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diff --git a/include/rtems/bdbuf.h b/include/rtems/bdbuf.h new file mode 100644 index 0000000000..edec05e099 --- /dev/null +++ b/include/rtems/bdbuf.h @@ -0,0 +1,699 @@ +/** + * @file + * + * @ingroup rtems_bdbuf + * @brief Block Device Buffer Management + */ + +/* + * Copyright (C) 2001 OKTET Ltd., St.-Petersburg, Russia + * Author: Victor V. Vengerov <vvv@oktet.ru> + * + * Copyright (C) 2008,2009 Chris Johns <chrisj@rtems.org> + * Rewritten to remove score mutex access. Fixes many performance + * issues. + * Change to support demand driven variable buffer sizes. + * + * Copyright (c) 2009-2012 embedded brains GmbH. + */ + +#ifndef _RTEMS_BDBUF_H +#define _RTEMS_BDBUF_H + +#include <rtems.h> +#include <rtems/libio.h> +#include <rtems/chain.h> + +#include <rtems/blkdev.h> +#include <rtems/diskdevs.h> + +#ifdef __cplusplus +extern "C" { +#endif + +/** + * @defgroup rtems_libblock Block Device Library + * + * Block device modules. + */ + +/** + * @defgroup rtems_bdbuf Block Device Buffer Management + * + * @ingroup rtems_libblock + * + * The Block Device Buffer Management implements a cache between the disk + * devices and file systems. The code provides read-ahead and write queuing to + * the drivers and fast cache look-up using an AVL tree. + * + * The block size used by a file system can be set at runtime and must be a + * multiple of the disk device block size. The disk device's physical block + * size is called the media block size. The file system can set the block size + * it uses to a larger multiple of the media block size. The driver must be + * able to handle buffers sizes larger than one media block. + * + * The user configures the amount of memory to be used as buffers in the cache, + * and the minimum and maximum buffer size. The cache will allocate additional + * memory for the buffer descriptors and groups. There are enough buffer + * descriptors allocated so all the buffer memory can be used as minimum sized + * buffers. + * + * The cache is a single pool of buffers. The buffer memory is divided into + * groups where the size of buffer memory allocated to a group is the maximum + * buffer size. A group's memory can be divided down into small buffer sizes + * that are a multiple of 2 of the minimum buffer size. A group is the minimum + * allocation unit for buffers of a specific size. If a buffer of maximum size + * is request the group will have a single buffer. If a buffer of minimum size + * is requested the group is divided into minimum sized buffers and the + * remaining buffers are held ready for use. A group keeps track of which + * buffers are with a file system or driver and groups who have buffer in use + * cannot be realloced. Groups with no buffers in use can be taken and + * realloced to a new size. This is how buffers of different sizes move around + * the cache. + + * The buffers are held in various lists in the cache. All buffers follow this + * state machine: + * + * @dot + * digraph state { + * size="16,8"; + * f [label="FREE",style="filled",fillcolor="aquamarine"]; + * e [label="EMPTY",style="filled",fillcolor="seagreen"]; + * c [label="CACHED",style="filled",fillcolor="chartreuse"]; + * ac [label="ACCESS CACHED",style="filled",fillcolor="royalblue"]; + * am [label="ACCESS MODIFIED",style="filled",fillcolor="royalblue"]; + * ae [label="ACCESS EMPTY",style="filled",fillcolor="royalblue"]; + * ap [label="ACCESS PURGED",style="filled",fillcolor="royalblue"]; + * t [label="TRANSFER",style="filled",fillcolor="red"]; + * tp [label="TRANSFER PURGED",style="filled",fillcolor="red"]; + * s [label="SYNC",style="filled",fillcolor="red"]; + * m [label="MODIFIED",style="filled",fillcolor="gold"]; + * i [label="INITIAL"]; + * + * legend_transfer [label="Transfer Wake-Up",fontcolor="red",shape="none"]; + * legend_access [label="Access Wake-Up",fontcolor="royalblue",shape="none"]; + * + * i -> f [label="Init"]; + * f -> e [label="Buffer Recycle"]; + * e -> ae [label="Get"]; + * e -> t [label="Read"]; + * e -> f [label="Nobody Waits"]; + * c -> ac [label="Get\nRead"]; + * c -> e [label="Buffer Recycle\nPurge"]; + * c -> f [label="Reallocate\nBlock Size Changed"]; + * t -> c [label="Transfer Done",color="red",fontcolor="red"]; + * t -> e [label="Transfer Error",color="red",fontcolor="red"]; + * t -> tp [label="Purge"]; + * tp -> e [label="Transfer Done\nTransfer Error",color="red",fontcolor="red"]; + * m -> t [label="Swapout"]; + * m -> s [label="Block Size Changed"]; + * m -> am [label="Get\nRead"]; + * m -> e [label="Purge"]; + * ac -> m [label="Release Modified",color="royalblue",fontcolor="royalblue"]; + * ac -> s [label="Sync",color="royalblue",fontcolor="royalblue"]; + * ac -> c [label="Release",color="royalblue",fontcolor="royalblue"]; + * ac -> ap [label="Purge"]; + * am -> m [label="Release\nRelease Modified",color="royalblue",fontcolor="royalblue"]; + * am -> s [label="Sync",color="royalblue",fontcolor="royalblue"]; + * am -> ap [label="Purge"]; + * ae -> m [label="Release Modified",color="royalblue",fontcolor="royalblue"]; + * ae -> s [label="Sync",color="royalblue",fontcolor="royalblue"]; + * ae -> e [label="Release",color="royalblue",fontcolor="royalblue"]; + * ae -> ap [label="Purge"]; + * ap -> e [label="Release\nRelease Modified\nSync",color="royalblue",fontcolor="royalblue"]; + * s -> t [label="Swapout"]; + * s -> e [label="Purge",color="red",fontcolor="red"]; + * } + * @enddot + * + * Empty or cached buffers are added to the LRU list and removed from this + * queue when a caller requests a buffer. This is referred to as getting a + * buffer in the code and the event get in the state diagram. The buffer is + * assigned to a block and inserted to the AVL based on the block/device key. + * If the block is to be read by the user and not in the cache it is transfered + * from the disk into memory. If no buffers are on the LRU list the modified + * list is checked. If buffers are on the modified the swap out task will be + * woken. The request blocks until a buffer is available for recycle. + * + * A block being accessed is given to the file system layer and not accessible + * to another requester until released back to the cache. The same goes to a + * buffer in the transfer state. The transfer state means being read or + * written. If the file system has modified the block and releases it as + * modified it placed on the cache's modified list and a hold timer + * initialised. The buffer is held for the hold time before being written to + * disk. Buffers are held for a configurable period of time on the modified + * list as a write sets the state to transfer and this locks the buffer out + * from the file system until the write completes. Buffers are often accessed + * and modified in a series of small updates so if sent to the disk when + * released as modified the user would have to block waiting until it had been + * written. This would be a performance problem. + * + * The code performs multiple block reads and writes. Multiple block reads or + * read-ahead increases performance with hardware that supports it. It also + * helps with a large cache as the disk head movement is reduced. It however + * is a speculative operation so excessive use can remove valuable and needed + * blocks from the cache. The read-ahead is triggered after two misses of + * ascending consecutive blocks or a read hit of a block read by the + * most-resent read-ahead transfer. The read-ahead works per disk, but all + * transfers are issued by the read-ahead task. + * + * The cache has the following lists of buffers: + * - LRU: Accessed or transfered buffers released in least recently used + * order. Empty buffers will be placed to the front. + * - Modified: Buffers waiting to be written to disk. + * - Sync: Buffers to be synchronized with the disk. + * + * A cache look-up will be performed to find a suitable buffer. A suitable + * buffer is one that matches the same allocation size as the device the buffer + * is for. The a buffer's group has no buffers in use with the file system or + * driver the group is reallocated. This means the buffers in the group are + * invalidated, resized and placed on the LRU queue. There is a performance + * issue with this design. The reallocation of a group may forced recently + * accessed buffers out of the cache when they should not. The design should be + * change to have groups on a LRU list if they have no buffers in use. + */ +/**@{**/ + +#if defined(RTEMS_POSIX_API) + /* + * Use the PTHREAD mutexes and condition variables if available. This helps + * on SMP configurations to avoid the home grown condition variables via + * disabled preemption. + */ + #define RTEMS_BDBUF_USE_PTHREAD +#endif + +/** + * @brief State of a buffer of the cache. + * + * The state has several implications. Depending on the state a buffer can be + * in the AVL tree, in a list, in use by an entity and a group user or not. + * + * <table> + * <tr> + * <th>State</th><th>Valid Data</th><th>AVL Tree</th> + * <th>LRU List</th><th>Modified List</th><th>Synchronization List</th> + * <th>Group User</th><th>External User</th> + * </tr> + * <tr> + * <td>FREE</td><td></td><td></td> + * <td>X</td><td></td><td></td><td></td><td></td> + * </tr> + * <tr> + * <td>EMPTY</td><td></td><td>X</td> + * <td></td><td></td><td></td><td></td><td></td> + * </tr> + * <tr> + * <td>CACHED</td><td>X</td><td>X</td> + * <td>X</td><td></td><td></td><td></td><td></td> + * </tr> + * <tr> + * <td>ACCESS CACHED</td><td>X</td><td>X</td> + * <td></td><td></td><td></td><td>X</td><td>X</td> + * </tr> + * <tr> + * <td>ACCESS MODIFIED</td><td>X</td><td>X</td> + * <td></td><td></td><td></td><td>X</td><td>X</td> + * </tr> + * <tr> + * <td>ACCESS EMPTY</td><td></td><td>X</td> + * <td></td><td></td><td></td><td>X</td><td>X</td> + * </tr> + * <tr> + * <td>ACCESS PURGED</td><td></td><td>X</td> + * <td></td><td></td><td></td><td>X</td><td>X</td> + * </tr> + * <tr> + * <td>MODIFIED</td><td>X</td><td>X</td> + * <td></td><td>X</td><td></td><td>X</td><td></td> + * </tr> + * <tr> + * <td>SYNC</td><td>X</td><td>X</td> + * <td></td><td></td><td>X</td><td>X</td><td></td> + * </tr> + * <tr> + * <td>TRANSFER</td><td>X</td><td>X</td> + * <td></td><td></td><td></td><td>X</td><td>X</td> + * </tr> + * <tr> + * <td>TRANSFER PURGED</td><td></td><td>X</td> + * <td></td><td></td><td></td><td>X</td><td>X</td> + * </tr> + * </table> + */ +typedef enum +{ + /** + * @brief Free. + */ + RTEMS_BDBUF_STATE_FREE = 0, + + /** + * @brief Empty. + */ + RTEMS_BDBUF_STATE_EMPTY, + + /** + * @brief Cached. + */ + RTEMS_BDBUF_STATE_CACHED, + + /** + * @brief Accessed by upper layer with cached data. + */ + RTEMS_BDBUF_STATE_ACCESS_CACHED, + + /** + * @brief Accessed by upper layer with modified data. + */ + RTEMS_BDBUF_STATE_ACCESS_MODIFIED, + + /** + * @brief Accessed by upper layer with invalid data. + */ + RTEMS_BDBUF_STATE_ACCESS_EMPTY, + + /** + * @brief Accessed by upper layer with purged data. + */ + RTEMS_BDBUF_STATE_ACCESS_PURGED, + + /** + * @brief Modified by upper layer. + */ + RTEMS_BDBUF_STATE_MODIFIED, + + /** + * @brief Scheduled for synchronization. + */ + RTEMS_BDBUF_STATE_SYNC, + + /** + * @brief In transfer by block device driver. + */ + RTEMS_BDBUF_STATE_TRANSFER, + + /** + * @brief In transfer by block device driver and purged. + */ + RTEMS_BDBUF_STATE_TRANSFER_PURGED +} rtems_bdbuf_buf_state; + +/** + * Forward reference to the block. + */ +struct rtems_bdbuf_group; +typedef struct rtems_bdbuf_group rtems_bdbuf_group; + +/** + * To manage buffers we using buffer descriptors (BD). A BD holds a buffer plus + * a range of other information related to managing the buffer in the cache. To + * speed-up buffer lookup descriptors are organized in AVL-Tree. The fields + * 'dd' and 'block' are search keys. + */ +typedef struct rtems_bdbuf_buffer +{ + rtems_chain_node link; /**< Link the BD onto a number of lists. */ + + struct rtems_bdbuf_avl_node + { + struct rtems_bdbuf_buffer* left; /**< Left Child */ + struct rtems_bdbuf_buffer* right; /**< Right Child */ + signed char cache; /**< Cache */ + signed char bal; /**< The balance of the sub-tree */ + } avl; + + rtems_disk_device *dd; /**< disk device */ + + rtems_blkdev_bnum block; /**< block number on the device */ + + unsigned char* buffer; /**< Pointer to the buffer memory area */ + + rtems_bdbuf_buf_state state; /**< State of the buffer. */ + + uint32_t waiters; /**< The number of threads waiting on this + * buffer. */ + rtems_bdbuf_group* group; /**< Pointer to the group of BDs this BD is + * part of. */ + uint32_t hold_timer; /**< Timer to indicate how long a buffer + * has been held in the cache modified. */ + + int references; /**< Allow reference counting by owner. */ + void* user; /**< User data. */ +} rtems_bdbuf_buffer; + +/** + * A group is a continuous block of buffer descriptors. A group covers the + * maximum configured buffer size and is the allocation size for the buffers to + * a specific buffer size. If you allocate a buffer to be a specific size, all + * buffers in the group, if there are more than 1 will also be that size. The + * number of buffers in a group is a multiple of 2, ie 1, 2, 4, 8, etc. + */ +struct rtems_bdbuf_group +{ + rtems_chain_node link; /**< Link the groups on a LRU list if they + * have no buffers in use. */ + size_t bds_per_group; /**< The number of BD allocated to this + * group. This value must be a multiple of + * 2. */ + uint32_t users; /**< How many users the block has. */ + rtems_bdbuf_buffer* bdbuf; /**< First BD this block covers. */ +}; + +/** + * Buffering configuration definition. See confdefs.h for support on using this + * structure. + */ +typedef struct rtems_bdbuf_config { + uint32_t max_read_ahead_blocks; /**< Number of blocks to read + * ahead. */ + uint32_t max_write_blocks; /**< Number of blocks to write + * at once. */ + rtems_task_priority swapout_priority; /**< Priority of the swap out + * task. */ + uint32_t swapout_period; /**< Period swap-out checks buf + * timers. */ + uint32_t swap_block_hold; /**< Period a buffer is held. */ + size_t swapout_workers; /**< The number of worker + * threads for the swap-out + * task. */ + rtems_task_priority swapout_worker_priority; /**< Priority of the swap out + * task. */ + size_t task_stack_size; /**< Task stack size for swap-out + * task and worker threads. */ + size_t size; /**< Size of memory in the + * cache */ + uint32_t buffer_min; /**< Minimum buffer size. */ + uint32_t buffer_max; /**< Maximum buffer size + * supported. It is also the + * allocation size. */ + rtems_task_priority read_ahead_priority; /**< Priority of the read-ahead + * task. */ +} rtems_bdbuf_config; + +/** + * External reference to the configuration. + * + * The configuration is provided by the application. + */ +extern const rtems_bdbuf_config rtems_bdbuf_configuration; + +/** + * The default value for the maximum read-ahead blocks disables the read-ahead + * feature. + */ +#define RTEMS_BDBUF_MAX_READ_AHEAD_BLOCKS_DEFAULT 0 + +/** + * Default maximum number of blocks to write at once. + */ +#define RTEMS_BDBUF_MAX_WRITE_BLOCKS_DEFAULT 16 + +/** + * Default swap-out task priority. + */ +#define RTEMS_BDBUF_SWAPOUT_TASK_PRIORITY_DEFAULT 15 + +/** + * Default swap-out task swap period in milli seconds. + */ +#define RTEMS_BDBUF_SWAPOUT_TASK_SWAP_PERIOD_DEFAULT 250 + +/** + * Default swap-out task block hold time in milli seconds. + */ +#define RTEMS_BDBUF_SWAPOUT_TASK_BLOCK_HOLD_DEFAULT 1000 + +/** + * Default swap-out worker tasks. Currently disabled. + */ +#define RTEMS_BDBUF_SWAPOUT_WORKER_TASKS_DEFAULT 0 + +/** + * Default swap-out worker task priority. The same as the swap-out task. + */ +#define RTEMS_BDBUF_SWAPOUT_WORKER_TASK_PRIORITY_DEFAULT \ + RTEMS_BDBUF_SWAPOUT_TASK_PRIORITY_DEFAULT + +/** + * Default read-ahead task priority. The same as the swap-out task. + */ +#define RTEMS_BDBUF_READ_AHEAD_TASK_PRIORITY_DEFAULT \ + RTEMS_BDBUF_SWAPOUT_TASK_PRIORITY_DEFAULT + +/** + * Default task stack size for swap-out and worker tasks. + */ +#define RTEMS_BDBUF_TASK_STACK_SIZE_DEFAULT RTEMS_MINIMUM_STACK_SIZE + +/** + * Default size of memory allocated to the cache. + */ +#define RTEMS_BDBUF_CACHE_MEMORY_SIZE_DEFAULT (64 * 512) + +/** + * Default minimum size of buffers. + */ +#define RTEMS_BDBUF_BUFFER_MIN_SIZE_DEFAULT (512) + +/** + * Default maximum size of buffers. + */ +#define RTEMS_BDBUF_BUFFER_MAX_SIZE_DEFAULT (4096) + +/** + * Prepare buffering layer to work - initialize buffer descritors and (if it is + * neccessary) buffers. After initialization all blocks is placed into the + * ready state. + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_CALLED_FROM_ISR Called from an interrupt context. + * @retval RTEMS_INVALID_NUMBER The buffer maximum is not an integral multiple + * of the buffer minimum. The maximum read-ahead blocks count is too large. + * @retval RTEMS_RESOURCE_IN_USE Already initialized. + * @retval RTEMS_UNSATISFIED Not enough resources. + */ +rtems_status_code +rtems_bdbuf_init (void); + +/** + * Get block buffer for data to be written into. The buffers is set to the + * access or modified access state. If the buffer is in the cache and modified + * the state is access modified else the state is access. This buffer contents + * are not initialised if the buffer is not already in the cache. If the block + * is already resident in memory it is returned how-ever if not in memory the + * buffer is not read from disk. This call is used when writing the whole block + * on a disk rather than just changing a part of it. If there is no buffers + * available this call will block. A buffer obtained with this call will not be + * involved in a transfer request and will not be returned to another user + * until released. If the buffer is already with a user when this call is made + * the call is blocked until the buffer is returned. The highest priority + * waiter will obtain the buffer first. + * + * The block number is the linear block number. This is relative to the start + * of the partition on the media. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param dd [in] The disk device. + * @param block [in] Linear media block number. + * @param bd [out] Reference to the buffer descriptor pointer. + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_INVALID_ID Invalid block number. + */ +rtems_status_code +rtems_bdbuf_get ( + rtems_disk_device *dd, + rtems_blkdev_bnum block, + rtems_bdbuf_buffer** bd +); + +/** + * Get the block buffer and if not already in the cache read from the disk. If + * specified block already cached return. The buffer is set to the access or + * modified access state. If the buffer is in the cache and modified the state + * is access modified else the state is access. If block is already being read + * from disk for being written to disk this call blocks. If the buffer is + * waiting to be written it is removed from modified queue and returned to the + * user. If the buffer is not in the cache a new buffer is obtained and the + * data read from disk. The call may block until these operations complete. A + * buffer obtained with this call will not be involved in a transfer request + * and will not be returned to another user until released. If the buffer is + * already with a user when this call is made the call is blocked until the + * buffer is returned. The highest priority waiter will obtain the buffer + * first. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param dd [in] The disk device. + * @param block [in] Linear media block number. + * @param bd [out] Reference to the buffer descriptor pointer. + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_INVALID_ID Invalid block number. + * @retval RTEMS_IO_ERROR IO error. + */ +rtems_status_code +rtems_bdbuf_read ( + rtems_disk_device *dd, + rtems_blkdev_bnum block, + rtems_bdbuf_buffer** bd +); + +/** + * Release the buffer obtained by a read call back to the cache. If the buffer + * was obtained by a get call and was not already in the cache the release + * modified call should be used. A buffer released with this call obtained by a + * get call may not be in sync with the contents on disk. If the buffer was in + * the cache and modified before this call it will be returned to the modified + * queue. The buffers is returned to the end of the LRU list. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param bd [in] Reference to the buffer descriptor. The buffer descriptor + * reference must not be @c NULL and must be obtained via rtems_bdbuf_get() or + * rtems_bdbuf_read(). + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_INVALID_ADDRESS The reference is NULL. + */ +rtems_status_code +rtems_bdbuf_release (rtems_bdbuf_buffer* bd); + +/** + * Release the buffer allocated with a get or read call placing it on the + * modified list. If the buffer was not released modified before the hold + * timer is set to the configuration value. If the buffer had been released + * modified before but not written to disk the hold timer is not updated. The + * buffer will be written to disk when the hold timer has expired, there are + * not more buffers available in the cache and a get or read buffer needs one + * or a sync call has been made. If the buffer is obtained with a get or read + * before the hold timer has expired the buffer will be returned to the user. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param bd [in] Reference to the buffer descriptor. The buffer descriptor + * reference must not be @c NULL and must be obtained via rtems_bdbuf_get() or + * rtems_bdbuf_read(). + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_INVALID_ADDRESS The reference is NULL. + */ +rtems_status_code +rtems_bdbuf_release_modified (rtems_bdbuf_buffer* bd); + +/** + * Release the buffer as modified and wait until it has been synchronized with + * the disk by writing it. This buffer will be the first to be transfer to disk + * and other buffers may also be written if the maximum number of blocks in a + * requests allows it. + * + * @note This code does not lock the sync mutex and stop additions to the + * modified queue. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param bd [in] Reference to the buffer descriptor. The buffer descriptor + * reference must not be @c NULL and must be obtained via rtems_bdbuf_get() or + * rtems_bdbuf_read(). + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_INVALID_ADDRESS The reference is NULL. + */ +rtems_status_code +rtems_bdbuf_sync (rtems_bdbuf_buffer* bd); + +/** + * Synchronize all modified buffers for this device with the disk and wait + * until the transfers have completed. The sync mutex for the cache is locked + * stopping the addition of any further modified buffers. It is only the + * currently modified buffers that are written. + * + * @note Nesting calls to sync multiple devices will be handled sequentially. A + * nested call will be blocked until the first sync request has complete. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param dd [in] The disk device. + * + * @retval RTEMS_SUCCESSFUL Successful operation. + */ +rtems_status_code +rtems_bdbuf_syncdev (rtems_disk_device *dd); + +/** + * @brief Purges all buffers corresponding to the disk device @a dd. + * + * This may result in loss of data. The read-ahead state of this device is reset. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param dd [in] The disk device. + */ +void +rtems_bdbuf_purge_dev (rtems_disk_device *dd); + +/** + * @brief Sets the block size of a disk device. + * + * This will set the block size derived fields of the disk device. If + * requested the disk device is synchronized before the block size change + * occurs. Since the cache is unlocked during the synchronization operation + * some tasks may access the disk device in the meantime. This may result in + * loss of data. After the synchronization the disk device is purged to ensure + * a consistent cache state and the block size change occurs. This also resets + * the read-ahead state of this disk device. Due to the purge operation this + * may result in loss of data. + * + * Before you can use this function, the rtems_bdbuf_init() routine must be + * called at least once to initialize the cache, otherwise a fatal error will + * occur. + * + * @param dd [in, out] The disk device. + * @param block_size [in] The new block size in bytes. + * @param sync [in] If @c true, then synchronize the disk device before the + * block size change. + * + * @retval RTEMS_SUCCESSFUL Successful operation. + * @retval RTEMS_INVALID_NUMBER Invalid block size. + */ +rtems_status_code +rtems_bdbuf_set_block_size (rtems_disk_device *dd, + uint32_t block_size, + bool sync); + +/** + * @brief Returns the block device statistics. + */ +void +rtems_bdbuf_get_device_stats (const rtems_disk_device *dd, + rtems_blkdev_stats *stats); + +/** + * @brief Resets the block device statistics. + */ +void +rtems_bdbuf_reset_device_stats (rtems_disk_device *dd); + +/** @} */ + +#ifdef __cplusplus +} +#endif + +#endif |