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/*
* bitmap.h: Copyright (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
*
* additions: Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.
*/
#ifndef BITMAP_H
#define BITMAP_H 1
#define BITMAP_MAJOR_LO 3
/* version 4 insists the bitmap is in little-endian order
* with version 3, it is host-endian which is non-portable
*/
#define BITMAP_MAJOR_HI 4
#define BITMAP_MAJOR_HOSTENDIAN 3
#define BITMAP_MINOR 39
/*
* in-memory bitmap:
*
* Use 16 bit block counters to track pending writes to each "chunk".
* The 2 high order bits are special-purpose, the first is a flag indicating
* whether a resync is needed. The second is a flag indicating whether a
* resync is active.
* This means that the counter is actually 14 bits:
*
* +--------+--------+------------------------------------------------+
* | resync | resync | counter |
* | needed | active | |
* | (0-1) | (0-1) | (0-16383) |
* +--------+--------+------------------------------------------------+
*
* The "resync needed" bit is set when:
* a '1' bit is read from storage at startup.
* a write request fails on some drives
* a resync is aborted on a chunk with 'resync active' set
* It is cleared (and resync-active set) when a resync starts across all drives
* of the chunk.
*
*
* The "resync active" bit is set when:
* a resync is started on all drives, and resync_needed is set.
* resync_needed will be cleared (as long as resync_active wasn't already set).
* It is cleared when a resync completes.
*
* The counter counts pending write requests, plus the on-disk bit.
* When the counter is '1' and the resync bits are clear, the on-disk
* bit can be cleared aswell, thus setting the counter to 0.
* When we set a bit, or in the counter (to start a write), if the fields is
* 0, we first set the disk bit and set the counter to 1.
*
* If the counter is 0, the on-disk bit is clear and the stipe is clean
* Anything that dirties the stipe pushes the counter to 2 (at least)
* and sets the on-disk bit (lazily).
* If a periodic sweep find the counter at 2, it is decremented to 1.
* If the sweep find the counter at 1, the on-disk bit is cleared and the
* counter goes to zero.
*
* Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
* counters as a fallback when "page" memory cannot be allocated:
*
* Normal case (page memory allocated):
*
* page pointer (32-bit)
*
* [ ] ------+
* |
* +-------> [ ][ ]..[ ] (4096 byte page == 2048 counters)
* c1 c2 c2048
*
* Hijacked case (page memory allocation failed):
*
* hijacked page pointer (32-bit)
*
* [ ][ ] (no page memory allocated)
* counter #1 (16-bit) counter #2 (16-bit)
*
*/
#ifdef __KERNEL__
#define PAGE_BITS (PAGE_SIZE << 3)
#define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
typedef __u16 bitmap_counter_t;
#define COUNTER_BITS 16
#define COUNTER_BIT_SHIFT 4
#define COUNTER_BYTE_RATIO (COUNTER_BITS / 8)
#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
#define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
#define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
#define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
/* how many counters per page? */
#define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
/* same, except a shift value for more efficient bitops */
#define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
/* same, except a mask value for more efficient bitops */
#define PAGE_COUNTER_MASK (PAGE_COUNTER_RATIO - 1)
#define BITMAP_BLOCK_SIZE 512
#define BITMAP_BLOCK_SHIFT 9
/* how many blocks per chunk? (this is variable) */
#define CHUNK_BLOCK_RATIO(bitmap) ((bitmap)->chunksize >> BITMAP_BLOCK_SHIFT)
#define CHUNK_BLOCK_SHIFT(bitmap) ((bitmap)->chunkshift - BITMAP_BLOCK_SHIFT)
#define CHUNK_BLOCK_MASK(bitmap) (CHUNK_BLOCK_RATIO(bitmap) - 1)
/* when hijacked, the counters and bits represent even larger "chunks" */
/* there will be 1024 chunks represented by each counter in the page pointers */
#define PAGEPTR_BLOCK_RATIO(bitmap) \
(CHUNK_BLOCK_RATIO(bitmap) << PAGE_COUNTER_SHIFT >> 1)
#define PAGEPTR_BLOCK_SHIFT(bitmap) \
(CHUNK_BLOCK_SHIFT(bitmap) + PAGE_COUNTER_SHIFT - 1)
#define PAGEPTR_BLOCK_MASK(bitmap) (PAGEPTR_BLOCK_RATIO(bitmap) - 1)
/*
* on-disk bitmap:
*
* Use one bit per "chunk" (block set). We do the disk I/O on the bitmap
* file a page at a time. There's a superblock at the start of the file.
*/
/* map chunks (bits) to file pages - offset by the size of the superblock */
#define CHUNK_BIT_OFFSET(chunk) ((chunk) + (sizeof(bitmap_super_t) << 3))
#endif
/*
* bitmap structures:
*/
#define BITMAP_MAGIC 0x6d746962
/* use these for bitmap->flags and bitmap->sb->state bit-fields */
enum bitmap_state {
BITMAP_ACTIVE = 0x001, /* the bitmap is in use */
BITMAP_STALE = 0x002 /* the bitmap file is out of date or had -EIO */
};
/* the superblock at the front of the bitmap file -- little endian */
typedef struct bitmap_super_s {
__u32 magic; /* 0 BITMAP_MAGIC */
__u32 version; /* 4 the bitmap major for now, could change... */
__u8 uuid[16]; /* 8 128 bit uuid - must match md device uuid */
__u64 events; /* 24 event counter for the bitmap (1)*/
__u64 events_cleared;/*32 event counter when last bit cleared (2) */
__u64 sync_size; /* 40 the size of the md device's sync range(3) */
__u32 state; /* 48 bitmap state information */
__u32 chunksize; /* 52 the bitmap chunk size in bytes */
__u32 daemon_sleep; /* 56 seconds between disk flushes */
__u32 write_behind; /* 60 number of outstanding write-behind writes */
__u8 pad[256 - 64]; /* set to zero */
} bitmap_super_t;
/* notes:
* (1) This event counter is updated before the eventcounter in the md superblock
* When a bitmap is loaded, it is only accepted if this event counter is equal
* to, or one greater than, the event counter in the superblock.
* (2) This event counter is updated when the other one is *if*and*only*if* the
* array is not degraded. As bits are not cleared when the array is degraded,
* this represents the last time that any bits were cleared.
* If a device is being added that has an event count with this value or
* higher, it is accepted as conforming to the bitmap.
* (3)This is the number of sectors represented by the bitmap, and is the range that
* resync happens across. For raid1 and raid5/6 it is the size of individual
* devices. For raid10 it is the size of the array.
*/
#ifdef __KERNEL__
/* the in-memory bitmap is represented by bitmap_pages */
struct bitmap_page {
/*
* map points to the actual memory page
*/
char *map;
/*
* in emergencies (when map cannot be alloced), hijack the map
* pointer and use it as two counters itself
*/
unsigned int hijacked;
/*
* count of dirty bits on the page
*/
int count;
};
/* keep track of bitmap file pages that have pending writes on them */
struct page_list {
struct list_head list;
struct page *page;
};
/* the main bitmap structure - one per mddev */
struct bitmap {
struct bitmap_page *bp;
unsigned long pages; /* total number of pages in the bitmap */
unsigned long missing_pages; /* number of pages not yet allocated */
mddev_t *mddev; /* the md device that the bitmap is for */
int counter_bits; /* how many bits per block counter */
/* bitmap chunksize -- how much data does each bit represent? */
unsigned long chunksize;
unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */
unsigned long chunks; /* total number of data chunks for the array */
/* We hold a count on the chunk currently being synced, and drop
* it when the last block is started. If the resync is aborted
* midway, we need to be able to drop that count, so we remember
* the counted chunk..
*/
unsigned long syncchunk;
__u64 events_cleared;
/* bitmap spinlock */
spinlock_t lock;
struct file *file; /* backing disk file */
struct page *sb_page; /* cached copy of the bitmap file superblock */
struct page **filemap; /* list of cache pages for the file */
unsigned long *filemap_attr; /* attributes associated w/ filemap pages */
unsigned long file_pages; /* number of pages in the file */
unsigned long flags;
/*
* the bitmap daemon - periodically wakes up and sweeps the bitmap
* file, cleaning up bits and flushing out pages to disk as necessary
*/
mdk_thread_t *daemon;
unsigned long daemon_sleep; /* how many seconds between updates? */
/*
* bitmap write daemon - this daemon performs writes to the bitmap file
* this thread is only needed because of a limitation in ext3 (jbd)
* that does not allow a task to have two journal transactions ongoing
* simultaneously (even if the transactions are for two different
* filesystems) -- in the case of bitmap, that would be the filesystem
* that the bitmap file resides on and the filesystem that is mounted
* on the md device -- see current->journal_info in jbd/transaction.c
*/
mdk_thread_t *write_daemon;
mdk_thread_t *writeback_daemon;
spinlock_t write_lock;
struct semaphore write_ready;
struct semaphore write_done;
unsigned long writes_pending;
wait_queue_head_t write_wait;
struct list_head write_pages;
struct list_head complete_pages;
mempool_t *write_pool;
};
/* the bitmap API */
/* these are used only by md/bitmap */
int bitmap_create(mddev_t *mddev);
void bitmap_destroy(mddev_t *mddev);
int bitmap_active(struct bitmap *bitmap);
char *file_path(struct file *file, char *buf, int count);
void bitmap_print_sb(struct bitmap *bitmap);
int bitmap_update_sb(struct bitmap *bitmap);
int bitmap_setallbits(struct bitmap *bitmap);
/* these are exported */
void bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors);
void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
int success);
int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks);
void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
void bitmap_close_sync(struct bitmap *bitmap);
int bitmap_unplug(struct bitmap *bitmap);
#endif
#endif