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[/] [test_project/] [trunk/] [linux_sd_driver/] [include/] [linux/] [raid/] [raid5.h] - Blame information for rev 62

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1 62 marcus.erl
#ifndef _RAID5_H
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#define _RAID5_H
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#include <linux/raid/md.h>
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#include <linux/raid/xor.h>
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/*
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 *
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 * Each stripe contains one buffer per disc.  Each buffer can be in
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 * one of a number of states stored in "flags".  Changes between
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 * these states happen *almost* exclusively under a per-stripe
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 * spinlock.  Some very specific changes can happen in bi_end_io, and
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 * these are not protected by the spin lock.
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 *
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 * The flag bits that are used to represent these states are:
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 *   R5_UPTODATE and R5_LOCKED
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 *
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 * State Empty == !UPTODATE, !LOCK
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 *        We have no data, and there is no active request
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 * State Want == !UPTODATE, LOCK
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 *        A read request is being submitted for this block
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 * State Dirty == UPTODATE, LOCK
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 *        Some new data is in this buffer, and it is being written out
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 * State Clean == UPTODATE, !LOCK
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 *        We have valid data which is the same as on disc
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 *
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 * The possible state transitions are:
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 *
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 *  Empty -> Want   - on read or write to get old data for  parity calc
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 *  Empty -> Dirty  - on compute_parity to satisfy write/sync request.(RECONSTRUCT_WRITE)
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 *  Empty -> Clean  - on compute_block when computing a block for failed drive
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 *  Want  -> Empty  - on failed read
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 *  Want  -> Clean  - on successful completion of read request
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 *  Dirty -> Clean  - on successful completion of write request
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 *  Dirty -> Clean  - on failed write
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 *  Clean -> Dirty  - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW)
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 *
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 * The Want->Empty, Want->Clean, Dirty->Clean, transitions
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 * all happen in b_end_io at interrupt time.
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 * Each sets the Uptodate bit before releasing the Lock bit.
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 * This leaves one multi-stage transition:
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 *    Want->Dirty->Clean
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 * This is safe because thinking that a Clean buffer is actually dirty
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 * will at worst delay some action, and the stripe will be scheduled
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 * for attention after the transition is complete.
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 *
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 * There is one possibility that is not covered by these states.  That
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 * is if one drive has failed and there is a spare being rebuilt.  We
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 * can't distinguish between a clean block that has been generated
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 * from parity calculations, and a clean block that has been
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 * successfully written to the spare ( or to parity when resyncing).
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 * To distingush these states we have a stripe bit STRIPE_INSYNC that
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 * is set whenever a write is scheduled to the spare, or to the parity
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 * disc if there is no spare.  A sync request clears this bit, and
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 * when we find it set with no buffers locked, we know the sync is
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 * complete.
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 *
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 * Buffers for the md device that arrive via make_request are attached
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 * to the appropriate stripe in one of two lists linked on b_reqnext.
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 * One list (bh_read) for read requests, one (bh_write) for write.
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 * There should never be more than one buffer on the two lists
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 * together, but we are not guaranteed of that so we allow for more.
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 *
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 * If a buffer is on the read list when the associated cache buffer is
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 * Uptodate, the data is copied into the read buffer and it's b_end_io
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 * routine is called.  This may happen in the end_request routine only
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 * if the buffer has just successfully been read.  end_request should
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 * remove the buffers from the list and then set the Uptodate bit on
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 * the buffer.  Other threads may do this only if they first check
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 * that the Uptodate bit is set.  Once they have checked that they may
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 * take buffers off the read queue.
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 *
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 * When a buffer on the write list is committed for write it is copied
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 * into the cache buffer, which is then marked dirty, and moved onto a
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 * third list, the written list (bh_written).  Once both the parity
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 * block and the cached buffer are successfully written, any buffer on
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 * a written list can be returned with b_end_io.
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 *
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 * The write list and read list both act as fifos.  The read list is
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 * protected by the device_lock.  The write and written lists are
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 * protected by the stripe lock.  The device_lock, which can be
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 * claimed while the stipe lock is held, is only for list
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 * manipulations and will only be held for a very short time.  It can
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 * be claimed from interrupts.
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 *
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 *
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 * Stripes in the stripe cache can be on one of two lists (or on
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 * neither).  The "inactive_list" contains stripes which are not
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 * currently being used for any request.  They can freely be reused
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 * for another stripe.  The "handle_list" contains stripes that need
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 * to be handled in some way.  Both of these are fifo queues.  Each
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 * stripe is also (potentially) linked to a hash bucket in the hash
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 * table so that it can be found by sector number.  Stripes that are
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 * not hashed must be on the inactive_list, and will normally be at
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 * the front.  All stripes start life this way.
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 *
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 * The inactive_list, handle_list and hash bucket lists are all protected by the
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 * device_lock.
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 *  - stripes on the inactive_list never have their stripe_lock held.
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 *  - stripes have a reference counter. If count==0, they are on a list.
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 *  - If a stripe might need handling, STRIPE_HANDLE is set.
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 *  - When refcount reaches zero, then if STRIPE_HANDLE it is put on
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 *    handle_list else inactive_list
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 *
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 * This, combined with the fact that STRIPE_HANDLE is only ever
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 * cleared while a stripe has a non-zero count means that if the
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 * refcount is 0 and STRIPE_HANDLE is set, then it is on the
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 * handle_list and if recount is 0 and STRIPE_HANDLE is not set, then
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 * the stripe is on inactive_list.
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 *
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 * The possible transitions are:
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 *  activate an unhashed/inactive stripe (get_active_stripe())
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 *     lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev
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 *  activate a hashed, possibly active stripe (get_active_stripe())
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 *     lockdev check-hash if(!cnt++)unlink-stripe unlockdev
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 *  attach a request to an active stripe (add_stripe_bh())
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 *     lockdev attach-buffer unlockdev
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 *  handle a stripe (handle_stripe())
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 *     lockstripe clrSTRIPE_HANDLE ...
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 *              (lockdev check-buffers unlockdev) ..
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 *              change-state ..
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 *              record io/ops needed unlockstripe schedule io/ops
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 *  release an active stripe (release_stripe())
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 *     lockdev if (!--cnt) { if  STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev
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 *
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 * The refcount counts each thread that have activated the stripe,
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 * plus raid5d if it is handling it, plus one for each active request
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 * on a cached buffer, and plus one if the stripe is undergoing stripe
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 * operations.
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 *
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 * Stripe operations are performed outside the stripe lock,
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 * the stripe operations are:
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 * -copying data between the stripe cache and user application buffers
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 * -computing blocks to save a disk access, or to recover a missing block
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 * -updating the parity on a write operation (reconstruct write and
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 *  read-modify-write)
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 * -checking parity correctness
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 * -running i/o to disk
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 * These operations are carried out by raid5_run_ops which uses the async_tx
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 * api to (optionally) offload operations to dedicated hardware engines.
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 * When requesting an operation handle_stripe sets the pending bit for the
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 * operation and increments the count.  raid5_run_ops is then run whenever
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 * the count is non-zero.
144
 * There are some critical dependencies between the operations that prevent some
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 * from being requested while another is in flight.
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 * 1/ Parity check operations destroy the in cache version of the parity block,
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 *    so we prevent parity dependent operations like writes and compute_blocks
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 *    from starting while a check is in progress.  Some dma engines can perform
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 *    the check without damaging the parity block, in these cases the parity
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 *    block is re-marked up to date (assuming the check was successful) and is
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 *    not re-read from disk.
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 * 2/ When a write operation is requested we immediately lock the affected
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 *    blocks, and mark them as not up to date.  This causes new read requests
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 *    to be held off, as well as parity checks and compute block operations.
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 * 3/ Once a compute block operation has been requested handle_stripe treats
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 *    that block as if it is up to date.  raid5_run_ops guaruntees that any
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 *    operation that is dependent on the compute block result is initiated after
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 *    the compute block completes.
159
 */
160
 
161
struct stripe_head {
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        struct hlist_node       hash;
163
        struct list_head        lru;                    /* inactive_list or handle_list */
164
        struct raid5_private_data       *raid_conf;
165
        sector_t                sector;                 /* sector of this row */
166
        int                     pd_idx;                 /* parity disk index */
167
        unsigned long           state;                  /* state flags */
168
        atomic_t                count;                  /* nr of active thread/requests */
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        spinlock_t              lock;
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        int                     bm_seq; /* sequence number for bitmap flushes */
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        int                     disks;                  /* disks in stripe */
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        /* stripe_operations
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         * @pending - pending ops flags (set for request->issue->complete)
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         * @ack - submitted ops flags (set for issue->complete)
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         * @complete - completed ops flags (set for complete)
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         * @target - STRIPE_OP_COMPUTE_BLK target
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         * @count - raid5_runs_ops is set to run when this is non-zero
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         */
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        struct stripe_operations {
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                unsigned long      pending;
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                unsigned long      ack;
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                unsigned long      complete;
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                int                target;
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                int                count;
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                u32                zero_sum_result;
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        } ops;
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        struct r5dev {
188
                struct bio      req;
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                struct bio_vec  vec;
190
                struct page     *page;
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                struct bio      *toread, *read, *towrite, *written;
192
                sector_t        sector;                 /* sector of this page */
193
                unsigned long   flags;
194
        } dev[1]; /* allocated with extra space depending of RAID geometry */
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};
196
 
197
/* stripe_head_state - collects and tracks the dynamic state of a stripe_head
198
 *     for handle_stripe.  It is only valid under spin_lock(sh->lock);
199
 */
200
struct stripe_head_state {
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        int syncing, expanding, expanded;
202
        int locked, uptodate, to_read, to_write, failed, written;
203
        int to_fill, compute, req_compute, non_overwrite;
204
        int failed_num;
205
};
206
 
207
/* r6_state - extra state data only relevant to r6 */
208
struct r6_state {
209
        int p_failed, q_failed, qd_idx, failed_num[2];
210
};
211
 
212
/* Flags */
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#define R5_UPTODATE     0        /* page contains current data */
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#define R5_LOCKED       1       /* IO has been submitted on "req" */
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#define R5_OVERWRITE    2       /* towrite covers whole page */
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/* and some that are internal to handle_stripe */
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#define R5_Insync       3       /* rdev && rdev->in_sync at start */
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#define R5_Wantread     4       /* want to schedule a read */
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#define R5_Wantwrite    5
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#define R5_Overlap      7       /* There is a pending overlapping request on this block */
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#define R5_ReadError    8       /* seen a read error here recently */
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#define R5_ReWrite      9       /* have tried to over-write the readerror */
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#define R5_Expanded     10      /* This block now has post-expand data */
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#define R5_Wantcompute  11 /* compute_block in progress treat as
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                                    * uptodate
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                                    */
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#define R5_Wantfill     12 /* dev->toread contains a bio that needs
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                                    * filling
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                                    */
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#define R5_Wantprexor   13 /* distinguish blocks ready for rmw from
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                                    * other "towrites"
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                                    */
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/*
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 * Write method
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 */
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#define RECONSTRUCT_WRITE       1
238
#define READ_MODIFY_WRITE       2
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/* not a write method, but a compute_parity mode */
240
#define CHECK_PARITY            3
241
 
242
/*
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 * Stripe state
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 */
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#define STRIPE_HANDLE           2
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#define STRIPE_SYNCING          3
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#define STRIPE_INSYNC           4
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#define STRIPE_PREREAD_ACTIVE   5
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#define STRIPE_DELAYED          6
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#define STRIPE_DEGRADED         7
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#define STRIPE_BIT_DELAY        8
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#define STRIPE_EXPANDING        9
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#define STRIPE_EXPAND_SOURCE    10
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#define STRIPE_EXPAND_READY     11
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/*
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 * Operations flags (in issue order)
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 */
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#define STRIPE_OP_BIOFILL       0
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#define STRIPE_OP_COMPUTE_BLK   1
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#define STRIPE_OP_PREXOR        2
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#define STRIPE_OP_BIODRAIN      3
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#define STRIPE_OP_POSTXOR       4
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#define STRIPE_OP_CHECK 5
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#define STRIPE_OP_IO            6
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/* modifiers to the base operations
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 * STRIPE_OP_MOD_REPAIR_PD - compute the parity block and write it back
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 * STRIPE_OP_MOD_DMA_CHECK - parity is not corrupted by the check
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 */
270
#define STRIPE_OP_MOD_REPAIR_PD 7
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#define STRIPE_OP_MOD_DMA_CHECK 8
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/*
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 * Plugging:
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 *
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 * To improve write throughput, we need to delay the handling of some
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 * stripes until there has been a chance that several write requests
278
 * for the one stripe have all been collected.
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 * In particular, any write request that would require pre-reading
280
 * is put on a "delayed" queue until there are no stripes currently
281
 * in a pre-read phase.  Further, if the "delayed" queue is empty when
282
 * a stripe is put on it then we "plug" the queue and do not process it
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 * until an unplug call is made. (the unplug_io_fn() is called).
284
 *
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 * When preread is initiated on a stripe, we set PREREAD_ACTIVE and add
286
 * it to the count of prereading stripes.
287
 * When write is initiated, or the stripe refcnt == 0 (just in case) we
288
 * clear the PREREAD_ACTIVE flag and decrement the count
289
 * Whenever the 'handle' queue is empty and the device is not plugged, we
290
 * move any strips from delayed to handle and clear the DELAYED flag and set
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 * PREREAD_ACTIVE.
292
 * In stripe_handle, if we find pre-reading is necessary, we do it if
293
 * PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue.
294
 * HANDLE gets cleared if stripe_handle leave nothing locked.
295
 */
296
 
297
 
298
struct disk_info {
299
        mdk_rdev_t      *rdev;
300
};
301
 
302
struct raid5_private_data {
303
        struct hlist_head       *stripe_hashtbl;
304
        mddev_t                 *mddev;
305
        struct disk_info        *spare;
306
        int                     chunk_size, level, algorithm;
307
        int                     max_degraded;
308
        int                     raid_disks;
309
        int                     max_nr_stripes;
310
 
311
        /* used during an expand */
312
        sector_t                expand_progress;        /* MaxSector when no expand happening */
313
        sector_t                expand_lo; /* from here up to expand_progress it out-of-bounds
314
                                            * as we haven't flushed the metadata yet
315
                                            */
316
        int                     previous_raid_disks;
317
 
318
        struct list_head        handle_list; /* stripes needing handling */
319
        struct list_head        delayed_list; /* stripes that have plugged requests */
320
        struct list_head        bitmap_list; /* stripes delaying awaiting bitmap update */
321
        struct bio              *retry_read_aligned; /* currently retrying aligned bios   */
322
        struct bio              *retry_read_aligned_list; /* aligned bios retry list  */
323
        atomic_t                preread_active_stripes; /* stripes with scheduled io */
324
        atomic_t                active_aligned_reads;
325
 
326
        atomic_t                reshape_stripes; /* stripes with pending writes for reshape */
327
        /* unfortunately we need two cache names as we temporarily have
328
         * two caches.
329
         */
330
        int                     active_name;
331
        char                    cache_name[2][20];
332
        struct kmem_cache               *slab_cache; /* for allocating stripes */
333
 
334
        int                     seq_flush, seq_write;
335
        int                     quiesce;
336
 
337
        int                     fullsync;  /* set to 1 if a full sync is needed,
338
                                            * (fresh device added).
339
                                            * Cleared when a sync completes.
340
                                            */
341
 
342
        struct page             *spare_page; /* Used when checking P/Q in raid6 */
343
 
344
        /*
345
         * Free stripes pool
346
         */
347
        atomic_t                active_stripes;
348
        struct list_head        inactive_list;
349
        wait_queue_head_t       wait_for_stripe;
350
        wait_queue_head_t       wait_for_overlap;
351
        int                     inactive_blocked;       /* release of inactive stripes blocked,
352
                                                         * waiting for 25% to be free
353
                                                         */
354
        int                     pool_size; /* number of disks in stripeheads in pool */
355
        spinlock_t              device_lock;
356
        struct disk_info        *disks;
357
};
358
 
359
typedef struct raid5_private_data raid5_conf_t;
360
 
361
#define mddev_to_conf(mddev) ((raid5_conf_t *) mddev->private)
362
 
363
/*
364
 * Our supported algorithms
365
 */
366
#define ALGORITHM_LEFT_ASYMMETRIC       0
367
#define ALGORITHM_RIGHT_ASYMMETRIC      1
368
#define ALGORITHM_LEFT_SYMMETRIC        2
369
#define ALGORITHM_RIGHT_SYMMETRIC       3
370
 
371
#endif

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