Root/drivers/md/bitmap.h

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

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