#ifndef _RAID5_H #define _RAID5_H #include #include /* * * Each stripe contains one buffer per disc. Each buffer can be in * one of a number of states stored in "flags". Changes between * these states happen *almost* exclusively under a per-stripe * spinlock. Some very specific changes can happen in bi_end_io, and * these are not protected by the spin lock. * * 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.(RECONSTRUCT_WRITE) * 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 distingush 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 is * protected by the device_lock. The write and written lists are * protected by the stripe lock. The device_lock, which can be * claimed while the stipe lock is held, 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 on the inactive_list never have their stripe_lock held. * - 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()) * lockstripe clrSTRIPE_HANDLE ... * (lockdev check-buffers unlockdev) .. * change-state .. * record io/ops needed unlockstripe 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. * * Stripe operations are performed outside the stripe lock, * 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 sh->lock * 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, }; struct stripe_head { struct hlist_node hash; struct list_head lru; /* inactive_list or handle_list */ struct raid5_private_data *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 */ unsigned long state; /* state flags */ atomic_t count; /* nr of active thread/requests */ spinlock_t lock; int bm_seq; /* sequence number for bitmap flushes */ int disks; /* disks in stripe */ enum check_states check_state; enum reconstruct_states reconstruct_state; /** * 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; #ifdef CONFIG_MULTICORE_RAID456 unsigned long request; wait_queue_head_t wait_for_ops; #endif } ops; struct r5dev { struct bio req; struct bio_vec vec; struct page *page; struct bio *toread, *read, *towrite, *written; sector_t sector; /* sector of this page */ unsigned long flags; } 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. It is only valid under spin_lock(sh->lock); */ struct stripe_head_state { int syncing, expanding, expanded; int locked, uptodate, to_read, to_write, failed, written; int to_fill, compute, req_compute, non_overwrite; int failed_num; unsigned long ops_request; }; /* r6_state - extra state data only relevant to r6 */ struct r6_state { int p_failed, q_failed, failed_num[2]; }; /* Flags */ #define R5_UPTODATE 0 /* page contains current data */ #define R5_LOCKED 1 /* IO has been submitted on "req" */ #define R5_OVERWRITE 2 /* towrite covers whole page */ /* and some that are internal to handle_stripe */ #define R5_Insync 3 /* rdev && rdev->in_sync at start */ #define R5_Wantread 4 /* want to schedule a read */ #define R5_Wantwrite 5 #define R5_Overlap 7 /* There is a pending overlapping request on this block */ #define R5_ReadError 8 /* seen a read error here recently */ #define R5_ReWrite 9 /* have tried to over-write the readerror */ #define R5_Expanded 10 /* This block now has post-expand data */ #define R5_Wantcompute 11 /* compute_block in progress treat as * uptodate */ #define R5_Wantfill 12 /* dev->toread contains a bio that needs * filling */ #define R5_Wantdrain 13 /* dev->towrite needs to be drained */ /* * Write method */ #define RECONSTRUCT_WRITE 1 #define READ_MODIFY_WRITE 2 /* not a write method, but a compute_parity mode */ #define CHECK_PARITY 3 /* Additional compute_parity mode -- updates the parity w/o LOCKING */ #define UPDATE_PARITY 4 /* * Stripe state */ #define STRIPE_HANDLE 2 #define STRIPE_SYNCING 3 #define STRIPE_INSYNC 4 #define STRIPE_PREREAD_ACTIVE 5 #define STRIPE_DELAYED 6 #define STRIPE_DEGRADED 7 #define STRIPE_BIT_DELAY 8 #define STRIPE_EXPANDING 9 #define STRIPE_EXPAND_SOURCE 10 #define STRIPE_EXPAND_READY 11 #define STRIPE_IO_STARTED 12 /* do not count towards 'bypass_count' */ #define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */ #define STRIPE_BIOFILL_RUN 14 #define STRIPE_COMPUTE_RUN 15 #define STRIPE_OPS_REQ_PENDING 16 /* * Operation request flags */ #define STRIPE_OP_BIOFILL 0 #define STRIPE_OP_COMPUTE_BLK 1 #define STRIPE_OP_PREXOR 2 #define STRIPE_OP_BIODRAIN 3 #define STRIPE_OP_RECONSTRUCT 4 #define STRIPE_OP_CHECK 5 /* * 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 leave nothing locked. */ struct disk_info { mdk_rdev_t *rdev; }; struct raid5_private_data { struct hlist_head *stripe_hashtbl; mddev_t *mddev; struct disk_info *spare; int chunk_sectors; int level, algorithm; int max_degraded; int raid_disks; int max_nr_stripes; /* 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 */ unsigned long reshape_checkpoint; /* Time we last updated * metadata */ struct list_head handle_list; /* stripes needing handling */ 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 */ 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 */ 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 */ 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. */ /* per cpu variables */ 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 */ } __percpu *percpu; size_t scribble_len; /* size of scribble region must be * associated with conf to handle * cpu hotplug while reshaping */ #ifdef CONFIG_HOTPLUG_CPU struct notifier_block cpu_notify; #endif /* * Free stripes pool */ atomic_t active_stripes; struct list_head inactive_list; wait_queue_head_t wait_for_stripe; wait_queue_head_t wait_for_overlap; int inactive_blocked; /* release of inactive stripes blocked, * waiting for 25% to be free */ int pool_size; /* number of disks in stripeheads in pool */ spinlock_t device_lock; struct disk_info *disks; /* When taking over an array from a different personality, we store * the new thread here until we fully activate the array. */ struct mdk_thread_s *thread; }; typedef struct raid5_private_data raid5_conf_t; /* * 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; } extern int md_raid5_congested(mddev_t *mddev, int bits); extern int raid5_set_cache_size(mddev_t *mddev, int size); #endif