1 /* 2 * Copyright (C) 2009-2011 Red Hat, Inc. 3 * 4 * Author: Mikulas Patocka <mpatocka@redhat.com> 5 * 6 * This file is released under the GPL. 7 */ 8 9 #ifndef DM_BUFIO_H 10 #define DM_BUFIO_H 11 12 #include <linux/blkdev.h> 13 #include <linux/types.h> 14 15 /*----------------------------------------------------------------*/ 16 17 struct dm_bufio_client; 18 struct dm_buffer; 19 20 /* 21 * Create a buffered IO cache on a given device 22 */ 23 struct dm_bufio_client * 24 dm_bufio_client_create(struct block_device *bdev, unsigned block_size, 25 unsigned reserved_buffers, unsigned aux_size, 26 void (*alloc_callback)(struct dm_buffer *), 27 void (*write_callback)(struct dm_buffer *)); 28 29 /* 30 * Release a buffered IO cache. 31 */ 32 void dm_bufio_client_destroy(struct dm_bufio_client *c); 33 34 /* 35 * WARNING: to avoid deadlocks, these conditions are observed: 36 * 37 * - At most one thread can hold at most "reserved_buffers" simultaneously. 38 * - Each other threads can hold at most one buffer. 39 * - Threads which call only dm_bufio_get can hold unlimited number of 40 * buffers. 41 */ 42 43 /* 44 * Read a given block from disk. Returns pointer to data. Returns a 45 * pointer to dm_buffer that can be used to release the buffer or to make 46 * it dirty. 47 */ 48 void *dm_bufio_read(struct dm_bufio_client *c, sector_t block, 49 struct dm_buffer **bp); 50 51 /* 52 * Like dm_bufio_read, but return buffer from cache, don't read 53 * it. If the buffer is not in the cache, return NULL. 54 */ 55 void *dm_bufio_get(struct dm_bufio_client *c, sector_t block, 56 struct dm_buffer **bp); 57 58 /* 59 * Like dm_bufio_read, but don't read anything from the disk. It is 60 * expected that the caller initializes the buffer and marks it dirty. 61 */ 62 void *dm_bufio_new(struct dm_bufio_client *c, sector_t block, 63 struct dm_buffer **bp); 64 65 /* 66 * Prefetch the specified blocks to the cache. 67 * The function starts to read the blocks and returns without waiting for 68 * I/O to finish. 69 */ 70 void dm_bufio_prefetch(struct dm_bufio_client *c, 71 sector_t block, unsigned n_blocks); 72 73 /* 74 * Release a reference obtained with dm_bufio_{read,get,new}. The data 75 * pointer and dm_buffer pointer is no longer valid after this call. 76 */ 77 void dm_bufio_release(struct dm_buffer *b); 78 79 /* 80 * Mark a buffer dirty. It should be called after the buffer is modified. 81 * 82 * In case of memory pressure, the buffer may be written after 83 * dm_bufio_mark_buffer_dirty, but before dm_bufio_write_dirty_buffers. So 84 * dm_bufio_write_dirty_buffers guarantees that the buffer is on-disk but 85 * the actual writing may occur earlier. 86 */ 87 void dm_bufio_mark_buffer_dirty(struct dm_buffer *b); 88 89 /* 90 * Initiate writing of dirty buffers, without waiting for completion. 91 */ 92 void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c); 93 94 /* 95 * Write all dirty buffers. Guarantees that all dirty buffers created prior 96 * to this call are on disk when this call exits. 97 */ 98 int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c); 99 100 /* 101 * Send an empty write barrier to the device to flush hardware disk cache. 102 */ 103 int dm_bufio_issue_flush(struct dm_bufio_client *c); 104 105 /* 106 * Like dm_bufio_release but also move the buffer to the new 107 * block. dm_bufio_write_dirty_buffers is needed to commit the new block. 108 */ 109 void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block); 110 111 /* 112 * Free the given buffer. 113 * This is just a hint, if the buffer is in use or dirty, this function 114 * does nothing. 115 */ 116 void dm_bufio_forget(struct dm_bufio_client *c, sector_t block); 117 118 /* 119 * Set the minimum number of buffers before cleanup happens. 120 */ 121 void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n); 122 123 unsigned dm_bufio_get_block_size(struct dm_bufio_client *c); 124 sector_t dm_bufio_get_device_size(struct dm_bufio_client *c); 125 sector_t dm_bufio_get_block_number(struct dm_buffer *b); 126 void *dm_bufio_get_block_data(struct dm_buffer *b); 127 void *dm_bufio_get_aux_data(struct dm_buffer *b); 128 struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b); 129 130 /*----------------------------------------------------------------*/ 131 132 #endif 133