persistent_gnt_c = 0;
 640
 641         /* Since we are shutting down remove all pages from the buffer */
 642         gnttab_page_cache_shrink(&ring->free_pages, 0 /* All */);
 643 }
 644
 645 static unsigned int xen_blkbk_unmap_prepare(
 646         struct xen_blkif_ring *ring,
 647         struct grant_page **pages,
 648         unsigned int num,
 649         struct gnttab_unmap_grant_ref *unmap_ops,
 650         struct page **unmap_pages)
 651 {
 652         unsigned int i, invcount = 0;
 653
 654         for (i = 0; i < num; i++) {
 655                 if (pages[i]->persistent_gnt != NULL) {
 656                         put_persistent_gnt(ring, pages[i]->persistent_gnt);
 657                         continue;
 658                 }
 659                 if (pages[i]->handle == BLKBACK_INVALID_HANDLE)
 660                         continue;
 661                 unmap_pages[invcount] = pages[i]->page;
 662                 gnttab_set_unmap_op(&unmap_ops[invcount], vaddr(pages[i]->page),
 663                                     GNTMAP_host_map, pages[i]->handle);
 664                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
 665                 invcount++;
 666         }
 667
 668         return invcount;
 669 }
 670
 671 static void xen_blkbk_unmap_and_respond_callback(int result, struct gntab_unmap_queue_data *data)
 672 {
 673         struct pending_req *pending_req = (struct pending_req *)(data->data);
 674         struct xen_blkif_ring *ring = pending_req->ring;
 675         struct xen_blkif *blkif = ring->blkif;
 676
 677         /* BUG_ON used to reproduce existing behaviour,
 678            but is this the best way to deal with this? */
 679         BUG_ON(result);
 680
 681         gnttab_page_cache_put(&ring->free_pages, data->pages, data->count);
 682         make_response(ring, pending_req->id,
 683                       pending_req->operation, pending_req->status);
 684         free_req(ring, pending_req);
 685         /*
 686          * Make sure the request is freed before releasing blkif,
 687          * or there could be a race between free_req and the
 688          * cleanup done in xen_blkif_free during shutdown.
 689          *
 690          * NB: The fact that we might try to wake up pending_free_wq
 691          * before drain_complete (in case there's a drain going on)
 692          * it's not a problem with our current implementation
 693          * because we can assure there's no thread waiting on
 694          * pending_free_wq if there's a drain going on, but it has
 695          * to be taken into account if the current model is changed.
 696          */
 697         if (atomic_dec_and_test(&ring->inflight) && atomic_read(&blkif->drain)) {
 698                 complete(&blkif->drain_complete);
 699         }
 700         xen_blkif_put(blkif);
 701 }
 702
 703 static void xen_blkbk_unmap_and_respond(struct pending_req *req)
 704 {
 705         struct gntab_unmap_queue_data* work = &req->gnttab_unmap_data;
 706         struct xen_blkif_ring *ring = req->ring;
 707         struct grant_page **pages = req->segments;
 708         unsigned int invcount;
 709
 710         invcount = xen_blkbk_unmap_prepare(ring, pages, req->nr_segs,
 711                                            req->unmap, req->unmap_pages);
 712
 713         work->data = req;
 714         work->done = xen_blkbk_unmap_and_respond_callback;
 715         work->unmap_ops = req->unmap;
 716         work->kunmap_ops = NULL;
 717         work->pages = req->unmap_pages;
 718         work->count = invcount;
 719
 720         gnttab_unmap_refs_async(&req->gnttab_unmap_data);
 721 }
 722
 723
 724 /*
 725  * Unmap the grant references.
 726  *
 727  * This could accumulate ops up to the batch size to reduce the number
 728  * of hypercalls, but since this is only used in error paths there's
 729  * no real need.
 730  */
 731 static void xen_blkbk_unmap(struct xen_blkif_ring *ring,
 732                             struct grant_page *pages[],
 733                             int num)
 734 {
 735         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 736         struct page *unmap_pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 737         unsigned int invcount = 0;
 738         int ret;
 739
 740         while (num) {
 741                 unsigned int batch = min(num, BLKIF_MAX_SEGMENTS_PER_REQUEST);
 742
 743                 invcount = xen_blkbk_unmap_prepare(ring, pages, batch,
 744                                                    unmap, unmap_pages);
 745                 if (invcount) {
 746                         ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount);
 747                         BUG_ON(ret);
 748                         gnttab_page_cache_put(&ring->free_pages, unmap_pages,
 749                                               invcount);
 750                 }
 751                 pages += batch;
 752                 num -= batch;
 753         }
 754 }
 755
 756 static int xen_blkbk_map(struct xen_blkif_ring *ring,
 757                          struct grant_page *pages[],
 758                          int num, bool ro)
 759 {
 760         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 761         struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 762         struct persistent_gnt *persistent_gnt = NULL;
 763         phys_addr_t addr = 0;
 764         int i, seg_idx, new_map_idx;
 765         int segs_to_map = 0;
 766         int ret = 0;
 767         int last_map = 0, map_until = 0;
 768         int use_persistent_gnts;
 769         struct xen_blkif *blkif = ring->blkif;
 770
 771         use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 772
 773         /*
 774          * Fill out preq.nr_sects with proper amount of sectors, and setup
 775          * assign map[..] with the PFN of the page in our domain with the
 776          * corresponding grant reference for each page.
 777          */
 778 again:
 779         for (i = map_until; i < num; i++) {
 780                 uint32_t flags;
 781
 782                 if (use_persistent_gnts) {
 783                         persistent_gnt = get_persistent_gnt(
 784                                 ring,
 785                                 pages[i]->gref);
 786                 }
 787
 788                 if (persistent_gnt) {
 789                         /*
 790                          * We are using persistent grants and
 791                          * the grant is already mapped
 792                          */
 793                         pages[i]->page = persistent_gnt->page;
 794                         pages[i]->persistent_gnt = persistent_gnt;
 795                 } else {
 796                         if (gnttab_page_cache_get(&ring->free_pages,
 797                                                   &pages[i]->page)) {
 798                                 gnttab_page_cache_put(&ring->free_pages,
 799                                                       pages_to_gnt,
 800                                                       segs_to_map);
 801                                 ret = -ENOMEM;
 802                                 goto out;
 803                         }
 804                         addr = vaddr(pages[i]->page);
 805                         pages_to_gnt[segs_to_map] = pages[i]->page;
 806                         pages[i]->persistent_gnt = NULL;
 807                         flags = GNTMAP_host_map;
 808                         if (!use_persistent_gnts && ro)
 809                                 flags |= GNTMAP_readonly;
 810                         gnttab_set_map_op(&map[segs_to_map++], addr,
 811                                           flags, pages[i]->gref,
 812                                           blkif->domid);
 813                 }
 814                 map_until = i + 1;
 815                 if (segs_to_map == BLKIF_MAX_SEGMENTS_PER_REQUEST)
 816                         break;
 817         }
 818
 819         if (segs_to_map)
 820                 ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
 821
 822         /*
 823          * Now swizzle the MFN in our domain with the MFN from the other domain
 824          * so that when we access vaddr(pending_req,i) it has the contents of
 825          * the page from the other domain.
 826          */
 827         for (seg_idx = last_map, new_map_idx = 0; seg_idx < map_until; seg_idx++) {
 828                 if (!pages[seg_idx]->persistent_gnt) {
 829                         /* This is a newly mapped grant */
 830                         BUG_ON(new_map_idx >= segs_to_map);
 831                         if (unlikely(map[new_map_idx].status != 0)) {
 832                                 pr_debug("invalid buffer -- could not remap it\n");
 833                                 gnttab_page_cache_put(&ring->free_pages,
 834                                                       &pages[seg_idx]->page, 1);
 835                                 pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
 836                                 ret |= !ret;
 837                                 goto next;
 838                         }
 839                         pages[seg_idx]->handle = map[new_map_idx].handle;
 840                 } else {
 841                         continue;
 842                 }
 843                 if (use_persistent_gnts &&
 844                     ring->persistent_gnt_c < max_pgrants) {
 845                         /*
 846                          * We are using persistent grants, the grant is
 847                          * not mapped but we might have room for it.
 848                          */
 849                         persistent_gnt = kmalloc(sizeof(struct persistent_gnt),
 850                                                  GFP_KERNEL);
 851                         if (!persistent_gnt) {
 852                                 /*
 853                                  * If we don't have enough memory to
 854                                  * allocate the persistent_gnt struct
 855                                  * map this grant non-persistenly
 856                                  */
 857                                 goto next;
 858                         }
 859                         persistent_gnt->gnt = map[new_map_idx].ref;
 860                         persistent_gnt->handle = map[new_map_idx].handle;
 861                         persistent_gnt->page = pages[seg_idx]->page;
 862                         if (add_persistent_gnt(ring,
 863                                                persistent_gnt)) {
 864                                 kfree(persistent_gnt);
 865                                 persistent_gnt = NULL;
 866                                 goto next;
 867                         }
 868                         pages[seg_idx]->persistent_gnt = persistent_gnt;
 869                         pr_debug("grant %u added to the tree of persistent grants, using %u/%u\n",
 870                                  persistent_gnt->gnt, ring->persistent_gnt_c,
 871                                  max_pgrants);
 872                         goto next;
 873                 }
 874                 if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) {
 875                         blkif->vbd.overflow_max_grants = 1;
 876                         pr_debug("domain %u, device %#x is using maximum number of persistent grants\n",
 877                                  blkif->domid, blkif->vbd.handle);
 878                 }
 879                 /*
 880                  * We could not map this grant persistently, so use it as
 881                  * a non-persistent grant.
 882                  */
 883 next:
 884                 new_map_idx++;
 885         }
 886         segs_to_map = 0;
 887         last_map = map_until;
 888         if (!ret && map_until != num)
 889                 goto again;
 890
 891 out:
 892         for (i = last_map; i < num; i++) {
 893                 /* Don't zap current batch's valid persistent grants. */
 894                 if(i >= last_map + segs_to_map)
 895                         pages[i]->persistent_gnt = NULL;
 896                 pages[i]->handle = BLKBACK_INVALID_HANDLE;
 897         }
 898
 899         return ret;
 900 }
 901
 902 static int xen_blkbk_map_seg(struct pending_req *pending_req)
 903 {
 904         int rc;
 905
 906         rc = xen_blkbk_map(pending_req->ring, pending_req->segments,
 907                            pending_req->nr_segs,
 908                            (pending_req->operation != BLKIF_OP_READ));
 909
 910         return rc;
 911 }
 912
 913 static int xen_blkbk_parse_indirect(struct blkif_request *req,
 914                                     struct pending_req *pending_req,
 915                                     struct seg_buf seg[],
 916                                     struct phys_req *preq)
 917 {
 918         struct grant_page **pages = pending_req->indirect_pages;
 919         struct xen_blkif_ring *ring = pending_req->ring;
 920         int indirect_grefs, rc, n, nseg, i;
 921         struct blkif_request_segment *segments = NULL;
 922
 923         nseg = pending_req->nr_segs;
 924         indirect_grefs = INDIRECT_PAGES(nseg);
 925         BUG_ON(indirect_grefs > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
 926
 927         for (i = 0; i < indirect_grefs; i++)
 928                 pages[i]->gref = req->u.indirect.indirect_grefs[i];
 929
 930         rc = xen_blkbk_map(ring, pages, indirect_grefs, true);
 931         if (rc)
 932                 goto unmap;
 933
 934         for (n = 0, i = 0; n < nseg; n++) {
 935                 uint8_t first_sect, last_sect;
 936
 937                 if ((n % SEGS_PER_INDIRECT_FRAME) == 0) {
 938                         /* Map indirect segments */
 939                         if (segments)
 940                                 kunmap_atomic(segments);
 941                         segments = kmap_atomic(pages[n/SEGS_PER_INDIRECT_FRAME]->page);
 942                 }
 943                 i = n % SEGS_PER_INDIRECT_FRAME;
 944
 945                 pending_req->segments[n]->gref = segments[i].gref;
 946
 947                 first_sect = READ_ONCE(segments[i].first_sect);
 948                 last_sect = READ_ONCE(segments[i].last_sect);
 949                 if (last_sect >= (XEN_PAGE_SIZE >> 9) || last_sect < first_sect) {
 950                         rc = -EINVAL;
 951                         goto unmap;
 952                 }
 953
 954                 seg[n].nsec = last_sect - first_sect + 1;
 955                 seg[n].offset = first_sect << 9;
 956                 preq->nr_sects += seg[n].nsec;
 957         }
 958
 959 unmap:
 960         if (segments)
 961                 kunmap_atomic(segments);
 962         xen_blkbk_unmap(ring, pages, indirect_grefs);
 963         return rc;
 964 }
 965
 966 static int dispatch_discard_io(struct xen_blkif_ring *ring,
 967                                 struct blkif_request *req)
 968 {
 969         int err = 0;
 970         int status = BLKIF_RSP_OKAY;
 971         struct xen_blkif *blkif = ring->blkif;
 972         struct block_device *bdev = blkif->vbd.bdev;
 973         unsigned long secure;
 974         struct phys_req preq;
 975
 976         xen_blkif_get(blkif);
 977
 978         preq.sector_number = req->u.discard.sector_number;
 979         preq.nr_sects      = req->u.discard.nr_sectors;
 980
 981         err = xen_vbd_translate(&preq, blkif, REQ_OP_WRITE);
 982         if (err) {
 983                 pr_warn("access denied: DISCARD [%llu->%llu] on dev=%04x\n",
 984                         preq.sector_number,
 985                         preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
 986                 goto fail_response;
 987         }
 988         ring->st_ds_req++;
 989
 990         secure = (blkif->vbd.discard_secure &&
 991                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
 992                  BLKDEV_DISCARD_SECURE : 0;
 993
 994         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
 995                                    req->u.discard.nr_sectors,
 996                                    GFP_KERNEL, secure);
 997 fail_response:
 998         if (err == -EOPNOTSUPP) {
 999                 pr_debug("discard op failed, not supported\n");
1000                 status = BLKIF_RSP_EOPNOTSUPP;
1001         } else if (err)
1002                 status = BLKIF_RSP_ERROR;
1003
1004         make_response(ring, req->u.discard.id, req->operation, status);
1005         xen_blkif_put(blkif);
1006         return err;
1007 }
1008
1009 static int dispatch_other_io(struct xen_blkif_ring *ring,
1010                              struct blkif_request *req,
1011                              struct pending_req *pending_req)
1012 {
1013         free_req(ring, pending_req);
1014         make_response(ring, req->u.other.id, req->operation,
1015                       BLKIF_RSP_EOPNOTSUPP);
1016         return -EIO;
1017 }
1018
1019 static void xen_blk_drain_io(struct xen_blkif_ring *ring)
1020 {
1021         struct xen_blkif *blkif = ring->blkif;
1022
1023         atomic_set(&blkif->drain, 1);
1024         do {
1025                 if (atomic_read(&ring->inflight) == 0)
1026                         break;
1027                 wait_for_completion_interruptible_timeout(
1028                                 &blkif->drain_complete, HZ);
1029
1030                 if (!atomic_read(&blkif->drain))
1031                         break;
1032         } while (!kthread_should_stop());
1033         atomic_set(&blkif->drain, 0);
1034 }
1035
1036 static void __end_block_io_op(struct pending_req *pending_req,
1037                 blk_status_t error)
1038 {
1039         /* An error fails the entire request. */
1040         if (pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE &&
1041             error == BLK_STS_NOTSUPP) {
1042                 pr_debug("flush diskcache op failed, not supported\n");
1043                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->ring->blkif->be, 0);
1044                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1045         } else if (pending_req->operation == BLKIF_OP_WRITE_BARRIER &&
1046                    error == BLK_STS_NOTSUPP) {
1047                 pr_debug("write barrier op failed, not supported\n");
1048                 xen_blkbk_barrier(XBT_NIL, pending_req->ring->blkif->be, 0);
1049                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1050         } else if (error) {
1051                 pr_debug("Buffer not up-to-date at end of operation,"
1052                          " error=%d\n", error);
1053                 pending_req->status = BLKIF_RSP_ERROR;
1054         }
1055
1056         /*
1057          * If all of the bio's have completed it is time to unmap
1058          * the grant references associated with 'request' and provide
1059          * the proper response on the ring.
1060          */
1061         if (atomic_dec_and_test(&pending_req->pendcnt))
1062                 xen_blkbk_unmap_and_respond(pending_req);
1063 }
1064
1065 /*
1066  * bio callback.
1067  */
1068 static void end_block_io_op(struct bio *bio)
1069 {
1070         __end_block_io_op(bio->bi_private, bio->bi_status);
1071         bio_put(bio);
1072 }
1073
1074
1075
1076 /*
1077  * Function to copy the from the ring buffer the 'struct blkif_request'
1078  * (which has the sectors we want, number of them, grant references, etc),
1079  * and transmute  it to the block API to hand it over to the proper block disk.
1080  */
1081 static int
1082 __do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
1083 {
1084         union blkif_back_rings *blk_rings = &ring->blk_rings;
1085         struct blkif_request req;
1086         struct pending_req *pending_req;
1087         RING_IDX rc, rp;
1088         int more_to_do = 0;
1089
1090         rc = blk_rings->common.req_cons;
1091         rp = blk_rings->common.sring->req_prod;
1092         rmb(); /* Ensure we see queued requests up to 'rp'. */
1093
1094         if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
1095                 rc = blk_rings->common.rsp_prod_pvt;
1096                 pr_warn("Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n",
1097                         rp, rc, rp - rc, ring->blkif->vbd.pdevice);
1098                 return -EACCES;
1099         }
1100         while (rc != rp) {
1101
1102                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1103                         break;
1104
1105                 /* We've seen a request, so clear spurious eoi flag. */
1106                 *eoi_flags &= ~XEN_EOI_FLAG_SPURIOUS;
1107
1108                 if (kthread_should_stop()) {
1109                         more_to_do = 1;
1110                         break;
1111                 }
1112
1113                 pending_req = alloc_req(ring);
1114                 if (NULL == pending_req) {
1115                         ring->st_oo_req++;
1116                         more_to_do = 1;
1117                         break;
1118                 }
1119
1120                 switch (ring->blkif->blk_protocol) {
1121                 case BLKIF_PROTOCOL_NATIVE:
1122                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1123                         break;
1124                 case BLKIF_PROTOCOL_X86_32:
1125                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1126                         break;
1127                 case BLKIF_PROTOCOL_X86_64:
1128                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1129                         break;
1130                 default:
1131                         BUG();
1132                 }
1133                 blk_rings->common.req_cons = ++rc; /* before make_response() */
1134
1135                 /* Apply all sanity checks to /private copy/ of request. */
1136                 barrier();
1137
1138                 switch (req.operation) {
1139                 case BLKIF_OP_READ:
1140                 case BLKIF_OP_WRITE:
1141                 case BLKIF_OP_WRITE_BARRIER:
1142                 case BLKIF_OP_FLUSH_DISKCACHE:
1143                 case BLKIF_OP_INDIRECT:
1144                         if (dispatch_rw_block_io(ring, &req, pending_req))
1145                                 goto done;
1146                         break;
1147                 case BLKIF_OP_DISCARD:
1148                         free_req(ring, pending_req);
1149                         if (dispatch_discard_io(ring, &req))
1150                                 goto done;
1151                         break;
1152                 default:
1153                         if (dispatch_other_io(ring, &req, pending_req))
1154                                 goto done;
1155                         break;
1156                 }
1157
1158                 /* Yield point for this unbounded loop. */
1159                 cond_resched();
1160         }
1161 done:
1162         return more_to_do;
1163 }
1164
1165 static int
1166 do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
1167 {
1168         union blkif_back_rings *blk_rings = &ring->blk_rings;
1169         int more_to_do;
1170
1171         do {
1172                 more_to_do = __do_block_io_op(ring, eoi_flags);
1173                 if (more_to_do)
1174                         break;
1175
1176                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1177         } while (more_to_do);
1178
1179         return more_to_do;
1180 }
1181 /*
1182  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1183  * and call the 'submit_bio' to pass it to the underlying storage.
1184  */
1185 static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
1186                                 struct blkif_request *req,
1187                                 struct pending_req *pending_req)
1188 {
1189         struct phys_req preq;
1190         struct seg_buf *seg = pending_req->seg;
1191         unsigned int nseg;
1192         struct bio *bio = NULL;
1193         struct bio **biolist = pending_req->biolist;
1194         int i, nbio = 0;
1195         int operation;
1196         int operation_flags = 0;
1197         struct blk_plug plug;
1198         bool drain = false;
1199         struct grant_page **pages = pending_req->segments;
1200         unsigned short req_operation;
1201
1202         req_operation = req->operation == BLKIF_OP_INDIRECT ?
1203                         req->u.indirect.indirect_op : req->operation;
1204
1205         if ((req->operation == BLKIF_OP_INDIRECT) &&
1206             (req_operation != BLKIF_OP_READ) &&
1207             (req_operation != BLKIF_OP_WRITE)) {
1208                 pr_debug("Invalid indirect operation (%u)\n", req_operation);
1209                 goto fail_response;
1210         }
1211
1212         switch (req_operation) {
1213         case BLKIF_OP_READ:
1214                 ring->st_rd_req++;
1215                 operation = REQ_OP_READ;
1216                 break;
1217         case BLKIF_OP_WRITE:
1218                 ring->st_wr_req++;
1219                 operation = REQ_OP_WRITE;
1220                 operation_flags = REQ_SYNC | REQ_IDLE;
1221                 break;
1222         case BLKIF_OP_WRITE_BARRIER:
1223                 drain = true;
1224                 fallthrough;
1225         case BLKIF_OP_FLUSH_DISKCACHE:
1226                 ring->st_f_req++;
1227                 operation = REQ_OP_WRITE;
1228                 operation_flags = REQ_PREFLUSH;
1229                 break;
1230         default:
1231                 operation = 0; /* make gcc happy */
1232                 goto fail_response;
1233                 break;
1234         }
1235
1236         /* Check that the number of segments is sane. */
1237         nseg = req->operation == BLKIF_OP_INDIRECT ?
1238                req->u.indirect.nr_segments : req->u.rw.nr_segments;
1239
1240         if (unlikely(nseg == 0 && operation_flags != REQ_PREFLUSH) ||
1241             unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1242                      (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1243             unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1244                      (nseg > MAX_INDIRECT_SEGMENTS))) {
1245                 pr_debug("Bad number of segments in request (%d)\n", nseg);
1246                 /* Haven't submitted any bio's yet. */
1247                 goto fail_response;
1248         }
1249
1250         preq.nr_sects      = 0;
1251
1252         pending_req->ring      = ring;
1253         pending_req->id        = req->u.rw.id;
1254         pending_req->operation = req_operation;
1255         pending_req->status    = BLKIF_RSP_OKAY;
1256         pending_req->nr_segs   = nseg;
1257
1258         if (req->operation != BLKIF_OP_INDIRECT) {
1259                 preq.dev               = req->u.rw.handle;
1260                 preq.sector_number     = req->u.rw.sector_number;
1261                 for (i = 0; i < nseg; i++) {
1262                         pages[i]->gref = req->u.rw.seg[i].gref;
1263                         seg[i].nsec = req->u.rw.seg[i].last_sect -
1264                                 req->u.rw.seg[i].first_sect + 1;
1265                         seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1266                         if ((req->u.rw.seg[i].last_sect >= (XEN_PAGE_SIZE >> 9)) ||
1267                             (req->u.rw.seg[i].last_sect <
1268                              req->u.rw.seg[i].first_sect))
1269                                 goto fail_response;
1270                         preq.nr_sects += seg[i].nsec;
1271                 }
1272         } else {
1273                 preq.dev               = req->u.indirect.handle;
1274                 preq.sector_number     = req->u.indirect.sector_number;
1275                 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1276                         goto fail_response;
1277         }
1278
1279         if (xen_vbd_translate(&preq, ring->blkif, operation) != 0) {
1280                 pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n",
1281                          operation == REQ_OP_READ ? "read" : "write",
1282                          preq.sector_number,
1283                          preq.sector_number + preq.nr_sects,
1284                          ring->blkif->vbd.pdevice);
1285                 goto fail_response;
1286         }
1287
1288         /*
1289          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1290          * is set there.
1291          */
1292         for (i = 0; i < nseg; i++) {
1293                 if (((int)preq.sector_number|(int)seg[i].nsec) &
1294                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1295                         pr_debug("Misaligned I/O request from domain %d\n",
1296                                  ring->blkif->domid);
1297                         goto fail_response;
1298                 }
1299         }
1300
1301         /* Wait on all outstanding I/O's and once that has been completed
1302          * issue the flush.
1303          */
1304         if (drain)
1305                 xen_blk_drain_io(pending_req->ring);
1306
1307         /*
1308          * If we have failed at this point, we need to undo the M2P override,
1309          * set gnttab_set_unmap_op on all of the grant references and perform
1310          * the hypercall to unmap the grants - that is all done in
1311          * xen_blkbk_unmap.
1312          */
1313         if (xen_blkbk_map_seg(pending_req))
1314                 goto fail_flush;
1315
1316         /*
1317          * This corresponding xen_blkif_put is done in __end_block_io_op, or
1318          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1319          */
1320         xen_blkif_get(ring->blkif);
1321         atomic_inc(&ring->inflight);
1322
1323         for (i = 0; i < nseg; i++) {
1324                 while ((bio == NULL) ||
1325                        (bio_add_page(bio,
1326                                      pages[i]->page,
1327                                      seg[i].nsec << 9,
1328                                      seg[i].offset) == 0)) {
1329                         bio = bio_alloc(GFP_KERNEL, bio_max_segs(nseg - i));
1330                         if (unlikely(bio == NULL))
1331                                 goto fail_put_bio;
1332
1333                         biolist[nbio++] = bio;
1334                         bio_set_dev(bio, 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                         bio_set_op_attrs(bio, operation, operation_flags);
1339                 }
1340
1341                 preq.sector_number += seg[i].nsec;
1342         }
1343
1344         /* This will be hit if the operation was a flush or discard. */
1345         if (!bio) {
1346                 BUG_ON(operation_flags != REQ_PREFLUSH);
1347
1348                 bio = bio_alloc(GFP_KERNEL, 0);
1349                 if (unlikely(bio == NULL))
1350                         goto fail_put_bio;
1351
1352                 biolist[nbio++] = bio;
1353                 bio_set_dev(bio, preq.bdev);
1354                 bio->bi_private = pending_req;
1355                 bio->bi_end_io  = end_block_io_op;
1356                 bio_set_op_attrs(bio, operation, operation_flags);
1357         }
1358
1359         atomic_set(&pending_req->pendcnt, nbio);
1360         blk_start_plug(&plug);
1361
1362         for (i = 0; i < nbio; i++)
1363                 submit_bio(biolist[i]);
1364
1365         /* Let the I/Os go.. */
1366         blk_finish_plug(&plug);
1367
1368         if (operation == REQ_OP_READ)
1369                 ring->st_rd_sect += preq.nr_sects;
1370         else if (operation == REQ_OP_WRITE)
1371                 ring->st_wr_sect += preq.nr_sects;
1372
1373         return 0;
1374
1375  fail_flush:
1376         xen_blkbk_unmap(ring, pending_req->segments,
1377                         pending_req->nr_segs);
1378  fail_response:
1379         /* Haven't submitted any bio's yet. */
1380         make_response(ring, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1381         free_req(ring, pending_req);
1382         msleep(1); /* back off a bit */
1383         return -EIO;
1384
1385  fail_put_bio:
1386         for (i = 0; i < nbio; i++)
1387                 bio_put(biolist[i]);
1388         atomic_set(&pending_req->pendcnt, 1);
1389         __end_block_io_op(pending_req, BLK_STS_RESOURCE);
1390         msleep(1); /* back off a bit */
1391         return -EIO;
1392 }
1393
1394
1395
1396 /*
1397  * Put a response on the ring on how the operation fared.
1398  */
1399 static void make_response(struct xen_blkif_ring *ring, u64 id,
1400                           unsigned short op, int st)
1401 {
1402         struct blkif_response *resp;
1403         unsigned long     flags;
1404         union blkif_back_rings *blk_rings;
1405         int notify;
1406
1407         spin_lock_irqsave(&ring->blk_ring_lock, flags);
1408         blk_rings = &ring->blk_rings;
1409         /* Place on the response ring for the relevant domain. */
1410         switch (ring->blkif->blk_protocol) {
1411         case BLKIF_PROTOCOL_NATIVE:
1412                 resp = RING_GET_RESPONSE(&blk_rings->native,
1413                                          blk_rings->native.rsp_prod_pvt);
1414                 break;
1415         case BLKIF_PROTOCOL_X86_32:
1416                 resp = RING_GET_RESPONSE(&blk_rings->x86_32,
1417                                          blk_rings->x86_32.rsp_prod_pvt);
1418                 break;
1419         case BLKIF_PROTOCOL_X86_64:
1420                 resp = RING_GET_RESPONSE(&blk_rings->x86_64,
1421                                          blk_rings->x86_64.rsp_prod_pvt);
1422                 break;
1423         default:
1424                 BUG();
1425         }
1426
1427         resp->id        = id;
1428         resp->operation = op;
1429         resp->status    = st;
1430
1431         blk_rings->common.rsp_prod_pvt++;
1432         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1433         spin_unlock_irqrestore(&ring->blk_ring_lock, flags);
1434         if (notify)
1435                 notify_remote_via_irq(ring->irq);
1436 }
1437
1438 static int __init xen_blkif_init(void)
1439 {
1440         int rc = 0;
1441
1442         if (!xen_domain())
1443                 return -ENODEV;
1444
1445         if (xen_blkif_max_ring_order > XENBUS_MAX_RING_GRANT_ORDER) {
1446                 pr_info("Invalid max_ring_order (%d), will use default max: %d.\n",
1447                         xen_blkif_max_ring_order, XENBUS_MAX_RING_GRANT_ORDER);
1448                 xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
1449         }
1450
1451         if (xenblk_max_queues == 0)
1452                 xenblk_max_queues = num_online_cpus();
1453
1454         rc = xen_blkif_interface_init();
1455         if (rc)
1456                 goto failed_init;
1457
1458         rc = xen_blkif_xenbus_init();
1459         if (rc)
1460                 goto failed_init;
1461
1462  failed_init:
1463         return rc;
1464 }
1465
1466 module_init(xen_blkif_init);
1467
1468 static void __exit xen_blkif_fini(void)
1469 {
1470         xen_blkif_xenbus_fini();
1471         xen_blkif_interface_fini();
1472 }
1473
1474 module_exit(xen_blkif_fini);
1475
1476 MODULE_LICENSE("Dual BSD/GPL");
1477 MODULE_ALIAS("xen-backend:vbd");