id1_buffer.c

小型操作系统,以VC为开发环境,需要boachs调试

			pstBlock = pstTemp;
			if ( !BADNESS(pstTemp) )
				break;
		}
    //repeat until we find something good
	}while ( (pstTemp=pstTemp->pstNextFree) != g_pstFreeList );

	//POSITION();
	if (!pstBlock) {
		//如果所有的缓冲都被使用（引用计数>0），睡眠，等待
		vMtsTaskSleep(&g_pstBufferWaitTask);
		goto lbl_Repeat;
	}

	//POSITION();
	Id1WaitOnBuffer(pstBlock);	//如果上锁则等...
	if (pstBlock->ucRefers)		//如果这时又被其他任务使用，则再重复上述过程。 
		goto lbl_Repeat;

	while (pstBlock->ucDirty) {
		//如果该缓冲区已经修改，则将数据写盘，并再次等待缓冲区解锁。
		iId1SyncDeviceBuffer(pstBlock->uiDevice);
		Id1WaitOnBuffer(pstBlock);
		if (pstBlock->ucRefers)
			goto lbl_Repeat;
	}
	//POSITION();
	/* NOTE!! While we slept waiting for this block, somebody else might */
	/* already have added "this" block to the cache. check it */
	if ( pstId1FindBuffer(iDevice, iBlock) )
		goto lbl_Repeat;
	/* OK, FINALLY we know that this buffer is the only one of it's kind, */
	/* and that it's unused (b_count=0), unlocked (b_lock=0), and clean */
	pstBlock->ucRefers = 1;
	pstBlock->ucDirty = 0;
	pstBlock->ucUpToDate = 0;
	Id1RemoveFromQueue(pstBlock);
	pstBlock->uiDevice = (unsigned short)iDevice;
	pstBlock->ulBlockNr = (unsigned short)iBlock;
	
	//POSITION();
	
	Id1InsertToQueue(pstBlock);

	return pstBlock;
}

/************************************************************
*************************************************************
**      Function Name:			pstId1GetHashTable
**      Author:                 x.cheng
**
**      Comment:
**			Why like this, I hear you say... The reason is race-conditions.
**		As we don't lock buffers (unless we are readint them, that is),
**		something might happen to it while we sleep (ie a read-error
**		will force it bad). This shouldn't really happen currently, but
**		the code is ready.
**
**      List of parameters:
**			iDevice - which device.
**			iBlock - which block.
**
**      Return value:   
**
**      Revisions:
**
*************************************************************
*************************************************************/
ts_BufferBlock* pstId1GetHashTable(int iDevice, int iBlock)
{
	ts_BufferBlock* pstBlock;

	for(;;) {
		if ( !(pstBlock=pstId1FindBuffer(iDevice, iBlock)) )
			return NULL;
		pstBlock->ucRefers ++;
		Id1WaitOnBuffer(pstBlock);

		if (pstBlock->uiDevice == (unsigned short)iDevice && 
			pstBlock->ulBlockNr == (unsigned short)iBlock)
			return pstBlock;

		pstBlock->ucRefers -- ;
	}
}

/************************************************************
*************************************************************
**      Function Name:			iId1SyncDeviceBuffer
**      Author:                 x.cheng
**
**      Comment:
**			对指定的设备进行缓冲和设备上数据的同步。
**
**      List of parameters:
**			iDevice - which device.
**
**      Return value:   
**
**      Revisions:
**
*************************************************************
*************************************************************/
int iId1SyncDeviceBuffer(int iDevice)
{
	int i;
	ts_BufferBlock* pstBlock;

	pstBlock = (ts_BufferBlock *)&KernelEnd_;
	
	for( i=0; i<(int)g_ulNrOfBlocks; i++, pstBlock++ ) {
		if (pstBlock->uiDevice != (unsigned short)iDevice)
			continue;
		Id1WaitOnBuffer(pstBlock);

		if ( pstBlock->uiDevice==(unsigned short)iDevice && pstBlock->ucDirty ) {
			//write to device...
		}
	}

	//write inode...

	return 1;
}


//----------------------------------------------------------------------------------
//==============================local function======================================
//----------------------------------------------------------------------------------

/************************************************************
*************************************************************
**      Function Name:			Id1WaitOnBuffer
**      Author:                 x.cheng
**
**      Comment:
**
**      List of parameters:
**			pucBlock - address.
**
**      Return value:   
**          none 
**
**      Revisions:
**
*************************************************************
*************************************************************/
static void Id1WaitOnBuffer(ts_BufferBlock* pstBlock)
{
//	vCLI();

	while ( pstBlock->ucLocked )
		vMtsTaskSleep( &pstBlock->pstWaitTask );

//	vSTI();
}

/************************************************************
*************************************************************
**      Function Name:			pstId1FindBuffer
**      Author:                 x.cheng
**
**      Comment:
**
**      List of parameters:
**			iDevice - which device.
**			iBlock - which block.
**
**      Return value:   
**          none 
**
**      Revisions:
**
*************************************************************
*************************************************************/
static ts_BufferBlock* pstId1FindBuffer(int iDevice, int iBlock)
{
	ts_BufferBlock* pstTemp;

	for ( pstTemp=pstHash(iDevice, iBlock); pstTemp!=NULL; pstTemp=pstTemp->pstNext ) {
		if ( pstTemp->uiDevice==(unsigned short)iDevice && pstTemp->ulBlockNr==(unsigned short)iBlock)
			return pstTemp;
	}
	
	return NULL;
}

/************************************************************
*************************************************************
**      Function Name:			Id1RemoveFromQueue
**      Author:                 x.cheng
**
**      Comment:
**
**      List of parameters:
**
**      Return value:   
**          none 
**
**      Revisions:
**
*************************************************************
*************************************************************/
static inline void Id1RemoveFromQueue( ts_BufferBlock *pstBlock)
{
	/* remove from hash-queue */
	if ( pstBlock->pstNext )
		pstBlock->pstNext->pstPrev = pstBlock->pstPrev;
	if ( pstBlock->pstPrev )
		pstBlock->pstPrev->pstNext = pstBlock->pstNext;

	if ( pstHash(pstBlock->uiDevice, pstBlock->ulBlockNr) == pstBlock )
		pstHash(pstBlock->uiDevice, pstBlock->ulBlockNr) = pstBlock->pstNext;

	/* remove from free list */
	if ( !(pstBlock->pstPrevFree) || !(pstBlock->pstNextFree) )
		PANIC1("Free block list corrupted\n");
	pstBlock->pstPrevFree->pstNextFree = pstBlock->pstNextFree;
	pstBlock->pstNextFree->pstPrevFree = pstBlock->pstPrevFree;

	if (g_pstFreeList == pstBlock)
		g_pstFreeList = pstBlock->pstNextFree;

}

/************************************************************
*************************************************************
**      Function Name:			Id1InsertToQueue
**      Author:                 x.cheng
**
**      Comment:
**
**      List of parameters:
**
**      Return value:   
**          none 
**
**      Revisions:
**
*************************************************************
*************************************************************/
static inline void Id1InsertToQueue( ts_BufferBlock *pstBlock)
{
	/* put at end of free list */
	pstBlock->pstNextFree = g_pstFreeList;
	pstBlock->pstPrevFree = g_pstFreeList->pstPrevFree;
	g_pstFreeList->pstPrevFree->pstNextFree = pstBlock;
	g_pstFreeList->pstPrevFree = pstBlock;

	/* put the buffer in new hash-queue if it has a device */
	pstBlock->pstPrev = NULL;
	pstBlock->pstNext = NULL;
	if ( !pstBlock->uiDevice )
		return;
	pstBlock->pstNext = pstHash(pstBlock->uiDevice, pstBlock->ulBlockNr);
	pstHash(pstBlock->uiDevice, pstBlock->ulBlockNr) = pstBlock;
	pstBlock->pstNext->pstPrev = pstBlock;

}