Messages in this thread | | | Date | Mon, 7 Jan 2002 16:37:49 -0500 (EST) | From | Michael Zhu <> | Subject | About the request queue of block device |
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Hello, everyone, I have a question about the request queue of block device.
I intercept the request function of floppy disk device by changing the pointer, "blk_dev[2].request_queue.request_fn", in my kernel module. The following is the source code.
original_request_fn_proc = blk_dev[2].request_queue.request_fn; blk_dev[2].request_queue.request_fn = my_request_fn_proc;
In my own my_request_fn_proc() I use the "req = blkdev_entry_next_request(&rq->queue_head)" function to get the pointer of the request structure. When req->cmd is WRITE I encrypt all the b_data buffer of the buffer header. Then I call the original_request_fn_proc(). And it works. The data on the floppy disk is some kind of cipher data. The trouble is when the req->cmd is READ. I don't know whether the b_data buffer contains the data read from the floppy disk after I call the original_request_fn_proc() function. When read a block from the block device, where is the data is placed?
In my module I use the blkdev_next_request() function to get the next request. When I want to do the same thing to this next request, the Linux kernel deadlocked. I must reboot the OS. What is wrong?
Any idea will be appreciated. Thanks in advance.
Michael
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