bdbuf.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

    *bd = bd_buf;
           
    return RTEMS_SUCCESSFUL;
}


/* bdbuf_release --
 *     Release buffer. Decrease buffer usage counter. If it is zero, further
 *     processing depends on modified attribute. If buffer was modified, it
 *     is inserted into mod chain and swapout task waken up. If buffer was
 *     not modified, it is returned to the end of lru chain making it available
 *     for further use.
 *
 * PARAMETERS:
 *     bd_buf - pointer to the released buffer descriptor.
 *
 * RETURNS:
 *     RTEMS_SUCCESSFUL if buffer released successfully, or error code if
 *     error occured.
 *
 * NOTE:
 *     This is internal function. It is assumed that task made non-preemptive
 *     before its invocation.
 */
static rtems_status_code
bdbuf_release(bdbuf_buffer *bd_buf)
{
    bdbuf_pool *bd_pool;
    rtems_status_code rc = RTEMS_SUCCESSFUL;

    if (bd_buf->use_count <= 0)
        return RTEMS_INTERNAL_ERROR;
    
    bd_pool = bd_ctx.pool + bd_buf->pool;

    bd_buf->use_count--;

    if (bd_buf->use_count == 0)
    {
        if (bd_buf->modified)
        {
            
            /* Buffer was modified. Insert buffer to the modified buffers
             * list and initiate flushing. */
            Chain_Append(&bd_ctx.mod, &bd_buf->link);

            /* Release the flush_sema */
            rc = rtems_semaphore_release(bd_ctx.flush_sema);
        }
        else
        {
            /* Buffer was not modified. Add this descriptor to the 
             * end of lru chain and make it available for reuse. */
            Chain_Append(&bd_pool->lru, &bd_buf->link);
            rc = rtems_semaphore_release(bd_pool->bufget_sema);
        }
    }
    return rc;
}


/* 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)
{
    preemption_key key;
    rtems_status_code rc = RTEMS_SUCCESSFUL;

    if (bd_buf == NULL)
        return RTEMS_INVALID_ADDRESS;
    
    DISABLE_PREEMPTION(key);
    
    rc = bdbuf_release(bd_buf);
    
    ENABLE_PREEMPTION(key);
    
    return rc;
}

/* 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)
{
    preemption_key key;
    rtems_status_code rc = RTEMS_SUCCESSFUL;

    if (bd_buf == NULL)
        return RTEMS_INVALID_ADDRESS;
    
    DISABLE_PREEMPTION(key);

    if (!bd_buf->modified)
    {
        bdbuf_initialize_transfer_sema(bd_buf);
    }
    bd_buf->modified = TRUE;
    bd_buf->actual = TRUE;
    rc = bdbuf_release(bd_buf);    
    
    ENABLE_PREEMPTION(key);
    
    return rc;
}

/* 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)
{
    preemption_key key;
    ISR_Level level;
    rtems_status_code rc = RTEMS_SUCCESSFUL;

    if (bd_buf == NULL)
        return RTEMS_INVALID_ADDRESS;
    
    DISABLE_PREEMPTION(key);

    if (!bd_buf->modified)
    {
        bdbuf_initialize_transfer_sema(bd_buf);
    }
    bd_buf->modified = TRUE;
    bd_buf->actual = TRUE;

    rc = bdbuf_release(bd_buf);

    if (rc == RTEMS_SUCCESSFUL)
    {
        rtems_interrupt_disable(level);
        _CORE_mutex_Seize(&bd_buf->transfer_sema, 0, TRUE,
                          WATCHDOG_NO_TIMEOUT, level);
    }
    
    ENABLE_PREEMPTION(key);
    
    return rc;
}

/* 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)
{
    preemption_key key;
    ISR_Level level;
            
    bdbuf_buffer *bd_buf;
    disk_device *dd;
    bdbuf_pool  *pool;
    
    dd = rtems_disk_lookup(dev);
    if (dd == NULL)
        return RTEMS_INVALID_ID;
    
    pool = bd_ctx.pool + dd->pool;
        
    DISABLE_PREEMPTION(key);
    do {
        bd_buf = avl_search_for_sync(&pool->tree, dd);
        if (bd_buf != NULL /* && bd_buf->modified */)
        {
            rtems_interrupt_disable(level);
            _CORE_mutex_Seize(&bd_buf->transfer_sema, 0, TRUE,
                              WATCHDOG_NO_TIMEOUT, level);
        }
    } while (bd_buf != NULL);
    ENABLE_PREEMPTION(key);
    return rtems_disk_release(dd);
}

/* bdbuf_swapout_task --
 *     Body of task which take care on flushing modified buffers to the
 *     disk.
 */
static rtems_task 
bdbuf_swapout_task(rtems_task_argument unused)
{
    rtems_status_code rc;
    int result;
    ISR_Level level;
    bdbuf_buffer *bd_buf;
    bdbuf_pool *bd_pool;
    disk_device *dd;
    blkdev_request1 req;

    while (1)
    {
        rc = rtems_semaphore_obtain(bd_ctx.flush_sema, RTEMS_WAIT, 0);
        if (rc != RTEMS_SUCCESSFUL)
        {
            rtems_fatal_error_occurred(BLKDEV_FATAL_BDBUF_SWAPOUT);
        }
            
        bd_buf = (bdbuf_buffer *)Chain_Get(&bd_ctx.mod);
        if (bd_buf == NULL)
        {
            /* It is possible that flush_sema semaphore will be released, but
             * buffer to be removed from mod chain before swapout task start
             * its processing. */
            continue;
        }

        bd_buf->in_progress = TRUE;
        bd_buf->use_count++;
        bd_pool = bd_ctx.pool + bd_buf->pool;
        dd = rtems_disk_lookup(bd_buf->dev);

        req.req.req = BLKDEV_REQ_WRITE;
        req.req.req_done = bdbuf_write_transfer_done;
        req.req.done_arg = bd_buf;
        req.req.start = bd_buf->block + dd->start;
        req.req.count = 1;
        req.req.bufnum = 1;
        req.req.bufs[0].length = dd->block_size;
        req.req.bufs[0].buffer = bd_buf->buffer;

        /* transfer_sema initialized when bd_buf inserted in the mod chain 
           first time */
        result = dd->ioctl(dd->phys_dev->dev, BLKIO_REQUEST, &req);
        
        rtems_disk_release(dd);
        
        if (result == -1)
        {
            bd_buf->status = RTEMS_IO_ERROR;
            bd_buf->error = errno;
            /* Release tasks waiting on syncing this buffer */
            _CORE_mutex_Flush(&bd_buf->transfer_sema, NULL,
                              CORE_MUTEX_STATUS_SUCCESSFUL);
        }
        else
        {
            if (bd_buf->in_progress)
            {
                rtems_interrupt_disable(level);
                _CORE_mutex_Seize(&bd_buf->transfer_sema, 0, TRUE, 0, level);
            }
        }
        bd_buf->use_count--;

        /* Another task have chance to use this buffer, or even
         * modify it. If buffer is not in use, insert it in appropriate chain
         * and release semaphore */
        if (bd_buf->use_count == 0)
        {
            if (bd_buf->modified)
            {
                Chain_Append(&bd_ctx.mod, &bd_buf->link);
                rc = rtems_semaphore_release(bd_ctx.flush_sema);
            }
            else
            {
                Chain_Append(&bd_pool->lru, &bd_buf->link);
                rc = rtems_semaphore_release(bd_pool->bufget_sema);
            }
        }
    }
}

/* 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_bdpool_id i;
    bdbuf_pool *p;
    int cursize = INT_MAX;
    rtems_bdpool_id curid = -1;
    rtems_boolean found = FALSE;
    int j;
    
    for (j = block_size; (j != 0) && ((j & 1) == 0); j >>= 1);
    if (j != 1)
        return RTEMS_INVALID_SIZE;
    
    for (i = 0, p = bd_ctx.pool; i < bd_ctx.npools; i++, p++)
    {
        if ((p->blksize >= block_size) &&
            (p->blksize < cursize))
        {
            curid = i;
            cursize = p->blksize;
            found = TRUE;
        }
    }
    
    if (found)
    {
        if (pool != NULL)
            *pool = curid;
        return RTEMS_SUCCESSFUL;
    }
    else
    {
        return RTEMS_NOT_DEFINED;
    }
}

/* 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)
{
    if (pool >= bd_ctx.npools)
        return RTEMS_INVALID_NUMBER;
    
    if (block_size != NULL)
    {
        *block_size = bd_ctx.pool[pool].blksize;
    }
    
    if (blocks != NULL)
    {
        *blocks = bd_ctx.pool[pool].nblks;
    }
    
    return RTEMS_SUCCESSFUL;
}