drivers/block/xen-blkfront.c

   1 /*
   2  * blkfront.c
   3  *
   4  * XenLinux virtual block device driver.
   5  *
   6  * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
   7  * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
   8  * Copyright (c) 2004, Christian Limpach
   9  * Copyright (c) 2004, Andrew Warfield
  10  * Copyright (c) 2005, Christopher Clark
  11  * Copyright (c) 2005, XenSource Ltd
  12  *
  13  * This program is free software; you can redistribute it and/or
  14  * modify it under the terms of the GNU General Public License version 2
  15  * as published by the Free Software Foundation; or, when distributed
  16  * separately from the Linux kernel or incorporated into other
  17  * software packages, subject to the following license:
  18  *
  19  * Permission is hereby granted, free of charge, to any person obtaining a copy
  20  * of this source file (the "Software"), to deal in the Software without
  21  * restriction, including without limitation the rights to use, copy, modify,
  22  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  23  * and to permit persons to whom the Software is furnished to do so, subject to
  24  * the following conditions:
  25  *
  26  * The above copyright notice and this permission notice shall be included in
  27  * all copies or substantial portions of the Software.
  28  *
  29  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  30  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  31  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  32  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  33  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  34  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  35  * IN THE SOFTWARE.
  36  */
  37
  38 #include <linux/interrupt.h>
  39 #include <linux/blkdev.h>
  40 #include <linux/hdreg.h>
  41 #include <linux/cdrom.h>
  42 #include <linux/module.h>
  43 #include <linux/slab.h>
  44 #include <linux/mutex.h>
  45 #include <linux/scatterlist.h>
  46 #include <linux/bitmap.h>
  47
  48 #include <xen/xen.h>
  49 #include <xen/xenbus.h>
  50 #include <xen/grant_table.h>
  51 #include <xen/events.h>
  52 #include <xen/page.h>
  53 #include <xen/platform_pci.h>
  54
  55 #include <xen/interface/grant_table.h>
  56 #include <xen/interface/io/blkif.h>
  57 #include <xen/interface/io/protocols.h>
  58
  59 #include <asm/xen/hypervisor.h>
  60
  61 enum blkif_state {
  62         BLKIF_STATE_DISCONNECTED,
  63         BLKIF_STATE_CONNECTED,
  64         BLKIF_STATE_SUSPENDED,
  65 };
  66
  67 struct blk_shadow {
  68         struct blkif_request req;
  69         struct request *request;
  70         unsigned long frame[BLKIF_MAX_SEGMENTS_PER_REQUEST];
  71 };
  72
  73 static DEFINE_MUTEX(blkfront_mutex);
  74 static const struct block_device_operations xlvbd_block_fops;
  75
  76 #define BLK_RING_SIZE __CONST_RING_SIZE(blkif, PAGE_SIZE)
  77
  78 /*
  79  * We have one of these per vbd, whether ide, scsi or 'other'.  They
  80  * hang in private_data off the gendisk structure. We may end up
  81  * putting all kinds of interesting stuff here :-)
  82  */
  83 struct blkfront_info
  84 {
  85         spinlock_t io_lock;
  86         struct mutex mutex;
  87         struct xenbus_device *xbdev;
  88         struct gendisk *gd;
  89         int vdevice;
  90         blkif_vdev_t handle;
  91         enum blkif_state connected;
  92         int ring_ref;
  93         struct blkif_front_ring ring;
  94         struct scatterlist sg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
  95         unsigned int evtchn, irq;
  96         struct request_queue *rq;
  97         struct work_struct work;
  98         struct gnttab_free_callback callback;
  99         struct blk_shadow shadow[BLK_RING_SIZE];
 100         unsigned long shadow_free;
 101         unsigned int feature_flush;
 102         unsigned int flush_op;
 103         unsigned int feature_discard:1;
 104         unsigned int feature_secdiscard:1;
 105         unsigned int discard_granularity;
 106         unsigned int discard_alignment;
 107         int is_ready;
 108 };
 109
 110 static unsigned int nr_minors;
 111 static unsigned long *minors;
 112 static DEFINE_SPINLOCK(minor_lock);
 113
 114 #define MAXIMUM_OUTSTANDING_BLOCK_REQS \
 115         (BLKIF_MAX_SEGMENTS_PER_REQUEST * BLK_RING_SIZE)
 116 #define GRANT_INVALID_REF       0
 117
 118 #define PARTS_PER_DISK          16
 119 #define PARTS_PER_EXT_DISK      256
 120
 121 #define BLKIF_MAJOR(dev) ((dev)>>8)
 122 #define BLKIF_MINOR(dev) ((dev) & 0xff)
 123
 124 #define EXT_SHIFT 28
 125 #define EXTENDED (1<<EXT_SHIFT)
 126 #define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
 127 #define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
 128 #define EMULATED_HD_DISK_MINOR_OFFSET (0)
 129 #define EMULATED_HD_DISK_NAME_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET / 256)
 130 #define EMULATED_SD_DISK_MINOR_OFFSET (0)
 131 #define EMULATED_SD_DISK_NAME_OFFSET (EMULATED_SD_DISK_MINOR_OFFSET / 256)
 132
 133 #define DEV_NAME        "xvd"   /* name in /dev */
 134
 135 static int get_id_from_freelist(struct blkfront_info *info)
 136 {
 137         unsigned long free = info->shadow_free;
 138         BUG_ON(free >= BLK_RING_SIZE);
 139         info->shadow_free = info->shadow[free].req.u.rw.id;
 140         info->shadow[free].req.u.rw.id = 0x0fffffee; /* debug */
 141         return free;
 142 }
 143
 144 static void add_id_to_freelist(struct blkfront_info *info,
 145                                unsigned long id)
 146 {
 147         info->shadow[id].req.u.rw.id  = info->shadow_free;
 148         info->shadow[id].request = NULL;
 149         info->shadow_free = id;
 150 }
 151
 152 static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
 153 {
 154         unsigned int end = minor + nr;
 155         int rc;
 156
 157         if (end > nr_minors) {
 158                 unsigned long *bitmap, *old;
 159
 160                 bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap),
 161                                  GFP_KERNEL);
 162                 if (bitmap == NULL)
 163                         return -ENOMEM;
 164
 165                 spin_lock(&minor_lock);
 166                 if (end > nr_minors) {
 167                         old = minors;
 168                         memcpy(bitmap, minors,
 169                                BITS_TO_LONGS(nr_minors) * sizeof(*bitmap));
 170                         minors = bitmap;
 171                         nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;
 172                 } else
 173                         old = bitmap;
 174                 spin_unlock(&minor_lock);
 175                 kfree(old);
 176         }
 177
 178         spin_lock(&minor_lock);
 179         if (find_next_bit(minors, end, minor) >= end) {
 180                 bitmap_set(minors, minor, nr);
 181                 rc = 0;
 182         } else
 183                 rc = -EBUSY;
 184         spin_unlock(&minor_lock);
 185
 186         return rc;
 187 }
 188
 189 static void xlbd_release_minors(unsigned int minor, unsigned int nr)
 190 {
 191         unsigned int end = minor + nr;
 192
 193         BUG_ON(end > nr_minors);
 194         spin_lock(&minor_lock);
 195         bitmap_clear(minors,  minor, nr);
 196         spin_unlock(&minor_lock);
 197 }
 198
 199 static void blkif_restart_queue_callback(void *arg)
 200 {
 201         struct blkfront_info *info = (struct blkfront_info *)arg;
 202         schedule_work(&info->work);
 203 }
 204
 205 static int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
 206 {
 207         /* We don't have real geometry info, but let's at least return
 208            values consistent with the size of the device */
 209         sector_t nsect = get_capacity(bd->bd_disk);
 210         sector_t cylinders = nsect;
 211
 212         hg->heads = 0xff;
 213         hg->sectors = 0x3f;
 214         sector_div(cylinders, hg->heads * hg->sectors);
 215         hg->cylinders = cylinders;
 216         if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
 217                 hg->cylinders = 0xffff;
 218         return 0;
 219 }
 220
 221 static int blkif_ioctl(struct block_device *bdev, fmode_t mode,
 222                        unsigned command, unsigned long argument)
 223 {
 224         struct blkfront_info *info = bdev->bd_disk->private_data;
 225         int i;
 226
 227         dev_dbg(&info->xbdev->dev, "command: 0x%x, argument: 0x%lx\n",
 228                 command, (long)argument);
 229
 230         switch (command) {
 231         case CDROMMULTISESSION:
 232                 dev_dbg(&info->xbdev->dev, "FIXME: support multisession CDs later\n");
 233                 for (i = 0; i < sizeof(struct cdrom_multisession); i++)
 234                         if (put_user(0, (char __user *)(argument + i)))
 235                                 return -EFAULT;
 236                 return 0;
 237
 238         case CDROM_GET_CAPABILITY: {
 239                 struct gendisk *gd = info->gd;
 240                 if (gd->flags & GENHD_FL_CD)
 241                         return 0;
 242                 return -EINVAL;
 243         }
 244
 245         default:
 246                 /*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
 247                   command);*/
 248                 return -EINVAL; /* same return as native Linux */
 249         }
 250
 251         return 0;
 252 }
 253
 254 /*
 255  * Generate a Xen blkfront IO request from a blk layer request.  Reads
 256  * and writes are handled as expected.
 257  *
 258  * @req: a request struct
 259  */
 260 static int blkif_queue_request(struct request *req)
 261 {
 262         struct blkfront_info *info = req->rq_disk->private_data;
 263         unsigned long buffer_mfn;
 264         struct blkif_request *ring_req;
 265         unsigned long id;
 266         unsigned int fsect, lsect;
 267         int i, ref;
 268         grant_ref_t gref_head;
 269         struct scatterlist *sg;
 270
 271         if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
 272                 return 1;
 273
 274         if (gnttab_alloc_grant_references(
 275                 BLKIF_MAX_SEGMENTS_PER_REQUEST, &gref_head) < 0) {
 276                 gnttab_request_free_callback(
 277                         &info->callback,
 278                         blkif_restart_queue_callback,
 279                         info,
 280                         BLKIF_MAX_SEGMENTS_PER_REQUEST);
 281                 return 1;
 282         }
 283
 284         /* Fill out a communications ring structure. */
 285         ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
 286         id = get_id_from_freelist(info);
 287         info->shadow[id].request = req;
 288
 289         ring_req->u.rw.id = id;
 290         ring_req->u.rw.sector_number = (blkif_sector_t)blk_rq_pos(req);
 291         ring_req->u.rw.handle = info->handle;
 292
 293         ring_req->operation = rq_data_dir(req) ?
 294                 BLKIF_OP_WRITE : BLKIF_OP_READ;
 295
 296         if (req->cmd_flags & (REQ_FLUSH | REQ_FUA)) {
 297                 /*
 298                  * Ideally we can do an unordered flush-to-disk. In case the
 299                  * backend onlysupports barriers, use that. A barrier request
 300                  * a superset of FUA, so we can implement it the same
 301                  * way.  (It's also a FLUSH+FUA, since it is
 302                  * guaranteed ordered WRT previous writes.)
 303                  */
 304                 ring_req->operation = info->flush_op;
 305         }
 306
 307         if (unlikely(req->cmd_flags & (REQ_DISCARD | REQ_SECURE))) {
 308                 /* id, sector_number and handle are set above. */
 309                 ring_req->operation = BLKIF_OP_DISCARD;
 310                 ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
 311                 if ((req->cmd_flags & REQ_SECURE) && info->feature_secdiscard)
 312                         ring_req->u.discard.flag = BLKIF_DISCARD_SECURE;
 313                 else
 314                         ring_req->u.discard.flag = 0;
 315         } else {
 316                 ring_req->u.rw.nr_segments = blk_rq_map_sg(req->q, req,
 317                                                            info->sg);
 318                 BUG_ON(ring_req->u.rw.nr_segments >
 319                        BLKIF_MAX_SEGMENTS_PER_REQUEST);
 320
 321                 for_each_sg(info->sg, sg, ring_req->u.rw.nr_segments, i) {
 322                         buffer_mfn = pfn_to_mfn(page_to_pfn(sg_page(sg)));
 323                         fsect = sg->offset >> 9;
 324                         lsect = fsect + (sg->length >> 9) - 1;
 325                         /* install a grant reference. */
 326                         ref = gnttab_claim_grant_reference(&gref_head);
 327                         BUG_ON(ref == -ENOSPC);
 328
 329                         gnttab_grant_foreign_access_ref(
 330                                         ref,
 331                                         info->xbdev->otherend_id,
 332                                         buffer_mfn,
 333                                         rq_data_dir(req));
 334
 335                         info->shadow[id].frame[i] = mfn_to_pfn(buffer_mfn);
 336                         ring_req->u.rw.seg[i] =
 337                                         (struct blkif_request_segment) {
 338                                                 .gref       = ref,
 339                                                 .first_sect = fsect,
 340                                                 .last_sect  = lsect };
 341                 }
 342         }
 343
 344         info->ring.req_prod_pvt++;
 345
 346         /* Keep a private copy so we can reissue requests when recovering. */
 347         info->shadow[id].req = *ring_req;
 348
 349         gnttab_free_grant_references(gref_head);
 350
 351         return 0;
 352 }
 353
 354
 355 static inline void flush_requests(struct blkfront_info *info)
 356 {
 357         int notify;
 358
 359         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&info->ring, notify);
 360
 361         if (notify)
 362                 notify_remote_via_irq(info->irq);
 363 }
 364
 365 /*
 366  * do_blkif_request
 367  *  read a block; request is in a request queue
 368  */
 369 static void do_blkif_request(struct request_queue *rq)
 370 {
 371         struct blkfront_info *info = NULL;
 372         struct request *req;
 373         int queued;
 374
 375         pr_debug("Entered do_blkif_request\n");
 376
 377         queued = 0;
 378
 379         while ((req = blk_peek_request(rq)) != NULL) {
 380                 info = req->rq_disk->private_data;
 381
 382                 if (RING_FULL(&info->ring))
 383                         goto wait;
 384
 385                 blk_start_request(req);
 386
 387                 if ((req->cmd_type != REQ_TYPE_FS) ||
 388                     ((req->cmd_flags & (REQ_FLUSH | REQ_FUA)) &&
 389                     !info->flush_op)) {
 390                         __blk_end_request_all(req, -EIO);
 391                         continue;
 392                 }
 393
 394                 pr_debug("do_blk_req %p: cmd %p, sec %lx, "
 395                          "(%u/%u) buffer:%p [%s]\n",
 396                          req, req->cmd, (unsigned long)blk_rq_pos(req),
 397                          blk_rq_cur_sectors(req), blk_rq_sectors(req),
 398                          req->buffer, rq_data_dir(req) ? "write" : "read");
 399
 400                 if (blkif_queue_request(req)) {
 401                         blk_requeue_request(rq, req);
 402 wait:
 403                         /* Avoid pointless unplugs. */
 404                         blk_stop_queue(rq);
 405                         break;
 406                 }
 407
 408                 queued++;
 409         }
 410
 411         if (queued != 0)
 412                 flush_requests(info);
 413 }
 414
 415 static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
 416 {
 417         struct request_queue *rq;
 418         struct blkfront_info *info = gd->private_data;
 419
 420         rq = blk_init_queue(do_blkif_request, &info->io_lock);
 421         if (rq == NULL)
 422                 return -1;
 423
 424         queue_flag_set_unlocked(QUEUE_FLAG_VIRT, rq);
 425
 426         if (info->feature_discard) {
 427                 queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, rq);
 428                 blk_queue_max_discard_sectors(rq, get_capacity(gd));
 429                 rq->limits.discard_granularity = info->discard_granularity;
 430                 rq->limits.discard_alignment = info->discard_alignment;
 431                 if (info->feature_secdiscard)
 432                         queue_flag_set_unlocked(QUEUE_FLAG_SECDISCARD, rq);
 433         }
 434
 435         /* Hard sector size and max sectors impersonate the equiv. hardware. */
 436         blk_queue_logical_block_size(rq, sector_size);
 437         blk_queue_max_hw_sectors(rq, 512);
 438
 439         /* Each segment in a request is up to an aligned page in size. */
 440         blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
 441         blk_queue_max_segment_size(rq, PAGE_SIZE);
 442
 443         /* Ensure a merged request will fit in a single I/O ring slot. */
 444         blk_queue_max_segments(rq, BLKIF_MAX_SEGMENTS_PER_REQUEST);
 445
 446         /* Make sure buffer addresses are sector-aligned. */
 447         blk_queue_dma_alignment(rq, 511);
 448
 449         /* Make sure we don't use bounce buffers. */
 450         blk_queue_bounce_limit(rq, BLK_BOUNCE_ANY);
 451
 452         gd->queue = rq;
 453
 454         return 0;
 455 }
 456
 457
 458 static void xlvbd_flush(struct blkfront_info *info)
 459 {
 460         blk_queue_flush(info->rq, info->feature_flush);
 461         printk(KERN_INFO "blkfront: %s: %s: %s\n",
 462                info->gd->disk_name,
 463                info->flush_op == BLKIF_OP_WRITE_BARRIER ?
 464                 "barrier" : (info->flush_op == BLKIF_OP_FLUSH_DISKCACHE ?
 465                 "flush diskcache" : "barrier or flush"),
 466                info->feature_flush ? "enabled" : "disabled");
 467 }
 468
 469 static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
 470 {
 471         int major;
 472         major = BLKIF_MAJOR(vdevice);
 473         *minor = BLKIF_MINOR(vdevice);
 474         switch (major) {
 475                 case XEN_IDE0_MAJOR:
 476                         *offset = (*minor / 64) + EMULATED_HD_DISK_NAME_OFFSET;
 477                         *minor = ((*minor / 64) * PARTS_PER_DISK) +
 478                                 EMULATED_HD_DISK_MINOR_OFFSET;
 479                         break;
 480                 case XEN_IDE1_MAJOR:
 481                         *offset = (*minor / 64) + 2 + EMULATED_HD_DISK_NAME_OFFSET;
 482                         *minor = (((*minor / 64) + 2) * PARTS_PER_DISK) +
 483                                 EMULATED_HD_DISK_MINOR_OFFSET;
 484                         break;
 485                 case XEN_SCSI_DISK0_MAJOR:
 486                         *offset = (*minor / PARTS_PER_DISK) + EMULATED_SD_DISK_NAME_OFFSET;
 487                         *minor = *minor + EMULATED_SD_DISK_MINOR_OFFSET;
 488                         break;
 489                 case XEN_SCSI_DISK1_MAJOR:
 490                 case XEN_SCSI_DISK2_MAJOR:
 491                 case XEN_SCSI_DISK3_MAJOR:
 492                 case XEN_SCSI_DISK4_MAJOR:
 493                 case XEN_SCSI_DISK5_MAJOR:
 494                 case XEN_SCSI_DISK6_MAJOR:
 495                 case XEN_SCSI_DISK7_MAJOR:
 496                         *offset = (*minor / PARTS_PER_DISK) +
 497                                 ((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
 498                                 EMULATED_SD_DISK_NAME_OFFSET;
 499                         *minor = *minor +
 500                                 ((major - XEN_SCSI_DISK1_MAJOR + 1) * 16 * PARTS_PER_DISK) +
 501                                 EMULATED_SD_DISK_MINOR_OFFSET;
 502                         break;
 503                 case XEN_SCSI_DISK8_MAJOR:
 504                 case XEN_SCSI_DISK9_MAJOR:
 505                 case XEN_SCSI_DISK10_MAJOR:
 506                 case XEN_SCSI_DISK11_MAJOR:
 507                 case XEN_SCSI_DISK12_MAJOR:
 508                 case XEN_SCSI_DISK13_MAJOR:
 509                 case XEN_SCSI_DISK14_MAJOR:
 510                 case XEN_SCSI_DISK15_MAJOR:
 511                         *offset = (*minor / PARTS_PER_DISK) +
 512                                 ((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
 513                                 EMULATED_SD_DISK_NAME_OFFSET;
 514                         *minor = *minor +
 515                                 ((major - XEN_SCSI_DISK8_MAJOR + 8) * 16 * PARTS_PER_DISK) +
 516                                 EMULATED_SD_DISK_MINOR_OFFSET;
 517                         break;
 518                 case XENVBD_MAJOR:
 519                         *offset = *minor / PARTS_PER_DISK;
 520                         break;
 521                 default:
 522                         printk(KERN_WARNING "blkfront: your disk configuration is "
 523                                         "incorrect, please use an xvd device instead\n");
 524                         return -ENODEV;
 525         }
 526         return 0;
 527 }
 528
 529 static char *encode_disk_name(char *ptr, unsigned int n)
 530 {
 531         if (n >= 26)
 532                 ptr = encode_disk_name(ptr, n / 26 - 1);
 533         *ptr = 'a' + n % 26;
 534         return ptr + 1;
 535 }
 536
 537 static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
 538                                struct blkfront_info *info,
 539                                u16 vdisk_info, u16 sector_size)
 540 {
 541         struct gendisk *gd;
 542         int nr_minors = 1;
 543         int err;
 544         unsigned int offset;
 545         int minor;
 546         int nr_parts;
 547         char *ptr;
 548
 549         BUG_ON(info->gd != NULL);
 550         BUG_ON(info->rq != NULL);
 551
 552         if ((info->vdevice>>EXT_SHIFT) > 1) {
 553                 /* this is above the extended range; something is wrong */
 554                 printk(KERN_WARNING "blkfront: vdevice 0x%x is above the extended range; ignoring\n", info->vdevice);
 555                 return -ENODEV;
 556         }
 557
 558         if (!VDEV_IS_EXTENDED(info->vdevice)) {
 559                 err = xen_translate_vdev(info->vdevice, &minor, &offset);
 560                 if (err)
 561                         return err;
 562                 nr_parts = PARTS_PER_DISK;
 563         } else {
 564                 minor = BLKIF_MINOR_EXT(info->vdevice);
 565                 nr_parts = PARTS_PER_EXT_DISK;
 566                 offset = minor / nr_parts;
 567                 if (xen_hvm_domain() && offset < EMULATED_HD_DISK_NAME_OFFSET + 4)
 568                         printk(KERN_WARNING "blkfront: vdevice 0x%x might conflict with "
 569                                         "emulated IDE disks,\n\t choose an xvd device name"
 570                                         "from xvde on\n", info->vdevice);
 571         }
 572         if (minor >> MINORBITS) {
 573                 pr_warn("blkfront: %#x's minor (%#x) out of range; ignoring\n",
 574                         info->vdevice, minor);
 575                 return -ENODEV;
 576         }
 577
 578         if ((minor % nr_parts) == 0)
 579                 nr_minors = nr_parts;
 580
 581         err = xlbd_reserve_minors(minor, nr_minors);
 582         if (err)
 583                 goto out;
 584         err = -ENODEV;
 585
 586         gd = alloc_disk(nr_minors);
 587         if (gd == NULL)
 588                 goto release;
 589
 590         strcpy(gd->disk_name, DEV_NAME);
 591         ptr = encode_disk_name(gd->disk_name + sizeof(DEV_NAME) - 1, offset);
 592         BUG_ON(ptr >= gd->disk_name + DISK_NAME_LEN);
 593         if (nr_minors > 1)
 594                 *ptr = 0;
 595         else
 596                 snprintf(ptr, gd->disk_name + DISK_NAME_LEN - ptr,
 597                          "%d", minor & (nr_parts - 1));
 598
 599         gd->major = XENVBD_MAJOR;
 600         gd->first_minor = minor;
 601         gd->fops = &xlvbd_block_fops;
 602         gd->private_data = info;
 603         gd->driverfs_dev = &(info->xbdev->dev);
 604         set_capacity(gd, capacity);
 605
 606         if (xlvbd_init_blk_queue(gd, sector_size)) {
 607                 del_gendisk(gd);
 608                 goto release;
 609         }
 610
 611         info->rq = gd->queue;
 612         info->gd = gd;
 613
 614         xlvbd_flush(info);
 615
 616         if (vdisk_info & VDISK_READONLY)
 617                 set_disk_ro(gd, 1);
 618
 619         if (vdisk_info & VDISK_REMOVABLE)
 620                 gd->flags |= GENHD_FL_REMOVABLE;
 621
 622         if (vdisk_info & VDISK_CDROM)
 623                 gd->flags |= GENHD_FL_CD;
 624
 625         return 0;
 626
 627  release:
 628         xlbd_release_minors(minor, nr_minors);
 629  out:
 630         return err;
 631 }
 632
 633 static void xlvbd_release_gendisk(struct blkfront_info *info)
 634 {
 635         unsigned int minor, nr_minors;
 636         unsigned long flags;
 637
 638         if (info->rq == NULL)
 639                 return;
 640
 641         spin_lock_irqsave(&info->io_lock, flags);
 642
 643         /* No more blkif_request(). */
 644         blk_stop_queue(info->rq);
 645
 646         /* No more gnttab callback work. */
 647         gnttab_cancel_free_callback(&info->callback);
 648         spin_unlock_irqrestore(&info->io_lock, flags);
 649
 650         /* Flush gnttab callback work. Must be done with no locks held. */
 651         flush_work_sync(&info->work);
 652
 653         del_gendisk(info->gd);
 654
 655         minor = info->gd->first_minor;
 656         nr_minors = info->gd->minors;
 657         xlbd_release_minors(minor, nr_minors);
 658
 659         blk_cleanup_queue(info->rq);
 660         info->rq = NULL;
 661
 662         put_disk(info->gd);
 663         info->gd = NULL;
 664 }
 665
 666 static void kick_pending_request_queues(struct blkfront_info *info)
 667 {
 668         if (!RING_FULL(&info->ring)) {
 669                 /* Re-enable calldowns. */
 670                 blk_start_queue(info->rq);
 671                 /* Kick things off immediately. */
 672                 do_blkif_request(info->rq);
 673         }
 674 }
 675
 676 static void blkif_restart_queue(struct work_struct *work)
 677 {
 678         struct blkfront_info *info = container_of(work, struct blkfront_info, work);
 679
 680         spin_lock_irq(&info->io_lock);
 681         if (info->connected == BLKIF_STATE_CONNECTED)
 682                 kick_pending_request_queues(info);
 683         spin_unlock_irq(&info->io_lock);
 684 }
 685
 686 static void blkif_free(struct blkfront_info *info, int suspend)
 687 {
 688         /* Prevent new requests being issued until we fix things up. */
 689         spin_lock_irq(&info->io_lock);
 690         info->connected = suspend ?
 691                 BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
 692         /* No more blkif_request(). */
 693         if (info->rq)
 694                 blk_stop_queue(info->rq);
 695         /* No more gnttab callback work. */
 696         gnttab_cancel_free_callback(&info->callback);
 697         spin_unlock_irq(&info->io_lock);
 698
 699         /* Flush gnttab callback work. Must be done with no locks held. */
 700         flush_work_sync(&info->work);
 701
 702         /* Free resources associated with old device channel. */
 703         if (info->ring_ref != GRANT_INVALID_REF) {
 704                 gnttab_end_foreign_access(info->ring_ref, 0,
 705                                           (unsigned long)info->ring.sring);
 706                 info->ring_ref = GRANT_INVALID_REF;
 707                 info->ring.sring = NULL;
 708         }
 709         if (info->irq)
 710                 unbind_from_irqhandler(info->irq, info);
 711         info->evtchn = info->irq = 0;
 712
 713 }
 714
 715 static void blkif_completion(struct blk_shadow *s)
 716 {
 717         int i;
 718         /* Do not let BLKIF_OP_DISCARD as nr_segment is in the same place
 719          * flag. */
 720         for (i = 0; i < s->req.u.rw.nr_segments; i++)
 721                 gnttab_end_foreign_access(s->req.u.rw.seg[i].gref, 0, 0UL);
 722 }
 723
 724 static irqreturn_t blkif_interrupt(int irq, void *dev_id)
 725 {
 726         struct request *req;
 727         struct blkif_response *bret;
 728         RING_IDX i, rp;
 729         unsigned long flags;
 730         struct blkfront_info *info = (struct blkfront_info *)dev_id;
 731         int error;
 732
 733         spin_lock_irqsave(&info->io_lock, flags);
 734
 735         if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) {
 736                 spin_unlock_irqrestore(&info->io_lock, flags);
 737                 return IRQ_HANDLED;
 738         }
 739
 740  again:
 741         rp = info->ring.sring->rsp_prod;
 742         rmb(); /* Ensure we see queued responses up to 'rp'. */
 743
 744         for (i = info->ring.rsp_cons; i != rp; i++) {
 745                 unsigned long id;
 746
 747                 bret = RING_GET_RESPONSE(&info->ring, i);
 748                 id   = bret->id;
 749                 req  = info->shadow[id].request;
 750
 751                 if (bret->operation != BLKIF_OP_DISCARD)
 752                         blkif_completion(&info->shadow[id]);
 753
 754                 add_id_to_freelist(info, id);
 755
 756                 error = (bret->status == BLKIF_RSP_OKAY) ? 0 : -EIO;
 757                 switch (bret->operation) {
 758                 case BLKIF_OP_DISCARD:
 759                         if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
 760                                 struct request_queue *rq = info->rq;
 761                                 printk(KERN_WARNING "blkfront: %s: discard op failed\n",
 762                                            info->gd->disk_name);
 763                                 error = -EOPNOTSUPP;
 764                                 info->feature_discard = 0;
 765                                 info->feature_secdiscard = 0;
 766                                 queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
 767                                 queue_flag_clear(QUEUE_FLAG_SECDISCARD, rq);
 768                         }
 769                         __blk_end_request_all(req, error);
 770                         break;
 771                 case BLKIF_OP_FLUSH_DISKCACHE:
 772                 case BLKIF_OP_WRITE_BARRIER:
 773                         if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
 774                                 printk(KERN_WARNING "blkfront: %s: write %s op failed\n",
 775                                        info->flush_op == BLKIF_OP_WRITE_BARRIER ?
 776                                        "barrier" :  "flush disk cache",
 777                                        info->gd->disk_name);
 778                                 error = -EOPNOTSUPP;
 779                         }
 780                         if (unlikely(bret->status == BLKIF_RSP_ERROR &&
 781                                      info->shadow[id].req.u.rw.nr_segments == 0)) {
 782                                 printk(KERN_WARNING "blkfront: %s: empty write %s op failed\n",
 783                                        info->flush_op == BLKIF_OP_WRITE_BARRIER ?
 784                                        "barrier" :  "flush disk cache",
 785                                        info->gd->disk_name);
 786                                 error = -EOPNOTSUPP;
 787                         }
 788                         if (unlikely(error)) {
 789                                 if (error == -EOPNOTSUPP)
 790                                         error = 0;
 791                                 info->feature_flush = 0;
 792                                 info->flush_op = 0;
 793                                 xlvbd_flush(info);
 794                         }
 795                         /* fall through */
 796                 case BLKIF_OP_READ:
 797                 case BLKIF_OP_WRITE:
 798                         if (unlikely(bret->status != BLKIF_RSP_OKAY))
 799                                 dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "
 800                                         "request: %x\n", bret->status);
 801
 802                         __blk_end_request_all(req, error);
 803                         break;
 804                 default:
 805                         BUG();
 806                 }
 807         }
 808
 809         info->ring.rsp_cons = i;
 810
 811         if (i != info->ring.req_prod_pvt) {
 812                 int more_to_do;
 813                 RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
 814                 if (more_to_do)
 815                         goto again;
 816         } else
 817                 info->ring.sring->rsp_event = i + 1;
 818
 819         kick_pending_request_queues(info);
 820
 821         spin_unlock_irqrestore(&info->io_lock, flags);
 822
 823         return IRQ_HANDLED;
 824 }
 825
 826
 827 static int setup_blkring(struct xenbus_device *dev,
 828                          struct blkfront_info *info)
 829 {
 830         struct blkif_sring *sring;
 831         int err;
 832
 833         info->ring_ref = GRANT_INVALID_REF;
 834
 835         sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
 836         if (!sring) {
 837                 xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
 838                 return -ENOMEM;
 839         }
 840         SHARED_RING_INIT(sring);
 841         FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
 842
 843         sg_init_table(info->sg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
 844
 845         err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
 846         if (err < 0) {
 847                 free_page((unsigned long)sring);
 848                 info->ring.sring = NULL;
 849                 goto fail;
 850         }
 851         info->ring_ref = err;
 852
 853         err = xenbus_alloc_evtchn(dev, &info->evtchn);
 854         if (err)
 855                 goto fail;
 856
 857         err = bind_evtchn_to_irqhandler(info->evtchn,
 858                                         blkif_interrupt,
 859                                         IRQF_SAMPLE_RANDOM, "blkif", info);
 860         if (err <= 0) {
 861                 xenbus_dev_fatal(dev, err,
 862                                  "bind_evtchn_to_irqhandler failed");
 863                 goto fail;
 864         }
 865         info->irq = err;
 866
 867         return 0;
 868 fail:
 869         blkif_free(info, 0);
 870         return err;
 871 }
 872
 873
 874 /* Common code used when first setting up, and when resuming. */
 875 static int talk_to_blkback(struct xenbus_device *dev,
 876                            struct blkfront_info *info)
 877 {
 878         const char *message = NULL;
 879         struct xenbus_transaction xbt;
 880         int err;
 881
 882         /* Create shared ring, alloc event channel. */
 883         err = setup_blkring(dev, info);
 884         if (err)
 885                 goto out;
 886
 887 again:
 888         err = xenbus_transaction_start(&xbt);
 889         if (err) {
 890                 xenbus_dev_fatal(dev, err, "starting transaction");
 891                 goto destroy_blkring;
 892         }
 893
 894         err = xenbus_printf(xbt, dev->nodename,
 895                             "ring-ref", "%u", info->ring_ref);
 896         if (err) {
 897                 message = "writing ring-ref";
 898                 goto abort_transaction;
 899         }
 900         err = xenbus_printf(xbt, dev->nodename,
 901                             "event-channel", "%u", info->evtchn);
 902         if (err) {
 903                 message = "writing event-channel";
 904                 goto abort_transaction;
 905         }
 906         err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
 907                             XEN_IO_PROTO_ABI_NATIVE);
 908         if (err) {
 909                 message = "writing protocol";
 910                 goto abort_transaction;
 911         }
 912
 913         err = xenbus_transaction_end(xbt, 0);
 914         if (err) {
 915                 if (err == -EAGAIN)
 916                         goto again;
 917                 xenbus_dev_fatal(dev, err, "completing transaction");
 918                 goto destroy_blkring;
 919         }
 920
 921         xenbus_switch_state(dev, XenbusStateInitialised);
 922
 923         return 0;
 924
 925  abort_transaction:
 926         xenbus_transaction_end(xbt, 1);
 927         if (message)
 928                 xenbus_dev_fatal(dev, err, "%s", message);
 929  destroy_blkring:
 930         blkif_free(info, 0);
 931  out:
 932         return err;
 933 }
 934
 935 /**
 936  * Entry point to this code when a new device is created.  Allocate the basic
 937  * structures and the ring buffer for communication with the backend, and
 938  * inform the backend of the appropriate details for those.  Switch to
 939  * Initialised state.
 940  */
 941 static int blkfront_probe(struct xenbus_device *dev,
 942                           const struct xenbus_device_id *id)
 943 {
 944         int err, vdevice, i;
 945         struct blkfront_info *info;
 946
 947         /* FIXME: Use dynamic device id if this is not set. */
 948         err = xenbus_scanf(XBT_NIL, dev->nodename,
 949                            "virtual-device", "%i", &vdevice);
 950         if (err != 1) {
 951                 /* go looking in the extended area instead */
 952                 err = xenbus_scanf(XBT_NIL, dev->nodename, "virtual-device-ext",
 953                                    "%i", &vdevice);
 954                 if (err != 1) {
 955                         xenbus_dev_fatal(dev, err, "reading virtual-device");
 956                         return err;
 957                 }
 958         }
 959
 960         if (xen_hvm_domain()) {
 961                 char *type;
 962                 int len;
 963                 /* no unplug has been done: do not hook devices != xen vbds */
 964                 if (xen_platform_pci_unplug & XEN_UNPLUG_UNNECESSARY) {
 965                         int major;
 966
 967                         if (!VDEV_IS_EXTENDED(vdevice))
 968                                 major = BLKIF_MAJOR(vdevice);
 969                         else
 970                                 major = XENVBD_MAJOR;
 971
 972                         if (major != XENVBD_MAJOR) {
 973                                 printk(KERN_INFO
 974                                                 "%s: HVM does not support vbd %d as xen block device\n",
 975                                                 __FUNCTION__, vdevice);
 976                                 return -ENODEV;
 977                         }
 978                 }
 979                 /* do not create a PV cdrom device if we are an HVM guest */
 980                 type = xenbus_read(XBT_NIL, dev->nodename, "device-type", &len);
 981                 if (IS_ERR(type))
 982                         return -ENODEV;
 983                 if (strncmp(type, "cdrom", 5) == 0) {
 984                         kfree(type);
 985                         return -ENODEV;
 986                 }
 987                 kfree(type);
 988         }
 989         info = kzalloc(sizeof(*info), GFP_KERNEL);
 990         if (!info) {
 991                 xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
 992                 return -ENOMEM;
 993         }
 994
 995         mutex_init(&info->mutex);
 996         spin_lock_init(&info->io_lock);
 997         info->xbdev = dev;
 998         info->vdevice = vdevice;
 999         info->connected = BLKIF_STATE_DISCONNECTED;
1000         INIT_WORK(&info->work, blkif_restart_queue);
1001
1002         for (i = 0; i < BLK_RING_SIZE; i++)
1003                 info->shadow[i].req.u.rw.id = i+1;
1004         info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
1005
1006         /* Front end dir is a number, which is used as the id. */
1007         info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
1008         dev_set_drvdata(&dev->dev, info);
1009
1010         err = talk_to_blkback(dev, info);
1011         if (err) {
1012                 kfree(info);
1013                 dev_set_drvdata(&dev->dev, NULL);
1014                 return err;
1015         }
1016
1017         return 0;
1018 }
1019
1020
1021 static int blkif_recover(struct blkfront_info *info)
1022 {
1023         int i;
1024         struct blkif_request *req;
1025         struct blk_shadow *copy;
1026         int j;
1027
1028         /* Stage 1: Make a safe copy of the shadow state. */
1029         copy = kmalloc(sizeof(info->shadow),
1030                        GFP_NOIO | __GFP_REPEAT | __GFP_HIGH);
1031         if (!copy)
1032                 return -ENOMEM;
1033         memcpy(copy, info->shadow, sizeof(info->shadow));
1034
1035         /* Stage 2: Set up free list. */
1036         memset(&info->shadow, 0, sizeof(info->shadow));
1037         for (i = 0; i < BLK_RING_SIZE; i++)
1038                 info->shadow[i].req.u.rw.id = i+1;
1039         info->shadow_free = info->ring.req_prod_pvt;
1040         info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
1041
1042         /* Stage 3: Find pending requests and requeue them. */
1043         for (i = 0; i < BLK_RING_SIZE; i++) {
1044                 /* Not in use? */
1045                 if (!copy[i].request)
1046                         continue;
1047
1048                 /* Grab a request slot and copy shadow state into it. */
1049                 req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);
1050                 *req = copy[i].req;
1051
1052                 /* We get a new request id, and must reset the shadow state. */
1053                 req->u.rw.id = get_id_from_freelist(info);
1054                 memcpy(&info->shadow[req->u.rw.id], &copy[i], sizeof(copy[i]));
1055
1056                 if (req->operation != BLKIF_OP_DISCARD) {
1057                 /* Rewrite any grant references invalidated by susp/resume. */
1058                         for (j = 0; j < req->u.rw.nr_segments; j++)
1059                                 gnttab_grant_foreign_access_ref(
1060                                         req->u.rw.seg[j].gref,
1061                                         info->xbdev->otherend_id,
1062                                         pfn_to_mfn(info->shadow[req->u.rw.id].frame[j]),
1063                                         rq_data_dir(info->shadow[req->u.rw.id].request));
1064                 }
1065                 info->shadow[req->u.rw.id].req = *req;
1066
1067                 info->ring.req_prod_pvt++;
1068         }
1069
1070         kfree(copy);
1071
1072         xenbus_switch_state(info->xbdev, XenbusStateConnected);
1073
1074         spin_lock_irq(&info->io_lock);
1075
1076         /* Now safe for us to use the shared ring */
1077         info->connected = BLKIF_STATE_CONNECTED;
1078
1079         /* Send off requeued requests */
1080         flush_requests(info);
1081
1082         /* Kick any other new requests queued since we resumed */
1083         kick_pending_request_queues(info);
1084
1085         spin_unlock_irq(&info->io_lock);
1086
1087         return 0;
1088 }
1089
1090 /**
1091  * We are reconnecting to the backend, due to a suspend/resume, or a backend
1092  * driver restart.  We tear down our blkif structure and recreate it, but
1093  * leave the device-layer structures intact so that this is transparent to the
1094  * rest of the kernel.
1095  */
1096 static int blkfront_resume(struct xenbus_device *dev)
1097 {
1098         struct blkfront_info *info = dev_get_drvdata(&dev->dev);
1099         int err;
1100
1101         dev_dbg(&dev->dev, "blkfront_resume: %s\n", dev->nodename);
1102
1103         blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
1104
1105         err = talk_to_blkback(dev, info);
1106         if (info->connected == BLKIF_STATE_SUSPENDED && !err)
1107                 err = blkif_recover(info);
1108
1109         return err;
1110 }
1111
1112 static void
1113 blkfront_closing(struct blkfront_info *info)
1114 {
1115         struct xenbus_device *xbdev = info->xbdev;
1116         struct block_device *bdev = NULL;
1117
1118         mutex_lock(&info->mutex);
1119
1120         if (xbdev->state == XenbusStateClosing) {
1121                 mutex_unlock(&info->mutex);
1122                 return;
1123         }
1124
1125         if (info->gd)
1126                 bdev = bdget_disk(info->gd, 0);
1127
1128         mutex_unlock(&info->mutex);
1129
1130         if (!bdev) {
1131                 xenbus_frontend_closed(xbdev);
1132                 return;
1133         }
1134
1135         mutex_lock(&bdev->bd_mutex);
1136
1137         if (bdev->bd_openers) {
1138                 xenbus_dev_error(xbdev, -EBUSY,
1139                                  "Device in use; refusing to close");
1140                 xenbus_switch_state(xbdev, XenbusStateClosing);
1141         } else {
1142                 xlvbd_release_gendisk(info);
1143                 xenbus_frontend_closed(xbdev);
1144         }
1145
1146         mutex_unlock(&bdev->bd_mutex);
1147         bdput(bdev);
1148 }
1149
1150 static void blkfront_setup_discard(struct blkfront_info *info)
1151 {
1152         int err;
1153         char *type;
1154         unsigned int discard_granularity;
1155         unsigned int discard_alignment;
1156         unsigned int discard_secure;
1157
1158         type = xenbus_read(XBT_NIL, info->xbdev->otherend, "type", NULL);
1159         if (IS_ERR(type))
1160                 return;
1161
1162         info->feature_secdiscard = 0;
1163         if (strncmp(type, "phy", 3) == 0) {
1164                 err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
1165                         "discard-granularity", "%u", &discard_granularity,
1166                         "discard-alignment", "%u", &discard_alignment,
1167                         NULL);
1168                 if (!err) {
1169                         info->feature_discard = 1;
1170                         info->discard_granularity = discard_granularity;
1171                         info->discard_alignment = discard_alignment;
1172                 }
1173                 err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
1174                             "discard-secure", "%d", &discard_secure,
1175                             NULL);
1176                 if (!err)
1177                         info->feature_secdiscard = discard_secure;
1178
1179         } else if (strncmp(type, "file", 4) == 0)
1180                 info->feature_discard = 1;
1181
1182         kfree(type);
1183 }
1184
1185 /*
1186  * Invoked when the backend is finally 'ready' (and has told produced
1187  * the details about the physical device - #sectors, size, etc).
1188  */
1189 static void blkfront_connect(struct blkfront_info *info)
1190 {
1191         unsigned long long sectors;
1192         unsigned long sector_size;
1193         unsigned int binfo;
1194         int err;
1195         int barrier, flush, discard;
1196
1197         switch (info->connected) {
1198         case BLKIF_STATE_CONNECTED:
1199                 /*
1200                  * Potentially, the back-end may be signalling
1201                  * a capacity change; update the capacity.
1202                  */
1203                 err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
1204                                    "sectors", "%Lu", &sectors);
1205                 if (XENBUS_EXIST_ERR(err))
1206                         return;
1207                 printk(KERN_INFO "Setting capacity to %Lu\n",
1208                        sectors);
1209                 set_capacity(info->gd, sectors);
1210                 revalidate_disk(info->gd);
1211
1212                 /* fall through */
1213         case BLKIF_STATE_SUSPENDED:
1214                 return;
1215
1216         default:
1217                 break;
1218         }
1219
1220         dev_dbg(&info->xbdev->dev, "%s:%s.\n",
1221                 __func__, info->xbdev->otherend);
1222
1223         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
1224                             "sectors", "%llu", &sectors,
1225                             "info", "%u", &binfo,
1226                             "sector-size", "%lu", &sector_size,
1227                             NULL);
1228         if (err) {
1229                 xenbus_dev_fatal(info->xbdev, err,
1230                                  "reading backend fields at %s",
1231                                  info->xbdev->otherend);
1232                 return;
1233         }
1234
1235         info->feature_flush = 0;
1236         info->flush_op = 0;
1237
1238         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
1239                             "feature-barrier", "%d", &barrier,
1240                             NULL);
1241
1242         /*
1243          * If there's no "feature-barrier" defined, then it means
1244          * we're dealing with a very old backend which writes
1245          * synchronously; nothing to do.
1246          *
1247          * If there are barriers, then we use flush.
1248          */
1249         if (!err && barrier) {
1250                 info->feature_flush = REQ_FLUSH | REQ_FUA;
1251                 info->flush_op = BLKIF_OP_WRITE_BARRIER;
1252         }
1253         /*
1254          * And if there is "feature-flush-cache" use that above
1255          * barriers.
1256          */
1257         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
1258                             "feature-flush-cache", "%d", &flush,
1259                             NULL);
1260
1261         if (!err && flush) {
1262                 info->feature_flush = REQ_FLUSH;
1263                 info->flush_op = BLKIF_OP_FLUSH_DISKCACHE;
1264         }
1265
1266         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
1267                             "feature-discard", "%d", &discard,
1268                             NULL);
1269
1270         if (!err && discard)
1271                 blkfront_setup_discard(info);
1272
1273         err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
1274         if (err) {
1275                 xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
1276                                  info->xbdev->otherend);
1277                 return;
1278         }
1279
1280         xenbus_switch_state(info->xbdev, XenbusStateConnected);
1281
1282         /* Kick pending requests. */
1283         spin_lock_irq(&info->io_lock);
1284         info->connected = BLKIF_STATE_CONNECTED;
1285         kick_pending_request_queues(info);
1286         spin_unlock_irq(&info->io_lock);
1287
1288         add_disk(info->gd);
1289
1290         info->is_ready = 1;
1291 }
1292
1293 /**
1294  * Callback received when the backend's state changes.
1295  */
1296 static void blkback_changed(struct xenbus_device *dev,
1297                             enum xenbus_state backend_state)
1298 {
1299         struct blkfront_info *info = dev_get_drvdata(&dev->dev);
1300
1301         dev_dbg(&dev->dev, "blkfront:blkback_changed to state %d.\n", backend_state);
1302
1303         switch (backend_state) {
1304         case XenbusStateInitialising:
1305         case XenbusStateInitWait:
1306         case XenbusStateInitialised:
1307         case XenbusStateReconfiguring:
1308         case XenbusStateReconfigured:
1309         case XenbusStateUnknown:
1310         case XenbusStateClosed:
1311                 break;
1312
1313         case XenbusStateConnected:
1314                 blkfront_connect(info);
1315                 break;
1316
1317         case XenbusStateClosing:
1318                 blkfront_closing(info);
1319                 break;
1320         }
1321 }
1322
1323 static int blkfront_remove(struct xenbus_device *xbdev)
1324 {
1325         struct blkfront_info *info = dev_get_drvdata(&xbdev->dev);
1326         struct block_device *bdev = NULL;
1327         struct gendisk *disk;
1328
1329         dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);
1330
1331         blkif_free(info, 0);
1332
1333         mutex_lock(&info->mutex);
1334
1335         disk = info->gd;
1336         if (disk)
1337                 bdev = bdget_disk(disk, 0);
1338
1339         info->xbdev = NULL;
1340         mutex_unlock(&info->mutex);
1341
1342         if (!bdev) {
1343                 kfree(info);
1344                 return 0;
1345         }
1346
1347         /*
1348          * The xbdev was removed before we reached the Closed
1349          * state. See if it's safe to remove the disk. If the bdev
1350          * isn't closed yet, we let release take care of it.
1351          */
1352
1353         mutex_lock(&bdev->bd_mutex);
1354         info = disk->private_data;
1355
1356         dev_warn(disk_to_dev(disk),
1357                  "%s was hot-unplugged, %d stale handles\n",
1358                  xbdev->nodename, bdev->bd_openers);
1359
1360         if (info && !bdev->bd_openers) {
1361                 xlvbd_release_gendisk(info);
1362                 disk->private_data = NULL;
1363                 kfree(info);
1364         }
1365
1366         mutex_unlock(&bdev->bd_mutex);
1367         bdput(bdev);
1368
1369         return 0;
1370 }
1371
1372 static int blkfront_is_ready(struct xenbus_device *dev)
1373 {
1374         struct blkfront_info *info = dev_get_drvdata(&dev->dev);
1375
1376         return info->is_ready && info->xbdev;
1377 }
1378
1379 static int blkif_open(struct block_device *bdev, fmode_t mode)
1380 {
1381         struct gendisk *disk = bdev->bd_disk;
1382         struct blkfront_info *info;
1383         int err = 0;
1384
1385         mutex_lock(&blkfront_mutex);
1386
1387         info = disk->private_data;
1388         if (!info) {
1389                 /* xbdev gone */
1390                 err = -ERESTARTSYS;
1391                 goto out;
1392         }
1393
1394         mutex_lock(&info->mutex);
1395
1396         if (!info->gd)
1397                 /* xbdev is closed */
1398                 err = -ERESTARTSYS;
1399
1400         mutex_unlock(&info->mutex);
1401
1402 out:
1403         mutex_unlock(&blkfront_mutex);
1404         return err;
1405 }
1406
1407 static int blkif_release(struct gendisk *disk, fmode_t mode)
1408 {
1409         struct blkfront_info *info = disk->private_data;
1410         struct block_device *bdev;
1411         struct xenbus_device *xbdev;
1412
1413         mutex_lock(&blkfront_mutex);
1414
1415         bdev = bdget_disk(disk, 0);
1416
1417         if (bdev->bd_openers)
1418                 goto out;
1419
1420         /*
1421          * Check if we have been instructed to close. We will have
1422          * deferred this request, because the bdev was still open.
1423          */
1424
1425         mutex_lock(&info->mutex);
1426         xbdev = info->xbdev;
1427
1428         if (xbdev && xbdev->state == XenbusStateClosing) {
1429                 /* pending switch to state closed */
1430                 dev_info(disk_to_dev(bdev->bd_disk), "releasing disk\n");
1431                 xlvbd_release_gendisk(info);
1432                 xenbus_frontend_closed(info->xbdev);
1433         }
1434
1435         mutex_unlock(&info->mutex);
1436
1437         if (!xbdev) {
1438                 /* sudden device removal */
1439                 dev_info(disk_to_dev(bdev->bd_disk), "releasing disk\n");
1440                 xlvbd_release_gendisk(info);
1441                 disk->private_data = NULL;
1442                 kfree(info);
1443         }
1444
1445 out:
1446         bdput(bdev);
1447         mutex_unlock(&blkfront_mutex);
1448         return 0;
1449 }
1450
1451 static const struct block_device_operations xlvbd_block_fops =
1452 {
1453         .owner = THIS_MODULE,
1454         .open = blkif_open,
1455         .release = blkif_release,
1456         .getgeo = blkif_getgeo,
1457         .ioctl = blkif_ioctl,
1458 };
1459
1460
1461 static const struct xenbus_device_id blkfront_ids[] = {
1462         { "vbd" },
1463         { "" }
1464 };
1465
1466 static DEFINE_XENBUS_DRIVER(blkfront, ,
1467         .probe = blkfront_probe,
1468         .remove = blkfront_remove,
1469         .resume = blkfront_resume,
1470         .otherend_changed = blkback_changed,
1471         .is_ready = blkfront_is_ready,
1472 );
1473
1474 static int __init xlblk_init(void)
1475 {
1476         int ret;
1477
1478         if (!xen_domain())
1479                 return -ENODEV;
1480
1481         if (xen_hvm_domain() && !xen_platform_pci_unplug)
1482                 return -ENODEV;
1483
1484         if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
1485                 printk(KERN_WARNING "xen_blk: can't get major %d with name %s\n",
1486                        XENVBD_MAJOR, DEV_NAME);
1487                 return -ENODEV;
1488         }
1489
1490         ret = xenbus_register_frontend(&blkfront_driver);
1491         if (ret) {
1492                 unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
1493                 return ret;
1494         }
1495
1496         return 0;
1497 }
1498 module_init(xlblk_init);
1499
1500
1501 static void __exit xlblk_exit(void)
1502 {
1503         xenbus_unregister_driver(&blkfront_driver);
1504         unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
1505         kfree(minors);
1506 }
1507 module_exit(xlblk_exit);
1508
1509 MODULE_DESCRIPTION("Xen virtual block device frontend");
1510 MODULE_LICENSE("GPL");
1511 MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
1512 MODULE_ALIAS("xen:vbd");
1513 MODULE_ALIAS("xenblk");