drivers/block/xen-blkback/blkback.c

   1 /******************************************************************************
   2  *
   3  * Back-end of the driver for virtual block devices. This portion of the
   4  * driver exports a 'unified' block-device interface that can be accessed
   5  * by any operating system that implements a compatible front end. A
   6  * reference front-end implementation can be found in:
   7  *  drivers/block/xen-blkfront.c
   8  *
   9  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
  10  * Copyright (c) 2005, Christopher Clark
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License version 2
  14  * as published by the Free Software Foundation; or, when distributed
  15  * separately from the Linux kernel or incorporated into other
  16  * software packages, subject to the following license:
  17  *
  18  * Permission is hereby granted, free of charge, to any person obtaining a copy
  19  * of this source file (the "Software"), to deal in the Software without
  20  * restriction, including without limitation the rights to use, copy, modify,
  21  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  22  * and to permit persons to whom the Software is furnished to do so, subject to
  23  * the following conditions:
  24  *
  25  * The above copyright notice and this permission notice shall be included in
  26  * all copies or substantial portions of the Software.
  27  *
  28  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  29  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  30  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  31  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  32  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  33  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  34  * IN THE SOFTWARE.
  35  */
  36
  37 #include <linux/spinlock.h>
  38 #include <linux/kthread.h>
  39 #include <linux/list.h>
  40 #include <linux/delay.h>
  41 #include <linux/freezer.h>
  42 #include <linux/bitmap.h>
  43
  44 #include <xen/events.h>
  45 #include <xen/page.h>
  46 #include <xen/xen.h>
  47 #include <asm/xen/hypervisor.h>
  48 #include <asm/xen/hypercall.h>
  49 #include "common.h"
  50
  51 /*
  52  * These are rather arbitrary. They are fairly large because adjacent requests
  53  * pulled from a communication ring are quite likely to end up being part of
  54  * the same scatter/gather request at the disc.
  55  *
  56  * ** TRY INCREASING 'xen_blkif_reqs' IF WRITE SPEEDS SEEM TOO LOW **
  57  *
  58  * This will increase the chances of being able to write whole tracks.
  59  * 64 should be enough to keep us competitive with Linux.
  60  */
  61 static int xen_blkif_reqs = 64;
  62 module_param_named(reqs, xen_blkif_reqs, int, 0);
  63 MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate");
  64
  65 /* Run-time switchable: /sys/module/blkback/parameters/ */
  66 static unsigned int log_stats;
  67 module_param(log_stats, int, 0644);
  68
  69 /*
  70  * Each outstanding request that we've passed to the lower device layers has a
  71  * 'pending_req' allocated to it. Each buffer_head that completes decrements
  72  * the pendcnt towards zero. When it hits zero, the specified domain has a
  73  * response queued for it, with the saved 'id' passed back.
  74  */
  75 struct pending_req {
  76         struct xen_blkif        *blkif;
  77         u64                     id;
  78         int                     nr_pages;
  79         atomic_t                pendcnt;
  80         unsigned short          operation;
  81         int                     status;
  82         struct list_head        free_list;
  83         DECLARE_BITMAP(unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
  84 };
  85
  86 #define BLKBACK_INVALID_HANDLE (~0)
  87
  88 struct xen_blkbk {
  89         struct pending_req      *pending_reqs;
  90         /* List of all 'pending_req' available */
  91         struct list_head        pending_free;
  92         /* And its spinlock. */
  93         spinlock_t              pending_free_lock;
  94         wait_queue_head_t       pending_free_wq;
  95         /* The list of all pages that are available. */
  96         struct page             **pending_pages;
  97         /* And the grant handles that are available. */
  98         grant_handle_t          *pending_grant_handles;
  99 };
 100
 101 static struct xen_blkbk *blkbk;
 102
 103 /*
 104  * Maximum number of grant pages that can be mapped in blkback.
 105  * BLKIF_MAX_SEGMENTS_PER_REQUEST * RING_SIZE is the maximum number of
 106  * pages that blkback will persistently map.
 107  * Currently, this is:
 108  * RING_SIZE = 32 (for all known ring types)
 109  * BLKIF_MAX_SEGMENTS_PER_REQUEST = 11
 110  * sizeof(struct persistent_gnt) = 48
 111  * So the maximum memory used to store the grants is:
 112  * 32 * 11 * 48 = 16896 bytes
 113  */
 114 static inline unsigned int max_mapped_grant_pages(enum blkif_protocol protocol)
 115 {
 116         switch (protocol) {
 117         case BLKIF_PROTOCOL_NATIVE:
 118                 return __CONST_RING_SIZE(blkif, PAGE_SIZE) *
 119                            BLKIF_MAX_SEGMENTS_PER_REQUEST;
 120         case BLKIF_PROTOCOL_X86_32:
 121                 return __CONST_RING_SIZE(blkif_x86_32, PAGE_SIZE) *
 122                            BLKIF_MAX_SEGMENTS_PER_REQUEST;
 123         case BLKIF_PROTOCOL_X86_64:
 124                 return __CONST_RING_SIZE(blkif_x86_64, PAGE_SIZE) *
 125                            BLKIF_MAX_SEGMENTS_PER_REQUEST;
 126         default:
 127                 BUG();
 128         }
 129         return 0;
 130 }
 131
 132
 133 /*
 134  * Little helpful macro to figure out the index and virtual address of the
 135  * pending_pages[..]. For each 'pending_req' we have have up to
 136  * BLKIF_MAX_SEGMENTS_PER_REQUEST (11) pages. The seg would be from 0 through
 137  * 10 and would index in the pending_pages[..].
 138  */
 139 static inline int vaddr_pagenr(struct pending_req *req, int seg)
 140 {
 141         return (req - blkbk->pending_reqs) *
 142                 BLKIF_MAX_SEGMENTS_PER_REQUEST + seg;
 143 }
 144
 145 #define pending_page(req, seg) pending_pages[vaddr_pagenr(req, seg)]
 146
 147 static inline unsigned long vaddr(struct pending_req *req, int seg)
 148 {
 149         unsigned long pfn = page_to_pfn(blkbk->pending_page(req, seg));
 150         return (unsigned long)pfn_to_kaddr(pfn);
 151 }
 152
 153 #define pending_handle(_req, _seg) \
 154         (blkbk->pending_grant_handles[vaddr_pagenr(_req, _seg)])
 155
 156
 157 static int do_block_io_op(struct xen_blkif *blkif);
 158 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 159                                 struct blkif_request *req,
 160                                 struct pending_req *pending_req);
 161 static void make_response(struct xen_blkif *blkif, u64 id,
 162                           unsigned short op, int st);
 163
 164 #define foreach_grant(pos, rbtree, node) \
 165         for ((pos) = container_of(rb_first((rbtree)), typeof(*(pos)), node); \
 166              &(pos)->node != NULL; \
 167              (pos) = container_of(rb_next(&(pos)->node), typeof(*(pos)), node))
 168
 169
 170 static void add_persistent_gnt(struct rb_root *root,
 171                                struct persistent_gnt *persistent_gnt)
 172 {
 173         struct rb_node **new = &(root->rb_node), *parent = NULL;
 174         struct persistent_gnt *this;
 175
 176         /* Figure out where to put new node */
 177         while (*new) {
 178                 this = container_of(*new, struct persistent_gnt, node);
 179
 180                 parent = *new;
 181                 if (persistent_gnt->gnt < this->gnt)
 182                         new = &((*new)->rb_left);
 183                 else if (persistent_gnt->gnt > this->gnt)
 184                         new = &((*new)->rb_right);
 185                 else {
 186                         pr_alert(DRV_PFX " trying to add a gref that's already in the tree\n");
 187                         BUG();
 188                 }
 189         }
 190
 191         /* Add new node and rebalance tree. */
 192         rb_link_node(&(persistent_gnt->node), parent, new);
 193         rb_insert_color(&(persistent_gnt->node), root);
 194 }
 195
 196 static struct persistent_gnt *get_persistent_gnt(struct rb_root *root,
 197                                                  grant_ref_t gref)
 198 {
 199         struct persistent_gnt *data;
 200         struct rb_node *node = root->rb_node;
 201
 202         while (node) {
 203                 data = container_of(node, struct persistent_gnt, node);
 204
 205                 if (gref < data->gnt)
 206                         node = node->rb_left;
 207                 else if (gref > data->gnt)
 208                         node = node->rb_right;
 209                 else
 210                         return data;
 211         }
 212         return NULL;
 213 }
 214
 215 static void free_persistent_gnts(struct rb_root *root, unsigned int num)
 216 {
 217         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 218         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 219         struct persistent_gnt *persistent_gnt;
 220         int ret = 0;
 221         int segs_to_unmap = 0;
 222
 223         foreach_grant(persistent_gnt, root, node) {
 224                 BUG_ON(persistent_gnt->handle ==
 225                         BLKBACK_INVALID_HANDLE);
 226                 gnttab_set_unmap_op(&unmap[segs_to_unmap],
 227                         (unsigned long) pfn_to_kaddr(page_to_pfn(
 228                                 persistent_gnt->page)),
 229                         GNTMAP_host_map,
 230                         persistent_gnt->handle);
 231
 232                 pages[segs_to_unmap] = persistent_gnt->page;
 233                 rb_erase(&persistent_gnt->node, root);
 234                 kfree(persistent_gnt);
 235                 num--;
 236
 237                 if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST ||
 238                         !rb_next(&persistent_gnt->node)) {
 239                         ret = gnttab_unmap_refs(unmap, NULL, pages,
 240                                 segs_to_unmap);
 241                         BUG_ON(ret);
 242                         segs_to_unmap = 0;
 243                 }
 244         }
 245         BUG_ON(num != 0);
 246 }
 247
 248 /*
 249  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 250  */
 251 static struct pending_req *alloc_req(void)
 252 {
 253         struct pending_req *req = NULL;
 254         unsigned long flags;
 255
 256         spin_lock_irqsave(&blkbk->pending_free_lock, flags);
 257         if (!list_empty(&blkbk->pending_free)) {
 258                 req = list_entry(blkbk->pending_free.next, struct pending_req,
 259                                  free_list);
 260                 list_del(&req->free_list);
 261         }
 262         spin_unlock_irqrestore(&blkbk->pending_free_lock, flags);
 263         return req;
 264 }
 265
 266 /*
 267  * Return the 'pending_req' structure back to the freepool. We also
 268  * wake up the thread if it was waiting for a free page.
 269  */
 270 static void free_req(struct pending_req *req)
 271 {
 272         unsigned long flags;
 273         int was_empty;
 274
 275         spin_lock_irqsave(&blkbk->pending_free_lock, flags);
 276         was_empty = list_empty(&blkbk->pending_free);
 277         list_add(&req->free_list, &blkbk->pending_free);
 278         spin_unlock_irqrestore(&blkbk->pending_free_lock, flags);
 279         if (was_empty)
 280                 wake_up(&blkbk->pending_free_wq);
 281 }
 282
 283 /*
 284  * Routines for managing virtual block devices (vbds).
 285  */
 286 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 287                              int operation)
 288 {
 289         struct xen_vbd *vbd = &blkif->vbd;
 290         int rc = -EACCES;
 291
 292         if ((operation != READ) && vbd->readonly)
 293                 goto out;
 294
 295         if (likely(req->nr_sects)) {
 296                 blkif_sector_t end = req->sector_number + req->nr_sects;
 297
 298                 if (unlikely(end < req->sector_number))
 299                         goto out;
 300                 if (unlikely(end > vbd_sz(vbd)))
 301                         goto out;
 302         }
 303
 304         req->dev  = vbd->pdevice;
 305         req->bdev = vbd->bdev;
 306         rc = 0;
 307
 308  out:
 309         return rc;
 310 }
 311
 312 static void xen_vbd_resize(struct xen_blkif *blkif)
 313 {
 314         struct xen_vbd *vbd = &blkif->vbd;
 315         struct xenbus_transaction xbt;
 316         int err;
 317         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 318         unsigned long long new_size = vbd_sz(vbd);
 319
 320         pr_info(DRV_PFX "VBD Resize: Domid: %d, Device: (%d, %d)\n",
 321                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 322         pr_info(DRV_PFX "VBD Resize: new size %llu\n", new_size);
 323         vbd->size = new_size;
 324 again:
 325         err = xenbus_transaction_start(&xbt);
 326         if (err) {
 327                 pr_warn(DRV_PFX "Error starting transaction");
 328                 return;
 329         }
 330         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 331                             (unsigned long long)vbd_sz(vbd));
 332         if (err) {
 333                 pr_warn(DRV_PFX "Error writing new size");
 334                 goto abort;
 335         }
 336         /*
 337          * Write the current state; we will use this to synchronize
 338          * the front-end. If the current state is "connected" the
 339          * front-end will get the new size information online.
 340          */
 341         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 342         if (err) {
 343                 pr_warn(DRV_PFX "Error writing the state");
 344                 goto abort;
 345         }
 346
 347         err = xenbus_transaction_end(xbt, 0);
 348         if (err == -EAGAIN)
 349                 goto again;
 350         if (err)
 351                 pr_warn(DRV_PFX "Error ending transaction");
 352         return;
 353 abort:
 354         xenbus_transaction_end(xbt, 1);
 355 }
 356
 357 /*
 358  * Notification from the guest OS.
 359  */
 360 static void blkif_notify_work(struct xen_blkif *blkif)
 361 {
 362         blkif->waiting_reqs = 1;
 363         wake_up(&blkif->wq);
 364 }
 365
 366 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 367 {
 368         blkif_notify_work(dev_id);
 369         return IRQ_HANDLED;
 370 }
 371
 372 /*
 373  * SCHEDULER FUNCTIONS
 374  */
 375
 376 static void print_stats(struct xen_blkif *blkif)
 377 {
 378         pr_info("xen-blkback (%s): oo %3d  |  rd %4d  |  wr %4d  |  f %4d"
 379                  "  |  ds %4d\n",
 380                  current->comm, blkif->st_oo_req,
 381                  blkif->st_rd_req, blkif->st_wr_req,
 382                  blkif->st_f_req, blkif->st_ds_req);
 383         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 384         blkif->st_rd_req = 0;
 385         blkif->st_wr_req = 0;
 386         blkif->st_oo_req = 0;
 387         blkif->st_ds_req = 0;
 388 }
 389
 390 int xen_blkif_schedule(void *arg)
 391 {
 392         struct xen_blkif *blkif = arg;
 393         struct xen_vbd *vbd = &blkif->vbd;
 394
 395         xen_blkif_get(blkif);
 396
 397         while (!kthread_should_stop()) {
 398                 if (try_to_freeze())
 399                         continue;
 400                 if (unlikely(vbd->size != vbd_sz(vbd)))
 401                         xen_vbd_resize(blkif);
 402
 403                 wait_event_interruptible(
 404                         blkif->wq,
 405                         blkif->waiting_reqs || kthread_should_stop());
 406                 wait_event_interruptible(
 407                         blkbk->pending_free_wq,
 408                         !list_empty(&blkbk->pending_free) ||
 409                         kthread_should_stop());
 410
 411                 blkif->waiting_reqs = 0;
 412                 smp_mb(); /* clear flag *before* checking for work */
 413
 414                 if (do_block_io_op(blkif))
 415                         blkif->waiting_reqs = 1;
 416
 417                 if (log_stats && time_after(jiffies, blkif->st_print))
 418                         print_stats(blkif);
 419         }
 420
 421         /* Free all persistent grant pages */
 422         if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
 423                 free_persistent_gnts(&blkif->persistent_gnts,
 424                         blkif->persistent_gnt_c);
 425
 426         BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 427         blkif->persistent_gnt_c = 0;
 428
 429         if (log_stats)
 430                 print_stats(blkif);
 431
 432         blkif->xenblkd = NULL;
 433         xen_blkif_put(blkif);
 434
 435         return 0;
 436 }
 437
 438 struct seg_buf {
 439         unsigned long buf;
 440         unsigned int nsec;
 441 };
 442 /*
 443  * Unmap the grant references, and also remove the M2P over-rides
 444  * used in the 'pending_req'.
 445  */
 446 static void xen_blkbk_unmap(struct pending_req *req)
 447 {
 448         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 449         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 450         unsigned int i, invcount = 0;
 451         grant_handle_t handle;
 452         int ret;
 453
 454         for (i = 0; i < req->nr_pages; i++) {
 455                 if (!test_bit(i, req->unmap_seg))
 456                         continue;
 457                 handle = pending_handle(req, i);
 458                 if (handle == BLKBACK_INVALID_HANDLE)
 459                         continue;
 460                 gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
 461                                     GNTMAP_host_map, handle);
 462                 pending_handle(req, i) = BLKBACK_INVALID_HANDLE;
 463                 pages[invcount] = virt_to_page(vaddr(req, i));
 464                 invcount++;
 465         }
 466
 467         ret = gnttab_unmap_refs(unmap, NULL, pages, invcount);
 468         BUG_ON(ret);
 469 }
 470
 471 static int xen_blkbk_map(struct blkif_request *req,
 472                          struct pending_req *pending_req,
 473                          struct seg_buf seg[],
 474                          struct page *pages[])
 475 {
 476         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 477         struct persistent_gnt *persistent_gnts[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 478         struct page *pages_to_gnt[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 479         struct persistent_gnt *persistent_gnt = NULL;
 480         struct xen_blkif *blkif = pending_req->blkif;
 481         phys_addr_t addr = 0;
 482         int i, j;
 483         bool new_map;
 484         int nseg = req->u.rw.nr_segments;
 485         int segs_to_map = 0;
 486         int ret = 0;
 487         int use_persistent_gnts;
 488
 489         use_persistent_gnts = (blkif->vbd.feature_gnt_persistent);
 490
 491         BUG_ON(blkif->persistent_gnt_c >
 492                    max_mapped_grant_pages(pending_req->blkif->blk_protocol));
 493
 494         /*
 495          * Fill out preq.nr_sects with proper amount of sectors, and setup
 496          * assign map[..] with the PFN of the page in our domain with the
 497          * corresponding grant reference for each page.
 498          */
 499         for (i = 0; i < nseg; i++) {
 500                 uint32_t flags;
 501
 502                 if (use_persistent_gnts)
 503                         persistent_gnt = get_persistent_gnt(
 504                                 &blkif->persistent_gnts,
 505                                 req->u.rw.seg[i].gref);
 506
 507                 if (persistent_gnt) {
 508                         /*
 509                          * We are using persistent grants and
 510                          * the grant is already mapped
 511                          */
 512                         new_map = false;
 513                 } else if (use_persistent_gnts &&
 514                            blkif->persistent_gnt_c <
 515                            max_mapped_grant_pages(blkif->blk_protocol)) {
 516                         /*
 517                          * We are using persistent grants, the grant is
 518                          * not mapped but we have room for it
 519                          */
 520                         new_map = true;
 521                         persistent_gnt = kmalloc(
 522                                 sizeof(struct persistent_gnt),
 523                                 GFP_KERNEL);
 524                         if (!persistent_gnt)
 525                                 return -ENOMEM;
 526                         persistent_gnt->page = alloc_page(GFP_KERNEL);
 527                         if (!persistent_gnt->page) {
 528                                 kfree(persistent_gnt);
 529                                 return -ENOMEM;
 530                         }
 531                         persistent_gnt->gnt = req->u.rw.seg[i].gref;
 532                         persistent_gnt->handle = BLKBACK_INVALID_HANDLE;
 533
 534                         pages_to_gnt[segs_to_map] =
 535                                 persistent_gnt->page;
 536                         addr = (unsigned long) pfn_to_kaddr(
 537                                 page_to_pfn(persistent_gnt->page));
 538
 539                         add_persistent_gnt(&blkif->persistent_gnts,
 540                                 persistent_gnt);
 541                         blkif->persistent_gnt_c++;
 542                         pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n",
 543                                  persistent_gnt->gnt, blkif->persistent_gnt_c,
 544                                  max_mapped_grant_pages(blkif->blk_protocol));
 545                 } else {
 546                         /*
 547                          * We are either using persistent grants and
 548                          * hit the maximum limit of grants mapped,
 549                          * or we are not using persistent grants.
 550                          */
 551                         if (use_persistent_gnts &&
 552                                 !blkif->vbd.overflow_max_grants) {
 553                                 blkif->vbd.overflow_max_grants = 1;
 554                                 pr_alert(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n",
 555                                          blkif->domid, blkif->vbd.handle);
 556                         }
 557                         new_map = true;
 558                         pages[i] = blkbk->pending_page(pending_req, i);
 559                         addr = vaddr(pending_req, i);
 560                         pages_to_gnt[segs_to_map] =
 561                                 blkbk->pending_page(pending_req, i);
 562                 }
 563
 564                 if (persistent_gnt) {
 565                         pages[i] = persistent_gnt->page;
 566                         persistent_gnts[i] = persistent_gnt;
 567                 } else {
 568                         persistent_gnts[i] = NULL;
 569                 }
 570
 571                 if (new_map) {
 572                         flags = GNTMAP_host_map;
 573                         if (!persistent_gnt &&
 574                             (pending_req->operation != BLKIF_OP_READ))
 575                                 flags |= GNTMAP_readonly;
 576                         gnttab_set_map_op(&map[segs_to_map++], addr,
 577                                           flags, req->u.rw.seg[i].gref,
 578                                           blkif->domid);
 579                 }
 580         }
 581
 582         if (segs_to_map) {
 583                 ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
 584                 BUG_ON(ret);
 585         }
 586
 587         /*
 588          * Now swizzle the MFN in our domain with the MFN from the other domain
 589          * so that when we access vaddr(pending_req,i) it has the contents of
 590          * the page from the other domain.
 591          */
 592         bitmap_zero(pending_req->unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
 593         for (i = 0, j = 0; i < nseg; i++) {
 594                 if (!persistent_gnts[i] ||
 595                     persistent_gnts[i]->handle == BLKBACK_INVALID_HANDLE) {
 596                         /* This is a newly mapped grant */
 597                         BUG_ON(j >= segs_to_map);
 598                         if (unlikely(map[j].status != 0)) {
 599                                 pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
 600                                 map[j].handle = BLKBACK_INVALID_HANDLE;
 601                                 ret |= 1;
 602                                 if (persistent_gnts[i]) {
 603                                         rb_erase(&persistent_gnts[i]->node,
 604                                                  &blkif->persistent_gnts);
 605                                         blkif->persistent_gnt_c--;
 606                                         kfree(persistent_gnts[i]);
 607                                         persistent_gnts[i] = NULL;
 608                                 }
 609                         }
 610                 }
 611                 if (persistent_gnts[i]) {
 612                         if (persistent_gnts[i]->handle ==
 613                             BLKBACK_INVALID_HANDLE) {
 614                                 /*
 615                                  * If this is a new persistent grant
 616                                  * save the handler
 617                                  */
 618                                 persistent_gnts[i]->handle = map[j].handle;
 619                                 persistent_gnts[i]->dev_bus_addr =
 620                                         map[j++].dev_bus_addr;
 621                         }
 622                         pending_handle(pending_req, i) =
 623                                 persistent_gnts[i]->handle;
 624
 625                         if (ret)
 626                                 continue;
 627
 628                         seg[i].buf = persistent_gnts[i]->dev_bus_addr |
 629                                 (req->u.rw.seg[i].first_sect << 9);
 630                 } else {
 631                         pending_handle(pending_req, i) = map[j].handle;
 632                         bitmap_set(pending_req->unmap_seg, i, 1);
 633
 634                         if (ret) {
 635                                 j++;
 636                                 continue;
 637                         }
 638
 639                         seg[i].buf = map[j++].dev_bus_addr |
 640                                 (req->u.rw.seg[i].first_sect << 9);
 641                 }
 642         }
 643         return ret;
 644 }
 645
 646 static int dispatch_discard_io(struct xen_blkif *blkif,
 647                                 struct blkif_request *req)
 648 {
 649         int err = 0;
 650         int status = BLKIF_RSP_OKAY;
 651         struct block_device *bdev = blkif->vbd.bdev;
 652         unsigned long secure;
 653
 654         blkif->st_ds_req++;
 655
 656         xen_blkif_get(blkif);
 657         secure = (blkif->vbd.discard_secure &&
 658                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
 659                  BLKDEV_DISCARD_SECURE : 0;
 660
 661         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
 662                                    req->u.discard.nr_sectors,
 663                                    GFP_KERNEL, secure);
 664
 665         if (err == -EOPNOTSUPP) {
 666                 pr_debug(DRV_PFX "discard op failed, not supported\n");
 667                 status = BLKIF_RSP_EOPNOTSUPP;
 668         } else if (err)
 669                 status = BLKIF_RSP_ERROR;
 670
 671         make_response(blkif, req->u.discard.id, req->operation, status);
 672         xen_blkif_put(blkif);
 673         return err;
 674 }
 675
 676 static void xen_blk_drain_io(struct xen_blkif *blkif)
 677 {
 678         atomic_set(&blkif->drain, 1);
 679         do {
 680                 /* The initial value is one, and one refcnt taken at the
 681                  * start of the xen_blkif_schedule thread. */
 682                 if (atomic_read(&blkif->refcnt) <= 2)
 683                         break;
 684                 wait_for_completion_interruptible_timeout(
 685                                 &blkif->drain_complete, HZ);
 686
 687                 if (!atomic_read(&blkif->drain))
 688                         break;
 689         } while (!kthread_should_stop());
 690         atomic_set(&blkif->drain, 0);
 691 }
 692
 693 /*
 694  * Completion callback on the bio's. Called as bh->b_end_io()
 695  */
 696
 697 static void __end_block_io_op(struct pending_req *pending_req, int error)
 698 {
 699         /* An error fails the entire request. */
 700         if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
 701             (error == -EOPNOTSUPP)) {
 702                 pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
 703                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
 704                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 705         } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
 706                     (error == -EOPNOTSUPP)) {
 707                 pr_debug(DRV_PFX "write barrier op failed, not supported\n");
 708                 xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
 709                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 710         } else if (error) {
 711                 pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
 712                          " error=%d\n", error);
 713                 pending_req->status = BLKIF_RSP_ERROR;
 714         }
 715
 716         /*
 717          * If all of the bio's have completed it is time to unmap
 718          * the grant references associated with 'request' and provide
 719          * the proper response on the ring.
 720          */
 721         if (atomic_dec_and_test(&pending_req->pendcnt)) {
 722                 xen_blkbk_unmap(pending_req);
 723                 make_response(pending_req->blkif, pending_req->id,
 724                               pending_req->operation, pending_req->status);
 725                 xen_blkif_put(pending_req->blkif);
 726                 if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
 727                         if (atomic_read(&pending_req->blkif->drain))
 728                                 complete(&pending_req->blkif->drain_complete);
 729                 }
 730                 free_req(pending_req);
 731         }
 732 }
 733
 734 /*
 735  * bio callback.
 736  */
 737 static void end_block_io_op(struct bio *bio, int error)
 738 {
 739         __end_block_io_op(bio->bi_private, error);
 740         bio_put(bio);
 741 }
 742
 743
 744
 745 /*
 746  * Function to copy the from the ring buffer the 'struct blkif_request'
 747  * (which has the sectors we want, number of them, grant references, etc),
 748  * and transmute  it to the block API to hand it over to the proper block disk.
 749  */
 750 static int
 751 __do_block_io_op(struct xen_blkif *blkif)
 752 {
 753         union blkif_back_rings *blk_rings = &blkif->blk_rings;
 754         struct blkif_request req;
 755         struct pending_req *pending_req;
 756         RING_IDX rc, rp;
 757         int more_to_do = 0;
 758
 759         rc = blk_rings->common.req_cons;
 760         rp = blk_rings->common.sring->req_prod;
 761         rmb(); /* Ensure we see queued requests up to 'rp'. */
 762
 763         while (rc != rp) {
 764
 765                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
 766                         break;
 767
 768                 if (kthread_should_stop()) {
 769                         more_to_do = 1;
 770                         break;
 771                 }
 772
 773                 pending_req = alloc_req();
 774                 if (NULL == pending_req) {
 775                         blkif->st_oo_req++;
 776                         more_to_do = 1;
 777                         break;
 778                 }
 779
 780                 switch (blkif->blk_protocol) {
 781                 case BLKIF_PROTOCOL_NATIVE:
 782                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
 783                         break;
 784                 case BLKIF_PROTOCOL_X86_32:
 785                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
 786                         break;
 787                 case BLKIF_PROTOCOL_X86_64:
 788                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
 789                         break;
 790                 default:
 791                         BUG();
 792                 }
 793                 blk_rings->common.req_cons = ++rc; /* before make_response() */
 794
 795                 /* Apply all sanity checks to /private copy/ of request. */
 796                 barrier();
 797                 if (unlikely(req.operation == BLKIF_OP_DISCARD)) {
 798                         free_req(pending_req);
 799                         if (dispatch_discard_io(blkif, &req))
 800                                 break;
 801                 } else if (dispatch_rw_block_io(blkif, &req, pending_req))
 802                         break;
 803
 804                 /* Yield point for this unbounded loop. */
 805                 cond_resched();
 806         }
 807
 808         return more_to_do;
 809 }
 810
 811 static int
 812 do_block_io_op(struct xen_blkif *blkif)
 813 {
 814         union blkif_back_rings *blk_rings = &blkif->blk_rings;
 815         int more_to_do;
 816
 817         do {
 818                 more_to_do = __do_block_io_op(blkif);
 819                 if (more_to_do)
 820                         break;
 821
 822                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
 823         } while (more_to_do);
 824
 825         return more_to_do;
 826 }
 827 /*
 828  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
 829  * and call the 'submit_bio' to pass it to the underlying storage.
 830  */
 831 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 832                                 struct blkif_request *req,
 833                                 struct pending_req *pending_req)
 834 {
 835         struct phys_req preq;
 836         struct seg_buf seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 837         unsigned int nseg;
 838         struct bio *bio = NULL;
 839         struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 840         int i, nbio = 0;
 841         int operation;
 842         struct blk_plug plug;
 843         bool drain = false;
 844         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 845
 846         switch (req->operation) {
 847         case BLKIF_OP_READ:
 848                 blkif->st_rd_req++;
 849                 operation = READ;
 850                 break;
 851         case BLKIF_OP_WRITE:
 852                 blkif->st_wr_req++;
 853                 operation = WRITE_ODIRECT;
 854                 break;
 855         case BLKIF_OP_WRITE_BARRIER:
 856                 drain = true;
 857         case BLKIF_OP_FLUSH_DISKCACHE:
 858                 blkif->st_f_req++;
 859                 operation = WRITE_FLUSH;
 860                 break;
 861         default:
 862                 operation = 0; /* make gcc happy */
 863                 goto fail_response;
 864                 break;
 865         }
 866
 867         /* Check that the number of segments is sane. */
 868         nseg = req->u.rw.nr_segments;
 869
 870         if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
 871             unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
 872                 pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
 873                          nseg);
 874                 /* Haven't submitted any bio's yet. */
 875                 goto fail_response;
 876         }
 877
 878         preq.dev           = req->u.rw.handle;
 879         preq.sector_number = req->u.rw.sector_number;
 880         preq.nr_sects      = 0;
 881
 882         pending_req->blkif     = blkif;
 883         pending_req->id        = req->u.rw.id;
 884         pending_req->operation = req->operation;
 885         pending_req->status    = BLKIF_RSP_OKAY;
 886         pending_req->nr_pages  = nseg;
 887
 888         for (i = 0; i < nseg; i++) {
 889                 seg[i].nsec = req->u.rw.seg[i].last_sect -
 890                         req->u.rw.seg[i].first_sect + 1;
 891                 if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
 892                     (req->u.rw.seg[i].last_sect < req->u.rw.seg[i].first_sect))
 893                         goto fail_response;
 894                 preq.nr_sects += seg[i].nsec;
 895
 896         }
 897
 898         if (xen_vbd_translate(&preq, blkif, operation) != 0) {
 899                 pr_debug(DRV_PFX "access denied: %s of [%llu,%llu] on dev=%04x\n",
 900                          operation == READ ? "read" : "write",
 901                          preq.sector_number,
 902                          preq.sector_number + preq.nr_sects, preq.dev);
 903                 goto fail_response;
 904         }
 905
 906         /*
 907          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
 908          * is set there.
 909          */
 910         for (i = 0; i < nseg; i++) {
 911                 if (((int)preq.sector_number|(int)seg[i].nsec) &
 912                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
 913                         pr_debug(DRV_PFX "Misaligned I/O request from domain %d",
 914                                  blkif->domid);
 915                         goto fail_response;
 916                 }
 917         }
 918
 919         /* Wait on all outstanding I/O's and once that has been completed
 920          * issue the WRITE_FLUSH.
 921          */
 922         if (drain)
 923                 xen_blk_drain_io(pending_req->blkif);
 924
 925         /*
 926          * If we have failed at this point, we need to undo the M2P override,
 927          * set gnttab_set_unmap_op on all of the grant references and perform
 928          * the hypercall to unmap the grants - that is all done in
 929          * xen_blkbk_unmap.
 930          */
 931         if (xen_blkbk_map(req, pending_req, seg, pages))
 932                 goto fail_flush;
 933
 934         /*
 935          * This corresponding xen_blkif_put is done in __end_block_io_op, or
 936          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
 937          */
 938         xen_blkif_get(blkif);
 939
 940         for (i = 0; i < nseg; i++) {
 941                 while ((bio == NULL) ||
 942                        (bio_add_page(bio,
 943                                      pages[i],
 944                                      seg[i].nsec << 9,
 945                                      seg[i].buf & ~PAGE_MASK) == 0)) {
 946
 947                         bio = bio_alloc(GFP_KERNEL, nseg-i);
 948                         if (unlikely(bio == NULL))
 949                                 goto fail_put_bio;
 950
 951                         biolist[nbio++] = bio;
 952                         bio->bi_bdev    = preq.bdev;
 953                         bio->bi_private = pending_req;
 954                         bio->bi_end_io  = end_block_io_op;
 955                         bio->bi_sector  = preq.sector_number;
 956                 }
 957
 958                 preq.sector_number += seg[i].nsec;
 959         }
 960
 961         /* This will be hit if the operation was a flush or discard. */
 962         if (!bio) {
 963                 BUG_ON(operation != WRITE_FLUSH);
 964
 965                 bio = bio_alloc(GFP_KERNEL, 0);
 966                 if (unlikely(bio == NULL))
 967                         goto fail_put_bio;
 968
 969                 biolist[nbio++] = bio;
 970                 bio->bi_bdev    = preq.bdev;
 971                 bio->bi_private = pending_req;
 972                 bio->bi_end_io  = end_block_io_op;
 973         }
 974
 975         /*
 976          * We set it one so that the last submit_bio does not have to call
 977          * atomic_inc.
 978          */
 979         atomic_set(&pending_req->pendcnt, nbio);
 980
 981         /* Get a reference count for the disk queue and start sending I/O */
 982         blk_start_plug(&plug);
 983
 984         for (i = 0; i < nbio; i++)
 985                 submit_bio(operation, biolist[i]);
 986
 987         /* Let the I/Os go.. */
 988         blk_finish_plug(&plug);
 989
 990         if (operation == READ)
 991                 blkif->st_rd_sect += preq.nr_sects;
 992         else if (operation & WRITE)
 993                 blkif->st_wr_sect += preq.nr_sects;
 994
 995         return 0;
 996
 997  fail_flush:
 998         xen_blkbk_unmap(pending_req);
 999  fail_response:
1000         /* Haven't submitted any bio's yet. */
1001         make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
1002         free_req(pending_req);
1003         msleep(1); /* back off a bit */
1004         return -EIO;
1005
1006  fail_put_bio:
1007         for (i = 0; i < nbio; i++)
1008                 bio_put(biolist[i]);
1009         __end_block_io_op(pending_req, -EINVAL);
1010         msleep(1); /* back off a bit */
1011         return -EIO;
1012 }
1013
1014
1015
1016 /*
1017  * Put a response on the ring on how the operation fared.
1018  */
1019 static void make_response(struct xen_blkif *blkif, u64 id,
1020                           unsigned short op, int st)
1021 {
1022         struct blkif_response  resp;
1023         unsigned long     flags;
1024         union blkif_back_rings *blk_rings = &blkif->blk_rings;
1025         int notify;
1026
1027         resp.id        = id;
1028         resp.operation = op;
1029         resp.status    = st;
1030
1031         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
1032         /* Place on the response ring for the relevant domain. */
1033         switch (blkif->blk_protocol) {
1034         case BLKIF_PROTOCOL_NATIVE:
1035                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
1036                        &resp, sizeof(resp));
1037                 break;
1038         case BLKIF_PROTOCOL_X86_32:
1039                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
1040                        &resp, sizeof(resp));
1041                 break;
1042         case BLKIF_PROTOCOL_X86_64:
1043                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
1044                        &resp, sizeof(resp));
1045                 break;
1046         default:
1047                 BUG();
1048         }
1049         blk_rings->common.rsp_prod_pvt++;
1050         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
1051         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
1052         if (notify)
1053                 notify_remote_via_irq(blkif->irq);
1054 }
1055
1056 static int __init xen_blkif_init(void)
1057 {
1058         int i, mmap_pages;
1059         int rc = 0;
1060
1061         if (!xen_domain())
1062                 return -ENODEV;
1063
1064         blkbk = kzalloc(sizeof(struct xen_blkbk), GFP_KERNEL);
1065         if (!blkbk) {
1066                 pr_alert(DRV_PFX "%s: out of memory!\n", __func__);
1067                 return -ENOMEM;
1068         }
1069
1070         mmap_pages = xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST;
1071
1072         blkbk->pending_reqs          = kzalloc(sizeof(blkbk->pending_reqs[0]) *
1073                                         xen_blkif_reqs, GFP_KERNEL);
1074         blkbk->pending_grant_handles = kmalloc(sizeof(blkbk->pending_grant_handles[0]) *
1075                                         mmap_pages, GFP_KERNEL);
1076         blkbk->pending_pages         = kzalloc(sizeof(blkbk->pending_pages[0]) *
1077                                         mmap_pages, GFP_KERNEL);
1078
1079         if (!blkbk->pending_reqs || !blkbk->pending_grant_handles ||
1080             !blkbk->pending_pages) {
1081                 rc = -ENOMEM;
1082                 goto out_of_memory;
1083         }
1084
1085         for (i = 0; i < mmap_pages; i++) {
1086                 blkbk->pending_grant_handles[i] = BLKBACK_INVALID_HANDLE;
1087                 blkbk->pending_pages[i] = alloc_page(GFP_KERNEL);
1088                 if (blkbk->pending_pages[i] == NULL) {
1089                         rc = -ENOMEM;
1090                         goto out_of_memory;
1091                 }
1092         }
1093         rc = xen_blkif_interface_init();
1094         if (rc)
1095                 goto failed_init;
1096
1097         INIT_LIST_HEAD(&blkbk->pending_free);
1098         spin_lock_init(&blkbk->pending_free_lock);
1099         init_waitqueue_head(&blkbk->pending_free_wq);
1100
1101         for (i = 0; i < xen_blkif_reqs; i++)
1102                 list_add_tail(&blkbk->pending_reqs[i].free_list,
1103                               &blkbk->pending_free);
1104
1105         rc = xen_blkif_xenbus_init();
1106         if (rc)
1107                 goto failed_init;
1108
1109         return 0;
1110
1111  out_of_memory:
1112         pr_alert(DRV_PFX "%s: out of memory\n", __func__);
1113  failed_init:
1114         kfree(blkbk->pending_reqs);
1115         kfree(blkbk->pending_grant_handles);
1116         if (blkbk->pending_pages) {
1117                 for (i = 0; i < mmap_pages; i++) {
1118                         if (blkbk->pending_pages[i])
1119                                 __free_page(blkbk->pending_pages[i]);
1120                 }
1121                 kfree(blkbk->pending_pages);
1122         }
1123         kfree(blkbk);
1124         blkbk = NULL;
1125         return rc;
1126 }
1127
1128 module_init(xen_blkif_init);
1129
1130 MODULE_LICENSE("Dual BSD/GPL");
1131 MODULE_ALIAS("xen-backend:vbd");