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 17struct dm_bufio_client; 18struct dm_buffer; 19 20/* 21 * Create a buffered IO cache on a given device 22 */ 23struct dm_bufio_client * 24dm_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 */ 32void 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 */ 48void *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 */ 55void *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 */ 62void *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 */ 70void 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 The data 75 * pointer and dm_buffer pointer is no longer valid after this call. 76 */ 77void dm_bufio_release(struct dm_buffer *b); 78 79/* 80 * Mark a buffer dirty.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 */ 87void dm_bufio_mark_buffer_dirty(struct dm_buffer *b); 88 89/* 90 * Initiate writing of dirty buffers, without waiting for completion. 91 */ 92void 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 */ 98int 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 */ 103int 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 */ 109void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block); 110 111unsigned dm_bufio_get_block_size(struct dm_bufio_client *c); 112sector_t dm_bufio_get_device_size(struct dm_bufio_client *c); 113sector_t dm_bufio_get_block_number(struct dm_buffer *b); 114void *dm_bufio_get_block_data(struct dm_buffer *b); 115void *dm_bufio_get_aux_data(struct dm_buffer *b); 116struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b); 117 118/*----------------------------------------------------------------*/ 119 120#endif 121