linux内核md源代码解读 三 阵列建设的进程

这个文件为什么不放在md目录而放在include目录下？是因为文件里的内容是用户态跟内核态共用的，如果是内核态单独用的就没有必要放在这里了。

对于阵列的创建流程，最关心的命令字有：

SET_ARRAY_INFO  设置阵列信息

ADD_NEW_DISK     添加磁盘到阵列

RUN_ARRAY           运行阵列

首先看设置阵列信息，这个函数是这三个函数中最简单的一个：

6000 /* 
6001  * set_array_info is used two different ways 
6002  * The original usage is when creating a new array. 
6003  * In this usage, raid_disks is > 0 and it together with 
6004  *  level, size, not_persistent,layout,chunksize determine the 
6005  *  shape of the array. 
6006  *  This will always create an array with a type-0.90.0 superblock. 
6007  * The newer usage is when assembling an array. 
6008  *  In this case raid_disks will be 0, and the major_version field is 
6009  *  use to determine which style super-blocks are to be found on the devices. 
6010  *  The minor and patch _version numbers are also kept incase the 
6011  *  super_block handler wishes to interpret them. 
6012  */
6013 static int set_array_info(struct mddev * mddev, mdu_array_info_t *info)  
6014 {  
6015   
6016         if (info->raid_disks == 0) {  
6017                 /* just setting version number for superblock loading */
6018                 if (info->major_version < 0 ||  
6019                     info->major_version >= ARRAY_SIZE(super_types) ||  
6020                     super_types[info->major_version].name == NULL) {  
6021                         /* maybe try to auto-load a module? */
6022                         printk(KERN_INFO   
6023                                 "md: superblock version %d not knownn",  
6024                                 info->major_version);  
6025                         return -EINVAL;  
6026                 }  
6027                 mddev->major_version = info->major_version;  
6028                 mddev->minor_version = info->minor_version;  
6029                 mddev->patch_version = info->patch_version;  
6030                 mddev->persistent = !info->not_persistent;  
6031                 /* ensure mddev_put doesn't delete this now that there 
6032                  * is some minimal configuration. 
6033                  */
6034                 mddev->ctime         = get_seconds();  
6035                 return 0;  
6036         }  
6037         mddev->major_version = MD_MAJOR_VERSION;  
6038         mddev->minor_version = MD_MINOR_VERSION;  
6039         mddev->patch_version = MD_PATCHLEVEL_VERSION;  
6040         mddev->ctime         = get_seconds();  
6041   
6042         mddev->level         = info->level;  
6043         mddev->clevel[0]     = 0;  
6044         mddev->dev_sectors   = 2 * (sector_t)info->size;  
6045         mddev->raid_disks    = info->raid_disks;  
6046         /* don't set md_minor, it is determined by which /dev/md* was 
6047          * openned 
6048          */
6049         if (info->state & (1<<MD_SB_CLEAN))  
6050                 mddev->recovery_cp = MaxSector;  
6051         else
6052                 mddev->recovery_cp = 0;  
6053         mddev->persistent    = ! info->not_persistent;  
6054         mddev->external      = 0;  
6055   
6056         mddev->layout        = info->layout;  
6057         mddev->chunk_sectors = info->chunk_size >> 9;  
6058   
6059         mddev->max_disks     = MD_SB_DISKS;  
6060   
6061         if (mddev->persistent)  
6062                 mddev->flags         = 0;  
6063         set_bit(MD_CHANGE_DEVS, &mddev->flags);  
6064   
6065         mddev->bitmap_info.default_offset = MD_SB_BYTES >> 9;  
6066         mddev->bitmap_info.default_space = 64*2 - (MD_SB_BYTES >> 9);  
6067         mddev->bitmap_info.offset = 0;  
6068   
6069         mddev->reshape_position = MaxSector;  
6070   
6071         /* 
6072          * Generate a 128 bit UUID 
6073          */
6074         get_random_bytes(mddev->uuid, 16);  
6075   
6076         mddev->new_level = mddev->level;  
6077         mddev->new_chunk_sectors = mddev->chunk_sectors;  
6078         mddev->new_layout = mddev->layout;  
6079         mddev->delta_disks = 0;  
6080         mddev->reshape_backwards = 0;  
6081   
6082         return 0;  
6083 }

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