1 /* 2 * bitmap.h: Copyright (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003 3 * 4 * additions: Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc. 5 */ 6 #ifndef BITMAP_H 7 #define BITMAP_H 1 8 9 #define BITMAP_MAJOR_LO 3 10 /* version 4 insists the bitmap is in little-endian order 11 * with version 3, it is host-endian which is non-portable 12 */ 13 #define BITMAP_MAJOR_HI 4 14 #define BITMAP_MAJOR_HOSTENDIAN 3 15 16 #define BITMAP_MINOR 39 17 18 /* 19 * in-memory bitmap: 20 * 21 * Use 16 bit block counters to track pending writes to each "chunk". 22 * The 2 high order bits are special-purpose, the first is a flag indicating 23 * whether a resync is needed. The second is a flag indicating whether a 24 * resync is active. 25 * This means that the counter is actually 14 bits: 26 * 27 * +--------+--------+------------------------------------------------+ 28 * | resync | resync | counter | 29 * | needed | active | | 30 * | (0-1) | (0-1) | (0-16383) | 31 * +--------+--------+------------------------------------------------+ 32 * 33 * The "resync needed" bit is set when: 34 * a '1' bit is read from storage at startup. 35 * a write request fails on some drives 36 * a resync is aborted on a chunk with 'resync active' set 37 * It is cleared (and resync-active set) when a resync starts across all drives 38 * of the chunk. 39 * 40 * 41 * The "resync active" bit is set when: 42 * a resync is started on all drives, and resync_needed is set. 43 * resync_needed will be cleared (as long as resync_active wasn't already set). 44 * It is cleared when a resync completes. 45 * 46 * The counter counts pending write requests, plus the on-disk bit. 47 * When the counter is '1' and the resync bits are clear, the on-disk 48 * bit can be cleared as well, thus setting the counter to 0. 49 * When we set a bit, or in the counter (to start a write), if the fields is 50 * 0, we first set the disk bit and set the counter to 1. 51 * 52 * If the counter is 0, the on-disk bit is clear and the stipe is clean 53 * Anything that dirties the stipe pushes the counter to 2 (at least) 54 * and sets the on-disk bit (lazily). 55 * If a periodic sweep find the counter at 2, it is decremented to 1. 56 * If the sweep find the counter at 1, the on-disk bit is cleared and the 57 * counter goes to zero. 58 * 59 * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block 60 * counters as a fallback when "page" memory cannot be allocated: 61 * 62 * Normal case (page memory allocated): 63 * 64 * page pointer (32-bit) 65 * 66 * [ ] ------+ 67 * | 68 * +-------> [ ][ ]..[ ] (4096 byte page == 2048 counters) 69 * c1 c2 c2048 70 * 71 * Hijacked case (page memory allocation failed): 72 * 73 * hijacked page pointer (32-bit) 74 * 75 * [ ][ ] (no page memory allocated) 76 * counter #1 (16-bit) counter #2 (16-bit) 77 * 78 */ 79 80 #ifdef __KERNEL__ 81 82 #define PAGE_BITS (PAGE_SIZE << 3) 83 #define PAGE_BIT_SHIFT (PAGE_SHIFT + 3) 84 85 typedef __u16 bitmap_counter_t; 86 #define COUNTER_BITS 16 87 #define COUNTER_BIT_SHIFT 4 88 #define COUNTER_BYTE_RATIO (COUNTER_BITS / 8) 89 #define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3) 90 91 #define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1))) 92 #define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2))) 93 #define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1) 94 #define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK) 95 #define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK) 96 #define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX) 97 98 /* how many counters per page? */ 99 #define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS) 100 /* same, except a shift value for more efficient bitops */ 101 #define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT) 102 /* same, except a mask value for more efficient bitops */ 103 #define PAGE_COUNTER_MASK (PAGE_COUNTER_RATIO - 1) 104 105 #define BITMAP_BLOCK_SIZE 512 106 #define BITMAP_BLOCK_SHIFT 9 107 108 /* how many blocks per chunk? (this is variable) */ 109 #define CHUNK_BLOCK_RATIO(bitmap) ((bitmap)->mddev->bitmap_info.chunksize >> BITMAP_BLOCK_SHIFT) 110 #define CHUNK_BLOCK_SHIFT(bitmap) ((bitmap)->chunkshift - BITMAP_BLOCK_SHIFT) 111 #define CHUNK_BLOCK_MASK(bitmap) (CHUNK_BLOCK_RATIO(bitmap) - 1) 112 113 /* when hijacked, the counters and bits represent even larger "chunks" */ 114 /* there will be 1024 chunks represented by each counter in the page pointers */ 115 #define PAGEPTR_BLOCK_RATIO(bitmap) \ 116 (CHUNK_BLOCK_RATIO(bitmap) << PAGE_COUNTER_SHIFT >> 1) 117 #define PAGEPTR_BLOCK_SHIFT(bitmap) \ 118 (CHUNK_BLOCK_SHIFT(bitmap) + PAGE_COUNTER_SHIFT - 1) 119 #define PAGEPTR_BLOCK_MASK(bitmap) (PAGEPTR_BLOCK_RATIO(bitmap) - 1) 120 121 #endif 122 123 /* 124 * bitmap structures: 125 */ 126 127 #define BITMAP_MAGIC 0x6d746962 128 129 /* use these for bitmap->flags and bitmap->sb->state bit-fields */ 130 enum bitmap_state { 131 BITMAP_STALE = 0x002, /* the bitmap file is out of date or had -EIO */ 132 BITMAP_WRITE_ERROR = 0x004, /* A write error has occurred */ 133 BITMAP_HOSTENDIAN = 0x8000, 134 }; 135 136 /* the superblock at the front of the bitmap file -- little endian */ 137 typedef struct bitmap_super_s { 138 __le32 magic; /* 0 BITMAP_MAGIC */ 139 __le32 version; /* 4 the bitmap major for now, could change... */ 140 __u8 uuid[16]; /* 8 128 bit uuid - must match md device uuid */ 141 __le64 events; /* 24 event counter for the bitmap (1)*/ 142 __le64 events_cleared;/*32 event counter when last bit cleared (2) */ 143 __le64 sync_size; /* 40 the size of the md device's sync range(3) */ 144 __le32 state; /* 48 bitmap state information */ 145 __le32 chunksize; /* 52 the bitmap chunk size in bytes */ 146 __le32 daemon_sleep; /* 56 seconds between disk flushes */ 147 __le32 write_behind; /* 60 number of outstanding write-behind writes */ 148 149 __u8 pad[256 - 64]; /* set to zero */ 150 } bitmap_super_t; 151 152 /* notes: 153 * (1) This event counter is updated before the eventcounter in the md superblock 154 * When a bitmap is loaded, it is only accepted if this event counter is equal 155 * to, or one greater than, the event counter in the superblock. 156 * (2) This event counter is updated when the other one is *if*and*only*if* the 157 * array is not degraded. As bits are not cleared when the array is degraded, 158 * this represents the last time that any bits were cleared. 159 * If a device is being added that has an event count with this value or 160 * higher, it is accepted as conforming to the bitmap. 161 * (3)This is the number of sectors represented by the bitmap, and is the range that 162 * resync happens across. For raid1 and raid5/6 it is the size of individual 163 * devices. For raid10 it is the size of the array. 164 */ 165 166 #ifdef __KERNEL__ 167 168 /* the in-memory bitmap is represented by bitmap_pages */ 169 struct bitmap_page { 170 /* 171 * map points to the actual memory page 172 */ 173 char *map; 174 /* 175 * in emergencies (when map cannot be alloced), hijack the map 176 * pointer and use it as two counters itself 177 */ 178 unsigned int hijacked:1; 179 /* 180 * count of dirty bits on the page 181 */ 182 unsigned int count:31; 183 }; 184 185 /* keep track of bitmap file pages that have pending writes on them */ 186 struct page_list { 187 struct list_head list; 188 struct page *page; 189 }; 190 191 /* the main bitmap structure - one per mddev */ 192 struct bitmap { 193 struct bitmap_page *bp; 194 unsigned long pages; /* total number of pages in the bitmap */ 195 unsigned long missing_pages; /* number of pages not yet allocated */ 196 197 mddev_t *mddev; /* the md device that the bitmap is for */ 198 199 int counter_bits; /* how many bits per block counter */ 200 201 /* bitmap chunksize -- how much data does each bit represent? */ 202 unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */ 203 unsigned long chunks; /* total number of data chunks for the array */ 204 205 /* We hold a count on the chunk currently being synced, and drop 206 * it when the last block is started. If the resync is aborted 207 * midway, we need to be able to drop that count, so we remember 208 * the counted chunk.. 209 */ 210 unsigned long syncchunk; 211 212 __u64 events_cleared; 213 int need_sync; 214 215 /* bitmap spinlock */ 216 spinlock_t lock; 217 218 struct file *file; /* backing disk file */ 219 struct page *sb_page; /* cached copy of the bitmap file superblock */ 220 struct page **filemap; /* list of cache pages for the file */ 221 unsigned long *filemap_attr; /* attributes associated w/ filemap pages */ 222 unsigned long file_pages; /* number of pages in the file */ 223 int last_page_size; /* bytes in the last page */ 224 225 unsigned long logattrs; /* used when filemap_attr doesn't exist 226 * because we are working with a dirty_log 227 */ 228 229 unsigned long flags; 230 231 int allclean; 232 233 atomic_t behind_writes; 234 unsigned long behind_writes_used; /* highest actual value at runtime */ 235 236 /* 237 * the bitmap daemon - periodically wakes up and sweeps the bitmap 238 * file, cleaning up bits and flushing out pages to disk as necessary 239 */ 240 unsigned long daemon_lastrun; /* jiffies of last run */ 241 unsigned long last_end_sync; /* when we lasted called end_sync to 242 * update bitmap with resync progress */ 243 244 atomic_t pending_writes; /* pending writes to the bitmap file */ 245 wait_queue_head_t write_wait; 246 wait_queue_head_t overflow_wait; 247 wait_queue_head_t behind_wait; 248 249 struct sysfs_dirent *sysfs_can_clear; 250 251 }; 252 253 /* the bitmap API */ 254 255 /* these are used only by md/bitmap */ 256 int bitmap_create(mddev_t *mddev); 257 int bitmap_load(mddev_t *mddev); 258 void bitmap_flush(mddev_t *mddev); 259 void bitmap_destroy(mddev_t *mddev); 260 261 void bitmap_print_sb(struct bitmap *bitmap); 262 void bitmap_update_sb(struct bitmap *bitmap); 263 264 int bitmap_setallbits(struct bitmap *bitmap); 265 void bitmap_write_all(struct bitmap *bitmap); 266 267 void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e); 268 269 /* these are exported */ 270 int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, 271 unsigned long sectors, int behind); 272 void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, 273 unsigned long sectors, int success, int behind); 274 int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int degraded); 275 void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted); 276 void bitmap_close_sync(struct bitmap *bitmap); 277 void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector); 278 279 void bitmap_unplug(struct bitmap *bitmap); 280 void bitmap_daemon_work(mddev_t *mddev); 281 #endif 282 283 #endif 284