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 
83 typedef __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 */
113 enum bitmap_state {
114 	BITMAP_STALE  = 0x002,  /* the bitmap file is out of date or had -EIO */
115 	BITMAP_WRITE_ERROR = 0x004, /* A write error has occurred */
116 	BITMAP_HOSTENDIAN = 0x8000,
117 };
118 
119 /* the superblock at the front of the bitmap file -- little endian */
120 typedef 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 
132 	__u8  pad[256 - 64]; /* set to zero */
133 } bitmap_super_t;
134 
135 /* notes:
136  * (1) This event counter is updated before the eventcounter in the md superblock
137  *    When a bitmap is loaded, it is only accepted if this event counter is equal
138  *    to, or one greater than, the event counter in the superblock.
139  * (2) This event counter is updated when the other one is *if*and*only*if* the
140  *    array is not degraded.  As bits are not cleared when the array is degraded,
141  *    this represents the last time that any bits were cleared.
142  *    If a device is being added that has an event count with this value or
143  *    higher, it is accepted as conforming to the bitmap.
144  * (3)This is the number of sectors represented by the bitmap, and is the range that
145  *    resync happens across.  For raid1 and raid5/6 it is the size of individual
146  *    devices.  For raid10 it is the size of the array.
147  */
148 
149 #ifdef __KERNEL__
150 
151 /* the in-memory bitmap is represented by bitmap_pages */
152 struct bitmap_page {
153 	/*
154 	 * map points to the actual memory page
155 	 */
156 	char *map;
157 	/*
158 	 * in emergencies (when map cannot be alloced), hijack the map
159 	 * pointer and use it as two counters itself
160 	 */
161 	unsigned int hijacked:1;
162 	/*
163 	 * count of dirty bits on the page
164 	 */
165 	unsigned int  count:31;
166 };
167 
168 /* the main bitmap structure - one per mddev */
169 struct bitmap {
170 	struct bitmap_page *bp;
171 	unsigned long pages; /* total number of pages in the bitmap */
172 	unsigned long missing_pages; /* number of pages not yet allocated */
173 
174 	struct mddev *mddev; /* the md device that the bitmap is for */
175 
176 	/* bitmap chunksize -- how much data does each bit represent? */
177 	unsigned long chunkshift; /* chunksize = 2^(chunkshift+9) (for bitops) */
178 	unsigned long chunks; /* total number of data chunks for the array */
179 
180 	__u64	events_cleared;
181 	int need_sync;
182 
183 	/* bitmap spinlock */
184 	spinlock_t lock;
185 
186 	struct file *file; /* backing disk file */
187 	struct page *sb_page; /* cached copy of the bitmap file superblock */
188 	struct page **filemap; /* list of cache pages for the file */
189 	unsigned long *filemap_attr; /* attributes associated w/ filemap pages */
190 	unsigned long file_pages; /* number of pages in the file */
191 	int last_page_size; /* bytes in the last page */
192 
193 	unsigned long flags;
194 
195 	int allclean;
196 
197 	atomic_t behind_writes;
198 	unsigned long behind_writes_used; /* highest actual value at runtime */
199 
200 	/*
201 	 * the bitmap daemon - periodically wakes up and sweeps the bitmap
202 	 * file, cleaning up bits and flushing out pages to disk as necessary
203 	 */
204 	unsigned long daemon_lastrun; /* jiffies of last run */
205 	unsigned long last_end_sync; /* when we lasted called end_sync to
206 				      * update bitmap with resync progress */
207 
208 	atomic_t pending_writes; /* pending writes to the bitmap file */
209 	wait_queue_head_t write_wait;
210 	wait_queue_head_t overflow_wait;
211 	wait_queue_head_t behind_wait;
212 
213 	struct sysfs_dirent *sysfs_can_clear;
214 };
215 
216 /* the bitmap API */
217 
218 /* these are used only by md/bitmap */
219 int  bitmap_create(struct mddev *mddev);
220 int bitmap_load(struct mddev *mddev);
221 void bitmap_flush(struct mddev *mddev);
222 void bitmap_destroy(struct mddev *mddev);
223 
224 void bitmap_print_sb(struct bitmap *bitmap);
225 void bitmap_update_sb(struct bitmap *bitmap);
226 void bitmap_status(struct seq_file *seq, struct bitmap *bitmap);
227 
228 int  bitmap_setallbits(struct bitmap *bitmap);
229 void bitmap_write_all(struct bitmap *bitmap);
230 
231 void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);
232 
233 /* these are exported */
234 int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
235 			unsigned long sectors, int behind);
236 void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
237 			unsigned long sectors, int success, int behind);
238 int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int degraded);
239 void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted);
240 void bitmap_close_sync(struct bitmap *bitmap);
241 void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector);
242 
243 void bitmap_unplug(struct bitmap *bitmap);
244 void bitmap_daemon_work(struct mddev *mddev);
245 #endif
246 
247 #endif
248