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"); 1132