drivers/md/raid10.c

   1 /*
   2  * raid10.c : Multiple Devices driver for Linux
   3  *
   4  * Copyright (C) 2000-2004 Neil Brown
   5  *
   6  * RAID-10 support for md.
   7  *
   8  * Base on code in raid1.c.  See raid1.c for futher copyright information.
   9  *
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2, or (at your option)
  14  * any later version.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * (for example /usr/src/linux/COPYING); if not, write to the Free
  18  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #include "dm-bio-list.h"
  22 #include <linux/raid/raid10.h>
  23 #include <linux/raid/bitmap.h>
  24
  25 /*
  26  * RAID10 provides a combination of RAID0 and RAID1 functionality.
  27  * The layout of data is defined by
  28  *    chunk_size
  29  *    raid_disks
  30  *    near_copies (stored in low byte of layout)
  31  *    far_copies (stored in second byte of layout)
  32  *    far_offset (stored in bit 16 of layout )
  33  *
  34  * The data to be stored is divided into chunks using chunksize.
  35  * Each device is divided into far_copies sections.
  36  * In each section, chunks are laid out in a style similar to raid0, but
  37  * near_copies copies of each chunk is stored (each on a different drive).
  38  * The starting device for each section is offset near_copies from the starting
  39  * device of the previous section.
  40  * Thus they are (near_copies*far_copies) of each chunk, and each is on a different
  41  * drive.
  42  * near_copies and far_copies must be at least one, and their product is at most
  43  * raid_disks.
  44  *
  45  * If far_offset is true, then the far_copies are handled a bit differently.
  46  * The copies are still in different stripes, but instead of be very far apart
  47  * on disk, there are adjacent stripes.
  48  */
  49
  50 /*
  51  * Number of guaranteed r10bios in case of extreme VM load:
  52  */
  53 #define NR_RAID10_BIOS 256
  54
  55 static void unplug_slaves(mddev_t *mddev);
  56
  57 static void allow_barrier(conf_t *conf);
  58 static void lower_barrier(conf_t *conf);
  59
  60 static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
  61 {
  62         conf_t *conf = data;
  63         r10bio_t *r10_bio;
  64         int size = offsetof(struct r10bio_s, devs[conf->copies]);
  65
  66         /* allocate a r10bio with room for raid_disks entries in the bios array */
  67         r10_bio = kzalloc(size, gfp_flags);
  68         if (!r10_bio)
  69                 unplug_slaves(conf->mddev);
  70
  71         return r10_bio;
  72 }
  73
  74 static void r10bio_pool_free(void *r10_bio, void *data)
  75 {
  76         kfree(r10_bio);
  77 }
  78
  79 /* Maximum size of each resync request */
  80 #define RESYNC_BLOCK_SIZE (64*1024)
  81 #define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
  82 /* amount of memory to reserve for resync requests */
  83 #define RESYNC_WINDOW (1024*1024)
  84 /* maximum number of concurrent requests, memory permitting */
  85 #define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
  86
  87 /*
  88  * When performing a resync, we need to read and compare, so
  89  * we need as many pages are there are copies.
  90  * When performing a recovery, we need 2 bios, one for read,
  91  * one for write (we recover only one drive per r10buf)
  92  *
  93  */
  94 static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
  95 {
  96         conf_t *conf = data;
  97         struct page *page;
  98         r10bio_t *r10_bio;
  99         struct bio *bio;
 100         int i, j;
 101         int nalloc;
 102
 103         r10_bio = r10bio_pool_alloc(gfp_flags, conf);
 104         if (!r10_bio) {
 105                 unplug_slaves(conf->mddev);
 106                 return NULL;
 107         }
 108
 109         if (test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery))
 110                 nalloc = conf->copies; /* resync */
 111         else
 112                 nalloc = 2; /* recovery */
 113
 114         /*
 115          * Allocate bios.
 116          */
 117         for (j = nalloc ; j-- ; ) {
 118                 bio = bio_alloc(gfp_flags, RESYNC_PAGES);
 119                 if (!bio)
 120                         goto out_free_bio;
 121                 r10_bio->devs[j].bio = bio;
 122         }
 123         /*
 124          * Allocate RESYNC_PAGES data pages and attach them
 125          * where needed.
 126          */
 127         for (j = 0 ; j < nalloc; j++) {
 128                 bio = r10_bio->devs[j].bio;
 129                 for (i = 0; i < RESYNC_PAGES; i++) {
 130                         page = alloc_page(gfp_flags);
 131                         if (unlikely(!page))
 132                                 goto out_free_pages;
 133
 134                         bio->bi_io_vec[i].bv_page = page;
 135                 }
 136         }
 137
 138         return r10_bio;
 139
 140 out_free_pages:
 141         for ( ; i > 0 ; i--)
 142                 safe_put_page(bio->bi_io_vec[i-1].bv_page);
 143         while (j--)
 144                 for (i = 0; i < RESYNC_PAGES ; i++)
 145                         safe_put_page(r10_bio->devs[j].bio->bi_io_vec[i].bv_page);
 146         j = -1;
 147 out_free_bio:
 148         while ( ++j < nalloc )
 149                 bio_put(r10_bio->devs[j].bio);
 150         r10bio_pool_free(r10_bio, conf);
 151         return NULL;
 152 }
 153
 154 static void r10buf_pool_free(void *__r10_bio, void *data)
 155 {
 156         int i;
 157         conf_t *conf = data;
 158         r10bio_t *r10bio = __r10_bio;
 159         int j;
 160
 161         for (j=0; j < conf->copies; j++) {
 162                 struct bio *bio = r10bio->devs[j].bio;
 163                 if (bio) {
 164                         for (i = 0; i < RESYNC_PAGES; i++) {
 165                                 safe_put_page(bio->bi_io_vec[i].bv_page);
 166                                 bio->bi_io_vec[i].bv_page = NULL;
 167                         }
 168                         bio_put(bio);
 169                 }
 170         }
 171         r10bio_pool_free(r10bio, conf);
 172 }
 173
 174 static void put_all_bios(conf_t *conf, r10bio_t *r10_bio)
 175 {
 176         int i;
 177
 178         for (i = 0; i < conf->copies; i++) {
 179                 struct bio **bio = & r10_bio->devs[i].bio;
 180                 if (*bio && *bio != IO_BLOCKED)
 181                         bio_put(*bio);
 182                 *bio = NULL;
 183         }
 184 }
 185
 186 static void free_r10bio(r10bio_t *r10_bio)
 187 {
 188         conf_t *conf = mddev_to_conf(r10_bio->mddev);
 189
 190         /*
 191          * Wake up any possible resync thread that waits for the device
 192          * to go idle.
 193          */
 194         allow_barrier(conf);
 195
 196         put_all_bios(conf, r10_bio);
 197         mempool_free(r10_bio, conf->r10bio_pool);
 198 }
 199
 200 static void put_buf(r10bio_t *r10_bio)
 201 {
 202         conf_t *conf = mddev_to_conf(r10_bio->mddev);
 203
 204         mempool_free(r10_bio, conf->r10buf_pool);
 205
 206         lower_barrier(conf);
 207 }
 208
 209 static void reschedule_retry(r10bio_t *r10_bio)
 210 {
 211         unsigned long flags;
 212         mddev_t *mddev = r10_bio->mddev;
 213         conf_t *conf = mddev_to_conf(mddev);
 214
 215         spin_lock_irqsave(&conf->device_lock, flags);
 216         list_add(&r10_bio->retry_list, &conf->retry_list);
 217         conf->nr_queued ++;
 218         spin_unlock_irqrestore(&conf->device_lock, flags);
 219
 220         /* wake up frozen array... */
 221         wake_up(&conf->wait_barrier);
 222
 223         md_wakeup_thread(mddev->thread);
 224 }
 225
 226 /*
 227  * raid_end_bio_io() is called when we have finished servicing a mirrored
 228  * operation and are ready to return a success/failure code to the buffer
 229  * cache layer.
 230  */
 231 static void raid_end_bio_io(r10bio_t *r10_bio)
 232 {
 233         struct bio *bio = r10_bio->master_bio;
 234
 235         bio_endio(bio,
 236                 test_bit(R10BIO_Uptodate, &r10_bio->state) ? 0 : -EIO);
 237         free_r10bio(r10_bio);
 238 }
 239
 240 /*
 241  * Update disk head position estimator based on IRQ completion info.
 242  */
 243 static inline void update_head_pos(int slot, r10bio_t *r10_bio)
 244 {
 245         conf_t *conf = mddev_to_conf(r10_bio->mddev);
 246
 247         conf->mirrors[r10_bio->devs[slot].devnum].head_position =
 248                 r10_bio->devs[slot].addr + (r10_bio->sectors);
 249 }
 250
 251 static void raid10_end_read_request(struct bio *bio, int error)
 252 {
 253         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 254         r10bio_t * r10_bio = (r10bio_t *)(bio->bi_private);
 255         int slot, dev;
 256         conf_t *conf = mddev_to_conf(r10_bio->mddev);
 257
 258
 259         slot = r10_bio->read_slot;
 260         dev = r10_bio->devs[slot].devnum;
 261         /*
 262          * this branch is our 'one mirror IO has finished' event handler:
 263          */
 264         update_head_pos(slot, r10_bio);
 265
 266         if (uptodate) {
 267                 /*
 268                  * Set R10BIO_Uptodate in our master bio, so that
 269                  * we will return a good error code to the higher
 270                  * levels even if IO on some other mirrored buffer fails.
 271                  *
 272                  * The 'master' represents the composite IO operation to
 273                  * user-side. So if something waits for IO, then it will
 274                  * wait for the 'master' bio.
 275                  */
 276                 set_bit(R10BIO_Uptodate, &r10_bio->state);
 277                 raid_end_bio_io(r10_bio);
 278         } else {
 279                 /*
 280                  * oops, read error:
 281                  */
 282                 char b[BDEVNAME_SIZE];
 283                 if (printk_ratelimit())
 284                         printk(KERN_ERR "raid10: %s: rescheduling sector %llu\n",
 285                                bdevname(conf->mirrors[dev].rdev->bdev,b), (unsigned long long)r10_bio->sector);
 286                 reschedule_retry(r10_bio);
 287         }
 288
 289         rdev_dec_pending(conf->mirrors[dev].rdev, conf->mddev);
 290 }
 291
 292 static void raid10_end_write_request(struct bio *bio, int error)
 293 {
 294         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 295         r10bio_t * r10_bio = (r10bio_t *)(bio->bi_private);
 296         int slot, dev;
 297         conf_t *conf = mddev_to_conf(r10_bio->mddev);
 298
 299         for (slot = 0; slot < conf->copies; slot++)
 300                 if (r10_bio->devs[slot].bio == bio)
 301                         break;
 302         dev = r10_bio->devs[slot].devnum;
 303
 304         /*
 305          * this branch is our 'one mirror IO has finished' event handler:
 306          */
 307         if (!uptodate) {
 308                 md_error(r10_bio->mddev, conf->mirrors[dev].rdev);
 309                 /* an I/O failed, we can't clear the bitmap */
 310                 set_bit(R10BIO_Degraded, &r10_bio->state);
 311         } else
 312                 /*
 313                  * Set R10BIO_Uptodate in our master bio, so that
 314                  * we will return a good error code for to the higher
 315                  * levels even if IO on some other mirrored buffer fails.
 316                  *
 317                  * The 'master' represents the composite IO operation to
 318                  * user-side. So if something waits for IO, then it will
 319                  * wait for the 'master' bio.
 320                  */
 321                 set_bit(R10BIO_Uptodate, &r10_bio->state);
 322
 323         update_head_pos(slot, r10_bio);
 324
 325         /*
 326          *
 327          * Let's see if all mirrored write operations have finished
 328          * already.
 329          */
 330         if (atomic_dec_and_test(&r10_bio->remaining)) {
 331                 /* clear the bitmap if all writes complete successfully */
 332                 bitmap_endwrite(r10_bio->mddev->bitmap, r10_bio->sector,
 333                                 r10_bio->sectors,
 334                                 !test_bit(R10BIO_Degraded, &r10_bio->state),
 335                                 0);
 336                 md_write_end(r10_bio->mddev);
 337                 raid_end_bio_io(r10_bio);
 338         }
 339
 340         rdev_dec_pending(conf->mirrors[dev].rdev, conf->mddev);
 341 }
 342
 343
 344 /*
 345  * RAID10 layout manager
 346  * Aswell as the chunksize and raid_disks count, there are two
 347  * parameters: near_copies and far_copies.
 348  * near_copies * far_copies must be <= raid_disks.
 349  * Normally one of these will be 1.
 350  * If both are 1, we get raid0.
 351  * If near_copies == raid_disks, we get raid1.
 352  *
 353  * Chunks are layed out in raid0 style with near_copies copies of the
 354  * first chunk, followed by near_copies copies of the next chunk and
 355  * so on.
 356  * If far_copies > 1, then after 1/far_copies of the array has been assigned
 357  * as described above, we start again with a device offset of near_copies.
 358  * So we effectively have another copy of the whole array further down all
 359  * the drives, but with blocks on different drives.
 360  * With this layout, and block is never stored twice on the one device.
 361  *
 362  * raid10_find_phys finds the sector offset of a given virtual sector
 363  * on each device that it is on.
 364  *
 365  * raid10_find_virt does the reverse mapping, from a device and a
 366  * sector offset to a virtual address
 367  */
 368
 369 static void raid10_find_phys(conf_t *conf, r10bio_t *r10bio)
 370 {
 371         int n,f;
 372         sector_t sector;
 373         sector_t chunk;
 374         sector_t stripe;
 375         int dev;
 376
 377         int slot = 0;
 378
 379         /* now calculate first sector/dev */
 380         chunk = r10bio->sector >> conf->chunk_shift;
 381         sector = r10bio->sector & conf->chunk_mask;
 382
 383         chunk *= conf->near_copies;
 384         stripe = chunk;
 385         dev = sector_div(stripe, conf->raid_disks);
 386         if (conf->far_offset)
 387                 stripe *= conf->far_copies;
 388
 389         sector += stripe << conf->chunk_shift;
 390
 391         /* and calculate all the others */
 392         for (n=0; n < conf->near_copies; n++) {
 393                 int d = dev;
 394                 sector_t s = sector;
 395                 r10bio->devs[slot].addr = sector;
 396                 r10bio->devs[slot].devnum = d;
 397                 slot++;
 398
 399                 for (f = 1; f < conf->far_copies; f++) {
 400                         d += conf->near_copies;
 401                         if (d >= conf->raid_disks)
 402                                 d -= conf->raid_disks;
 403                         s += conf->stride;
 404                         r10bio->devs[slot].devnum = d;
 405                         r10bio->devs[slot].addr = s;
 406                         slot++;
 407                 }
 408                 dev++;
 409                 if (dev >= conf->raid_disks) {
 410                         dev = 0;
 411                         sector += (conf->chunk_mask + 1);
 412                 }
 413         }
 414         BUG_ON(slot != conf->copies);
 415 }
 416
 417 static sector_t raid10_find_virt(conf_t *conf, sector_t sector, int dev)
 418 {
 419         sector_t offset, chunk, vchunk;
 420
 421         offset = sector & conf->chunk_mask;
 422         if (conf->far_offset) {
 423                 int fc;
 424                 chunk = sector >> conf->chunk_shift;
 425                 fc = sector_div(chunk, conf->far_copies);
 426                 dev -= fc * conf->near_copies;
 427                 if (dev < 0)
 428                         dev += conf->raid_disks;
 429         } else {
 430                 while (sector >= conf->stride) {
 431                         sector -= conf->stride;
 432                         if (dev < conf->near_copies)
 433                                 dev += conf->raid_disks - conf->near_copies;
 434                         else
 435                                 dev -= conf->near_copies;
 436                 }
 437                 chunk = sector >> conf->chunk_shift;
 438         }
 439         vchunk = chunk * conf->raid_disks + dev;
 440         sector_div(vchunk, conf->near_copies);
 441         return (vchunk << conf->chunk_shift) + offset;
 442 }
 443
 444 /**
 445  *      raid10_mergeable_bvec -- tell bio layer if a two requests can be merged
 446  *      @q: request queue
 447  *      @bvm: properties of new bio
 448  *      @biovec: the request that could be merged to it.
 449  *
 450  *      Return amount of bytes we can accept at this offset
 451  *      If near_copies == raid_disk, there are no striping issues,
 452  *      but in that case, the function isn't called at all.
 453  */
 454 static int raid10_mergeable_bvec(struct request_queue *q,
 455                                  struct bvec_merge_data *bvm,
 456                                  struct bio_vec *biovec)
 457 {
 458         mddev_t *mddev = q->queuedata;
 459         sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 460         int max;
 461         unsigned int chunk_sectors = mddev->chunk_size >> 9;
 462         unsigned int bio_sectors = bvm->bi_size >> 9;
 463
 464         max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
 465         if (max < 0) max = 0; /* bio_add cannot handle a negative return */
 466         if (max <= biovec->bv_len && bio_sectors == 0)
 467                 return biovec->bv_len;
 468         else
 469                 return max;
 470 }
 471
 472 /*
 473  * This routine returns the disk from which the requested read should
 474  * be done. There is a per-array 'next expected sequential IO' sector
 475  * number - if this matches on the next IO then we use the last disk.
 476  * There is also a per-disk 'last know head position' sector that is
 477  * maintained from IRQ contexts, both the normal and the resync IO
 478  * completion handlers update this position correctly. If there is no
 479  * perfect sequential match then we pick the disk whose head is closest.
 480  *
 481  * If there are 2 mirrors in the same 2 devices, performance degrades
 482  * because position is mirror, not device based.
 483  *
 484  * The rdev for the device selected will have nr_pending incremented.
 485  */
 486
 487 /*
 488  * FIXME: possibly should rethink readbalancing and do it differently
 489  * depending on near_copies / far_copies geometry.
 490  */
 491 static int read_balance(conf_t *conf, r10bio_t *r10_bio)
 492 {
 493         const unsigned long this_sector = r10_bio->sector;
 494         int disk, slot, nslot;
 495         const int sectors = r10_bio->sectors;
 496         sector_t new_distance, current_distance;
 497         mdk_rdev_t *rdev;
 498
 499         raid10_find_phys(conf, r10_bio);
 500         rcu_read_lock();
 501         /*
 502          * Check if we can balance. We can balance on the whole
 503          * device if no resync is going on (recovery is ok), or below
 504          * the resync window. We take the first readable disk when
 505          * above the resync window.
 506          */
 507         if (conf->mddev->recovery_cp < MaxSector
 508             && (this_sector + sectors >= conf->next_resync)) {
 509                 /* make sure that disk is operational */
 510                 slot = 0;
 511                 disk = r10_bio->devs[slot].devnum;
 512
 513                 while ((rdev = rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
 514                        r10_bio->devs[slot].bio == IO_BLOCKED ||
 515                        !test_bit(In_sync, &rdev->flags)) {
 516                         slot++;
 517                         if (slot == conf->copies) {
 518                                 slot = 0;
 519                                 disk = -1;
 520                                 break;
 521                         }
 522                         disk = r10_bio->devs[slot].devnum;
 523                 }
 524                 goto rb_out;
 525         }
 526
 527
 528         /* make sure the disk is operational */
 529         slot = 0;
 530         disk = r10_bio->devs[slot].devnum;
 531         while ((rdev=rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
 532                r10_bio->devs[slot].bio == IO_BLOCKED ||
 533                !test_bit(In_sync, &rdev->flags)) {
 534                 slot ++;
 535                 if (slot == conf->copies) {
 536                         disk = -1;
 537                         goto rb_out;
 538                 }
 539                 disk = r10_bio->devs[slot].devnum;
 540         }
 541
 542
 543         current_distance = abs(r10_bio->devs[slot].addr -
 544                                conf->mirrors[disk].head_position);
 545
 546         /* Find the disk whose head is closest,
 547          * or - for far > 1 - find the closest to partition beginning */
 548
 549         for (nslot = slot; nslot < conf->copies; nslot++) {
 550                 int ndisk = r10_bio->devs[nslot].devnum;
 551
 552
 553                 if ((rdev=rcu_dereference(conf->mirrors[ndisk].rdev)) == NULL ||
 554                     r10_bio->devs[nslot].bio == IO_BLOCKED ||
 555                     !test_bit(In_sync, &rdev->flags))
 556                         continue;
 557
 558                 /* This optimisation is debatable, and completely destroys
 559                  * sequential read speed for 'far copies' arrays.  So only
 560                  * keep it for 'near' arrays, and review those later.
 561                  */
 562                 if (conf->near_copies > 1 && !atomic_read(&rdev->nr_pending)) {
 563                         disk = ndisk;
 564                         slot = nslot;
 565                         break;
 566                 }
 567
 568                 /* for far > 1 always use the lowest address */
 569                 if (conf->far_copies > 1)
 570                         new_distance = r10_bio->devs[nslot].addr;
 571                 else
 572                         new_distance = abs(r10_bio->devs[nslot].addr -
 573                                            conf->mirrors[ndisk].head_position);
 574                 if (new_distance < current_distance) {
 575                         current_distance = new_distance;
 576                         disk = ndisk;
 577                         slot = nslot;
 578                 }
 579         }
 580
 581 rb_out:
 582         r10_bio->read_slot = slot;
 583 /*      conf->next_seq_sect = this_sector + sectors;*/
 584
 585         if (disk >= 0 && (rdev=rcu_dereference(conf->mirrors[disk].rdev))!= NULL)
 586                 atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
 587         else
 588                 disk = -1;
 589         rcu_read_unlock();
 590
 591         return disk;
 592 }
 593
 594 static void unplug_slaves(mddev_t *mddev)
 595 {
 596         conf_t *conf = mddev_to_conf(mddev);
 597         int i;
 598
 599         rcu_read_lock();
 600         for (i=0; i<mddev->raid_disks; i++) {
 601                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
 602                 if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
 603                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
 604
 605                         atomic_inc(&rdev->nr_pending);
 606                         rcu_read_unlock();
 607
 608                         blk_unplug(r_queue);
 609
 610                         rdev_dec_pending(rdev, mddev);
 611                         rcu_read_lock();
 612                 }
 613         }
 614         rcu_read_unlock();
 615 }
 616
 617 static void raid10_unplug(struct request_queue *q)
 618 {
 619         mddev_t *mddev = q->queuedata;
 620
 621         unplug_slaves(q->queuedata);
 622         md_wakeup_thread(mddev->thread);
 623 }
 624
 625 static int raid10_congested(void *data, int bits)
 626 {
 627         mddev_t *mddev = data;
 628         conf_t *conf = mddev_to_conf(mddev);
 629         int i, ret = 0;
 630
 631         rcu_read_lock();
 632         for (i = 0; i < mddev->raid_disks && ret == 0; i++) {
 633                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
 634                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 635                         struct request_queue *q = bdev_get_queue(rdev->bdev);
 636
 637                         ret |= bdi_congested(&q->backing_dev_info, bits);
 638                 }
 639         }
 640         rcu_read_unlock();
 641         return ret;
 642 }
 643
 644 static int flush_pending_writes(conf_t *conf)
 645 {
 646         /* Any writes that have been queued but are awaiting
 647          * bitmap updates get flushed here.
 648          * We return 1 if any requests were actually submitted.
 649          */
 650         int rv = 0;
 651
 652         spin_lock_irq(&conf->device_lock);
 653
 654         if (conf->pending_bio_list.head) {
 655                 struct bio *bio;
 656                 bio = bio_list_get(&conf->pending_bio_list);
 657                 blk_remove_plug(conf->mddev->queue);
 658                 spin_unlock_irq(&conf->device_lock);
 659                 /* flush any pending bitmap writes to disk
 660                  * before proceeding w/ I/O */
 661                 bitmap_unplug(conf->mddev->bitmap);
 662
 663                 while (bio) { /* submit pending writes */
 664                         struct bio *next = bio->bi_next;
 665                         bio->bi_next = NULL;
 666                         generic_make_request(bio);
 667                         bio = next;
 668                 }
 669                 rv = 1;
 670         } else
 671                 spin_unlock_irq(&conf->device_lock);
 672         return rv;
 673 }
 674 /* Barriers....
 675  * Sometimes we need to suspend IO while we do something else,
 676  * either some resync/recovery, or reconfigure the array.
 677  * To do this we raise a 'barrier'.
 678  * The 'barrier' is a counter that can be raised multiple times
 679  * to count how many activities are happening which preclude
 680  * normal IO.
 681  * We can only raise the barrier if there is no pending IO.
 682  * i.e. if nr_pending == 0.
 683  * We choose only to raise the barrier if no-one is waiting for the
 684  * barrier to go down.  This means that as soon as an IO request
 685  * is ready, no other operations which require a barrier will start
 686  * until the IO request has had a chance.
 687  *
 688  * So: regular IO calls 'wait_barrier'.  When that returns there
 689  *    is no backgroup IO happening,  It must arrange to call
 690  *    allow_barrier when it has finished its IO.
 691  * backgroup IO calls must call raise_barrier.  Once that returns
 692  *    there is no normal IO happeing.  It must arrange to call
 693  *    lower_barrier when the particular background IO completes.
 694  */
 695
 696 static void raise_barrier(conf_t *conf, int force)
 697 {
 698         BUG_ON(force && !conf->barrier);
 699         spin_lock_irq(&conf->resync_lock);
 700
 701         /* Wait until no block IO is waiting (unless 'force') */
 702         wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
 703                             conf->resync_lock,
 704                             raid10_unplug(conf->mddev->queue));
 705
 706         /* block any new IO from starting */
 707         conf->barrier++;
 708
 709         /* No wait for all pending IO to complete */
 710         wait_event_lock_irq(conf->wait_barrier,
 711                             !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
 712                             conf->resync_lock,
 713                             raid10_unplug(conf->mddev->queue));
 714
 715         spin_unlock_irq(&conf->resync_lock);
 716 }
 717
 718 static void lower_barrier(conf_t *conf)
 719 {
 720         unsigned long flags;
 721         spin_lock_irqsave(&conf->resync_lock, flags);
 722         conf->barrier--;
 723         spin_unlock_irqrestore(&conf->resync_lock, flags);
 724         wake_up(&conf->wait_barrier);
 725 }
 726
 727 static void wait_barrier(conf_t *conf)
 728 {
 729         spin_lock_irq(&conf->resync_lock);
 730         if (conf->barrier) {
 731                 conf->nr_waiting++;
 732                 wait_event_lock_irq(conf->wait_barrier, !conf->barrier,
 733                                     conf->resync_lock,
 734                                     raid10_unplug(conf->mddev->queue));
 735                 conf->nr_waiting--;
 736         }
 737         conf->nr_pending++;
 738         spin_unlock_irq(&conf->resync_lock);
 739 }
 740
 741 static void allow_barrier(conf_t *conf)
 742 {
 743         unsigned long flags;
 744         spin_lock_irqsave(&conf->resync_lock, flags);
 745         conf->nr_pending--;
 746         spin_unlock_irqrestore(&conf->resync_lock, flags);
 747         wake_up(&conf->wait_barrier);
 748 }
 749
 750 static void freeze_array(conf_t *conf)
 751 {
 752         /* stop syncio and normal IO and wait for everything to
 753          * go quiet.
 754          * We increment barrier and nr_waiting, and then
 755          * wait until nr_pending match nr_queued+1
 756          * This is called in the context of one normal IO request
 757          * that has failed. Thus any sync request that might be pending
 758          * will be blocked by nr_pending, and we need to wait for
 759          * pending IO requests to complete or be queued for re-try.
 760          * Thus the number queued (nr_queued) plus this request (1)
 761          * must match the number of pending IOs (nr_pending) before
 762          * we continue.
 763          */
 764         spin_lock_irq(&conf->resync_lock);
 765         conf->barrier++;
 766         conf->nr_waiting++;
 767         wait_event_lock_irq(conf->wait_barrier,
 768                             conf->nr_pending == conf->nr_queued+1,
 769                             conf->resync_lock,
 770                             ({ flush_pending_writes(conf);
 771                                raid10_unplug(conf->mddev->queue); }));
 772         spin_unlock_irq(&conf->resync_lock);
 773 }
 774
 775 static void unfreeze_array(conf_t *conf)
 776 {
 777         /* reverse the effect of the freeze */
 778         spin_lock_irq(&conf->resync_lock);
 779         conf->barrier--;
 780         conf->nr_waiting--;
 781         wake_up(&conf->wait_barrier);
 782         spin_unlock_irq(&conf->resync_lock);
 783 }
 784
 785 static int make_request(struct request_queue *q, struct bio * bio)
 786 {
 787         mddev_t *mddev = q->queuedata;
 788         conf_t *conf = mddev_to_conf(mddev);
 789         mirror_info_t *mirror;
 790         r10bio_t *r10_bio;
 791         struct bio *read_bio;
 792         int i;
 793         int chunk_sects = conf->chunk_mask + 1;
 794         const int rw = bio_data_dir(bio);
 795         const int do_sync = bio_sync(bio);
 796         struct bio_list bl;
 797         unsigned long flags;
 798         mdk_rdev_t *blocked_rdev;
 799
 800         if (unlikely(bio_barrier(bio))) {
 801                 bio_endio(bio, -EOPNOTSUPP);
 802                 return 0;
 803         }
 804
 805         /* If this request crosses a chunk boundary, we need to
 806          * split it.  This will only happen for 1 PAGE (or less) requests.
 807          */
 808         if (unlikely( (bio->bi_sector & conf->chunk_mask) + (bio->bi_size >> 9)
 809                       > chunk_sects &&
 810                     conf->near_copies < conf->raid_disks)) {
 811                 struct bio_pair *bp;
 812                 /* Sanity check -- queue functions should prevent this happening */
 813                 if (bio->bi_vcnt != 1 ||
 814                     bio->bi_idx != 0)
 815                         goto bad_map;
 816                 /* This is a one page bio that upper layers
 817                  * refuse to split for us, so we need to split it.
 818                  */
 819                 bp = bio_split(bio, bio_split_pool,
 820                                chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
 821                 if (make_request(q, &bp->bio1))
 822                         generic_make_request(&bp->bio1);
 823                 if (make_request(q, &bp->bio2))
 824                         generic_make_request(&bp->bio2);
 825
 826                 bio_pair_release(bp);
 827                 return 0;
 828         bad_map:
 829                 printk("raid10_make_request bug: can't convert block across chunks"
 830                        " or bigger than %dk %llu %d\n", chunk_sects/2,
 831                        (unsigned long long)bio->bi_sector, bio->bi_size >> 10);
 832
 833                 bio_io_error(bio);
 834                 return 0;
 835         }
 836
 837         md_write_start(mddev, bio);
 838
 839         /*
 840          * Register the new request and wait if the reconstruction
 841          * thread has put up a bar for new requests.
 842          * Continue immediately if no resync is active currently.
 843          */
 844         wait_barrier(conf);
 845
 846         disk_stat_inc(mddev->gendisk, ios[rw]);
 847         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
 848
 849         r10_bio = mempool_alloc(conf->r10bio_pool, GFP_NOIO);
 850
 851         r10_bio->master_bio = bio;
 852         r10_bio->sectors = bio->bi_size >> 9;
 853
 854         r10_bio->mddev = mddev;
 855         r10_bio->sector = bio->bi_sector;
 856         r10_bio->state = 0;
 857
 858         if (rw == READ) {
 859                 /*
 860                  * read balancing logic:
 861                  */
 862                 int disk = read_balance(conf, r10_bio);
 863                 int slot = r10_bio->read_slot;
 864                 if (disk < 0) {
 865                         raid_end_bio_io(r10_bio);
 866                         return 0;
 867                 }
 868                 mirror = conf->mirrors + disk;
 869
 870                 read_bio = bio_clone(bio, GFP_NOIO);
 871
 872                 r10_bio->devs[slot].bio = read_bio;
 873
 874                 read_bio->bi_sector = r10_bio->devs[slot].addr +
 875                         mirror->rdev->data_offset;
 876                 read_bio->bi_bdev = mirror->rdev->bdev;
 877                 read_bio->bi_end_io = raid10_end_read_request;
 878                 read_bio->bi_rw = READ | do_sync;
 879                 read_bio->bi_private = r10_bio;
 880
 881                 generic_make_request(read_bio);
 882                 return 0;
 883         }
 884
 885         /*
 886          * WRITE:
 887          */
 888         /* first select target devices under rcu_lock and
 889          * inc refcount on their rdev.  Record them by setting
 890          * bios[x] to bio
 891          */
 892         raid10_find_phys(conf, r10_bio);
 893  retry_write:
 894         blocked_rdev = NULL;
 895         rcu_read_lock();
 896         for (i = 0;  i < conf->copies; i++) {
 897                 int d = r10_bio->devs[i].devnum;
 898                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[d].rdev);
 899                 if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
 900                         atomic_inc(&rdev->nr_pending);
 901                         blocked_rdev = rdev;
 902                         break;
 903                 }
 904                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 905                         atomic_inc(&rdev->nr_pending);
 906                         r10_bio->devs[i].bio = bio;
 907                 } else {
 908                         r10_bio->devs[i].bio = NULL;
 909                         set_bit(R10BIO_Degraded, &r10_bio->state);
 910                 }
 911         }
 912         rcu_read_unlock();
 913
 914         if (unlikely(blocked_rdev)) {
 915                 /* Have to wait for this device to get unblocked, then retry */
 916                 int j;
 917                 int d;
 918
 919                 for (j = 0; j < i; j++)
 920                         if (r10_bio->devs[j].bio) {
 921                                 d = r10_bio->devs[j].devnum;
 922                                 rdev_dec_pending(conf->mirrors[d].rdev, mddev);
 923                         }
 924                 allow_barrier(conf);
 925                 md_wait_for_blocked_rdev(blocked_rdev, mddev);
 926                 wait_barrier(conf);
 927                 goto retry_write;
 928         }
 929
 930         atomic_set(&r10_bio->remaining, 0);
 931
 932         bio_list_init(&bl);
 933         for (i = 0; i < conf->copies; i++) {
 934                 struct bio *mbio;
 935                 int d = r10_bio->devs[i].devnum;
 936                 if (!r10_bio->devs[i].bio)
 937                         continue;
 938
 939                 mbio = bio_clone(bio, GFP_NOIO);
 940                 r10_bio->devs[i].bio = mbio;
 941
 942                 mbio->bi_sector = r10_bio->devs[i].addr+
 943                         conf->mirrors[d].rdev->data_offset;
 944                 mbio->bi_bdev = conf->mirrors[d].rdev->bdev;
 945                 mbio->bi_end_io = raid10_end_write_request;
 946                 mbio->bi_rw = WRITE | do_sync;
 947                 mbio->bi_private = r10_bio;
 948
 949                 atomic_inc(&r10_bio->remaining);
 950                 bio_list_add(&bl, mbio);
 951         }
 952
 953         if (unlikely(!atomic_read(&r10_bio->remaining))) {
 954                 /* the array is dead */
 955                 md_write_end(mddev);
 956                 raid_end_bio_io(r10_bio);
 957                 return 0;
 958         }
 959
 960         bitmap_startwrite(mddev->bitmap, bio->bi_sector, r10_bio->sectors, 0);
 961         spin_lock_irqsave(&conf->device_lock, flags);
 962         bio_list_merge(&conf->pending_bio_list, &bl);
 963         blk_plug_device(mddev->queue);
 964         spin_unlock_irqrestore(&conf->device_lock, flags);
 965
 966         /* In case raid10d snuck in to freeze_array */
 967         wake_up(&conf->wait_barrier);
 968
 969         if (do_sync)
 970                 md_wakeup_thread(mddev->thread);
 971
 972         return 0;
 973 }
 974
 975 static void status(struct seq_file *seq, mddev_t *mddev)
 976 {
 977         conf_t *conf = mddev_to_conf(mddev);
 978         int i;
 979
 980         if (conf->near_copies < conf->raid_disks)
 981                 seq_printf(seq, " %dK chunks", mddev->chunk_size/1024);
 982         if (conf->near_copies > 1)
 983                 seq_printf(seq, " %d near-copies", conf->near_copies);
 984         if (conf->far_copies > 1) {
 985                 if (conf->far_offset)
 986                         seq_printf(seq, " %d offset-copies", conf->far_copies);
 987                 else
 988                         seq_printf(seq, " %d far-copies", conf->far_copies);
 989         }
 990         seq_printf(seq, " [%d/%d] [", conf->raid_disks,
 991                                         conf->raid_disks - mddev->degraded);
 992         for (i = 0; i < conf->raid_disks; i++)
 993                 seq_printf(seq, "%s",
 994                               conf->mirrors[i].rdev &&
 995                               test_bit(In_sync, &conf->mirrors[i].rdev->flags) ? "U" : "_");
 996         seq_printf(seq, "]");
 997 }
 998
 999 static void error(mddev_t *mddev, mdk_rdev_t *rdev)
1000 {
1001         char b[BDEVNAME_SIZE];
1002         conf_t *conf = mddev_to_conf(mddev);
1003
1004         /*
1005          * If it is not operational, then we have already marked it as dead
1006          * else if it is the last working disks, ignore the error, let the
1007          * next level up know.
1008          * else mark the drive as failed
1009          */
1010         if (test_bit(In_sync, &rdev->flags)
1011             && conf->raid_disks-mddev->degraded == 1)
1012                 /*
1013                  * Don't fail the drive, just return an IO error.
1014                  * The test should really be more sophisticated than
1015                  * "working_disks == 1", but it isn't critical, and
1016                  * can wait until we do more sophisticated "is the drive
1017                  * really dead" tests...
1018                  */
1019                 return;
1020         if (test_and_clear_bit(In_sync, &rdev->flags)) {
1021                 unsigned long flags;
1022                 spin_lock_irqsave(&conf->device_lock, flags);
1023                 mddev->degraded++;
1024                 spin_unlock_irqrestore(&conf->device_lock, flags);
1025                 /*
1026                  * if recovery is running, make sure it aborts.
1027                  */
1028                 set_bit(MD_RECOVERY_INTR, &mddev->recovery);
1029         }
1030         set_bit(Faulty, &rdev->flags);
1031         set_bit(MD_CHANGE_DEVS, &mddev->flags);
1032         printk(KERN_ALERT "raid10: Disk failure on %s, disabling device.\n"
1033                 "raid10: Operation continuing on %d devices.\n",
1034                 bdevname(rdev->bdev,b), conf->raid_disks - mddev->degraded);
1035 }
1036
1037 static void print_conf(conf_t *conf)
1038 {
1039         int i;
1040         mirror_info_t *tmp;
1041
1042         printk("RAID10 conf printout:\n");
1043         if (!conf) {
1044                 printk("(!conf)\n");
1045                 return;
1046         }
1047         printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
1048                 conf->raid_disks);
1049
1050         for (i = 0; i < conf->raid_disks; i++) {
1051                 char b[BDEVNAME_SIZE];
1052                 tmp = conf->mirrors + i;
1053                 if (tmp->rdev)
1054                         printk(" disk %d, wo:%d, o:%d, dev:%s\n",
1055                                 i, !test_bit(In_sync, &tmp->rdev->flags),
1056                                 !test_bit(Faulty, &tmp->rdev->flags),
1057                                 bdevname(tmp->rdev->bdev,b));
1058         }
1059 }
1060
1061 static void close_sync(conf_t *conf)
1062 {
1063         wait_barrier(conf);
1064         allow_barrier(conf);
1065
1066         mempool_destroy(conf->r10buf_pool);
1067         conf->r10buf_pool = NULL;
1068 }
1069
1070 /* check if there are enough drives for
1071  * every block to appear on atleast one
1072  */
1073 static int enough(conf_t *conf)
1074 {
1075         int first = 0;
1076
1077         do {
1078                 int n = conf->copies;
1079                 int cnt = 0;
1080                 while (n--) {
1081                         if (conf->mirrors[first].rdev)
1082                                 cnt++;
1083                         first = (first+1) % conf->raid_disks;
1084                 }
1085                 if (cnt == 0)
1086                         return 0;
1087         } while (first != 0);
1088         return 1;
1089 }
1090
1091 static int raid10_spare_active(mddev_t *mddev)
1092 {
1093         int i;
1094         conf_t *conf = mddev->private;
1095         mirror_info_t *tmp;
1096
1097         /*
1098          * Find all non-in_sync disks within the RAID10 configuration
1099          * and mark them in_sync
1100          */
1101         for (i = 0; i < conf->raid_disks; i++) {
1102                 tmp = conf->mirrors + i;
1103                 if (tmp->rdev
1104                     && !test_bit(Faulty, &tmp->rdev->flags)
1105                     && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
1106                         unsigned long flags;
1107                         spin_lock_irqsave(&conf->device_lock, flags);
1108                         mddev->degraded--;
1109                         spin_unlock_irqrestore(&conf->device_lock, flags);
1110                 }
1111         }
1112
1113         print_conf(conf);
1114         return 0;
1115 }
1116
1117
1118 static int raid10_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
1119 {
1120         conf_t *conf = mddev->private;
1121         int err = -EEXIST;
1122         int mirror;
1123         mirror_info_t *p;
1124         int first = 0;
1125         int last = mddev->raid_disks - 1;
1126
1127         if (mddev->recovery_cp < MaxSector)
1128                 /* only hot-add to in-sync arrays, as recovery is
1129                  * very different from resync
1130                  */
1131                 return -EBUSY;
1132         if (!enough(conf))
1133                 return -EINVAL;
1134
1135         if (rdev->raid_disk)
1136                 first = last = rdev->raid_disk;
1137
1138         if (rdev->saved_raid_disk >= 0 &&
1139             rdev->saved_raid_disk >= first &&
1140             conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
1141                 mirror = rdev->saved_raid_disk;
1142         else
1143                 mirror = first;
1144         for ( ; mirror <= last ; mirror++)
1145                 if ( !(p=conf->mirrors+mirror)->rdev) {
1146
1147                         blk_queue_stack_limits(mddev->queue,
1148                                                rdev->bdev->bd_disk->queue);
1149                         /* as we don't honour merge_bvec_fn, we must never risk
1150                          * violating it, so limit ->max_sector to one PAGE, as
1151                          * a one page request is never in violation.
1152                          */
1153                         if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
1154                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
1155                                 mddev->queue->max_sectors = (PAGE_SIZE>>9);
1156
1157                         p->head_position = 0;
1158                         rdev->raid_disk = mirror;
1159                         err = 0;
1160                         if (rdev->saved_raid_disk != mirror)
1161                                 conf->fullsync = 1;
1162                         rcu_assign_pointer(p->rdev, rdev);
1163                         break;
1164                 }
1165
1166         print_conf(conf);
1167         return err;
1168 }
1169
1170 static int raid10_remove_disk(mddev_t *mddev, int number)
1171 {
1172         conf_t *conf = mddev->private;
1173         int err = 0;
1174         mdk_rdev_t *rdev;
1175         mirror_info_t *p = conf->mirrors+ number;
1176
1177         print_conf(conf);
1178         rdev = p->rdev;
1179         if (rdev) {
1180                 if (test_bit(In_sync, &rdev->flags) ||
1181                     atomic_read(&rdev->nr_pending)) {
1182                         err = -EBUSY;
1183                         goto abort;
1184                 }
1185                 /* Only remove faulty devices in recovery
1186                  * is not possible.
1187                  */
1188                 if (!test_bit(Faulty, &rdev->flags) &&
1189                     enough(conf)) {
1190                         err = -EBUSY;
1191                         goto abort;
1192                 }
1193                 p->rdev = NULL;
1194                 synchronize_rcu();
1195                 if (atomic_read(&rdev->nr_pending)) {
1196                         /* lost the race, try later */
1197                         err = -EBUSY;
1198                         p->rdev = rdev;
1199                 }
1200         }
1201 abort:
1202
1203         print_conf(conf);
1204         return err;
1205 }
1206
1207
1208 static void end_sync_read(struct bio *bio, int error)
1209 {
1210         r10bio_t * r10_bio = (r10bio_t *)(bio->bi_private);
1211         conf_t *conf = mddev_to_conf(r10_bio->mddev);
1212         int i,d;
1213
1214         for (i=0; i<conf->copies; i++)
1215                 if (r10_bio->devs[i].bio == bio)
1216                         break;
1217         BUG_ON(i == conf->copies);
1218         update_head_pos(i, r10_bio);
1219         d = r10_bio->devs[i].devnum;
1220
1221         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
1222                 set_bit(R10BIO_Uptodate, &r10_bio->state);
1223         else {
1224                 atomic_add(r10_bio->sectors,
1225                            &conf->mirrors[d].rdev->corrected_errors);
1226                 if (!test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery))
1227                         md_error(r10_bio->mddev,
1228                                  conf->mirrors[d].rdev);
1229         }
1230
1231         /* for reconstruct, we always reschedule after a read.
1232          * for resync, only after all reads
1233          */
1234         if (test_bit(R10BIO_IsRecover, &r10_bio->state) ||
1235             atomic_dec_and_test(&r10_bio->remaining)) {
1236                 /* we have read all the blocks,
1237                  * do the comparison in process context in raid10d
1238                  */
1239                 reschedule_retry(r10_bio);
1240         }
1241         rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);
1242 }
1243
1244 static void end_sync_write(struct bio *bio, int error)
1245 {
1246         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
1247         r10bio_t * r10_bio = (r10bio_t *)(bio->bi_private);
1248         mddev_t *mddev = r10_bio->mddev;
1249         conf_t *conf = mddev_to_conf(mddev);
1250         int i,d;
1251
1252         for (i = 0; i < conf->copies; i++)
1253                 if (r10_bio->devs[i].bio == bio)
1254                         break;
1255         d = r10_bio->devs[i].devnum;
1256
1257         if (!uptodate)
1258                 md_error(mddev, conf->mirrors[d].rdev);
1259
1260         update_head_pos(i, r10_bio);
1261
1262         while (atomic_dec_and_test(&r10_bio->remaining)) {
1263                 if (r10_bio->master_bio == NULL) {
1264                         /* the primary of several recovery bios */
1265                         md_done_sync(mddev, r10_bio->sectors, 1);
1266                         put_buf(r10_bio);
1267                         break;
1268                 } else {
1269                         r10bio_t *r10_bio2 = (r10bio_t *)r10_bio->master_bio;
1270                         put_buf(r10_bio);
1271                         r10_bio = r10_bio2;
1272                 }
1273         }
1274         rdev_dec_pending(conf->mirrors[d].rdev, mddev);
1275 }
1276
1277 /*
1278  * Note: sync and recover and handled very differently for raid10
1279  * This code is for resync.
1280  * For resync, we read through virtual addresses and read all blocks.
1281  * If there is any error, we schedule a write.  The lowest numbered
1282  * drive is authoritative.
1283  * However requests come for physical address, so we need to map.
1284  * For every physical address there are raid_disks/copies virtual addresses,
1285  * which is always are least one, but is not necessarly an integer.
1286  * This means that a physical address can span multiple chunks, so we may
1287  * have to submit multiple io requests for a single sync request.
1288  */
1289 /*
1290  * We check if all blocks are in-sync and only write to blocks that
1291  * aren't in sync
1292  */
1293 static void sync_request_write(mddev_t *mddev, r10bio_t *r10_bio)
1294 {
1295         conf_t *conf = mddev_to_conf(mddev);
1296         int i, first;
1297         struct bio *tbio, *fbio;
1298
1299         atomic_set(&r10_bio->remaining, 1);
1300
1301         /* find the first device with a block */
1302         for (i=0; i<conf->copies; i++)
1303                 if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags))
1304                         break;
1305
1306         if (i == conf->copies)
1307                 goto done;
1308
1309         first = i;
1310         fbio = r10_bio->devs[i].bio;
1311
1312         /* now find blocks with errors */
1313         for (i=0 ; i < conf->copies ; i++) {
1314                 int  j, d;
1315                 int vcnt = r10_bio->sectors >> (PAGE_SHIFT-9);
1316
1317                 tbio = r10_bio->devs[i].bio;
1318
1319                 if (tbio->bi_end_io != end_sync_read)
1320                         continue;
1321                 if (i == first)
1322                         continue;
1323                 if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags)) {
1324                         /* We know that the bi_io_vec layout is the same for
1325                          * both 'first' and 'i', so we just compare them.
1326                          * All vec entries are PAGE_SIZE;
1327                          */
1328                         for (j = 0; j < vcnt; j++)
1329                                 if (memcmp(page_address(fbio->bi_io_vec[j].bv_page),
1330                                            page_address(tbio->bi_io_vec[j].bv_page),
1331                                            PAGE_SIZE))
1332                                         break;
1333                         if (j == vcnt)
1334                                 continue;
1335                         mddev->resync_mismatches += r10_bio->sectors;
1336                 }
1337                 if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
1338                         /* Don't fix anything. */
1339                         continue;
1340                 /* Ok, we need to write this bio
1341                  * First we need to fixup bv_offset, bv_len and
1342                  * bi_vecs, as the read request might have corrupted these
1343                  */
1344                 tbio->bi_vcnt = vcnt;
1345                 tbio->bi_size = r10_bio->sectors << 9;
1346                 tbio->bi_idx = 0;
1347                 tbio->bi_phys_segments = 0;
1348                 tbio->bi_flags &= ~(BIO_POOL_MASK - 1);
1349                 tbio->bi_flags |= 1 << BIO_UPTODATE;
1350                 tbio->bi_next = NULL;
1351                 tbio->bi_rw = WRITE;
1352                 tbio->bi_private = r10_bio;
1353                 tbio->bi_sector = r10_bio->devs[i].addr;
1354
1355                 for (j=0; j < vcnt ; j++) {
1356                         tbio->bi_io_vec[j].bv_offset = 0;
1357                         tbio->bi_io_vec[j].bv_len = PAGE_SIZE;
1358
1359                         memcpy(page_address(tbio->bi_io_vec[j].bv_page),
1360                                page_address(fbio->bi_io_vec[j].bv_page),
1361                                PAGE_SIZE);
1362                 }
1363                 tbio->bi_end_io = end_sync_write;
1364
1365                 d = r10_bio->devs[i].devnum;
1366                 atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1367                 atomic_inc(&r10_bio->remaining);
1368                 md_sync_acct(conf->mirrors[d].rdev->bdev, tbio->bi_size >> 9);
1369
1370                 tbio->bi_sector += conf->mirrors[d].rdev->data_offset;
1371                 tbio->bi_bdev = conf->mirrors[d].rdev->bdev;
1372                 generic_make_request(tbio);
1373         }
1374
1375 done:
1376         if (atomic_dec_and_test(&r10_bio->remaining)) {
1377                 md_done_sync(mddev, r10_bio->sectors, 1);
1378                 put_buf(r10_bio);
1379         }
1380 }
1381
1382 /*
1383  * Now for the recovery code.
1384  * Recovery happens across physical sectors.
1385  * We recover all non-is_sync drives by finding the virtual address of
1386  * each, and then choose a working drive that also has that virt address.
1387  * There is a separate r10_bio for each non-in_sync drive.
1388  * Only the first two slots are in use. The first for reading,
1389  * The second for writing.
1390  *
1391  */
1392
1393 static void recovery_request_write(mddev_t *mddev, r10bio_t *r10_bio)
1394 {
1395         conf_t *conf = mddev_to_conf(mddev);
1396         int i, d;
1397         struct bio *bio, *wbio;
1398
1399
1400         /* move the pages across to the second bio
1401          * and submit the write request
1402          */
1403         bio = r10_bio->devs[0].bio;
1404         wbio = r10_bio->devs[1].bio;
1405         for (i=0; i < wbio->bi_vcnt; i++) {
1406                 struct page *p = bio->bi_io_vec[i].bv_page;
1407                 bio->bi_io_vec[i].bv_page = wbio->bi_io_vec[i].bv_page;
1408                 wbio->bi_io_vec[i].bv_page = p;
1409         }
1410         d = r10_bio->devs[1].devnum;
1411
1412         atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1413         md_sync_acct(conf->mirrors[d].rdev->bdev, wbio->bi_size >> 9);
1414         if (test_bit(R10BIO_Uptodate, &r10_bio->state))
1415                 generic_make_request(wbio);
1416         else
1417                 bio_endio(wbio, -EIO);
1418 }
1419
1420
1421 /*
1422  * This is a kernel thread which:
1423  *
1424  *      1.      Retries failed read operations on working mirrors.
1425  *      2.      Updates the raid superblock when problems encounter.
1426  *      3.      Performs writes following reads for array synchronising.
1427  */
1428
1429 static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
1430 {
1431         int sect = 0; /* Offset from r10_bio->sector */
1432         int sectors = r10_bio->sectors;
1433         mdk_rdev_t*rdev;
1434         while(sectors) {
1435                 int s = sectors;
1436                 int sl = r10_bio->read_slot;
1437                 int success = 0;
1438                 int start;
1439
1440                 if (s > (PAGE_SIZE>>9))
1441                         s = PAGE_SIZE >> 9;
1442
1443                 rcu_read_lock();
1444                 do {
1445                         int d = r10_bio->devs[sl].devnum;
1446                         rdev = rcu_dereference(conf->mirrors[d].rdev);
1447                         if (rdev &&
1448                             test_bit(In_sync, &rdev->flags)) {
1449                                 atomic_inc(&rdev->nr_pending);
1450                                 rcu_read_unlock();
1451                                 success = sync_page_io(rdev->bdev,
1452                                                        r10_bio->devs[sl].addr +
1453                                                        sect + rdev->data_offset,
1454                                                        s<<9,
1455                                                        conf->tmppage, READ);
1456                                 rdev_dec_pending(rdev, mddev);
1457                                 rcu_read_lock();
1458                                 if (success)
1459                                         break;
1460                         }
1461                         sl++;
1462                         if (sl == conf->copies)
1463                                 sl = 0;
1464                 } while (!success && sl != r10_bio->read_slot);
1465                 rcu_read_unlock();
1466
1467                 if (!success) {
1468                         /* Cannot read from anywhere -- bye bye array */
1469                         int dn = r10_bio->devs[r10_bio->read_slot].devnum;
1470                         md_error(mddev, conf->mirrors[dn].rdev);
1471                         break;
1472                 }
1473
1474                 start = sl;
1475                 /* write it back and re-read */
1476                 rcu_read_lock();
1477                 while (sl != r10_bio->read_slot) {
1478                         int d;
1479                         if (sl==0)
1480                                 sl = conf->copies;
1481                         sl--;
1482                         d = r10_bio->devs[sl].devnum;
1483                         rdev = rcu_dereference(conf->mirrors[d].rdev);
1484                         if (rdev &&
1485                             test_bit(In_sync, &rdev->flags)) {
1486                                 atomic_inc(&rdev->nr_pending);
1487                                 rcu_read_unlock();
1488                                 atomic_add(s, &rdev->corrected_errors);
1489                                 if (sync_page_io(rdev->bdev,
1490                                                  r10_bio->devs[sl].addr +
1491                                                  sect + rdev->data_offset,
1492                                                  s<<9, conf->tmppage, WRITE)
1493                                     == 0)
1494                                         /* Well, this device is dead */
1495                                         md_error(mddev, rdev);
1496                                 rdev_dec_pending(rdev, mddev);
1497                                 rcu_read_lock();
1498                         }
1499                 }
1500                 sl = start;
1501                 while (sl != r10_bio->read_slot) {
1502                         int d;
1503                         if (sl==0)
1504                                 sl = conf->copies;
1505                         sl--;
1506                         d = r10_bio->devs[sl].devnum;
1507                         rdev = rcu_dereference(conf->mirrors[d].rdev);
1508                         if (rdev &&
1509                             test_bit(In_sync, &rdev->flags)) {
1510                                 char b[BDEVNAME_SIZE];
1511                                 atomic_inc(&rdev->nr_pending);
1512                                 rcu_read_unlock();
1513                                 if (sync_page_io(rdev->bdev,
1514                                                  r10_bio->devs[sl].addr +
1515                                                  sect + rdev->data_offset,
1516                                                  s<<9, conf->tmppage, READ) == 0)
1517                                         /* Well, this device is dead */
1518                                         md_error(mddev, rdev);
1519                                 else
1520                                         printk(KERN_INFO
1521                                                "raid10:%s: read error corrected"
1522                                                " (%d sectors at %llu on %s)\n",
1523                                                mdname(mddev), s,
1524                                                (unsigned long long)(sect+
1525                                                     rdev->data_offset),
1526                                                bdevname(rdev->bdev, b));
1527
1528                                 rdev_dec_pending(rdev, mddev);
1529                                 rcu_read_lock();
1530                         }
1531                 }
1532                 rcu_read_unlock();
1533
1534                 sectors -= s;
1535                 sect += s;
1536         }
1537 }
1538
1539 static void raid10d(mddev_t *mddev)
1540 {
1541         r10bio_t *r10_bio;
1542         struct bio *bio;
1543         unsigned long flags;
1544         conf_t *conf = mddev_to_conf(mddev);
1545         struct list_head *head = &conf->retry_list;
1546         int unplug=0;
1547         mdk_rdev_t *rdev;
1548
1549         md_check_recovery(mddev);
1550
1551         for (;;) {
1552                 char b[BDEVNAME_SIZE];
1553
1554                 unplug += flush_pending_writes(conf);
1555
1556                 spin_lock_irqsave(&conf->device_lock, flags);
1557                 if (list_empty(head)) {
1558                         spin_unlock_irqrestore(&conf->device_lock, flags);
1559                         break;
1560                 }
1561                 r10_bio = list_entry(head->prev, r10bio_t, retry_list);
1562                 list_del(head->prev);
1563                 conf->nr_queued--;
1564                 spin_unlock_irqrestore(&conf->device_lock, flags);
1565
1566                 mddev = r10_bio->mddev;
1567                 conf = mddev_to_conf(mddev);
1568                 if (test_bit(R10BIO_IsSync, &r10_bio->state)) {
1569                         sync_request_write(mddev, r10_bio);
1570                         unplug = 1;
1571                 } else  if (test_bit(R10BIO_IsRecover, &r10_bio->state)) {
1572                         recovery_request_write(mddev, r10_bio);
1573                         unplug = 1;
1574                 } else {
1575                         int mirror;
1576                         /* we got a read error. Maybe the drive is bad.  Maybe just
1577                          * the block and we can fix it.
1578                          * We freeze all other IO, and try reading the block from
1579                          * other devices.  When we find one, we re-write
1580                          * and check it that fixes the read error.
1581                          * This is all done synchronously while the array is
1582                          * frozen.
1583                          */
1584                         if (mddev->ro == 0) {
1585                                 freeze_array(conf);
1586                                 fix_read_error(conf, mddev, r10_bio);
1587                                 unfreeze_array(conf);
1588                         }
1589
1590                         bio = r10_bio->devs[r10_bio->read_slot].bio;
1591                         r10_bio->devs[r10_bio->read_slot].bio =
1592                                 mddev->ro ? IO_BLOCKED : NULL;
1593                         mirror = read_balance(conf, r10_bio);
1594                         if (mirror == -1) {
1595                                 printk(KERN_ALERT "raid10: %s: unrecoverable I/O"
1596                                        " read error for block %llu\n",
1597                                        bdevname(bio->bi_bdev,b),
1598                                        (unsigned long long)r10_bio->sector);
1599                                 raid_end_bio_io(r10_bio);
1600                                 bio_put(bio);
1601                         } else {
1602                                 const int do_sync = bio_sync(r10_bio->master_bio);
1603                                 bio_put(bio);
1604                                 rdev = conf->mirrors[mirror].rdev;
1605                                 if (printk_ratelimit())
1606                                         printk(KERN_ERR "raid10: %s: redirecting sector %llu to"
1607                                                " another mirror\n",
1608                                                bdevname(rdev->bdev,b),
1609                                                (unsigned long long)r10_bio->sector);
1610                                 bio = bio_clone(r10_bio->master_bio, GFP_NOIO);
1611                                 r10_bio->devs[r10_bio->read_slot].bio = bio;
1612                                 bio->bi_sector = r10_bio->devs[r10_bio->read_slot].addr
1613                                         + rdev->data_offset;
1614                                 bio->bi_bdev = rdev->bdev;
1615                                 bio->bi_rw = READ | do_sync;
1616                                 bio->bi_private = r10_bio;
1617                                 bio->bi_end_io = raid10_end_read_request;
1618                                 unplug = 1;
1619                                 generic_make_request(bio);
1620                         }
1621                 }
1622         }
1623         if (unplug)
1624                 unplug_slaves(mddev);
1625 }
1626
1627
1628 static int init_resync(conf_t *conf)
1629 {
1630         int buffs;
1631
1632         buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
1633         BUG_ON(conf->r10buf_pool);
1634         conf->r10buf_pool = mempool_create(buffs, r10buf_pool_alloc, r10buf_pool_free, conf);
1635         if (!conf->r10buf_pool)
1636                 return -ENOMEM;
1637         conf->next_resync = 0;
1638         return 0;
1639 }
1640
1641 /*
1642  * perform a "sync" on one "block"
1643  *
1644  * We need to make sure that no normal I/O request - particularly write
1645  * requests - conflict with active sync requests.
1646  *
1647  * This is achieved by tracking pending requests and a 'barrier' concept
1648  * that can be installed to exclude normal IO requests.
1649  *
1650  * Resync and recovery are handled very differently.
1651  * We differentiate by looking at MD_RECOVERY_SYNC in mddev->recovery.
1652  *
1653  * For resync, we iterate over virtual addresses, read all copies,
1654  * and update if there are differences.  If only one copy is live,
1655  * skip it.
1656  * For recovery, we iterate over physical addresses, read a good
1657  * value for each non-in_sync drive, and over-write.
1658  *
1659  * So, for recovery we may have several outstanding complex requests for a
1660  * given address, one for each out-of-sync device.  We model this by allocating
1661  * a number of r10_bio structures, one for each out-of-sync device.
1662  * As we setup these structures, we collect all bio's together into a list
1663  * which we then process collectively to add pages, and then process again
1664  * to pass to generic_make_request.
1665  *
1666  * The r10_bio structures are linked using a borrowed master_bio pointer.
1667  * This link is counted in ->remaining.  When the r10_bio that points to NULL
1668  * has its remaining count decremented to 0, the whole complex operation
1669  * is complete.
1670  *
1671  */
1672
1673 static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
1674 {
1675         conf_t *conf = mddev_to_conf(mddev);
1676         r10bio_t *r10_bio;
1677         struct bio *biolist = NULL, *bio;
1678         sector_t max_sector, nr_sectors;
1679         int disk;
1680         int i;
1681         int max_sync;
1682         int sync_blocks;
1683
1684         sector_t sectors_skipped = 0;
1685         int chunks_skipped = 0;
1686
1687         if (!conf->r10buf_pool)
1688                 if (init_resync(conf))
1689                         return 0;
1690
1691  skipped:
1692         max_sector = mddev->size << 1;
1693         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
1694                 max_sector = mddev->resync_max_sectors;
1695         if (sector_nr >= max_sector) {
1696                 /* If we aborted, we need to abort the
1697                  * sync on the 'current' bitmap chucks (there can
1698                  * be several when recovering multiple devices).
1699                  * as we may have started syncing it but not finished.
1700                  * We can find the current address in
1701                  * mddev->curr_resync, but for recovery,
1702                  * we need to convert that to several
1703                  * virtual addresses.
1704                  */
1705                 if (mddev->curr_resync < max_sector) { /* aborted */
1706                         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
1707                                 bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
1708                                                 &sync_blocks, 1);
1709                         else for (i=0; i<conf->raid_disks; i++) {
1710                                 sector_t sect =
1711                                         raid10_find_virt(conf, mddev->curr_resync, i);
1712                                 bitmap_end_sync(mddev->bitmap, sect,
1713                                                 &sync_blocks, 1);
1714                         }
1715                 } else /* completed sync */
1716                         conf->fullsync = 0;
1717
1718                 bitmap_close_sync(mddev->bitmap);
1719                 close_sync(conf);
1720                 *skipped = 1;
1721                 return sectors_skipped;
1722         }
1723         if (chunks_skipped >= conf->raid_disks) {
1724                 /* if there has been nothing to do on any drive,
1725                  * then there is nothing to do at all..
1726                  */
1727                 *skipped = 1;
1728                 return (max_sector - sector_nr) + sectors_skipped;
1729         }
1730
1731         if (max_sector > mddev->resync_max)
1732                 max_sector = mddev->resync_max; /* Don't do IO beyond here */
1733
1734         /* make sure whole request will fit in a chunk - if chunks
1735          * are meaningful
1736          */
1737         if (conf->near_copies < conf->raid_disks &&
1738             max_sector > (sector_nr | conf->chunk_mask))
1739                 max_sector = (sector_nr | conf->chunk_mask) + 1;
1740         /*
1741          * If there is non-resync activity waiting for us then
1742          * put in a delay to throttle resync.
1743          */
1744         if (!go_faster && conf->nr_waiting)
1745                 msleep_interruptible(1000);
1746
1747         bitmap_cond_end_sync(mddev->bitmap, sector_nr);
1748
1749         /* Again, very different code for resync and recovery.
1750          * Both must result in an r10bio with a list of bios that
1751          * have bi_end_io, bi_sector, bi_bdev set,
1752          * and bi_private set to the r10bio.
1753          * For recovery, we may actually create several r10bios
1754          * with 2 bios in each, that correspond to the bios in the main one.
1755          * In this case, the subordinate r10bios link back through a
1756          * borrowed master_bio pointer, and the counter in the master
1757          * includes a ref from each subordinate.
1758          */
1759         /* First, we decide what to do and set ->bi_end_io
1760          * To end_sync_read if we want to read, and
1761          * end_sync_write if we will want to write.
1762          */
1763
1764         max_sync = RESYNC_PAGES << (PAGE_SHIFT-9);
1765         if (!test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
1766                 /* recovery... the complicated one */
1767                 int i, j, k;
1768                 r10_bio = NULL;
1769
1770                 for (i=0 ; i<conf->raid_disks; i++)
1771                         if (conf->mirrors[i].rdev &&
1772                             !test_bit(In_sync, &conf->mirrors[i].rdev->flags)) {
1773                                 int still_degraded = 0;
1774                                 /* want to reconstruct this device */
1775                                 r10bio_t *rb2 = r10_bio;
1776                                 sector_t sect = raid10_find_virt(conf, sector_nr, i);
1777                                 int must_sync;
1778                                 /* Unless we are doing a full sync, we only need
1779                                  * to recover the block if it is set in the bitmap
1780                                  */
1781                                 must_sync = bitmap_start_sync(mddev->bitmap, sect,
1782                                                               &sync_blocks, 1);
1783                                 if (sync_blocks < max_sync)
1784                                         max_sync = sync_blocks;
1785                                 if (!must_sync &&
1786                                     !conf->fullsync) {
1787                                         /* yep, skip the sync_blocks here, but don't assume
1788                                          * that there will never be anything to do here
1789                                          */
1790                                         chunks_skipped = -1;
1791                                         continue;
1792                                 }
1793
1794                                 r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
1795                                 raise_barrier(conf, rb2 != NULL);
1796                                 atomic_set(&r10_bio->remaining, 0);
1797
1798                                 r10_bio->master_bio = (struct bio*)rb2;
1799                                 if (rb2)
1800                                         atomic_inc(&rb2->remaining);
1801                                 r10_bio->mddev = mddev;
1802                                 set_bit(R10BIO_IsRecover, &r10_bio->state);
1803                                 r10_bio->sector = sect;
1804
1805                                 raid10_find_phys(conf, r10_bio);
1806                                 /* Need to check if this section will still be
1807                                  * degraded
1808                                  */
1809                                 for (j=0; j<conf->copies;j++) {
1810                                         int d = r10_bio->devs[j].devnum;
1811                                         if (conf->mirrors[d].rdev == NULL ||
1812                                             test_bit(Faulty, &conf->mirrors[d].rdev->flags)) {
1813                                                 still_degraded = 1;
1814                                                 break;
1815                                         }
1816                                 }
1817                                 must_sync = bitmap_start_sync(mddev->bitmap, sect,
1818                                                               &sync_blocks, still_degraded);
1819
1820                                 for (j=0; j<conf->copies;j++) {
1821                                         int d = r10_bio->devs[j].devnum;
1822                                         if (conf->mirrors[d].rdev &&
1823                                             test_bit(In_sync, &conf->mirrors[d].rdev->flags)) {
1824                                                 /* This is where we read from */
1825                                                 bio = r10_bio->devs[0].bio;
1826                                                 bio->bi_next = biolist;
1827                                                 biolist = bio;
1828                                                 bio->bi_private = r10_bio;
1829                                                 bio->bi_end_io = end_sync_read;
1830                                                 bio->bi_rw = READ;
1831                                                 bio->bi_sector = r10_bio->devs[j].addr +
1832                                                         conf->mirrors[d].rdev->data_offset;
1833                                                 bio->bi_bdev = conf->mirrors[d].rdev->bdev;
1834                                                 atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1835                                                 atomic_inc(&r10_bio->remaining);
1836                                                 /* and we write to 'i' */
1837
1838                                                 for (k=0; k<conf->copies; k++)
1839                                                         if (r10_bio->devs[k].devnum == i)
1840                                                                 break;
1841                                                 BUG_ON(k == conf->copies);
1842                                                 bio = r10_bio->devs[1].bio;
1843                                                 bio->bi_next = biolist;
1844                                                 biolist = bio;
1845                                                 bio->bi_private = r10_bio;
1846                                                 bio->bi_end_io = end_sync_write;
1847                                                 bio->bi_rw = WRITE;
1848                                                 bio->bi_sector = r10_bio->devs[k].addr +
1849                                                         conf->mirrors[i].rdev->data_offset;
1850                                                 bio->bi_bdev = conf->mirrors[i].rdev->bdev;
1851
1852                                                 r10_bio->devs[0].devnum = d;
1853                                                 r10_bio->devs[1].devnum = i;
1854
1855                                                 break;
1856                                         }
1857                                 }
1858                                 if (j == conf->copies) {
1859                                         /* Cannot recover, so abort the recovery */
1860                                         put_buf(r10_bio);
1861                                         if (rb2)
1862                                                 atomic_dec(&rb2->remaining);
1863                                         r10_bio = rb2;
1864                                         if (!test_and_set_bit(MD_RECOVERY_INTR,
1865                                                               &mddev->recovery))
1866                                                 printk(KERN_INFO "raid10: %s: insufficient working devices for recovery.\n",
1867                                                        mdname(mddev));
1868                                         break;
1869                                 }
1870                         }
1871                 if (biolist == NULL) {
1872                         while (r10_bio) {
1873                                 r10bio_t *rb2 = r10_bio;
1874                                 r10_bio = (r10bio_t*) rb2->master_bio;
1875                                 rb2->master_bio = NULL;
1876                                 put_buf(rb2);
1877                         }
1878                         goto giveup;
1879                 }
1880         } else {
1881                 /* resync. Schedule a read for every block at this virt offset */
1882                 int count = 0;
1883
1884                 if (!bitmap_start_sync(mddev->bitmap, sector_nr,
1885                                        &sync_blocks, mddev->degraded) &&
1886                     !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
1887                         /* We can skip this block */
1888                         *skipped = 1;
1889                         return sync_blocks + sectors_skipped;
1890                 }
1891                 if (sync_blocks < max_sync)
1892                         max_sync = sync_blocks;
1893                 r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
1894
1895                 r10_bio->mddev = mddev;
1896                 atomic_set(&r10_bio->remaining, 0);
1897                 raise_barrier(conf, 0);
1898                 conf->next_resync = sector_nr;
1899
1900                 r10_bio->master_bio = NULL;
1901                 r10_bio->sector = sector_nr;
1902                 set_bit(R10BIO_IsSync, &r10_bio->state);
1903                 raid10_find_phys(conf, r10_bio);
1904                 r10_bio->sectors = (sector_nr | conf->chunk_mask) - sector_nr +1;
1905
1906                 for (i=0; i<conf->copies; i++) {
1907                         int d = r10_bio->devs[i].devnum;
1908                         bio = r10_bio->devs[i].bio;
1909                         bio->bi_end_io = NULL;
1910                         clear_bit(BIO_UPTODATE, &bio->bi_flags);
1911                         if (conf->mirrors[d].rdev == NULL ||
1912                             test_bit(Faulty, &conf->mirrors[d].rdev->flags))
1913                                 continue;
1914                         atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1915                         atomic_inc(&r10_bio->remaining);
1916                         bio->bi_next = biolist;
1917                         biolist = bio;
1918                         bio->bi_private = r10_bio;
1919                         bio->bi_end_io = end_sync_read;
1920                         bio->bi_rw = READ;
1921                         bio->bi_sector = r10_bio->devs[i].addr +
1922                                 conf->mirrors[d].rdev->data_offset;
1923                         bio->bi_bdev = conf->mirrors[d].rdev->bdev;
1924                         count++;
1925                 }
1926
1927                 if (count < 2) {
1928                         for (i=0; i<conf->copies; i++) {
1929                                 int d = r10_bio->devs[i].devnum;
1930                                 if (r10_bio->devs[i].bio->bi_end_io)
1931                                         rdev_dec_pending(conf->mirrors[d].rdev, mddev);
1932                         }
1933                         put_buf(r10_bio);
1934                         biolist = NULL;
1935                         goto giveup;
1936                 }
1937         }
1938
1939         for (bio = biolist; bio ; bio=bio->bi_next) {
1940
1941                 bio->bi_flags &= ~(BIO_POOL_MASK - 1);
1942                 if (bio->bi_end_io)
1943                         bio->bi_flags |= 1 << BIO_UPTODATE;
1944                 bio->bi_vcnt = 0;
1945                 bio->bi_idx = 0;
1946                 bio->bi_phys_segments = 0;
1947                 bio->bi_hw_segments = 0;
1948                 bio->bi_size = 0;
1949         }
1950
1951         nr_sectors = 0;
1952         if (sector_nr + max_sync < max_sector)
1953                 max_sector = sector_nr + max_sync;
1954         do {
1955                 struct page *page;
1956                 int len = PAGE_SIZE;
1957                 disk = 0;
1958                 if (sector_nr + (len>>9) > max_sector)
1959                         len = (max_sector - sector_nr) << 9;
1960                 if (len == 0)
1961                         break;
1962                 for (bio= biolist ; bio ; bio=bio->bi_next) {
1963                         page = bio->bi_io_vec[bio->bi_vcnt].bv_page;
1964                         if (bio_add_page(bio, page, len, 0) == 0) {
1965                                 /* stop here */
1966                                 struct bio *bio2;
1967                                 bio->bi_io_vec[bio->bi_vcnt].bv_page = page;
1968                                 for (bio2 = biolist; bio2 && bio2 != bio; bio2 = bio2->bi_next) {
1969                                         /* remove last page from this bio */
1970                                         bio2->bi_vcnt--;
1971                                         bio2->bi_size -= len;
1972                                         bio2->bi_flags &= ~(1<< BIO_SEG_VALID);
1973                                 }
1974                                 goto bio_full;
1975                         }
1976                         disk = i;
1977                 }
1978                 nr_sectors += len>>9;
1979                 sector_nr += len>>9;
1980         } while (biolist->bi_vcnt < RESYNC_PAGES);
1981  bio_full:
1982         r10_bio->sectors = nr_sectors;
1983
1984         while (biolist) {
1985                 bio = biolist;
1986                 biolist = biolist->bi_next;
1987
1988                 bio->bi_next = NULL;
1989                 r10_bio = bio->bi_private;
1990                 r10_bio->sectors = nr_sectors;
1991
1992                 if (bio->bi_end_io == end_sync_read) {
1993                         md_sync_acct(bio->bi_bdev, nr_sectors);
1994                         generic_make_request(bio);
1995                 }
1996         }
1997
1998         if (sectors_skipped)
1999                 /* pretend they weren't skipped, it makes
2000                  * no important difference in this case
2001                  */
2002                 md_done_sync(mddev, sectors_skipped, 1);
2003
2004         return sectors_skipped + nr_sectors;
2005  giveup:
2006         /* There is nowhere to write, so all non-sync
2007          * drives must be failed, so try the next chunk...
2008          */
2009         {
2010         sector_t sec = max_sector - sector_nr;
2011         sectors_skipped += sec;
2012         chunks_skipped ++;
2013         sector_nr = max_sector;
2014         goto skipped;
2015         }
2016 }
2017
2018 static int run(mddev_t *mddev)
2019 {
2020         conf_t *conf;
2021         int i, disk_idx;
2022         mirror_info_t *disk;
2023         mdk_rdev_t *rdev;
2024         struct list_head *tmp;
2025         int nc, fc, fo;
2026         sector_t stride, size;
2027
2028         if (mddev->chunk_size == 0) {
2029                 printk(KERN_ERR "md/raid10: non-zero chunk size required.\n");
2030                 return -EINVAL;
2031         }
2032
2033         nc = mddev->layout & 255;
2034         fc = (mddev->layout >> 8) & 255;
2035         fo = mddev->layout & (1<<16);
2036         if ((nc*fc) <2 || (nc*fc) > mddev->raid_disks ||
2037             (mddev->layout >> 17)) {
2038                 printk(KERN_ERR "raid10: %s: unsupported raid10 layout: 0x%8x\n",
2039                        mdname(mddev), mddev->layout);
2040                 goto out;
2041         }
2042         /*
2043          * copy the already verified devices into our private RAID10
2044          * bookkeeping area. [whatever we allocate in run(),
2045          * should be freed in stop()]
2046          */
2047         conf = kzalloc(sizeof(conf_t), GFP_KERNEL);
2048         mddev->private = conf;
2049         if (!conf) {
2050                 printk(KERN_ERR "raid10: couldn't allocate memory for %s\n",
2051                         mdname(mddev));
2052                 goto out;
2053         }
2054         conf->mirrors = kzalloc(sizeof(struct mirror_info)*mddev->raid_disks,
2055                                  GFP_KERNEL);
2056         if (!conf->mirrors) {
2057                 printk(KERN_ERR "raid10: couldn't allocate memory for %s\n",
2058                        mdname(mddev));
2059                 goto out_free_conf;
2060         }
2061
2062         conf->tmppage = alloc_page(GFP_KERNEL);
2063         if (!conf->tmppage)
2064                 goto out_free_conf;
2065
2066         conf->mddev = mddev;
2067         conf->raid_disks = mddev->raid_disks;
2068         conf->near_copies = nc;
2069         conf->far_copies = fc;
2070         conf->copies = nc*fc;
2071         conf->far_offset = fo;
2072         conf->chunk_mask = (sector_t)(mddev->chunk_size>>9)-1;
2073         conf->chunk_shift = ffz(~mddev->chunk_size) - 9;
2074         size = mddev->size >> (conf->chunk_shift-1);
2075         sector_div(size, fc);
2076         size = size * conf->raid_disks;
2077         sector_div(size, nc);
2078         /* 'size' is now the number of chunks in the array */
2079         /* calculate "used chunks per device" in 'stride' */
2080         stride = size * conf->copies;
2081
2082         /* We need to round up when dividing by raid_disks to
2083          * get the stride size.
2084          */
2085         stride += conf->raid_disks - 1;
2086         sector_div(stride, conf->raid_disks);
2087         mddev->size = stride  << (conf->chunk_shift-1);
2088
2089         if (fo)
2090                 stride = 1;
2091         else
2092                 sector_div(stride, fc);
2093         conf->stride = stride << conf->chunk_shift;
2094
2095         conf->r10bio_pool = mempool_create(NR_RAID10_BIOS, r10bio_pool_alloc,
2096                                                 r10bio_pool_free, conf);
2097         if (!conf->r10bio_pool) {
2098                 printk(KERN_ERR "raid10: couldn't allocate memory for %s\n",
2099                         mdname(mddev));
2100                 goto out_free_conf;
2101         }
2102
2103         spin_lock_init(&conf->device_lock);
2104         mddev->queue->queue_lock = &conf->device_lock;
2105
2106         rdev_for_each(rdev, tmp, mddev) {
2107                 disk_idx = rdev->raid_disk;
2108                 if (disk_idx >= mddev->raid_disks
2109                     || disk_idx < 0)
2110                         continue;
2111                 disk = conf->mirrors + disk_idx;
2112
2113                 disk->rdev = rdev;
2114
2115                 blk_queue_stack_limits(mddev->queue,
2116                                        rdev->bdev->bd_disk->queue);
2117                 /* as we don't honour merge_bvec_fn, we must never risk
2118                  * violating it, so limit ->max_sector to one PAGE, as
2119                  * a one page request is never in violation.
2120                  */
2121                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
2122                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
2123                         mddev->queue->max_sectors = (PAGE_SIZE>>9);
2124
2125                 disk->head_position = 0;
2126         }
2127         INIT_LIST_HEAD(&conf->retry_list);
2128
2129         spin_lock_init(&conf->resync_lock);
2130         init_waitqueue_head(&conf->wait_barrier);
2131
2132         /* need to check that every block has at least one working mirror */
2133         if (!enough(conf)) {
2134                 printk(KERN_ERR "raid10: not enough operational mirrors for %s\n",
2135                        mdname(mddev));
2136                 goto out_free_conf;
2137         }
2138
2139         mddev->degraded = 0;
2140         for (i = 0; i < conf->raid_disks; i++) {
2141
2142                 disk = conf->mirrors + i;
2143
2144                 if (!disk->rdev ||
2145                     !test_bit(In_sync, &disk->rdev->flags)) {
2146                         disk->head_position = 0;
2147                         mddev->degraded++;
2148                         if (disk->rdev)
2149                                 conf->fullsync = 1;
2150                 }
2151         }
2152
2153
2154         mddev->thread = md_register_thread(raid10d, mddev, "%s_raid10");
2155         if (!mddev->thread) {
2156                 printk(KERN_ERR
2157                        "raid10: couldn't allocate thread for %s\n",
2158                        mdname(mddev));
2159                 goto out_free_conf;
2160         }
2161
2162         printk(KERN_INFO
2163                 "raid10: raid set %s active with %d out of %d devices\n",
2164                 mdname(mddev), mddev->raid_disks - mddev->degraded,
2165                 mddev->raid_disks);
2166         /*
2167          * Ok, everything is just fine now
2168          */
2169         mddev->array_sectors = size << conf->chunk_shift;
2170         mddev->resync_max_sectors = size << conf->chunk_shift;
2171
2172         mddev->queue->unplug_fn = raid10_unplug;
2173         mddev->queue->backing_dev_info.congested_fn = raid10_congested;
2174         mddev->queue->backing_dev_info.congested_data = mddev;
2175
2176         /* Calculate max read-ahead size.
2177          * We need to readahead at least twice a whole stripe....
2178          * maybe...
2179          */
2180         {
2181                 int stripe = conf->raid_disks * (mddev->chunk_size / PAGE_SIZE);
2182                 stripe /= conf->near_copies;
2183                 if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
2184                         mddev->queue->backing_dev_info.ra_pages = 2* stripe;
2185         }
2186
2187         if (conf->near_copies < mddev->raid_disks)
2188                 blk_queue_merge_bvec(mddev->queue, raid10_mergeable_bvec);
2189         return 0;
2190
2191 out_free_conf:
2192         if (conf->r10bio_pool)
2193                 mempool_destroy(conf->r10bio_pool);
2194         safe_put_page(conf->tmppage);
2195         kfree(conf->mirrors);
2196         kfree(conf);
2197         mddev->private = NULL;
2198 out:
2199         return -EIO;
2200 }
2201
2202 static int stop(mddev_t *mddev)
2203 {
2204         conf_t *conf = mddev_to_conf(mddev);
2205
2206         md_unregister_thread(mddev->thread);
2207         mddev->thread = NULL;
2208         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
2209         if (conf->r10bio_pool)
2210                 mempool_destroy(conf->r10bio_pool);
2211         kfree(conf->mirrors);
2212         kfree(conf);
2213         mddev->private = NULL;
2214         return 0;
2215 }
2216
2217 static void raid10_quiesce(mddev_t *mddev, int state)
2218 {
2219         conf_t *conf = mddev_to_conf(mddev);
2220
2221         switch(state) {
2222         case 1:
2223                 raise_barrier(conf, 0);
2224                 break;
2225         case 0:
2226                 lower_barrier(conf);
2227                 break;
2228         }
2229         if (mddev->thread) {
2230                 if (mddev->bitmap)
2231                         mddev->thread->timeout = mddev->bitmap->daemon_sleep * HZ;
2232                 else
2233                         mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
2234                 md_wakeup_thread(mddev->thread);
2235         }
2236 }
2237
2238 static struct mdk_personality raid10_personality =
2239 {
2240         .name           = "raid10",
2241         .level          = 10,
2242         .owner          = THIS_MODULE,
2243         .make_request   = make_request,
2244         .run            = run,
2245         .stop           = stop,
2246         .status         = status,
2247         .error_handler  = error,
2248         .hot_add_disk   = raid10_add_disk,
2249         .hot_remove_disk= raid10_remove_disk,
2250         .spare_active   = raid10_spare_active,
2251         .sync_request   = sync_request,
2252         .quiesce        = raid10_quiesce,
2253 };
2254
2255 static int __init raid_init(void)
2256 {
2257         return register_md_personality(&raid10_personality);
2258 }
2259
2260 static void raid_exit(void)
2261 {
2262         unregister_md_personality(&raid10_personality);
2263 }
2264
2265 module_init(raid_init);
2266 module_exit(raid_exit);
2267 MODULE_LICENSE("GPL");
2268 MODULE_ALIAS("md-personality-9"); /* RAID10 */
2269 MODULE_ALIAS("md-raid10");
2270 MODULE_ALIAS("md-level-10");