1 #ifndef _RAID5_H 2 #define _RAID5_H 3 4 #include <linux/raid/md.h> 5 #include <linux/raid/xor.h> 6 7 /* 8 * 9 * Each stripe contains one buffer per disc. Each buffer can be in 10 * one of a number of states determined by bh_state. Changes between 11 * these states happen *almost* exclusively under a per-stripe 12 * spinlock. Some very specific changes can happen in b_end_io, and 13 * these are not protected by the spin lock. 14 * 15 * The bh_state bits that are used to represent these states are: 16 * BH_Uptodate, BH_Lock 17 * 18 * State Empty == !Uptodate, !Lock 19 * We have no data, and there is no active request 20 * State Want == !Uptodate, Lock 21 * A read request is being submitted for this block 22 * State Dirty == Uptodate, Lock 23 * Some new data is in this buffer, and it is being written out 24 * State Clean == Uptodate, !Lock 25 * We have valid data which is the same as on disc 26 * 27 * The possible state transitions are: 28 * 29 * Empty -> Want - on read or write to get old data for parity calc 30 * Empty -> Dirty - on compute_parity to satisfy write/sync request.(RECONSTRUCT_WRITE) 31 * Empty -> Clean - on compute_block when computing a block for failed drive 32 * Want -> Empty - on failed read 33 * Want -> Clean - on successful completion of read request 34 * Dirty -> Clean - on successful completion of write request 35 * Dirty -> Clean - on failed write 36 * Clean -> Dirty - on compute_parity to satisfy write/sync (RECONSTRUCT or RMW) 37 * 38 * The Want->Empty, Want->Clean, Dirty->Clean, transitions 39 * all happen in b_end_io at interrupt time. 40 * Each sets the Uptodate bit before releasing the Lock bit. 41 * This leaves one multi-stage transition: 42 * Want->Dirty->Clean 43 * This is safe because thinking that a Clean buffer is actually dirty 44 * will at worst delay some action, and the stripe will be scheduled 45 * for attention after the transition is complete. 46 * 47 * There is one possibility that is not covered by these states. That 48 * is if one drive has failed and there is a spare being rebuilt. We 49 * can't distinguish between a clean block that has been generated 50 * from parity calculations, and a clean block that has been 51 * successfully written to the spare ( or to parity when resyncing). 52 * To distingush these states we have a stripe bit STRIPE_INSYNC that 53 * is set whenever a write is scheduled to the spare, or to the parity 54 * disc if there is no spare. A sync request clears this bit, and 55 * when we find it set with no buffers locked, we know the sync is 56 * complete. 57 * 58 * Buffers for the md device that arrive via make_request are attached 59 * to the appropriate stripe in one of two lists linked on b_reqnext. 60 * One list (bh_read) for read requests, one (bh_write) for write. 61 * There should never be more than one buffer on the two lists 62 * together, but we are not guaranteed of that so we allow for more. 63 * 64 * If a buffer is on the read list when the associated cache buffer is 65 * Uptodate, the data is copied into the read buffer and it's b_end_io 66 * routine is called. This may happen in the end_request routine only 67 * if the buffer has just successfully been read. end_request should 68 * remove the buffers from the list and then set the Uptodate bit on 69 * the buffer. Other threads may do this only if they first check 70 * that the Uptodate bit is set. Once they have checked that they may 71 * take buffers off the read queue. 72 * 73 * When a buffer on the write list is committed for write is it copied 74 * into the cache buffer, which is then marked dirty, and moved onto a 75 * third list, the written list (bh_written). Once both the parity 76 * block and the cached buffer are successfully written, any buffer on 77 * a written list can be returned with b_end_io. 78 * 79 * The write list and read list both act as fifos. The read list is 80 * protected by the device_lock. The write and written lists are 81 * protected by the stripe lock. The device_lock, which can be 82 * claimed while the stipe lock is held, is only for list 83 * manipulations and will only be held for a very short time. It can 84 * be claimed from interrupts. 85 * 86 * 87 * Stripes in the stripe cache can be on one of two lists (or on 88 * neither). The "inactive_list" contains stripes which are not 89 * currently being used for any request. They can freely be reused 90 * for another stripe. The "handle_list" contains stripes that need 91 * to be handled in some way. Both of these are fifo queues. Each 92 * stripe is also (potentially) linked to a hash bucket in the hash 93 * table so that it can be found by sector number. Stripes that are 94 * not hashed must be on the inactive_list, and will normally be at 95 * the front. All stripes start life this way. 96 * 97 * The inactive_list, handle_list and hash bucket lists are all protected by the 98 * device_lock. 99 * - stripes on the inactive_list never have their stripe_lock held. 100 * - stripes have a reference counter. If count==0, they are on a list. 101 * - If a stripe might need handling, STRIPE_HANDLE is set. 102 * - When refcount reaches zero, then if STRIPE_HANDLE it is put on 103 * handle_list else inactive_list 104 * 105 * This, combined with the fact that STRIPE_HANDLE is only ever 106 * cleared while a stripe has a non-zero count means that if the 107 * refcount is 0 and STRIPE_HANDLE is set, then it is on the 108 * handle_list and if recount is 0 and STRIPE_HANDLE is not set, then 109 * the stripe is on inactive_list. 110 * 111 * The possible transitions are: 112 * activate an unhashed/inactive stripe (get_active_stripe()) 113 * lockdev check-hash unlink-stripe cnt++ clean-stripe hash-stripe unlockdev 114 * activate a hashed, possibly active stripe (get_active_stripe()) 115 * lockdev check-hash if(!cnt++)unlink-stripe unlockdev 116 * attach a request to an active stripe (add_stripe_bh()) 117 * lockdev attach-buffer unlockdev 118 * handle a stripe (handle_stripe()) 119 * lockstripe clrSTRIPE_HANDLE ... (lockdev check-buffers unlockdev) .. change-state .. record io needed unlockstripe schedule io 120 * release an active stripe (release_stripe()) 121 * lockdev if (!--cnt) { if STRIPE_HANDLE, add to handle_list else add to inactive-list } unlockdev 122 * 123 * The refcount counts each thread that have activated the stripe, 124 * plus raid5d if it is handling it, plus one for each active request 125 * on a cached buffer. 126 */ 127 struct stripe_head { 128 struct stripe_head *hash_next, **hash_pprev; /* hash pointers */ 129 struct list_head lru; /* inactive_list or handle_list */ 130 struct raid5_private_data *raid_conf; 131 struct buffer_head *bh_cache[MD_SB_DISKS]; /* buffered copy */ 132 struct buffer_head *bh_read[MD_SB_DISKS]; /* read request buffers of the MD device */ 133 struct buffer_head *bh_write[MD_SB_DISKS]; /* write request buffers of the MD device */ 134 struct buffer_head *bh_written[MD_SB_DISKS]; /* write request buffers of the MD device that have been scheduled for write */ 135 struct page *bh_page[MD_SB_DISKS]; /* saved bh_cache[n]->b_page when reading around the cache */ 136 unsigned long sector; /* sector of this row */ 137 int size; /* buffers size */ 138 int pd_idx; /* parity disk index */ 139 unsigned long state; /* state flags */ 140 atomic_t count; /* nr of active thread/requests */ 141 spinlock_t lock; 142 int sync_redone; 143 }; 144 145 146 /* 147 * Write method 148 */ 149 #define RECONSTRUCT_WRITE 1 150 #define READ_MODIFY_WRITE 2 151 /* not a write method, but a compute_parity mode */ 152 #define CHECK_PARITY 3 153 154 /* 155 * Stripe state 156 */ 157 #define STRIPE_ERROR 1 158 #define STRIPE_HANDLE 2 159 #define STRIPE_SYNCING 3 160 #define STRIPE_INSYNC 4 161 #define STRIPE_PREREAD_ACTIVE 5 162 #define STRIPE_DELAYED 6 163 164 /* 165 * Plugging: 166 * 167 * To improve write throughput, we need to delay the handling of some 168 * stripes until there has been a chance that several write requests 169 * for the one stripe have all been collected. 170 * In particular, any write request that would require pre-reading 171 * is put on a "delayed" queue until there are no stripes currently 172 * in a pre-read phase. Further, if the "delayed" queue is empty when 173 * a stripe is put on it then we "plug" the queue and do not process it 174 * until an unplg call is made. (the tq_disk list is run). 175 * 176 * When preread is initiated on a stripe, we set PREREAD_ACTIVE and add 177 * it to the count of prereading stripes. 178 * When write is initiated, or the stripe refcnt == 0 (just in case) we 179 * clear the PREREAD_ACTIVE flag and decrement the count 180 * Whenever the delayed queue is empty and the device is not plugged, we 181 * move any strips from delayed to handle and clear the DELAYED flag and set PREREAD_ACTIVE. 182 * In stripe_handle, if we find pre-reading is necessary, we do it if 183 * PREREAD_ACTIVE is set, else we set DELAYED which will send it to the delayed queue. 184 * HANDLE gets cleared if stripe_handle leave nothing locked. 185 */ 186 187 188 struct disk_info { 189 kdev_t dev; 190 int operational; 191 int number; 192 int raid_disk; 193 int write_only; 194 int spare; 195 int used_slot; 196 }; 197 198 struct raid5_private_data { 199 struct stripe_head **stripe_hashtbl; 200 mddev_t *mddev; 201 mdk_thread_t *thread, *resync_thread; 202 struct disk_info disks[MD_SB_DISKS]; 203 struct disk_info *spare; 204 int buffer_size; 205 int chunk_size, level, algorithm; 206 int raid_disks, working_disks, failed_disks; 207 int resync_parity; 208 int max_nr_stripes; 209 210 struct list_head handle_list; /* stripes needing handling */ 211 struct list_head delayed_list; /* stripes that have plugged requests */ 212 atomic_t preread_active_stripes; /* stripes with scheduled io */ 213 /* 214 * Free stripes pool 215 */ 216 atomic_t active_stripes; 217 struct list_head inactive_list; 218 md_wait_queue_head_t wait_for_stripe; 219 int inactive_blocked; /* release of inactive stripes blocked, 220 * waiting for 25% to be free 221 */ 222 md_spinlock_t device_lock; 223 224 int plugged; 225 struct tq_struct plug_tq; 226 }; 227 228 typedef struct raid5_private_data raid5_conf_t; 229 230 #define mddev_to_conf(mddev) ((raid5_conf_t *) mddev->private) 231 232 /* 233 * Our supported algorithms 234 */ 235 #define ALGORITHM_LEFT_ASYMMETRIC 0 236 #define ALGORITHM_RIGHT_ASYMMETRIC 1 237 #define ALGORITHM_LEFT_SYMMETRIC 2 238 #define ALGORITHM_RIGHT_SYMMETRIC 3 239 240 #endif 241