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 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _RAID5_H
 #define _RAID5_H
 
 #include <linux/raid/xor.h>
 #include <linux/dmaengine.h>
 #include <linux/local_lock.h>
 
 /*
  *
  * Each stripe contains one buffer per device.  Each buffer can be in
  * one of a number of states stored in "flags".  Changes between
  * these states happen *almost* exclusively under the protection of the
  * STRIPE_ACTIVE flag.  Some very specific changes can happen in bi_end_io, and
  * these are not protected by STRIPE_ACTIVE.
  *
  * The flag bits that are used to represent these states are:
  *   R5_UPTODATE and R5_LOCKED
  *
  * State Empty == !UPTODATE, !LOCK
  *        We have no data, and there is no active request
  * State Want == !UPTODATE, LOCK
  *        A read request is being submitted for this block
  * State Dirty == UPTODATE, LOCK
  *        Some new data is in this buffer, and it is being written out
  * State Clean == UPTODATE, !LOCK
  *        We have valid data which is the same as on disc
  *
  * The possible state transitions are:
  *
  *  Empty -> Want   - on read or write to get old data for  parity calc
  *  Empty -> Dirty  - on compute_parity to satisfy write/sync request.
  *  Empty -> Clean  - on compute_block when computing a block for failed drive
  *  Want  -> Empty  - on failed read
  *  Want  -> Clean  - on successful completion of read request
  *  Dirty -> Clean  - on successful completion of write request
  *  Dirty -> Clean  - on failed write
  *  Clean -> Dirty  - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
  *
  * The Want->Empty, Want->Clean, Dirty->Clean, transitions
  * all happen in b_end_io at interrupt time.
  * Each sets the Uptodate bit before releasing the Lock bit.
  * This leaves one multi-stage transition:
  *    Want->Dirty->Clean
  * This is safe because thinking that a Clean buffer is actually dirty
  * will at worst delay some action, and the stripe will be scheduled
  * for attention after the transition is complete.
  *
  * There is one possibility that is not covered by these states.  That
  * is if one drive has failed and there is a spare being rebuilt.  We
  * can't distinguish between a clean block that has been generated
  * from parity calculations, and a clean block that has been
  * successfully written to the spare ( or to parity when resyncing).
  * To distinguish these states we have a stripe bit STRIPE_INSYNC that
  * is set whenever a write is scheduled to the spare, or to the parity
  * disc if there is no spare.  A sync request clears this bit, and
  * when we find it set with no buffers locked, we know the sync is
  * complete.
  *
  * Buffers for the md device that arrive via make_request are attached
  * to the appropriate stripe in one of two lists linked on b_reqnext.
  * One list (bh_read) for read requests, one (bh_write) for write.
  * There should never be more than one buffer on the two lists
  * together, but we are not guaranteed of that so we allow for more.
  *
  * If a buffer is on the read list when the associated cache buffer is
  * Uptodate, the data is copied into the read buffer and it's b_end_io
  * routine is called.  This may happen in the end_request routine only
  * if the buffer has just successfully been read.  end_request should
  * remove the buffers from the list and then set the Uptodate bit on
  * the buffer.  Other threads may do this only if they first check
  * that the Uptodate bit is set.  Once they have checked that they may
  * take buffers off the read queue.
  *
  * When a buffer on the write list is committed for write it is copied
  * into the cache buffer, which is then marked dirty, and moved onto a
  * third list, the written list (bh_written).  Once both the parity
  * block and the cached buffer are successfully written, any buffer on
  * a written list can be returned with b_end_io.
  *
  * The write list and read list both act as fifos.  The read list,
  * write list and written list are protected by the device_lock.
  * The device_lock is only for list manipulations and will only be
  * held for a very short time.  It can be claimed from interrupts.
  *
  *
  * Stripes in the stripe cache can be on one of two lists (or on
  * neither).  The "inactive_list" contains stripes which are not
  * currently being used for any request.  They can freely be reused
  * for another stripe.  The "handle_list" contains stripes that need
  * to be handled in some way.  Both of these are fifo queues.  Each
  * stripe is also (potentially) linked to a hash bucket in the hash
  * table so that it can be found by sector number.  Stripes that are
  * not hashed must be on the inactive_list, and will normally be at
  * the front.  All stripes start life this way.
  *
  * The inactive_list, handle_list and hash bucket lists are all protected by the
  * device_lock.
  *  - stripes have a reference counter. If count==0, they are on a list.
  *  - If a stripe might need handling, STRIPE_HANDLE is set.
  *  - When refcount reaches zero, then if STRIPE_HANDLE it is put on
  *    handle_list else inactive_list
  *
  * This, combined with the fact that STRIPE_HANDLE is only ever
  * cleared while a stripe has a non-zero count means that if the
  * refcount is 0 and STRIPE_HANDLE is set, then it is on the
  * handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
  * the stripe is on inactive_list.
  *
  * The possible transitions are:
  *  activate an unhashed/inactive stripe (get_active_stripe())
  *     lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
  *  activate a hashed, possibly active stripe (get_active_stripe())
  *     lockdev check-hash if(!cnt++)unlink-stripe unlockdev
  *  attach a request to an active stripe (add_stripe_bh())
  *     lockdev attach-buffer unlockdev
  *  handle a stripe (handle_stripe())
  *     setSTRIPE_ACTIVE,  clrSTRIPE_HANDLE ...
  *      (lockdev check-buffers unlockdev) ..
  *      change-state ..
  *      record io/ops needed clearSTRIPE_ACTIVE schedule io/ops
  *  release an active stripe (release_stripe())
  *     lockdev if (!--cnt) { if  STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
  *
  * The refcount counts each thread that have activated the stripe,
  * plus raid5d if it is handling it, plus one for each active request
  * on a cached buffer, and plus one if the stripe is undergoing stripe
  * operations.
  *
  * The stripe operations are:
  * -copying data between the stripe cache and user application buffers
  * -computing blocks to save a disk access, or to recover a missing block
  * -updating the parity on a write operation (reconstruct write and
  *  read-modify-write)
  * -checking parity correctness
  * -running i/o to disk
  * These operations are carried out by raid5_run_ops which uses the async_tx
  * api to (optionally) offload operations to dedicated hardware engines.
  * When requesting an operation handle_stripe sets the pending bit for the
  * operation and increments the count.  raid5_run_ops is then run whenever
  * the count is non-zero.
  * There are some critical dependencies between the operations that prevent some
  * from being requested while another is in flight.
  * 1/ Parity check operations destroy the in cache version of the parity block,
  *    so we prevent parity dependent operations like writes and compute_blocks
  *    from starting while a check is in progress.  Some dma engines can perform
  *    the check without damaging the parity block, in these cases the parity
  *    block is re-marked up to date (assuming the check was successful) and is
  *    not re-read from disk.
  * 2/ When a write operation is requested we immediately lock the affected
  *    blocks, and mark them as not up to date.  This causes new read requests
  *    to be held off, as well as parity checks and compute block operations.
  * 3/ Once a compute block operation has been requested handle_stripe treats
  *    that block as if it is up to date.  raid5_run_ops guaruntees that any
  *    operation that is dependent on the compute block result is initiated after
  *    the compute block completes.
  */
 
 /*
  * Operations state - intermediate states that are visible outside of
  *   STRIPE_ACTIVE.
  * In general _idle indicates nothing is running, _run indicates a data
  * processing operation is active, and _result means the data processing result
  * is stable and can be acted upon.  For simple operations like biofill and
  * compute that only have an _idle and _run state they are indicated with
  * sh->state flags (STRIPE_BIOFILL_RUN and STRIPE_COMPUTE_RUN)
  */
 /**
  * enum check_states - handles syncing / repairing a stripe
  * @check_state_idle - check operations are quiesced
  * @check_state_run - check operation is running
  * @check_state_result - set outside lock when check result is valid
  * @check_state_compute_run - check failed and we are repairing
  * @check_state_compute_result - set outside lock when compute result is valid
  */
 enum check_states {
     check_state_idle = 0,
     check_state_run, /* xor parity check */
     check_state_run_q, /* q-parity check */
     check_state_run_pq, /* pq dual parity check */
     check_state_check_result,
     check_state_compute_run, /* parity repair */
     check_state_compute_result,
 };
 
 /**
  * enum reconstruct_states - handles writing or expanding a stripe
  */
 enum reconstruct_states {
     reconstruct_state_idle = 0,
     reconstruct_state_prexor_drain_run, /* prexor-write */
     reconstruct_state_drain_run,        /* write */
     reconstruct_state_run,          /* expand */
     reconstruct_state_prexor_drain_result,
     reconstruct_state_drain_result,
     reconstruct_state_result,
 };
 
 #define DEFAULT_STRIPE_SIZE 4096
 struct stripe_head {
     struct hlist_node   hash;
     struct list_head    lru;          /* inactive_list or handle_list */
     struct llist_node   release_list;
     struct r5conf       *raid_conf;
     short           generation; /* increments with every
                          * reshape */
     sector_t        sector;     /* sector of this row */
     short           pd_idx;     /* parity disk index */
     short           qd_idx;     /* 'Q' disk index for raid6 */
     short           ddf_layout;/* use DDF ordering to calculate Q */
     short           hash_lock_index;
     unsigned long       state;      /* state flags */
     atomic_t        count;        /* nr of active thread/requests */
     int         bm_seq; /* sequence number for bitmap flushes */
     int         disks;      /* disks in stripe */
     int         overwrite_disks; /* total overwrite disks in stripe,
                           * this is only checked when stripe
                           * has STRIPE_BATCH_READY
                           */
     enum check_states   check_state;
     enum reconstruct_states reconstruct_state;
     spinlock_t      stripe_lock;
     int         cpu;
     struct r5worker_group   *group;
 
     struct stripe_head  *batch_head; /* protected by stripe lock */
     spinlock_t      batch_lock; /* only header's lock is useful */
     struct list_head    batch_list; /* protected by head's batch lock*/
 
     union {
         struct r5l_io_unit  *log_io;
         struct ppl_io_unit  *ppl_io;
     };
 
     struct list_head    log_list;
     sector_t        log_start; /* first meta block on the journal */
     struct list_head    r5c; /* for r5c_cache->stripe_in_journal */
 
     struct page     *ppl_page; /* partial parity of this stripe */
     /**
      * struct stripe_operations
      * @target - STRIPE_OP_COMPUTE_BLK target
      * @target2 - 2nd compute target in the raid6 case
      * @zero_sum_result - P and Q verification flags
      * @request - async service request flags for raid_run_ops
      */
     struct stripe_operations {
         int              target, target2;
         enum sum_check_flags zero_sum_result;
     } ops;
 
 #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
     /* These pages will be used by bios in dev[i] */
     struct page **pages;
     int nr_pages;   /* page array size */
     int stripes_per_page;
 #endif
     struct r5dev {
         /* rreq and rvec are used for the replacement device when
          * writing data to both devices.
          */
         struct bio  req, rreq;
         struct bio_vec  vec, rvec;
         struct page *page, *orig_page;
         unsigned int    offset;     /* offset of the page */
         struct bio  *toread, *read, *towrite, *written;
         sector_t    sector;         /* sector of this page */
         unsigned long   flags;
         u32     log_checksum;
         unsigned short  write_hint;
     } dev[1]; /* allocated with extra space depending of RAID geometry */
 };
 
 /* stripe_head_state - collects and tracks the dynamic state of a stripe_head
  *     for handle_stripe.
  */
 struct stripe_head_state {
     /* 'syncing' means that we need to read all devices, either
      * to check/correct parity, or to reconstruct a missing device.
      * 'replacing' means we are replacing one or more drives and
      * the source is valid at this point so we don't need to
      * read all devices, just the replacement targets.
      */
     int syncing, expanding, expanded, replacing;
     int locked, uptodate, to_read, to_write, failed, written;
     int to_fill, compute, req_compute, non_overwrite;
     int injournal, just_cached;
     int failed_num[2];
     int p_failed, q_failed;
     int dec_preread_active;
     unsigned long ops_request;
 
     struct md_rdev *blocked_rdev;
     int handle_bad_blocks;
     int log_failed;
     int waiting_extra_page;
 };
 
 /* Flags for struct r5dev.flags */
 enum r5dev_flags {
     R5_UPTODATE,    /* page contains current data */
     R5_LOCKED,  /* IO has been submitted on "req" */
     R5_DOUBLE_LOCKED,/* Cannot clear R5_LOCKED until 2 writes complete */
     R5_OVERWRITE,   /* towrite covers whole page */
 /* and some that are internal to handle_stripe */
     R5_Insync,  /* rdev && rdev->in_sync at start */
     R5_Wantread,    /* want to schedule a read */
     R5_Wantwrite,
     R5_Overlap, /* There is a pending overlapping request
              * on this block */
     R5_ReadNoMerge, /* prevent bio from merging in block-layer */
     R5_ReadError,   /* seen a read error here recently */
     R5_ReWrite, /* have tried to over-write the readerror */
 
     R5_Expanded,    /* This block now has post-expand data */
     R5_Wantcompute, /* compute_block in progress treat as
              * uptodate
              */
     R5_Wantfill,    /* dev->toread contains a bio that needs
              * filling
              */
     R5_Wantdrain,   /* dev->towrite needs to be drained */
     R5_WantFUA, /* Write should be FUA */
     R5_SyncIO,  /* The IO is sync */
     R5_WriteError,  /* got a write error - need to record it */
     R5_MadeGood,    /* A bad block has been fixed by writing to it */
     R5_ReadRepl,    /* Will/did read from replacement rather than orig */
     R5_MadeGoodRepl,/* A bad block on the replacement device has been
              * fixed by writing to it */
     R5_NeedReplace, /* This device has a replacement which is not
              * up-to-date at this stripe. */
     R5_WantReplace, /* We need to update the replacement, we have read
              * data in, and now is a good time to write it out.
              */
     R5_Discard, /* Discard the stripe */
     R5_SkipCopy,    /* Don't copy data from bio to stripe cache */
     R5_InJournal,   /* data being written is in the journal device.
              * if R5_InJournal is set for parity pd_idx, all the
              * data and parity being written are in the journal
              * device
              */
     R5_OrigPageUPTDODATE,   /* with write back cache, we read old data into
                  * dev->orig_page for prexor. When this flag is
                  * set, orig_page contains latest data in the
                  * raid disk.
                  */
 };
 
 /*
  * Stripe state
  */
 enum {
     STRIPE_ACTIVE,
     STRIPE_HANDLE,
     STRIPE_SYNC_REQUESTED,
     STRIPE_SYNCING,
     STRIPE_INSYNC,
     STRIPE_REPLACED,
     STRIPE_PREREAD_ACTIVE,
     STRIPE_DELAYED,
     STRIPE_DEGRADED,
     STRIPE_BIT_DELAY,
     STRIPE_EXPANDING,
     STRIPE_EXPAND_SOURCE,
     STRIPE_EXPAND_READY,
     STRIPE_IO_STARTED,  /* do not count towards 'bypass_count' */
     STRIPE_FULL_WRITE,  /* all blocks are set to be overwritten */
     STRIPE_BIOFILL_RUN,
     STRIPE_COMPUTE_RUN,
     STRIPE_ON_UNPLUG_LIST,
     STRIPE_DISCARD,
     STRIPE_ON_RELEASE_LIST,
     STRIPE_BATCH_READY,
     STRIPE_BATCH_ERR,
     STRIPE_BITMAP_PENDING,  /* Being added to bitmap, don't add
                  * to batch yet.
                  */
     STRIPE_LOG_TRAPPED, /* trapped into log (see raid5-cache.c)
                  * this bit is used in two scenarios:
                  *
                  * 1. write-out phase
                  *  set in first entry of r5l_write_stripe
                  *  clear in second entry of r5l_write_stripe
                  *  used to bypass logic in handle_stripe
                  *
                  * 2. caching phase
                  *  set in r5c_try_caching_write()
                  *  clear when journal write is done
                  *  used to initiate r5c_cache_data()
                  *  also used to bypass logic in handle_stripe
                  */
     STRIPE_R5C_CACHING, /* the stripe is in caching phase
                  * see more detail in the raid5-cache.c
                  */
     STRIPE_R5C_PARTIAL_STRIPE,  /* in r5c cache (to-be/being handled or
                      * in conf->r5c_partial_stripe_list)
                      */
     STRIPE_R5C_FULL_STRIPE, /* in r5c cache (to-be/being handled or
                  * in conf->r5c_full_stripe_list)
                  */
     STRIPE_R5C_PREFLUSH,    /* need to flush journal device */
 };
 
 #define STRIPE_EXPAND_SYNC_FLAGS \
     ((1 << STRIPE_EXPAND_SOURCE) |\
     (1 << STRIPE_EXPAND_READY) |\
     (1 << STRIPE_EXPANDING) |\
     (1 << STRIPE_SYNC_REQUESTED))
 /*
  * Operation request flags
  */
 enum {
     STRIPE_OP_BIOFILL,
     STRIPE_OP_COMPUTE_BLK,
     STRIPE_OP_PREXOR,
     STRIPE_OP_BIODRAIN,
     STRIPE_OP_RECONSTRUCT,
     STRIPE_OP_CHECK,
     STRIPE_OP_PARTIAL_PARITY,
 };
 
 /*
  * RAID parity calculation preferences
  */
 enum {
     PARITY_DISABLE_RMW = 0,
     PARITY_ENABLE_RMW,
     PARITY_PREFER_RMW,
 };
 
 /*
  * Pages requested from set_syndrome_sources()
  */
 enum {
     SYNDROME_SRC_ALL,
     SYNDROME_SRC_WANT_DRAIN,
     SYNDROME_SRC_WRITTEN,
 };
 /*
  * Plugging:
  *
  * To improve write throughput, we need to delay the handling of some
  * stripes until there has been a chance that several write requests
  * for the one stripe have all been collected.
  * In particular, any write request that would require pre-reading
  * is put on a "delayed" queue until there are no stripes currently
  * in a pre-read phase.  Further, if the "delayed" queue is empty when
  * a stripe is put on it then we "plug" the queue and do not process it
  * until an unplug call is made. (the unplug_io_fn() is called).
  *
  * When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
  * it to the count of prereading stripes.
  * When write is initiated, or the stripe refcnt == 0 (just in case) we
  * clear the PREREAD_ACTIVE flag and decrement the count
  * Whenever the 'handle' queue is empty and the device is not plugged, we
  * move any strips from delayed to handle and clear the DELAYED flag and set
  * PREREAD_ACTIVE.
  * In stripe_handle, if we find pre-reading is necessary, we do it if
  * PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
  * HANDLE gets cleared if stripe_handle leaves nothing locked.
  */
 
 /* Note: disk_info.rdev can be set to NULL asynchronously by raid5_remove_disk.
  * There are three safe ways to access disk_info.rdev.
  * 1/ when holding mddev->reconfig_mutex
  * 2/ when resync/recovery/reshape is known to be happening - i.e. in code that
  *    is called as part of performing resync/recovery/reshape.
  * 3/ while holding rcu_read_lock(), use rcu_dereference to get the pointer
  *    and if it is non-NULL, increment rdev->nr_pending before dropping the RCU
  *    lock.
  * When .rdev is set to NULL, the nr_pending count checked again and if
  * it has been incremented, the pointer is put back in .rdev.
  */
 
 struct disk_info {
     struct md_rdev  __rcu *rdev;
     struct md_rdev  __rcu *replacement;
     struct page *extra_page; /* extra page to use in prexor */
 };
 
 /*
  * Stripe cache
  */
 
 #define NR_STRIPES      256
 
 #if PAGE_SIZE == DEFAULT_STRIPE_SIZE
 #define STRIPE_SIZE     PAGE_SIZE
 #define STRIPE_SHIFT        (PAGE_SHIFT - 9)
 #define STRIPE_SECTORS      (STRIPE_SIZE>>9)
 #endif
 
 #define IO_THRESHOLD        1
 #define BYPASS_THRESHOLD    1
 #define NR_HASH         (PAGE_SIZE / sizeof(struct hlist_head))
 #define HASH_MASK       (NR_HASH - 1)
 #define MAX_STRIPE_BATCH    8
 
 /* NOTE NR_STRIPE_HASH_LOCKS must remain below 64.
  * This is because we sometimes take all the spinlocks
  * and creating that much locking depth can cause
  * problems.
  */
 #define NR_STRIPE_HASH_LOCKS 8
 #define STRIPE_HASH_LOCKS_MASK (NR_STRIPE_HASH_LOCKS - 1)
 
 struct r5worker {
     struct work_struct work;
     struct r5worker_group *group;
     struct list_head temp_inactive_list[NR_STRIPE_HASH_LOCKS];
     bool working;
 };
 
 struct r5worker_group {
     struct list_head handle_list;
     struct list_head loprio_list;
     struct r5conf *conf;
     struct r5worker *workers;
     int stripes_cnt;
 };
 
 /*
  * r5c journal modes of the array: write-back or write-through.
  * write-through mode has identical behavior as existing log only
  * implementation.
  */
 enum r5c_journal_mode {
     R5C_JOURNAL_MODE_WRITE_THROUGH = 0,
     R5C_JOURNAL_MODE_WRITE_BACK = 1,
 };
 
 enum r5_cache_state {
     R5_INACTIVE_BLOCKED,    /* release of inactive stripes blocked,
                  * waiting for 25% to be free
                  */
     R5_ALLOC_MORE,      /* It might help to allocate another
                  * stripe.
                  */
     R5_DID_ALLOC,       /* A stripe was allocated, don't allocate
                  * more until at least one has been
                  * released.  This avoids flooding
                  * the cache.
                  */
     R5C_LOG_TIGHT,      /* log device space tight, need to
                  * prioritize stripes at last_checkpoint
                  */
     R5C_LOG_CRITICAL,   /* log device is running out of space,
                  * only process stripes that are already
                  * occupying the log
                  */
     R5C_EXTRA_PAGE_IN_USE,  /* a stripe is using disk_info.extra_page
                  * for prexor
                  */
 };
 
 #define PENDING_IO_MAX 512
 #define PENDING_IO_ONE_FLUSH 128
 struct r5pending_data {
     struct list_head sibling;
     sector_t sector; /* stripe sector */
     struct bio_list bios;
 };
 
 struct raid5_percpu {
     struct page *spare_page; /* Used when checking P/Q in raid6 */
     void        *scribble;  /* space for constructing buffer
                      * lists and performing address
                      * conversions
                      */
     int             scribble_obj_size;
     local_lock_t    lock;
 };
 
 struct r5conf {
     struct hlist_head   *stripe_hashtbl;
     /* only protect corresponding hash list and inactive_list */
     spinlock_t      hash_locks[NR_STRIPE_HASH_LOCKS];
     struct mddev        *mddev;
     int         chunk_sectors;
     int         level, algorithm, rmw_level;
     int         max_degraded;
     int         raid_disks;
     int         max_nr_stripes;
     int         min_nr_stripes;
 #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
     unsigned long   stripe_size;
     unsigned int    stripe_shift;
     unsigned long   stripe_sectors;
 #endif
 
     /* reshape_progress is the leading edge of a 'reshape'
      * It has value MaxSector when no reshape is happening
      * If delta_disks < 0, it is the last sector we started work on,
      * else is it the next sector to work on.
      */
     sector_t        reshape_progress;
     /* reshape_safe is the trailing edge of a reshape.  We know that
      * before (or after) this address, all reshape has completed.
      */
     sector_t        reshape_safe;
     int         previous_raid_disks;
     int         prev_chunk_sectors;
     int         prev_algo;
     short           generation; /* increments with every reshape */
     seqcount_spinlock_t gen_lock;   /* lock against generation changes */
     unsigned long       reshape_checkpoint; /* Time we last updated
                              * metadata */
     long long       min_offset_diff; /* minimum difference between
                           * data_offset and
                           * new_data_offset across all
                           * devices.  May be negative,
                           * but is closest to zero.
                           */
 
     struct list_head    handle_list; /* stripes needing handling */
     struct list_head    loprio_list; /* low priority stripes */
     struct list_head    hold_list; /* preread ready stripes */
     struct list_head    delayed_list; /* stripes that have plugged requests */
     struct list_head    bitmap_list; /* stripes delaying awaiting bitmap update */
     struct bio      *retry_read_aligned; /* currently retrying aligned bios   */
     unsigned int        retry_read_offset; /* sector offset into retry_read_aligned */
     struct bio      *retry_read_aligned_list; /* aligned bios retry list  */
     atomic_t        preread_active_stripes; /* stripes with scheduled io */
     atomic_t        active_aligned_reads;
     atomic_t        pending_full_writes; /* full write backlog */
     int         bypass_count; /* bypassed prereads */
     int         bypass_threshold; /* preread nice */
     int         skip_copy; /* Don't copy data from bio to stripe cache */
     struct list_head    *last_hold; /* detect hold_list promotions */
 
     atomic_t        reshape_stripes; /* stripes with pending writes for reshape */
     /* unfortunately we need two cache names as we temporarily have
      * two caches.
      */
     int         active_name;
     char            cache_name[2][32];
     struct kmem_cache   *slab_cache; /* for allocating stripes */
     struct mutex        cache_size_mutex; /* Protect changes to cache size */
 
     int         seq_flush, seq_write;
     int         quiesce;
 
     int         fullsync;  /* set to 1 if a full sync is needed,
                         * (fresh device added).
                         * Cleared when a sync completes.
                         */
     int         recovery_disabled;
     /* per cpu variables */
     struct raid5_percpu __percpu *percpu;
     int scribble_disks;
     int scribble_sectors;
     struct hlist_node node;
 
     /*
      * Free stripes pool
      */
     atomic_t        active_stripes;
     struct list_head    inactive_list[NR_STRIPE_HASH_LOCKS];
 
     atomic_t        r5c_cached_full_stripes;
     struct list_head    r5c_full_stripe_list;
     atomic_t        r5c_cached_partial_stripes;
     struct list_head    r5c_partial_stripe_list;
     atomic_t        r5c_flushing_full_stripes;
     atomic_t        r5c_flushing_partial_stripes;
 
     atomic_t        empty_inactive_list_nr;
     struct llist_head   released_stripes;
     wait_queue_head_t   wait_for_quiescent;
     wait_queue_head_t   wait_for_stripe;
     wait_queue_head_t   wait_for_overlap;
     unsigned long       cache_state;
     struct shrinker     shrinker;
     int         pool_size; /* number of disks in stripeheads in pool */
     spinlock_t      device_lock;
     struct disk_info    *disks;
     struct bio_set      bio_split;
 
     /* When taking over an array from a different personality, we store
      * the new thread here until we fully activate the array.
      */
     struct md_thread    *thread;
     struct list_head    temp_inactive_list[NR_STRIPE_HASH_LOCKS];
     struct r5worker_group   *worker_groups;
     int         group_cnt;
     int         worker_cnt_per_group;
     struct r5l_log      *log;
     void            *log_private;
 
     spinlock_t      pending_bios_lock;
     bool            batch_bio_dispatch;
     struct r5pending_data   *pending_data;
     struct list_head    free_list;
     struct list_head    pending_list;
     int         pending_data_cnt;
     struct r5pending_data   *next_pending_data;
 };
 
 #if PAGE_SIZE == DEFAULT_STRIPE_SIZE
 #define RAID5_STRIPE_SIZE(conf) STRIPE_SIZE
 #define RAID5_STRIPE_SHIFT(conf)    STRIPE_SHIFT
 #define RAID5_STRIPE_SECTORS(conf)  STRIPE_SECTORS
 #else
 #define RAID5_STRIPE_SIZE(conf) ((conf)->stripe_size)
 #define RAID5_STRIPE_SHIFT(conf)    ((conf)->stripe_shift)
 #define RAID5_STRIPE_SECTORS(conf)  ((conf)->stripe_sectors)
 #endif
 
 /* bio's attached to a stripe+device for I/O are linked together in bi_sector
  * order without overlap.  There may be several bio's per stripe+device, and
  * a bio could span several devices.
  * When walking this list for a particular stripe+device, we must never proceed
  * beyond a bio that extends past this device, as the next bio might no longer
  * be valid.
  * This function is used to determine the 'next' bio in the list, given the
  * sector of the current stripe+device
  */
 static inline struct bio *r5_next_bio(struct r5conf *conf, struct bio *bio, sector_t sector)
 {
     if (bio_end_sector(bio) < sector + RAID5_STRIPE_SECTORS(conf))
         return bio->bi_next;
     else
         return NULL;
 }
 
 /*
  * Our supported algorithms
  */
 #define ALGORITHM_LEFT_ASYMMETRIC   0 /* Rotating Parity N with Data Restart */
 #define ALGORITHM_RIGHT_ASYMMETRIC  1 /* Rotating Parity 0 with Data Restart */
 #define ALGORITHM_LEFT_SYMMETRIC    2 /* Rotating Parity N with Data Continuation */
 #define ALGORITHM_RIGHT_SYMMETRIC   3 /* Rotating Parity 0 with Data Continuation */
 
 /* Define non-rotating (raid4) algorithms.  These allow
  * conversion of raid4 to raid5.
  */
 #define ALGORITHM_PARITY_0      4 /* P or P,Q are initial devices */
 #define ALGORITHM_PARITY_N      5 /* P or P,Q are final devices. */
 
 /* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
  * Firstly, the exact positioning of the parity block is slightly
  * different between the 'LEFT_*' modes of md and the "_N_*" modes
  * of DDF.
  * Secondly, or order of datablocks over which the Q syndrome is computed
  * is different.
  * Consequently we have different layouts for DDF/raid6 than md/raid6.
  * These layouts are from the DDFv1.2 spec.
  * Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
  * leaves RLQ=3 as 'Vendor Specific'
  */
 
 #define ALGORITHM_ROTATING_ZERO_RESTART 8 /* DDF PRL=6 RLQ=1 */
 #define ALGORITHM_ROTATING_N_RESTART    9 /* DDF PRL=6 RLQ=2 */
 #define ALGORITHM_ROTATING_N_CONTINUE   10 /*DDF PRL=6 RLQ=3 */
 
 /* For every RAID5 algorithm we define a RAID6 algorithm
  * with exactly the same layout for data and parity, and
  * with the Q block always on the last device (N-1).
  * This allows trivial conversion from RAID5 to RAID6
  */
 #define ALGORITHM_LEFT_ASYMMETRIC_6 16
 #define ALGORITHM_RIGHT_ASYMMETRIC_6    17
 #define ALGORITHM_LEFT_SYMMETRIC_6  18
 #define ALGORITHM_RIGHT_SYMMETRIC_6 19
 #define ALGORITHM_PARITY_0_6        20
 #define ALGORITHM_PARITY_N_6        ALGORITHM_PARITY_N
 
 static inline int algorithm_valid_raid5(int layout)
 {
     return (layout >= 0) &&
         (layout <= 5);
 }
 static inline int algorithm_valid_raid6(int layout)
 {
     return (layout >= 0 && layout <= 5)
         ||
         (layout >= 8 && layout <= 10)
         ||
         (layout >= 16 && layout <= 20);
 }
 
 static inline int algorithm_is_DDF(int layout)
 {
     return layout >= 8 && layout <= 10;
 }
 
 #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
 /*
  * Return offset of the corresponding page for r5dev.
  */
 static inline int raid5_get_page_offset(struct stripe_head *sh, int disk_idx)
 {
     return (disk_idx % sh->stripes_per_page) * RAID5_STRIPE_SIZE(sh->raid_conf);
 }
 
 /*
  * Return corresponding page address for r5dev.
  */
 static inline struct page *
 raid5_get_dev_page(struct stripe_head *sh, int disk_idx)
 {
     return sh->pages[disk_idx / sh->stripes_per_page];
 }
 #endif
 
 extern void md_raid5_kick_device(struct r5conf *conf);
 extern int raid5_set_cache_size(struct mddev *mddev, int size);
 extern sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous);
 extern void raid5_release_stripe(struct stripe_head *sh);
 extern sector_t raid5_compute_sector(struct r5conf *conf, sector_t r_sector,
                      int previous, int *dd_idx,
                      struct stripe_head *sh);
 extern struct stripe_head *
 raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
             bool previous, bool noblock, bool noquiesce);
 extern int raid5_calc_degraded(struct r5conf *conf);
 extern int r5c_journal_mode_set(struct mddev *mddev, int journal_mode);
 #endif

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