1 /* 2 * Copyright (C) 2011 Red Hat, Inc. 3 * 4 * This file is released under the GPL. 5 */ 6 7 #ifndef _LINUX_DM_BLOCK_MANAGER_H 8 #define _LINUX_DM_BLOCK_MANAGER_H 9 10 #include <linux/types.h> 11 #include <linux/blkdev.h> 12 13 /*----------------------------------------------------------------*/ 14 15 /* 16 * Block number. 17 */ 18 typedef uint64_t dm_block_t; 19 struct dm_block; 20 21 dm_block_t dm_block_location(struct dm_block *b); 22 void *dm_block_data(struct dm_block *b); 23 24 /*----------------------------------------------------------------*/ 25 26 /* 27 * @name should be a unique identifier for the block manager, no longer 28 * than 32 chars. 29 * 30 * @max_held_per_thread should be the maximum number of locks, read or 31 * write, that an individual thread holds at any one time. 32 */ 33 struct dm_block_manager; 34 struct dm_block_manager *dm_block_manager_create( 35 struct block_device *bdev, unsigned block_size, 36 unsigned cache_size, unsigned max_held_per_thread); 37 void dm_block_manager_destroy(struct dm_block_manager *bm); 38 39 unsigned dm_bm_block_size(struct dm_block_manager *bm); 40 dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm); 41 42 /*----------------------------------------------------------------*/ 43 44 /* 45 * The validator allows the caller to verify newly-read data and modify 46 * the data just before writing, e.g. to calculate checksums. It's 47 * important to be consistent with your use of validators. The only time 48 * you can change validators is if you call dm_bm_write_lock_zero. 49 */ 50 struct dm_block_validator { 51 const char *name; 52 void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size); 53 54 /* 55 * Return 0 if the checksum is valid or < 0 on error. 56 */ 57 int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size); 58 }; 59 60 /*----------------------------------------------------------------*/ 61 62 /* 63 * You can have multiple concurrent readers or a single writer holding a 64 * block lock. 65 */ 66 67 /* 68 * dm_bm_lock() locks a block and returns through @result a pointer to 69 * memory that holds a copy of that block. If you have write-locked the 70 * block then any changes you make to memory pointed to by @result will be 71 * written back to the disk sometime after dm_bm_unlock is called. 72 */ 73 int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b, 74 struct dm_block_validator *v, 75 struct dm_block **result); 76 77 int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b, 78 struct dm_block_validator *v, 79 struct dm_block **result); 80 81 /* 82 * The *_try_lock variants return -EWOULDBLOCK if the block isn't 83 * available immediately. 84 */ 85 int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b, 86 struct dm_block_validator *v, 87 struct dm_block **result); 88 89 /* 90 * Use dm_bm_write_lock_zero() when you know you're going to 91 * overwrite the block completely. It saves a disk read. 92 */ 93 int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b, 94 struct dm_block_validator *v, 95 struct dm_block **result); 96 97 int dm_bm_unlock(struct dm_block *b); 98 99 /* 100 * An optimisation; we often want to copy a block's contents to a new 101 * block. eg, as part of the shadowing operation. It's far better for 102 * bufio to do this move behind the scenes than hold 2 locks and memcpy the 103 * data. 104 */ 105 int dm_bm_unlock_move(struct dm_block *b, dm_block_t n); 106 107 /* 108 * It's a common idiom to have a superblock that should be committed last. 109 * 110 * @superblock should be write-locked on entry. It will be unlocked during 111 * this function. All dirty blocks are guaranteed to be written and flushed 112 * before the superblock. 113 * 114 * This method always blocks. 115 */ 116 int dm_bm_flush_and_unlock(struct dm_block_manager *bm, 117 struct dm_block *superblock); 118 119 u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor); 120 121 /*----------------------------------------------------------------*/ 122 123 #endif /* _LINUX_DM_BLOCK_MANAGER_H */ 124