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 kernfs_node *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