drivers/md/raid6main.c

   1 /*
   2  * raid6main.c : Multiple Devices driver for Linux
   3  *         Copyright (C) 1996, 1997 Ingo Molnar, Miguel de Icaza, Gadi Oxman
   4  *         Copyright (C) 1999, 2000 Ingo Molnar
   5  *         Copyright (C) 2002, 2003 H. Peter Anvin
   6  *
   7  * RAID-6 management functions.  This code is derived from raid5.c.
   8  * Last merge from raid5.c bkcvs version 1.79 (kernel 2.6.1).
   9  *
  10  * Thanks to Penguin Computing for making the RAID-6 development possible
  11  * by donating a test server!
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2, or (at your option)
  16  * any later version.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * (for example /usr/src/linux/COPYING); if not, write to the Free
  20  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23
  24 #include <linux/config.h>
  25 #include <linux/module.h>
  26 #include <linux/slab.h>
  27 #include <linux/highmem.h>
  28 #include <linux/bitops.h>
  29 #include <asm/atomic.h>
  30 #include "raid6.h"
  31
  32 #include <linux/raid/bitmap.h>
  33
  34 /*
  35  * Stripe cache
  36  */
  37
  38 #define NR_STRIPES              256
  39 #define STRIPE_SIZE             PAGE_SIZE
  40 #define STRIPE_SHIFT            (PAGE_SHIFT - 9)
  41 #define STRIPE_SECTORS          (STRIPE_SIZE>>9)
  42 #define IO_THRESHOLD            1
  43 #define NR_HASH                 (PAGE_SIZE / sizeof(struct hlist_head))
  44 #define HASH_MASK               (NR_HASH - 1)
  45
  46 #define stripe_hash(conf, sect) (&((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK]))
  47
  48 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
  49  * order without overlap.  There may be several bio's per stripe+device, and
  50  * a bio could span several devices.
  51  * When walking this list for a particular stripe+device, we must never proceed
  52  * beyond a bio that extends past this device, as the next bio might no longer
  53  * be valid.
  54  * This macro is used to determine the 'next' bio in the list, given the sector
  55  * of the current stripe+device
  56  */
  57 #define r5_next_bio(bio, sect) ( ( (bio)->bi_sector + ((bio)->bi_size>>9) < sect + STRIPE_SECTORS) ? (bio)->bi_next : NULL)
  58 /*
  59  * The following can be used to debug the driver
  60  */
  61 #define RAID6_DEBUG     0       /* Extremely verbose printk */
  62 #define RAID6_PARANOIA  1       /* Check spinlocks */
  63 #define RAID6_DUMPSTATE 0       /* Include stripe cache state in /proc/mdstat */
  64 #if RAID6_PARANOIA && defined(CONFIG_SMP)
  65 # define CHECK_DEVLOCK() assert_spin_locked(&conf->device_lock)
  66 #else
  67 # define CHECK_DEVLOCK()
  68 #endif
  69
  70 #define PRINTK(x...) ((void)(RAID6_DEBUG && printk(KERN_DEBUG x)))
  71 #if RAID6_DEBUG
  72 #undef inline
  73 #undef __inline__
  74 #define inline
  75 #define __inline__
  76 #endif
  77
  78 #if !RAID6_USE_EMPTY_ZERO_PAGE
  79 /* In .bss so it's zeroed */
  80 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
  81 #endif
  82
  83 static inline int raid6_next_disk(int disk, int raid_disks)
  84 {
  85         disk++;
  86         return (disk < raid_disks) ? disk : 0;
  87 }
  88
  89 static void print_raid6_conf (raid6_conf_t *conf);
  90
  91 static void __release_stripe(raid6_conf_t *conf, struct stripe_head *sh)
  92 {
  93         if (atomic_dec_and_test(&sh->count)) {
  94                 BUG_ON(!list_empty(&sh->lru));
  95                 BUG_ON(atomic_read(&conf->active_stripes)==0);
  96                 if (test_bit(STRIPE_HANDLE, &sh->state)) {
  97                         if (test_bit(STRIPE_DELAYED, &sh->state))
  98                                 list_add_tail(&sh->lru, &conf->delayed_list);
  99                         else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
 100                                  conf->seq_write == sh->bm_seq)
 101                                 list_add_tail(&sh->lru, &conf->bitmap_list);
 102                         else {
 103                                 clear_bit(STRIPE_BIT_DELAY, &sh->state);
 104                                 list_add_tail(&sh->lru, &conf->handle_list);
 105                         }
 106                         md_wakeup_thread(conf->mddev->thread);
 107                 } else {
 108                         if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
 109                                 atomic_dec(&conf->preread_active_stripes);
 110                                 if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
 111                                         md_wakeup_thread(conf->mddev->thread);
 112                         }
 113                         list_add_tail(&sh->lru, &conf->inactive_list);
 114                         atomic_dec(&conf->active_stripes);
 115                         if (!conf->inactive_blocked ||
 116                             atomic_read(&conf->active_stripes) < (conf->max_nr_stripes*3/4))
 117                                 wake_up(&conf->wait_for_stripe);
 118                 }
 119         }
 120 }
 121 static void release_stripe(struct stripe_head *sh)
 122 {
 123         raid6_conf_t *conf = sh->raid_conf;
 124         unsigned long flags;
 125
 126         spin_lock_irqsave(&conf->device_lock, flags);
 127         __release_stripe(conf, sh);
 128         spin_unlock_irqrestore(&conf->device_lock, flags);
 129 }
 130
 131 static inline void remove_hash(struct stripe_head *sh)
 132 {
 133         PRINTK("remove_hash(), stripe %llu\n", (unsigned long long)sh->sector);
 134
 135         hlist_del_init(&sh->hash);
 136 }
 137
 138 static inline void insert_hash(raid6_conf_t *conf, struct stripe_head *sh)
 139 {
 140         struct hlist_head *hp = stripe_hash(conf, sh->sector);
 141
 142         PRINTK("insert_hash(), stripe %llu\n", (unsigned long long)sh->sector);
 143
 144         CHECK_DEVLOCK();
 145         hlist_add_head(&sh->hash, hp);
 146 }
 147
 148
 149 /* find an idle stripe, make sure it is unhashed, and return it. */
 150 static struct stripe_head *get_free_stripe(raid6_conf_t *conf)
 151 {
 152         struct stripe_head *sh = NULL;
 153         struct list_head *first;
 154
 155         CHECK_DEVLOCK();
 156         if (list_empty(&conf->inactive_list))
 157                 goto out;
 158         first = conf->inactive_list.next;
 159         sh = list_entry(first, struct stripe_head, lru);
 160         list_del_init(first);
 161         remove_hash(sh);
 162         atomic_inc(&conf->active_stripes);
 163 out:
 164         return sh;
 165 }
 166
 167 static void shrink_buffers(struct stripe_head *sh, int num)
 168 {
 169         struct page *p;
 170         int i;
 171
 172         for (i=0; i<num ; i++) {
 173                 p = sh->dev[i].page;
 174                 if (!p)
 175                         continue;
 176                 sh->dev[i].page = NULL;
 177                 put_page(p);
 178         }
 179 }
 180
 181 static int grow_buffers(struct stripe_head *sh, int num)
 182 {
 183         int i;
 184
 185         for (i=0; i<num; i++) {
 186                 struct page *page;
 187
 188                 if (!(page = alloc_page(GFP_KERNEL))) {
 189                         return 1;
 190                 }
 191                 sh->dev[i].page = page;
 192         }
 193         return 0;
 194 }
 195
 196 static void raid6_build_block (struct stripe_head *sh, int i);
 197
 198 static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx)
 199 {
 200         raid6_conf_t *conf = sh->raid_conf;
 201         int disks = conf->raid_disks, i;
 202
 203         BUG_ON(atomic_read(&sh->count) != 0);
 204         BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
 205
 206         CHECK_DEVLOCK();
 207         PRINTK("init_stripe called, stripe %llu\n",
 208                 (unsigned long long)sh->sector);
 209
 210         remove_hash(sh);
 211
 212         sh->sector = sector;
 213         sh->pd_idx = pd_idx;
 214         sh->state = 0;
 215
 216         for (i=disks; i--; ) {
 217                 struct r5dev *dev = &sh->dev[i];
 218
 219                 if (dev->toread || dev->towrite || dev->written ||
 220                     test_bit(R5_LOCKED, &dev->flags)) {
 221                         PRINTK("sector=%llx i=%d %p %p %p %d\n",
 222                                (unsigned long long)sh->sector, i, dev->toread,
 223                                dev->towrite, dev->written,
 224                                test_bit(R5_LOCKED, &dev->flags));
 225                         BUG();
 226                 }
 227                 dev->flags = 0;
 228                 raid6_build_block(sh, i);
 229         }
 230         insert_hash(conf, sh);
 231 }
 232
 233 static struct stripe_head *__find_stripe(raid6_conf_t *conf, sector_t sector)
 234 {
 235         struct stripe_head *sh;
 236         struct hlist_node *hn;
 237
 238         CHECK_DEVLOCK();
 239         PRINTK("__find_stripe, sector %llu\n", (unsigned long long)sector);
 240         hlist_for_each_entry (sh, hn,  stripe_hash(conf, sector), hash)
 241                 if (sh->sector == sector)
 242                         return sh;
 243         PRINTK("__stripe %llu not in cache\n", (unsigned long long)sector);
 244         return NULL;
 245 }
 246
 247 static void unplug_slaves(mddev_t *mddev);
 248
 249 static struct stripe_head *get_active_stripe(raid6_conf_t *conf, sector_t sector,
 250                                              int pd_idx, int noblock)
 251 {
 252         struct stripe_head *sh;
 253
 254         PRINTK("get_stripe, sector %llu\n", (unsigned long long)sector);
 255
 256         spin_lock_irq(&conf->device_lock);
 257
 258         do {
 259                 wait_event_lock_irq(conf->wait_for_stripe,
 260                                     conf->quiesce == 0,
 261                                     conf->device_lock, /* nothing */);
 262                 sh = __find_stripe(conf, sector);
 263                 if (!sh) {
 264                         if (!conf->inactive_blocked)
 265                                 sh = get_free_stripe(conf);
 266                         if (noblock && sh == NULL)
 267                                 break;
 268                         if (!sh) {
 269                                 conf->inactive_blocked = 1;
 270                                 wait_event_lock_irq(conf->wait_for_stripe,
 271                                                     !list_empty(&conf->inactive_list) &&
 272                                                     (atomic_read(&conf->active_stripes)
 273                                                      < (conf->max_nr_stripes *3/4)
 274                                                      || !conf->inactive_blocked),
 275                                                     conf->device_lock,
 276                                                     unplug_slaves(conf->mddev);
 277                                         );
 278                                 conf->inactive_blocked = 0;
 279                         } else
 280                                 init_stripe(sh, sector, pd_idx);
 281                 } else {
 282                         if (atomic_read(&sh->count)) {
 283                                 BUG_ON(!list_empty(&sh->lru));
 284                         } else {
 285                                 if (!test_bit(STRIPE_HANDLE, &sh->state))
 286                                         atomic_inc(&conf->active_stripes);
 287                                 BUG_ON(list_empty(&sh->lru));
 288                                 list_del_init(&sh->lru);
 289                         }
 290                 }
 291         } while (sh == NULL);
 292
 293         if (sh)
 294                 atomic_inc(&sh->count);
 295
 296         spin_unlock_irq(&conf->device_lock);
 297         return sh;
 298 }
 299
 300 static int grow_one_stripe(raid6_conf_t *conf)
 301 {
 302         struct stripe_head *sh;
 303         sh = kmem_cache_alloc(conf->slab_cache, GFP_KERNEL);
 304         if (!sh)
 305                 return 0;
 306         memset(sh, 0, sizeof(*sh) + (conf->raid_disks-1)*sizeof(struct r5dev));
 307         sh->raid_conf = conf;
 308         spin_lock_init(&sh->lock);
 309
 310         if (grow_buffers(sh, conf->raid_disks)) {
 311                 shrink_buffers(sh, conf->raid_disks);
 312                 kmem_cache_free(conf->slab_cache, sh);
 313                 return 0;
 314         }
 315         /* we just created an active stripe so... */
 316         atomic_set(&sh->count, 1);
 317         atomic_inc(&conf->active_stripes);
 318         INIT_LIST_HEAD(&sh->lru);
 319         release_stripe(sh);
 320         return 1;
 321 }
 322
 323 static int grow_stripes(raid6_conf_t *conf, int num)
 324 {
 325         kmem_cache_t *sc;
 326         int devs = conf->raid_disks;
 327
 328         sprintf(conf->cache_name[0], "raid6/%s", mdname(conf->mddev));
 329
 330         sc = kmem_cache_create(conf->cache_name[0],
 331                                sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
 332                                0, 0, NULL, NULL);
 333         if (!sc)
 334                 return 1;
 335         conf->slab_cache = sc;
 336         while (num--)
 337                 if (!grow_one_stripe(conf))
 338                         return 1;
 339         return 0;
 340 }
 341
 342 static int drop_one_stripe(raid6_conf_t *conf)
 343 {
 344         struct stripe_head *sh;
 345         spin_lock_irq(&conf->device_lock);
 346         sh = get_free_stripe(conf);
 347         spin_unlock_irq(&conf->device_lock);
 348         if (!sh)
 349                 return 0;
 350         BUG_ON(atomic_read(&sh->count));
 351         shrink_buffers(sh, conf->raid_disks);
 352         kmem_cache_free(conf->slab_cache, sh);
 353         atomic_dec(&conf->active_stripes);
 354         return 1;
 355 }
 356
 357 static void shrink_stripes(raid6_conf_t *conf)
 358 {
 359         while (drop_one_stripe(conf))
 360                 ;
 361
 362         if (conf->slab_cache)
 363                 kmem_cache_destroy(conf->slab_cache);
 364         conf->slab_cache = NULL;
 365 }
 366
 367 static int raid6_end_read_request(struct bio * bi, unsigned int bytes_done,
 368                                   int error)
 369 {
 370         struct stripe_head *sh = bi->bi_private;
 371         raid6_conf_t *conf = sh->raid_conf;
 372         int disks = conf->raid_disks, i;
 373         int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
 374
 375         if (bi->bi_size)
 376                 return 1;
 377
 378         for (i=0 ; i<disks; i++)
 379                 if (bi == &sh->dev[i].req)
 380                         break;
 381
 382         PRINTK("end_read_request %llu/%d, count: %d, uptodate %d.\n",
 383                 (unsigned long long)sh->sector, i, atomic_read(&sh->count),
 384                 uptodate);
 385         if (i == disks) {
 386                 BUG();
 387                 return 0;
 388         }
 389
 390         if (uptodate) {
 391 #if 0
 392                 struct bio *bio;
 393                 unsigned long flags;
 394                 spin_lock_irqsave(&conf->device_lock, flags);
 395                 /* we can return a buffer if we bypassed the cache or
 396                  * if the top buffer is not in highmem.  If there are
 397                  * multiple buffers, leave the extra work to
 398                  * handle_stripe
 399                  */
 400                 buffer = sh->bh_read[i];
 401                 if (buffer &&
 402                     (!PageHighMem(buffer->b_page)
 403                      || buffer->b_page == bh->b_page )
 404                         ) {
 405                         sh->bh_read[i] = buffer->b_reqnext;
 406                         buffer->b_reqnext = NULL;
 407                 } else
 408                         buffer = NULL;
 409                 spin_unlock_irqrestore(&conf->device_lock, flags);
 410                 if (sh->bh_page[i]==bh->b_page)
 411                         set_buffer_uptodate(bh);
 412                 if (buffer) {
 413                         if (buffer->b_page != bh->b_page)
 414                                 memcpy(buffer->b_data, bh->b_data, bh->b_size);
 415                         buffer->b_end_io(buffer, 1);
 416                 }
 417 #else
 418                 set_bit(R5_UPTODATE, &sh->dev[i].flags);
 419 #endif
 420                 if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
 421                         printk(KERN_INFO "raid6: read error corrected!!\n");
 422                         clear_bit(R5_ReadError, &sh->dev[i].flags);
 423                         clear_bit(R5_ReWrite, &sh->dev[i].flags);
 424                 }
 425                 if (atomic_read(&conf->disks[i].rdev->read_errors))
 426                         atomic_set(&conf->disks[i].rdev->read_errors, 0);
 427         } else {
 428                 int retry = 0;
 429                 clear_bit(R5_UPTODATE, &sh->dev[i].flags);
 430                 atomic_inc(&conf->disks[i].rdev->read_errors);
 431                 if (conf->mddev->degraded)
 432                         printk(KERN_WARNING "raid6: read error not correctable.\n");
 433                 else if (test_bit(R5_ReWrite, &sh->dev[i].flags))
 434                         /* Oh, no!!! */
 435                         printk(KERN_WARNING "raid6: read error NOT corrected!!\n");
 436                 else if (atomic_read(&conf->disks[i].rdev->read_errors)
 437                          > conf->max_nr_stripes)
 438                         printk(KERN_WARNING
 439                                "raid6: Too many read errors, failing device.\n");
 440                 else
 441                         retry = 1;
 442                 if (retry)
 443                         set_bit(R5_ReadError, &sh->dev[i].flags);
 444                 else {
 445                         clear_bit(R5_ReadError, &sh->dev[i].flags);
 446                         clear_bit(R5_ReWrite, &sh->dev[i].flags);
 447                         md_error(conf->mddev, conf->disks[i].rdev);
 448                 }
 449         }
 450         rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
 451 #if 0
 452         /* must restore b_page before unlocking buffer... */
 453         if (sh->bh_page[i] != bh->b_page) {
 454                 bh->b_page = sh->bh_page[i];
 455                 bh->b_data = page_address(bh->b_page);
 456                 clear_buffer_uptodate(bh);
 457         }
 458 #endif
 459         clear_bit(R5_LOCKED, &sh->dev[i].flags);
 460         set_bit(STRIPE_HANDLE, &sh->state);
 461         release_stripe(sh);
 462         return 0;
 463 }
 464
 465 static int raid6_end_write_request (struct bio *bi, unsigned int bytes_done,
 466                                     int error)
 467 {
 468         struct stripe_head *sh = bi->bi_private;
 469         raid6_conf_t *conf = sh->raid_conf;
 470         int disks = conf->raid_disks, i;
 471         unsigned long flags;
 472         int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
 473
 474         if (bi->bi_size)
 475                 return 1;
 476
 477         for (i=0 ; i<disks; i++)
 478                 if (bi == &sh->dev[i].req)
 479                         break;
 480
 481         PRINTK("end_write_request %llu/%d, count %d, uptodate: %d.\n",
 482                 (unsigned long long)sh->sector, i, atomic_read(&sh->count),
 483                 uptodate);
 484         if (i == disks) {
 485                 BUG();
 486                 return 0;
 487         }
 488
 489         spin_lock_irqsave(&conf->device_lock, flags);
 490         if (!uptodate)
 491                 md_error(conf->mddev, conf->disks[i].rdev);
 492
 493         rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
 494
 495         clear_bit(R5_LOCKED, &sh->dev[i].flags);
 496         set_bit(STRIPE_HANDLE, &sh->state);
 497         __release_stripe(conf, sh);
 498         spin_unlock_irqrestore(&conf->device_lock, flags);
 499         return 0;
 500 }
 501
 502
 503 static sector_t compute_blocknr(struct stripe_head *sh, int i);
 504
 505 static void raid6_build_block (struct stripe_head *sh, int i)
 506 {
 507         struct r5dev *dev = &sh->dev[i];
 508         int pd_idx = sh->pd_idx;
 509         int qd_idx = raid6_next_disk(pd_idx, sh->raid_conf->raid_disks);
 510
 511         bio_init(&dev->req);
 512         dev->req.bi_io_vec = &dev->vec;
 513         dev->req.bi_vcnt++;
 514         dev->req.bi_max_vecs++;
 515         dev->vec.bv_page = dev->page;
 516         dev->vec.bv_len = STRIPE_SIZE;
 517         dev->vec.bv_offset = 0;
 518
 519         dev->req.bi_sector = sh->sector;
 520         dev->req.bi_private = sh;
 521
 522         dev->flags = 0;
 523         if (i != pd_idx && i != qd_idx)
 524                 dev->sector = compute_blocknr(sh, i);
 525 }
 526
 527 static void error(mddev_t *mddev, mdk_rdev_t *rdev)
 528 {
 529         char b[BDEVNAME_SIZE];
 530         raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
 531         PRINTK("raid6: error called\n");
 532
 533         if (!test_bit(Faulty, &rdev->flags)) {
 534                 mddev->sb_dirty = 1;
 535                 if (test_bit(In_sync, &rdev->flags)) {
 536                         conf->working_disks--;
 537                         mddev->degraded++;
 538                         conf->failed_disks++;
 539                         clear_bit(In_sync, &rdev->flags);
 540                         /*
 541                          * if recovery was running, make sure it aborts.
 542                          */
 543                         set_bit(MD_RECOVERY_ERR, &mddev->recovery);
 544                 }
 545                 set_bit(Faulty, &rdev->flags);
 546                 printk (KERN_ALERT
 547                         "raid6: Disk failure on %s, disabling device."
 548                         " Operation continuing on %d devices\n",
 549                         bdevname(rdev->bdev,b), conf->working_disks);
 550         }
 551 }
 552
 553 /*
 554  * Input: a 'big' sector number,
 555  * Output: index of the data and parity disk, and the sector # in them.
 556  */
 557 static sector_t raid6_compute_sector(sector_t r_sector, unsigned int raid_disks,
 558                         unsigned int data_disks, unsigned int * dd_idx,
 559                         unsigned int * pd_idx, raid6_conf_t *conf)
 560 {
 561         long stripe;
 562         unsigned long chunk_number;
 563         unsigned int chunk_offset;
 564         sector_t new_sector;
 565         int sectors_per_chunk = conf->chunk_size >> 9;
 566
 567         /* First compute the information on this sector */
 568
 569         /*
 570          * Compute the chunk number and the sector offset inside the chunk
 571          */
 572         chunk_offset = sector_div(r_sector, sectors_per_chunk);
 573         chunk_number = r_sector;
 574         if ( r_sector != chunk_number ) {
 575                 printk(KERN_CRIT "raid6: ERROR: r_sector = %llu, chunk_number = %lu\n",
 576                        (unsigned long long)r_sector, (unsigned long)chunk_number);
 577                 BUG();
 578         }
 579
 580         /*
 581          * Compute the stripe number
 582          */
 583         stripe = chunk_number / data_disks;
 584
 585         /*
 586          * Compute the data disk and parity disk indexes inside the stripe
 587          */
 588         *dd_idx = chunk_number % data_disks;
 589
 590         /*
 591          * Select the parity disk based on the user selected algorithm.
 592          */
 593
 594         /**** FIX THIS ****/
 595         switch (conf->algorithm) {
 596         case ALGORITHM_LEFT_ASYMMETRIC:
 597                 *pd_idx = raid_disks - 1 - (stripe % raid_disks);
 598                 if (*pd_idx == raid_disks-1)
 599                         (*dd_idx)++;    /* Q D D D P */
 600                 else if (*dd_idx >= *pd_idx)
 601                         (*dd_idx) += 2; /* D D P Q D */
 602                 break;
 603         case ALGORITHM_RIGHT_ASYMMETRIC:
 604                 *pd_idx = stripe % raid_disks;
 605                 if (*pd_idx == raid_disks-1)
 606                         (*dd_idx)++;    /* Q D D D P */
 607                 else if (*dd_idx >= *pd_idx)
 608                         (*dd_idx) += 2; /* D D P Q D */
 609                 break;
 610         case ALGORITHM_LEFT_SYMMETRIC:
 611                 *pd_idx = raid_disks - 1 - (stripe % raid_disks);
 612                 *dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
 613                 break;
 614         case ALGORITHM_RIGHT_SYMMETRIC:
 615                 *pd_idx = stripe % raid_disks;
 616                 *dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
 617                 break;
 618         default:
 619                 printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
 620                         conf->algorithm);
 621         }
 622
 623         PRINTK("raid6: chunk_number = %lu, pd_idx = %u, dd_idx = %u\n",
 624                chunk_number, *pd_idx, *dd_idx);
 625
 626         /*
 627          * Finally, compute the new sector number
 628          */
 629         new_sector = (sector_t) stripe * sectors_per_chunk + chunk_offset;
 630         return new_sector;
 631 }
 632
 633
 634 static sector_t compute_blocknr(struct stripe_head *sh, int i)
 635 {
 636         raid6_conf_t *conf = sh->raid_conf;
 637         int raid_disks = conf->raid_disks, data_disks = raid_disks - 2;
 638         sector_t new_sector = sh->sector, check;
 639         int sectors_per_chunk = conf->chunk_size >> 9;
 640         sector_t stripe;
 641         int chunk_offset;
 642         int chunk_number, dummy1, dummy2, dd_idx = i;
 643         sector_t r_sector;
 644         int i0 = i;
 645
 646         chunk_offset = sector_div(new_sector, sectors_per_chunk);
 647         stripe = new_sector;
 648         if ( new_sector != stripe ) {
 649                 printk(KERN_CRIT "raid6: ERROR: new_sector = %llu, stripe = %lu\n",
 650                        (unsigned long long)new_sector, (unsigned long)stripe);
 651                 BUG();
 652         }
 653
 654         switch (conf->algorithm) {
 655                 case ALGORITHM_LEFT_ASYMMETRIC:
 656                 case ALGORITHM_RIGHT_ASYMMETRIC:
 657                         if (sh->pd_idx == raid_disks-1)
 658                                 i--;    /* Q D D D P */
 659                         else if (i > sh->pd_idx)
 660                                 i -= 2; /* D D P Q D */
 661                         break;
 662                 case ALGORITHM_LEFT_SYMMETRIC:
 663                 case ALGORITHM_RIGHT_SYMMETRIC:
 664                         if (sh->pd_idx == raid_disks-1)
 665                                 i--; /* Q D D D P */
 666                         else {
 667                                 /* D D P Q D */
 668                                 if (i < sh->pd_idx)
 669                                         i += raid_disks;
 670                                 i -= (sh->pd_idx + 2);
 671                         }
 672                         break;
 673                 default:
 674                         printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
 675                                 conf->algorithm);
 676         }
 677
 678         PRINTK("raid6: compute_blocknr: pd_idx = %u, i0 = %u, i = %u\n", sh->pd_idx, i0, i);
 679
 680         chunk_number = stripe * data_disks + i;
 681         r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
 682
 683         check = raid6_compute_sector (r_sector, raid_disks, data_disks, &dummy1, &dummy2, conf);
 684         if (check != sh->sector || dummy1 != dd_idx || dummy2 != sh->pd_idx) {
 685                 printk(KERN_CRIT "raid6: compute_blocknr: map not correct\n");
 686                 return 0;
 687         }
 688         return r_sector;
 689 }
 690
 691
 692
 693 /*
 694  * Copy data between a page in the stripe cache, and one or more bion
 695  * The page could align with the middle of the bio, or there could be
 696  * several bion, each with several bio_vecs, which cover part of the page
 697  * Multiple bion are linked together on bi_next.  There may be extras
 698  * at the end of this list.  We ignore them.
 699  */
 700 static void copy_data(int frombio, struct bio *bio,
 701                      struct page *page,
 702                      sector_t sector)
 703 {
 704         char *pa = page_address(page);
 705         struct bio_vec *bvl;
 706         int i;
 707         int page_offset;
 708
 709         if (bio->bi_sector >= sector)
 710                 page_offset = (signed)(bio->bi_sector - sector) * 512;
 711         else
 712                 page_offset = (signed)(sector - bio->bi_sector) * -512;
 713         bio_for_each_segment(bvl, bio, i) {
 714                 int len = bio_iovec_idx(bio,i)->bv_len;
 715                 int clen;
 716                 int b_offset = 0;
 717
 718                 if (page_offset < 0) {
 719                         b_offset = -page_offset;
 720                         page_offset += b_offset;
 721                         len -= b_offset;
 722                 }
 723
 724                 if (len > 0 && page_offset + len > STRIPE_SIZE)
 725                         clen = STRIPE_SIZE - page_offset;
 726                 else clen = len;
 727
 728                 if (clen > 0) {
 729                         char *ba = __bio_kmap_atomic(bio, i, KM_USER0);
 730                         if (frombio)
 731                                 memcpy(pa+page_offset, ba+b_offset, clen);
 732                         else
 733                                 memcpy(ba+b_offset, pa+page_offset, clen);
 734                         __bio_kunmap_atomic(ba, KM_USER0);
 735                 }
 736                 if (clen < len) /* hit end of page */
 737                         break;
 738                 page_offset +=  len;
 739         }
 740 }
 741
 742 #define check_xor()     do {                                            \
 743                            if (count == MAX_XOR_BLOCKS) {               \
 744                                 xor_block(count, STRIPE_SIZE, ptr);     \
 745                                 count = 1;                              \
 746                            }                                            \
 747                         } while(0)
 748
 749 /* Compute P and Q syndromes */
 750 static void compute_parity(struct stripe_head *sh, int method)
 751 {
 752         raid6_conf_t *conf = sh->raid_conf;
 753         int i, pd_idx = sh->pd_idx, qd_idx, d0_idx, disks = conf->raid_disks, count;
 754         struct bio *chosen;
 755         /**** FIX THIS: This could be very bad if disks is close to 256 ****/
 756         void *ptrs[disks];
 757
 758         qd_idx = raid6_next_disk(pd_idx, disks);
 759         d0_idx = raid6_next_disk(qd_idx, disks);
 760
 761         PRINTK("compute_parity, stripe %llu, method %d\n",
 762                 (unsigned long long)sh->sector, method);
 763
 764         switch(method) {
 765         case READ_MODIFY_WRITE:
 766                 BUG();          /* READ_MODIFY_WRITE N/A for RAID-6 */
 767         case RECONSTRUCT_WRITE:
 768                 for (i= disks; i-- ;)
 769                         if ( i != pd_idx && i != qd_idx && sh->dev[i].towrite ) {
 770                                 chosen = sh->dev[i].towrite;
 771                                 sh->dev[i].towrite = NULL;
 772
 773                                 if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
 774                                         wake_up(&conf->wait_for_overlap);
 775
 776                                 BUG_ON(sh->dev[i].written);
 777                                 sh->dev[i].written = chosen;
 778                         }
 779                 break;
 780         case CHECK_PARITY:
 781                 BUG();          /* Not implemented yet */
 782         }
 783
 784         for (i = disks; i--;)
 785                 if (sh->dev[i].written) {
 786                         sector_t sector = sh->dev[i].sector;
 787                         struct bio *wbi = sh->dev[i].written;
 788                         while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
 789                                 copy_data(1, wbi, sh->dev[i].page, sector);
 790                                 wbi = r5_next_bio(wbi, sector);
 791                         }
 792
 793                         set_bit(R5_LOCKED, &sh->dev[i].flags);
 794                         set_bit(R5_UPTODATE, &sh->dev[i].flags);
 795                 }
 796
 797 //      switch(method) {
 798 //      case RECONSTRUCT_WRITE:
 799 //      case CHECK_PARITY:
 800 //      case UPDATE_PARITY:
 801                 /* Note that unlike RAID-5, the ordering of the disks matters greatly. */
 802                 /* FIX: Is this ordering of drives even remotely optimal? */
 803                 count = 0;
 804                 i = d0_idx;
 805                 do {
 806                         ptrs[count++] = page_address(sh->dev[i].page);
 807                         if (count <= disks-2 && !test_bit(R5_UPTODATE, &sh->dev[i].flags))
 808                                 printk("block %d/%d not uptodate on parity calc\n", i,count);
 809                         i = raid6_next_disk(i, disks);
 810                 } while ( i != d0_idx );
 811 //              break;
 812 //      }
 813
 814         raid6_call.gen_syndrome(disks, STRIPE_SIZE, ptrs);
 815
 816         switch(method) {
 817         case RECONSTRUCT_WRITE:
 818                 set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
 819                 set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
 820                 set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
 821                 set_bit(R5_LOCKED,   &sh->dev[qd_idx].flags);
 822                 break;
 823         case UPDATE_PARITY:
 824                 set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
 825                 set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
 826                 break;
 827         }
 828 }
 829
 830 /* Compute one missing block */
 831 static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
 832 {
 833         raid6_conf_t *conf = sh->raid_conf;
 834         int i, count, disks = conf->raid_disks;
 835         void *ptr[MAX_XOR_BLOCKS], *p;
 836         int pd_idx = sh->pd_idx;
 837         int qd_idx = raid6_next_disk(pd_idx, disks);
 838
 839         PRINTK("compute_block_1, stripe %llu, idx %d\n",
 840                 (unsigned long long)sh->sector, dd_idx);
 841
 842         if ( dd_idx == qd_idx ) {
 843                 /* We're actually computing the Q drive */
 844                 compute_parity(sh, UPDATE_PARITY);
 845         } else {
 846                 ptr[0] = page_address(sh->dev[dd_idx].page);
 847                 if (!nozero) memset(ptr[0], 0, STRIPE_SIZE);
 848                 count = 1;
 849                 for (i = disks ; i--; ) {
 850                         if (i == dd_idx || i == qd_idx)
 851                                 continue;
 852                         p = page_address(sh->dev[i].page);
 853                         if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
 854                                 ptr[count++] = p;
 855                         else
 856                                 printk("compute_block() %d, stripe %llu, %d"
 857                                        " not present\n", dd_idx,
 858                                        (unsigned long long)sh->sector, i);
 859
 860                         check_xor();
 861                 }
 862                 if (count != 1)
 863                         xor_block(count, STRIPE_SIZE, ptr);
 864                 if (!nozero) set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
 865                 else clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
 866         }
 867 }
 868
 869 /* Compute two missing blocks */
 870 static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
 871 {
 872         raid6_conf_t *conf = sh->raid_conf;
 873         int i, count, disks = conf->raid_disks;
 874         int pd_idx = sh->pd_idx;
 875         int qd_idx = raid6_next_disk(pd_idx, disks);
 876         int d0_idx = raid6_next_disk(qd_idx, disks);
 877         int faila, failb;
 878
 879         /* faila and failb are disk numbers relative to d0_idx */
 880         /* pd_idx become disks-2 and qd_idx become disks-1 */
 881         faila = (dd_idx1 < d0_idx) ? dd_idx1+(disks-d0_idx) : dd_idx1-d0_idx;
 882         failb = (dd_idx2 < d0_idx) ? dd_idx2+(disks-d0_idx) : dd_idx2-d0_idx;
 883
 884         BUG_ON(faila == failb);
 885         if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
 886
 887         PRINTK("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
 888                (unsigned long long)sh->sector, dd_idx1, dd_idx2, faila, failb);
 889
 890         if ( failb == disks-1 ) {
 891                 /* Q disk is one of the missing disks */
 892                 if ( faila == disks-2 ) {
 893                         /* Missing P+Q, just recompute */
 894                         compute_parity(sh, UPDATE_PARITY);
 895                         return;
 896                 } else {
 897                         /* We're missing D+Q; recompute D from P */
 898                         compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1, 0);
 899                         compute_parity(sh, UPDATE_PARITY); /* Is this necessary? */
 900                         return;
 901                 }
 902         }
 903
 904         /* We're missing D+P or D+D; build pointer table */
 905         {
 906                 /**** FIX THIS: This could be very bad if disks is close to 256 ****/
 907                 void *ptrs[disks];
 908
 909                 count = 0;
 910                 i = d0_idx;
 911                 do {
 912                         ptrs[count++] = page_address(sh->dev[i].page);
 913                         i = raid6_next_disk(i, disks);
 914                         if (i != dd_idx1 && i != dd_idx2 &&
 915                             !test_bit(R5_UPTODATE, &sh->dev[i].flags))
 916                                 printk("compute_2 with missing block %d/%d\n", count, i);
 917                 } while ( i != d0_idx );
 918
 919                 if ( failb == disks-2 ) {
 920                         /* We're missing D+P. */
 921                         raid6_datap_recov(disks, STRIPE_SIZE, faila, ptrs);
 922                 } else {
 923                         /* We're missing D+D. */
 924                         raid6_2data_recov(disks, STRIPE_SIZE, faila, failb, ptrs);
 925                 }
 926
 927                 /* Both the above update both missing blocks */
 928                 set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
 929                 set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
 930         }
 931 }
 932
 933
 934 /*
 935  * Each stripe/dev can have one or more bion attached.
 936  * toread/towrite point to the first in a chain.
 937  * The bi_next chain must be in order.
 938  */
 939 static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, int forwrite)
 940 {
 941         struct bio **bip;
 942         raid6_conf_t *conf = sh->raid_conf;
 943         int firstwrite=0;
 944
 945         PRINTK("adding bh b#%llu to stripe s#%llu\n",
 946                 (unsigned long long)bi->bi_sector,
 947                 (unsigned long long)sh->sector);
 948
 949
 950         spin_lock(&sh->lock);
 951         spin_lock_irq(&conf->device_lock);
 952         if (forwrite) {
 953                 bip = &sh->dev[dd_idx].towrite;
 954                 if (*bip == NULL && sh->dev[dd_idx].written == NULL)
 955                         firstwrite = 1;
 956         } else
 957                 bip = &sh->dev[dd_idx].toread;
 958         while (*bip && (*bip)->bi_sector < bi->bi_sector) {
 959                 if ((*bip)->bi_sector + ((*bip)->bi_size >> 9) > bi->bi_sector)
 960                         goto overlap;
 961                 bip = &(*bip)->bi_next;
 962         }
 963         if (*bip && (*bip)->bi_sector < bi->bi_sector + ((bi->bi_size)>>9))
 964                 goto overlap;
 965
 966         BUG_ON(*bip && bi->bi_next && (*bip) != bi->bi_next);
 967         if (*bip)
 968                 bi->bi_next = *bip;
 969         *bip = bi;
 970         bi->bi_phys_segments ++;
 971         spin_unlock_irq(&conf->device_lock);
 972         spin_unlock(&sh->lock);
 973
 974         PRINTK("added bi b#%llu to stripe s#%llu, disk %d.\n",
 975                 (unsigned long long)bi->bi_sector,
 976                 (unsigned long long)sh->sector, dd_idx);
 977
 978         if (conf->mddev->bitmap && firstwrite) {
 979                 sh->bm_seq = conf->seq_write;
 980                 bitmap_startwrite(conf->mddev->bitmap, sh->sector,
 981                                   STRIPE_SECTORS, 0);
 982                 set_bit(STRIPE_BIT_DELAY, &sh->state);
 983         }
 984
 985         if (forwrite) {
 986                 /* check if page is covered */
 987                 sector_t sector = sh->dev[dd_idx].sector;
 988                 for (bi=sh->dev[dd_idx].towrite;
 989                      sector < sh->dev[dd_idx].sector + STRIPE_SECTORS &&
 990                              bi && bi->bi_sector <= sector;
 991                      bi = r5_next_bio(bi, sh->dev[dd_idx].sector)) {
 992                         if (bi->bi_sector + (bi->bi_size>>9) >= sector)
 993                                 sector = bi->bi_sector + (bi->bi_size>>9);
 994                 }
 995                 if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
 996                         set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
 997         }
 998         return 1;
 999
1000  overlap:
1001         set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
1002         spin_unlock_irq(&conf->device_lock);
1003         spin_unlock(&sh->lock);
1004         return 0;
1005 }
1006
1007
1008 static int page_is_zero(struct page *p)
1009 {
1010         char *a = page_address(p);
1011         return ((*(u32*)a) == 0 &&
1012                 memcmp(a, a+4, STRIPE_SIZE-4)==0);
1013 }
1014 /*
1015  * handle_stripe - do things to a stripe.
1016  *
1017  * We lock the stripe and then examine the state of various bits
1018  * to see what needs to be done.
1019  * Possible results:
1020  *    return some read request which now have data
1021  *    return some write requests which are safely on disc
1022  *    schedule a read on some buffers
1023  *    schedule a write of some buffers
1024  *    return confirmation of parity correctness
1025  *
1026  * Parity calculations are done inside the stripe lock
1027  * buffers are taken off read_list or write_list, and bh_cache buffers
1028  * get BH_Lock set before the stripe lock is released.
1029  *
1030  */
1031
1032 static void handle_stripe(struct stripe_head *sh, struct page *tmp_page)
1033 {
1034         raid6_conf_t *conf = sh->raid_conf;
1035         int disks = conf->raid_disks;
1036         struct bio *return_bi= NULL;
1037         struct bio *bi;
1038         int i;
1039         int syncing;
1040         int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
1041         int non_overwrite = 0;
1042         int failed_num[2] = {0, 0};
1043         struct r5dev *dev, *pdev, *qdev;
1044         int pd_idx = sh->pd_idx;
1045         int qd_idx = raid6_next_disk(pd_idx, disks);
1046         int p_failed, q_failed;
1047
1048         PRINTK("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d, qd_idx=%d\n",
1049                (unsigned long long)sh->sector, sh->state, atomic_read(&sh->count),
1050                pd_idx, qd_idx);
1051
1052         spin_lock(&sh->lock);
1053         clear_bit(STRIPE_HANDLE, &sh->state);
1054         clear_bit(STRIPE_DELAYED, &sh->state);
1055
1056         syncing = test_bit(STRIPE_SYNCING, &sh->state);
1057         /* Now to look around and see what can be done */
1058
1059         rcu_read_lock();
1060         for (i=disks; i--; ) {
1061                 mdk_rdev_t *rdev;
1062                 dev = &sh->dev[i];
1063                 clear_bit(R5_Insync, &dev->flags);
1064
1065                 PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
1066                         i, dev->flags, dev->toread, dev->towrite, dev->written);
1067                 /* maybe we can reply to a read */
1068                 if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
1069                         struct bio *rbi, *rbi2;
1070                         PRINTK("Return read for disc %d\n", i);
1071                         spin_lock_irq(&conf->device_lock);
1072                         rbi = dev->toread;
1073                         dev->toread = NULL;
1074                         if (test_and_clear_bit(R5_Overlap, &dev->flags))
1075                                 wake_up(&conf->wait_for_overlap);
1076                         spin_unlock_irq(&conf->device_lock);
1077                         while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
1078                                 copy_data(0, rbi, dev->page, dev->sector);
1079                                 rbi2 = r5_next_bio(rbi, dev->sector);
1080                                 spin_lock_irq(&conf->device_lock);
1081                                 if (--rbi->bi_phys_segments == 0) {
1082                                         rbi->bi_next = return_bi;
1083                                         return_bi = rbi;
1084                                 }
1085                                 spin_unlock_irq(&conf->device_lock);
1086                                 rbi = rbi2;
1087                         }
1088                 }
1089
1090                 /* now count some things */
1091                 if (test_bit(R5_LOCKED, &dev->flags)) locked++;
1092                 if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
1093
1094
1095                 if (dev->toread) to_read++;
1096                 if (dev->towrite) {
1097                         to_write++;
1098                         if (!test_bit(R5_OVERWRITE, &dev->flags))
1099                                 non_overwrite++;
1100                 }
1101                 if (dev->written) written++;
1102                 rdev = rcu_dereference(conf->disks[i].rdev);
1103                 if (!rdev || !test_bit(In_sync, &rdev->flags)) {
1104                         /* The ReadError flag will just be confusing now */
1105                         clear_bit(R5_ReadError, &dev->flags);
1106                         clear_bit(R5_ReWrite, &dev->flags);
1107                 }
1108                 if (!rdev || !test_bit(In_sync, &rdev->flags)
1109                     || test_bit(R5_ReadError, &dev->flags)) {
1110                         if ( failed < 2 )
1111                                 failed_num[failed] = i;
1112                         failed++;
1113                 } else
1114                         set_bit(R5_Insync, &dev->flags);
1115         }
1116         rcu_read_unlock();
1117         PRINTK("locked=%d uptodate=%d to_read=%d"
1118                " to_write=%d failed=%d failed_num=%d,%d\n",
1119                locked, uptodate, to_read, to_write, failed,
1120                failed_num[0], failed_num[1]);
1121         /* check if the array has lost >2 devices and, if so, some requests might
1122          * need to be failed
1123          */
1124         if (failed > 2 && to_read+to_write+written) {
1125                 for (i=disks; i--; ) {
1126                         int bitmap_end = 0;
1127
1128                         if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
1129                                 mdk_rdev_t *rdev;
1130                                 rcu_read_lock();
1131                                 rdev = rcu_dereference(conf->disks[i].rdev);
1132                                 if (rdev && test_bit(In_sync, &rdev->flags))
1133                                         /* multiple read failures in one stripe */
1134                                         md_error(conf->mddev, rdev);
1135                                 rcu_read_unlock();
1136                         }
1137
1138                         spin_lock_irq(&conf->device_lock);
1139                         /* fail all writes first */
1140                         bi = sh->dev[i].towrite;
1141                         sh->dev[i].towrite = NULL;
1142                         if (bi) { to_write--; bitmap_end = 1; }
1143
1144                         if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1145                                 wake_up(&conf->wait_for_overlap);
1146
1147                         while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
1148                                 struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
1149                                 clear_bit(BIO_UPTODATE, &bi->bi_flags);
1150                                 if (--bi->bi_phys_segments == 0) {
1151                                         md_write_end(conf->mddev);
1152                                         bi->bi_next = return_bi;
1153                                         return_bi = bi;
1154                                 }
1155                                 bi = nextbi;
1156                         }
1157                         /* and fail all 'written' */
1158                         bi = sh->dev[i].written;
1159                         sh->dev[i].written = NULL;
1160                         if (bi) bitmap_end = 1;
1161                         while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS) {
1162                                 struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
1163                                 clear_bit(BIO_UPTODATE, &bi->bi_flags);
1164                                 if (--bi->bi_phys_segments == 0) {
1165                                         md_write_end(conf->mddev);
1166                                         bi->bi_next = return_bi;
1167                                         return_bi = bi;
1168                                 }
1169                                 bi = bi2;
1170                         }
1171
1172                         /* fail any reads if this device is non-operational */
1173                         if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
1174                             test_bit(R5_ReadError, &sh->dev[i].flags)) {
1175                                 bi = sh->dev[i].toread;
1176                                 sh->dev[i].toread = NULL;
1177                                 if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
1178                                         wake_up(&conf->wait_for_overlap);
1179                                 if (bi) to_read--;
1180                                 while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
1181                                         struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
1182                                         clear_bit(BIO_UPTODATE, &bi->bi_flags);
1183                                         if (--bi->bi_phys_segments == 0) {
1184                                                 bi->bi_next = return_bi;
1185                                                 return_bi = bi;
1186                                         }
1187                                         bi = nextbi;
1188                                 }
1189                         }
1190                         spin_unlock_irq(&conf->device_lock);
1191                         if (bitmap_end)
1192                                 bitmap_endwrite(conf->mddev->bitmap, sh->sector,
1193                                                 STRIPE_SECTORS, 0, 0);
1194                 }
1195         }
1196         if (failed > 2 && syncing) {
1197                 md_done_sync(conf->mddev, STRIPE_SECTORS,0);
1198                 clear_bit(STRIPE_SYNCING, &sh->state);
1199                 syncing = 0;
1200         }
1201
1202         /*
1203          * might be able to return some write requests if the parity blocks
1204          * are safe, or on a failed drive
1205          */
1206         pdev = &sh->dev[pd_idx];
1207         p_failed = (failed >= 1 && failed_num[0] == pd_idx)
1208                 || (failed >= 2 && failed_num[1] == pd_idx);
1209         qdev = &sh->dev[qd_idx];
1210         q_failed = (failed >= 1 && failed_num[0] == qd_idx)
1211                 || (failed >= 2 && failed_num[1] == qd_idx);
1212
1213         if ( written &&
1214              ( p_failed || ((test_bit(R5_Insync, &pdev->flags)
1215                              && !test_bit(R5_LOCKED, &pdev->flags)
1216                              && test_bit(R5_UPTODATE, &pdev->flags))) ) &&
1217              ( q_failed || ((test_bit(R5_Insync, &qdev->flags)
1218                              && !test_bit(R5_LOCKED, &qdev->flags)
1219                              && test_bit(R5_UPTODATE, &qdev->flags))) ) ) {
1220                 /* any written block on an uptodate or failed drive can be
1221                  * returned.  Note that if we 'wrote' to a failed drive,
1222                  * it will be UPTODATE, but never LOCKED, so we don't need
1223                  * to test 'failed' directly.
1224                  */
1225                 for (i=disks; i--; )
1226                         if (sh->dev[i].written) {
1227                                 dev = &sh->dev[i];
1228                                 if (!test_bit(R5_LOCKED, &dev->flags) &&
1229                                     test_bit(R5_UPTODATE, &dev->flags) ) {
1230                                         /* We can return any write requests */
1231                                         int bitmap_end = 0;
1232                                         struct bio *wbi, *wbi2;
1233                                         PRINTK("Return write for stripe %llu disc %d\n",
1234                                                (unsigned long long)sh->sector, i);
1235                                         spin_lock_irq(&conf->device_lock);
1236                                         wbi = dev->written;
1237                                         dev->written = NULL;
1238                                         while (wbi && wbi->bi_sector < dev->sector + STRIPE_SECTORS) {
1239                                                 wbi2 = r5_next_bio(wbi, dev->sector);
1240                                                 if (--wbi->bi_phys_segments == 0) {
1241                                                         md_write_end(conf->mddev);
1242                                                         wbi->bi_next = return_bi;
1243                                                         return_bi = wbi;
1244                                                 }
1245                                                 wbi = wbi2;
1246                                         }
1247                                         if (dev->towrite == NULL)
1248                                                 bitmap_end = 1;
1249                                         spin_unlock_irq(&conf->device_lock);
1250                                         if (bitmap_end)
1251                                                 bitmap_endwrite(conf->mddev->bitmap, sh->sector,
1252                                                                 STRIPE_SECTORS,
1253                                                                 !test_bit(STRIPE_DEGRADED, &sh->state), 0);
1254                                 }
1255                         }
1256         }
1257
1258         /* Now we might consider reading some blocks, either to check/generate
1259          * parity, or to satisfy requests
1260          * or to load a block that is being partially written.
1261          */
1262         if (to_read || non_overwrite || (to_write && failed) || (syncing && (uptodate < disks))) {
1263                 for (i=disks; i--;) {
1264                         dev = &sh->dev[i];
1265                         if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
1266                             (dev->toread ||
1267                              (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
1268                              syncing ||
1269                              (failed >= 1 && (sh->dev[failed_num[0]].toread || to_write)) ||
1270                              (failed >= 2 && (sh->dev[failed_num[1]].toread || to_write))
1271                                     )
1272                                 ) {
1273                                 /* we would like to get this block, possibly
1274                                  * by computing it, but we might not be able to
1275                                  */
1276                                 if (uptodate == disks-1) {
1277                                         PRINTK("Computing stripe %llu block %d\n",
1278                                                (unsigned long long)sh->sector, i);
1279                                         compute_block_1(sh, i, 0);
1280                                         uptodate++;
1281                                 } else if ( uptodate == disks-2 && failed >= 2 ) {
1282                                         /* Computing 2-failure is *very* expensive; only do it if failed >= 2 */
1283                                         int other;
1284                                         for (other=disks; other--;) {
1285                                                 if ( other == i )
1286                                                         continue;
1287                                                 if ( !test_bit(R5_UPTODATE, &sh->dev[other].flags) )
1288                                                         break;
1289                                         }
1290                                         BUG_ON(other < 0);
1291                                         PRINTK("Computing stripe %llu blocks %d,%d\n",
1292                                                (unsigned long long)sh->sector, i, other);
1293                                         compute_block_2(sh, i, other);
1294                                         uptodate += 2;
1295                                 } else if (test_bit(R5_Insync, &dev->flags)) {
1296                                         set_bit(R5_LOCKED, &dev->flags);
1297                                         set_bit(R5_Wantread, &dev->flags);
1298 #if 0
1299                                         /* if I am just reading this block and we don't have
1300                                            a failed drive, or any pending writes then sidestep the cache */
1301                                         if (sh->bh_read[i] && !sh->bh_read[i]->b_reqnext &&
1302                                             ! syncing && !failed && !to_write) {
1303                                                 sh->bh_cache[i]->b_page =  sh->bh_read[i]->b_page;
1304                                                 sh->bh_cache[i]->b_data =  sh->bh_read[i]->b_data;
1305                                         }
1306 #endif
1307                                         locked++;
1308                                         PRINTK("Reading block %d (sync=%d)\n",
1309                                                 i, syncing);
1310                                 }
1311                         }
1312                 }
1313                 set_bit(STRIPE_HANDLE, &sh->state);
1314         }
1315
1316         /* now to consider writing and what else, if anything should be read */
1317         if (to_write) {
1318                 int rcw=0, must_compute=0;
1319                 for (i=disks ; i--;) {
1320                         dev = &sh->dev[i];
1321                         /* Would I have to read this buffer for reconstruct_write */
1322                         if (!test_bit(R5_OVERWRITE, &dev->flags)
1323                             && i != pd_idx && i != qd_idx
1324                             && (!test_bit(R5_LOCKED, &dev->flags)
1325 #if 0
1326                                 || sh->bh_page[i] != bh->b_page
1327 #endif
1328                                     ) &&
1329                             !test_bit(R5_UPTODATE, &dev->flags)) {
1330                                 if (test_bit(R5_Insync, &dev->flags)) rcw++;
1331                                 else {
1332                                         PRINTK("raid6: must_compute: disk %d flags=%#lx\n", i, dev->flags);
1333                                         must_compute++;
1334                                 }
1335                         }
1336                 }
1337                 PRINTK("for sector %llu, rcw=%d, must_compute=%d\n",
1338                        (unsigned long long)sh->sector, rcw, must_compute);
1339                 set_bit(STRIPE_HANDLE, &sh->state);
1340
1341                 if (rcw > 0)
1342                         /* want reconstruct write, but need to get some data */
1343                         for (i=disks; i--;) {
1344                                 dev = &sh->dev[i];
1345                                 if (!test_bit(R5_OVERWRITE, &dev->flags)
1346                                     && !(failed == 0 && (i == pd_idx || i == qd_idx))
1347                                     && !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
1348                                     test_bit(R5_Insync, &dev->flags)) {
1349                                         if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
1350                                         {
1351                                                 PRINTK("Read_old stripe %llu block %d for Reconstruct\n",
1352                                                        (unsigned long long)sh->sector, i);
1353                                                 set_bit(R5_LOCKED, &dev->flags);
1354                                                 set_bit(R5_Wantread, &dev->flags);
1355                                                 locked++;
1356                                         } else {
1357                                                 PRINTK("Request delayed stripe %llu block %d for Reconstruct\n",
1358                                                        (unsigned long long)sh->sector, i);
1359                                                 set_bit(STRIPE_DELAYED, &sh->state);
1360                                                 set_bit(STRIPE_HANDLE, &sh->state);
1361                                         }
1362                                 }
1363                         }
1364                 /* now if nothing is locked, and if we have enough data, we can start a write request */
1365                 if (locked == 0 && rcw == 0 &&
1366                     !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
1367                         if ( must_compute > 0 ) {
1368                                 /* We have failed blocks and need to compute them */
1369                                 switch ( failed ) {
1370                                 case 0: BUG();
1371                                 case 1: compute_block_1(sh, failed_num[0], 0); break;
1372                                 case 2: compute_block_2(sh, failed_num[0], failed_num[1]); break;
1373                                 default: BUG(); /* This request should have been failed? */
1374                                 }
1375                         }
1376
1377                         PRINTK("Computing parity for stripe %llu\n", (unsigned long long)sh->sector);
1378                         compute_parity(sh, RECONSTRUCT_WRITE);
1379                         /* now every locked buffer is ready to be written */
1380                         for (i=disks; i--;)
1381                                 if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
1382                                         PRINTK("Writing stripe %llu block %d\n",
1383                                                (unsigned long long)sh->sector, i);
1384                                         locked++;
1385                                         set_bit(R5_Wantwrite, &sh->dev[i].flags);
1386                                 }
1387                         /* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
1388                         set_bit(STRIPE_INSYNC, &sh->state);
1389
1390                         if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
1391                                 atomic_dec(&conf->preread_active_stripes);
1392                                 if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
1393                                         md_wakeup_thread(conf->mddev->thread);
1394                         }
1395                 }
1396         }
1397
1398         /* maybe we need to check and possibly fix the parity for this stripe
1399          * Any reads will already have been scheduled, so we just see if enough data
1400          * is available
1401          */
1402         if (syncing && locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state)) {
1403                 int update_p = 0, update_q = 0;
1404                 struct r5dev *dev;
1405
1406                 set_bit(STRIPE_HANDLE, &sh->state);
1407
1408                 BUG_ON(failed>2);
1409                 BUG_ON(uptodate < disks);
1410                 /* Want to check and possibly repair P and Q.
1411                  * However there could be one 'failed' device, in which
1412                  * case we can only check one of them, possibly using the
1413                  * other to generate missing data
1414                  */
1415
1416                 /* If !tmp_page, we cannot do the calculations,
1417                  * but as we have set STRIPE_HANDLE, we will soon be called
1418                  * by stripe_handle with a tmp_page - just wait until then.
1419                  */
1420                 if (tmp_page) {
1421                         if (failed == q_failed) {
1422                                 /* The only possible failed device holds 'Q', so it makes
1423                                  * sense to check P (If anything else were failed, we would
1424                                  * have used P to recreate it).
1425                                  */
1426                                 compute_block_1(sh, pd_idx, 1);
1427                                 if (!page_is_zero(sh->dev[pd_idx].page)) {
1428                                         compute_block_1(sh,pd_idx,0);
1429                                         update_p = 1;
1430                                 }
1431                         }
1432                         if (!q_failed && failed < 2) {
1433                                 /* q is not failed, and we didn't use it to generate
1434                                  * anything, so it makes sense to check it
1435                                  */
1436                                 memcpy(page_address(tmp_page),
1437                                        page_address(sh->dev[qd_idx].page),
1438                                        STRIPE_SIZE);
1439                                 compute_parity(sh, UPDATE_PARITY);
1440                                 if (memcmp(page_address(tmp_page),
1441                                            page_address(sh->dev[qd_idx].page),
1442                                            STRIPE_SIZE)!= 0) {
1443                                         clear_bit(STRIPE_INSYNC, &sh->state);
1444                                         update_q = 1;
1445                                 }
1446                         }
1447                         if (update_p || update_q) {
1448                                 conf->mddev->resync_mismatches += STRIPE_SECTORS;
1449                                 if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
1450                                         /* don't try to repair!! */
1451                                         update_p = update_q = 0;
1452                         }
1453
1454                         /* now write out any block on a failed drive,
1455                          * or P or Q if they need it
1456                          */
1457
1458                         if (failed == 2) {
1459                                 dev = &sh->dev[failed_num[1]];
1460                                 locked++;
1461                                 set_bit(R5_LOCKED, &dev->flags);
1462                                 set_bit(R5_Wantwrite, &dev->flags);
1463                         }
1464                         if (failed >= 1) {
1465                                 dev = &sh->dev[failed_num[0]];
1466                                 locked++;
1467                                 set_bit(R5_LOCKED, &dev->flags);
1468                                 set_bit(R5_Wantwrite, &dev->flags);
1469                         }
1470
1471                         if (update_p) {
1472                                 dev = &sh->dev[pd_idx];
1473                                 locked ++;
1474                                 set_bit(R5_LOCKED, &dev->flags);
1475                                 set_bit(R5_Wantwrite, &dev->flags);
1476                         }
1477                         if (update_q) {
1478                                 dev = &sh->dev[qd_idx];
1479                                 locked++;
1480                                 set_bit(R5_LOCKED, &dev->flags);
1481                                 set_bit(R5_Wantwrite, &dev->flags);
1482                         }
1483                         clear_bit(STRIPE_DEGRADED, &sh->state);
1484
1485                         set_bit(STRIPE_INSYNC, &sh->state);
1486                 }
1487         }
1488
1489         if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
1490                 md_done_sync(conf->mddev, STRIPE_SECTORS,1);
1491                 clear_bit(STRIPE_SYNCING, &sh->state);
1492         }
1493
1494         /* If the failed drives are just a ReadError, then we might need
1495          * to progress the repair/check process
1496          */
1497         if (failed <= 2 && ! conf->mddev->ro)
1498                 for (i=0; i<failed;i++) {
1499                         dev = &sh->dev[failed_num[i]];
1500                         if (test_bit(R5_ReadError, &dev->flags)
1501                             && !test_bit(R5_LOCKED, &dev->flags)
1502                             && test_bit(R5_UPTODATE, &dev->flags)
1503                                 ) {
1504                                 if (!test_bit(R5_ReWrite, &dev->flags)) {
1505                                         set_bit(R5_Wantwrite, &dev->flags);
1506                                         set_bit(R5_ReWrite, &dev->flags);
1507                                         set_bit(R5_LOCKED, &dev->flags);
1508                                 } else {
1509                                         /* let's read it back */
1510                                         set_bit(R5_Wantread, &dev->flags);
1511                                         set_bit(R5_LOCKED, &dev->flags);
1512                                 }
1513                         }
1514                 }
1515         spin_unlock(&sh->lock);
1516
1517         while ((bi=return_bi)) {
1518                 int bytes = bi->bi_size;
1519
1520                 return_bi = bi->bi_next;
1521                 bi->bi_next = NULL;
1522                 bi->bi_size = 0;
1523                 bi->bi_end_io(bi, bytes, 0);
1524         }
1525         for (i=disks; i-- ;) {
1526                 int rw;
1527                 struct bio *bi;
1528                 mdk_rdev_t *rdev;
1529                 if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
1530                         rw = 1;
1531                 else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
1532                         rw = 0;
1533                 else
1534                         continue;
1535
1536                 bi = &sh->dev[i].req;
1537
1538                 bi->bi_rw = rw;
1539                 if (rw)
1540                         bi->bi_end_io = raid6_end_write_request;
1541                 else
1542                         bi->bi_end_io = raid6_end_read_request;
1543
1544                 rcu_read_lock();
1545                 rdev = rcu_dereference(conf->disks[i].rdev);
1546                 if (rdev && test_bit(Faulty, &rdev->flags))
1547                         rdev = NULL;
1548                 if (rdev)
1549                         atomic_inc(&rdev->nr_pending);
1550                 rcu_read_unlock();
1551
1552                 if (rdev) {
1553                         if (syncing)
1554                                 md_sync_acct(rdev->bdev, STRIPE_SECTORS);
1555
1556                         bi->bi_bdev = rdev->bdev;
1557                         PRINTK("for %llu schedule op %ld on disc %d\n",
1558                                 (unsigned long long)sh->sector, bi->bi_rw, i);
1559                         atomic_inc(&sh->count);
1560                         bi->bi_sector = sh->sector + rdev->data_offset;
1561                         bi->bi_flags = 1 << BIO_UPTODATE;
1562                         bi->bi_vcnt = 1;
1563                         bi->bi_max_vecs = 1;
1564                         bi->bi_idx = 0;
1565                         bi->bi_io_vec = &sh->dev[i].vec;
1566                         bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
1567                         bi->bi_io_vec[0].bv_offset = 0;
1568                         bi->bi_size = STRIPE_SIZE;
1569                         bi->bi_next = NULL;
1570                         if (rw == WRITE &&
1571                             test_bit(R5_ReWrite, &sh->dev[i].flags))
1572                                 atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
1573                         generic_make_request(bi);
1574                 } else {
1575                         if (rw == 1)
1576                                 set_bit(STRIPE_DEGRADED, &sh->state);
1577                         PRINTK("skip op %ld on disc %d for sector %llu\n",
1578                                 bi->bi_rw, i, (unsigned long long)sh->sector);
1579                         clear_bit(R5_LOCKED, &sh->dev[i].flags);
1580                         set_bit(STRIPE_HANDLE, &sh->state);
1581                 }
1582         }
1583 }
1584
1585 static void raid6_activate_delayed(raid6_conf_t *conf)
1586 {
1587         if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
1588                 while (!list_empty(&conf->delayed_list)) {
1589                         struct list_head *l = conf->delayed_list.next;
1590                         struct stripe_head *sh;
1591                         sh = list_entry(l, struct stripe_head, lru);
1592                         list_del_init(l);
1593                         clear_bit(STRIPE_DELAYED, &sh->state);
1594                         if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
1595                                 atomic_inc(&conf->preread_active_stripes);
1596                         list_add_tail(&sh->lru, &conf->handle_list);
1597                 }
1598         }
1599 }
1600
1601 static void activate_bit_delay(raid6_conf_t *conf)
1602 {
1603         /* device_lock is held */
1604         struct list_head head;
1605         list_add(&head, &conf->bitmap_list);
1606         list_del_init(&conf->bitmap_list);
1607         while (!list_empty(&head)) {
1608                 struct stripe_head *sh = list_entry(head.next, struct stripe_head, lru);
1609                 list_del_init(&sh->lru);
1610                 atomic_inc(&sh->count);
1611                 __release_stripe(conf, sh);
1612         }
1613 }
1614
1615 static void unplug_slaves(mddev_t *mddev)
1616 {
1617         raid6_conf_t *conf = mddev_to_conf(mddev);
1618         int i;
1619
1620         rcu_read_lock();
1621         for (i=0; i<mddev->raid_disks; i++) {
1622                 mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
1623                 if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
1624                         request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
1625
1626                         atomic_inc(&rdev->nr_pending);
1627                         rcu_read_unlock();
1628
1629                         if (r_queue->unplug_fn)
1630                                 r_queue->unplug_fn(r_queue);
1631
1632                         rdev_dec_pending(rdev, mddev);
1633                         rcu_read_lock();
1634                 }
1635         }
1636         rcu_read_unlock();
1637 }
1638
1639 static void raid6_unplug_device(request_queue_t *q)
1640 {
1641         mddev_t *mddev = q->queuedata;
1642         raid6_conf_t *conf = mddev_to_conf(mddev);
1643         unsigned long flags;
1644
1645         spin_lock_irqsave(&conf->device_lock, flags);
1646
1647         if (blk_remove_plug(q)) {
1648                 conf->seq_flush++;
1649                 raid6_activate_delayed(conf);
1650         }
1651         md_wakeup_thread(mddev->thread);
1652
1653         spin_unlock_irqrestore(&conf->device_lock, flags);
1654
1655         unplug_slaves(mddev);
1656 }
1657
1658 static int raid6_issue_flush(request_queue_t *q, struct gendisk *disk,
1659                              sector_t *error_sector)
1660 {
1661         mddev_t *mddev = q->queuedata;
1662         raid6_conf_t *conf = mddev_to_conf(mddev);
1663         int i, ret = 0;
1664
1665         rcu_read_lock();
1666         for (i=0; i<mddev->raid_disks && ret == 0; i++) {
1667                 mdk_rdev_t *rdev = rcu_dereference(conf->disks[i].rdev);
1668                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
1669                         struct block_device *bdev = rdev->bdev;
1670                         request_queue_t *r_queue = bdev_get_queue(bdev);
1671
1672                         if (!r_queue->issue_flush_fn)
1673                                 ret = -EOPNOTSUPP;
1674                         else {
1675                                 atomic_inc(&rdev->nr_pending);
1676                                 rcu_read_unlock();
1677                                 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
1678                                                               error_sector);
1679                                 rdev_dec_pending(rdev, mddev);
1680                                 rcu_read_lock();
1681                         }
1682                 }
1683         }
1684         rcu_read_unlock();
1685         return ret;
1686 }
1687
1688 static inline void raid6_plug_device(raid6_conf_t *conf)
1689 {
1690         spin_lock_irq(&conf->device_lock);
1691         blk_plug_device(conf->mddev->queue);
1692         spin_unlock_irq(&conf->device_lock);
1693 }
1694
1695 static int make_request (request_queue_t *q, struct bio * bi)
1696 {
1697         mddev_t *mddev = q->queuedata;
1698         raid6_conf_t *conf = mddev_to_conf(mddev);
1699         const unsigned int raid_disks = conf->raid_disks;
1700         const unsigned int data_disks = raid_disks - 2;
1701         unsigned int dd_idx, pd_idx;
1702         sector_t new_sector;
1703         sector_t logical_sector, last_sector;
1704         struct stripe_head *sh;
1705         const int rw = bio_data_dir(bi);
1706
1707         if (unlikely(bio_barrier(bi))) {
1708                 bio_endio(bi, bi->bi_size, -EOPNOTSUPP);
1709                 return 0;
1710         }
1711
1712         md_write_start(mddev, bi);
1713
1714         disk_stat_inc(mddev->gendisk, ios[rw]);
1715         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bi));
1716
1717         logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
1718         last_sector = bi->bi_sector + (bi->bi_size>>9);
1719
1720         bi->bi_next = NULL;
1721         bi->bi_phys_segments = 1;       /* over-loaded to count active stripes */
1722
1723         for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
1724                 DEFINE_WAIT(w);
1725
1726                 new_sector = raid6_compute_sector(logical_sector,
1727                                                   raid_disks, data_disks, &dd_idx, &pd_idx, conf);
1728
1729                 PRINTK("raid6: make_request, sector %llu logical %llu\n",
1730                        (unsigned long long)new_sector,
1731                        (unsigned long long)logical_sector);
1732
1733         retry:
1734                 prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
1735                 sh = get_active_stripe(conf, new_sector, pd_idx, (bi->bi_rw&RWA_MASK));
1736                 if (sh) {
1737                         if (!add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK))) {
1738                                 /* Add failed due to overlap.  Flush everything
1739                                  * and wait a while
1740                                  */
1741                                 raid6_unplug_device(mddev->queue);
1742                                 release_stripe(sh);
1743                                 schedule();
1744                                 goto retry;
1745                         }
1746                         finish_wait(&conf->wait_for_overlap, &w);
1747                         raid6_plug_device(conf);
1748                         handle_stripe(sh, NULL);
1749                         release_stripe(sh);
1750                 } else {
1751                         /* cannot get stripe for read-ahead, just give-up */
1752                         clear_bit(BIO_UPTODATE, &bi->bi_flags);
1753                         finish_wait(&conf->wait_for_overlap, &w);
1754                         break;
1755                 }
1756
1757         }
1758         spin_lock_irq(&conf->device_lock);
1759         if (--bi->bi_phys_segments == 0) {
1760                 int bytes = bi->bi_size;
1761
1762                 if (rw == WRITE )
1763                         md_write_end(mddev);
1764                 bi->bi_size = 0;
1765                 bi->bi_end_io(bi, bytes, 0);
1766         }
1767         spin_unlock_irq(&conf->device_lock);
1768         return 0;
1769 }
1770
1771 /* FIXME go_faster isn't used */
1772 static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
1773 {
1774         raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
1775         struct stripe_head *sh;
1776         int sectors_per_chunk = conf->chunk_size >> 9;
1777         sector_t x;
1778         unsigned long stripe;
1779         int chunk_offset;
1780         int dd_idx, pd_idx;
1781         sector_t first_sector;
1782         int raid_disks = conf->raid_disks;
1783         int data_disks = raid_disks - 2;
1784         sector_t max_sector = mddev->size << 1;
1785         int sync_blocks;
1786         int still_degraded = 0;
1787         int i;
1788
1789         if (sector_nr >= max_sector) {
1790                 /* just being told to finish up .. nothing much to do */
1791                 unplug_slaves(mddev);
1792
1793                 if (mddev->curr_resync < max_sector) /* aborted */
1794                         bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
1795                                         &sync_blocks, 1);
1796                 else /* completed sync */
1797                         conf->fullsync = 0;
1798                 bitmap_close_sync(mddev->bitmap);
1799
1800                 return 0;
1801         }
1802         /* if there are 2 or more failed drives and we are trying
1803          * to resync, then assert that we are finished, because there is
1804          * nothing we can do.
1805          */
1806         if (mddev->degraded >= 2 && test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
1807                 sector_t rv = (mddev->size << 1) - sector_nr;
1808                 *skipped = 1;
1809                 return rv;
1810         }
1811         if (!bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, 1) &&
1812             !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
1813             !conf->fullsync && sync_blocks >= STRIPE_SECTORS) {
1814                 /* we can skip this block, and probably more */
1815                 sync_blocks /= STRIPE_SECTORS;
1816                 *skipped = 1;
1817                 return sync_blocks * STRIPE_SECTORS; /* keep things rounded to whole stripes */
1818         }
1819
1820         x = sector_nr;
1821         chunk_offset = sector_div(x, sectors_per_chunk);
1822         stripe = x;
1823         BUG_ON(x != stripe);
1824
1825         first_sector = raid6_compute_sector((sector_t)stripe*data_disks*sectors_per_chunk
1826                 + chunk_offset, raid_disks, data_disks, &dd_idx, &pd_idx, conf);
1827         sh = get_active_stripe(conf, sector_nr, pd_idx, 1);
1828         if (sh == NULL) {
1829                 sh = get_active_stripe(conf, sector_nr, pd_idx, 0);
1830                 /* make sure we don't swamp the stripe cache if someone else
1831                  * is trying to get access
1832                  */
1833                 schedule_timeout_uninterruptible(1);
1834         }
1835         /* Need to check if array will still be degraded after recovery/resync
1836          * We don't need to check the 'failed' flag as when that gets set,
1837          * recovery aborts.
1838          */
1839         for (i=0; i<mddev->raid_disks; i++)
1840                 if (conf->disks[i].rdev == NULL)
1841                         still_degraded = 1;
1842
1843         bitmap_start_sync(mddev->bitmap, sector_nr, &sync_blocks, still_degraded);
1844
1845         spin_lock(&sh->lock);
1846         set_bit(STRIPE_SYNCING, &sh->state);
1847         clear_bit(STRIPE_INSYNC, &sh->state);
1848         spin_unlock(&sh->lock);
1849
1850         handle_stripe(sh, NULL);
1851         release_stripe(sh);
1852
1853         return STRIPE_SECTORS;
1854 }
1855
1856 /*
1857  * This is our raid6 kernel thread.
1858  *
1859  * We scan the hash table for stripes which can be handled now.
1860  * During the scan, completed stripes are saved for us by the interrupt
1861  * handler, so that they will not have to wait for our next wakeup.
1862  */
1863 static void raid6d (mddev_t *mddev)
1864 {
1865         struct stripe_head *sh;
1866         raid6_conf_t *conf = mddev_to_conf(mddev);
1867         int handled;
1868
1869         PRINTK("+++ raid6d active\n");
1870
1871         md_check_recovery(mddev);
1872
1873         handled = 0;
1874         spin_lock_irq(&conf->device_lock);
1875         while (1) {
1876                 struct list_head *first;
1877
1878                 if (conf->seq_flush - conf->seq_write > 0) {
1879                         int seq = conf->seq_flush;
1880                         spin_unlock_irq(&conf->device_lock);
1881                         bitmap_unplug(mddev->bitmap);
1882                         spin_lock_irq(&conf->device_lock);
1883                         conf->seq_write = seq;
1884                         activate_bit_delay(conf);
1885                 }
1886
1887                 if (list_empty(&conf->handle_list) &&
1888                     atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD &&
1889                     !blk_queue_plugged(mddev->queue) &&
1890                     !list_empty(&conf->delayed_list))
1891                         raid6_activate_delayed(conf);
1892
1893                 if (list_empty(&conf->handle_list))
1894                         break;
1895
1896                 first = conf->handle_list.next;
1897                 sh = list_entry(first, struct stripe_head, lru);
1898
1899                 list_del_init(first);
1900                 atomic_inc(&sh->count);
1901                 BUG_ON(atomic_read(&sh->count)!= 1);
1902                 spin_unlock_irq(&conf->device_lock);
1903
1904                 handled++;
1905                 handle_stripe(sh, conf->spare_page);
1906                 release_stripe(sh);
1907
1908                 spin_lock_irq(&conf->device_lock);
1909         }
1910         PRINTK("%d stripes handled\n", handled);
1911
1912         spin_unlock_irq(&conf->device_lock);
1913
1914         unplug_slaves(mddev);
1915
1916         PRINTK("--- raid6d inactive\n");
1917 }
1918
1919 static ssize_t
1920 raid6_show_stripe_cache_size(mddev_t *mddev, char *page)
1921 {
1922         raid6_conf_t *conf = mddev_to_conf(mddev);
1923         if (conf)
1924                 return sprintf(page, "%d\n", conf->max_nr_stripes);
1925         else
1926                 return 0;
1927 }
1928
1929 static ssize_t
1930 raid6_store_stripe_cache_size(mddev_t *mddev, const char *page, size_t len)
1931 {
1932         raid6_conf_t *conf = mddev_to_conf(mddev);
1933         char *end;
1934         int new;
1935         if (len >= PAGE_SIZE)
1936                 return -EINVAL;
1937         if (!conf)
1938                 return -ENODEV;
1939
1940         new = simple_strtoul(page, &end, 10);
1941         if (!*page || (*end && *end != '\n') )
1942                 return -EINVAL;
1943         if (new <= 16 || new > 32768)
1944                 return -EINVAL;
1945         while (new < conf->max_nr_stripes) {
1946                 if (drop_one_stripe(conf))
1947                         conf->max_nr_stripes--;
1948                 else
1949                         break;
1950         }
1951         while (new > conf->max_nr_stripes) {
1952                 if (grow_one_stripe(conf))
1953                         conf->max_nr_stripes++;
1954                 else break;
1955         }
1956         return len;
1957 }
1958
1959 static struct md_sysfs_entry
1960 raid6_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR,
1961                                 raid6_show_stripe_cache_size,
1962                                 raid6_store_stripe_cache_size);
1963
1964 static ssize_t
1965 stripe_cache_active_show(mddev_t *mddev, char *page)
1966 {
1967         raid6_conf_t *conf = mddev_to_conf(mddev);
1968         if (conf)
1969                 return sprintf(page, "%d\n", atomic_read(&conf->active_stripes));
1970         else
1971                 return 0;
1972 }
1973
1974 static struct md_sysfs_entry
1975 raid6_stripecache_active = __ATTR_RO(stripe_cache_active);
1976
1977 static struct attribute *raid6_attrs[] =  {
1978         &raid6_stripecache_size.attr,
1979         &raid6_stripecache_active.attr,
1980         NULL,
1981 };
1982 static struct attribute_group raid6_attrs_group = {
1983         .name = NULL,
1984         .attrs = raid6_attrs,
1985 };
1986
1987 static int run(mddev_t *mddev)
1988 {
1989         raid6_conf_t *conf;
1990         int raid_disk, memory;
1991         mdk_rdev_t *rdev;
1992         struct disk_info *disk;
1993         struct list_head *tmp;
1994
1995         if (mddev->level != 6) {
1996                 PRINTK("raid6: %s: raid level not set to 6 (%d)\n", mdname(mddev), mddev->level);
1997                 return -EIO;
1998         }
1999
2000         mddev->private = kzalloc(sizeof (raid6_conf_t), GFP_KERNEL);
2001         if ((conf = mddev->private) == NULL)
2002                 goto abort;
2003         conf->disks = kzalloc(mddev->raid_disks * sizeof(struct disk_info),
2004                                  GFP_KERNEL);
2005         if (!conf->disks)
2006                 goto abort;
2007
2008         conf->mddev = mddev;
2009
2010         if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
2011                 goto abort;
2012
2013         conf->spare_page = alloc_page(GFP_KERNEL);
2014         if (!conf->spare_page)
2015                 goto abort;
2016
2017         spin_lock_init(&conf->device_lock);
2018         init_waitqueue_head(&conf->wait_for_stripe);
2019         init_waitqueue_head(&conf->wait_for_overlap);
2020         INIT_LIST_HEAD(&conf->handle_list);
2021         INIT_LIST_HEAD(&conf->delayed_list);
2022         INIT_LIST_HEAD(&conf->bitmap_list);
2023         INIT_LIST_HEAD(&conf->inactive_list);
2024         atomic_set(&conf->active_stripes, 0);
2025         atomic_set(&conf->preread_active_stripes, 0);
2026
2027         PRINTK("raid6: run(%s) called.\n", mdname(mddev));
2028
2029         ITERATE_RDEV(mddev,rdev,tmp) {
2030                 raid_disk = rdev->raid_disk;
2031                 if (raid_disk >= mddev->raid_disks
2032                     || raid_disk < 0)
2033                         continue;
2034                 disk = conf->disks + raid_disk;
2035
2036                 disk->rdev = rdev;
2037
2038                 if (test_bit(In_sync, &rdev->flags)) {
2039                         char b[BDEVNAME_SIZE];
2040                         printk(KERN_INFO "raid6: device %s operational as raid"
2041                                " disk %d\n", bdevname(rdev->bdev,b),
2042                                raid_disk);
2043                         conf->working_disks++;
2044                 }
2045         }
2046
2047         conf->raid_disks = mddev->raid_disks;
2048
2049         /*
2050          * 0 for a fully functional array, 1 or 2 for a degraded array.
2051          */
2052         mddev->degraded = conf->failed_disks = conf->raid_disks - conf->working_disks;
2053         conf->mddev = mddev;
2054         conf->chunk_size = mddev->chunk_size;
2055         conf->level = mddev->level;
2056         conf->algorithm = mddev->layout;
2057         conf->max_nr_stripes = NR_STRIPES;
2058
2059         /* device size must be a multiple of chunk size */
2060         mddev->size &= ~(mddev->chunk_size/1024 -1);
2061         mddev->resync_max_sectors = mddev->size << 1;
2062
2063         if (conf->raid_disks < 4) {
2064                 printk(KERN_ERR "raid6: not enough configured devices for %s (%d, minimum 4)\n",
2065                        mdname(mddev), conf->raid_disks);
2066                 goto abort;
2067         }
2068         if (!conf->chunk_size || conf->chunk_size % 4) {
2069                 printk(KERN_ERR "raid6: invalid chunk size %d for %s\n",
2070                        conf->chunk_size, mdname(mddev));
2071                 goto abort;
2072         }
2073         if (conf->algorithm > ALGORITHM_RIGHT_SYMMETRIC) {
2074                 printk(KERN_ERR
2075                        "raid6: unsupported parity algorithm %d for %s\n",
2076                        conf->algorithm, mdname(mddev));
2077                 goto abort;
2078         }
2079         if (mddev->degraded > 2) {
2080                 printk(KERN_ERR "raid6: not enough operational devices for %s"
2081                        " (%d/%d failed)\n",
2082                        mdname(mddev), conf->failed_disks, conf->raid_disks);
2083                 goto abort;
2084         }
2085
2086         if (mddev->degraded > 0 &&
2087             mddev->recovery_cp != MaxSector) {
2088                 if (mddev->ok_start_degraded)
2089                         printk(KERN_WARNING "raid6: starting dirty degraded array:%s"
2090                                "- data corruption possible.\n",
2091                                mdname(mddev));
2092                 else {
2093                         printk(KERN_ERR "raid6: cannot start dirty degraded array"
2094                                " for %s\n", mdname(mddev));
2095                         goto abort;
2096                 }
2097         }
2098
2099         {
2100                 mddev->thread = md_register_thread(raid6d, mddev, "%s_raid6");
2101                 if (!mddev->thread) {
2102                         printk(KERN_ERR
2103                                "raid6: couldn't allocate thread for %s\n",
2104                                mdname(mddev));
2105                         goto abort;
2106                 }
2107         }
2108
2109         memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
2110                  conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
2111         if (grow_stripes(conf, conf->max_nr_stripes)) {
2112                 printk(KERN_ERR
2113                        "raid6: couldn't allocate %dkB for buffers\n", memory);
2114                 shrink_stripes(conf);
2115                 md_unregister_thread(mddev->thread);
2116                 goto abort;
2117         } else
2118                 printk(KERN_INFO "raid6: allocated %dkB for %s\n",
2119                        memory, mdname(mddev));
2120
2121         if (mddev->degraded == 0)
2122                 printk(KERN_INFO "raid6: raid level %d set %s active with %d out of %d"
2123                        " devices, algorithm %d\n", conf->level, mdname(mddev),
2124                        mddev->raid_disks-mddev->degraded, mddev->raid_disks,
2125                        conf->algorithm);
2126         else
2127                 printk(KERN_ALERT "raid6: raid level %d set %s active with %d"
2128                        " out of %d devices, algorithm %d\n", conf->level,
2129                        mdname(mddev), mddev->raid_disks - mddev->degraded,
2130                        mddev->raid_disks, conf->algorithm);
2131
2132         print_raid6_conf(conf);
2133
2134         /* read-ahead size must cover two whole stripes, which is
2135          * 2 * (n-2) * chunksize where 'n' is the number of raid devices
2136          */
2137         {
2138                 int stripe = (mddev->raid_disks-2) * mddev->chunk_size
2139                         / PAGE_SIZE;
2140                 if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
2141                         mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
2142         }
2143
2144         /* Ok, everything is just fine now */
2145         sysfs_create_group(&mddev->kobj, &raid6_attrs_group);
2146
2147         mddev->array_size =  mddev->size * (mddev->raid_disks - 2);
2148
2149         mddev->queue->unplug_fn = raid6_unplug_device;
2150         mddev->queue->issue_flush_fn = raid6_issue_flush;
2151         return 0;
2152 abort:
2153         if (conf) {
2154                 print_raid6_conf(conf);
2155                 safe_put_page(conf->spare_page);
2156                 kfree(conf->stripe_hashtbl);
2157                 kfree(conf->disks);
2158                 kfree(conf);
2159         }
2160         mddev->private = NULL;
2161         printk(KERN_ALERT "raid6: failed to run raid set %s\n", mdname(mddev));
2162         return -EIO;
2163 }
2164
2165
2166
2167 static int stop (mddev_t *mddev)
2168 {
2169         raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
2170
2171         md_unregister_thread(mddev->thread);
2172         mddev->thread = NULL;
2173         shrink_stripes(conf);
2174         kfree(conf->stripe_hashtbl);
2175         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
2176         sysfs_remove_group(&mddev->kobj, &raid6_attrs_group);
2177         kfree(conf);
2178         mddev->private = NULL;
2179         return 0;
2180 }
2181
2182 #if RAID6_DUMPSTATE
2183 static void print_sh (struct seq_file *seq, struct stripe_head *sh)
2184 {
2185         int i;
2186
2187         seq_printf(seq, "sh %llu, pd_idx %d, state %ld.\n",
2188                    (unsigned long long)sh->sector, sh->pd_idx, sh->state);
2189         seq_printf(seq, "sh %llu,  count %d.\n",
2190                    (unsigned long long)sh->sector, atomic_read(&sh->count));
2191         seq_printf(seq, "sh %llu, ", (unsigned long long)sh->sector);
2192         for (i = 0; i < sh->raid_conf->raid_disks; i++) {
2193                 seq_printf(seq, "(cache%d: %p %ld) ",
2194                            i, sh->dev[i].page, sh->dev[i].flags);
2195         }
2196         seq_printf(seq, "\n");
2197 }
2198
2199 static void printall (struct seq_file *seq, raid6_conf_t *conf)
2200 {
2201         struct stripe_head *sh;
2202         struct hlist_node *hn;
2203         int i;
2204
2205         spin_lock_irq(&conf->device_lock);
2206         for (i = 0; i < NR_HASH; i++) {
2207                 sh = conf->stripe_hashtbl[i];
2208                 hlist_for_each_entry(sh, hn, &conf->stripe_hashtbl[i], hash) {
2209                         if (sh->raid_conf != conf)
2210                                 continue;
2211                         print_sh(seq, sh);
2212                 }
2213         }
2214         spin_unlock_irq(&conf->device_lock);
2215 }
2216 #endif
2217
2218 static void status (struct seq_file *seq, mddev_t *mddev)
2219 {
2220         raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
2221         int i;
2222
2223         seq_printf (seq, " level %d, %dk chunk, algorithm %d", mddev->level, mddev->chunk_size >> 10, mddev->layout);
2224         seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->working_disks);
2225         for (i = 0; i < conf->raid_disks; i++)
2226                 seq_printf (seq, "%s",
2227                             conf->disks[i].rdev &&
2228                             test_bit(In_sync, &conf->disks[i].rdev->flags) ? "U" : "_");
2229         seq_printf (seq, "]");
2230 #if RAID6_DUMPSTATE
2231         seq_printf (seq, "\n");
2232         printall(seq, conf);
2233 #endif
2234 }
2235
2236 static void print_raid6_conf (raid6_conf_t *conf)
2237 {
2238         int i;
2239         struct disk_info *tmp;
2240
2241         printk("RAID6 conf printout:\n");
2242         if (!conf) {
2243                 printk("(conf==NULL)\n");
2244                 return;
2245         }
2246         printk(" --- rd:%d wd:%d fd:%d\n", conf->raid_disks,
2247                  conf->working_disks, conf->failed_disks);
2248
2249         for (i = 0; i < conf->raid_disks; i++) {
2250                 char b[BDEVNAME_SIZE];
2251                 tmp = conf->disks + i;
2252                 if (tmp->rdev)
2253                 printk(" disk %d, o:%d, dev:%s\n",
2254                         i, !test_bit(Faulty, &tmp->rdev->flags),
2255                         bdevname(tmp->rdev->bdev,b));
2256         }
2257 }
2258
2259 static int raid6_spare_active(mddev_t *mddev)
2260 {
2261         int i;
2262         raid6_conf_t *conf = mddev->private;
2263         struct disk_info *tmp;
2264
2265         for (i = 0; i < conf->raid_disks; i++) {
2266                 tmp = conf->disks + i;
2267                 if (tmp->rdev
2268                     && !test_bit(Faulty, &tmp->rdev->flags)
2269                     && !test_bit(In_sync, &tmp->rdev->flags)) {
2270                         mddev->degraded--;
2271                         conf->failed_disks--;
2272                         conf->working_disks++;
2273                         set_bit(In_sync, &tmp->rdev->flags);
2274                 }
2275         }
2276         print_raid6_conf(conf);
2277         return 0;
2278 }
2279
2280 static int raid6_remove_disk(mddev_t *mddev, int number)
2281 {
2282         raid6_conf_t *conf = mddev->private;
2283         int err = 0;
2284         mdk_rdev_t *rdev;
2285         struct disk_info *p = conf->disks + number;
2286
2287         print_raid6_conf(conf);
2288         rdev = p->rdev;
2289         if (rdev) {
2290                 if (test_bit(In_sync, &rdev->flags) ||
2291                     atomic_read(&rdev->nr_pending)) {
2292                         err = -EBUSY;
2293                         goto abort;
2294                 }
2295                 p->rdev = NULL;
2296                 synchronize_rcu();
2297                 if (atomic_read(&rdev->nr_pending)) {
2298                         /* lost the race, try later */
2299                         err = -EBUSY;
2300                         p->rdev = rdev;
2301                 }
2302         }
2303
2304 abort:
2305
2306         print_raid6_conf(conf);
2307         return err;
2308 }
2309
2310 static int raid6_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
2311 {
2312         raid6_conf_t *conf = mddev->private;
2313         int found = 0;
2314         int disk;
2315         struct disk_info *p;
2316
2317         if (mddev->degraded > 2)
2318                 /* no point adding a device */
2319                 return 0;
2320         /*
2321          * find the disk ... but prefer rdev->saved_raid_disk
2322          * if possible.
2323          */
2324         if (rdev->saved_raid_disk >= 0 &&
2325             conf->disks[rdev->saved_raid_disk].rdev == NULL)
2326                 disk = rdev->saved_raid_disk;
2327         else
2328                 disk = 0;
2329         for ( ; disk < mddev->raid_disks; disk++)
2330                 if ((p=conf->disks + disk)->rdev == NULL) {
2331                         clear_bit(In_sync, &rdev->flags);
2332                         rdev->raid_disk = disk;
2333                         found = 1;
2334                         if (rdev->saved_raid_disk != disk)
2335                                 conf->fullsync = 1;
2336                         rcu_assign_pointer(p->rdev, rdev);
2337                         break;
2338                 }
2339         print_raid6_conf(conf);
2340         return found;
2341 }
2342
2343 static int raid6_resize(mddev_t *mddev, sector_t sectors)
2344 {
2345         /* no resync is happening, and there is enough space
2346          * on all devices, so we can resize.
2347          * We need to make sure resync covers any new space.
2348          * If the array is shrinking we should possibly wait until
2349          * any io in the removed space completes, but it hardly seems
2350          * worth it.
2351          */
2352         sectors &= ~((sector_t)mddev->chunk_size/512 - 1);
2353         mddev->array_size = (sectors * (mddev->raid_disks-2))>>1;
2354         set_capacity(mddev->gendisk, mddev->array_size << 1);
2355         mddev->changed = 1;
2356         if (sectors/2  > mddev->size && mddev->recovery_cp == MaxSector) {
2357                 mddev->recovery_cp = mddev->size << 1;
2358                 set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
2359         }
2360         mddev->size = sectors /2;
2361         mddev->resync_max_sectors = sectors;
2362         return 0;
2363 }
2364
2365 static void raid6_quiesce(mddev_t *mddev, int state)
2366 {
2367         raid6_conf_t *conf = mddev_to_conf(mddev);
2368
2369         switch(state) {
2370         case 1: /* stop all writes */
2371                 spin_lock_irq(&conf->device_lock);
2372                 conf->quiesce = 1;
2373                 wait_event_lock_irq(conf->wait_for_stripe,
2374                                     atomic_read(&conf->active_stripes) == 0,
2375                                     conf->device_lock, /* nothing */);
2376                 spin_unlock_irq(&conf->device_lock);
2377                 break;
2378
2379         case 0: /* re-enable writes */
2380                 spin_lock_irq(&conf->device_lock);
2381                 conf->quiesce = 0;
2382                 wake_up(&conf->wait_for_stripe);
2383                 spin_unlock_irq(&conf->device_lock);
2384                 break;
2385         }
2386 }
2387
2388 static struct mdk_personality raid6_personality =
2389 {
2390         .name           = "raid6",
2391         .level          = 6,
2392         .owner          = THIS_MODULE,
2393         .make_request   = make_request,
2394         .run            = run,
2395         .stop           = stop,
2396         .status         = status,
2397         .error_handler  = error,
2398         .hot_add_disk   = raid6_add_disk,
2399         .hot_remove_disk= raid6_remove_disk,
2400         .spare_active   = raid6_spare_active,
2401         .sync_request   = sync_request,
2402         .resize         = raid6_resize,
2403         .quiesce        = raid6_quiesce,
2404 };
2405
2406 static int __init raid6_init(void)
2407 {
2408         int e;
2409
2410         e = raid6_select_algo();
2411         if ( e )
2412                 return e;
2413
2414         return register_md_personality(&raid6_personality);
2415 }
2416
2417 static void raid6_exit (void)
2418 {
2419         unregister_md_personality(&raid6_personality);
2420 }
2421
2422 module_init(raid6_init);
2423 module_exit(raid6_exit);
2424 MODULE_LICENSE("GPL");
2425 MODULE_ALIAS("md-personality-8"); /* RAID6 */
2426 MODULE_ALIAS("md-raid6");
2427 MODULE_ALIAS("md-level-6");