如何识别Linux块设备的请求队列

Question 1

我正在研究通过网络连接硬盘的驱动程序。有一个错误，如果我在计算机上启用了两个或多个硬盘，则只有第一个硬盘可以查看并识别分区。结果是，如果我在hda上有1个分区，而在hdb上有1个分区，那么当我连接hda时，就会有一个可以挂载的分区。因此，hda1在挂载后立即获得blkid xyz123。但是当我继续安装hdb1时，它也出现了相同的blkid，实际上，驱动程序是从hda而不是hdb读取的。

所以我想我找到了司机搞砸的地方。下面是一个调试输出，包括一个dump_stack，我将其放在第一个似乎访问错误设备的位置。

这是代码部分：

/*basically, this is just the request_queue processor. In the log output that
  follows, the second device, (hdb) has just been connected, right after hda
  was connected and hda1 was mounted to the system. */

void nblk_request_proc(struct request_queue *q)
{
struct request *req;
ndas_error_t err = NDAS_OK;

dump_stack();

while((req = NBLK_NEXT_REQUEST(q)) != NULL)
{
    dbgl_blk(8,"processing queue request from slot %d",SLOT_R(req));

    if (test_bit(NDAS_FLAG_QUEUE_SUSPENDED, &(NDAS_GET_SLOT_DEV(SLOT_R(req))->queue_flags)))  {
        printk ("ndas: Queue is suspended\n");
        /* Queue is suspended */
#if ( LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,31) )
        blk_start_request(req);
#else
        blkdev_dequeue_request(req);
#endif

这是日志输出。我添加了一些评论来帮助您了解正在发生的事情以及坏电话似乎出现的地方。

  /* Just below here you can see "slot" mentioned many times. This is the 
     identification for the network case in which the hd is connected to the 
     network. So you will see slot 2 in this log because the first device has 
     already been connected and mounted. */

  kernel: [231644.155503] BL|4|slot_enable|/driver/block/ctrldev.c:281|adding disk: slot=2, first_minor=16, capacity=976769072|nd/dpcd1,64:15:44.38,3828:10
  kernel: [231644.155588] BL|3|ndop_open|/driver/block/ops.c:233|ing bdev=f6823400|nd/dpcd1,64:15:44.38,3720:10
  kernel: [231644.155598] BL|2|ndop_open|/driver/block/ops.c:247|slot =0x2|nd/dpcd1,64:15:44.38,3720:10
  kernel: [231644.155606] BL|2|ndop_open|/driver/block/ops.c:248|dev_t=0x3c00010|nd/dpcd1,64:15:44.38,3720:10
  kernel: [231644.155615] ND|3|ndas_query_slot|netdisk/nddev.c:791|slot=2 sdev=d33e2080|nd/dpcd1,64:15:44.38,3696:10
  kernel: [231644.155624] ND|3|ndas_query_slot|netdisk/nddev.c:817|ed|nd/dpcd1,64:15:44.38,3696:10
  kernel: [231644.155631] BL|3|ndop_open|/driver/block/ops.c:326|mode=1|nd/dpcd1,64:15:44.38,3720:10
  kernel: [231644.155640] BL|3|ndop_open|/driver/block/ops.c:365|ed open|nd/dpcd1,64:15:44.38,3724:10
  kernel: [231644.155653] BL|8|ndop_revalidate_disk|/driver/block/ops.c:2334|gendisk=c6afd800={major=60,first_minor=16,minors=0x10,disk_name=ndas-44700486-0,private_data=00000002,capacity=%lld}|nd/dpcd1,64:15:44.38,3660:10
  kernel: [231644.155668] BL|8|ndop_revalidate_disk|/driver/block/ops.c:2346|ed|nd/dpcd1,64:15:44.38,3652:10

  /* So at this point the hard disk is added (gendisk=c6...) and the identifications
     all match the network device. The driver is now about to begin scanning the 
     hard drive for existing partitions. the little 'ed', at the end of the previous
     line indicates that revalidate_disk has finished it's job. 

     Also, I think the request queue is indicated by the output dpcd1 near the very
     end of the line. 

     Now below we have entered the function that is pasted above. In the function
     you can see that the slot can be determined by the queue. And the log output
     after the stack dump shows it is from slot 1. (The first network drive that was
     already mounted.) */

        kernel: [231644.155677]  ndas-44700486-0:Pid: 467, comm: nd/dpcd1 Tainted: P           2.6.32-5-686 #1
  kernel: [231644.155711] Call Trace:
  kernel: [231644.155723]  [<fc5a7685>] ? nblk_request_proc+0x9/0x10c [ndas_block]
  kernel: [231644.155732]  [<c11298db>] ? __generic_unplug_device+0x23/0x25
  kernel: [231644.155737]  [<c1129afb>] ? generic_unplug_device+0x1e/0x2e
  kernel: [231644.155743]  [<c1123090>] ? blk_unplug+0x2e/0x31
  kernel: [231644.155750]  [<c10cceec>] ? block_sync_page+0x33/0x34
  kernel: [231644.155756]  [<c108770c>] ? sync_page+0x35/0x3d
  kernel: [231644.155763]  [<c126d568>] ? __wait_on_bit_lock+0x31/0x6a
  kernel: [231644.155768]  [<c10876d7>] ? sync_page+0x0/0x3d
  kernel: [231644.155773]  [<c10876aa>] ? __lock_page+0x76/0x7e
  kernel: [231644.155780]  [<c1043f1f>] ? wake_bit_function+0x0/0x3c
  kernel: [231644.155785]  [<c1087b76>] ? do_read_cache_page+0xdf/0xf8
  kernel: [231644.155791]  [<c10d21b9>] ? blkdev_readpage+0x0/0xc
  kernel: [231644.155796]  [<c1087bbc>] ? read_cache_page_async+0x14/0x18
  kernel: [231644.155801]  [<c1087bc9>] ? read_cache_page+0x9/0xf
  kernel: [231644.155808]  [<c10ed6fc>] ? read_dev_sector+0x26/0x60
  kernel: [231644.155813]  [<c10ee368>] ? adfspart_check_ICS+0x20/0x14c
  kernel: [231644.155819]  [<c10ee138>] ? rescan_partitions+0x17e/0x378
  kernel: [231644.155825]  [<c10ee348>] ? adfspart_check_ICS+0x0/0x14c
  kernel: [231644.155830]  [<c10d26a3>] ? __blkdev_get+0x225/0x2c7
  kernel: [231644.155836]  [<c10ed7e6>] ? register_disk+0xb0/0xfd
  kernel: [231644.155843]  [<c112e33b>] ? add_disk+0x9a/0xe8
  kernel: [231644.155848]  [<c112dafd>] ? exact_match+0x0/0x4
  kernel: [231644.155853]  [<c112deae>] ? exact_lock+0x0/0xd
  kernel: [231644.155861]  [<fc5a8b80>] ? slot_enable+0x405/0x4a5 [ndas_block]
  kernel: [231644.155868]  [<fc5a8c63>] ? ndcmd_enabled_handler+0x43/0x9e [ndas_block]
  kernel: [231644.155874]  [<fc5a8c20>] ? ndcmd_enabled_handler+0x0/0x9e [ndas_block]
  kernel: [231644.155891]  [<fc54b22b>] ? notify_func+0x38/0x4b [ndas_core]
  kernel: [231644.155906]  [<fc561cba>] ? _dpc_cancel+0x17c/0x626 [ndas_core]
  kernel: [231644.155919]  [<fc562005>] ? _dpc_cancel+0x4c7/0x626 [ndas_core]
  kernel: [231644.155933]  [<fc561cba>] ? _dpc_cancel+0x17c/0x626 [ndas_core]
  kernel: [231644.155941]  [<c1003d47>] ? kernel_thread_helper+0x7/0x10

  /* here are the output of the driver debugs. They show that this operation is
     being performed on the first devices request queue. */

  kernel: [231644.155948] BL|8|nblk_request_proc|/driver/block/block26.c:494|processing queue request from slot 1|nd/dpcd1,64:15:44.38,3408:10
  kernel: [231644.155959] BL|8|nblk_handle_io|/driver/block/block26.c:374|struct ndas_slot sd = NDAS GET SLOT DEV(slot 1)
  kernel: [231644.155966] |nd/dpcd1,64:15:44.38,3328:10
  kernel: [231644.155970] BL|8|nblk_handle_io|/driver/block/block26.c:458|case READA call ndas_read(slot=1, ndas_req)|nd/dpcd1,64:15:44.38,3328:10
  kernel: [231644.155979] ND|8|ndas_read|netdisk/nddev.c:824|read io: slot=1, cmd=0, req=x00|nd/dpcd1,64:15:44.38,3320:10

我希望这是足够的背景信息。现在可能有一个明显的问题是“在什么时候在哪里分配request_queue？”

好了，在add_disk函数之前进行了一点处理。添加磁盘，是日志输出的第一行。

slot->disk = NULL;
spin_lock_init(&slot->lock);
slot->queue = blk_init_queue(
    nblk_request_proc, 
    &slot->lock
);

据我所知，这是标准操作。回到我原来的问题。我可以在某处找到请求队列，并确保每个新设备的请求队列都是递增的或唯一的，或者Linux内核是否对每个主设备号仅使用一个队列？我想发现为什么该驱动程序在两个不同的块存储上加载相同的队列，并确定在初始注册过程中是否导致重复的blkid。

感谢您为我查看这种情况。

Question 2

Queue = blk_init_queue(sbd_request, &Device.lock);

Question 3

我与导致我发布此问题的错误的解决方案相同。尽管它实际上并未回答如何识别设备请求队列的问题。

在上面的代码中是以下内容：

if (test_bit(NDAS_FLAG_QUEUE_SUSPENDED, 
       &(NDAS_GET_SLOT_DEV(SLOT_R(req))->queue_flags)))

好吧，那是“ SLOT_R（req）”引起的麻烦。那是定义返回gendisk设备的其他位置。

#define SLOT_R(_request_) SLOT((_request_)->rq_disk)

这将返回磁盘，但稍后将不提供用于各种操作的正确值。因此，当加载了额外的块设备时，此函数基本上保持返回1。

解决方法是访问将磁盘添加到系统时已存储在磁盘的private_data中的正确磁盘标识值。

Correct identifier definition:
   #define SLOT_R(_request_) ( (int) _request_->rq_disk->private_data )

How the correct disk number was stored.
   slot->disk->queue = slot->queue;
   slot->disk->private_data = (void*) (long) s;  <-- 's' is the disk id
   slot->queue_flags = 0;

现在，从私有数据返回了正确的磁盘ID，因此所有请求都发送到了正确的队列。

如前所述，这并未显示如何识别队列。没有根据的猜测可能是：

 x = (int) _request_->rq_disk->queue->id;

参考在Linux中request_queue功能 http://lxr.free-electrons.com/source/include/linux/blkdev.h#L270＆321

谢谢大家的帮助！