<linux>from lvm2 to device mapper
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/* * Add LV and any known dependencies */static int _add_lv_to_dtree(struct dev_manager *dm, struct dm_tree *dtree, struct logical_volume *lv){//...if (!_add_dev_to_dtree(dm, dtree, lv, NULL))return_0;//...return 1;}?_add_dev_to_dtree ---》int _info() ---》 dm_task_run()
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然后就是 dm 库
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int dm_task_run(struct dm_task *dmt){repeat_ioctl:/*关键就是这个*/if (!(dmi = _do_dm_ioctl(dmt, command, _ioctl_buffer_double_factor)))return 0;if (dmi->flags & DM_BUFFER_FULL_FLAG) {switch (dmt->type) {case DM_DEVICE_LIST_VERSIONS:case DM_DEVICE_LIST:case DM_DEVICE_DEPS:case DM_DEVICE_STATUS:case DM_DEVICE_TABLE:case DM_DEVICE_WAITEVENT:_ioctl_buffer_double_factor++;dm_free(dmi);goto repeat_ioctl;/*这里其实是在循环决定操作*/default:log_error("WARNING: libdevmapper buffer too small for data");}//...}??
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static struct dm_ioctl *_do_dm_ioctl(struct dm_task *dmt, unsigned command, unsigned repeat_count){struct dm_ioctl *dmi;dmi = _flatten(dmt, repeat_count);/*dm_task结构字段合法性检查*/if (!dmi) {log_error("Couldn't create ioctl argument.");return NULL;}if (dmt->type == DM_DEVICE_TABLE)dmi->flags |= DM_STATUS_TABLE_FLAG;dmi->flags |= DM_EXISTS_FLAG;/* FIXME */if (dmt->no_open_count)dmi->flags |= DM_SKIP_BDGET_FLAG;//...#ifdef DM_IOCTLSif (ioctl(_control_fd, command, dmi) < 0) {/*注意这里的dmi */if (errno == ENXIO && ((dmt->type == DM_DEVICE_INFO) || (dmt->type == DM_DEVICE_MKNODES) || (dmt->type == DM_DEVICE_STATUS)))dmi->flags &= ~DM_EXISTS_FLAG;/* FIXME */else {if (_log_suppress)log_verbose("device-mapper: %s ioctl " "failed: %s", _cmd_data_v4[dmt->type].name, strerror(errno));elselog_error("device-mapper: %s ioctl " "failed: %s", _cmd_data_v4[dmt->type].name, strerror(errno));dm_free(dmi);return NULL;}}#else /* Userspace alternative for testing */#endifreturn dmi;}??
int dm_task_run(struct dm_task *dmt){struct dm_ioctl *dmi;unsigned command;//...command = _cmd_data_v4[dmt->type].cmd;//...}?
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对应一个全局数组
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static struct cmd_data _cmd_data_v4[] = {{"create",DM_DEV_CREATE,{4, 0, 0}},{"reload",DM_TABLE_LOAD,{4, 0, 0}},{"remove",DM_DEV_REMOVE,{4, 0, 0}},{"remove_all",DM_REMOVE_ALL,{4, 0, 0}},{"suspend",DM_DEV_SUSPEND,{4, 0, 0}},{"resume",DM_DEV_SUSPEND,{4, 0, 0}},{"info",DM_DEV_STATUS,{4, 0, 0}},{"deps",DM_TABLE_DEPS,{4, 0, 0}},{"rename",DM_DEV_RENAME,{4, 0, 0}},{"version",DM_VERSION,{4, 0, 0}},{"status",DM_TABLE_STATUS,{4, 0, 0}},{"table",DM_TABLE_STATUS,{4, 0, 0}},{"waitevent",DM_DEV_WAIT,{4, 0, 0}},{"names",DM_LIST_DEVICES,{4, 0, 0}},{"clear",DM_TABLE_CLEAR,{4, 0, 0}},{"mknodes",DM_DEV_STATUS,{4, 0, 0}},#ifdef DM_LIST_VERSIONS{"versions",DM_LIST_VERSIONS,{4, 1, 0}},#endif#ifdef DM_TARGET_MSG{"message",DM_TARGET_MSG,{4, 2, 0}},#endif#ifdef DM_DEV_SET_GEOMETRY{"setgeometry",DM_DEV_SET_GEOMETRY,{4, 6, 0}},#endif};?前面就是 shell输入的命令。 关键就是?
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struct cmd_data {const char *name;const int cmd;const int version[3];};?
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#define DM_DEV_CREATE _IOWR(DM_IOCTL, DM_DEV_CREATE_CMD, struct dm_ioctl)/*.....................*/#define _IOWR(type,nr,size)_IOC(_IOC_READ|_IOC_WRITE,(type),(nr),sizeof(size))??
比如我们通过shell 调用[root]\> dmsetup create kko txt
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#define DM_IOCTL 0xfd?
关键的 _IOWR_(nr) 的序号就是
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enum {/* Top level cmds */DM_VERSION_CMD = 0,DM_REMOVE_ALL_CMD,DM_LIST_DEVICES_CMD,/* device level cmds */DM_DEV_CREATE_CMD,DM_DEV_REMOVE_CMD,DM_DEV_RENAME_CMD,DM_DEV_SUSPEND_CMD,DM_DEV_STATUS_CMD,DM_DEV_WAIT_CMD,/* Table level cmds */DM_TABLE_LOAD_CMD,DM_TABLE_CLEAR_CMD,DM_TABLE_DEPS_CMD,DM_TABLE_STATUS_CMD,/* Added later */DM_LIST_VERSIONS_CMD,DM_TARGET_MSG_CMD,DM_DEV_SET_GEOMETRY_CMD};?
所以DM_DEV_CREATE 就是 03
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明白这个几个宏之后 ， 就去内核看看处理
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device_mapper 主要的代码都在 ?/drivers/md 里面
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首先看一下和上面 ioctl 一一对应的一个结构体?
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1 先注册fs 的操作类
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static const struct file_operations _ctl_fops = {.open = nonseekable_open,.unlocked_ioctl = dm_ctl_ioctl,.compat_ioctl = dm_compat_ctl_ioctl,.owner = THIS_MODULE,.llseek = noop_llseek,};?
当用户调用 ioctl 的时候(上面分析过) 通过字符设备 ?就会调用内核的.unlocked_ioctl
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2 接下来就是dm_ctl_ioctl()->ctl_ioctl() -> lookup_ioctl()
static ioctl_fn lookup_ioctl(unsigned int cmd){static struct {int cmd;ioctl_fn fn;} _ioctls[] = {{DM_VERSION_CMD, NULL},/* version is dealt with elsewhere */{DM_REMOVE_ALL_CMD, remove_all},{DM_LIST_DEVICES_CMD, list_devices},{DM_DEV_CREATE_CMD, dev_create},{DM_DEV_REMOVE_CMD, dev_remove},{DM_DEV_RENAME_CMD, dev_rename},{DM_DEV_SUSPEND_CMD, dev_suspend},{DM_DEV_STATUS_CMD, dev_status},{DM_DEV_WAIT_CMD, dev_wait},{DM_TABLE_LOAD_CMD, table_load},{DM_TABLE_CLEAR_CMD, table_clear},{DM_TABLE_DEPS_CMD, table_deps},{DM_TABLE_STATUS_CMD, table_status},{DM_LIST_VERSIONS_CMD, list_versions},{DM_TARGET_MSG_CMD, target_message},{DM_DEV_SET_GEOMETRY_CMD, dev_set_geometry}};return (cmd >= ARRAY_SIZE(_ioctls)) ? NULL : _ioctls[cmd].fn;}??
按上面的 shell [root]\>dmsetup create xxx
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???gdb ?
static int dev_create(struct dm_ioctl *param, size_t param_size){int r, m = DM_ANY_MINOR;struct mapped_device *md;r = check_name(param->name);/*这个就是dmsetup create 后面跟的名字*/if (r)return r;if (param->flags & DM_PERSISTENT_DEV_FLAG)/*这里一般都是由内核自己制定一个未用的主备设备号*/m = MINOR(huge_decode_dev(param->dev));r = dm_create(m, &md);/*初始化mapped_device */if (r)return r;/*hash插入mapped_device到全局 static struct list_head _name_buckets[NUM_BUCKETS];*/r = dm_hash_insert(param->name, *param->uuid ? param->uuid : NULL, md);if (r) {dm_put(md);dm_destroy(md);return r;}param->flags &= ~DM_INACTIVE_PRESENT_FLAG;__dev_status(md, param);dm_put(md);return 0;}?
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接着gdb ?就会发现第二次调用 ioctl 的地方
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static int table_load(struct dm_ioctl *param, size_t param_size){int r;struct hash_cell *hc;struct dm_table *t;struct mapped_device *md;/*在hash表中找到操作对应的mapped_device */md = find_device(param);if (!md)return -ENXIO;/*产生一个dm_table 结构*/r = dm_table_create(&t, get_mode(param), param->target_count, md);if (r)goto out;/*通过dm_table_add_target 初始化需要的dm_taget结构 并且保持在一颗对应md 的btree上*/r = populate_table(t, param, param_size);if (r) {dm_table_destroy(t);goto out;}/* Protect md->type and md->queue against concurrent table loads. */dm_lock_md_type(md);if (dm_get_md_type(md) == DM_TYPE_NONE)/* Initial table load: acquire type of table. */dm_set_md_type(md, dm_table_get_type(t));else if (dm_get_md_type(md) != dm_table_get_type(t)) {DMWARN("can't change device type after initial table load.");dm_table_destroy(t);dm_unlock_md_type(md);r = -EINVAL;goto out;}/* setup md->queue to reflect md's type (may block) */r = dm_setup_md_queue(md);/*初始化DM vfs 请求队列*/if (r) {DMWARN("unable to set up device queue for new table.");dm_table_destroy(t);dm_unlock_md_type(md);goto out;}dm_unlock_md_type(md);/* stage inactive table */down_write(&_hash_lock);hc = dm_get_mdptr(md);if (!hc || hc->md != md) {DMWARN("device has been removed from the dev hash table.");dm_table_destroy(t);up_write(&_hash_lock);r = -ENXIO;goto out;}if (hc->new_map)dm_table_destroy(hc->new_map);hc->new_map = t;/*放入hash 结构中*/up_write(&_hash_lock);param->flags |= DM_INACTIVE_PRESENT_FLAG;__dev_status(md, param);out:dm_put(md);return r;}??
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接着gdb ?就会发现第三次调用 ioctl 的地方
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gdb?p command /*第一次调用ioctl(,command,)*/?
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?static int dev_suspend(struct dm_ioctl *param, size_t param_size)
{if (param->flags & DM_SUSPEND_FLAG)return do_suspend(param);/*用新的 dm_table 激活mapped device*/return do_resume(param);}??
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这里补充一下关于 lvm2 伟大的逻辑卷管理：
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大家都知道 lvm2 会把自己的卷组信息写在分区的前512个字节上。 主要通过 ?dev-io.c
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的 _io() 方法，操作原始磁盘 这块尤其重要 这个后面再看。
static int _io(struct device_area *where, void *buffer, int should_write)?
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而所有的备份 灾难恢复秘密都在 Archive.c 文件中
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外部的接口主要有：?
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int vgcfgrestore(struct cmd_context *cmd, int argc, char **argv)
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—>
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int archive_display(struct cmd_context *cmd, const char *vg_name)
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--->
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int archive_list(struct cmd_context *cmd, const char *dir, const char *vgname)
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/* * Returns a list of archive_files. */static struct list *_scan_archive(struct dm_pool *mem, const char *vgname, const char *dir)
??明白了吧 。所以你可以在 [root]\> 输入?
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?[root@localhost home]# vgcfgrestore别的关于 vgcfg 大家可以自己看
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对于备份 ?vgcfgbackup
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主要的流程就是?
--->int process_each_vg()
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然后会去找当前有效的VG 然后通过_process_one_vg ?接下里就是通过
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vg = vg_read(cmd, vg_name, vgid, &consistent)
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(这里的struct cmd_context *cmd 里面记录了)
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struct cmd_context {//....struct list config_files;int config_valid;struct config_tree *cft;struct config_tree *cft_override;struct config_info default_settings;struct config_info current_settings;struct archive_params *archive_params;struct backup_params *backup_params;/* List of defined tags */struct list tags;int hosttags;/*目录的的路径 */char sys_dir[PATH_MAX];/*一般是: /etc/lvm*/char dev_dir[PATH_MAX];/*一般是: /dev/*/char proc_dir[PATH_MAX];/*一般是: /proc*/};??
关键的部分到了
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->>>?
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archiver.c:
?int backup(struct volume_group *vg)
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?? ? ? ? ? ?int __backup(struct volume_group *vg)
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?? ? ? ? ? ? ? ?backup_to_file(name, desc, vg);
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好的 lvm 的基本 skeleton 就这样了。。 ?别的都能看懂， 我不分析了?
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