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Diffstat (limited to 'cpukit/libblock/include/rtems/bdbuf.h')
| -rw-r--r-- | cpukit/libblock/include/rtems/bdbuf.h | 282 |
1 files changed, 282 insertions, 0 deletions
diff --git a/cpukit/libblock/include/rtems/bdbuf.h b/cpukit/libblock/include/rtems/bdbuf.h new file mode 100644 index 0000000000..270b69598b --- /dev/null +++ b/cpukit/libblock/include/rtems/bdbuf.h @@ -0,0 +1,282 @@ +/* bdbuf.h -- block device buffer management + * + * Copyright (C) 2001 OKTET Ltd., St.-Petersburg, Russia + * Author: Victor V. Vengerov <vvv@oktet.ru> + * + * @(#) $Id$ + */ + +#ifndef __RTEMS_LIBBLOCK_BDBUF_H__ +#define __RTEMS_LIBBLOCK_BDBUF_H__ + +#ifdef __cplusplus +extern "C" { +#endif + +#include <rtems.h> +#include <rtems/libio.h> +#include <chain.h> + +#include "rtems/blkdev.h" +#include "rtems/diskdevs.h" + + +/* + * To manage buffers we using Buffer Descriptors. + * To speed-up buffer lookup descriptors are organized in AVL-Tree. + * The fields 'dev' and 'block' are search key. + */ + +/* Buffer descriptors + * Descriptors organized in AVL-tree to speedup buffer lookup. + * dev and block fields are search key in AVL-tree. + * Modified buffers, free buffers and used buffers linked in 'mod', 'free' and + * 'lru' chains appropriately. + */ + +typedef struct bdbuf_buffer { + Chain_Node link; /* Link in the lru, mod or free chains */ + +#ifdef BINARY_TREE + struct bdbuf_avl_node { + struct bdbuf_buffer *left; /* link to the left sub-tree */ + struct bdbuf_buffer *right; /* link to the right sub-tree */ + + int bf; /* AVL tree node balance factor */ + } avl; /* AVL-tree links */ +#else /* AVL TREE */ + struct bdbuf_avl_node { + char cache; /* Cache */ + + struct bdbuf_buffer* link[2]; /* Left and Right Kids */ + + char bal; /* The balance of the sub-tree */ + } avl; +#endif + dev_t dev; /* device number */ + blkdev_bnum block; /* block number on the device */ + + char *buffer; /* Pointer to the buffer memory area */ + rtems_status_code status; /* Last I/O operation completion status */ + int error; /* If status != RTEMS_SUCCESSFUL, this field contains + errno value which can be used by user later */ + boolean modified:1; /* =1 if buffer was modified */ + boolean in_progress:1; /* =1 if exchange with disk is in progress; + need to wait on semaphore */ + boolean actual:1; /* Buffer contains actual data */ + int use_count; /* Usage counter; incremented when somebody use + this buffer; decremented when buffer released + without modification or when buffer is flushed + by swapout task */ + + rtems_bdpool_id pool; /* Identifier of buffer pool to which this buffer + belongs */ + CORE_mutex_Control transfer_sema; + /* Transfer operation semaphore */ +} bdbuf_buffer; + + + +/* bdbuf_config structure describes block configuration (size, + * amount, memory location) for buffering layer + */ +typedef struct rtems_bdbuf_config { + int size; /* Size of block */ + int num; /* Number of blocks of appropriate size */ + char *mem_area; /* Pointer to the blocks location or NULL, in this + case memory for blocks will be allocated by + Buffering Layer with the help of RTEMS partition + manager */ +} rtems_bdbuf_config; + +extern rtems_bdbuf_config rtems_bdbuf_configuration[]; +extern int rtems_bdbuf_configuration_size; + +/* rtems_bdbuf_init -- + * Prepare buffering layer to work - initialize buffer descritors + * and (if it is neccessary) buffers. Buffers will be allocated accoriding + * to the configuration table, each entry describes kind of block and + * amount requested. After initialization all blocks is placed into + * free elements lists. + * + * PARAMETERS: + * conf_table - pointer to the buffers configuration table + * size - number of entries in configuration table + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + */ +rtems_status_code +rtems_bdbuf_init(rtems_bdbuf_config *conf_table, int size); + + +/* rtems_bdbuf_get -- + * Obtain block buffer. If specified block already cached (i.e. there's + * block in the _modified_, or _recently_used_), return address + * of appropriate buffer descriptor and increment reference counter to 1. + * If block is not cached, allocate new buffer and return it. Data + * shouldn't be read to the buffer from media; buffer may contains + * arbitrary data. This primitive may be blocked if there are no free + * buffer descriptors available and there are no unused non-modified + * (or synchronized with media) buffers available. + * + * PARAMETERS: + * device - device number (constructed of major and minor device number) + * block - linear media block number + * bd - address of variable to store pointer to the buffer descriptor + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + * + * SIDE EFFECTS: + * bufget_sema semaphore obtained by this primitive. + */ +rtems_status_code +rtems_bdbuf_get(dev_t device, blkdev_bnum block, bdbuf_buffer **bdb_ptr); + +/* rtems_bdbuf_read -- + * (Similar to the rtems_bdbuf_get, except reading data from media) + * Obtain block buffer. If specified block already cached, return address + * of appropriate buffer and increment reference counter to 1. If block is + * not cached, allocate new buffer and read data to it from the media. + * This primitive may be blocked on waiting until data to be read from + * media, if there are no free buffer descriptors available and there are + * no unused non-modified (or synchronized with media) buffers available. + * + * PARAMETERS: + * device - device number (consists of major and minor device number) + * block - linear media block number + * bd - address of variable to store pointer to the buffer descriptor + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + * + * SIDE EFFECTS: + * bufget_sema and transfer_sema semaphores obtained by this primitive. + */ +rtems_status_code +rtems_bdbuf_read(dev_t device, blkdev_bnum block, bdbuf_buffer **bdb_ptr); + +/* rtems_bdbuf_release -- + * Release buffer allocated before. This primitive decrease the + * usage counter. If it is zero, further destiny of buffer depends on + * 'modified' status. If buffer was modified, it is placed to the end of + * mod list and flush task waken up. If buffer was not modified, + * it is placed to the end of lru list, and bufget_sema released, allowing + * to reuse this buffer. + * + * PARAMETERS: + * bd_buf - pointer to the bdbuf_buffer structure previously obtained using + * get/read primitive. + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + * + * SIDE EFFECTS: + * flush_sema and bufget_sema semaphores may be released by this primitive. + */ +rtems_status_code +rtems_bdbuf_release(bdbuf_buffer *bd_buf); + +/* rtems_bdbuf_release_modified -- + * Release buffer allocated before, assuming that it is _modified_ by + * it's owner. This primitive decrease usage counter for buffer, mark + * buffer descriptor as modified. If usage counter is 0, insert it at + * end of mod chain and release flush_sema semaphore to activate the + * flush task. + * + * PARAMETERS: + * bd_buf - pointer to the bdbuf_buffer structure previously obtained using + * get/read primitive. + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + * + * SIDE EFFECTS: + * flush_sema semaphore may be released by this primitive. + */ +rtems_status_code +rtems_bdbuf_release_modified(bdbuf_buffer *bd_buf); + +/* rtems_bdbuf_sync -- + * Wait until specified buffer synchronized with disk. Invoked on exchanges + * critical for data consistency on the media. This primitive mark owned + * block as modified, decrease usage counter. If usage counter is 0, + * block inserted to the mod chain and flush_sema semaphore released. + * Finally, primitives blocked on transfer_sema semaphore. + * + * PARAMETERS: + * bd_buf - pointer to the bdbuf_buffer structure previously obtained using + * get/read primitive. + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + * + * SIDE EFFECTS: + * Primitive may be blocked on transfer_sema semaphore. + */ +rtems_status_code +rtems_bdbuf_sync(bdbuf_buffer *bd_buf); + +/* rtems_bdbuf_syncdev -- + * Synchronize with disk all buffers containing the blocks belonging to + * specified device. + * + * PARAMETERS: + * dev - block device number + * + * RETURNS: + * RTEMS status code (RTEMS_SUCCESSFUL if operation completed successfully + * or error code if error is occured) + */ +rtems_status_code +rtems_bdbuf_syncdev(dev_t dev); + +/* rtems_bdbuf_find_pool -- + * Find first appropriate buffer pool. This primitive returns the index + * of first buffer pool which block size is greater than or equal to + * specified size. + * + * PARAMETERS: + * block_size - requested block size + * pool - placeholder for result + * + * RETURNS: + * RTEMS status code: RTEMS_SUCCESSFUL if operation completed successfully, + * RTEMS_INVALID_SIZE if specified block size is invalid (not a power + * of 2), RTEMS_NOT_DEFINED if buffer pool for this or greater block size + * is not configured. + */ +rtems_status_code +rtems_bdbuf_find_pool(int block_size, rtems_bdpool_id *pool); + +/* rtems_bdbuf_get_pool_info -- + * Obtain characteristics of buffer pool with specified number. + * + * PARAMETERS: + * pool - buffer pool number + * block_size - block size for which buffer pool is configured returned + * there + * blocks - number of buffers in buffer pool returned there + * + * RETURNS: + * RTEMS status code: RTEMS_SUCCESSFUL if operation completed successfully, + * RTEMS_INVALID_NUMBER if appropriate buffer pool is not configured. + * + * NOTE: + * Buffer pools enumerated contiguously starting from 0. + */ +rtems_status_code +rtems_bdbuf_get_pool_info(rtems_bdpool_id pool, int *block_size, int *blocks); + +#ifdef __cplusplus +} +#endif + +#endif |