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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 3 | |
10 | #define BITMAP_MINOR 38 | |
11 | ||
12 | /* | |
13 | * in-memory bitmap: | |
14 | * | |
15 | * Use 16 bit block counters to track pending writes to each "chunk". | |
16 | * The 2 high order bits are special-purpose, the first is a flag indicating | |
17 | * whether a resync is needed. The second is a flag indicating whether a | |
18 | * resync is active. | |
19 | * This means that the counter is actually 14 bits: | |
20 | * | |
21 | * +--------+--------+------------------------------------------------+ | |
22 | * | resync | resync | counter | | |
23 | * | needed | active | | | |
24 | * | (0-1) | (0-1) | (0-16383) | | |
25 | * +--------+--------+------------------------------------------------+ | |
26 | * | |
27 | * The "resync needed" bit is set when: | |
28 | * a '1' bit is read from storage at startup. | |
29 | * a write request fails on some drives | |
30 | * a resync is aborted on a chunk with 'resync active' set | |
31 | * It is cleared (and resync-active set) when a resync starts across all drives | |
32 | * of the chunk. | |
33 | * | |
34 | * | |
35 | * The "resync active" bit is set when: | |
36 | * a resync is started on all drives, and resync_needed is set. | |
37 | * resync_needed will be cleared (as long as resync_active wasn't already set). | |
38 | * It is cleared when a resync completes. | |
39 | * | |
40 | * The counter counts pending write requests, plus the on-disk bit. | |
41 | * When the counter is '1' and the resync bits are clear, the on-disk | |
42 | * bit can be cleared aswell, thus setting the counter to 0. | |
43 | * When we set a bit, or in the counter (to start a write), if the fields is | |
44 | * 0, we first set the disk bit and set the counter to 1. | |
45 | * | |
46 | * Also, we'll hijack the "map" pointer itself and use it as two 16 bit block | |
47 | * counters as a fallback when "page" memory cannot be allocated: | |
48 | * | |
49 | * Normal case (page memory allocated): | |
50 | * | |
51 | * page pointer (32-bit) | |
52 | * | |
53 | * [ ] ------+ | |
54 | * | | |
55 | * +-------> [ ][ ]..[ ] (4096 byte page == 2048 counters) | |
56 | * c1 c2 c2048 | |
57 | * | |
58 | * Hijacked case (page memory allocation failed): | |
59 | * | |
60 | * hijacked page pointer (32-bit) | |
61 | * | |
62 | * [ ][ ] (no page memory allocated) | |
63 | * counter #1 (16-bit) counter #2 (16-bit) | |
64 | * | |
65 | */ | |
66 | ||
67 | #ifdef __KERNEL__ | |
68 | ||
69 | #define PAGE_BITS (PAGE_SIZE << 3) | |
70 | #define PAGE_BIT_SHIFT (PAGE_SHIFT + 3) | |
71 | ||
72 | typedef __u16 bitmap_counter_t; | |
73 | #define COUNTER_BITS 16 | |
74 | #define COUNTER_BIT_SHIFT 4 | |
75 | #define COUNTER_BYTE_RATIO (COUNTER_BITS / 8) | |
76 | #define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3) | |
77 | ||
78 | #define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1))) | |
79 | #define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2))) | |
80 | #define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1) | |
81 | #define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK) | |
82 | #define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK) | |
83 | #define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX) | |
84 | ||
85 | /* how many counters per page? */ | |
86 | #define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS) | |
87 | /* same, except a shift value for more efficient bitops */ | |
88 | #define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT) | |
89 | /* same, except a mask value for more efficient bitops */ | |
90 | #define PAGE_COUNTER_MASK (PAGE_COUNTER_RATIO - 1) | |
91 | ||
92 | #define BITMAP_BLOCK_SIZE 512 | |
93 | #define BITMAP_BLOCK_SHIFT 9 | |
94 | ||
95 | /* how many blocks per chunk? (this is variable) */ | |
96 | #define CHUNK_BLOCK_RATIO(bitmap) ((bitmap)->chunksize >> BITMAP_BLOCK_SHIFT) | |
97 | #define CHUNK_BLOCK_SHIFT(bitmap) ((bitmap)->chunkshift - BITMAP_BLOCK_SHIFT) | |
98 | #define CHUNK_BLOCK_MASK(bitmap) (CHUNK_BLOCK_RATIO(bitmap) - 1) | |
99 | ||
100 | /* when hijacked, the counters and bits represent even larger "chunks" */ | |
101 | /* there will be 1024 chunks represented by each counter in the page pointers */ | |
102 | #define PAGEPTR_BLOCK_RATIO(bitmap) \ | |
103 | (CHUNK_BLOCK_RATIO(bitmap) << PAGE_COUNTER_SHIFT >> 1) | |
104 | #define PAGEPTR_BLOCK_SHIFT(bitmap) \ | |
105 | (CHUNK_BLOCK_SHIFT(bitmap) + PAGE_COUNTER_SHIFT - 1) | |
106 | #define PAGEPTR_BLOCK_MASK(bitmap) (PAGEPTR_BLOCK_RATIO(bitmap) - 1) | |
107 | ||
108 | /* | |
109 | * on-disk bitmap: | |
110 | * | |
111 | * Use one bit per "chunk" (block set). We do the disk I/O on the bitmap | |
112 | * file a page at a time. There's a superblock at the start of the file. | |
113 | */ | |
114 | ||
115 | /* map chunks (bits) to file pages - offset by the size of the superblock */ | |
116 | #define CHUNK_BIT_OFFSET(chunk) ((chunk) + (sizeof(bitmap_super_t) << 3)) | |
117 | ||
118 | #endif | |
119 | ||
120 | /* | |
121 | * bitmap structures: | |
122 | */ | |
123 | ||
124 | #define BITMAP_MAGIC 0x6d746962 | |
125 | ||
126 | /* use these for bitmap->flags and bitmap->sb->state bit-fields */ | |
127 | enum bitmap_state { | |
128 | BITMAP_ACTIVE = 0x001, /* the bitmap is in use */ | |
129 | BITMAP_STALE = 0x002 /* the bitmap file is out of date or had -EIO */ | |
130 | }; | |
131 | ||
132 | /* the superblock at the front of the bitmap file -- little endian */ | |
133 | typedef struct bitmap_super_s { | |
134 | __u32 magic; /* 0 BITMAP_MAGIC */ | |
135 | __u32 version; /* 4 the bitmap major for now, could change... */ | |
136 | __u8 uuid[16]; /* 8 128 bit uuid - must match md device uuid */ | |
137 | __u64 events; /* 24 event counter for the bitmap (1)*/ | |
138 | __u64 events_cleared;/*32 event counter when last bit cleared (2) */ | |
139 | __u64 sync_size; /* 40 the size of the md device's sync range(3) */ | |
140 | __u32 state; /* 48 bitmap state information */ | |
141 | __u32 chunksize; /* 52 the bitmap chunk size in bytes */ | |
142 | __u32 daemon_sleep; /* 56 seconds between disk flushes */ | |
143 | ||
e793c2e5 | 144 | __u8 pad[256 - 60]; /* set to zero */ |
c82f047c NB |
145 | } bitmap_super_t; |
146 | ||
147 | /* notes: | |
148 | * (1) This event counter is updated before the eventcounter in the md superblock | |
149 | * When a bitmap is loaded, it is only accepted if this event counter is equal | |
150 | * to, or one greater than, the event counter in the superblock. | |
151 | * (2) This event counter is updated when the other one is *if*and*only*if* the | |
152 | * array is not degraded. As bits are not cleared when the array is degraded, | |
153 | * this represents the last time that any bits were cleared. | |
154 | * If a device is being added that has an event count with this value or | |
155 | * higher, it is accepted as conforming to the bitmap. | |
156 | * (3)This is the number of sectors represented by the bitmap, and is the range that | |
157 | * resync happens across. For raid1 and raid5/6 it is the size of individual | |
158 | * devices. For raid10 it is the size of the array. | |
159 | */ | |
160 | ||
161 | #ifdef __KERNEL__ | |
162 | ||
163 | /* the in-memory bitmap is represented by bitmap_pages */ | |
164 | struct bitmap_page { | |
165 | /* | |
166 | * map points to the actual memory page | |
167 | */ | |
168 | char *map; | |
169 | /* | |
170 | * in emergencies (when map cannot be alloced), hijack the map | |
171 | * pointer and use it as two counters itself | |
172 | */ | |
173 | unsigned int hijacked; | |
174 | /* | |
175 | * count of dirty bits on the page | |
176 | */ | |
177 | int count; | |
178 | }; | |
179 | ||
180 | /* keep track of bitmap file pages that have pending writes on them */ | |
181 | struct page_list { | |
182 | struct list_head list; | |
183 | struct page *page; | |
184 | }; | |
185 | ||
186 | /* the main bitmap structure - one per mddev */ | |
187 | struct bitmap { | |
188 | struct bitmap_page *bp; | |
189 | unsigned long pages; /* total number of pages in the bitmap */ | |
190 | unsigned long missing_pages; /* number of pages not yet allocated */ | |
191 | ||
192 | mddev_t *mddev; /* the md device that the bitmap is for */ | |
193 | ||
194 | int counter_bits; /* how many bits per block counter */ | |
195 | ||
196 | /* bitmap chunksize -- how much data does each bit represent? */ | |
197 | unsigned long chunksize; | |
198 | unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */ | |
199 | unsigned long chunks; /* total number of data chunks for the array */ | |
200 | ||
201 | /* We hold a count on the chunk currently being synced, and drop | |
202 | * it when the last block is started. If the resync is aborted | |
203 | * midway, we need to be able to drop that count, so we remember | |
204 | * the counted chunk.. | |
205 | */ | |
206 | unsigned long syncchunk; | |
207 | ||
208 | __u64 events_cleared; | |
209 | ||
210 | /* bitmap spinlock */ | |
211 | spinlock_t lock; | |
212 | ||
213 | struct file *file; /* backing disk file */ | |
214 | struct page *sb_page; /* cached copy of the bitmap file superblock */ | |
215 | struct page **filemap; /* list of cache pages for the file */ | |
216 | unsigned long *filemap_attr; /* attributes associated w/ filemap pages */ | |
217 | unsigned long file_pages; /* number of pages in the file */ | |
218 | ||
219 | unsigned long flags; | |
220 | ||
221 | /* | |
222 | * the bitmap daemon - periodically wakes up and sweeps the bitmap | |
223 | * file, cleaning up bits and flushing out pages to disk as necessary | |
224 | */ | |
225 | mdk_thread_t *daemon; | |
226 | unsigned long daemon_sleep; /* how many seconds between updates? */ | |
227 | ||
228 | /* | |
229 | * bitmap write daemon - this daemon performs writes to the bitmap file | |
230 | * this thread is only needed because of a limitation in ext3 (jbd) | |
231 | * that does not allow a task to have two journal transactions ongoing | |
232 | * simultaneously (even if the transactions are for two different | |
233 | * filesystems) -- in the case of bitmap, that would be the filesystem | |
234 | * that the bitmap file resides on and the filesystem that is mounted | |
235 | * on the md device -- see current->journal_info in jbd/transaction.c | |
236 | */ | |
237 | mdk_thread_t *write_daemon; | |
238 | mdk_thread_t *writeback_daemon; | |
239 | spinlock_t write_lock; | |
240 | struct semaphore write_ready; | |
241 | struct semaphore write_done; | |
242 | unsigned long writes_pending; | |
243 | wait_queue_head_t write_wait; | |
244 | struct list_head write_pages; | |
245 | struct list_head complete_pages; | |
246 | mempool_t *write_pool; | |
247 | }; | |
248 | ||
249 | /* the bitmap API */ | |
250 | ||
251 | /* these are used only by md/bitmap */ | |
252 | int bitmap_create(mddev_t *mddev); | |
253 | void bitmap_destroy(mddev_t *mddev); | |
254 | int bitmap_active(struct bitmap *bitmap); | |
255 | ||
256 | char *file_path(struct file *file, char *buf, int count); | |
257 | void bitmap_print_sb(struct bitmap *bitmap); | |
258 | int bitmap_update_sb(struct bitmap *bitmap); | |
259 | ||
260 | int bitmap_setallbits(struct bitmap *bitmap); | |
261 | ||
262 | /* these are exported */ | |
263 | void bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors); | |
264 | void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, | |
265 | int success); | |
266 | int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks); | |
267 | void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted); | |
268 | void bitmap_close_sync(struct bitmap *bitmap); | |
269 | ||
270 | int bitmap_unplug(struct bitmap *bitmap); | |
271 | #endif | |
272 | ||
273 | #endif |