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#ifndef _RAID5_H #define _RAID5_H #include <linux/raid/md.h> #include <linux/raid/xor.h> /* * * 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 needed unlockstripe schedule io * 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. */ struct stripe_head { struct hlist_node hash; struct list_head lru; /* inactive_list or handle_list */ struct raid5_private_data *raid_conf; sector_t sector; /* sector of this row */ int pd_idx; /* parity disk index */ unsigned long state; /* state flags */ atomic_t count; /* nr of active thread/requests */ spinlock_t lock; int bm_seq; /* sequence number for bitmap flushes */ struct r5dev { struct bio req; struct bio_vec vec; struct page *page; struct bio *toread, *towrite, *written; sector_t sector; /* sector of this page */ unsigned long flags; } dev[1]; /* allocated with extra space depending of RAID geometry */ }; /* 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 */ /* * Write method */ #define RECONSTRUCT_WRITE 1 #define READ_MODIFY_WRITE 2 /* not a write method, but a compute_parity mode */ #define CHECK_PARITY 3 /* * 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 /* * 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 delayed 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_size, level, algorithm; int raid_disks, working_disks, failed_disks; int max_nr_stripes; struct list_head handle_list; /* stripes needing handling */ struct list_head delayed_list; /* stripes that have plugged requests */ struct list_head bitmap_list; /* stripes delaying awaiting bitmap update */ atomic_t preread_active_stripes; /* stripes with scheduled io */ char cache_name[20]; kmem_cache_t *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. */ struct page *spare_page; /* Used when checking P/Q in raid6 */ /* * 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 */ spinlock_t device_lock; struct disk_info disks[0]; }; typedef struct raid5_private_data raid5_conf_t; #define mddev_to_conf(mddev) ((raid5_conf_t *) mddev->private) /* * Our supported algorithms */ #define ALGORITHM_LEFT_ASYMMETRIC 0 #define ALGORITHM_RIGHT_ASYMMETRIC 1 #define ALGORITHM_LEFT_SYMMETRIC 2 #define ALGORITHM_RIGHT_SYMMETRIC 3 #endif