磁盘槽位和盘符绑定方案

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Linux下的SCSI设备都是按照设备的发现顺序命名的，对于磁盘盘符名称就是sda，sdb，sdc等等。存储设备一般都配有很多块磁盘，盘符名称和槽位号没有对应关系，当磁盘插入，拔出时对应的盘符可能会变化。这给使用和运维带来很多不便。

对于SCSI磁盘可通过修改sd_mod模块中的sd_probe（drivers/scsi/sd.c）来完成“磁盘槽位和盘符”的绑定。

/** *sd_probe - called during driver initialization and whenever a *new scsi device is attached to the system. It is called once *for each scsi device (not just disks) present. *@dev: pointer to device object * *Returns 0 if successful (or not interested in this scsi device  *(e.g. scanner)); 1 when there is an error. * *Note: this function is invoked from the scsi mid-level. *This function sets up the mapping between a given  *<host,channel,id,lun> (found in sdp) and new device name  *(e.g. /dev/sda). More precisely it is the block device major  *and minor number that is chosen here. * *Assume sd_attach is not re-entrant (for time being) *Also think about sd_attach() and sd_remove() running coincidentally. **/static int sd_probe(struct device *dev){struct scsi_device *sdp = to_scsi_device(dev);struct scsi_disk *sdkp;struct gendisk *gd;u32 index;int error;error = -ENODEV;if (sdp->type != TYPE_DISK && sdp->type != TYPE_MOD && sdp->type != TYPE_RBC)goto out;SCSI_LOG_HLQUEUE(3, sdev_printk(KERN_INFO, sdp,"sd_attach\n"));error = -ENOMEM;sdkp = kzalloc(sizeof(*sdkp), GFP_KERNEL);if (!sdkp)goto out;gd = alloc_disk(SD_MINORS);if (!gd)goto out_free;do {if (!ida_pre_get(&sd_index_ida, GFP_KERNEL))goto out_put;spin_lock(&sd_index_lock);error = ida_get_new(&sd_index_ida, &index);spin_unlock(&sd_index_lock);} while (error == -EAGAIN);if (error)goto out_put;if (index >= SD_MAX_DISKS) {error = -ENODEV;sdev_printk(KERN_WARNING, sdp, "SCSI disk (sd) name space exhausted.\n");goto out_free_index;}error = sd_format_disk_name("sd", index, gd->disk_name, DISK_NAME_LEN);if (error)goto out_free_index;              sdkp->device = sdp;      sdkp->driver = &sd_template;                                                                             sdkp->disk = gd;      sdkp->index = index;                                                                                     sdkp->openers = 0;      sdkp->previous_state = 1;          ......}

具体负责给gendisk分配磁盘名称的就是 sd_format_disk_name，而决定磁盘名称的index这个参数。index通过ida_get_new（include/linux/idr.h）获取。ida是基于idr（底层是radix tree）实现的id分配器。从ida分配的index会被赋值给scsi_disk（drivers/scsi/sd.h）中的index，这个域作为SCSI磁盘的索引，系统内唯一，不仅确定了设备名而且确定了设备的主设备号和次设备号（关于scsi_disk->index如何确定设备号可参见sd_probe_async）。为了完成槽位和盘符绑定我们需要一个磁盘槽位和index的对应关系，这个对应关系可以根据系统中的一些不变量，如磁盘控制器的SCSI host号（系统范围内唯一编号，用于标识这个主机适配器）来确定。Linux系统中SATA磁盘控制器上的每个磁盘都会被映射到一个单独的SCSI host，对于只使用SATA控制器的阵列而言，可以采用如下方式绑定磁盘槽位和盘符。

以下是笔者根据scsi host（针对某款特定主板）确定SATA磁盘盘符对应关系的Patch：

将sd_probe中ida_get_new替换为ida_get_new_above，这样每次分配的index == host_no。

do {        if (!ida_pre_get(&sd_index_ida, GFP_KERNEL))            goto out_put;        host_no = sdp->host->host_no;        spin_lock(&sd_index_lock);        //error = ida_get_new(&sd_index_ida, &index);        error = ida_get_new_above(&sd_index_ida, host_no, &index);        spin_unlock(&sd_index_lock);} while (error == -EAGAIN);

转载请注明出处：http://blog.csdn.net/lkkey80/article/details/50263083

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