How to rewrite sbull_request in ldd3 for current kernel?

[Dongli Zhang]

Please refer to https://github.com/21cnbao/training/tree/50506cf04bc5616e0c3f3285dbb006c54deb1c53/kernel/drivers/vmem_disk

Dongli Zhang (张东立)
http://finallyjustice.github.io


________________________________
> From: zyunone at 163.com 
> Subject: How to rewrite sbull_request in ldd3 for current kernel? 
> Date: Sat, 19 Mar 2016 21:22:19 +0800 
> To: kernelnewbies at kernelnewbies.org 
> 
> Hi, 
> I am reading the book, Linux Driver Development 3. 
> In the chapter on block driver of this book, I need some help to 
> rewriting the sbull_request since the kernel’s block API was changed. 
> 
> The sbull_request code: 
> /* 
> * The simple form of the request function. 
> */ 
> static void sbull_request(request_queue_t *q) 
> { 
> struct request *req; 
> 
> while ((req = elv_next_request(q)) != NULL) { 
> struct sbull_dev *dev = req->rq_disk->private_data; 
> if (! blk_fs_request(req)) { 
> printk (KERN_NOTICE "Skip non-fs request\n"); 
> end_request(req, 0); 
> continue; 
> } 
> sbull_transfer(dev, req->sector, req->current_nr_sectors, 
> req->buffer, rq_data_dir(req)); 
> end_request(req, 1); 
> } 
> } 
> 
> I have rewritten the code above into: 
> 
> /* 
> * The simple form of the request function. 
> */ 
> void blkplay_request(struct request_queue *q) 
> { 
> struct request *req; 
> 
> while (!blk_queue_stopped(q) && 
> (req = blk_peek_request(q)) != NULL) { 
> struct blkplay_dev *dev = req->rq_disk->private_data; 
> blk_start_request(req); 
> if (req->cmd_type != REQ_TYPE_FS) { 
> printk (KERN_NOTICE "Skip non-fs request\n"); 
> blk_end_request(req, -EIO, 0); 
> continue; 
> } 
> 
> /* I don’t know how to write the statement below */ 
> blkplay_transfer(dev, req->sector, req->current_nr_sectors, 
> req->buffer, rq_data_dir(req)); 
> 
> blk_end_request_cur(req, 0); 
> } 
> } 
> 
> 
> Is the rewrite proper? 
> 
> 
> 
> The compiler can’t compile it because the request struct no longer has 
> 
> the field of ‘sector’ and ‘current_nr_sectors’. I have read the kernel code 
> 
> about the request struct, the kernel code said the __data_len and 
> __sector field of 
> request struct is internal so that we shouldn’t access them directly. 
> 
> How could I rewrite it ? Thanks. 
> 
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