pvcreate代码分析

LVM代码分析1.探索pvcreate函数大致的执行过程1.1. p vcreate/** 代码1*/int pvcreate(struct cmd_context *cmd, int argc, char **argv){int i;int ret = ECMD_PROCESSED;struct pvcreate_params pp;struct physical_volume *pv;/* 给pp设置默认值*/pvcreate_params_set_defaults(&pp);/* 检查pvcreate需要保存到磁盘的参数，如restorefile、uuid，并传给pp结构体*/ if (!pvcreate_restore_params_validate(cmd, argc, argv, &pp)) {return EINV ALID_CMD_LINE;}/* 检查pvcreate不需要保存到磁盘的参数（见man pvcreate），并传给pp结构体*/ if (!pvcreate_params_validate(cmd, argc, argv, &pp)) {return EINV ALID_CMD_LINE;}/* 将用户输入的所有device转换成PV */for (i = 0; i < argc; i++) {if (!lock_vol(cmd, VG_ORPHANS, LCK_VG_WRITE)) {log_error("Can't get lock for orphan PVs");return ECMD_FAILED;}dm_unescape_colons_and_at_signs(argv[i], NULL, NULL);/* 单独转换一个device，详见代码2 */if (!(pv = pvcreate_single(cmd, argv[i], &pp, 1))) {stack;ret = ECMD_FAILED;}unlock_vg(cmd, VG_ORPHANS);if (sigint_caught())return ret;}return ret;}1.2. p vcreate_single/** 代码2* pvcreate_single() - initialize a device with PV label and metadata area** Parameters:* - pv_name: device path to initialize* - pp: parameters to pass to pv_create; if NULL, use default values** Returns:* NULL: error* struct physical_volume * (non-NULL): handle to physical volume created*/struct physical_volume * pvcreate_single(struct cmd_context *cmd,const char *pv_name,struct pvcreate_params *pp,int write_now){struct physical_volume *pv = NULL;struct device *dev;struct dm_list mdas;struct pvcreate_params default_pp;char buffer[64] __attribute__((aligned(8)));/* 给pp设置默认值，pp保存的是pvcreate命令创建PV时的参数。

可以由用户指定，否则使用默认值*/ pvcreate_params_set_defaults(&default_pp);if (!pp) // 如果pp未定义，则使用默认的pp值pp = &default_pp;if (pp->idp) {// 如果UUID存在（比如用户指定一个UUID）if ((dev = lvmcache_device_from_pvid(cmd, pp->idp, NULL, NULL)) && // 查看此UUID是否在lvm缓存中已经存在对应的设备(dev != dev_cache_get(pv_name, cmd->filter))) { // 在缓存中查看用户输入的pv_name对应的设备if (!id_write_format((const struct id*)&pp->idp->uuid,buffer, sizeof(buffer)))goto_bad;log_error("uuid %s already in use on \"%s\"", buffer,dev_name(dev));goto bad;;}}// 上述缓存为两个hash表，在lvm启动的时候初始化if (!pvcreate_check(cmd, pv_name, pp))goto_bad;if (sigint_caught())goto_bad;if (!(dev = dev_cache_get(pv_name, cmd->filter))) {log_error("%s: Couldn't find device. Check your filters?",pv_name);goto bad;}dm_list_init(&mdas);/* pv_create函数见代码3，作用是：创建并填充pv结构体*/if (!(pv = pv_create(cmd, dev, pp->idp, pp->size,pp->data_alignment, pp->data_alignment_offset,pp->pe_start ? pp->pe_start : PV_PE_START_CALC,pp->extent_count, pp->extent_size,pp->labelsector, pp->pvmetadatacopies,pp->pvmetadatasize, pp->metadataignore))) {log_error("Failed to setup physical volume \"%s\"", pv_name);goto bad;}log_verbose("Set up physical volume for \"%s\" with %" PRIu64" available sectors", pv_name, pv_size(pv));if (write_now) {struct pv_to_create pvc;pvc.pp = pp;pvc.pv = pv;if (!_pvcreate_write(cmd, &pvc)) //将pv和pp的信息写到磁盘，详见代码4 goto bad;} else {pv->status |= UNLABELLED_PV;}return pv;bad:return NULL;}1.3. p v_create/*** 代码3* pv_create - initialize a physical volume for use with a volume group * created PV belongs to Orphan VG.** @fmt: format type* @dev: PV device to initialize* @size: size of the PV in sectors* @data_alignment: requested alignment of data* @data_alignment_offset: requested offset to aligned data * @pe_start: physical extent start* @existing_extent_count* @existing_extent_size* @pvmetadatacopies* @pvmetadatasize* @mdas** Returns:* PV handle - physical volume initialized successfully * NULL - invalid parameter or problem initializing the physical volume ** Note:* FIXME: shorten argument list and replace with explict 'set' functions */struct physical_volume *pv_create(const struct cmd_context *cmd, struct device *dev,struct id *id, uint64_t size, unsigned long data_alignment, unsigned long data_alignment_offset,uint64_t pe_start,uint32_t existing_extent_count,uint32_t existing_extent_size,uint64_t label_sector,unsigned pvmetadatacopies,uint64_t pvmetadatasize,unsigned metadataignore){const struct format_type *fmt = cmd->fmt;struct dm_pool *mem = fmt->orphan_vg->vgmem;struct physical_volume *pv = _alloc_pv(mem, dev);unsigned mda_index;struct pv_list *pvl;if (!pv)return_NULL;if (id)memcpy(&pv->id, id, sizeof(*id));else if (!id_create(&pv->id)) {log_error("Failed to create random uuid for %s.",dev_name(dev));goto bad;}if (!dev_get_size(pv->dev, &pv->size)) {log_error("%s: Couldn't get size.", pv_dev_name(pv));goto bad;}if (size) {if (size > pv->size)log_warn("WARNING: %s: Overriding real size. ""Y ou could lose data.", pv_dev_name(pv));log_verbose("%s: Pretending size is %" PRIu64 " sectors.",pv_dev_name(pv), size);pv->size = size;}if (pv->size < pv_min_size()) {log_error("%s: Size must exceed minimum of %" PRIu64 " sectors.", pv_dev_name(pv), pv_min_size());goto bad;}if (pv->size < data_alignment) {log_error("%s: Data alignment must not exceed device size.", pv_dev_name(pv));goto bad;}if (!(pvl = dm_pool_zalloc(mem, sizeof(*pvl)))) {log_error("pv_list allocation in pv_create failed");goto bad;}pvl->pv = pv;add_pvl_to_vgs(fmt->orphan_vg, pvl);fmt->orphan_vg->extent_count += pv->pe_count;fmt->orphan_vg->free_count += pv->pe_count;pv->fmt = fmt;pv->vg_name = fmt->orphan_vg_name;if (!fmt->ops->pv_initialise(fmt, label_sector, pe_start,existing_extent_count, existing_extent_size,data_alignment, data_alignment_offset, pv)) { log_error("Format-specific initialisation of physical ""volume %s failed.", pv_dev_name(pv));goto bad;}for (mda_index = 0; mda_index < pvmetadatacopies; mda_index++) { if (pv->fmt->ops->pv_add_metadata_area &&!pv->fmt->ops->pv_add_metadata_area(pv->fmt, pv,pe_start != PV_PE_START_CALC,mda_index, pvmetadatasize,metadataignore)) {log_error("Failed to add metadata area for ""new physical volume %s", pv_dev_name(pv));goto bad;}}return pv;bad:// FIXME: detach from orphan in error path//free_pv_fid(pv);//dm_pool_free(mem, pv);}1.4. _pvcreate_write/** 代码4*/static int _pvcreate_write(struct cmd_context *cmd, struct pv_to_create *pvc){int zero = pvc->pp->zero;struct physical_volume *pv = pvc->pv;struct device *dev = pv->dev;const char *pv_name = dev_name(dev);/* Wipe existing label first */if (!label_remove(pv_dev(pv))) {log_error("Failed to wipe existing label on %s", pv_name);return 0;}if (zero) {log_verbose("Zeroing start of device %s", pv_name);if (!dev_open_quiet(dev)) {log_error("%s not opened: device not zeroed", pv_name);return 0;}if (!dev_set(dev, UINT64_C(0), (size_t) 2048, 0)) {log_error("%s not wiped: aborting", pv_name);if (!dev_close(dev))stack;return 0;}if (!dev_close(dev))stack;}log_error("Writing physical volume data to disk \"%s\"",pv_name);if (!(pv_write(cmd, pv, 1))) { // 很明显，这个命令就是写磁盘用的，详见代码5 log_error("Failed to write physical volume \"%s\"", pv_name);}log_print("Physical volume \"%s\" successfully created", pv_name);return 1;}1.5. p v_write/** 代码5* 调用pv->fmt->ops->pv_write函数* 代码3中，第一句就是：const struct format_type *fmt = cmd->fmt;之后pv->fmt = fmt; * 所以找pv_write函数，需从cmd结构体下手* 另外有个蛋疼的名词：orphan，词典解释：孤儿。