linux/drivers/md/raid5.h
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   1#ifndef _RAID5_H
   2#define _RAID5_H
   3
   4#include <linux/raid/xor.h>
   5#include <linux/dmaengine.h>
   6
   7/*
   8 *
   9 * Each stripe contains one buffer per device.  Each buffer can be in
  10 * one of a number of states stored in "flags".  Changes between
  11 * these states happen *almost* exclusively under the protection of the
  12 * STRIPE_ACTIVE flag.  Some very specific changes can happen in bi_end_io, and
  13 * these are not protected by STRIPE_ACTIVE.
  14 *
  15 * The flag bits that are used to represent these states are:
  16 *   R5_UPTODATE and R5_LOCKED
  17 *
  18 * State Empty == !UPTODATE, !LOCK
  19 *        We have no data, and there is no active request
  20 * State Want == !UPTODATE, LOCK
  21 *        A read request is being submitted for this block
  22 * State Dirty == UPTODATE, LOCK
  23 *        Some new data is in this buffer, and it is being written out
  24 * State Clean == UPTODATE, !LOCK
  25 *        We have valid data which is the same as on disc
  26 *
  27 * The possible state transitions are:
  28 *
  29 *  Empty -> Want   - on read or write to get old data for  parity calc
  30 *  Empty -> Dirty  - on compute_parity to satisfy write/sync request.
  31 *  Empty -> Clean  - on compute_block when computing a block for failed drive
  32 *  Want  -> Empty  - on failed read
  33 *  Want  -> Clean  - on successful completion of read request
  34 *  Dirty -> Clean  - on successful completion of write request
  35 *  Dirty -> Clean  - on failed write
  36 *  Clean -> Dirty  - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
  37 *
  38 * The Want->Empty, Want->Clean, Dirty->Clean, transitions
  39 * all happen in b_end_io at interrupt time.
  40 * Each sets the Uptodate bit before releasing the Lock bit.
  41 * This leaves one multi-stage transition:
  42 *    Want->Dirty->Clean
  43 * This is safe because thinking that a Clean buffer is actually dirty
  44 * will at worst delay some action, and the stripe will be scheduled
  45 * for attention after the transition is complete.
  46 *
  47 * There is one possibility that is not covered by these states.  That
  48 * is if one drive has failed and there is a spare being rebuilt.  We
  49 * can't distinguish between a clean block that has been generated
  50 * from parity calculations, and a clean block that has been
  51 * successfully written to the spare ( or to parity when resyncing).
  52 * To distinguish these states we have a stripe bit STRIPE_INSYNC that
  53 * is set whenever a write is scheduled to the spare, or to the parity
  54 * disc if there is no spare.  A sync request clears this bit, and
  55 * when we find it set with no buffers locked, we know the sync is
  56 * complete.
  57 *
  58 * Buffers for the md device that arrive via make_request are attached
  59 * to the appropriate stripe in one of two lists linked on b_reqnext.
  60 * One list (bh_read) for read requests, one (bh_write) for write.
  61 * There should never be more than one buffer on the two lists
  62 * together, but we are not guaranteed of that so we allow for more.
  63 *
  64 * If a buffer is on the read list when the associated cache buffer is
  65 * Uptodate, the data is copied into the read buffer and it's b_end_io
  66 * routine is called.  This may happen in the end_request routine only
  67 * if the buffer has just successfully been read.  end_request should
  68 * remove the buffers from the list and then set the Uptodate bit on
  69 * the buffer.  Other threads may do this only if they first check
  70 * that the Uptodate bit is set.  Once they have checked that they may
  71 * take buffers off the read queue.
  72 *
  73 * When a buffer on the write list is committed for write it is copied
  74 * into the cache buffer, which is then marked dirty, and moved onto a
  75 * third list, the written list (bh_written).  Once both the parity
  76 * block and the cached buffer are successfully written, any buffer on
  77 * a written list can be returned with b_end_io.
  78 *
  79 * The write list and read list both act as fifos.  The read list,
  80 * write list and written list are protected by the device_lock.
  81 * The device_lock is only for list manipulations and will only be
  82 * held for a very short time.  It can be claimed from interrupts.
  83 *
  84 *
  85 * Stripes in the stripe cache can be on one of two lists (or on
  86 * neither).  The "inactive_list" contains stripes which are not
  87 * currently being used for any request.  They can freely be reused
  88 * for another stripe.  The "handle_list" contains stripes that need
  89 * to be handled in some way.  Both of these are fifo queues.  Each
  90 * stripe is also (potentially) linked to a hash bucket in the hash
  91 * table so that it can be found by sector number.  Stripes that are
  92 * not hashed must be on the inactive_list, and will normally be at
  93 * the front.  All stripes start life this way.
  94 *
  95 * The inactive_list, handle_list and hash bucket lists are all protected by the
  96 * device_lock.
  97 *  - stripes have a reference counter. If count==0, they are on a list.
  98 *  - If a stripe might need handling, STRIPE_HANDLE is set.
  99 *  - When refcount reaches zero, then if STRIPE_HANDLE it is put on
 100 *    handle_list else inactive_list
 101 *
 102 * This, combined with the fact that STRIPE_HANDLE is only ever
 103 * cleared while a stripe has a non-zero count means that if the
 104 * refcount is 0 and STRIPE_HANDLE is set, then it is on the
 105 * handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
 106 * the stripe is on inactive_list.
 107 *
 108 * The possible transitions are:
 109 *  activate an unhashed/inactive stripe (get_active_stripe())
 110 *     lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
 111 *  activate a hashed, possibly active stripe (get_active_stripe())
 112 *     lockdev check-hash if(!cnt++)unlink-stripe unlockdev
 113 *  attach a request to an active stripe (add_stripe_bh())
 114 *     lockdev attach-buffer unlockdev
 115 *  handle a stripe (handle_stripe())
 116 *     setSTRIPE_ACTIVE,  clrSTRIPE_HANDLE ...
 117 *              (lockdev check-buffers unlockdev) ..
 118 *              change-state ..
 119 *              record io/ops needed clearSTRIPE_ACTIVE schedule io/ops
 120 *  release an active stripe (release_stripe())
 121 *     lockdev if (!--cnt) { if  STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
 122 *
 123 * The refcount counts each thread that have activated the stripe,
 124 * plus raid5d if it is handling it, plus one for each active request
 125 * on a cached buffer, and plus one if the stripe is undergoing stripe
 126 * operations.
 127 *
 128 * The stripe operations are:
 129 * -copying data between the stripe cache and user application buffers
 130 * -computing blocks to save a disk access, or to recover a missing block
 131 * -updating the parity on a write operation (reconstruct write and
 132 *  read-modify-write)
 133 * -checking parity correctness
 134 * -running i/o to disk
 135 * These operations are carried out by raid5_run_ops which uses the async_tx
 136 * api to (optionally) offload operations to dedicated hardware engines.
 137 * When requesting an operation handle_stripe sets the pending bit for the
 138 * operation and increments the count.  raid5_run_ops is then run whenever
 139 * the count is non-zero.
 140 * There are some critical dependencies between the operations that prevent some
 141 * from being requested while another is in flight.
 142 * 1/ Parity check operations destroy the in cache version of the parity block,
 143 *    so we prevent parity dependent operations like writes and compute_blocks
 144 *    from starting while a check is in progress.  Some dma engines can perform
 145 *    the check without damaging the parity block, in these cases the parity
 146 *    block is re-marked up to date (assuming the check was successful) and is
 147 *    not re-read from disk.
 148 * 2/ When a write operation is requested we immediately lock the affected
 149 *    blocks, and mark them as not up to date.  This causes new read requests
 150 *    to be held off, as well as parity checks and compute block operations.
 151 * 3/ Once a compute block operation has been requested handle_stripe treats
 152 *    that block as if it is up to date.  raid5_run_ops guaruntees that any
 153 *    operation that is dependent on the compute block result is initiated after
 154 *    the compute block completes.
 155 */
 156
 157/*
 158 * Operations state - intermediate states that are visible outside of
 159 *   STRIPE_ACTIVE.
 160 * In general _idle indicates nothing is running, _run indicates a data
 161 * processing operation is active, and _result means the data processing result
 162 * is stable and can be acted upon.  For simple operations like biofill and
 163 * compute that only have an _idle and _run state they are indicated with
 164 * sh->state flags (STRIPE_BIOFILL_RUN and STRIPE_COMPUTE_RUN)
 165 */
 166/**
 167 * enum check_states - handles syncing / repairing a stripe
 168 * @check_state_idle - check operations are quiesced
 169 * @check_state_run - check operation is running
 170 * @check_state_result - set outside lock when check result is valid
 171 * @check_state_compute_run - check failed and we are repairing
 172 * @check_state_compute_result - set outside lock when compute result is valid
 173 */
 174enum check_states {
 175        check_state_idle = 0,
 176        check_state_run, /* xor parity check */
 177        check_state_run_q, /* q-parity check */
 178        check_state_run_pq, /* pq dual parity check */
 179        check_state_check_result,
 180        check_state_compute_run, /* parity repair */
 181        check_state_compute_result,
 182};
 183
 184/**
 185 * enum reconstruct_states - handles writing or expanding a stripe
 186 */
 187enum reconstruct_states {
 188        reconstruct_state_idle = 0,
 189        reconstruct_state_prexor_drain_run,     /* prexor-write */
 190        reconstruct_state_drain_run,            /* write */
 191        reconstruct_state_run,                  /* expand */
 192        reconstruct_state_prexor_drain_result,
 193        reconstruct_state_drain_result,
 194        reconstruct_state_result,
 195};
 196
 197struct stripe_head {
 198        struct hlist_node       hash;
 199        struct list_head        lru;          /* inactive_list or handle_list */
 200        struct llist_node       release_list;
 201        struct r5conf           *raid_conf;
 202        short                   generation;     /* increments with every
 203                                                 * reshape */
 204        sector_t                sector;         /* sector of this row */
 205        short                   pd_idx;         /* parity disk index */
 206        short                   qd_idx;         /* 'Q' disk index for raid6 */
 207        short                   ddf_layout;/* use DDF ordering to calculate Q */
 208        short                   hash_lock_index;
 209        unsigned long           state;          /* state flags */
 210        atomic_t                count;        /* nr of active thread/requests */
 211        int                     bm_seq; /* sequence number for bitmap flushes */
 212        int                     disks;          /* disks in stripe */
 213        int                     overwrite_disks; /* total overwrite disks in stripe,
 214                                                  * this is only checked when stripe
 215                                                  * has STRIPE_BATCH_READY
 216                                                  */
 217        enum check_states       check_state;
 218        enum reconstruct_states reconstruct_state;
 219        spinlock_t              stripe_lock;
 220        int                     cpu;
 221        struct r5worker_group   *group;
 222
 223        struct stripe_head      *batch_head; /* protected by stripe lock */
 224        spinlock_t              batch_lock; /* only header's lock is useful */
 225        struct list_head        batch_list; /* protected by head's batch lock*/
 226        /**
 227         * struct stripe_operations
 228         * @target - STRIPE_OP_COMPUTE_BLK target
 229         * @target2 - 2nd compute target in the raid6 case
 230         * @zero_sum_result - P and Q verification flags
 231         * @request - async service request flags for raid_run_ops
 232         */
 233        struct stripe_operations {
 234                int                  target, target2;
 235                enum sum_check_flags zero_sum_result;
 236        } ops;
 237        struct r5dev {
 238                /* rreq and rvec are used for the replacement device when
 239                 * writing data to both devices.
 240                 */
 241                struct bio      req, rreq;
 242                struct bio_vec  vec, rvec;
 243                struct page     *page, *orig_page;
 244                struct bio      *toread, *read, *towrite, *written;
 245                sector_t        sector;                 /* sector of this page */
 246                unsigned long   flags;
 247        } dev[1]; /* allocated with extra space depending of RAID geometry */
 248};
 249
 250/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
 251 *     for handle_stripe.
 252 */
 253struct stripe_head_state {
 254        /* 'syncing' means that we need to read all devices, either
 255         * to check/correct parity, or to reconstruct a missing device.
 256         * 'replacing' means we are replacing one or more drives and
 257         * the source is valid at this point so we don't need to
 258         * read all devices, just the replacement targets.
 259         */
 260        int syncing, expanding, expanded, replacing;
 261        int locked, uptodate, to_read, to_write, failed, written;
 262        int to_fill, compute, req_compute, non_overwrite;
 263        int failed_num[2];
 264        int p_failed, q_failed;
 265        int dec_preread_active;
 266        unsigned long ops_request;
 267
 268        struct bio_list return_bi;
 269        struct md_rdev *blocked_rdev;
 270        int handle_bad_blocks;
 271};
 272
 273/* Flags for struct r5dev.flags */
 274enum r5dev_flags {
 275        R5_UPTODATE,    /* page contains current data */
 276        R5_LOCKED,      /* IO has been submitted on "req" */
 277        R5_DOUBLE_LOCKED,/* Cannot clear R5_LOCKED until 2 writes complete */
 278        R5_OVERWRITE,   /* towrite covers whole page */
 279/* and some that are internal to handle_stripe */
 280        R5_Insync,      /* rdev && rdev->in_sync at start */
 281        R5_Wantread,    /* want to schedule a read */
 282        R5_Wantwrite,
 283        R5_Overlap,     /* There is a pending overlapping request
 284                         * on this block */
 285        R5_ReadNoMerge, /* prevent bio from merging in block-layer */
 286        R5_ReadError,   /* seen a read error here recently */
 287        R5_ReWrite,     /* have tried to over-write the readerror */
 288
 289        R5_Expanded,    /* This block now has post-expand data */
 290        R5_Wantcompute, /* compute_block in progress treat as
 291                         * uptodate
 292                         */
 293        R5_Wantfill,    /* dev->toread contains a bio that needs
 294                         * filling
 295                         */
 296        R5_Wantdrain,   /* dev->towrite needs to be drained */
 297        R5_WantFUA,     /* Write should be FUA */
 298        R5_SyncIO,      /* The IO is sync */
 299        R5_WriteError,  /* got a write error - need to record it */
 300        R5_MadeGood,    /* A bad block has been fixed by writing to it */
 301        R5_ReadRepl,    /* Will/did read from replacement rather than orig */
 302        R5_MadeGoodRepl,/* A bad block on the replacement device has been
 303                         * fixed by writing to it */
 304        R5_NeedReplace, /* This device has a replacement which is not
 305                         * up-to-date at this stripe. */
 306        R5_WantReplace, /* We need to update the replacement, we have read
 307                         * data in, and now is a good time to write it out.
 308                         */
 309        R5_Discard,     /* Discard the stripe */
 310        R5_SkipCopy,    /* Don't copy data from bio to stripe cache */
 311};
 312
 313/*
 314 * Stripe state
 315 */
 316enum {
 317        STRIPE_ACTIVE,
 318        STRIPE_HANDLE,
 319        STRIPE_SYNC_REQUESTED,
 320        STRIPE_SYNCING,
 321        STRIPE_INSYNC,
 322        STRIPE_REPLACED,
 323        STRIPE_PREREAD_ACTIVE,
 324        STRIPE_DELAYED,
 325        STRIPE_DEGRADED,
 326        STRIPE_BIT_DELAY,
 327        STRIPE_EXPANDING,
 328        STRIPE_EXPAND_SOURCE,
 329        STRIPE_EXPAND_READY,
 330        STRIPE_IO_STARTED,      /* do not count towards 'bypass_count' */
 331        STRIPE_FULL_WRITE,      /* all blocks are set to be overwritten */
 332        STRIPE_BIOFILL_RUN,
 333        STRIPE_COMPUTE_RUN,
 334        STRIPE_OPS_REQ_PENDING,
 335        STRIPE_ON_UNPLUG_LIST,
 336        STRIPE_DISCARD,
 337        STRIPE_ON_RELEASE_LIST,
 338        STRIPE_BATCH_READY,
 339        STRIPE_BATCH_ERR,
 340        STRIPE_BITMAP_PENDING,  /* Being added to bitmap, don't add
 341                                 * to batch yet.
 342                                 */
 343};
 344
 345#define STRIPE_EXPAND_SYNC_FLAGS \
 346        ((1 << STRIPE_EXPAND_SOURCE) |\
 347        (1 << STRIPE_EXPAND_READY) |\
 348        (1 << STRIPE_EXPANDING) |\
 349        (1 << STRIPE_SYNC_REQUESTED))
 350/*
 351 * Operation request flags
 352 */
 353enum {
 354        STRIPE_OP_BIOFILL,
 355        STRIPE_OP_COMPUTE_BLK,
 356        STRIPE_OP_PREXOR,
 357        STRIPE_OP_BIODRAIN,
 358        STRIPE_OP_RECONSTRUCT,
 359        STRIPE_OP_CHECK,
 360};
 361
 362/*
 363 * RAID parity calculation preferences
 364 */
 365enum {
 366        PARITY_DISABLE_RMW = 0,
 367        PARITY_ENABLE_RMW,
 368        PARITY_PREFER_RMW,
 369};
 370
 371/*
 372 * Pages requested from set_syndrome_sources()
 373 */
 374enum {
 375        SYNDROME_SRC_ALL,
 376        SYNDROME_SRC_WANT_DRAIN,
 377        SYNDROME_SRC_WRITTEN,
 378};
 379/*
 380 * Plugging:
 381 *
 382 * To improve write throughput, we need to delay the handling of some
 383 * stripes until there has been a chance that several write requests
 384 * for the one stripe have all been collected.
 385 * In particular, any write request that would require pre-reading
 386 * is put on a "delayed" queue until there are no stripes currently
 387 * in a pre-read phase.  Further, if the "delayed" queue is empty when
 388 * a stripe is put on it then we "plug" the queue and do not process it
 389 * until an unplug call is made. (the unplug_io_fn() is called).
 390 *
 391 * When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
 392 * it to the count of prereading stripes.
 393 * When write is initiated, or the stripe refcnt == 0 (just in case) we
 394 * clear the PREREAD_ACTIVE flag and decrement the count
 395 * Whenever the 'handle' queue is empty and the device is not plugged, we
 396 * move any strips from delayed to handle and clear the DELAYED flag and set
 397 * PREREAD_ACTIVE.
 398 * In stripe_handle, if we find pre-reading is necessary, we do it if
 399 * PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
 400 * HANDLE gets cleared if stripe_handle leaves nothing locked.
 401 */
 402
 403struct disk_info {
 404        struct md_rdev  *rdev, *replacement;
 405};
 406
 407/* NOTE NR_STRIPE_HASH_LOCKS must remain below 64.
 408 * This is because we sometimes take all the spinlocks
 409 * and creating that much locking depth can cause
 410 * problems.
 411 */
 412#define NR_STRIPE_HASH_LOCKS 8
 413#define STRIPE_HASH_LOCKS_MASK (NR_STRIPE_HASH_LOCKS - 1)
 414
 415struct r5worker {
 416        struct work_struct work;
 417        struct r5worker_group *group;
 418        struct list_head temp_inactive_list[NR_STRIPE_HASH_LOCKS];
 419        bool working;
 420};
 421
 422struct r5worker_group {
 423        struct list_head handle_list;
 424        struct r5conf *conf;
 425        struct r5worker *workers;
 426        int stripes_cnt;
 427};
 428
 429struct r5conf {
 430        struct hlist_head       *stripe_hashtbl;
 431        /* only protect corresponding hash list and inactive_list */
 432        spinlock_t              hash_locks[NR_STRIPE_HASH_LOCKS];
 433        struct mddev            *mddev;
 434        int                     chunk_sectors;
 435        int                     level, algorithm, rmw_level;
 436        int                     max_degraded;
 437        int                     raid_disks;
 438        int                     max_nr_stripes;
 439        int                     min_nr_stripes;
 440
 441        /* reshape_progress is the leading edge of a 'reshape'
 442         * It has value MaxSector when no reshape is happening
 443         * If delta_disks < 0, it is the last sector we started work on,
 444         * else is it the next sector to work on.
 445         */
 446        sector_t                reshape_progress;
 447        /* reshape_safe is the trailing edge of a reshape.  We know that
 448         * before (or after) this address, all reshape has completed.
 449         */
 450        sector_t                reshape_safe;
 451        int                     previous_raid_disks;
 452        int                     prev_chunk_sectors;
 453        int                     prev_algo;
 454        short                   generation; /* increments with every reshape */
 455        seqcount_t              gen_lock;       /* lock against generation changes */
 456        unsigned long           reshape_checkpoint; /* Time we last updated
 457                                                     * metadata */
 458        long long               min_offset_diff; /* minimum difference between
 459                                                  * data_offset and
 460                                                  * new_data_offset across all
 461                                                  * devices.  May be negative,
 462                                                  * but is closest to zero.
 463                                                  */
 464
 465        struct list_head        handle_list; /* stripes needing handling */
 466        struct list_head        hold_list; /* preread ready stripes */
 467        struct list_head        delayed_list; /* stripes that have plugged requests */
 468        struct list_head        bitmap_list; /* stripes delaying awaiting bitmap update */
 469        struct bio              *retry_read_aligned; /* currently retrying aligned bios   */
 470        struct bio              *retry_read_aligned_list; /* aligned bios retry list  */
 471        atomic_t                preread_active_stripes; /* stripes with scheduled io */
 472        atomic_t                active_aligned_reads;
 473        atomic_t                pending_full_writes; /* full write backlog */
 474        int                     bypass_count; /* bypassed prereads */
 475        int                     bypass_threshold; /* preread nice */
 476        int                     skip_copy; /* Don't copy data from bio to stripe cache */
 477        struct list_head        *last_hold; /* detect hold_list promotions */
 478
 479        /* bios to have bi_end_io called after metadata is synced */
 480        struct bio_list         return_bi;
 481
 482        atomic_t                reshape_stripes; /* stripes with pending writes for reshape */
 483        /* unfortunately we need two cache names as we temporarily have
 484         * two caches.
 485         */
 486        int                     active_name;
 487        char                    cache_name[2][32];
 488        struct kmem_cache       *slab_cache; /* for allocating stripes */
 489        struct mutex            cache_size_mutex; /* Protect changes to cache size */
 490
 491        int                     seq_flush, seq_write;
 492        int                     quiesce;
 493
 494        int                     fullsync;  /* set to 1 if a full sync is needed,
 495                                            * (fresh device added).
 496                                            * Cleared when a sync completes.
 497                                            */
 498        int                     recovery_disabled;
 499        /* per cpu variables */
 500        struct raid5_percpu {
 501                struct page     *spare_page; /* Used when checking P/Q in raid6 */
 502                struct flex_array *scribble;   /* space for constructing buffer
 503                                              * lists and performing address
 504                                              * conversions
 505                                              */
 506        } __percpu *percpu;
 507#ifdef CONFIG_HOTPLUG_CPU
 508        struct notifier_block   cpu_notify;
 509#endif
 510
 511        /*
 512         * Free stripes pool
 513         */
 514        atomic_t                active_stripes;
 515        struct list_head        inactive_list[NR_STRIPE_HASH_LOCKS];
 516        atomic_t                empty_inactive_list_nr;
 517        struct llist_head       released_stripes;
 518        wait_queue_head_t       wait_for_quiescent;
 519        wait_queue_head_t       wait_for_stripe[NR_STRIPE_HASH_LOCKS];
 520        wait_queue_head_t       wait_for_overlap;
 521        unsigned long           cache_state;
 522#define R5_INACTIVE_BLOCKED     1       /* release of inactive stripes blocked,
 523                                         * waiting for 25% to be free
 524                                         */
 525#define R5_ALLOC_MORE           2       /* It might help to allocate another
 526                                         * stripe.
 527                                         */
 528#define R5_DID_ALLOC            4       /* A stripe was allocated, don't allocate
 529                                         * more until at least one has been
 530                                         * released.  This avoids flooding
 531                                         * the cache.
 532                                         */
 533        struct shrinker         shrinker;
 534        int                     pool_size; /* number of disks in stripeheads in pool */
 535        spinlock_t              device_lock;
 536        struct disk_info        *disks;
 537
 538        /* When taking over an array from a different personality, we store
 539         * the new thread here until we fully activate the array.
 540         */
 541        struct md_thread        *thread;
 542        struct list_head        temp_inactive_list[NR_STRIPE_HASH_LOCKS];
 543        struct r5worker_group   *worker_groups;
 544        int                     group_cnt;
 545        int                     worker_cnt_per_group;
 546};
 547
 548
 549/*
 550 * Our supported algorithms
 551 */
 552#define ALGORITHM_LEFT_ASYMMETRIC       0 /* Rotating Parity N with Data Restart */
 553#define ALGORITHM_RIGHT_ASYMMETRIC      1 /* Rotating Parity 0 with Data Restart */
 554#define ALGORITHM_LEFT_SYMMETRIC        2 /* Rotating Parity N with Data Continuation */
 555#define ALGORITHM_RIGHT_SYMMETRIC       3 /* Rotating Parity 0 with Data Continuation */
 556
 557/* Define non-rotating (raid4) algorithms.  These allow
 558 * conversion of raid4 to raid5.
 559 */
 560#define ALGORITHM_PARITY_0              4 /* P or P,Q are initial devices */
 561#define ALGORITHM_PARITY_N              5 /* P or P,Q are final devices. */
 562
 563/* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
 564 * Firstly, the exact positioning of the parity block is slightly
 565 * different between the 'LEFT_*' modes of md and the "_N_*" modes
 566 * of DDF.
 567 * Secondly, or order of datablocks over which the Q syndrome is computed
 568 * is different.
 569 * Consequently we have different layouts for DDF/raid6 than md/raid6.
 570 * These layouts are from the DDFv1.2 spec.
 571 * Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
 572 * leaves RLQ=3 as 'Vendor Specific'
 573 */
 574
 575#define ALGORITHM_ROTATING_ZERO_RESTART 8 /* DDF PRL=6 RLQ=1 */
 576#define ALGORITHM_ROTATING_N_RESTART    9 /* DDF PRL=6 RLQ=2 */
 577#define ALGORITHM_ROTATING_N_CONTINUE   10 /*DDF PRL=6 RLQ=3 */
 578
 579/* For every RAID5 algorithm we define a RAID6 algorithm
 580 * with exactly the same layout for data and parity, and
 581 * with the Q block always on the last device (N-1).
 582 * This allows trivial conversion from RAID5 to RAID6
 583 */
 584#define ALGORITHM_LEFT_ASYMMETRIC_6     16
 585#define ALGORITHM_RIGHT_ASYMMETRIC_6    17
 586#define ALGORITHM_LEFT_SYMMETRIC_6      18
 587#define ALGORITHM_RIGHT_SYMMETRIC_6     19
 588#define ALGORITHM_PARITY_0_6            20
 589#define ALGORITHM_PARITY_N_6            ALGORITHM_PARITY_N
 590
 591static inline int algorithm_valid_raid5(int layout)
 592{
 593        return (layout >= 0) &&
 594                (layout <= 5);
 595}
 596static inline int algorithm_valid_raid6(int layout)
 597{
 598        return (layout >= 0 && layout <= 5)
 599                ||
 600                (layout >= 8 && layout <= 10)
 601                ||
 602                (layout >= 16 && layout <= 20);
 603}
 604
 605static inline int algorithm_is_DDF(int layout)
 606{
 607        return layout >= 8 && layout <= 10;
 608}
 609
 610extern void md_raid5_kick_device(struct r5conf *conf);
 611extern int raid5_set_cache_size(struct mddev *mddev, int size);
 612#endif
 613