drivers/md/raid10.c

   1 /*
   2  * raid10.c : Multiple Devices driver for Linux
   3  *
   4  * Copyright (C) 2000-2004 Neil Brown
   5  *
   6  * RAID-10 support for md.
   7  *
   8  * Base on code in raid1.c.  See raid1.c for futher copyright information.
   9  *
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation; either version 2, or (at your option)
  14  * any later version.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * (for example /usr/src/linux/COPYING); if not, write to the Free
  18  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #include <linux/delay.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/seq_file.h>
  24 #include "md.h"
  25 #include "raid10.h"
  26 #include "raid0.h"
  27 #include "bitmap.h"
  28
  29 /*
  30  * RAID10 provides a combination of RAID0 and RAID1 functionality.
  31  * The layout of data is defined by
  32  *    chunk_size
  33  *    raid_disks
  34  *    near_copies (stored in low byte of layout)
  35  *    far_copies (stored in second byte of layout)
  36  *    far_offset (stored in bit 16 of layout )
  37  *
  38  * The data to be stored is divided into chunks using chunksize.
  39  * Each device is divided into far_copies sections.
  40  * In each section, chunks are laid out in a style similar to raid0, but
  41  * near_copies copies of each chunk is stored (each on a different drive).
  42  * The starting device for each section is offset near_copies from the starting
  43  * device of the previous section.
  44  * Thus they are (near_copies*far_copies) of each chunk, and each is on a different
  45  * drive.
  46  * near_copies and far_copies must be at least one, and their product is at most
  47  * raid_disks.
  48  *
  49  * If far_offset is true, then the far_copies are handled a bit differently.
  50  * The copies are still in different stripes, but instead of be very far apart
  51  * on disk, there are adjacent stripes.
  52  */
  53
  54 /*
  55  * Number of guaranteed r10bios in case of extreme VM load:
  56  */
  57 #define NR_RAID10_BIOS 256
  58
  59 static void unplug_slaves(mddev_t *mddev);
  60
  61 static void allow_barrier(conf_t *conf);
  62 static void lower_barrier(conf_t *conf);
  63
  64 static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
  65 {
  66         conf_t *conf = data;
  67         r10bio_t *r10_bio;
  68         int size = offsetof(struct r10bio_s, devs[conf->copies]);
  69
  70         /* allocate a r10bio with room for raid_disks entries in the bios array */
  71         r10_bio = kzalloc(size, gfp_flags);
  72         if (!r10_bio && conf->mddev)
  73                 unplug_slaves(conf->mddev);
  74
  75         return r10_bio;
  76 }
  77
  78 static void r10bio_pool_free(void *r10_bio, void *data)
  79 {
  80         kfree(r10_bio);
  81 }
  82
  83 /* Maximum size of each resync request */
  84 #define RESYNC_BLOCK_SIZE (64*1024)
  85 #define RESYNC_PAGES ((RESYNC_BLOCK_SIZE + PAGE_SIZE-1) / PAGE_SIZE)
  86 /* amount of memory to reserve for resync requests */
  87 #define RESYNC_WINDOW (1024*1024)
  88 /* maximum number of concurrent requests, memory permitting */
  89 #define RESYNC_DEPTH (32*1024*1024/RESYNC_BLOCK_SIZE)
  90
  91 /*
  92  * When performing a resync, we need to read and compare, so
  93  * we need as many pages are there are copies.
  94  * When performing a recovery, we need 2 bios, one for read,
  95  * one for write (we recover only one drive per r10buf)
  96  *
  97  */
  98 static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
  99 {
 100         conf_t *conf = data;
 101         struct page *page;
 102         r10bio_t *r10_bio;
 103         struct bio *bio;
 104         int i, j;
 105         int nalloc;
 106
 107         r10_bio = r10bio_pool_alloc(gfp_flags, conf);
 108         if (!r10_bio) {
 109                 unplug_slaves(conf->mddev);
 110                 return NULL;
 111         }
 112
 113         if (test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery))
 114                 nalloc = conf->copies; /* resync */
 115         else
 116                 nalloc = 2; /* recovery */
 117
 118         /*
 119          * Allocate bios.
 120          */
 121         for (j = nalloc ; j-- ; ) {
 122                 bio = bio_alloc(gfp_flags, RESYNC_PAGES);
 123                 if (!bio)
 124                         goto out_free_bio;
 125                 r10_bio->devs[j].bio = bio;
 126         }
 127         /*
 128          * Allocate RESYNC_PAGES data pages and attach them
 129          * where needed.
 130          */
 131         for (j = 0 ; j < nalloc; j++) {
 132                 bio = r10_bio->devs[j].bio;
 133                 for (i = 0; i < RESYNC_PAGES; i++) {
 134                         page = alloc_page(gfp_flags);
 135                         if (unlikely(!page))
 136                                 goto out_free_pages;
 137
 138                         bio->bi_io_vec[i].bv_page = page;
 139                 }
 140         }
 141
 142         return r10_bio;
 143
 144 out_free_pages:
 145         for ( ; i > 0 ; i--)
 146                 safe_put_page(bio->bi_io_vec[i-1].bv_page);
 147         while (j--)
 148                 for (i = 0; i < RESYNC_PAGES ; i++)
 149                         safe_put_page(r10_bio->devs[j].bio->bi_io_vec[i].bv_page);
 150         j = -1;
 151 out_free_bio:
 152         while ( ++j < nalloc )
 153                 bio_put(r10_bio->devs[j].bio);
 154         r10bio_pool_free(r10_bio, conf);
 155         return NULL;
 156 }
 157
 158 static void r10buf_pool_free(void *__r10_bio, void *data)
 159 {
 160         int i;
 161         conf_t *conf = data;
 162         r10bio_t *r10bio = __r10_bio;
 163         int j;
 164
 165         for (j=0; j < conf->copies; j++) {
 166                 struct bio *bio = r10bio->devs[j].bio;
 167                 if (bio) {
 168                         for (i = 0; i < RESYNC_PAGES; i++) {
 169                                 safe_put_page(bio->bi_io_vec[i].bv_page);
 170                                 bio->bi_io_vec[i].bv_page = NULL;
 171                         }
 172                         bio_put(bio);
 173                 }
 174         }
 175         r10bio_pool_free(r10bio, conf);
 176 }
 177
 178 static void put_all_bios(conf_t *conf, r10bio_t *r10_bio)
 179 {
 180         int i;
 181
 182         for (i = 0; i < conf->copies; i++) {
 183                 struct bio **bio = & r10_bio->devs[i].bio;
 184                 if (*bio && *bio != IO_BLOCKED)
 185                         bio_put(*bio);
 186                 *bio = NULL;
 187         }
 188 }
 189
 190 static void free_r10bio(r10bio_t *r10_bio)
 191 {
 192         conf_t *conf = r10_bio->mddev->private;
 193
 194         /*
 195          * Wake up any possible resync thread that waits for the device
 196          * to go idle.
 197          */
 198         allow_barrier(conf);
 199
 200         put_all_bios(conf, r10_bio);
 201         mempool_free(r10_bio, conf->r10bio_pool);
 202 }
 203
 204 static void put_buf(r10bio_t *r10_bio)
 205 {
 206         conf_t *conf = r10_bio->mddev->private;
 207
 208         mempool_free(r10_bio, conf->r10buf_pool);
 209
 210         lower_barrier(conf);
 211 }
 212
 213 static void reschedule_retry(r10bio_t *r10_bio)
 214 {
 215         unsigned long flags;
 216         mddev_t *mddev = r10_bio->mddev;
 217         conf_t *conf = mddev->private;
 218
 219         spin_lock_irqsave(&conf->device_lock, flags);
 220         list_add(&r10_bio->retry_list, &conf->retry_list);
 221         conf->nr_queued ++;
 222         spin_unlock_irqrestore(&conf->device_lock, flags);
 223
 224         /* wake up frozen array... */
 225         wake_up(&conf->wait_barrier);
 226
 227         md_wakeup_thread(mddev->thread);
 228 }
 229
 230 /*
 231  * raid_end_bio_io() is called when we have finished servicing a mirrored
 232  * operation and are ready to return a success/failure code to the buffer
 233  * cache layer.
 234  */
 235 static void raid_end_bio_io(r10bio_t *r10_bio)
 236 {
 237         struct bio *bio = r10_bio->master_bio;
 238
 239         bio_endio(bio,
 240                 test_bit(R10BIO_Uptodate, &r10_bio->state) ? 0 : -EIO);
 241         free_r10bio(r10_bio);
 242 }
 243
 244 /*
 245  * Update disk head position estimator based on IRQ completion info.
 246  */
 247 static inline void update_head_pos(int slot, r10bio_t *r10_bio)
 248 {
 249         conf_t *conf = r10_bio->mddev->private;
 250
 251         conf->mirrors[r10_bio->devs[slot].devnum].head_position =
 252                 r10_bio->devs[slot].addr + (r10_bio->sectors);
 253 }
 254
 255 static void raid10_end_read_request(struct bio *bio, int error)
 256 {
 257         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 258         r10bio_t *r10_bio = bio->bi_private;
 259         int slot, dev;
 260         conf_t *conf = r10_bio->mddev->private;
 261
 262
 263         slot = r10_bio->read_slot;
 264         dev = r10_bio->devs[slot].devnum;
 265         /*
 266          * this branch is our 'one mirror IO has finished' event handler:
 267          */
 268         update_head_pos(slot, r10_bio);
 269
 270         if (uptodate) {
 271                 /*
 272                  * Set R10BIO_Uptodate in our master bio, so that
 273                  * we will return a good error code to the higher
 274                  * levels even if IO on some other mirrored buffer fails.
 275                  *
 276                  * The 'master' represents the composite IO operation to
 277                  * user-side. So if something waits for IO, then it will
 278                  * wait for the 'master' bio.
 279                  */
 280                 set_bit(R10BIO_Uptodate, &r10_bio->state);
 281                 raid_end_bio_io(r10_bio);
 282         } else {
 283                 /*
 284                  * oops, read error:
 285                  */
 286                 char b[BDEVNAME_SIZE];
 287                 if (printk_ratelimit())
 288                         printk(KERN_ERR "md/raid10:%s: %s: rescheduling sector %llu\n",
 289                                mdname(conf->mddev),
 290                                bdevname(conf->mirrors[dev].rdev->bdev,b), (unsigned long long)r10_bio->sector);
 291                 reschedule_retry(r10_bio);
 292         }
 293
 294         rdev_dec_pending(conf->mirrors[dev].rdev, conf->mddev);
 295 }
 296
 297 static void raid10_end_write_request(struct bio *bio, int error)
 298 {
 299         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 300         r10bio_t *r10_bio = bio->bi_private;
 301         int slot, dev;
 302         conf_t *conf = r10_bio->mddev->private;
 303
 304         for (slot = 0; slot < conf->copies; slot++)
 305                 if (r10_bio->devs[slot].bio == bio)
 306                         break;
 307         dev = r10_bio->devs[slot].devnum;
 308
 309         /*
 310          * this branch is our 'one mirror IO has finished' event handler:
 311          */
 312         if (!uptodate) {
 313                 md_error(r10_bio->mddev, conf->mirrors[dev].rdev);
 314                 /* an I/O failed, we can't clear the bitmap */
 315                 set_bit(R10BIO_Degraded, &r10_bio->state);
 316         } else
 317                 /*
 318                  * Set R10BIO_Uptodate in our master bio, so that
 319                  * we will return a good error code for to the higher
 320                  * levels even if IO on some other mirrored buffer fails.
 321                  *
 322                  * The 'master' represents the composite IO operation to
 323                  * user-side. So if something waits for IO, then it will
 324                  * wait for the 'master' bio.
 325                  */
 326                 set_bit(R10BIO_Uptodate, &r10_bio->state);
 327
 328         update_head_pos(slot, r10_bio);
 329
 330         /*
 331          *
 332          * Let's see if all mirrored write operations have finished
 333          * already.
 334          */
 335         if (atomic_dec_and_test(&r10_bio->remaining)) {
 336                 /* clear the bitmap if all writes complete successfully */
 337                 bitmap_endwrite(r10_bio->mddev->bitmap, r10_bio->sector,
 338                                 r10_bio->sectors,
 339                                 !test_bit(R10BIO_Degraded, &r10_bio->state),
 340                                 0);
 341                 md_write_end(r10_bio->mddev);
 342                 raid_end_bio_io(r10_bio);
 343         }
 344
 345         rdev_dec_pending(conf->mirrors[dev].rdev, conf->mddev);
 346 }
 347
 348
 349 /*
 350  * RAID10 layout manager
 351  * Aswell as the chunksize and raid_disks count, there are two
 352  * parameters: near_copies and far_copies.
 353  * near_copies * far_copies must be <= raid_disks.
 354  * Normally one of these will be 1.
 355  * If both are 1, we get raid0.
 356  * If near_copies == raid_disks, we get raid1.
 357  *
 358  * Chunks are layed out in raid0 style with near_copies copies of the
 359  * first chunk, followed by near_copies copies of the next chunk and
 360  * so on.
 361  * If far_copies > 1, then after 1/far_copies of the array has been assigned
 362  * as described above, we start again with a device offset of near_copies.
 363  * So we effectively have another copy of the whole array further down all
 364  * the drives, but with blocks on different drives.
 365  * With this layout, and block is never stored twice on the one device.
 366  *
 367  * raid10_find_phys finds the sector offset of a given virtual sector
 368  * on each device that it is on.
 369  *
 370  * raid10_find_virt does the reverse mapping, from a device and a
 371  * sector offset to a virtual address
 372  */
 373
 374 static void raid10_find_phys(conf_t *conf, r10bio_t *r10bio)
 375 {
 376         int n,f;
 377         sector_t sector;
 378         sector_t chunk;
 379         sector_t stripe;
 380         int dev;
 381
 382         int slot = 0;
 383
 384         /* now calculate first sector/dev */
 385         chunk = r10bio->sector >> conf->chunk_shift;
 386         sector = r10bio->sector & conf->chunk_mask;
 387
 388         chunk *= conf->near_copies;
 389         stripe = chunk;
 390         dev = sector_div(stripe, conf->raid_disks);
 391         if (conf->far_offset)
 392                 stripe *= conf->far_copies;
 393
 394         sector += stripe << conf->chunk_shift;
 395
 396         /* and calculate all the others */
 397         for (n=0; n < conf->near_copies; n++) {
 398                 int d = dev;
 399                 sector_t s = sector;
 400                 r10bio->devs[slot].addr = sector;
 401                 r10bio->devs[slot].devnum = d;
 402                 slot++;
 403
 404                 for (f = 1; f < conf->far_copies; f++) {
 405                         d += conf->near_copies;
 406                         if (d >= conf->raid_disks)
 407                                 d -= conf->raid_disks;
 408                         s += conf->stride;
 409                         r10bio->devs[slot].devnum = d;
 410                         r10bio->devs[slot].addr = s;
 411                         slot++;
 412                 }
 413                 dev++;
 414                 if (dev >= conf->raid_disks) {
 415                         dev = 0;
 416                         sector += (conf->chunk_mask + 1);
 417                 }
 418         }
 419         BUG_ON(slot != conf->copies);
 420 }
 421
 422 static sector_t raid10_find_virt(conf_t *conf, sector_t sector, int dev)
 423 {
 424         sector_t offset, chunk, vchunk;
 425
 426         offset = sector & conf->chunk_mask;
 427         if (conf->far_offset) {
 428                 int fc;
 429                 chunk = sector >> conf->chunk_shift;
 430                 fc = sector_div(chunk, conf->far_copies);
 431                 dev -= fc * conf->near_copies;
 432                 if (dev < 0)
 433                         dev += conf->raid_disks;
 434         } else {
 435                 while (sector >= conf->stride) {
 436                         sector -= conf->stride;
 437                         if (dev < conf->near_copies)
 438                                 dev += conf->raid_disks - conf->near_copies;
 439                         else
 440                                 dev -= conf->near_copies;
 441                 }
 442                 chunk = sector >> conf->chunk_shift;
 443         }
 444         vchunk = chunk * conf->raid_disks + dev;
 445         sector_div(vchunk, conf->near_copies);
 446         return (vchunk << conf->chunk_shift) + offset;
 447 }
 448
 449 /**
 450  *      raid10_mergeable_bvec -- tell bio layer if a two requests can be merged
 451  *      @q: request queue
 452  *      @bvm: properties of new bio
 453  *      @biovec: the request that could be merged to it.
 454  *
 455  *      Return amount of bytes we can accept at this offset
 456  *      If near_copies == raid_disk, there are no striping issues,
 457  *      but in that case, the function isn't called at all.
 458  */
 459 static int raid10_mergeable_bvec(struct request_queue *q,
 460                                  struct bvec_merge_data *bvm,
 461                                  struct bio_vec *biovec)
 462 {
 463         mddev_t *mddev = q->queuedata;
 464         sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
 465         int max;
 466         unsigned int chunk_sectors = mddev->chunk_sectors;
 467         unsigned int bio_sectors = bvm->bi_size >> 9;
 468
 469         max =  (chunk_sectors - ((sector & (chunk_sectors - 1)) + bio_sectors)) << 9;
 470         if (max < 0) max = 0; /* bio_add cannot handle a negative return */
 471         if (max <= biovec->bv_len && bio_sectors == 0)
 472                 return biovec->bv_len;
 473         else
 474                 return max;
 475 }
 476
 477 /*
 478  * This routine returns the disk from which the requested read should
 479  * be done. There is a per-array 'next expected sequential IO' sector
 480  * number - if this matches on the next IO then we use the last disk.
 481  * There is also a per-disk 'last know head position' sector that is
 482  * maintained from IRQ contexts, both the normal and the resync IO
 483  * completion handlers update this position correctly. If there is no
 484  * perfect sequential match then we pick the disk whose head is closest.
 485  *
 486  * If there are 2 mirrors in the same 2 devices, performance degrades
 487  * because position is mirror, not device based.
 488  *
 489  * The rdev for the device selected will have nr_pending incremented.
 490  */
 491
 492 /*
 493  * FIXME: possibly should rethink readbalancing and do it differently
 494  * depending on near_copies / far_copies geometry.
 495  */
 496 static int read_balance(conf_t *conf, r10bio_t *r10_bio)
 497 {
 498         const unsigned long this_sector = r10_bio->sector;
 499         int disk, slot, nslot;
 500         const int sectors = r10_bio->sectors;
 501         sector_t new_distance, current_distance;
 502         mdk_rdev_t *rdev;
 503
 504         raid10_find_phys(conf, r10_bio);
 505         rcu_read_lock();
 506         /*
 507          * Check if we can balance. We can balance on the whole
 508          * device if no resync is going on (recovery is ok), or below
 509          * the resync window. We take the first readable disk when
 510          * above the resync window.
 511          */
 512         if (conf->mddev->recovery_cp < MaxSector
 513             && (this_sector + sectors >= conf->next_resync)) {
 514                 /* make sure that disk is operational */
 515                 slot = 0;
 516                 disk = r10_bio->devs[slot].devnum;
 517
 518                 while ((rdev = rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
 519                        r10_bio->devs[slot].bio == IO_BLOCKED ||
 520                        !test_bit(In_sync, &rdev->flags)) {
 521                         slot++;
 522                         if (slot == conf->copies) {
 523                                 slot = 0;
 524                                 disk = -1;
 525                                 break;
 526                         }
 527                         disk = r10_bio->devs[slot].devnum;
 528                 }
 529                 goto rb_out;
 530         }
 531
 532
 533         /* make sure the disk is operational */
 534         slot = 0;
 535         disk = r10_bio->devs[slot].devnum;
 536         while ((rdev=rcu_dereference(conf->mirrors[disk].rdev)) == NULL ||
 537                r10_bio->devs[slot].bio == IO_BLOCKED ||
 538                !test_bit(In_sync, &rdev->flags)) {
 539                 slot ++;
 540                 if (slot == conf->copies) {
 541                         disk = -1;
 542                         goto rb_out;
 543                 }
 544                 disk = r10_bio->devs[slot].devnum;
 545         }
 546
 547
 548         current_distance = abs(r10_bio->devs[slot].addr -
 549                                conf->mirrors[disk].head_position);
 550
 551         /* Find the disk whose head is closest,
 552          * or - for far > 1 - find the closest to partition beginning */
 553
 554         for (nslot = slot; nslot < conf->copies; nslot++) {
 555                 int ndisk = r10_bio->devs[nslot].devnum;
 556
 557
 558                 if ((rdev=rcu_dereference(conf->mirrors[ndisk].rdev)) == NULL ||
 559                     r10_bio->devs[nslot].bio == IO_BLOCKED ||
 560                     !test_bit(In_sync, &rdev->flags))
 561                         continue;
 562
 563                 /* This optimisation is debatable, and completely destroys
 564                  * sequential read speed for 'far copies' arrays.  So only
 565                  * keep it for 'near' arrays, and review those later.
 566                  */
 567                 if (conf->near_copies > 1 && !atomic_read(&rdev->nr_pending)) {
 568                         disk = ndisk;
 569                         slot = nslot;
 570                         break;
 571                 }
 572
 573                 /* for far > 1 always use the lowest address */
 574                 if (conf->far_copies > 1)
 575                         new_distance = r10_bio->devs[nslot].addr;
 576                 else
 577                         new_distance = abs(r10_bio->devs[nslot].addr -
 578                                            conf->mirrors[ndisk].head_position);
 579                 if (new_distance < current_distance) {
 580                         current_distance = new_distance;
 581                         disk = ndisk;
 582                         slot = nslot;
 583                 }
 584         }
 585
 586 rb_out:
 587         r10_bio->read_slot = slot;
 588 /*      conf->next_seq_sect = this_sector + sectors;*/
 589
 590         if (disk >= 0 && (rdev=rcu_dereference(conf->mirrors[disk].rdev))!= NULL)
 591                 atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
 592         else
 593                 disk = -1;
 594         rcu_read_unlock();
 595
 596         return disk;
 597 }
 598
 599 static void unplug_slaves(mddev_t *mddev)
 600 {
 601         conf_t *conf = mddev->private;
 602         int i;
 603
 604         rcu_read_lock();
 605         for (i=0; i < conf->raid_disks; i++) {
 606                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
 607                 if (rdev && !test_bit(Faulty, &rdev->flags) && atomic_read(&rdev->nr_pending)) {
 608                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
 609
 610                         atomic_inc(&rdev->nr_pending);
 611                         rcu_read_unlock();
 612
 613                         blk_unplug(r_queue);
 614
 615                         rdev_dec_pending(rdev, mddev);
 616                         rcu_read_lock();
 617                 }
 618         }
 619         rcu_read_unlock();
 620 }
 621
 622 static void raid10_unplug(struct request_queue *q)
 623 {
 624         mddev_t *mddev = q->queuedata;
 625
 626         unplug_slaves(q->queuedata);
 627         md_wakeup_thread(mddev->thread);
 628 }
 629
 630 static int raid10_congested(void *data, int bits)
 631 {
 632         mddev_t *mddev = data;
 633         conf_t *conf = mddev->private;
 634         int i, ret = 0;
 635
 636         if (mddev_congested(mddev, bits))
 637                 return 1;
 638         rcu_read_lock();
 639         for (i = 0; i < conf->raid_disks && ret == 0; i++) {
 640                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[i].rdev);
 641                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 642                         struct request_queue *q = bdev_get_queue(rdev->bdev);
 643
 644                         ret |= bdi_congested(&q->backing_dev_info, bits);
 645                 }
 646         }
 647         rcu_read_unlock();
 648         return ret;
 649 }
 650
 651 static int flush_pending_writes(conf_t *conf)
 652 {
 653         /* Any writes that have been queued but are awaiting
 654          * bitmap updates get flushed here.
 655          * We return 1 if any requests were actually submitted.
 656          */
 657         int rv = 0;
 658
 659         spin_lock_irq(&conf->device_lock);
 660
 661         if (conf->pending_bio_list.head) {
 662                 struct bio *bio;
 663                 bio = bio_list_get(&conf->pending_bio_list);
 664                 blk_remove_plug(conf->mddev->queue);
 665                 spin_unlock_irq(&conf->device_lock);
 666                 /* flush any pending bitmap writes to disk
 667                  * before proceeding w/ I/O */
 668                 bitmap_unplug(conf->mddev->bitmap);
 669
 670                 while (bio) { /* submit pending writes */
 671                         struct bio *next = bio->bi_next;
 672                         bio->bi_next = NULL;
 673                         generic_make_request(bio);
 674                         bio = next;
 675                 }
 676                 rv = 1;
 677         } else
 678                 spin_unlock_irq(&conf->device_lock);
 679         return rv;
 680 }
 681 /* Barriers....
 682  * Sometimes we need to suspend IO while we do something else,
 683  * either some resync/recovery, or reconfigure the array.
 684  * To do this we raise a 'barrier'.
 685  * The 'barrier' is a counter that can be raised multiple times
 686  * to count how many activities are happening which preclude
 687  * normal IO.
 688  * We can only raise the barrier if there is no pending IO.
 689  * i.e. if nr_pending == 0.
 690  * We choose only to raise the barrier if no-one is waiting for the
 691  * barrier to go down.  This means that as soon as an IO request
 692  * is ready, no other operations which require a barrier will start
 693  * until the IO request has had a chance.
 694  *
 695  * So: regular IO calls 'wait_barrier'.  When that returns there
 696  *    is no backgroup IO happening,  It must arrange to call
 697  *    allow_barrier when it has finished its IO.
 698  * backgroup IO calls must call raise_barrier.  Once that returns
 699  *    there is no normal IO happeing.  It must arrange to call
 700  *    lower_barrier when the particular background IO completes.
 701  */
 702
 703 static void raise_barrier(conf_t *conf, int force)
 704 {
 705         BUG_ON(force && !conf->barrier);
 706         spin_lock_irq(&conf->resync_lock);
 707
 708         /* Wait until no block IO is waiting (unless 'force') */
 709         wait_event_lock_irq(conf->wait_barrier, force || !conf->nr_waiting,
 710                             conf->resync_lock,
 711                             raid10_unplug(conf->mddev->queue));
 712
 713         /* block any new IO from starting */
 714         conf->barrier++;
 715
 716         /* No wait for all pending IO to complete */
 717         wait_event_lock_irq(conf->wait_barrier,
 718                             !conf->nr_pending && conf->barrier < RESYNC_DEPTH,
 719                             conf->resync_lock,
 720                             raid10_unplug(conf->mddev->queue));
 721
 722         spin_unlock_irq(&conf->resync_lock);
 723 }
 724
 725 static void lower_barrier(conf_t *conf)
 726 {
 727         unsigned long flags;
 728         spin_lock_irqsave(&conf->resync_lock, flags);
 729         conf->barrier--;
 730         spin_unlock_irqrestore(&conf->resync_lock, flags);
 731         wake_up(&conf->wait_barrier);
 732 }
 733
 734 static void wait_barrier(conf_t *conf)
 735 {
 736         spin_lock_irq(&conf->resync_lock);
 737         if (conf->barrier) {
 738                 conf->nr_waiting++;
 739                 wait_event_lock_irq(conf->wait_barrier, !conf->barrier,
 740                                     conf->resync_lock,
 741                                     raid10_unplug(conf->mddev->queue));
 742                 conf->nr_waiting--;
 743         }
 744         conf->nr_pending++;
 745         spin_unlock_irq(&conf->resync_lock);
 746 }
 747
 748 static void allow_barrier(conf_t *conf)
 749 {
 750         unsigned long flags;
 751         spin_lock_irqsave(&conf->resync_lock, flags);
 752         conf->nr_pending--;
 753         spin_unlock_irqrestore(&conf->resync_lock, flags);
 754         wake_up(&conf->wait_barrier);
 755 }
 756
 757 static void freeze_array(conf_t *conf)
 758 {
 759         /* stop syncio and normal IO and wait for everything to
 760          * go quiet.
 761          * We increment barrier and nr_waiting, and then
 762          * wait until nr_pending match nr_queued+1
 763          * This is called in the context of one normal IO request
 764          * that has failed. Thus any sync request that might be pending
 765          * will be blocked by nr_pending, and we need to wait for
 766          * pending IO requests to complete or be queued for re-try.
 767          * Thus the number queued (nr_queued) plus this request (1)
 768          * must match the number of pending IOs (nr_pending) before
 769          * we continue.
 770          */
 771         spin_lock_irq(&conf->resync_lock);
 772         conf->barrier++;
 773         conf->nr_waiting++;
 774         wait_event_lock_irq(conf->wait_barrier,
 775                             conf->nr_pending == conf->nr_queued+1,
 776                             conf->resync_lock,
 777                             ({ flush_pending_writes(conf);
 778                                raid10_unplug(conf->mddev->queue); }));
 779         spin_unlock_irq(&conf->resync_lock);
 780 }
 781
 782 static void unfreeze_array(conf_t *conf)
 783 {
 784         /* reverse the effect of the freeze */
 785         spin_lock_irq(&conf->resync_lock);
 786         conf->barrier--;
 787         conf->nr_waiting--;
 788         wake_up(&conf->wait_barrier);
 789         spin_unlock_irq(&conf->resync_lock);
 790 }
 791
 792 static int make_request(mddev_t *mddev, struct bio * bio)
 793 {
 794         conf_t *conf = mddev->private;
 795         mirror_info_t *mirror;
 796         r10bio_t *r10_bio;
 797         struct bio *read_bio;
 798         int i;
 799         int chunk_sects = conf->chunk_mask + 1;
 800         const int rw = bio_data_dir(bio);
 801         const bool do_sync = bio_rw_flagged(bio, BIO_RW_SYNCIO);
 802         struct bio_list bl;
 803         unsigned long flags;
 804         mdk_rdev_t *blocked_rdev;
 805
 806         if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER))) {
 807                 md_barrier_request(mddev, bio);
 808                 return 0;
 809         }
 810
 811         /* If this request crosses a chunk boundary, we need to
 812          * split it.  This will only happen for 1 PAGE (or less) requests.
 813          */
 814         if (unlikely( (bio->bi_sector & conf->chunk_mask) + (bio->bi_size >> 9)
 815                       > chunk_sects &&
 816                     conf->near_copies < conf->raid_disks)) {
 817                 struct bio_pair *bp;
 818                 /* Sanity check -- queue functions should prevent this happening */
 819                 if (bio->bi_vcnt != 1 ||
 820                     bio->bi_idx != 0)
 821                         goto bad_map;
 822                 /* This is a one page bio that upper layers
 823                  * refuse to split for us, so we need to split it.
 824                  */
 825                 bp = bio_split(bio,
 826                                chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
 827                 if (make_request(mddev, &bp->bio1))
 828                         generic_make_request(&bp->bio1);
 829                 if (make_request(mddev, &bp->bio2))
 830                         generic_make_request(&bp->bio2);
 831
 832                 bio_pair_release(bp);
 833                 return 0;
 834         bad_map:
 835                 printk("md/raid10:%s: make_request bug: can't convert block across chunks"
 836                        " or bigger than %dk %llu %d\n", mdname(mddev), chunk_sects/2,
 837                        (unsigned long long)bio->bi_sector, bio->bi_size >> 10);
 838
 839                 bio_io_error(bio);
 840                 return 0;
 841         }
 842
 843         md_write_start(mddev, bio);
 844
 845         /*
 846          * Register the new request and wait if the reconstruction
 847          * thread has put up a bar for new requests.
 848          * Continue immediately if no resync is active currently.
 849          */
 850         wait_barrier(conf);
 851
 852         r10_bio = mempool_alloc(conf->r10bio_pool, GFP_NOIO);
 853
 854         r10_bio->master_bio = bio;
 855         r10_bio->sectors = bio->bi_size >> 9;
 856
 857         r10_bio->mddev = mddev;
 858         r10_bio->sector = bio->bi_sector;
 859         r10_bio->state = 0;
 860
 861         if (rw == READ) {
 862                 /*
 863                  * read balancing logic:
 864                  */
 865                 int disk = read_balance(conf, r10_bio);
 866                 int slot = r10_bio->read_slot;
 867                 if (disk < 0) {
 868                         raid_end_bio_io(r10_bio);
 869                         return 0;
 870                 }
 871                 mirror = conf->mirrors + disk;
 872
 873                 read_bio = bio_clone(bio, GFP_NOIO);
 874
 875                 r10_bio->devs[slot].bio = read_bio;
 876
 877                 read_bio->bi_sector = r10_bio->devs[slot].addr +
 878                         mirror->rdev->data_offset;
 879                 read_bio->bi_bdev = mirror->rdev->bdev;
 880                 read_bio->bi_end_io = raid10_end_read_request;
 881                 read_bio->bi_rw = READ | (do_sync << BIO_RW_SYNCIO);
 882                 read_bio->bi_private = r10_bio;
 883
 884                 generic_make_request(read_bio);
 885                 return 0;
 886         }
 887
 888         /*
 889          * WRITE:
 890          */
 891         /* first select target devices under rcu_lock and
 892          * inc refcount on their rdev.  Record them by setting
 893          * bios[x] to bio
 894          */
 895         raid10_find_phys(conf, r10_bio);
 896  retry_write:
 897         blocked_rdev = NULL;
 898         rcu_read_lock();
 899         for (i = 0;  i < conf->copies; i++) {
 900                 int d = r10_bio->devs[i].devnum;
 901                 mdk_rdev_t *rdev = rcu_dereference(conf->mirrors[d].rdev);
 902                 if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
 903                         atomic_inc(&rdev->nr_pending);
 904                         blocked_rdev = rdev;
 905                         break;
 906                 }
 907                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 908                         atomic_inc(&rdev->nr_pending);
 909                         r10_bio->devs[i].bio = bio;
 910                 } else {
 911                         r10_bio->devs[i].bio = NULL;
 912                         set_bit(R10BIO_Degraded, &r10_bio->state);
 913                 }
 914         }
 915         rcu_read_unlock();
 916
 917         if (unlikely(blocked_rdev)) {
 918                 /* Have to wait for this device to get unblocked, then retry */
 919                 int j;
 920                 int d;
 921
 922                 for (j = 0; j < i; j++)
 923                         if (r10_bio->devs[j].bio) {
 924                                 d = r10_bio->devs[j].devnum;
 925                                 rdev_dec_pending(conf->mirrors[d].rdev, mddev);
 926                         }
 927                 allow_barrier(conf);
 928                 md_wait_for_blocked_rdev(blocked_rdev, mddev);
 929                 wait_barrier(conf);
 930                 goto retry_write;
 931         }
 932
 933         atomic_set(&r10_bio->remaining, 0);
 934
 935         bio_list_init(&bl);
 936         for (i = 0; i < conf->copies; i++) {
 937                 struct bio *mbio;
 938                 int d = r10_bio->devs[i].devnum;
 939                 if (!r10_bio->devs[i].bio)
 940                         continue;
 941
 942                 mbio = bio_clone(bio, GFP_NOIO);
 943                 r10_bio->devs[i].bio = mbio;
 944
 945                 mbio->bi_sector = r10_bio->devs[i].addr+
 946                         conf->mirrors[d].rdev->data_offset;
 947                 mbio->bi_bdev = conf->mirrors[d].rdev->bdev;
 948                 mbio->bi_end_io = raid10_end_write_request;
 949                 mbio->bi_rw = WRITE | (do_sync << BIO_RW_SYNCIO);
 950                 mbio->bi_private = r10_bio;
 951
 952                 atomic_inc(&r10_bio->remaining);
 953                 bio_list_add(&bl, mbio);
 954         }
 955
 956         if (unlikely(!atomic_read(&r10_bio->remaining))) {
 957                 /* the array is dead */
 958                 md_write_end(mddev);
 959                 raid_end_bio_io(r10_bio);
 960                 return 0;
 961         }
 962
 963         bitmap_startwrite(mddev->bitmap, bio->bi_sector, r10_bio->sectors, 0);
 964         spin_lock_irqsave(&conf->device_lock, flags);
 965         bio_list_merge(&conf->pending_bio_list, &bl);
 966         blk_plug_device(mddev->queue);
 967         spin_unlock_irqrestore(&conf->device_lock, flags);
 968
 969         /* In case raid10d snuck in to freeze_array */
 970         wake_up(&conf->wait_barrier);
 971
 972         if (do_sync)
 973                 md_wakeup_thread(mddev->thread);
 974
 975         return 0;
 976 }
 977
 978 static void status(struct seq_file *seq, mddev_t *mddev)
 979 {
 980         conf_t *conf = mddev->private;
 981         int i;
 982
 983         if (conf->near_copies < conf->raid_disks)
 984                 seq_printf(seq, " %dK chunks", mddev->chunk_sectors / 2);
 985         if (conf->near_copies > 1)
 986                 seq_printf(seq, " %d near-copies", conf->near_copies);
 987         if (conf->far_copies > 1) {
 988                 if (conf->far_offset)
 989                         seq_printf(seq, " %d offset-copies", conf->far_copies);
 990                 else
 991                         seq_printf(seq, " %d far-copies", conf->far_copies);
 992         }
 993         seq_printf(seq, " [%d/%d] [", conf->raid_disks,
 994                                         conf->raid_disks - mddev->degraded);
 995         for (i = 0; i < conf->raid_disks; i++)
 996                 seq_printf(seq, "%s",
 997                               conf->mirrors[i].rdev &&
 998                               test_bit(In_sync, &conf->mirrors[i].rdev->flags) ? "U" : "_");
 999         seq_printf(seq, "]");
1000 }
1001
1002 static void error(mddev_t *mddev, mdk_rdev_t *rdev)
1003 {
1004         char b[BDEVNAME_SIZE];
1005         conf_t *conf = mddev->private;
1006
1007         /*
1008          * If it is not operational, then we have already marked it as dead
1009          * else if it is the last working disks, ignore the error, let the
1010          * next level up know.
1011          * else mark the drive as failed
1012          */
1013         if (test_bit(In_sync, &rdev->flags)
1014             && conf->raid_disks-mddev->degraded == 1)
1015                 /*
1016                  * Don't fail the drive, just return an IO error.
1017                  * The test should really be more sophisticated than
1018                  * "working_disks == 1", but it isn't critical, and
1019                  * can wait until we do more sophisticated "is the drive
1020                  * really dead" tests...
1021                  */
1022                 return;
1023         if (test_and_clear_bit(In_sync, &rdev->flags)) {
1024                 unsigned long flags;
1025                 spin_lock_irqsave(&conf->device_lock, flags);
1026                 mddev->degraded++;
1027                 spin_unlock_irqrestore(&conf->device_lock, flags);
1028                 /*
1029                  * if recovery is running, make sure it aborts.
1030                  */
1031                 set_bit(MD_RECOVERY_INTR, &mddev->recovery);
1032         }
1033         set_bit(Faulty, &rdev->flags);
1034         set_bit(MD_CHANGE_DEVS, &mddev->flags);
1035         printk(KERN_ALERT "md/raid10:%s: Disk failure on %s, disabling device.\n"
1036                KERN_ALERT "md/raid10:%s: Operation continuing on %d devices.\n",
1037                mdname(mddev), bdevname(rdev->bdev, b),
1038                mdname(mddev), conf->raid_disks - mddev->degraded);
1039 }
1040
1041 static void print_conf(conf_t *conf)
1042 {
1043         int i;
1044         mirror_info_t *tmp;
1045
1046         printk(KERN_DEBUG "RAID10 conf printout:\n");
1047         if (!conf) {
1048                 printk(KERN_DEBUG "(!conf)\n");
1049                 return;
1050         }
1051         printk(KERN_DEBUG " --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
1052                 conf->raid_disks);
1053
1054         for (i = 0; i < conf->raid_disks; i++) {
1055                 char b[BDEVNAME_SIZE];
1056                 tmp = conf->mirrors + i;
1057                 if (tmp->rdev)
1058                         printk(KERN_DEBUG " disk %d, wo:%d, o:%d, dev:%s\n",
1059                                 i, !test_bit(In_sync, &tmp->rdev->flags),
1060                                 !test_bit(Faulty, &tmp->rdev->flags),
1061                                 bdevname(tmp->rdev->bdev,b));
1062         }
1063 }
1064
1065 static void close_sync(conf_t *conf)
1066 {
1067         wait_barrier(conf);
1068         allow_barrier(conf);
1069
1070         mempool_destroy(conf->r10buf_pool);
1071         conf->r10buf_pool = NULL;
1072 }
1073
1074 /* check if there are enough drives for
1075  * every block to appear on atleast one
1076  */
1077 static int enough(conf_t *conf)
1078 {
1079         int first = 0;
1080
1081         do {
1082                 int n = conf->copies;
1083                 int cnt = 0;
1084                 while (n--) {
1085                         if (conf->mirrors[first].rdev)
1086                                 cnt++;
1087                         first = (first+1) % conf->raid_disks;
1088                 }
1089                 if (cnt == 0)
1090                         return 0;
1091         } while (first != 0);
1092         return 1;
1093 }
1094
1095 static int raid10_spare_active(mddev_t *mddev)
1096 {
1097         int i;
1098         conf_t *conf = mddev->private;
1099         mirror_info_t *tmp;
1100
1101         /*
1102          * Find all non-in_sync disks within the RAID10 configuration
1103          * and mark them in_sync
1104          */
1105         for (i = 0; i < conf->raid_disks; i++) {
1106                 tmp = conf->mirrors + i;
1107                 if (tmp->rdev
1108                     && !test_bit(Faulty, &tmp->rdev->flags)
1109                     && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
1110                         unsigned long flags;
1111                         spin_lock_irqsave(&conf->device_lock, flags);
1112                         mddev->degraded--;
1113                         spin_unlock_irqrestore(&conf->device_lock, flags);
1114                 }
1115         }
1116
1117         print_conf(conf);
1118         return 0;
1119 }
1120
1121
1122 static int raid10_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
1123 {
1124         conf_t *conf = mddev->private;
1125         int err = -EEXIST;
1126         int mirror;
1127         mirror_info_t *p;
1128         int first = 0;
1129         int last = conf->raid_disks - 1;
1130
1131         if (mddev->recovery_cp < MaxSector)
1132                 /* only hot-add to in-sync arrays, as recovery is
1133                  * very different from resync
1134                  */
1135                 return -EBUSY;
1136         if (!enough(conf))
1137                 return -EINVAL;
1138
1139         if (rdev->raid_disk >= 0)
1140                 first = last = rdev->raid_disk;
1141
1142         if (rdev->saved_raid_disk >= 0 &&
1143             rdev->saved_raid_disk >= first &&
1144             conf->mirrors[rdev->saved_raid_disk].rdev == NULL)
1145                 mirror = rdev->saved_raid_disk;
1146         else
1147                 mirror = first;
1148         for ( ; mirror <= last ; mirror++)
1149                 if ( !(p=conf->mirrors+mirror)->rdev) {
1150
1151                         disk_stack_limits(mddev->gendisk, rdev->bdev,
1152                                           rdev->data_offset << 9);
1153                         /* as we don't honour merge_bvec_fn, we must
1154                          * never risk violating it, so limit
1155                          * ->max_segments to one lying with a single
1156                          * page, as a one page request is never in
1157                          * violation.
1158                          */
1159                         if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
1160                                 blk_queue_max_segments(mddev->queue, 1);
1161                                 blk_queue_segment_boundary(mddev->queue,
1162                                                            PAGE_CACHE_SIZE - 1);
1163                         }
1164
1165                         p->head_position = 0;
1166                         rdev->raid_disk = mirror;
1167                         err = 0;
1168                         if (rdev->saved_raid_disk != mirror)
1169                                 conf->fullsync = 1;
1170                         rcu_assign_pointer(p->rdev, rdev);
1171                         break;
1172                 }
1173
1174         md_integrity_add_rdev(rdev, mddev);
1175         print_conf(conf);
1176         return err;
1177 }
1178
1179 static int raid10_remove_disk(mddev_t *mddev, int number)
1180 {
1181         conf_t *conf = mddev->private;
1182         int err = 0;
1183         mdk_rdev_t *rdev;
1184         mirror_info_t *p = conf->mirrors+ number;
1185
1186         print_conf(conf);
1187         rdev = p->rdev;
1188         if (rdev) {
1189                 if (test_bit(In_sync, &rdev->flags) ||
1190                     atomic_read(&rdev->nr_pending)) {
1191                         err = -EBUSY;
1192                         goto abort;
1193                 }
1194                 /* Only remove faulty devices in recovery
1195                  * is not possible.
1196                  */
1197                 if (!test_bit(Faulty, &rdev->flags) &&
1198                     enough(conf)) {
1199                         err = -EBUSY;
1200                         goto abort;
1201                 }
1202                 p->rdev = NULL;
1203                 synchronize_rcu();
1204                 if (atomic_read(&rdev->nr_pending)) {
1205                         /* lost the race, try later */
1206                         err = -EBUSY;
1207                         p->rdev = rdev;
1208                         goto abort;
1209                 }
1210                 md_integrity_register(mddev);
1211         }
1212 abort:
1213
1214         print_conf(conf);
1215         return err;
1216 }
1217
1218
1219 static void end_sync_read(struct bio *bio, int error)
1220 {
1221         r10bio_t *r10_bio = bio->bi_private;
1222         conf_t *conf = r10_bio->mddev->private;
1223         int i,d;
1224
1225         for (i=0; i<conf->copies; i++)
1226                 if (r10_bio->devs[i].bio == bio)
1227                         break;
1228         BUG_ON(i == conf->copies);
1229         update_head_pos(i, r10_bio);
1230         d = r10_bio->devs[i].devnum;
1231
1232         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
1233                 set_bit(R10BIO_Uptodate, &r10_bio->state);
1234         else {
1235                 atomic_add(r10_bio->sectors,
1236                            &conf->mirrors[d].rdev->corrected_errors);
1237                 if (!test_bit(MD_RECOVERY_SYNC, &conf->mddev->recovery))
1238                         md_error(r10_bio->mddev,
1239                                  conf->mirrors[d].rdev);
1240         }
1241
1242         /* for reconstruct, we always reschedule after a read.
1243          * for resync, only after all reads
1244          */
1245         rdev_dec_pending(conf->mirrors[d].rdev, conf->mddev);
1246         if (test_bit(R10BIO_IsRecover, &r10_bio->state) ||
1247             atomic_dec_and_test(&r10_bio->remaining)) {
1248                 /* we have read all the blocks,
1249                  * do the comparison in process context in raid10d
1250                  */
1251                 reschedule_retry(r10_bio);
1252         }
1253 }
1254
1255 static void end_sync_write(struct bio *bio, int error)
1256 {
1257         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
1258         r10bio_t *r10_bio = bio->bi_private;
1259         mddev_t *mddev = r10_bio->mddev;
1260         conf_t *conf = mddev->private;
1261         int i,d;
1262
1263         for (i = 0; i < conf->copies; i++)
1264                 if (r10_bio->devs[i].bio == bio)
1265                         break;
1266         d = r10_bio->devs[i].devnum;
1267
1268         if (!uptodate)
1269                 md_error(mddev, conf->mirrors[d].rdev);
1270
1271         update_head_pos(i, r10_bio);
1272
1273         rdev_dec_pending(conf->mirrors[d].rdev, mddev);
1274         while (atomic_dec_and_test(&r10_bio->remaining)) {
1275                 if (r10_bio->master_bio == NULL) {
1276                         /* the primary of several recovery bios */
1277                         sector_t s = r10_bio->sectors;
1278                         put_buf(r10_bio);
1279                         md_done_sync(mddev, s, 1);
1280                         break;
1281                 } else {
1282                         r10bio_t *r10_bio2 = (r10bio_t *)r10_bio->master_bio;
1283                         put_buf(r10_bio);
1284                         r10_bio = r10_bio2;
1285                 }
1286         }
1287 }
1288
1289 /*
1290  * Note: sync and recover and handled very differently for raid10
1291  * This code is for resync.
1292  * For resync, we read through virtual addresses and read all blocks.
1293  * If there is any error, we schedule a write.  The lowest numbered
1294  * drive is authoritative.
1295  * However requests come for physical address, so we need to map.
1296  * For every physical address there are raid_disks/copies virtual addresses,
1297  * which is always are least one, but is not necessarly an integer.
1298  * This means that a physical address can span multiple chunks, so we may
1299  * have to submit multiple io requests for a single sync request.
1300  */
1301 /*
1302  * We check if all blocks are in-sync and only write to blocks that
1303  * aren't in sync
1304  */
1305 static void sync_request_write(mddev_t *mddev, r10bio_t *r10_bio)
1306 {
1307         conf_t *conf = mddev->private;
1308         int i, first;
1309         struct bio *tbio, *fbio;
1310
1311         atomic_set(&r10_bio->remaining, 1);
1312
1313         /* find the first device with a block */
1314         for (i=0; i<conf->copies; i++)
1315                 if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags))
1316                         break;
1317
1318         if (i == conf->copies)
1319                 goto done;
1320
1321         first = i;
1322         fbio = r10_bio->devs[i].bio;
1323
1324         /* now find blocks with errors */
1325         for (i=0 ; i < conf->copies ; i++) {
1326                 int  j, d;
1327                 int vcnt = r10_bio->sectors >> (PAGE_SHIFT-9);
1328
1329                 tbio = r10_bio->devs[i].bio;
1330
1331                 if (tbio->bi_end_io != end_sync_read)
1332                         continue;
1333                 if (i == first)
1334                         continue;
1335                 if (test_bit(BIO_UPTODATE, &r10_bio->devs[i].bio->bi_flags)) {
1336                         /* We know that the bi_io_vec layout is the same for
1337                          * both 'first' and 'i', so we just compare them.
1338                          * All vec entries are PAGE_SIZE;
1339                          */
1340                         for (j = 0; j < vcnt; j++)
1341                                 if (memcmp(page_address(fbio->bi_io_vec[j].bv_page),
1342                                            page_address(tbio->bi_io_vec[j].bv_page),
1343                                            PAGE_SIZE))
1344                                         break;
1345                         if (j == vcnt)
1346                                 continue;
1347                         mddev->resync_mismatches += r10_bio->sectors;
1348                 }
1349                 if (test_bit(MD_RECOVERY_CHECK, &mddev->recovery))
1350                         /* Don't fix anything. */
1351                         continue;
1352                 /* Ok, we need to write this bio
1353                  * First we need to fixup bv_offset, bv_len and
1354                  * bi_vecs, as the read request might have corrupted these
1355                  */
1356                 tbio->bi_vcnt = vcnt;
1357                 tbio->bi_size = r10_bio->sectors << 9;
1358                 tbio->bi_idx = 0;
1359                 tbio->bi_phys_segments = 0;
1360                 tbio->bi_flags &= ~(BIO_POOL_MASK - 1);
1361                 tbio->bi_flags |= 1 << BIO_UPTODATE;
1362                 tbio->bi_next = NULL;
1363                 tbio->bi_rw = WRITE;
1364                 tbio->bi_private = r10_bio;
1365                 tbio->bi_sector = r10_bio->devs[i].addr;
1366
1367                 for (j=0; j < vcnt ; j++) {
1368                         tbio->bi_io_vec[j].bv_offset = 0;
1369                         tbio->bi_io_vec[j].bv_len = PAGE_SIZE;
1370
1371                         memcpy(page_address(tbio->bi_io_vec[j].bv_page),
1372                                page_address(fbio->bi_io_vec[j].bv_page),
1373                                PAGE_SIZE);
1374                 }
1375                 tbio->bi_end_io = end_sync_write;
1376
1377                 d = r10_bio->devs[i].devnum;
1378                 atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1379                 atomic_inc(&r10_bio->remaining);
1380                 md_sync_acct(conf->mirrors[d].rdev->bdev, tbio->bi_size >> 9);
1381
1382                 tbio->bi_sector += conf->mirrors[d].rdev->data_offset;
1383                 tbio->bi_bdev = conf->mirrors[d].rdev->bdev;
1384                 generic_make_request(tbio);
1385         }
1386
1387 done:
1388         if (atomic_dec_and_test(&r10_bio->remaining)) {
1389                 md_done_sync(mddev, r10_bio->sectors, 1);
1390                 put_buf(r10_bio);
1391         }
1392 }
1393
1394 /*
1395  * Now for the recovery code.
1396  * Recovery happens across physical sectors.
1397  * We recover all non-is_sync drives by finding the virtual address of
1398  * each, and then choose a working drive that also has that virt address.
1399  * There is a separate r10_bio for each non-in_sync drive.
1400  * Only the first two slots are in use. The first for reading,
1401  * The second for writing.
1402  *
1403  */
1404
1405 static void recovery_request_write(mddev_t *mddev, r10bio_t *r10_bio)
1406 {
1407         conf_t *conf = mddev->private;
1408         int i, d;
1409         struct bio *bio, *wbio;
1410
1411
1412         /* move the pages across to the second bio
1413          * and submit the write request
1414          */
1415         bio = r10_bio->devs[0].bio;
1416         wbio = r10_bio->devs[1].bio;
1417         for (i=0; i < wbio->bi_vcnt; i++) {
1418                 struct page *p = bio->bi_io_vec[i].bv_page;
1419                 bio->bi_io_vec[i].bv_page = wbio->bi_io_vec[i].bv_page;
1420                 wbio->bi_io_vec[i].bv_page = p;
1421         }
1422         d = r10_bio->devs[1].devnum;
1423
1424         atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1425         md_sync_acct(conf->mirrors[d].rdev->bdev, wbio->bi_size >> 9);
1426         if (test_bit(R10BIO_Uptodate, &r10_bio->state))
1427                 generic_make_request(wbio);
1428         else
1429                 bio_endio(wbio, -EIO);
1430 }
1431
1432
1433 /*
1434  * Used by fix_read_error() to decay the per rdev read_errors.
1435  * We halve the read error count for every hour that has elapsed
1436  * since the last recorded read error.
1437  *
1438  */
1439 static void check_decay_read_errors(mddev_t *mddev, mdk_rdev_t *rdev)
1440 {
1441         struct timespec cur_time_mon;
1442         unsigned long hours_since_last;
1443         unsigned int read_errors = atomic_read(&rdev->read_errors);
1444
1445         ktime_get_ts(&cur_time_mon);
1446
1447         if (rdev->last_read_error.tv_sec == 0 &&
1448             rdev->last_read_error.tv_nsec == 0) {
1449                 /* first time we've seen a read error */
1450                 rdev->last_read_error = cur_time_mon;
1451                 return;
1452         }
1453
1454         hours_since_last = (cur_time_mon.tv_sec -
1455                             rdev->last_read_error.tv_sec) / 3600;
1456
1457         rdev->last_read_error = cur_time_mon;
1458
1459         /*
1460          * if hours_since_last is > the number of bits in read_errors
1461          * just set read errors to 0. We do this to avoid
1462          * overflowing the shift of read_errors by hours_since_last.
1463          */
1464         if (hours_since_last >= 8 * sizeof(read_errors))
1465                 atomic_set(&rdev->read_errors, 0);
1466         else
1467                 atomic_set(&rdev->read_errors, read_errors >> hours_since_last);
1468 }
1469
1470 /*
1471  * This is a kernel thread which:
1472  *
1473  *      1.      Retries failed read operations on working mirrors.
1474  *      2.      Updates the raid superblock when problems encounter.
1475  *      3.      Performs writes following reads for array synchronising.
1476  */
1477
1478 static void fix_read_error(conf_t *conf, mddev_t *mddev, r10bio_t *r10_bio)
1479 {
1480         int sect = 0; /* Offset from r10_bio->sector */
1481         int sectors = r10_bio->sectors;
1482         mdk_rdev_t*rdev;
1483         int max_read_errors = atomic_read(&mddev->max_corr_read_errors);
1484
1485         rcu_read_lock();
1486         {
1487                 int d = r10_bio->devs[r10_bio->read_slot].devnum;
1488                 char b[BDEVNAME_SIZE];
1489                 int cur_read_error_count = 0;
1490
1491                 rdev = rcu_dereference(conf->mirrors[d].rdev);
1492                 bdevname(rdev->bdev, b);
1493
1494                 if (test_bit(Faulty, &rdev->flags)) {
1495                         rcu_read_unlock();
1496                         /* drive has already been failed, just ignore any
1497                            more fix_read_error() attempts */
1498                         return;
1499                 }
1500
1501                 check_decay_read_errors(mddev, rdev);
1502                 atomic_inc(&rdev->read_errors);
1503                 cur_read_error_count = atomic_read(&rdev->read_errors);
1504                 if (cur_read_error_count > max_read_errors) {
1505                         rcu_read_unlock();
1506                         printk(KERN_NOTICE
1507                                "md/raid10:%s: %s: Raid device exceeded "
1508                                "read_error threshold "
1509                                "[cur %d:max %d]\n",
1510                                mdname(mddev),
1511                                b, cur_read_error_count, max_read_errors);
1512                         printk(KERN_NOTICE
1513                                "md/raid10:%s: %s: Failing raid "
1514                                "device\n", mdname(mddev), b);
1515                         md_error(mddev, conf->mirrors[d].rdev);
1516                         return;
1517                 }
1518         }
1519         rcu_read_unlock();
1520
1521         while(sectors) {
1522                 int s = sectors;
1523                 int sl = r10_bio->read_slot;
1524                 int success = 0;
1525                 int start;
1526
1527                 if (s > (PAGE_SIZE>>9))
1528                         s = PAGE_SIZE >> 9;
1529
1530                 rcu_read_lock();
1531                 do {
1532                         int d = r10_bio->devs[sl].devnum;
1533                         rdev = rcu_dereference(conf->mirrors[d].rdev);
1534                         if (rdev &&
1535                             test_bit(In_sync, &rdev->flags)) {
1536                                 atomic_inc(&rdev->nr_pending);
1537                                 rcu_read_unlock();
1538                                 success = sync_page_io(rdev->bdev,
1539                                                        r10_bio->devs[sl].addr +
1540                                                        sect + rdev->data_offset,
1541                                                        s<<9,
1542                                                        conf->tmppage, READ);
1543                                 rdev_dec_pending(rdev, mddev);
1544                                 rcu_read_lock();
1545                                 if (success)
1546                                         break;
1547                         }
1548                         sl++;
1549                         if (sl == conf->copies)
1550                                 sl = 0;
1551                 } while (!success && sl != r10_bio->read_slot);
1552                 rcu_read_unlock();
1553
1554                 if (!success) {
1555                         /* Cannot read from anywhere -- bye bye array */
1556                         int dn = r10_bio->devs[r10_bio->read_slot].devnum;
1557                         md_error(mddev, conf->mirrors[dn].rdev);
1558                         break;
1559                 }
1560
1561                 start = sl;
1562                 /* write it back and re-read */
1563                 rcu_read_lock();
1564                 while (sl != r10_bio->read_slot) {
1565                         char b[BDEVNAME_SIZE];
1566                         int d;
1567                         if (sl==0)
1568                                 sl = conf->copies;
1569                         sl--;
1570                         d = r10_bio->devs[sl].devnum;
1571                         rdev = rcu_dereference(conf->mirrors[d].rdev);
1572                         if (rdev &&
1573                             test_bit(In_sync, &rdev->flags)) {
1574                                 atomic_inc(&rdev->nr_pending);
1575                                 rcu_read_unlock();
1576                                 atomic_add(s, &rdev->corrected_errors);
1577                                 if (sync_page_io(rdev->bdev,
1578                                                  r10_bio->devs[sl].addr +
1579                                                  sect + rdev->data_offset,
1580                                                  s<<9, conf->tmppage, WRITE)
1581                                     == 0) {
1582                                         /* Well, this device is dead */
1583                                         printk(KERN_NOTICE
1584                                                "md/raid10:%s: read correction "
1585                                                "write failed"
1586                                                " (%d sectors at %llu on %s)\n",
1587                                                mdname(mddev), s,
1588                                                (unsigned long long)(sect+
1589                                                rdev->data_offset),
1590                                                bdevname(rdev->bdev, b));
1591                                         printk(KERN_NOTICE "md/raid10:%s: %s: failing "
1592                                                "drive\n",
1593                                                mdname(mddev),
1594                                                bdevname(rdev->bdev, b));
1595                                         md_error(mddev, rdev);
1596                                 }
1597                                 rdev_dec_pending(rdev, mddev);
1598                                 rcu_read_lock();
1599                         }
1600                 }
1601                 sl = start;
1602                 while (sl != r10_bio->read_slot) {
1603                         int d;
1604                         if (sl==0)
1605                                 sl = conf->copies;
1606                         sl--;
1607                         d = r10_bio->devs[sl].devnum;
1608                         rdev = rcu_dereference(conf->mirrors[d].rdev);
1609                         if (rdev &&
1610                             test_bit(In_sync, &rdev->flags)) {
1611                                 char b[BDEVNAME_SIZE];
1612                                 atomic_inc(&rdev->nr_pending);
1613                                 rcu_read_unlock();
1614                                 if (sync_page_io(rdev->bdev,
1615                                                  r10_bio->devs[sl].addr +
1616                                                  sect + rdev->data_offset,
1617                                                  s<<9, conf->tmppage,
1618                                                  READ) == 0) {
1619                                         /* Well, this device is dead */
1620                                         printk(KERN_NOTICE
1621                                                "md/raid10:%s: unable to read back "
1622                                                "corrected sectors"
1623                                                " (%d sectors at %llu on %s)\n",
1624                                                mdname(mddev), s,
1625                                                (unsigned long long)(sect+
1626                                                     rdev->data_offset),
1627                                                bdevname(rdev->bdev, b));
1628                                         printk(KERN_NOTICE "md/raid10:%s: %s: failing drive\n",
1629                                                mdname(mddev),
1630                                                bdevname(rdev->bdev, b));
1631
1632                                         md_error(mddev, rdev);
1633                                 } else {
1634                                         printk(KERN_INFO
1635                                                "md/raid10:%s: read error corrected"
1636                                                " (%d sectors at %llu on %s)\n",
1637                                                mdname(mddev), s,
1638                                                (unsigned long long)(sect+
1639                                                     rdev->data_offset),
1640                                                bdevname(rdev->bdev, b));
1641                                 }
1642
1643                                 rdev_dec_pending(rdev, mddev);
1644                                 rcu_read_lock();
1645                         }
1646                 }
1647                 rcu_read_unlock();
1648
1649                 sectors -= s;
1650                 sect += s;
1651         }
1652 }
1653
1654 static void raid10d(mddev_t *mddev)
1655 {
1656         r10bio_t *r10_bio;
1657         struct bio *bio;
1658         unsigned long flags;
1659         conf_t *conf = mddev->private;
1660         struct list_head *head = &conf->retry_list;
1661         int unplug=0;
1662         mdk_rdev_t *rdev;
1663
1664         md_check_recovery(mddev);
1665
1666         for (;;) {
1667                 char b[BDEVNAME_SIZE];
1668
1669                 unplug += flush_pending_writes(conf);
1670
1671                 spin_lock_irqsave(&conf->device_lock, flags);
1672                 if (list_empty(head)) {
1673                         spin_unlock_irqrestore(&conf->device_lock, flags);
1674                         break;
1675                 }
1676                 r10_bio = list_entry(head->prev, r10bio_t, retry_list);
1677                 list_del(head->prev);
1678                 conf->nr_queued--;
1679                 spin_unlock_irqrestore(&conf->device_lock, flags);
1680
1681                 mddev = r10_bio->mddev;
1682                 conf = mddev->private;
1683                 if (test_bit(R10BIO_IsSync, &r10_bio->state)) {
1684                         sync_request_write(mddev, r10_bio);
1685                         unplug = 1;
1686                 } else  if (test_bit(R10BIO_IsRecover, &r10_bio->state)) {
1687                         recovery_request_write(mddev, r10_bio);
1688                         unplug = 1;
1689                 } else {
1690                         int mirror;
1691                         /* we got a read error. Maybe the drive is bad.  Maybe just
1692                          * the block and we can fix it.
1693                          * We freeze all other IO, and try reading the block from
1694                          * other devices.  When we find one, we re-write
1695                          * and check it that fixes the read error.
1696                          * This is all done synchronously while the array is
1697                          * frozen.
1698                          */
1699                         if (mddev->ro == 0) {
1700                                 freeze_array(conf);
1701                                 fix_read_error(conf, mddev, r10_bio);
1702                                 unfreeze_array(conf);
1703                         }
1704
1705                         bio = r10_bio->devs[r10_bio->read_slot].bio;
1706                         r10_bio->devs[r10_bio->read_slot].bio =
1707                                 mddev->ro ? IO_BLOCKED : NULL;
1708                         mirror = read_balance(conf, r10_bio);
1709                         if (mirror == -1) {
1710                                 printk(KERN_ALERT "md/raid10:%s: %s: unrecoverable I/O"
1711                                        " read error for block %llu\n",
1712                                        mdname(mddev),
1713                                        bdevname(bio->bi_bdev,b),
1714                                        (unsigned long long)r10_bio->sector);
1715                                 raid_end_bio_io(r10_bio);
1716                                 bio_put(bio);
1717                         } else {
1718                                 const bool do_sync = bio_rw_flagged(r10_bio->master_bio, BIO_RW_SYNCIO);
1719                                 bio_put(bio);
1720                                 rdev = conf->mirrors[mirror].rdev;
1721                                 if (printk_ratelimit())
1722                                         printk(KERN_ERR "md/raid10:%s: %s: redirecting sector %llu to"
1723                                                " another mirror\n",
1724                                                mdname(mddev),
1725                                                bdevname(rdev->bdev,b),
1726                                                (unsigned long long)r10_bio->sector);
1727                                 bio = bio_clone(r10_bio->master_bio, GFP_NOIO);
1728                                 r10_bio->devs[r10_bio->read_slot].bio = bio;
1729                                 bio->bi_sector = r10_bio->devs[r10_bio->read_slot].addr
1730                                         + rdev->data_offset;
1731                                 bio->bi_bdev = rdev->bdev;
1732                                 bio->bi_rw = READ | (do_sync << BIO_RW_SYNCIO);
1733                                 bio->bi_private = r10_bio;
1734                                 bio->bi_end_io = raid10_end_read_request;
1735                                 unplug = 1;
1736                                 generic_make_request(bio);
1737                         }
1738                 }
1739                 cond_resched();
1740         }
1741         if (unplug)
1742                 unplug_slaves(mddev);
1743 }
1744
1745
1746 static int init_resync(conf_t *conf)
1747 {
1748         int buffs;
1749
1750         buffs = RESYNC_WINDOW / RESYNC_BLOCK_SIZE;
1751         BUG_ON(conf->r10buf_pool);
1752         conf->r10buf_pool = mempool_create(buffs, r10buf_pool_alloc, r10buf_pool_free, conf);
1753         if (!conf->r10buf_pool)
1754                 return -ENOMEM;
1755         conf->next_resync = 0;
1756         return 0;
1757 }
1758
1759 /*
1760  * perform a "sync" on one "block"
1761  *
1762  * We need to make sure that no normal I/O request - particularly write
1763  * requests - conflict with active sync requests.
1764  *
1765  * This is achieved by tracking pending requests and a 'barrier' concept
1766  * that can be installed to exclude normal IO requests.
1767  *
1768  * Resync and recovery are handled very differently.
1769  * We differentiate by looking at MD_RECOVERY_SYNC in mddev->recovery.
1770  *
1771  * For resync, we iterate over virtual addresses, read all copies,
1772  * and update if there are differences.  If only one copy is live,
1773  * skip it.
1774  * For recovery, we iterate over physical addresses, read a good
1775  * value for each non-in_sync drive, and over-write.
1776  *
1777  * So, for recovery we may have several outstanding complex requests for a
1778  * given address, one for each out-of-sync device.  We model this by allocating
1779  * a number of r10_bio structures, one for each out-of-sync device.
1780  * As we setup these structures, we collect all bio's together into a list
1781  * which we then process collectively to add pages, and then process again
1782  * to pass to generic_make_request.
1783  *
1784  * The r10_bio structures are linked using a borrowed master_bio pointer.
1785  * This link is counted in ->remaining.  When the r10_bio that points to NULL
1786  * has its remaining count decremented to 0, the whole complex operation
1787  * is complete.
1788  *
1789  */
1790
1791 static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster)
1792 {
1793         conf_t *conf = mddev->private;
1794         r10bio_t *r10_bio;
1795         struct bio *biolist = NULL, *bio;
1796         sector_t max_sector, nr_sectors;
1797         int disk;
1798         int i;
1799         int max_sync;
1800         int sync_blocks;
1801
1802         sector_t sectors_skipped = 0;
1803         int chunks_skipped = 0;
1804
1805         if (!conf->r10buf_pool)
1806                 if (init_resync(conf))
1807                         return 0;
1808
1809  skipped:
1810         max_sector = mddev->dev_sectors;
1811         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
1812                 max_sector = mddev->resync_max_sectors;
1813         if (sector_nr >= max_sector) {
1814                 /* If we aborted, we need to abort the
1815                  * sync on the 'current' bitmap chucks (there can
1816                  * be several when recovering multiple devices).
1817                  * as we may have started syncing it but not finished.
1818                  * We can find the current address in
1819                  * mddev->curr_resync, but for recovery,
1820                  * we need to convert that to several
1821                  * virtual addresses.
1822                  */
1823                 if (mddev->curr_resync < max_sector) { /* aborted */
1824                         if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery))
1825                                 bitmap_end_sync(mddev->bitmap, mddev->curr_resync,
1826                                                 &sync_blocks, 1);
1827                         else for (i=0; i<conf->raid_disks; i++) {
1828                                 sector_t sect =
1829                                         raid10_find_virt(conf, mddev->curr_resync, i);
1830                                 bitmap_end_sync(mddev->bitmap, sect,
1831                                                 &sync_blocks, 1);
1832                         }
1833                 } else /* completed sync */
1834                         conf->fullsync = 0;
1835
1836                 bitmap_close_sync(mddev->bitmap);
1837                 close_sync(conf);
1838                 *skipped = 1;
1839                 return sectors_skipped;
1840         }
1841         if (chunks_skipped >= conf->raid_disks) {
1842                 /* if there has been nothing to do on any drive,
1843                  * then there is nothing to do at all..
1844                  */
1845                 *skipped = 1;
1846                 return (max_sector - sector_nr) + sectors_skipped;
1847         }
1848
1849         if (max_sector > mddev->resync_max)
1850                 max_sector = mddev->resync_max; /* Don't do IO beyond here */
1851
1852         /* make sure whole request will fit in a chunk - if chunks
1853          * are meaningful
1854          */
1855         if (conf->near_copies < conf->raid_disks &&
1856             max_sector > (sector_nr | conf->chunk_mask))
1857                 max_sector = (sector_nr | conf->chunk_mask) + 1;
1858         /*
1859          * If there is non-resync activity waiting for us then
1860          * put in a delay to throttle resync.
1861          */
1862         if (!go_faster && conf->nr_waiting)
1863                 msleep_interruptible(1000);
1864
1865         /* Again, very different code for resync and recovery.
1866          * Both must result in an r10bio with a list of bios that
1867          * have bi_end_io, bi_sector, bi_bdev set,
1868          * and bi_private set to the r10bio.
1869          * For recovery, we may actually create several r10bios
1870          * with 2 bios in each, that correspond to the bios in the main one.
1871          * In this case, the subordinate r10bios link back through a
1872          * borrowed master_bio pointer, and the counter in the master
1873          * includes a ref from each subordinate.
1874          */
1875         /* First, we decide what to do and set ->bi_end_io
1876          * To end_sync_read if we want to read, and
1877          * end_sync_write if we will want to write.
1878          */
1879
1880         max_sync = RESYNC_PAGES << (PAGE_SHIFT-9);
1881         if (!test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
1882                 /* recovery... the complicated one */
1883                 int j, k;
1884                 r10_bio = NULL;
1885
1886                 for (i=0 ; i<conf->raid_disks; i++)
1887                         if (conf->mirrors[i].rdev &&
1888                             !test_bit(In_sync, &conf->mirrors[i].rdev->flags)) {
1889                                 int still_degraded = 0;
1890                                 /* want to reconstruct this device */
1891                                 r10bio_t *rb2 = r10_bio;
1892                                 sector_t sect = raid10_find_virt(conf, sector_nr, i);
1893                                 int must_sync;
1894                                 /* Unless we are doing a full sync, we only need
1895                                  * to recover the block if it is set in the bitmap
1896                                  */
1897                                 must_sync = bitmap_start_sync(mddev->bitmap, sect,
1898                                                               &sync_blocks, 1);
1899                                 if (sync_blocks < max_sync)
1900                                         max_sync = sync_blocks;
1901                                 if (!must_sync &&
1902                                     !conf->fullsync) {
1903                                         /* yep, skip the sync_blocks here, but don't assume
1904                                          * that there will never be anything to do here
1905                                          */
1906                                         chunks_skipped = -1;
1907                                         continue;
1908                                 }
1909
1910                                 r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
1911                                 raise_barrier(conf, rb2 != NULL);
1912                                 atomic_set(&r10_bio->remaining, 0);
1913
1914                                 r10_bio->master_bio = (struct bio*)rb2;
1915                                 if (rb2)
1916                                         atomic_inc(&rb2->remaining);
1917                                 r10_bio->mddev = mddev;
1918                                 set_bit(R10BIO_IsRecover, &r10_bio->state);
1919                                 r10_bio->sector = sect;
1920
1921                                 raid10_find_phys(conf, r10_bio);
1922
1923                                 /* Need to check if the array will still be
1924                                  * degraded
1925                                  */
1926                                 for (j=0; j<conf->raid_disks; j++)
1927                                         if (conf->mirrors[j].rdev == NULL ||
1928                                             test_bit(Faulty, &conf->mirrors[j].rdev->flags)) {
1929                                                 still_degraded = 1;
1930                                                 break;
1931                                         }
1932
1933                                 must_sync = bitmap_start_sync(mddev->bitmap, sect,
1934                                                               &sync_blocks, still_degraded);
1935
1936                                 for (j=0; j<conf->copies;j++) {
1937                                         int d = r10_bio->devs[j].devnum;
1938                                         if (conf->mirrors[d].rdev &&
1939                                             test_bit(In_sync, &conf->mirrors[d].rdev->flags)) {
1940                                                 /* This is where we read from */
1941                                                 bio = r10_bio->devs[0].bio;
1942                                                 bio->bi_next = biolist;
1943                                                 biolist = bio;
1944                                                 bio->bi_private = r10_bio;
1945                                                 bio->bi_end_io = end_sync_read;
1946                                                 bio->bi_rw = READ;
1947                                                 bio->bi_sector = r10_bio->devs[j].addr +
1948                                                         conf->mirrors[d].rdev->data_offset;
1949                                                 bio->bi_bdev = conf->mirrors[d].rdev->bdev;
1950                                                 atomic_inc(&conf->mirrors[d].rdev->nr_pending);
1951                                                 atomic_inc(&r10_bio->remaining);
1952                                                 /* and we write to 'i' */
1953
1954                                                 for (k=0; k<conf->copies; k++)
1955                                                         if (r10_bio->devs[k].devnum == i)
1956                                                                 break;
1957                                                 BUG_ON(k == conf->copies);
1958                                                 bio = r10_bio->devs[1].bio;
1959                                                 bio->bi_next = biolist;
1960                                                 biolist = bio;
1961                                                 bio->bi_private = r10_bio;
1962                                                 bio->bi_end_io = end_sync_write;
1963                                                 bio->bi_rw = WRITE;
1964                                                 bio->bi_sector = r10_bio->devs[k].addr +
1965                                                         conf->mirrors[i].rdev->data_offset;
1966                                                 bio->bi_bdev = conf->mirrors[i].rdev->bdev;
1967
1968                                                 r10_bio->devs[0].devnum = d;
1969                                                 r10_bio->devs[1].devnum = i;
1970
1971                                                 break;
1972                                         }
1973                                 }
1974                                 if (j == conf->copies) {
1975                                         /* Cannot recover, so abort the recovery */
1976                                         put_buf(r10_bio);
1977                                         if (rb2)
1978                                                 atomic_dec(&rb2->remaining);
1979                                         r10_bio = rb2;
1980                                         if (!test_and_set_bit(MD_RECOVERY_INTR,
1981                                                               &mddev->recovery))
1982                                                 printk(KERN_INFO "md/raid10:%s: insufficient "
1983                                                        "working devices for recovery.\n",
1984                                                        mdname(mddev));
1985                                         break;
1986                                 }
1987                         }
1988                 if (biolist == NULL) {
1989                         while (r10_bio) {
1990                                 r10bio_t *rb2 = r10_bio;
1991                                 r10_bio = (r10bio_t*) rb2->master_bio;
1992                                 rb2->master_bio = NULL;
1993                                 put_buf(rb2);
1994                         }
1995                         goto giveup;
1996                 }
1997         } else {
1998                 /* resync. Schedule a read for every block at this virt offset */
1999                 int count = 0;
2000
2001                 bitmap_cond_end_sync(mddev->bitmap, sector_nr);
2002
2003                 if (!bitmap_start_sync(mddev->bitmap, sector_nr,
2004                                        &sync_blocks, mddev->degraded) &&
2005                     !conf->fullsync && !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery)) {
2006                         /* We can skip this block */
2007                         *skipped = 1;
2008                         return sync_blocks + sectors_skipped;
2009                 }
2010                 if (sync_blocks < max_sync)
2011                         max_sync = sync_blocks;
2012                 r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
2013
2014                 r10_bio->mddev = mddev;
2015                 atomic_set(&r10_bio->remaining, 0);
2016                 raise_barrier(conf, 0);
2017                 conf->next_resync = sector_nr;
2018
2019                 r10_bio->master_bio = NULL;
2020                 r10_bio->sector = sector_nr;
2021                 set_bit(R10BIO_IsSync, &r10_bio->state);
2022                 raid10_find_phys(conf, r10_bio);
2023                 r10_bio->sectors = (sector_nr | conf->chunk_mask) - sector_nr +1;
2024
2025                 for (i=0; i<conf->copies; i++) {
2026                         int d = r10_bio->devs[i].devnum;
2027                         bio = r10_bio->devs[i].bio;
2028                         bio->bi_end_io = NULL;
2029                         clear_bit(BIO_UPTODATE, &bio->bi_flags);
2030                         if (conf->mirrors[d].rdev == NULL ||
2031                             test_bit(Faulty, &conf->mirrors[d].rdev->flags))
2032                                 continue;
2033                         atomic_inc(&conf->mirrors[d].rdev->nr_pending);
2034                         atomic_inc(&r10_bio->remaining);
2035                         bio->bi_next = biolist;
2036                         biolist = bio;
2037                         bio->bi_private = r10_bio;
2038                         bio->bi_end_io = end_sync_read;
2039                         bio->bi_rw = READ;
2040                         bio->bi_sector = r10_bio->devs[i].addr +
2041                                 conf->mirrors[d].rdev->data_offset;
2042                         bio->bi_bdev = conf->mirrors[d].rdev->bdev;
2043                         count++;
2044                 }
2045
2046                 if (count < 2) {
2047                         for (i=0; i<conf->copies; i++) {
2048                                 int d = r10_bio->devs[i].devnum;
2049                                 if (r10_bio->devs[i].bio->bi_end_io)
2050                                         rdev_dec_pending(conf->mirrors[d].rdev, mddev);
2051                         }
2052                         put_buf(r10_bio);
2053                         biolist = NULL;
2054                         goto giveup;
2055                 }
2056         }
2057
2058         for (bio = biolist; bio ; bio=bio->bi_next) {
2059
2060                 bio->bi_flags &= ~(BIO_POOL_MASK - 1);
2061                 if (bio->bi_end_io)
2062                         bio->bi_flags |= 1 << BIO_UPTODATE;
2063                 bio->bi_vcnt = 0;
2064                 bio->bi_idx = 0;
2065                 bio->bi_phys_segments = 0;
2066                 bio->bi_size = 0;
2067         }
2068
2069         nr_sectors = 0;
2070         if (sector_nr + max_sync < max_sector)
2071                 max_sector = sector_nr + max_sync;
2072         do {
2073                 struct page *page;
2074                 int len = PAGE_SIZE;
2075                 disk = 0;
2076                 if (sector_nr + (len>>9) > max_sector)
2077                         len = (max_sector - sector_nr) << 9;
2078                 if (len == 0)
2079                         break;
2080                 for (bio= biolist ; bio ; bio=bio->bi_next) {
2081                         page = bio->bi_io_vec[bio->bi_vcnt].bv_page;
2082                         if (bio_add_page(bio, page, len, 0) == 0) {
2083                                 /* stop here */
2084                                 struct bio *bio2;
2085                                 bio->bi_io_vec[bio->bi_vcnt].bv_page = page;
2086                                 for (bio2 = biolist; bio2 && bio2 != bio; bio2 = bio2->bi_next) {
2087                                         /* remove last page from this bio */
2088                                         bio2->bi_vcnt--;
2089                                         bio2->bi_size -= len;
2090                                         bio2->bi_flags &= ~(1<< BIO_SEG_VALID);
2091                                 }
2092                                 goto bio_full;
2093                         }
2094                         disk = i;
2095                 }
2096                 nr_sectors += len>>9;
2097                 sector_nr += len>>9;
2098         } while (biolist->bi_vcnt < RESYNC_PAGES);
2099  bio_full:
2100         r10_bio->sectors = nr_sectors;
2101
2102         while (biolist) {
2103                 bio = biolist;
2104                 biolist = biolist->bi_next;
2105
2106                 bio->bi_next = NULL;
2107                 r10_bio = bio->bi_private;
2108                 r10_bio->sectors = nr_sectors;
2109
2110                 if (bio->bi_end_io == end_sync_read) {
2111                         md_sync_acct(bio->bi_bdev, nr_sectors);
2112                         generic_make_request(bio);
2113                 }
2114         }
2115
2116         if (sectors_skipped)
2117                 /* pretend they weren't skipped, it makes
2118                  * no important difference in this case
2119                  */
2120                 md_done_sync(mddev, sectors_skipped, 1);
2121
2122         return sectors_skipped + nr_sectors;
2123  giveup:
2124         /* There is nowhere to write, so all non-sync
2125          * drives must be failed, so try the next chunk...
2126          */
2127         if (sector_nr + max_sync < max_sector)
2128                 max_sector = sector_nr + max_sync;
2129
2130         sectors_skipped += (max_sector - sector_nr);
2131         chunks_skipped ++;
2132         sector_nr = max_sector;
2133         goto skipped;
2134 }
2135
2136 static sector_t
2137 raid10_size(mddev_t *mddev, sector_t sectors, int raid_disks)
2138 {
2139         sector_t size;
2140         conf_t *conf = mddev->private;
2141
2142         if (!raid_disks)
2143                 raid_disks = conf->raid_disks;
2144         if (!sectors)
2145                 sectors = conf->dev_sectors;
2146
2147         size = sectors >> conf->chunk_shift;
2148         sector_div(size, conf->far_copies);
2149         size = size * raid_disks;
2150         sector_div(size, conf->near_copies);
2151
2152         return size << conf->chunk_shift;
2153 }
2154
2155
2156 static conf_t *setup_conf(mddev_t *mddev)
2157 {
2158         conf_t *conf = NULL;
2159         int nc, fc, fo;
2160         sector_t stride, size;
2161         int err = -EINVAL;
2162
2163         if (mddev->chunk_sectors < (PAGE_SIZE >> 9) ||
2164             !is_power_of_2(mddev->chunk_sectors)) {
2165                 printk(KERN_ERR "md/raid10:%s: chunk size must be "
2166                        "at least PAGE_SIZE(%ld) and be a power of 2.\n",
2167                        mdname(mddev), PAGE_SIZE);
2168                 goto out;
2169         }
2170
2171         nc = mddev->layout & 255;
2172         fc = (mddev->layout >> 8) & 255;
2173         fo = mddev->layout & (1<<16);
2174
2175         if ((nc*fc) <2 || (nc*fc) > mddev->raid_disks ||
2176             (mddev->layout >> 17)) {
2177                 printk(KERN_ERR "md/raid10:%s: unsupported raid10 layout: 0x%8x\n",
2178                        mdname(mddev), mddev->layout);
2179                 goto out;
2180         }
2181
2182         err = -ENOMEM;
2183         conf = kzalloc(sizeof(conf_t), GFP_KERNEL);
2184         if (!conf)
2185                 goto out;
2186
2187         conf->mirrors = kzalloc(sizeof(struct mirror_info)*mddev->raid_disks,
2188                                 GFP_KERNEL);
2189         if (!conf->mirrors)
2190                 goto out;
2191
2192         conf->tmppage = alloc_page(GFP_KERNEL);
2193         if (!conf->tmppage)
2194                 goto out;
2195
2196
2197         conf->raid_disks = mddev->raid_disks;
2198         conf->near_copies = nc;
2199         conf->far_copies = fc;
2200         conf->copies = nc*fc;
2201         conf->far_offset = fo;
2202         conf->chunk_mask = mddev->new_chunk_sectors - 1;
2203         conf->chunk_shift = ffz(~mddev->new_chunk_sectors);
2204
2205         conf->r10bio_pool = mempool_create(NR_RAID10_BIOS, r10bio_pool_alloc,
2206                                            r10bio_pool_free, conf);
2207         if (!conf->r10bio_pool)
2208                 goto out;
2209
2210         size = mddev->dev_sectors >> conf->chunk_shift;
2211         sector_div(size, fc);
2212         size = size * conf->raid_disks;
2213         sector_div(size, nc);
2214         /* 'size' is now the number of chunks in the array */
2215         /* calculate "used chunks per device" in 'stride' */
2216         stride = size * conf->copies;
2217
2218         /* We need to round up when dividing by raid_disks to
2219          * get the stride size.
2220          */
2221         stride += conf->raid_disks - 1;
2222         sector_div(stride, conf->raid_disks);
2223
2224         conf->dev_sectors = stride << conf->chunk_shift;
2225
2226         if (fo)
2227                 stride = 1;
2228         else
2229                 sector_div(stride, fc);
2230         conf->stride = stride << conf->chunk_shift;
2231
2232
2233         spin_lock_init(&conf->device_lock);
2234         INIT_LIST_HEAD(&conf->retry_list);
2235
2236         spin_lock_init(&conf->resync_lock);
2237         init_waitqueue_head(&conf->wait_barrier);
2238
2239         conf->thread = md_register_thread(raid10d, mddev, NULL);
2240         if (!conf->thread)
2241                 goto out;
2242
2243         conf->scale_disks = 0;
2244         conf->mddev = mddev;
2245         return conf;
2246
2247  out:
2248         printk(KERN_ERR "md/raid10:%s: couldn't allocate memory.\n",
2249                mdname(mddev));
2250         if (conf) {
2251                 if (conf->r10bio_pool)
2252                         mempool_destroy(conf->r10bio_pool);
2253                 kfree(conf->mirrors);
2254                 safe_put_page(conf->tmppage);
2255                 kfree(conf);
2256         }
2257         return ERR_PTR(err);
2258 }
2259
2260 static int run(mddev_t *mddev)
2261 {
2262         conf_t *conf;
2263         int i, disk_idx, chunk_size;
2264         mirror_info_t *disk;
2265         mdk_rdev_t *rdev;
2266         sector_t size;
2267
2268         /*
2269          * copy the already verified devices into our private RAID10
2270          * bookkeeping area. [whatever we allocate in run(),
2271          * should be freed in stop()]
2272          */
2273
2274         if (mddev->private == NULL) {
2275                 conf = setup_conf(mddev);
2276                 if (IS_ERR(conf))
2277                         return PTR_ERR(conf);
2278                 mddev->private = conf;
2279         }
2280         conf = mddev->private;
2281         if (!conf)
2282                 goto out;
2283
2284         mddev->queue->queue_lock = &conf->device_lock;
2285
2286         mddev->thread = conf->thread;
2287         conf->thread = NULL;
2288
2289         chunk_size = mddev->chunk_sectors << 9;
2290         blk_queue_io_min(mddev->queue, chunk_size);
2291         if (conf->raid_disks % conf->near_copies)
2292                 blk_queue_io_opt(mddev->queue, chunk_size * conf->raid_disks);
2293         else
2294                 blk_queue_io_opt(mddev->queue, chunk_size *
2295                                  (conf->raid_disks / conf->near_copies));
2296
2297         list_for_each_entry(rdev, &mddev->disks, same_set) {
2298                 disk_idx = rdev->raid_disk;
2299                 if (disk_idx >= conf->raid_disks
2300                     || disk_idx < 0)
2301                         continue;
2302                 if (conf->scale_disks) {
2303                         disk_idx *= conf->scale_disks;
2304                         rdev->raid_disk = disk_idx;
2305                         /* MOVE 'rd%d' link !! */
2306                 }
2307                 disk = conf->mirrors + disk_idx;
2308
2309                 disk->rdev = rdev;
2310                 disk_stack_limits(mddev->gendisk, rdev->bdev,
2311                                   rdev->data_offset << 9);
2312                 /* as we don't honour merge_bvec_fn, we must never risk
2313                  * violating it, so limit max_segments to 1 lying
2314                  * within a single page.
2315                  */
2316                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
2317                         blk_queue_max_segments(mddev->queue, 1);
2318                         blk_queue_segment_boundary(mddev->queue,
2319                                                    PAGE_CACHE_SIZE - 1);
2320                 }
2321
2322                 disk->head_position = 0;
2323         }
2324         /* need to check that every block has at least one working mirror */
2325         if (!enough(conf)) {
2326                 printk(KERN_ERR "md/raid10:%s: not enough operational mirrors.\n",
2327                        mdname(mddev));
2328                 goto out_free_conf;
2329         }
2330
2331         mddev->degraded = 0;
2332         for (i = 0; i < conf->raid_disks; i++) {
2333
2334                 disk = conf->mirrors + i;
2335
2336                 if (!disk->rdev ||
2337                     !test_bit(In_sync, &disk->rdev->flags)) {
2338                         disk->head_position = 0;
2339                         mddev->degraded++;
2340                         if (disk->rdev)
2341                                 conf->fullsync = 1;
2342                 }
2343         }
2344
2345         if (mddev->recovery_cp != MaxSector)
2346                 printk(KERN_NOTICE "md/raid10:%s: not clean"
2347                        " -- starting background reconstruction\n",
2348                        mdname(mddev));
2349         printk(KERN_INFO
2350                 "md/raid10:%s: active with %d out of %d devices\n",
2351                 mdname(mddev), conf->raid_disks - mddev->degraded,
2352                 conf->raid_disks);
2353         /*
2354          * Ok, everything is just fine now
2355          */
2356         mddev->dev_sectors = conf->dev_sectors;
2357         size = raid10_size(mddev, 0, 0);
2358         md_set_array_sectors(mddev, size);
2359         mddev->resync_max_sectors = size;
2360
2361         mddev->queue->unplug_fn = raid10_unplug;
2362         mddev->queue->backing_dev_info.congested_fn = raid10_congested;
2363         mddev->queue->backing_dev_info.congested_data = mddev;
2364
2365         /* Calculate max read-ahead size.
2366          * We need to readahead at least twice a whole stripe....
2367          * maybe...
2368          */
2369         {
2370                 int stripe = conf->raid_disks *
2371                         ((mddev->chunk_sectors << 9) / PAGE_SIZE);
2372                 stripe /= conf->near_copies;
2373                 if (mddev->queue->backing_dev_info.ra_pages < 2* stripe)
2374                         mddev->queue->backing_dev_info.ra_pages = 2* stripe;
2375         }
2376
2377         if (conf->near_copies < conf->raid_disks)
2378                 blk_queue_merge_bvec(mddev->queue, raid10_mergeable_bvec);
2379         md_integrity_register(mddev);
2380         return 0;
2381
2382 out_free_conf:
2383         if (conf->r10bio_pool)
2384                 mempool_destroy(conf->r10bio_pool);
2385         safe_put_page(conf->tmppage);
2386         kfree(conf->mirrors);
2387         kfree(conf);
2388         mddev->private = NULL;
2389         md_unregister_thread(mddev->thread);
2390 out:
2391         return -EIO;
2392 }
2393
2394 static int stop(mddev_t *mddev)
2395 {
2396         conf_t *conf = mddev->private;
2397
2398         raise_barrier(conf, 0);
2399         lower_barrier(conf);
2400
2401         md_unregister_thread(mddev->thread);
2402         mddev->thread = NULL;
2403         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
2404         if (conf->r10bio_pool)
2405                 mempool_destroy(conf->r10bio_pool);
2406         kfree(conf->mirrors);
2407         kfree(conf);
2408         mddev->private = NULL;
2409         return 0;
2410 }
2411
2412 static void raid10_quiesce(mddev_t *mddev, int state)
2413 {
2414         conf_t *conf = mddev->private;
2415
2416         switch(state) {
2417         case 1:
2418                 raise_barrier(conf, 0);
2419                 break;
2420         case 0:
2421                 lower_barrier(conf);
2422                 break;
2423         }
2424 }
2425
2426 static void *raid10_takeover_raid0(mddev_t *mddev)
2427 {
2428         mdk_rdev_t *rdev;
2429         conf_t *conf;
2430
2431         if (mddev->degraded > 0) {
2432                 printk(KERN_ERR "md/raid10:%s: Error: degraded raid0!\n",
2433                        mdname(mddev));
2434                 return ERR_PTR(-EINVAL);
2435         }
2436
2437         /* Update slot numbers to obtain
2438          * degraded raid10 with missing mirrors
2439          */
2440         list_for_each_entry(rdev, &mddev->disks, same_set) {
2441                 rdev->raid_disk *= 2;
2442         }
2443
2444         /* Set new parameters */
2445         mddev->new_level = 10;
2446         /* new layout: far_copies = 1, near_copies = 2 */
2447         mddev->new_layout = (1<<8) + 2;
2448         mddev->new_chunk_sectors = mddev->chunk_sectors;
2449         mddev->delta_disks = mddev->raid_disks;
2450         mddev->degraded = mddev->raid_disks;
2451         mddev->raid_disks *= 2;
2452         /* make sure it will be not marked as dirty */
2453         mddev->recovery_cp = MaxSector;
2454
2455         conf = setup_conf(mddev);
2456         conf->scale_disks = 2;
2457         return conf;
2458 }
2459
2460 static void *raid10_takeover(mddev_t *mddev)
2461 {
2462         struct raid0_private_data *raid0_priv;
2463
2464         /* raid10 can take over:
2465          *  raid0 - providing it has only two drives
2466          */
2467         if (mddev->level == 0) {
2468                 /* for raid0 takeover only one zone is supported */
2469                 raid0_priv = mddev->private;
2470                 if (raid0_priv->nr_strip_zones > 1) {
2471                         printk(KERN_ERR "md/raid10:%s: cannot takeover raid 0"
2472                                " with more than one zone.\n",
2473                                mdname(mddev));
2474                         return ERR_PTR(-EINVAL);
2475                 }
2476                 return raid10_takeover_raid0(mddev);
2477         }
2478         return ERR_PTR(-EINVAL);
2479 }
2480
2481 static struct mdk_personality raid10_personality =
2482 {
2483         .name           = "raid10",
2484         .level          = 10,
2485         .owner          = THIS_MODULE,
2486         .make_request   = make_request,
2487         .run            = run,
2488         .stop           = stop,
2489         .status         = status,
2490         .error_handler  = error,
2491         .hot_add_disk   = raid10_add_disk,
2492         .hot_remove_disk= raid10_remove_disk,
2493         .spare_active   = raid10_spare_active,
2494         .sync_request   = sync_request,
2495         .quiesce        = raid10_quiesce,
2496         .size           = raid10_size,
2497         .takeover       = raid10_takeover,
2498 };
2499
2500 static int __init raid_init(void)
2501 {
2502         return register_md_personality(&raid10_personality);
2503 }
2504
2505 static void raid_exit(void)
2506 {
2507         unregister_md_personality(&raid10_personality);
2508 }
2509
2510 module_init(raid_init);
2511 module_exit(raid_exit);
2512 MODULE_LICENSE("GPL");
2513 MODULE_DESCRIPTION("RAID10 (striped mirror) personality for MD");
2514 MODULE_ALIAS("md-personality-9"); /* RAID10 */
2515 MODULE_ALIAS("md-raid10");
2516 MODULE_ALIAS("md-level-10");