1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * Copyright (C) 2011 Red Hat, Inc. 4 * 5 * This file is released under the GPL. 6 */ 7 8 #ifndef _LINUX_DM_BLOCK_MANAGER_H 9 #define _LINUX_DM_BLOCK_MANAGER_H 10 11 #include <linux/types.h> 12 #include <linux/blkdev.h> 13 14 /*----------------------------------------------------------------*/ 15 16 /* 17 * Block number. 18 */ 19 typedef uint64_t dm_block_t; 20 struct dm_block; 21 22 dm_block_t dm_block_location(struct dm_block *b); 23 void *dm_block_data(struct dm_block *b); 24 25 /*----------------------------------------------------------------*/ 26 27 /* 28 * @name should be a unique identifier for the block manager, no longer 29 * than 32 chars. 30 * 31 * @max_held_per_thread should be the maximum number of locks, read or 32 * write, that an individual thread holds at any one time. 33 */ 34 struct dm_block_manager; 35 struct dm_block_manager *dm_block_manager_create( 36 struct block_device *bdev, unsigned int block_size, 37 unsigned int max_held_per_thread); 38 void dm_block_manager_destroy(struct dm_block_manager *bm); 39 void dm_block_manager_reset(struct dm_block_manager *bm); 40 41 unsigned int dm_bm_block_size(struct dm_block_manager *bm); 42 dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm); 43 44 /*----------------------------------------------------------------*/ 45 46 /* 47 * The validator allows the caller to verify newly-read data and modify 48 * the data just before writing, e.g. to calculate checksums. It's 49 * important to be consistent with your use of validators. The only time 50 * you can change validators is if you call dm_bm_write_lock_zero. 51 */ 52 struct dm_block_validator { 53 const char *name; 54 void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size); 55 56 /* 57 * Return 0 if the checksum is valid or < 0 on error. 58 */ 59 int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size); 60 }; 61 62 /*----------------------------------------------------------------*/ 63 64 /* 65 * You can have multiple concurrent readers or a single writer holding a 66 * block lock. 67 */ 68 69 /* 70 * dm_bm_lock() locks a block and returns through @result a pointer to 71 * memory that holds a copy of that block. If you have write-locked the 72 * block then any changes you make to memory pointed to by @result will be 73 * written back to the disk sometime after dm_bm_unlock is called. 74 */ 75 int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b, 76 struct dm_block_validator *v, 77 struct dm_block **result); 78 79 int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b, 80 struct dm_block_validator *v, 81 struct dm_block **result); 82 83 /* 84 * The *_try_lock variants return -EWOULDBLOCK if the block isn't 85 * available immediately. 86 */ 87 int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b, 88 struct dm_block_validator *v, 89 struct dm_block **result); 90 91 /* 92 * Use dm_bm_write_lock_zero() when you know you're going to 93 * overwrite the block completely. It saves a disk read. 94 */ 95 int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b, 96 struct dm_block_validator *v, 97 struct dm_block **result); 98 99 void dm_bm_unlock(struct dm_block *b); 100 101 /* 102 * It's a common idiom to have a superblock that should be committed last. 103 * 104 * @superblock should be write-locked on entry. It will be unlocked during 105 * this function. All dirty blocks are guaranteed to be written and flushed 106 * before the superblock. 107 * 108 * This method always blocks. 109 */ 110 int dm_bm_flush(struct dm_block_manager *bm); 111 112 /* 113 * Request data is prefetched into the cache. 114 */ 115 void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b); 116 117 /* 118 * Switches the bm to a read only mode. Once read-only mode 119 * has been entered the following functions will return -EPERM. 120 * 121 * dm_bm_write_lock 122 * dm_bm_write_lock_zero 123 * dm_bm_flush_and_unlock 124 * 125 * Additionally you should not use dm_bm_unlock_move, however no error will 126 * be returned if you do. 127 */ 128 bool dm_bm_is_read_only(struct dm_block_manager *bm); 129 void dm_bm_set_read_only(struct dm_block_manager *bm); 130 void dm_bm_set_read_write(struct dm_block_manager *bm); 131 132 u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor); 133 134 /*----------------------------------------------------------------*/ 135 136 #endif /* _LINUX_DM_BLOCK_MANAGER_H */ 137