命令参数定义：

$ cat tools/command.h
...xx(lvextend,"Add space to a logical volume",0,"lvextend\n""\t[-A|--autobackup y|n]\n""\t[--alloc AllocationPolicy]\n""\t[--commandprofile ProfileName]\n""\t[-d|--debug]\n""\t[-f|--force]\n""\t[-h|--help]\n""\t[-i|--stripes Stripes [-I|--stripesize StripeSize]]\n""\t{-l|--extents [+]LogicalExtentsNumber[%{VG|LV|PVS|FREE|ORIGIN}] |\n""\t -L|--size [+]LogicalVolumeSize[bBsSkKmMgGtTpPeE]}\n""\t --poolmetadatasize [+]MetadataVolumeSize[bBsSkKmMgG]}\n""\t[-m|--mirrors Mirrors]\n""\t[--nosync]\n""\t[--use-policies]\n""\t[-n|--nofsck]\n""\t[--noudevsync]\n""\t[--reportformat {basic|json}]\n""\t[-r|--resizefs]\n""\t[-t|--test]\n""\t[--type VolumeType]\n""\t[-v|--verbose]\n""\t[--version]\n""\tLogicalVolume[Path] [ PhysicalVolumePath... ]\n",alloc_ARG, autobackup_ARG, extents_ARG, force_ARG, mirrors_ARG,nofsck_ARG, nosync_ARG, noudevsync_ARG, poolmetadatasize_ARG,reportformat_ARG, resizefs_ARG, size_ARG, stripes_ARG, stripesize_ARG,test_ARG, type_ARG, usepolicies_ARG)...

命令入口，调用lvresize：

$ cat tools/lvextend.c
...#include "tools.h"int lvextend(struct cmd_context *cmd, int argc, char **argv)
{return lvresize(cmd, argc, argv);
}...

lvresize函数入口：

$ cat tools/lvresize.c
...int lvresize(struct cmd_context *cmd, int argc, char **argv)
{struct processing_handle *handle;struct lvresize_params lp = { 0 };int ret;if (!_lvresize_params(cmd, argc, argv, &lp)) {stack;return EINVALID_CMD_LINE;}if (!(handle = init_processing_handle(cmd, NULL))) {log_error("Failed to initialize processing handle.");return ECMD_FAILED;}handle->custom_handle = &lp;ret = process_each_vg(cmd, 0, NULL, lp.vg_name, NULL, READ_FOR_UPDATE, 0, handle,&_lvresize_single);destroy_processing_handle(cmd, handle);return ret;
}...

...static int _lvresize_single(struct cmd_context *cmd, const char *vg_name,struct volume_group *vg, struct processing_handle *handle)
{struct lvresize_params *lp = (struct lvresize_params *) handle->custom_handle;struct dm_list *pvh;struct logical_volume *lv;int ret = ECMD_FAILED;/* Does LV exist? */if (!(lv = find_lv(vg, lp->lv_name))) {log_error("Logical volume %s not found in volume group %s.",lp->lv_name, vg->name);goto out;}if (!(pvh = lp->argc ? create_pv_list(cmd->mem, vg, lp->argc, lp->argv, 1) : &vg->pvs))goto_out;if (!lv_resize(lv, lp, pvh))goto_out;ret = ECMD_PROCESSED;
out:return ret;
}...

lv_resize关键部分：

$ cat lib/metadata/lv_mainp.c
...int lv_resize(struct logical_volume *lv,struct lvresize_params *lp,struct dm_list *pvh)
{struct volume_group *vg = lv->vg;struct cmd_context *cmd = vg->cmd;struct logical_volume *lock_lv = (struct logical_volume*) lv_lock_holder(lv);struct logical_volume *aux_lv = NULL; /* Note: aux_lv never resizes fs */struct lvresize_params aux_lp;int activated = 0;int ret = 0;if (!_lvresize_check(lv, lp))return_0;if (lp->use_policies) {lp->extents = 0;lp->sign = SIGN_PLUS;lp->percent = PERCENT_LV;aux_lp = *lp;if (!_lvresize_adjust_policy(lv, &lp->extents, &aux_lp.extents))return_0;if (!lp->extents) {if (!aux_lp.extents)return 1;  /* Nothing to do *//* Resize thin-pool metadata as mainlv */lv = first_seg(lv)->metadata_lv; /* metadata LV */lp->extents = aux_lp.extents;} else if (aux_lp.extents) {/* Also resize thin-pool metadata */aux_lv = _lvresize_setup_aux(first_seg(lv)->metadata_lv, &aux_lp);}} else if (lp->poolmetadata_size) {if (!lp->extents && !lp->size) {/* When only --poolmetadatasize give and not --size* swith directly to resize metadata LV */lv = first_seg(lv)->metadata_lv;lp->size = lp->poolmetadata_size;lp->sign = lp->poolmetadata_sign;} else {aux_lp = *lp;aux_lv = _lvresize_setup_aux(first_seg(lv)->metadata_lv, &aux_lp);aux_lp.size = lp->poolmetadata_size;aux_lp.sign = lp->poolmetadata_sign;}}if (aux_lv && !_lvresize_prepare(&aux_lv, &aux_lp, pvh))return_0;if (!_lvresize_prepare(&lv, lp, pvh))return_0;if (lv_is_thin_pool(lock_lv) &&  /* Lock holder is thin-pool */!lv_is_active(lock_lv)) {if (!activation()) {log_error("Cannot resize %s without using ""device-mapper kernel driver.",display_lvname(lock_lv));return 0;}/** Active 'hidden' -tpool can be waiting for resize, but the* pool LV itself might be inactive.* Here plain suspend/resume would not work.* So active temporarily pool LV (with on disk metadata)* then use suspend and resume and deactivate pool LV,* instead of searching for an active thin volume.*/if (!activate_lv_excl(cmd, lock_lv)) {log_error("Failed to activate %s.", display_lvname(lock_lv));return 0;}activated = 1;}/** If the LV is locked from activation, this lock call is a no-op.* Otherwise, this acquires a transient lock on the lv (not PERSISTENT).*/if (!lockd_lv(cmd, lock_lv, "ex", 0))return_0;if (aux_lv) {if (!_lvresize_volume(aux_lv, &aux_lp, pvh))goto_bad;/* store vg on disk(s) */if (!lv_update_and_reload(lock_lv))goto_bad;}if (!_lvresize_volume(lv, lp, pvh))goto_bad;/* store vg on disk(s) */if (!lv_update_and_reload(lock_lv))goto_bad;if (lv_is_cow_covering_origin(lv))if (!monitor_dev_for_events(cmd, lv, 0, 0))stack;if (lv_is_thin_pool(lock_lv)) {/* Update lvm pool metadata (drop messages). */if (!update_pool_lv(lock_lv, 0))goto_bad;backup(vg);}log_print_unless_silent("Logical volume %s successfully resized.",display_lvname(lv));if (lp->resizefs && (lp->resize == LV_EXTEND) &&!_fsadm_cmd(FSADM_CMD_RESIZE, lv, lp->extents, lp->force, NULL))return_0;ret = 1;
bad:if (activated && !deactivate_lv(cmd, lock_lv)) {log_error("Problem deactivating %s.", display_lvname(lock_lv));ret = 0;}return ret;
}...

$ cat lib/locking/file_locking.c
...static int _file_lock_resource(struct cmd_context *cmd, const char *resource,uint32_t flags, const struct logical_volume *lv)
{...case LCK_UNLOCK:log_very_verbose("Unlocking LV %s%s%s", resource, origin_only ? " without snapshots" : "", revert ? " (reverting)" : "");if (!lv_resume_if_active(cmd, resource, origin_only, 0, revert, lv_committed(lv)))return 0;break;...case LCK_WRITE:log_very_verbose("Locking LV %s (W)%s", resource, origin_only ? " without snapshots" : "");if (!lv_suspend_if_active(cmd, resource, origin_only, 0, lv_committed(lv), lv))return 0;break;...return 1;
}...

$ cat lib/active/active.c
.../** In a cluster, set exclusive to indicate that only one node is using the* device.  Any preloaded tables may then use non-clustered targets.** Returns success if the device is not active*/
int lv_suspend_if_active(struct cmd_context *cmd, const char *lvid_s, unsigned origin_only, unsigned exclusive,const struct logical_volume *lv, const struct logical_volume *lv_pre)
{struct lv_activate_opts laopts = {.origin_only = origin_only,.exclusive = exclusive};return _lv_suspend(cmd, lvid_s, &laopts, 0, lv, lv_pre);
}.../** In a cluster, set exclusive to indicate that only one node is using the* device.  Any tables loaded may then use non-clustered targets.** @origin_only* @exclusive   This parameter only has an affect in cluster-context.*              It forces local target type to be used (instead of*              cluster-aware type).* Returns success if the device is not active*/
int lv_resume_if_active(struct cmd_context *cmd, const char *lvid_s,unsigned origin_only, unsigned exclusive,unsigned revert, const struct logical_volume *lv)
{struct lv_activate_opts laopts = {.origin_only = origin_only,.exclusive = exclusive,.revert = revert};return _lv_resume(cmd, lvid_s, &laopts, 0, lv);
}...