/**
* @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
*
* @ingroup RTEMSDeviceDrivers
*
* @brief 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.
*/
/**@{**/
/**
* @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
