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)
 243 {
 244         struct rb_root *root = &ring->persistent_gnts;
 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         if (RB_EMPTY_ROOT(root))
 253                 return;
 254
 255         unmap_data.pages = pages;
 256         unmap_data.unmap_ops = unmap;
 257         unmap_data.kunmap_ops = NULL;
 258
 259         foreach_grant_safe(persistent_gnt, n, root, node) {
 260                 BUG_ON(persistent_gnt->handle ==
 261                         BLKBACK_INVALID_HANDLE);
 262                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 263                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 264                                 persistent_gnt->page)),
 265                         GNTMAP_host_map,
 266                         persistent_gnt->handle);
 267
 268                 pages[segs_to_unmap] = persistent_gnt->page;
 269
 270                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 271                         !rb_next(&persistent_gnt->node)) {
 272
 273                         unmap_data.count = segs_to_unmap;
 274                         BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 275
 276                         gnttab_page_cache_put(&ring->free_pages, pages,
 277                                               segs_to_unmap);
 278                         segs_to_unmap = 0;
 279                 }
 280
 281                 rb_erase(&persistent_gnt->node, root);
 282                 kfree(persistent_gnt);
 283                 ring->persistent_gnt_c--;
 284         }
 285
 286         BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts));
 287         BUG_ON(ring->persistent_gnt_c != 0);
 288 }
 289
 290 void xen_blkbk_unmap_purged_grants(struct work_struct *work)
 291 {
 292         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 293         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 294         struct persistent_gnt *persistent_gnt;
 295         int segs_to_unmap = 0;
 296         struct xen_blkif_ring *ring = container_of(work, typeof(*ring), persistent_purge_work);
 297         struct gntab_unmap_queue_data unmap_data;
 298
 299         unmap_data.pages = pages;
 300         unmap_data.unmap_ops = unmap;
 301         unmap_data.kunmap_ops = NULL;
 302
 303         while(!list_empty(&ring->persistent_purge_list)) {
 304                 persistent_gnt = list_first_entry(&ring->persistent_purge_list,
 305                                                   struct persistent_gnt,
 306                                                   remove_node);
 307                 list_del(&persistent_gnt->remove_node);
 308
 309                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 310                         vaddr(persistent_gnt->page),
 311                         GNTMAP_host_map,
 312                         persistent_gnt->handle);
 313
 314                 pages[segs_to_unmap] = persistent_gnt->page;
 315
 316                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) {
 317                         unmap_data.count = segs_to_unmap;
 318                         BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 319                         gnttab_page_cache_put(&ring->free_pages, pages,
 320                                               segs_to_unmap);
 321                         segs_to_unmap = 0;
 322                 }
 323                 kfree(persistent_gnt);
 324         }
 325         if (segs_to_unmap > 0) {
 326                 unmap_data.count = segs_to_unmap;
 327                 BUG_ON(gnttab_unmap_refs_sync(&unmap_data));
 328                 gnttab_page_cache_put(&ring->free_pages, pages, segs_to_unmap);
 329         }
 330 }
 331
 332 static void purge_persistent_gnt(struct xen_blkif_ring *ring)
 333 {
 334         struct persistent_gnt *persistent_gnt;
 335         struct rb_node *n;
 336         unsigned int num_clean, total;
 337         bool scan_used = false;
 338         struct rb_root *root;
 339
 340         if (work_busy(&ring->persistent_purge_work)) {
 341                 pr_alert_ratelimited("Scheduled work from previous purge is still busy, cannot purge list\n");
 342                 goto out;
 343         }
 344
 345         if (ring->persistent_gnt_c < max_pgrants ||
 346             (ring->persistent_gnt_c == max_pgrants &&
 347             !ring->blkif->vbd.overflow_max_grants)) {
 348                 num_clean = 0;
 349         } else {
 350                 num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN;
 351                 num_clean = ring->persistent_gnt_c - max_pgrants + num_clean;
 352                 num_clean = min(ring->persistent_gnt_c, num_clean);
 353                 pr_debug("Going to purge at least %u persistent grants\n",
 354                          num_clean);
 355         }
 356
 357         /*
 358          * At this point, we can assure that there will be no calls
 359          * to get_persistent_grant (because we are executing this code from
 360          * xen_blkif_schedule), there can only be calls to put_persistent_gnt,
 361          * which means that the number of currently used grants will go down,
 362          * but never up, so we will always be able to remove the requested
 363          * number of grants.
 364          */
 365
 366         total = 0;
 367
 368         BUG_ON(!list_empty(&ring->persistent_purge_list));
 369         root = &ring->persistent_gnts;
 370 purge_list:
 371         foreach_grant_safe(persistent_gnt, n, root, node) {
 372                 BUG_ON(persistent_gnt->handle ==
 373                         BLKBACK_INVALID_HANDLE);
 374
 375                 if (persistent_gnt->active)
 376                         continue;
 377                 if (!scan_used && !persistent_gnt_timeout(persistent_gnt))
 378                         continue;
 379                 if (scan_used && total >= num_clean)
 380                         continue;
 381
 382                 rb_erase(&persistent_gnt->node, root);
 383                 list_add(&persistent_gnt->remove_node,
 384                          &ring->persistent_purge_list);
 385                 total++;
 386         }
 387         /*
 388          * Check whether we also need to start cleaning
 389          * grants that were used since last purge in order to cope
 390          * with the requested num
 391          */
 392         if (!scan_used && total < num_clean) {
 393                 pr_debug("Still missing %u purged frames\n", num_clean - total);
 394                 scan_used = true;
 395                 goto purge_list;
 396         }
 397
 398         if (total) {
 399                 ring->persistent_gnt_c -= total;
 400                 ring->blkif->vbd.overflow_max_grants = 0;
 401
 402                 /* We can defer this work */
 403                 schedule_work(&ring->persistent_purge_work);
 404                 pr_debug("Purged %u/%u\n", num_clean, total);
 405         }
 406
 407 out:
 408         return;
 409 }
 410
 411 /*
 412  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 413  */
 414 static struct pending_req *alloc_req(struct xen_blkif_ring *ring)
 415 {
 416         struct pending_req *req = NULL;
 417         unsigned long flags;
 418
 419         spin_lock_irqsave(&ring->pending_free_lock, flags);
 420         if (!list_empty(&ring->pending_free)) {
 421                 req = list_entry(ring->pending_free.next, struct pending_req,
 422                                  free_list);
 423                 list_del(&req->free_list);
 424         }
 425         spin_unlock_irqrestore(&ring->pending_free_lock, flags);
 426         return req;
 427 }
 428
 429 /*
 430  * Return the 'pending_req' structure back to the freepool. We also
 431  * wake up the thread if it was waiting for a free page.
 432  */
 433 static void free_req(struct xen_blkif_ring *ring, struct pending_req *req)
 434 {
 435         unsigned long flags;
 436         int was_empty;
 437
 438         spin_lock_irqsave(&ring->pending_free_lock, flags);
 439         was_empty = list_empty(&ring->pending_free);
 440         list_add(&req->free_list, &ring->pending_free);
 441         spin_unlock_irqrestore(&ring->pending_free_lock, flags);
 442         if (was_empty)
 443                 wake_up(&ring->pending_free_wq);
 444 }
 445
 446 /*
 447  * Routines for managing virtual block devices (vbds).
 448  */
 449 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 450                              enum req_op operation)
 451 {
 452         struct xen_vbd *vbd = &blkif->vbd;
 453         int rc = -EACCES;
 454
 455         if ((operation != REQ_OP_READ) && vbd->readonly)
 456                 goto out;
 457
 458         if (likely(req->nr_sects)) {
 459                 blkif_sector_t end = req->sector_number + req->nr_sects;
 460
 461                 if (unlikely(end < req->sector_number))
 462                         goto out;
 463                 if (unlikely(end > vbd_sz(vbd)))
 464                         goto out;
 465         }
 466
 467         req->dev  = vbd->pdevice;
 468         req->bdev = vbd->bdev_handle->bdev;
 469         rc = 0;
 470
 471  out:
 472         return rc;
 473 }
 474
 475 static void xen_vbd_resize(struct xen_blkif *blkif)
 476 {
 477         struct xen_vbd *vbd = &blkif->vbd;
 478         struct xenbus_transaction xbt;
 479         int err;
 480         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 481         unsigned long long new_size = vbd_sz(vbd);
 482
 483         pr_info("VBD Resize: Domid: %d, Device: (%d, %d)\n",
 484                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 485         pr_info("VBD Resize: new size %llu\n", new_size);
 486         vbd->size = new_size;
 487 again:
 488         err = xenbus_transaction_start(&xbt);
 489         if (err) {
 490                 pr_warn("Error starting transaction\n");
 491                 return;
 492         }
 493         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 494                             (unsigned long long)vbd_sz(vbd));
 495         if (err) {
 496                 pr_warn("Error writing new size\n");
 497                 goto abort;
 498         }
 499         /*
 500          * Write the current state; we will use this to synchronize
 501          * the front-end. If the current state is "connected" the
 502          * front-end will get the new size information online.
 503          */
 504         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 505         if (err) {
 506                 pr_warn("Error writing the state\n");
 507                 goto abort;
 508         }
 509
 510         err = xenbus_transaction_end(xbt, 0);
 511         if (err == -EAGAIN)
 512                 goto again;
 513         if (err)
 514                 pr_warn("Error ending transaction\n");
 515         return;
 516 abort:
 517         xenbus_transaction_end(xbt, 1);
 518 }
 519
 520 /*
 521  * Notification from the guest OS.
 522  */
 523 static void blkif_notify_work(struct xen_blkif_ring *ring)
 524 {
 525         ring->waiting_reqs = 1;
 526         wake_up(&ring->wq);
 527 }
 528
 529 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 530 {
 531         blkif_notify_work(dev_id);
 532         return IRQ_HANDLED;
 533 }
 534
 535 /*
 536  * SCHEDULER FUNCTIONS
 537  */
 538
 539 static void print_stats(struct xen_blkif_ring *ring)
 540 {
 541         pr_info("(%s): oo %3llu  |  rd %4llu  |  wr %4llu  |  f %4llu"
 542                  "  |  ds %4llu | pg: %4u/%4d\n",
 543                  current->comm, ring->st_oo_req,
 544                  ring->st_rd_req, ring->st_wr_req,
 545                  ring->st_f_req, ring->st_ds_req,
 546                  ring->persistent_gnt_c, max_pgrants);
 547         ring->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 548         ring->st_rd_req = 0;
 549         ring->st_wr_req = 0;
 550         ring->st_oo_req = 0;
 551         ring->st_ds_req = 0;
 552 }
 553
 554 int xen_blkif_schedule(void *arg)
 555 {
 556         struct xen_blkif_ring *ring = arg;
 557         struct xen_blkif *blkif = ring->blkif;
 558         struct xen_vbd *vbd = &blkif->vbd;
 559         unsigned long timeout;
 560         int ret;
 561         bool do_eoi;
 562         unsigned int eoi_flags = XEN_EOI_FLAG_SPURIOUS;
 563
 564         set_freezable();
 565         while (!kthread_should_stop()) {
 566                 if (try_to_freeze())
 567                         continue;
 568                 if (unlikely(vbd->size != vbd_sz(vbd)))
 569                         xen_vbd_resize(blkif);
 570
 571                 timeout = msecs_to_jiffies(LRU_INTERVAL);
 572
 573                 timeout = wait_event_interruptible_timeout(
 574                         ring->wq,
 575                         ring->waiting_reqs || kthread_should_stop(),
 576                         timeout);
 577                 if (timeout == 0)
 578                         goto purge_gnt_list;
 579                 timeout = wait_event_interruptible_timeout(
 580                         ring->pending_free_wq,
 581                         !list_empty(&ring->pending_free) ||
 582                         kthread_should_stop(),
 583                         timeout);
 584                 if (timeout == 0)
 585                         goto purge_gnt_list;
 586
 587                 do_eoi = ring->waiting_reqs;
 588
 589                 ring->waiting_reqs = 0;
 590                 smp_mb(); /* clear flag *before* checking for work */
 591
 592                 ret = do_block_io_op(ring, &eoi_flags);
 593                 if (ret > 0)
 594                         ring->waiting_reqs = 1;
 595                 if (ret == -EACCES)
 596                         wait_event_interruptible(ring->shutdown_wq,
 597                                                  kthread_should_stop());
 598
 599                 if (do_eoi && !ring->waiting_reqs) {
 600                         xen_irq_lateeoi(ring->irq, eoi_flags);
 601                         eoi_flags |= XEN_EOI_FLAG_SPURIOUS;
 602                 }
 603
 604 purge_gnt_list:
 605                 if (blkif->vbd.feature_gnt_persistent &&
 606                     time_after(jiffies, ring->next_lru)) {
 607                         purge_persistent_gnt(ring);
 608                         ring->next_lru = jiffies + msecs_to_jiffies(LRU_INTERVAL);
 609                 }
 610
 611                 /* Shrink the free pages pool if it is too large. */
 612                 if (time_before(jiffies, blkif->buffer_squeeze_end))
 613                         gnttab_page_cache_shrink(&ring->free_pages, 0);
 614                 else
 615                         gnttab_page_cache_shrink(&ring->free_pages,
 616                                                  max_buffer_pages);
 617
 618                 if (log_stats && time_after(jiffies, ring->st_print))
 619                         print_stats(ring);
 620         }
 621
 622         /* Drain pending purge work */
 623         flush_work(&ring->persistent_purge_work);
 624
 625         if (log_stats)
 626                 print_stats(ring);
 627
 628         ring->xenblkd = NULL;
 629
 630         return 0;
 631 }
 632
 633 /*
 634  * Remove persistent grants and empty the pool of free pages
 635  */
 636 void xen_blkbk_free_caches(struct xen_blkif_ring *ring)
 637 {
 638         /* Free all persistent grant pages */
 639         free_persistent_gnts(ring);
 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 >= map_until)
 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; 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_handle->bdev;
 973         struct phys_req preq;
 974
 975         xen_blkif_get(blkif);
 976
 977         preq.sector_number = req->u.discard.sector_number;
 978         preq.nr_sects      = req->u.discard.nr_sectors;
 979
 980         err = xen_vbd_translate(&preq, blkif, REQ_OP_WRITE);
 981         if (err) {
 982                 pr_warn("access denied: DISCARD [%llu->%llu] on dev=%04x\n",
 983                         preq.sector_number,
 984                         preq.sector_number + preq.nr_sects, blkif->vbd.pdevice);
 985                 goto fail_response;
 986         }
 987         ring->st_ds_req++;
 988
 989         if (blkif->vbd.discard_secure &&
 990             (req->u.discard.flag & BLKIF_DISCARD_SECURE))
 991                 err = blkdev_issue_secure_erase(bdev,
 992                                 req->u.discard.sector_number,
 993                                 req->u.discard.nr_sectors, GFP_KERNEL);
 994         else
 995                 err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
 996                                 req->u.discard.nr_sectors, GFP_KERNEL);
 997
 998 fail_response:
 999         if (err == -EOPNOTSUPP) {
1000                 pr_debug("discard op failed, not supported\n");
1001                 status = BLKIF_RSP_EOPNOTSUPP;
1002         } else if (err)
1003                 status = BLKIF_RSP_ERROR;
1004
1005         make_response(ring, req->u.discard.id, req->operation, status);
1006         xen_blkif_put(blkif);
1007         return err;
1008 }
1009
1010 static int dispatch_other_io(struct xen_blkif_ring *ring,
1011                              struct blkif_request *req,
1012                              struct pending_req *pending_req)
1013 {
1014         free_req(ring, pending_req);
1015         make_response(ring, req->u.other.id, req->operation,
1016                       BLKIF_RSP_EOPNOTSUPP);
1017         return -EIO;
1018 }
1019
1020 static void xen_blk_drain_io(struct xen_blkif_ring *ring)
1021 {
1022         struct xen_blkif *blkif = ring->blkif;
1023
1024         atomic_set(&blkif->drain, 1);
1025         do {
1026                 if (atomic_read(&ring->inflight) == 0)
1027                         break;
1028                 wait_for_completion_interruptible_timeout(
1029                                 &blkif->drain_complete, HZ);
1030
1031                 if (!atomic_read(&blkif->drain))
1032                         break;
1033         } while (!kthread_should_stop());
1034         atomic_set(&blkif->drain, 0);
1035 }
1036
1037 static void __end_block_io_op(struct pending_req *pending_req,
1038                 blk_status_t error)
1039 {
1040         /* An error fails the entire request. */
1041         if (pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE &&
1042             error == BLK_STS_NOTSUPP) {
1043                 pr_debug("flush diskcache op failed, not supported\n");
1044                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->ring->blkif->be, 0);
1045                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1046         } else if (pending_req->operation == BLKIF_OP_WRITE_BARRIER &&
1047                    error == BLK_STS_NOTSUPP) {
1048                 pr_debug("write barrier op failed, not supported\n");
1049                 xen_blkbk_barrier(XBT_NIL, pending_req->ring->blkif->be, 0);
1050                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
1051         } else if (error) {
1052                 pr_debug("Buffer not up-to-date at end of operation,"
1053                          " error=%d\n", error);
1054                 pending_req->status = BLKIF_RSP_ERROR;
1055         }
1056
1057         /*
1058          * If all of the bio's have completed it is time to unmap
1059          * the grant references associated with 'request' and provide
1060          * the proper response on the ring.
1061          */
1062         if (atomic_dec_and_test(&pending_req->pendcnt))
1063                 xen_blkbk_unmap_and_respond(pending_req);
1064 }
1065
1066 /*
1067  * bio callback.
1068  */
1069 static void end_block_io_op(struct bio *bio)
1070 {
1071         __end_block_io_op(bio->bi_private, bio->bi_status);
1072         bio_put(bio);
1073 }
1074
1075 static void blkif_get_x86_32_req(struct blkif_request *dst,
1076                                  const struct blkif_x86_32_request *src)
1077 {
1078         unsigned int i, n;
1079
1080         dst->operation = READ_ONCE(src->operation);
1081
1082         switch (dst->operation) {
1083         case BLKIF_OP_READ:
1084         case BLKIF_OP_WRITE:
1085         case BLKIF_OP_WRITE_BARRIER:
1086         case BLKIF_OP_FLUSH_DISKCACHE:
1087                 dst->u.rw.nr_segments = READ_ONCE(src->u.rw.nr_segments);
1088                 dst->u.rw.handle = src->u.rw.handle;
1089                 dst->u.rw.id = src->u.rw.id;
1090                 dst->u.rw.sector_number = src->u.rw.sector_number;
1091                 n = min_t(unsigned int, BLKIF_MAX_SEGMENTS_PER_REQUEST,
1092                           dst->u.rw.nr_segments);
1093                 for (i = 0; i < n; i++)
1094                         dst->u.rw.seg[i] = src->u.rw.seg[i];
1095                 break;
1096
1097         case BLKIF_OP_DISCARD:
1098                 dst->u.discard.flag = src->u.discard.flag;
1099                 dst->u.discard.id = src->u.discard.id;
1100                 dst->u.discard.sector_number = src->u.discard.sector_number;
1101                 dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
1102                 break;
1103
1104         case BLKIF_OP_INDIRECT:
1105                 dst->u.indirect.indirect_op = src->u.indirect.indirect_op;
1106                 dst->u.indirect.nr_segments =
1107                         READ_ONCE(src->u.indirect.nr_segments);
1108                 dst->u.indirect.handle = src->u.indirect.handle;
1109                 dst->u.indirect.id = src->u.indirect.id;
1110                 dst->u.indirect.sector_number = src->u.indirect.sector_number;
1111                 n = min(MAX_INDIRECT_PAGES,
1112                         INDIRECT_PAGES(dst->u.indirect.nr_segments));
1113                 for (i = 0; i < n; i++)
1114                         dst->u.indirect.indirect_grefs[i] =
1115                                 src->u.indirect.indirect_grefs[i];
1116                 break;
1117
1118         default:
1119                 /*
1120                  * Don't know how to translate this op. Only get the
1121                  * ID so failure can be reported to the frontend.
1122                  */
1123                 dst->u.other.id = src->u.other.id;
1124                 break;
1125         }
1126 }
1127
1128 static void blkif_get_x86_64_req(struct blkif_request *dst,
1129                                  const struct blkif_x86_64_request *src)
1130 {
1131         unsigned int i, n;
1132
1133         dst->operation = READ_ONCE(src->operation);
1134
1135         switch (dst->operation) {
1136         case BLKIF_OP_READ:
1137         case BLKIF_OP_WRITE:
1138         case BLKIF_OP_WRITE_BARRIER:
1139         case BLKIF_OP_FLUSH_DISKCACHE:
1140                 dst->u.rw.nr_segments = READ_ONCE(src->u.rw.nr_segments);
1141                 dst->u.rw.handle = src->u.rw.handle;
1142                 dst->u.rw.id = src->u.rw.id;
1143                 dst->u.rw.sector_number = src->u.rw.sector_number;
1144                 n = min_t(unsigned int, BLKIF_MAX_SEGMENTS_PER_REQUEST,
1145                           dst->u.rw.nr_segments);
1146                 for (i = 0; i < n; i++)
1147                         dst->u.rw.seg[i] = src->u.rw.seg[i];
1148                 break;
1149
1150         case BLKIF_OP_DISCARD:
1151                 dst->u.discard.flag = src->u.discard.flag;
1152                 dst->u.discard.id = src->u.discard.id;
1153                 dst->u.discard.sector_number = src->u.discard.sector_number;
1154                 dst->u.discard.nr_sectors = src->u.discard.nr_sectors;
1155                 break;
1156
1157         case BLKIF_OP_INDIRECT:
1158                 dst->u.indirect.indirect_op = src->u.indirect.indirect_op;
1159                 dst->u.indirect.nr_segments =
1160                         READ_ONCE(src->u.indirect.nr_segments);
1161                 dst->u.indirect.handle = src->u.indirect.handle;
1162                 dst->u.indirect.id = src->u.indirect.id;
1163                 dst->u.indirect.sector_number = src->u.indirect.sector_number;
1164                 n = min(MAX_INDIRECT_PAGES,
1165                         INDIRECT_PAGES(dst->u.indirect.nr_segments));
1166                 for (i = 0; i < n; i++)
1167                         dst->u.indirect.indirect_grefs[i] =
1168                                 src->u.indirect.indirect_grefs[i];
1169                 break;
1170
1171         default:
1172                 /*
1173                  * Don't know how to translate this op. Only get the
1174                  * ID so failure can be reported to the frontend.
1175                  */
1176                 dst->u.other.id = src->u.other.id;
1177                 break;
1178         }
1179 }
1180
1181 /*
1182  * Function to copy the from the ring buffer the 'struct blkif_request'
1183  * (which has the sectors we want, number of them, grant references, etc),
1184  * and transmute  it to the block API to hand it over to the proper block disk.
1185  */
1186 static int
1187 __do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
1188 {
1189         union blkif_back_rings *blk_rings = &ring->blk_rings;
1190         struct blkif_request req;
1191         struct pending_req *pending_req;
1192         RING_IDX rc, rp;
1193         int more_to_do = 0;
1194
1195         rc = blk_rings->common.req_cons;
1196         rp = blk_rings->common.sring->req_prod;
1197         rmb(); /* Ensure we see queued requests up to 'rp'. */
1198
1199         if (RING_REQUEST_PROD_OVERFLOW(&blk_rings->common, rp)) {
1200                 rc = blk_rings->common.rsp_prod_pvt;
1201                 pr_warn("Frontend provided bogus ring requests (%d - %d = %d). Halting ring processing on dev=%04x\n",
1202                         rp, rc, rp - rc, ring->blkif->vbd.pdevice);
1203                 return -EACCES;
1204         }
1205         while (rc != rp) {
1206
1207                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
1208                         break;
1209
1210                 /* We've seen a request, so clear spurious eoi flag. */
1211                 *eoi_flags &= ~XEN_EOI_FLAG_SPURIOUS;
1212
1213                 if (kthread_should_stop()) {
1214                         more_to_do = 1;
1215                         break;
1216                 }
1217
1218                 pending_req = alloc_req(ring);
1219                 if (NULL == pending_req) {
1220                         ring->st_oo_req++;
1221                         more_to_do = 1;
1222                         break;
1223                 }
1224
1225                 switch (ring->blkif->blk_protocol) {
1226                 case BLKIF_PROTOCOL_NATIVE:
1227                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
1228                         break;
1229                 case BLKIF_PROTOCOL_X86_32:
1230                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
1231                         break;
1232                 case BLKIF_PROTOCOL_X86_64:
1233                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
1234                         break;
1235                 default:
1236                         BUG();
1237                 }
1238                 blk_rings->common.req_cons = ++rc; /* before make_response() */
1239
1240                 /* Apply all sanity checks to /private copy/ of request. */
1241                 barrier();
1242
1243                 switch (req.operation) {
1244                 case BLKIF_OP_READ:
1245                 case BLKIF_OP_WRITE:
1246                 case BLKIF_OP_WRITE_BARRIER:
1247                 case BLKIF_OP_FLUSH_DISKCACHE:
1248                 case BLKIF_OP_INDIRECT:
1249                         if (dispatch_rw_block_io(ring, &req, pending_req))
1250                                 goto done;
1251                         break;
1252                 case BLKIF_OP_DISCARD:
1253                         free_req(ring, pending_req);
1254                         if (dispatch_discard_io(ring, &req))
1255                                 goto done;
1256                         break;
1257                 default:
1258                         if (dispatch_other_io(ring, &req, pending_req))
1259                                 goto done;
1260                         break;
1261                 }
1262
1263                 /* Yield point for this unbounded loop. */
1264                 cond_resched();
1265         }
1266 done:
1267         return more_to_do;
1268 }
1269
1270 static int
1271 do_block_io_op(struct xen_blkif_ring *ring, unsigned int *eoi_flags)
1272 {
1273         union blkif_back_rings *blk_rings = &ring->blk_rings;
1274         int more_to_do;
1275
1276         do {
1277                 more_to_do = __do_block_io_op(ring, eoi_flags);
1278                 if (more_to_do)
1279                         break;
1280
1281                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
1282         } while (more_to_do);
1283
1284         return more_to_do;
1285 }
1286 /*
1287  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
1288  * and call the 'submit_bio' to pass it to the underlying storage.
1289  */
1290 static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
1291                                 struct blkif_request *req,
1292                                 struct pending_req *pending_req)
1293 {
1294         struct phys_req preq;
1295         struct seg_buf *seg = pending_req->seg;
1296         unsigned int nseg;
1297         struct bio *bio = NULL;
1298         struct bio **biolist = pending_req->biolist;
1299         int i, nbio = 0;
1300         enum req_op operation;
1301         blk_opf_t operation_flags = 0;
1302         struct blk_plug plug;
1303         bool drain = false;
1304         struct grant_page **pages = pending_req->segments;
1305         unsigned short req_operation;
1306
1307         req_operation = req->operation == BLKIF_OP_INDIRECT ?
1308                         req->u.indirect.indirect_op : req->operation;
1309
1310         if ((req->operation == BLKIF_OP_INDIRECT) &&
1311             (req_operation != BLKIF_OP_READ) &&
1312             (req_operation != BLKIF_OP_WRITE)) {
1313                 pr_debug("Invalid indirect operation (%u)\n", req_operation);
1314                 goto fail_response;
1315         }
1316
1317         switch (req_operation) {
1318         case BLKIF_OP_READ:
1319                 ring->st_rd_req++;
1320                 operation = REQ_OP_READ;
1321                 break;
1322         case BLKIF_OP_WRITE:
1323                 ring->st_wr_req++;
1324                 operation = REQ_OP_WRITE;
1325                 operation_flags = REQ_SYNC | REQ_IDLE;
1326                 break;
1327         case BLKIF_OP_WRITE_BARRIER:
1328                 drain = true;
1329                 fallthrough;
1330         case BLKIF_OP_FLUSH_DISKCACHE:
1331                 ring->st_f_req++;
1332                 operation = REQ_OP_WRITE;
1333                 operation_flags = REQ_PREFLUSH;
1334                 break;
1335         default:
1336                 operation = 0; /* make gcc happy */
1337                 goto fail_response;
1338                 break;
1339         }
1340
1341         /* Check that the number of segments is sane. */
1342         nseg = req->operation == BLKIF_OP_INDIRECT ?
1343                req->u.indirect.nr_segments : req->u.rw.nr_segments;
1344
1345         if (unlikely(nseg == 0 && operation_flags != REQ_PREFLUSH) ||
1346             unlikely((req->operation != BLKIF_OP_INDIRECT) &&
1347                      (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) ||
1348             unlikely((req->operation == BLKIF_OP_INDIRECT) &&
1349                      (nseg > MAX_INDIRECT_SEGMENTS))) {
1350                 pr_debug("Bad number of segments in request (%d)\n", nseg);
1351                 /* Haven't submitted any bio's yet. */
1352                 goto fail_response;
1353         }
1354
1355         preq.nr_sects      = 0;
1356
1357         pending_req->ring      = ring;
1358         pending_req->id        = req->u.rw.id;
1359         pending_req->operation = req_operation;
1360         pending_req->status    = BLKIF_RSP_OKAY;
1361         pending_req->nr_segs   = nseg;
1362
1363         if (req->operation != BLKIF_OP_INDIRECT) {
1364                 preq.dev               = req->u.rw.handle;
1365                 preq.sector_number     = req->u.rw.sector_number;
1366                 for (i = 0; i < nseg; i++) {
1367                         pages[i]->gref = req->u.rw.seg[i].gref;
1368                         seg[i].nsec = req->u.rw.seg[i].last_sect -
1369                                 req->u.rw.seg[i].first_sect + 1;
1370                         seg[i].offset = (req->u.rw.seg[i].first_sect << 9);
1371                         if ((req->u.rw.seg[i].last_sect >= (XEN_PAGE_SIZE >> 9)) ||
1372                             (req->u.rw.seg[i].last_sect <
1373                              req->u.rw.seg[i].first_sect))
1374                                 goto fail_response;
1375                         preq.nr_sects += seg[i].nsec;
1376                 }
1377         } else {
1378                 preq.dev               = req->u.indirect.handle;
1379                 preq.sector_number     = req->u.indirect.sector_number;
1380                 if (xen_blkbk_parse_indirect(req, pending_req, seg, &preq))
1381                         goto fail_response;
1382         }
1383
1384         if (xen_vbd_translate(&preq, ring->blkif, operation) != 0) {
1385                 pr_debug("access denied: %s of [%llu,%llu] on dev=%04x\n",
1386                          operation == REQ_OP_READ ? "read" : "write",
1387                          preq.sector_number,
1388                          preq.sector_number + preq.nr_sects,
1389                          ring->blkif->vbd.pdevice);
1390                 goto fail_response;
1391         }
1392
1393         /*
1394          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
1395          * is set there.
1396          */
1397         for (i = 0; i < nseg; i++) {
1398                 if (((int)preq.sector_number|(int)seg[i].nsec) &
1399                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
1400                         pr_debug("Misaligned I/O request from domain %d\n",
1401                                  ring->blkif->domid);
1402                         goto fail_response;
1403                 }
1404         }
1405
1406         /* Wait on all outstanding I/O's and once that has been completed
1407          * issue the flush.
1408          */
1409         if (drain)
1410                 xen_blk_drain_io(pending_req->ring);
1411
1412         /*
1413          * If we have failed at this point, we need to undo the M2P override,
1414          * set gnttab_set_unmap_op on all of the grant references and perform
1415          * the hypercall to unmap the grants - that is all done in
1416          * xen_blkbk_unmap.
1417          */
1418         if (xen_blkbk_map_seg(pending_req))
1419                 goto fail_flush;
1420
1421         /*
1422          * This corresponding xen_blkif_put is done in __end_block_io_op, or
1423          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
1424          */
1425         xen_blkif_get(ring->blkif);
1426         atomic_inc(&ring->inflight);
1427
1428         for (i = 0; i < nseg; i++) {
1429                 while ((bio == NULL) ||
1430                        (bio_add_page(bio,
1431                                      pages[i]->page,
1432                                      seg[i].nsec << 9,
1433                                      seg[i].offset) == 0)) {
1434                         bio = bio_alloc(preq.bdev, bio_max_segs(nseg - i),
1435                                         operation | operation_flags,
1436                                         GFP_KERNEL);
1437                         biolist[nbio++] = bio;
1438                         bio->bi_private = pending_req;
1439                         bio->bi_end_io  = end_block_io_op;
1440                         bio->bi_iter.bi_sector  = preq.sector_number;
1441                 }
1442
1443                 preq.sector_number += seg[i].nsec;
1444         }
1445
1446         /* This will be hit if the operation was a flush or discard. */
1447         if (!bio) {
1448                 BUG_ON(operation_flags != REQ_PREFLUSH);
1449
1450                 bio = bio_alloc(preq.bdev, 0, operation | operation_flags,
1451                                 GFP_KERNEL);
1452                 biolist[nbio++] = bio;
1453                 bio->bi_private = pending_req;
1454                 bio->bi_end_io  = end_block_io_op;
1455         }
1456
1457         atomic_set(&pending_req->pendcnt, nbio);
1458         blk_start_plug(&plug);
1459
1460         for (i = 0; i < nbio; i++)
1461                 submit_bio(biolist[i]);
1462
1463         /* Let the I/Os go.. */
1464         blk_finish_plug(&plug);
1465
1466         if (operation == REQ_OP_READ)
1467                 ring->st_rd_sect += preq.nr_sects;
1468         else if (operation == REQ_OP_WRITE)
1469                 ring->st_wr_sect += preq.nr_sects;
1470
1471         return 0;
1472
1473  fail_flush:
1474         xen_blkbk_unmap(ring, pending_req->segments,
1475                         pending_req->nr_segs);
1476  fail_response:
1477         /* Haven't submitted any bio's yet. */
1478         make_response(ring, req->u.rw.id, req_operation, BLKIF_RSP_ERROR);
1479         free_req(ring, pending_req);
1480         msleep(1); /* back off a bit */
1481         return -EIO;
1482 }
1483
1484
1485
1486 /*
1487  * Put a response on the ring on how the operation fared.
1488  */
1489 static void make_response(struct xen_blkif_ring *ring, u64 id,
1490                           unsigned short op, int st)
1491 {
1492         struct blkif_response *resp;
1493         unsigned long     flags;
1494         union blkif_back_rings *blk_rings;
1495         int notify;
1496
1497         spin_lock_irqsave(&ring->blk_ring_lock, flags);
1498         blk_rings = &ring->blk_rings;
1499         /* Place on the response ring for the relevant domain. */
1500         switch (ring->blkif->blk_protocol) {
1501         case BLKIF_PROTOCOL_NATIVE:
1502                 resp = RING_GET_RESPONSE(&blk_rings->native,
1503                                          blk_rings->native.rsp_prod_pvt);
1504                 break;
1505         case BLKIF_PROTOCOL_X86_32:
1506                 resp = RING_GET_RESPONSE(&blk_rings->x86_32,
1507                                          blk_rings->x86_32.rsp_prod_pvt);
1508                 break;
1509         case BLKIF_PROTOCOL_X86_64:
1510                 resp = RING_GET_RESPONSE(&blk_rings->x86_64,
1511                                          blk_rings->x86_64.rsp_prod_pvt);
1512                 break;
1513         default:
1514                 BUG();
1515         }
1516
1517         resp->id        = id;
1518         resp->operation = op;
1519         resp->status    = st;
1520
1521         blk_rings->common.rsp_prod_pvt++;
1522         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1523         spin_unlock_irqrestore(&ring->blk_ring_lock, flags);
1524         if (notify)
1525                 notify_remote_via_irq(ring->irq);
1526 }
1527
1528 static int __init xen_blkif_init(void)
1529 {
1530         int rc = 0;
1531
1532         if (!xen_domain())
1533                 return -ENODEV;
1534
1535         if (xen_blkif_max_ring_order > XENBUS_MAX_RING_GRANT_ORDER) {
1536                 pr_info("Invalid max_ring_order (%d), will use default max: %d.\n",
1537                         xen_blkif_max_ring_order, XENBUS_MAX_RING_GRANT_ORDER);
1538                 xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
1539         }
1540
1541         if (xenblk_max_queues == 0)
1542                 xenblk_max_queues = num_online_cpus();
1543
1544         rc = xen_blkif_interface_init();
1545         if (rc)
1546                 goto failed_init;
1547
1548         rc = xen_blkif_xenbus_init();
1549         if (rc)
1550                 goto failed_init;
1551
1552  failed_init:
1553         return rc;
1554 }
1555
1556 module_init(xen_blkif_init);
1557
1558 static void __exit xen_blkif_fini(void)
1559 {
1560         xen_blkif_xenbus_fini();
1561         xen_blkif_interface_fini();
1562 }
1563
1564 module_exit(xen_blkif_fini);
1565
1566 MODULE_LICENSE("Dual BSD/GPL");
1567 MODULE_ALIAS("xen-backend:vbd");