280 lines
10 KiB
C
280 lines
10 KiB
C
/*
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* bitmap.h: Copyright (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
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*
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* additions: Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.
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*/
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#ifndef BITMAP_H
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#define BITMAP_H 1
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#define BITMAP_MAJOR 3
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#define BITMAP_MINOR 39
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/*
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* in-memory bitmap:
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*
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* Use 16 bit block counters to track pending writes to each "chunk".
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* The 2 high order bits are special-purpose, the first is a flag indicating
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* whether a resync is needed. The second is a flag indicating whether a
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* resync is active.
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* This means that the counter is actually 14 bits:
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*
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* +--------+--------+------------------------------------------------+
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* | resync | resync | counter |
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* | needed | active | |
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* | (0-1) | (0-1) | (0-16383) |
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* +--------+--------+------------------------------------------------+
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*
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* The "resync needed" bit is set when:
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* a '1' bit is read from storage at startup.
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* a write request fails on some drives
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* a resync is aborted on a chunk with 'resync active' set
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* It is cleared (and resync-active set) when a resync starts across all drives
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* of the chunk.
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*
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*
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* The "resync active" bit is set when:
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* a resync is started on all drives, and resync_needed is set.
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* resync_needed will be cleared (as long as resync_active wasn't already set).
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* It is cleared when a resync completes.
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*
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* The counter counts pending write requests, plus the on-disk bit.
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* When the counter is '1' and the resync bits are clear, the on-disk
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* bit can be cleared aswell, thus setting the counter to 0.
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* When we set a bit, or in the counter (to start a write), if the fields is
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* 0, we first set the disk bit and set the counter to 1.
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*
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* If the counter is 0, the on-disk bit is clear and the stipe is clean
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* Anything that dirties the stipe pushes the counter to 2 (at least)
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* and sets the on-disk bit (lazily).
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* If a periodic sweep find the counter at 2, it is decremented to 1.
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* If the sweep find the counter at 1, the on-disk bit is cleared and the
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* counter goes to zero.
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*
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* Also, we'll hijack the "map" pointer itself and use it as two 16 bit block
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* counters as a fallback when "page" memory cannot be allocated:
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*
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* Normal case (page memory allocated):
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*
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* page pointer (32-bit)
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*
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* [ ] ------+
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* |
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* +-------> [ ][ ]..[ ] (4096 byte page == 2048 counters)
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* c1 c2 c2048
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*
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* Hijacked case (page memory allocation failed):
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*
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* hijacked page pointer (32-bit)
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*
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* [ ][ ] (no page memory allocated)
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* counter #1 (16-bit) counter #2 (16-bit)
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*
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*/
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#ifdef __KERNEL__
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#define PAGE_BITS (PAGE_SIZE << 3)
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#define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
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typedef __u16 bitmap_counter_t;
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#define COUNTER_BITS 16
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#define COUNTER_BIT_SHIFT 4
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#define COUNTER_BYTE_RATIO (COUNTER_BITS / 8)
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#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
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#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
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#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
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#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
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#define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
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#define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
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#define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
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/* how many counters per page? */
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#define PAGE_COUNTER_RATIO (PAGE_BITS / COUNTER_BITS)
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/* same, except a shift value for more efficient bitops */
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#define PAGE_COUNTER_SHIFT (PAGE_BIT_SHIFT - COUNTER_BIT_SHIFT)
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/* same, except a mask value for more efficient bitops */
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#define PAGE_COUNTER_MASK (PAGE_COUNTER_RATIO - 1)
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#define BITMAP_BLOCK_SIZE 512
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#define BITMAP_BLOCK_SHIFT 9
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/* how many blocks per chunk? (this is variable) */
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#define CHUNK_BLOCK_RATIO(bitmap) ((bitmap)->chunksize >> BITMAP_BLOCK_SHIFT)
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#define CHUNK_BLOCK_SHIFT(bitmap) ((bitmap)->chunkshift - BITMAP_BLOCK_SHIFT)
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#define CHUNK_BLOCK_MASK(bitmap) (CHUNK_BLOCK_RATIO(bitmap) - 1)
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/* when hijacked, the counters and bits represent even larger "chunks" */
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/* there will be 1024 chunks represented by each counter in the page pointers */
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#define PAGEPTR_BLOCK_RATIO(bitmap) \
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(CHUNK_BLOCK_RATIO(bitmap) << PAGE_COUNTER_SHIFT >> 1)
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#define PAGEPTR_BLOCK_SHIFT(bitmap) \
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(CHUNK_BLOCK_SHIFT(bitmap) + PAGE_COUNTER_SHIFT - 1)
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#define PAGEPTR_BLOCK_MASK(bitmap) (PAGEPTR_BLOCK_RATIO(bitmap) - 1)
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/*
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* on-disk bitmap:
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*
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* Use one bit per "chunk" (block set). We do the disk I/O on the bitmap
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* file a page at a time. There's a superblock at the start of the file.
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*/
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/* map chunks (bits) to file pages - offset by the size of the superblock */
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#define CHUNK_BIT_OFFSET(chunk) ((chunk) + (sizeof(bitmap_super_t) << 3))
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#endif
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/*
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* bitmap structures:
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*/
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#define BITMAP_MAGIC 0x6d746962
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/* use these for bitmap->flags and bitmap->sb->state bit-fields */
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enum bitmap_state {
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BITMAP_ACTIVE = 0x001, /* the bitmap is in use */
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BITMAP_STALE = 0x002 /* the bitmap file is out of date or had -EIO */
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};
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/* the superblock at the front of the bitmap file -- little endian */
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typedef struct bitmap_super_s {
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__u32 magic; /* 0 BITMAP_MAGIC */
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__u32 version; /* 4 the bitmap major for now, could change... */
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__u8 uuid[16]; /* 8 128 bit uuid - must match md device uuid */
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__u64 events; /* 24 event counter for the bitmap (1)*/
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__u64 events_cleared;/*32 event counter when last bit cleared (2) */
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__u64 sync_size; /* 40 the size of the md device's sync range(3) */
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__u32 state; /* 48 bitmap state information */
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__u32 chunksize; /* 52 the bitmap chunk size in bytes */
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__u32 daemon_sleep; /* 56 seconds between disk flushes */
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__u32 write_behind; /* 60 number of outstanding write-behind writes */
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__u8 pad[256 - 64]; /* set to zero */
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} bitmap_super_t;
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/* notes:
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* (1) This event counter is updated before the eventcounter in the md superblock
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* When a bitmap is loaded, it is only accepted if this event counter is equal
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* to, or one greater than, the event counter in the superblock.
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* (2) This event counter is updated when the other one is *if*and*only*if* the
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* array is not degraded. As bits are not cleared when the array is degraded,
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* this represents the last time that any bits were cleared.
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* If a device is being added that has an event count with this value or
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* higher, it is accepted as conforming to the bitmap.
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* (3)This is the number of sectors represented by the bitmap, and is the range that
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* resync happens across. For raid1 and raid5/6 it is the size of individual
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* devices. For raid10 it is the size of the array.
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*/
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#ifdef __KERNEL__
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/* the in-memory bitmap is represented by bitmap_pages */
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struct bitmap_page {
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/*
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* map points to the actual memory page
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*/
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char *map;
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/*
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* in emergencies (when map cannot be alloced), hijack the map
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* pointer and use it as two counters itself
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*/
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unsigned int hijacked:1;
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/*
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* count of dirty bits on the page
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*/
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unsigned int count:31;
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};
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/* keep track of bitmap file pages that have pending writes on them */
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struct page_list {
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struct list_head list;
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struct page *page;
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};
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/* the main bitmap structure - one per mddev */
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struct bitmap {
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struct bitmap_page *bp;
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unsigned long pages; /* total number of pages in the bitmap */
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unsigned long missing_pages; /* number of pages not yet allocated */
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mddev_t *mddev; /* the md device that the bitmap is for */
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int counter_bits; /* how many bits per block counter */
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/* bitmap chunksize -- how much data does each bit represent? */
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unsigned long chunksize;
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unsigned long chunkshift; /* chunksize = 2^chunkshift (for bitops) */
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unsigned long chunks; /* total number of data chunks for the array */
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/* We hold a count on the chunk currently being synced, and drop
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* it when the last block is started. If the resync is aborted
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* midway, we need to be able to drop that count, so we remember
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* the counted chunk..
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*/
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unsigned long syncchunk;
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__u64 events_cleared;
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/* bitmap spinlock */
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spinlock_t lock;
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long offset; /* offset from superblock if file is NULL */
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struct file *file; /* backing disk file */
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struct page *sb_page; /* cached copy of the bitmap file superblock */
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struct page **filemap; /* list of cache pages for the file */
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unsigned long *filemap_attr; /* attributes associated w/ filemap pages */
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unsigned long file_pages; /* number of pages in the file */
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unsigned long flags;
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unsigned long max_write_behind; /* write-behind mode */
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atomic_t behind_writes;
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/*
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* the bitmap daemon - periodically wakes up and sweeps the bitmap
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* file, cleaning up bits and flushing out pages to disk as necessary
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*/
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unsigned long daemon_lastrun; /* jiffies of last run */
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unsigned long daemon_sleep; /* how many seconds between updates? */
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/*
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* bitmap_writeback_daemon waits for file-pages that have been written,
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* as there is no way to get a call-back when a page write completes.
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*/
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mdk_thread_t *writeback_daemon;
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spinlock_t write_lock;
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wait_queue_head_t write_wait;
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struct list_head complete_pages;
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mempool_t *write_pool;
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};
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/* the bitmap API */
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/* these are used only by md/bitmap */
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int bitmap_create(mddev_t *mddev);
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void bitmap_flush(mddev_t *mddev);
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void bitmap_destroy(mddev_t *mddev);
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int bitmap_active(struct bitmap *bitmap);
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char *file_path(struct file *file, char *buf, int count);
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void bitmap_print_sb(struct bitmap *bitmap);
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int bitmap_update_sb(struct bitmap *bitmap);
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int bitmap_setallbits(struct bitmap *bitmap);
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void bitmap_write_all(struct bitmap *bitmap);
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/* these are exported */
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int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
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unsigned long sectors, int behind);
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void bitmap_endwrite(struct bitmap *bitmap, sector_t offset,
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unsigned long sectors, int success, int behind);
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int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int degraded);
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void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted);
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void bitmap_close_sync(struct bitmap *bitmap);
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int bitmap_unplug(struct bitmap *bitmap);
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int bitmap_daemon_work(struct bitmap *bitmap);
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#endif
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#endif
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