Line data Source code
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 aswell, 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 1 :
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 1 :
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 flags;
226 :
227 : int allclean;
228 :
229 : atomic_t behind_writes;
230 :
231 : /*
232 : * the bitmap daemon - periodically wakes up and sweeps the bitmap
233 : * file, cleaning up bits and flushing out pages to disk as necessary
234 : */
235 : unsigned long daemon_lastrun; /* jiffies of last run */
236 : unsigned long last_end_sync; /* when we lasted called end_sync to
237 : * update bitmap with resync progress */
238 :
239 : atomic_t pending_writes; /* pending writes to the bitmap file */
240 : wait_queue_head_t write_wait;
241 : wait_queue_head_t overflow_wait;
242 :
243 : struct sysfs_dirent *sysfs_can_clear;
244 : };
245 :
246 : /* the bitmap API */
247 :
248 : /* these are used only by md/bitmap */
249 : int bitmap_create(mddev_t *mddev);
250 : void bitmap_flush(mddev_t *mddev);
251 : void bitmap_destroy(mddev_t *mddev);
252 :
253 : void bitmap_print_sb(struct bitmap *bitmap);
254 : void bitmap_update_sb(struct bitmap *bitmap);
255 :
256 : int bitmap_setallbits(struct bitmap *bitmap);
257 : void bitmap_write_all(struct bitmap *bitmap);
258 :
259 : void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);
260 :
261 : /* these are exported */
262 : int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
263 : unsigned long sectors, int behind);
264 : void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
265 : unsigned long sectors, int success, int behind);
266 : int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int degraded);
267 : void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
268 : void bitmap_close_sync(struct bitmap *bitmap);
269 : void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);
270 :
271 : void bitmap_unplug(struct bitmap *bitmap);
272 : void bitmap_daemon_work(mddev_t *mddev);
273 : #endif
274 :
275 : #endif
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