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
  43 #include <xen/events.h>
  44 #include <xen/page.h>
  45 #include <xen/xen.h>
  46 #include <asm/xen/hypervisor.h>
  47 #include <asm/xen/hypercall.h>
  48 #include "common.h"
  49
  50 /*
  51  * These are rather arbitrary. They are fairly large because adjacent requests
  52  * pulled from a communication ring are quite likely to end up being part of
  53  * the same scatter/gather request at the disc.
  54  *
  55  * ** TRY INCREASING 'xen_blkif_reqs' IF WRITE SPEEDS SEEM TOO LOW **
  56  *
  57  * This will increase the chances of being able to write whole tracks.
  58  * 64 should be enough to keep us competitive with Linux.
  59  */
  60 static int xen_blkif_reqs = 64;
  61 module_param_named(reqs, xen_blkif_reqs, int, 0);
  62 MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate");
  63
  64 /* Run-time switchable: /sys/module/blkback/parameters/ */
  65 static unsigned int log_stats;
  66 module_param(log_stats, int, 0644);
  67
  68 /*
  69  * Each outstanding request that we've passed to the lower device layers has a
  70  * 'pending_req' allocated to it. Each buffer_head that completes decrements
  71  * the pendcnt towards zero. When it hits zero, the specified domain has a
  72  * response queued for it, with the saved 'id' passed back.
  73  */
  74 struct pending_req {
  75         struct xen_blkif        *blkif;
  76         u64                     id;
  77         int                     nr_pages;
  78         atomic_t                pendcnt;
  79         unsigned short          operation;
  80         int                     status;
  81         struct list_head        free_list;
  82 };
  83
  84 #define BLKBACK_INVALID_HANDLE (~0)
  85
  86 struct xen_blkbk {
  87         struct pending_req      *pending_reqs;
  88         /* List of all 'pending_req' available */
  89         struct list_head        pending_free;
  90         /* And its spinlock. */
  91         spinlock_t              pending_free_lock;
  92         wait_queue_head_t       pending_free_wq;
  93         /* The list of all pages that are available. */
  94         struct page             **pending_pages;
  95         /* And the grant handles that are available. */
  96         grant_handle_t          *pending_grant_handles;
  97 };
  98
  99 static struct xen_blkbk *blkbk;
 100
 101 /*
 102  * Little helpful macro to figure out the index and virtual address of the
 103  * pending_pages[..]. For each 'pending_req' we have have up to
 104  * BLKIF_MAX_SEGMENTS_PER_REQUEST (11) pages. The seg would be from 0 through
 105  * 10 and would index in the pending_pages[..].
 106  */
 107 static inline int vaddr_pagenr(struct pending_req *req, int seg)
 108 {
 109         return (req - blkbk->pending_reqs) *
 110                 BLKIF_MAX_SEGMENTS_PER_REQUEST + seg;
 111 }
 112
 113 #define pending_page(req, seg) pending_pages[vaddr_pagenr(req, seg)]
 114
 115 static inline unsigned long vaddr(struct pending_req *req, int seg)
 116 {
 117         unsigned long pfn = page_to_pfn(blkbk->pending_page(req, seg));
 118         return (unsigned long)pfn_to_kaddr(pfn);
 119 }
 120
 121 #define pending_handle(_req, _seg) \
 122         (blkbk->pending_grant_handles[vaddr_pagenr(_req, _seg)])
 123
 124
 125 static int do_block_io_op(struct xen_blkif *blkif);
 126 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 127                                 struct blkif_request *req,
 128                                 struct pending_req *pending_req);
 129 static void make_response(struct xen_blkif *blkif, u64 id,
 130                           unsigned short op, int st);
 131
 132 /*
 133  * Retrieve from the 'pending_reqs' a free pending_req structure to be used.
 134  */
 135 static struct pending_req *alloc_req(void)
 136 {
 137         struct pending_req *req = NULL;
 138         unsigned long flags;
 139
 140         spin_lock_irqsave(&blkbk->pending_free_lock, flags);
 141         if (!list_empty(&blkbk->pending_free)) {
 142                 req = list_entry(blkbk->pending_free.next, struct pending_req,
 143                                  free_list);
 144                 list_del(&req->free_list);
 145         }
 146         spin_unlock_irqrestore(&blkbk->pending_free_lock, flags);
 147         return req;
 148 }
 149
 150 /*
 151  * Return the 'pending_req' structure back to the freepool. We also
 152  * wake up the thread if it was waiting for a free page.
 153  */
 154 static void free_req(struct pending_req *req)
 155 {
 156         unsigned long flags;
 157         int was_empty;
 158
 159         spin_lock_irqsave(&blkbk->pending_free_lock, flags);
 160         was_empty = list_empty(&blkbk->pending_free);
 161         list_add(&req->free_list, &blkbk->pending_free);
 162         spin_unlock_irqrestore(&blkbk->pending_free_lock, flags);
 163         if (was_empty)
 164                 wake_up(&blkbk->pending_free_wq);
 165 }
 166
 167 /*
 168  * Routines for managing virtual block devices (vbds).
 169  */
 170 static int xen_vbd_translate(struct phys_req *req, struct xen_blkif *blkif,
 171                              int operation)
 172 {
 173         struct xen_vbd *vbd = &blkif->vbd;
 174         int rc = -EACCES;
 175
 176         if ((operation != READ) && vbd->readonly)
 177                 goto out;
 178
 179         if (likely(req->nr_sects)) {
 180                 blkif_sector_t end = req->sector_number + req->nr_sects;
 181
 182                 if (unlikely(end < req->sector_number))
 183                         goto out;
 184                 if (unlikely(end > vbd_sz(vbd)))
 185                         goto out;
 186         }
 187
 188         req->dev  = vbd->pdevice;
 189         req->bdev = vbd->bdev;
 190         rc = 0;
 191
 192  out:
 193         return rc;
 194 }
 195
 196 static void xen_vbd_resize(struct xen_blkif *blkif)
 197 {
 198         struct xen_vbd *vbd = &blkif->vbd;
 199         struct xenbus_transaction xbt;
 200         int err;
 201         struct xenbus_device *dev = xen_blkbk_xenbus(blkif->be);
 202         unsigned long long new_size = vbd_sz(vbd);
 203
 204         pr_info(DRV_PFX "VBD Resize: Domid: %d, Device: (%d, %d)\n",
 205                 blkif->domid, MAJOR(vbd->pdevice), MINOR(vbd->pdevice));
 206         pr_info(DRV_PFX "VBD Resize: new size %llu\n", new_size);
 207         vbd->size = new_size;
 208 again:
 209         err = xenbus_transaction_start(&xbt);
 210         if (err) {
 211                 pr_warn(DRV_PFX "Error starting transaction");
 212                 return;
 213         }
 214         err = xenbus_printf(xbt, dev->nodename, "sectors", "%llu",
 215                             (unsigned long long)vbd_sz(vbd));
 216         if (err) {
 217                 pr_warn(DRV_PFX "Error writing new size");
 218                 goto abort;
 219         }
 220         /*
 221          * Write the current state; we will use this to synchronize
 222          * the front-end. If the current state is "connected" the
 223          * front-end will get the new size information online.
 224          */
 225         err = xenbus_printf(xbt, dev->nodename, "state", "%d", dev->state);
 226         if (err) {
 227                 pr_warn(DRV_PFX "Error writing the state");
 228                 goto abort;
 229         }
 230
 231         err = xenbus_transaction_end(xbt, 0);
 232         if (err == -EAGAIN)
 233                 goto again;
 234         if (err)
 235                 pr_warn(DRV_PFX "Error ending transaction");
 236         return;
 237 abort:
 238         xenbus_transaction_end(xbt, 1);
 239 }
 240
 241 /*
 242  * Notification from the guest OS.
 243  */
 244 static void blkif_notify_work(struct xen_blkif *blkif)
 245 {
 246         blkif->waiting_reqs = 1;
 247         wake_up(&blkif->wq);
 248 }
 249
 250 irqreturn_t xen_blkif_be_int(int irq, void *dev_id)
 251 {
 252         blkif_notify_work(dev_id);
 253         return IRQ_HANDLED;
 254 }
 255
 256 /*
 257  * SCHEDULER FUNCTIONS
 258  */
 259
 260 static void print_stats(struct xen_blkif *blkif)
 261 {
 262         pr_info("xen-blkback (%s): oo %3d  |  rd %4d  |  wr %4d  |  f %4d"
 263                  "  |  ds %4d\n",
 264                  current->comm, blkif->st_oo_req,
 265                  blkif->st_rd_req, blkif->st_wr_req,
 266                  blkif->st_f_req, blkif->st_ds_req);
 267         blkif->st_print = jiffies + msecs_to_jiffies(10 * 1000);
 268         blkif->st_rd_req = 0;
 269         blkif->st_wr_req = 0;
 270         blkif->st_oo_req = 0;
 271         blkif->st_ds_req = 0;
 272 }
 273
 274 int xen_blkif_schedule(void *arg)
 275 {
 276         struct xen_blkif *blkif = arg;
 277         struct xen_vbd *vbd = &blkif->vbd;
 278
 279         xen_blkif_get(blkif);
 280
 281         while (!kthread_should_stop()) {
 282                 if (try_to_freeze())
 283                         continue;
 284                 if (unlikely(vbd->size != vbd_sz(vbd)))
 285                         xen_vbd_resize(blkif);
 286
 287                 wait_event_interruptible(
 288                         blkif->wq,
 289                         blkif->waiting_reqs || kthread_should_stop());
 290                 wait_event_interruptible(
 291                         blkbk->pending_free_wq,
 292                         !list_empty(&blkbk->pending_free) ||
 293                         kthread_should_stop());
 294
 295                 blkif->waiting_reqs = 0;
 296                 smp_mb(); /* clear flag *before* checking for work */
 297
 298                 if (do_block_io_op(blkif))
 299                         blkif->waiting_reqs = 1;
 300
 301                 if (log_stats && time_after(jiffies, blkif->st_print))
 302                         print_stats(blkif);
 303         }
 304
 305         if (log_stats)
 306                 print_stats(blkif);
 307
 308         blkif->xenblkd = NULL;
 309         xen_blkif_put(blkif);
 310
 311         return 0;
 312 }
 313
 314 struct seg_buf {
 315         unsigned long buf;
 316         unsigned int nsec;
 317 };
 318 /*
 319  * Unmap the grant references, and also remove the M2P over-rides
 320  * used in the 'pending_req'.
 321  */
 322 static void xen_blkbk_unmap(struct pending_req *req)
 323 {
 324         struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 325         struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 326         unsigned int i, invcount = 0;
 327         grant_handle_t handle;
 328         int ret;
 329
 330         for (i = 0; i < req->nr_pages; i++) {
 331                 handle = pending_handle(req, i);
 332                 if (handle == BLKBACK_INVALID_HANDLE)
 333                         continue;
 334                 gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
 335                                     GNTMAP_host_map, handle);
 336                 pending_handle(req, i) = BLKBACK_INVALID_HANDLE;
 337                 pages[invcount] = virt_to_page(vaddr(req, i));
 338                 invcount++;
 339         }
 340
 341         ret = gnttab_unmap_refs(unmap, NULL, pages, invcount);
 342         BUG_ON(ret);
 343 }
 344
 345 static int xen_blkbk_map(struct blkif_request *req,
 346                          struct pending_req *pending_req,
 347                          struct seg_buf seg[])
 348 {
 349         struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 350         int i;
 351         int nseg = req->u.rw.nr_segments;
 352         int ret = 0;
 353
 354         /*
 355          * Fill out preq.nr_sects with proper amount of sectors, and setup
 356          * assign map[..] with the PFN of the page in our domain with the
 357          * corresponding grant reference for each page.
 358          */
 359         for (i = 0; i < nseg; i++) {
 360                 uint32_t flags;
 361
 362                 flags = GNTMAP_host_map;
 363                 if (pending_req->operation != BLKIF_OP_READ)
 364                         flags |= GNTMAP_readonly;
 365                 gnttab_set_map_op(&map[i], vaddr(pending_req, i), flags,
 366                                   req->u.rw.seg[i].gref,
 367                                   pending_req->blkif->domid);
 368         }
 369
 370         ret = gnttab_map_refs(map, NULL, &blkbk->pending_page(pending_req, 0), nseg);
 371         BUG_ON(ret);
 372
 373         /*
 374          * Now swizzle the MFN in our domain with the MFN from the other domain
 375          * so that when we access vaddr(pending_req,i) it has the contents of
 376          * the page from the other domain.
 377          */
 378         for (i = 0; i < nseg; i++) {
 379                 if (unlikely(map[i].status != 0)) {
 380                         pr_debug(DRV_PFX "invalid buffer -- could not remap it\n");
 381                         map[i].handle = BLKBACK_INVALID_HANDLE;
 382                         ret |= 1;
 383                 }
 384
 385                 pending_handle(pending_req, i) = map[i].handle;
 386
 387                 if (ret)
 388                         continue;
 389
 390                 seg[i].buf  = map[i].dev_bus_addr |
 391                         (req->u.rw.seg[i].first_sect << 9);
 392         }
 393         return ret;
 394 }
 395
 396 static int dispatch_discard_io(struct xen_blkif *blkif,
 397                                 struct blkif_request *req)
 398 {
 399         int err = 0;
 400         int status = BLKIF_RSP_OKAY;
 401         struct block_device *bdev = blkif->vbd.bdev;
 402         unsigned long secure;
 403
 404         blkif->st_ds_req++;
 405
 406         xen_blkif_get(blkif);
 407         secure = (blkif->vbd.discard_secure &&
 408                  (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
 409                  BLKDEV_DISCARD_SECURE : 0;
 410
 411         err = blkdev_issue_discard(bdev, req->u.discard.sector_number,
 412                                    req->u.discard.nr_sectors,
 413                                    GFP_KERNEL, secure);
 414
 415         if (err == -EOPNOTSUPP) {
 416                 pr_debug(DRV_PFX "discard op failed, not supported\n");
 417                 status = BLKIF_RSP_EOPNOTSUPP;
 418         } else if (err)
 419                 status = BLKIF_RSP_ERROR;
 420
 421         make_response(blkif, req->u.discard.id, req->operation, status);
 422         xen_blkif_put(blkif);
 423         return err;
 424 }
 425
 426 static void xen_blk_drain_io(struct xen_blkif *blkif)
 427 {
 428         atomic_set(&blkif->drain, 1);
 429         do {
 430                 /* The initial value is one, and one refcnt taken at the
 431                  * start of the xen_blkif_schedule thread. */
 432                 if (atomic_read(&blkif->refcnt) <= 2)
 433                         break;
 434                 wait_for_completion_interruptible_timeout(
 435                                 &blkif->drain_complete, HZ);
 436
 437                 if (!atomic_read(&blkif->drain))
 438                         break;
 439         } while (!kthread_should_stop());
 440         atomic_set(&blkif->drain, 0);
 441 }
 442
 443 /*
 444  * Completion callback on the bio's. Called as bh->b_end_io()
 445  */
 446
 447 static void __end_block_io_op(struct pending_req *pending_req, int error)
 448 {
 449         /* An error fails the entire request. */
 450         if ((pending_req->operation == BLKIF_OP_FLUSH_DISKCACHE) &&
 451             (error == -EOPNOTSUPP)) {
 452                 pr_debug(DRV_PFX "flush diskcache op failed, not supported\n");
 453                 xen_blkbk_flush_diskcache(XBT_NIL, pending_req->blkif->be, 0);
 454                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 455         } else if ((pending_req->operation == BLKIF_OP_WRITE_BARRIER) &&
 456                     (error == -EOPNOTSUPP)) {
 457                 pr_debug(DRV_PFX "write barrier op failed, not supported\n");
 458                 xen_blkbk_barrier(XBT_NIL, pending_req->blkif->be, 0);
 459                 pending_req->status = BLKIF_RSP_EOPNOTSUPP;
 460         } else if (error) {
 461                 pr_debug(DRV_PFX "Buffer not up-to-date at end of operation,"
 462                          " error=%d\n", error);
 463                 pending_req->status = BLKIF_RSP_ERROR;
 464         }
 465
 466         /*
 467          * If all of the bio's have completed it is time to unmap
 468          * the grant references associated with 'request' and provide
 469          * the proper response on the ring.
 470          */
 471         if (atomic_dec_and_test(&pending_req->pendcnt)) {
 472                 xen_blkbk_unmap(pending_req);
 473                 make_response(pending_req->blkif, pending_req->id,
 474                               pending_req->operation, pending_req->status);
 475                 xen_blkif_put(pending_req->blkif);
 476                 if (atomic_read(&pending_req->blkif->refcnt) <= 2) {
 477                         if (atomic_read(&pending_req->blkif->drain))
 478                                 complete(&pending_req->blkif->drain_complete);
 479                 }
 480                 free_req(pending_req);
 481         }
 482 }
 483
 484 /*
 485  * bio callback.
 486  */
 487 static void end_block_io_op(struct bio *bio, int error)
 488 {
 489         __end_block_io_op(bio->bi_private, error);
 490         bio_put(bio);
 491 }
 492
 493
 494
 495 /*
 496  * Function to copy the from the ring buffer the 'struct blkif_request'
 497  * (which has the sectors we want, number of them, grant references, etc),
 498  * and transmute  it to the block API to hand it over to the proper block disk.
 499  */
 500 static int
 501 __do_block_io_op(struct xen_blkif *blkif)
 502 {
 503         union blkif_back_rings *blk_rings = &blkif->blk_rings;
 504         struct blkif_request req;
 505         struct pending_req *pending_req;
 506         RING_IDX rc, rp;
 507         int more_to_do = 0;
 508
 509         rc = blk_rings->common.req_cons;
 510         rp = blk_rings->common.sring->req_prod;
 511         rmb(); /* Ensure we see queued requests up to 'rp'. */
 512
 513         while (rc != rp) {
 514
 515                 if (RING_REQUEST_CONS_OVERFLOW(&blk_rings->common, rc))
 516                         break;
 517
 518                 if (kthread_should_stop()) {
 519                         more_to_do = 1;
 520                         break;
 521                 }
 522
 523                 pending_req = alloc_req();
 524                 if (NULL == pending_req) {
 525                         blkif->st_oo_req++;
 526                         more_to_do = 1;
 527                         break;
 528                 }
 529
 530                 switch (blkif->blk_protocol) {
 531                 case BLKIF_PROTOCOL_NATIVE:
 532                         memcpy(&req, RING_GET_REQUEST(&blk_rings->native, rc), sizeof(req));
 533                         break;
 534                 case BLKIF_PROTOCOL_X86_32:
 535                         blkif_get_x86_32_req(&req, RING_GET_REQUEST(&blk_rings->x86_32, rc));
 536                         break;
 537                 case BLKIF_PROTOCOL_X86_64:
 538                         blkif_get_x86_64_req(&req, RING_GET_REQUEST(&blk_rings->x86_64, rc));
 539                         break;
 540                 default:
 541                         BUG();
 542                 }
 543                 blk_rings->common.req_cons = ++rc; /* before make_response() */
 544
 545                 /* Apply all sanity checks to /private copy/ of request. */
 546                 barrier();
 547                 if (unlikely(req.operation == BLKIF_OP_DISCARD)) {
 548                         free_req(pending_req);
 549                         if (dispatch_discard_io(blkif, &req))
 550                                 break;
 551                 } else if (dispatch_rw_block_io(blkif, &req, pending_req))
 552                         break;
 553
 554                 /* Yield point for this unbounded loop. */
 555                 cond_resched();
 556         }
 557
 558         return more_to_do;
 559 }
 560
 561 static int
 562 do_block_io_op(struct xen_blkif *blkif)
 563 {
 564         union blkif_back_rings *blk_rings = &blkif->blk_rings;
 565         int more_to_do;
 566
 567         do {
 568                 more_to_do = __do_block_io_op(blkif);
 569                 if (more_to_do)
 570                         break;
 571
 572                 RING_FINAL_CHECK_FOR_REQUESTS(&blk_rings->common, more_to_do);
 573         } while (more_to_do);
 574
 575         return more_to_do;
 576 }
 577 /*
 578  * Transmutation of the 'struct blkif_request' to a proper 'struct bio'
 579  * and call the 'submit_bio' to pass it to the underlying storage.
 580  */
 581 static int dispatch_rw_block_io(struct xen_blkif *blkif,
 582                                 struct blkif_request *req,
 583                                 struct pending_req *pending_req)
 584 {
 585         struct phys_req preq;
 586         struct seg_buf seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 587         unsigned int nseg;
 588         struct bio *bio = NULL;
 589         struct bio *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 590         int i, nbio = 0;
 591         int operation;
 592         struct blk_plug plug;
 593         bool drain = false;
 594
 595         switch (req->operation) {
 596         case BLKIF_OP_READ:
 597                 blkif->st_rd_req++;
 598                 operation = READ;
 599                 break;
 600         case BLKIF_OP_WRITE:
 601                 blkif->st_wr_req++;
 602                 operation = WRITE_ODIRECT;
 603                 break;
 604         case BLKIF_OP_WRITE_BARRIER:
 605                 drain = true;
 606         case BLKIF_OP_FLUSH_DISKCACHE:
 607                 blkif->st_f_req++;
 608                 operation = WRITE_FLUSH;
 609                 break;
 610         default:
 611                 operation = 0; /* make gcc happy */
 612                 goto fail_response;
 613                 break;
 614         }
 615
 616         /* Check that the number of segments is sane. */
 617         nseg = req->u.rw.nr_segments;
 618
 619         if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
 620             unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
 621                 pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
 622                          nseg);
 623                 /* Haven't submitted any bio's yet. */
 624                 goto fail_response;
 625         }
 626
 627         preq.dev           = req->u.rw.handle;
 628         preq.sector_number = req->u.rw.sector_number;
 629         preq.nr_sects      = 0;
 630
 631         pending_req->blkif     = blkif;
 632         pending_req->id        = req->u.rw.id;
 633         pending_req->operation = req->operation;
 634         pending_req->status    = BLKIF_RSP_OKAY;
 635         pending_req->nr_pages  = nseg;
 636
 637         for (i = 0; i < nseg; i++) {
 638                 seg[i].nsec = req->u.rw.seg[i].last_sect -
 639                         req->u.rw.seg[i].first_sect + 1;
 640                 if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
 641                     (req->u.rw.seg[i].last_sect < req->u.rw.seg[i].first_sect))
 642                         goto fail_response;
 643                 preq.nr_sects += seg[i].nsec;
 644
 645         }
 646
 647         if (xen_vbd_translate(&preq, blkif, operation) != 0) {
 648                 pr_debug(DRV_PFX "access denied: %s of [%llu,%llu] on dev=%04x\n",
 649                          operation == READ ? "read" : "write",
 650                          preq.sector_number,
 651                          preq.sector_number + preq.nr_sects, preq.dev);
 652                 goto fail_response;
 653         }
 654
 655         /*
 656          * This check _MUST_ be done after xen_vbd_translate as the preq.bdev
 657          * is set there.
 658          */
 659         for (i = 0; i < nseg; i++) {
 660                 if (((int)preq.sector_number|(int)seg[i].nsec) &
 661                     ((bdev_logical_block_size(preq.bdev) >> 9) - 1)) {
 662                         pr_debug(DRV_PFX "Misaligned I/O request from domain %d",
 663                                  blkif->domid);
 664                         goto fail_response;
 665                 }
 666         }
 667
 668         /* Wait on all outstanding I/O's and once that has been completed
 669          * issue the WRITE_FLUSH.
 670          */
 671         if (drain)
 672                 xen_blk_drain_io(pending_req->blkif);
 673
 674         /*
 675          * If we have failed at this point, we need to undo the M2P override,
 676          * set gnttab_set_unmap_op on all of the grant references and perform
 677          * the hypercall to unmap the grants - that is all done in
 678          * xen_blkbk_unmap.
 679          */
 680         if (xen_blkbk_map(req, pending_req, seg))
 681                 goto fail_flush;
 682
 683         /*
 684          * This corresponding xen_blkif_put is done in __end_block_io_op, or
 685          * below (in "!bio") if we are handling a BLKIF_OP_DISCARD.
 686          */
 687         xen_blkif_get(blkif);
 688
 689         for (i = 0; i < nseg; i++) {
 690                 while ((bio == NULL) ||
 691                        (bio_add_page(bio,
 692                                      blkbk->pending_page(pending_req, i),
 693                                      seg[i].nsec << 9,
 694                                      seg[i].buf & ~PAGE_MASK) == 0)) {
 695
 696                         bio = bio_alloc(GFP_KERNEL, nseg-i);
 697                         if (unlikely(bio == NULL))
 698                                 goto fail_put_bio;
 699
 700                         biolist[nbio++] = bio;
 701                         bio->bi_bdev    = preq.bdev;
 702                         bio->bi_private = pending_req;
 703                         bio->bi_end_io  = end_block_io_op;
 704                         bio->bi_sector  = preq.sector_number;
 705                 }
 706
 707                 preq.sector_number += seg[i].nsec;
 708         }
 709
 710         /* This will be hit if the operation was a flush or discard. */
 711         if (!bio) {
 712                 BUG_ON(operation != WRITE_FLUSH);
 713
 714                 bio = bio_alloc(GFP_KERNEL, 0);
 715                 if (unlikely(bio == NULL))
 716                         goto fail_put_bio;
 717
 718                 biolist[nbio++] = bio;
 719                 bio->bi_bdev    = preq.bdev;
 720                 bio->bi_private = pending_req;
 721                 bio->bi_end_io  = end_block_io_op;
 722         }
 723
 724         /*
 725          * We set it one so that the last submit_bio does not have to call
 726          * atomic_inc.
 727          */
 728         atomic_set(&pending_req->pendcnt, nbio);
 729
 730         /* Get a reference count for the disk queue and start sending I/O */
 731         blk_start_plug(&plug);
 732
 733         for (i = 0; i < nbio; i++)
 734                 submit_bio(operation, biolist[i]);
 735
 736         /* Let the I/Os go.. */
 737         blk_finish_plug(&plug);
 738
 739         if (operation == READ)
 740                 blkif->st_rd_sect += preq.nr_sects;
 741         else if (operation & WRITE)
 742                 blkif->st_wr_sect += preq.nr_sects;
 743
 744         return 0;
 745
 746  fail_flush:
 747         xen_blkbk_unmap(pending_req);
 748  fail_response:
 749         /* Haven't submitted any bio's yet. */
 750         make_response(blkif, req->u.rw.id, req->operation, BLKIF_RSP_ERROR);
 751         free_req(pending_req);
 752         msleep(1); /* back off a bit */
 753         return -EIO;
 754
 755  fail_put_bio:
 756         for (i = 0; i < nbio; i++)
 757                 bio_put(biolist[i]);
 758         __end_block_io_op(pending_req, -EINVAL);
 759         msleep(1); /* back off a bit */
 760         return -EIO;
 761 }
 762
 763
 764
 765 /*
 766  * Put a response on the ring on how the operation fared.
 767  */
 768 static void make_response(struct xen_blkif *blkif, u64 id,
 769                           unsigned short op, int st)
 770 {
 771         struct blkif_response  resp;
 772         unsigned long     flags;
 773         union blkif_back_rings *blk_rings = &blkif->blk_rings;
 774         int notify;
 775
 776         resp.id        = id;
 777         resp.operation = op;
 778         resp.status    = st;
 779
 780         spin_lock_irqsave(&blkif->blk_ring_lock, flags);
 781         /* Place on the response ring for the relevant domain. */
 782         switch (blkif->blk_protocol) {
 783         case BLKIF_PROTOCOL_NATIVE:
 784                 memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
 785                        &resp, sizeof(resp));
 786                 break;
 787         case BLKIF_PROTOCOL_X86_32:
 788                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
 789                        &resp, sizeof(resp));
 790                 break;
 791         case BLKIF_PROTOCOL_X86_64:
 792                 memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
 793                        &resp, sizeof(resp));
 794                 break;
 795         default:
 796                 BUG();
 797         }
 798         blk_rings->common.rsp_prod_pvt++;
 799         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
 800         spin_unlock_irqrestore(&blkif->blk_ring_lock, flags);
 801         if (notify)
 802                 notify_remote_via_irq(blkif->irq);
 803 }
 804
 805 static int __init xen_blkif_init(void)
 806 {
 807         int i, mmap_pages;
 808         int rc = 0;
 809
 810         if (!xen_domain())
 811                 return -ENODEV;
 812
 813         blkbk = kzalloc(sizeof(struct xen_blkbk), GFP_KERNEL);
 814         if (!blkbk) {
 815                 pr_alert(DRV_PFX "%s: out of memory!\n", __func__);
 816                 return -ENOMEM;
 817         }
 818
 819         mmap_pages = xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST;
 820
 821         blkbk->pending_reqs          = kzalloc(sizeof(blkbk->pending_reqs[0]) *
 822                                         xen_blkif_reqs, GFP_KERNEL);
 823         blkbk->pending_grant_handles = kmalloc(sizeof(blkbk->pending_grant_handles[0]) *
 824                                         mmap_pages, GFP_KERNEL);
 825         blkbk->pending_pages         = kzalloc(sizeof(blkbk->pending_pages[0]) *
 826                                         mmap_pages, GFP_KERNEL);
 827
 828         if (!blkbk->pending_reqs || !blkbk->pending_grant_handles ||
 829             !blkbk->pending_pages) {
 830                 rc = -ENOMEM;
 831                 goto out_of_memory;
 832         }
 833
 834         for (i = 0; i < mmap_pages; i++) {
 835                 blkbk->pending_grant_handles[i] = BLKBACK_INVALID_HANDLE;
 836                 blkbk->pending_pages[i] = alloc_page(GFP_KERNEL);
 837                 if (blkbk->pending_pages[i] == NULL) {
 838                         rc = -ENOMEM;
 839                         goto out_of_memory;
 840                 }
 841         }
 842         rc = xen_blkif_interface_init();
 843         if (rc)
 844                 goto failed_init;
 845
 846         INIT_LIST_HEAD(&blkbk->pending_free);
 847         spin_lock_init(&blkbk->pending_free_lock);
 848         init_waitqueue_head(&blkbk->pending_free_wq);
 849
 850         for (i = 0; i < xen_blkif_reqs; i++)
 851                 list_add_tail(&blkbk->pending_reqs[i].free_list,
 852                               &blkbk->pending_free);
 853
 854         rc = xen_blkif_xenbus_init();
 855         if (rc)
 856                 goto failed_init;
 857
 858         return 0;
 859
 860  out_of_memory:
 861         pr_alert(DRV_PFX "%s: out of memory\n", __func__);
 862  failed_init:
 863         kfree(blkbk->pending_reqs);
 864         kfree(blkbk->pending_grant_handles);
 865         if (blkbk->pending_pages) {
 866                 for (i = 0; i < mmap_pages; i++) {
 867                         if (blkbk->pending_pages[i])
 868                                 __free_page(blkbk->pending_pages[i]);
 869                 }
 870                 kfree(blkbk->pending_pages);
 871         }
 872         kfree(blkbk);
 873         blkbk = NULL;
 874         return rc;
 875 }
 876
 877 module_init(xen_blkif_init);
 878
 879 MODULE_LICENSE("Dual BSD/GPL");
 880 MODULE_ALIAS("xen-backend:vbd");