linux 下面的虚拟块设备,就是将内存的一个部分虚拟为块设备,提高输入输出的效率.zip

// // Virtual Disk // #define __KERNEL__ #define MODULE // // Include the necessary head files // #include <linux/module.h> #include <linux/kernel.h> #include <linux/sched.h> #include <linux/fs.h> #include <linux/vmalloc.h> #include <asm/uaccess.h> #include <linux/blk.h> #define VIRTUAL_DISK_DEV_MAJOR 42 // The major number of the virtual disk device #define DEVICE_NAME "VirtualDisk" // The name of the virtual disk device #define VIRTUAL_DISK_SECTOR_SIZE 512 // disk sector size #define VIRTUAL_DISK_BLOCK_SIZE 1024 // block size in bytes #define VIRTUAL_DISK_BLOCK_SIZE_IN_SECTOR 2 // block size in sector #define VIRTUAL_DISK_TOTAL_SIZE_IN_BLOCK 10*1024 // size in blocks in blocks /* the storage pool */ static char *g_pVirtualDiskPool; // The pointer pointing the buffer used by our virtual disk static int g_iSectorSize = VIRTUAL_DISK_SECTOR_SIZE; static int g_iBlockSizeInBytes = VIRTUAL_DISK_BLOCK_SIZE; static int g_iDiskSizeInBlocks = VIRTUAL_DISK_TOTAL_SIZE_IN_BLOCK; static int g_iReadAheadCount = 4; // // _fops function declarations // static int VirtualDiskOpen (struct inode *pINode, struct file *pFile); static int VirtualDiskRelease (struct inode *pINode, struct file *pFile); static int VirtualDiskIoctl (struct inode *pINode, struct file *pFile, unsigned int iCmd, unsigned long ulArg); static struct block_device_operations g_fops = { open: VirtualDiskOpen, release: VirtualDiskRelease, ioctl: VirtualDiskIoctl, }; // // The function processing the read/write request // static int VirtualDiskRequest(request_queue_t *pRequestQueue, int rw, struct buffer_head *pBufferHead) { unsigned long ulOffset, ulTotal; //printk ("%s sector rsector = %lu, blocknr = %lu\n", rw == READ ? "read" : "write", pBufferHead->b_rsector, pBufferHead->b_blocknr); ulOffset = pBufferHead->b_rsector*VIRTUAL_DISK_SECTOR_SIZE; ulTotal = (unsigned long)pBufferHead->b_size; // // Access beyond end of the device // if (ulTotal + ulOffset > VIRTUAL_DISK_TOTAL_SIZE_IN_BLOCK * VIRTUAL_DISK_BLOCK_SIZE) { printk ("Error: access beyond end of the device"); // // Io error process // buffer_IO_error(pBufferHead); return 0; } if (rw == READ) { // // Copy from our memory pool to the buffer // memcpy(bh_kmap(pBufferHead), g_pVirtualDiskPool + ulOffset, ulTotal); } else if (rw == WRITE) { // // Copy from the buffer to our memory pool // memcpy(g_pVirtualDiskPool + ulOffset, bh_kmap(pBufferHead), ulTotal); } else { printk ("Error: Invalid command!"); } // // End I/O process // pBufferHead->b_end_io(pBufferHead,1); if (rw == READ) printk ("Read end successfully!\n"); else printk ("Write end successfully!\n"); return 0; } static int VirtualDiskRelease(struct inode *pINode, struct file *file) { // // Decrement reference count // MOD_DEC_USE_COUNT; return 0; } static int VirtualDiskOpen(struct inode *pINode, struct file *pFile) { // // Increment reference count // MOD_INC_USE_COUNT; return 0; } static int VirtualDiskIoctl (struct inode *pINode, struct file *pFile, unsigned int iCmd, unsigned long ulArg) { // // We can define some special command by pINode->i_rdev // unsigned int iMinor; int iTmp; if (!pINode || !pINode->i_rdev) return -EINVAL; iMinor = MINOR(pINode->i_rdev); switch (iCmd) { case BLKFLSBUF: // // Flush buffers content to storage device // printk ("ioctl: BLKFLSBUF\n"); // // Deny all but root // if (!capable(CAP_SYS_ADMIN)) return -EACCES; fsync_dev(pINode->i_rdev); invalidate_buffers(pINode->i_rdev); break; case BLKGETSIZE: // // Return device size // printk ("ioctl: BLKGETSIZE\n"); if (!ulArg) return -EINVAL; return put_user(VIRTUAL_DISK_TOTAL_SIZE_IN_BLOCK*VIRTUAL_DISK_BLOCK_SIZE_IN_SECTOR, (long *) ulArg); case BLKRASET: // // Set read ahead value // printk ("ioctl: BLKRASET\n"); if (get_user(iTmp, (long *)ulArg)) return -EINVAL; if (iTmp > 0xff) return -EINVAL; read_ahead[VIRTUAL_DISK_DEV_MAJOR] = iTmp; return 0; case BLKRAGET: // // Return read ahead value // printk ("ioctl: BLKRAGET\n"); if (!ulArg) return -EINVAL; return put_user(read_ahead[VIRTUAL_DISK_DEV_MAJOR], (long *)ulArg); case BLKSSZGET: // // Return block size // printk ("ioctl: BLKSSZGET\n"); if (!ulArg) return -EINVAL; return put_user(VIRTUAL_DISK_BLOCK_SIZE, (long *)ulArg); default: printk ("ioctl wanted\n"); return -ENOTTY; } return 0; } int init_module(void) { int iResult = 0; // // Verify block size must be a multiple of sector size // if (g_iBlockSizeInBytes & (VIRTUAL_DISK_SECTOR_SIZE - 1)) { printk ("Block size not a multiple of sector size\n"); return -EINVAL; } // // Allocate the buffer used by our disk // g_pVirtualDiskPool = (char *) vmalloc (VIRTUAL_DISK_BLOCK_SIZE*VIRTUAL_DISK_TOTAL_SIZE_IN_BLOCK); if (g_pVirtualDiskPool == NULL) { printk ("Not enough memory.\n"); return -ENOMEM; } memset(g_pVirtualDiskPool, 0, VIRTUAL_DISK_BLOCK_SIZE*VIRTUAL_DISK_TOTAL_SIZE_IN_BLOCK); // // Register our device to the devfs // if ((iResult = register_blkdev(VIRTUAL_DISK_DEV_MAJOR, DEVICE_NAME, &g_fops)) != 0) { printk ("couldn't register virtual disk device\n"); return iResult; } // // Register our disk information // hardsect_size [VIRTUAL_DISK_DEV_MAJOR] = &g_iSectorSize; blksize_size [VIRTUAL_DISK_DEV_MAJOR] = &g_iBlockSizeInBytes; blk_size [VIRTUAL_DISK_DEV_MAJOR] = &g_iDiskSizeInBlocks; // // Register our read/write function //建立自己的请求队列 blk_queue_make_request (BLK_DEFAULT_QUEUE(VIRTUAL_DISK_DEV_MAJOR), &VirtualDiskRequest); read_ahead [VIRTUAL_DISK_DEV_MAJOR] = g_iReadAheadCount; return 0; } void cleanup_module(void) { // // Unregister our block device // unregister_blkdev(VIRTUAL_DISK_DEV_MAJOR, DEVICE_NAME); invalidate_buffers (MKDEV(VIRTUAL_DISK_DEV_MAJOR, 0)); // // Invalidate our read/write funtion // blk_dev[VIRTUAL_DISK_DEV_MAJOR].request_queue.request_fn = 0; vfree(g_pVirtualDiskPool); } MODULE_LICENSE("GPL");