lvm代码分析.doc

lvm代码分析其实挺不敢在csdn写blog的，特别是技术的东东，万一被高手路过，看到自己如此搓人在这造次，岂不是贻笑大方，不过发现这里写文章代码块很好用，用来做代码阅读的笔记挺好的。偷偷留痕，咔咔。在Linux安装完lvm2的工具集后，便可以使用pvcreate，lvcreate，pvscan等命令，其实这些命令都是lvm指出来的链接（害得偶曾经郁闷地找这些命令的main，!=.=）在lvm.c中，入口函数main很简单，调用lvm2_main函数。int main(int argc, char *argv) return lvm2_main(argc, argv, 0);分析int lvm2_main(int argc, char *argv, unsigned is_static) char *base; int ret, alias = 0; struct cmd_context *cmd;这里有个变态的结构cmd_context，发现Linux下很多结构都很变态，也许是自己底子太浅，加上以前都没有阅读过太多代码的缘故。/* FIXME Split into tool & library contexts */* command-instance-related variables needed by library */struct cmd_context struct dm_pool *libmem; /* For permanent config data */ struct dm_pool *mem; /* Transient: Cleared between each command */ const struct format_type *fmt; /* Current format to use by default */ struct format_type *fmt_backup; /* Format to use for backups */ struct list formats; /* Available formats */ struct list segtypes; /* Available segment types */ const char *hostname; const char *kernel_vsn; char *cmd_line; struct command *command; struct arg *args; char *argv; unsigned is_static; /* Static binary? */ unsigned is_long_lived; /* Optimises persistent_filter handling */ struct dev_filter *filter; int dump_filter; /* Dump filter when exiting? */ 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; char sys_dirPATH_MAX; char dev_dirPATH_MAX; char proc_dirPATH_MAX;一个变态的结构引出了几个更变态的结构，已然疯掉，libmen和men是通过dm的lib函数生成的内存池，format_type结构中的format_handle指向相应操作的函数指针，不同的format_type对应的操作函数不一样。struct format_type struct list list; struct cmd_context *cmd; struct format_handler *ops; struct labeller *labeller; const char *name; const char *alias; const char *orphan_vg_name; uint32_t features; void *library; void *private;还有一个command的结构，定义如下：struct command const char *name; const char *help; int min_args; int max_args; command_fn fn;继续分析lvm2_main： _close_stray_fds(); base = last_path_component(argv0); while (*base = /) base+; if (strcmp(base, lvm) & strcmp(base, lvm.static) & strcmp(base, initrd-lvm) alias = 1; if (is_static & strcmp(base, lvm.static) & path_exists(LVM_SHARED_PATH) & !getenv(LVM_DID_EXEC) setenv(LVM_DID_EXEC, base, 1); execvp(LVM_SHARED_PATH, argv); unsetenv(LVM_DID_EXEC); 第1行的函数_close_stray_fds()，没看懂，不过貌似和主干数据流没有多大的影响，暂且不管。希望以后多回头几次能读懂。咔咔。接下来的last_path_component(argv0)是将输入的命令进行一些处理，最后得到命令名，下面的两个if是判断做一些相关处理。就pvcreate /dev/sda0而言，两个if都没有执行。继续往下： if (!(cmd = init_lvm(is_static) return -1;此处调用init_lvm(is_static)，is_static=0struct cmd_context *init_lvm(unsigned is_static) struct cmd_context *cmd; _cmdline.the_args = &_the_args0; if (!(cmd = create_toolcontext(_cmdline.the_args, is_static, 0) return_NULL; _init_rand(); _apply_settings(cmd); return cmd;此处的_cmdline是一个静态变量static struct cmdline_context _cmdline;而这个_the_arg0的赋值也着实让我见识到啥是c语言高级编程，把我最后一点自信给毁了。/* * Table of valid switches */static struct arg _the_argsARG_COUNT + 1 = #define arg(a, b, c, d, e) b, , - c, d, e, 0, NULL, 0, 0, INT64_C(0), UINT64_C(0), SIGN_NONE, PERCENT_NONE, NULL,#include args.h#undef arg;在代码中，我始终没找到ARG_COUNT这个变量的定义，可能是se的问题吧。arg.h:/* * Put all long args that dont have a * corresponding short option first . */* *INDENT-OFF* */arg(version_ARG, 0, version, NULL, 0)arg(quiet_ARG, 0, quiet, NULL, 0)arg(physicalvolumesize_ARG, 0, setphysicalvolumesize, size_mb_arg, 0)arg(ignorelockingfailure_ARG, 0, ignorelockingfailure, NULL, 0)arg(nolocking_ARG, 0, nolocking, NULL, 0)arg(metadatacopies_ARG, 0, metadatacopies, int_arg, 0)arg(metadatasize_ARG, 0, metadatasize, size_mb_arg, 0)arg(restorefile_ARG, 0, restorefile, string_arg, 0)arg(labelsector_ARG, 0, labelsector, int_arg, 0)arg(driverloaded_ARG, 0, driverloaded, yes_no_arg, 0)arg(aligned_ARG, 0, aligned, NULL, 0)arg(unbuffered_ARG, 0, unbuffered, NULL, 0)arg(noheadings_ARG, 0, noheadings, NULL, 0)arg(segments_ARG, 0, segments, NULL, 0)arg(units_ARG, 0, units, string_arg, 0)arg(nosuffix_ARG, 0, nosuffix, NULL, 0)arg(removemissing_ARG, 0, removemissing, NULL, 0)arg(abort_ARG, 0, abort, NULL, 0)arg(addtag_ARG, 0, addtag, tag_arg, 0)arg(deltag_ARG, 0, deltag, tag_arg, 0)arg(refresh_ARG, 0, refresh, NULL, 0)arg(mknodes_ARG, 0, mknodes, NULL, 0)arg(minor_ARG, 0, minor, minor_arg, 0)arg(type_ARG, 0, type, segtype_arg, 0)arg(alloc_ARG, 0, alloc, alloc_arg, 0)arg(separator_ARG, 0, separator, string_arg, 0)arg(mirrorsonly_ARG, 0, mirrorsonly, NULL, 0)arg(nosync_ARG, 0, nosync, NULL, 0)arg(resync_ARG, 0, resync, NULL, 0)arg(corelog_ARG, 0, corelog, NULL, 0)arg(mirrorlog_ARG, 0, mirrorlog, string_arg, 0)arg(monitor_ARG, 0, monitor, yes_no_arg, 0)arg(config_ARG, 0, config, string_arg, 0)arg(trustcache_ARG, 0, trustcache, NULL, 0)arg(ignoremonitoring_ARG, 0, ignoremonitoring, NULL, 0)arg(nameprefixes_ARG, 0, nameprefixes, NULL, 0)arg(unquoted_ARG, 0, unquoted, NULL, 0)arg(rows_ARG, 0, rows, NULL, 0)/* Allow some variations */arg(resizable_ARG, 0, resizable, yes_no_arg, 0)arg(allocation_ARG, 0, allocation, yes_no_arg, 0)/* * . and now the short args. */arg(available_ARG, a, available, yes_no_excl_arg, 0)arg(all_ARG, a, all, NULL, 0)arg(autobackup_ARG, A, autobackup, yes_no_arg, 0)arg(activevolumegroups_ARG, A, activevolumegroups, NULL, 0)arg(background_ARG, b, background, NULL, 0)arg(blockdevice_ARG, b, blockdevice, NULL, 0)arg(chunksize_ARG, c, chunksize, size_kb_arg, 0)arg(clustered_ARG, c, clustered, yes_no_arg, 0)arg(colon_ARG, c, colon, NULL, 0)arg(columns_ARG, C, columns, NULL, 0)arg(contiguous_ARG, C, contiguous, yes_no_arg, 0)arg(debug_ARG, d, debug, NULL, ARG_REPEATABLE)arg(disk_ARG, D, disk, NULL, 0)arg(exported_ARG, e, exported, NULL, 0)arg(physicalextent_ARG, E, physicalextent, NULL, 0)arg(file_ARG, f, file, string_arg, 0)arg(force_ARG, f, force, NULL, ARG_REPEATABLE)arg(full_ARG, f, full, NULL, 0)arg(help_ARG, h, help, NULL, 0)arg(help2_ARG, ?, , NULL, 0)arg(stripesize_ARG, I, stripesize, size_kb_arg, 0)arg(stripes_ARG, i, stripes, int_arg, 0)arg(interval_ARG, i, interval, int_arg, 0)arg(iop_version_ARG, i, iop_version, NULL, 0)arg(logicalvolume_ARG, l, logicalvolume, int_arg, 0)arg(maxlogicalvolumes_ARG, l, maxlogicalvolumes, int_arg, 0)arg(extents_ARG, l, extents, int_arg_with_sign_and_percent, 0)arg(lvmpartition_ARG, l, lvmpartition, NULL, 0)arg(list_ARG, l, list, NULL, 0)arg(size_ARG, L, size, size_mb_arg, 0)arg(logicalextent_ARG, L, logicalextent, int_arg_with_sign, 0)arg(persistent_ARG, M, persistent, yes_no_arg, 0)arg(major_ARG, j, major, major_arg, 0)arg(mirrors_ARG, m, mirrors, int_arg_with_sign, 0)arg(metadatatype_ARG, M, metadatatype, metadatatype_arg, 0)arg(maps_ARG, m, maps, NULL, 0)arg(name_ARG, n, name, string_arg, 0)arg(oldpath_ARG, n, oldpath, NULL, 0)arg(nofsck_ARG, n, nofsck, NULL, 0)arg(novolumegroup_ARG, n, novolumegroup, NULL, 0)arg(options_ARG, o, options, string_arg, 0)arg(sort_ARG, O, sort, string_arg, 0)arg(permission_ARG, p, permission, permission_arg, 0)arg(maxphysicalvolumes_ARG, p, maxphysicalvolumes, int_arg, 0)arg(partial_ARG, P, partial, NULL, 0)arg(physicalvolume_ARG, P, physicalvolume, NULL, 0)arg(readahead_ARG, r, readahead, readahead_arg, 0)arg(resizefs_ARG, r, resizefs, NULL, 0)arg(reset_ARG, R, reset, NULL, 0)arg(regionsize_ARG, R, regionsize, size_mb_arg, 0)arg(physicalextentsize_ARG, s, physicalextentsize, size_mb_arg, 0)arg(stdin_ARG, s, stdin, NULL, 0)arg(snapshot_ARG, s, snapshot, NULL, 0)arg(short_ARG, s, short, NULL, 0)arg(test_ARG, t, test, NULL, 0)arg(uuid_ARG, u, uuid, NULL, 0)arg(uuidstr_ARG, u, uuid, string_arg, 0)arg(uuidlist_ARG, U, uuidlist, NULL, 0)arg(verbose_ARG, v, verbose, NULL, ARG_REPEATABLE)arg(volumegroup_ARG, V, volumegroup, NULL, 0)arg(allocatable_ARG, x, allocatable, yes_no_arg, 0)arg(resizeable_ARG, x, resizeable, yes_no_arg, 0)arg(yes_ARG, y, yes, NULL, 0)arg(zero_ARG, Z, zero, yes_no_arg, 0)/* this should always be last */arg(ARG_COUNT, -, , NULL, 0)/* *INDENT-ON* */这个数组的初始化太有个性了。接着讲init_lvm:struct cmd_context *init_lvm(unsigned is_static) struct cmd_context *cmd; _cmdline.the_args = &_the_args0; if (!(cmd = create_toolcontext(_cmdline.the_args, is_static, 0) return_NULL; _init_rand(); _apply_settings(cmd); return cmd;将_the_args赋予_cmdline.the_args后，调用create_toolcontext,在该函数中，前面的语句：#ifdef M_MMAP_MAX mallopt(M_MMAP_MAX, 0);#endif if (!setlocale(LC_ALL, ) log_very_verbose(setlocale failed);#ifdef INTL_PACKAGE bindtextdomain(INTL_PACKAGE, LOCALEDIR);#endif init_syslog(DEFAULT_LOG_FACILITY);暂且不管，看似一些log相关的东西，接下来的if (!(cmd = dm_malloc(sizeof(*cmd) log_error(Failed to allocate command context); return NULL; memset(cmd, 0, sizeof(*cmd); cmd-args = the_args; cmd-is_static = is_static; cmd-is_long_lived = is_long_lived; cmd-hosttags = 0; list_init(&cmd-formats); list_init(&cmd-segtypes); list_init(&cmd-tags); list_init(&cmd-config_files); strcpy(cmd-sys_dir, DEFAULT_SYS_DIR); if (!_get_env_vars(cmd) goto error; /* Create system directory if it doesnt already exist */ if (*cmd-sys_dir & !dm_create_dir(cmd-sys_dir) log_error(Failed to create LVM2 system dir for metadata backups, config files and internal cache.); log_error(Set environment variable LVM_SYSTEM_DIR to alternative location or empty string.); goto error; if (!(cmd-libmem = dm_pool_create(library, 4 * 1024) log_error(Library memory pool creation failed); goto error; if (!_init_lvm_conf(cmd) goto error; _init_logging(cmd); if (!_init_hostname(cmd) goto error; if (!_init_tags(cmd, cmd-cft) goto error; if (!_init_tag_configs(cmd) goto error; if (!_merge_config_files(cmd) goto error; if (!_process_config(cmd) goto error; if (!_init_dev_cache(cmd) goto error; if (!_init_filters(cmd, 1) goto error; if (!(cmd-mem = dm_pool_create(command, 4 * 1024) log_error(Command memory pool creation failed); goto error; memlock_init(cmd); if (!_init_formats(cmd) goto error; if (!init_lvmcache_orphans(cmd) goto error; if (!_init_segtypes(cmd) goto error; if (!_init_backup(cmd) goto error; cmd-default_settings.cache_vgmetadata = 1; cmd-current_settings = cmd-default_settings; cmd-config_valid = 1; return cmd; error: dm_free(cmd); return NULL;向dm申请cmd内存，然后对cmd进行初始化。init_lvm中的 _init_rand(); _apply_settings(cmd);先暂且不管吧。lvm返回后，在lvm2_main里执行： cmd-argv = argv; lvm_register_commands();lvm_register_commands()又是一个似曾相识的构架：void lvm_register_commands(void)#define xx(a, b, c, d.) _register_command(# a, a, b, c, # d, driverloaded_ARG, debug_ARG, help_ARG, help2_ARG, version_ARG, verbose_ARG, quiet_ARG, config_ARG, -1);#include commands.h#undef xx在commands.h中，xx了好多种命令：xx(dumpconfig, Dump active configuration, 0, dumpconfig t-f|-file filename n ConfigurationVariable.n, file_ARG)xx(formats, List available metadata formats, 0, formatsn)xx(help, Display help for commands, 0, help n)/*xx(lvactivate, Activate logical volume on given partition(s), lvactivate t-d|-debugn t-h|-helpn t-v|-verbosen Logical Volume(s)n)*/xx(lvchange, Change the attributes of logical volume(s), CACHE_VGMETADATA, lvchangen t-A|-autobackup y|nn t-a|-available e|ly|nn t-addtag Tagn t-alloc AllocationPolicyn t-C|-contiguous y|nn t-d|-debugn t-deltag Tagn t-f|-forcen t-h|-helpn t-ignorelockingfailuren t-ignoremonitoringn t-monitor y|nn t-M|-persistent y|n -major major -minor minorn t-P|-partial n t-p|-permission r|rwn t-r|-readahead ReadAheadSectors|auto|nonen t-refreshn t-resyncn t-t|-testn t-v|-verbosen t-y|-yesn t-version n tLogicalVolumePath LogicalVolumePath.n, alloc_ARG, autobackup_ARG, available_ARG, contiguous_ARG, force_ARG, ignorelockingfailure_ARG, ignoremonitoring_ARG, major_ARG, minor_ARG, monitor_ARG, partial_ARG, permission_ARG, persistent_ARG, readahead_ARG, resync_ARG, refresh_ARG, addtag_ARG, deltag_ARG, test_ARG, yes_ARG)xx(lvconvert, Change logical volume layout, 0, lvconvert -m|-mirrors Mirrors -mirrorlog disk|core|-corelogn t-R|-regionsize MirrorLogRegionSizen t-alloc AllocationPolicyn t-b|-backgroundn t-d|-debugn t-h|-?|-helpn t-i|-interval secondsn t-v|-verbosen t-version n tLogicalVolumePath PhysicalVolumePath.nn lvconvert -s|-snapshotn t-c|-chunksizen t-d|-debugn t-h|-?|-helpn t-v|-verbosen t-Z|-zero y|nn t-version n tOriginalLogicalVolumePath SnapshotLogicalVolumePathn, alloc_ARG, background_ARG, chunksize_ARG, corelog_ARG, interval_ARG, mirrorlog_ARG, mirrors_ARG, regionsize_ARG, snapshot_ARG, test_ARG, zero_ARG)xx(lvcreate, Create a logical volume, 0, lvcreate n t-A|-autobackup y|nn t-addtag Tagn t-alloc AllocationPolicyn t-C|-contiguous y|nn t-d|-debugn t-h|-?|-helpn t-i|-stripes Stripes -I|-stripesize StripeSizen t-l|-extents LogicalExtentsNumber |n t -L|-size LogicalVolumeSizekKmMgGtTpPeEn t-M|-persistent y|n -major major -minor minorn t-m|-mirrors Mirrors -nosync -mirrorlog disk|core|-corelogn t-n|-name LogicalVolumeNamen t-p|-permission r|rwn t-r|-readahead ReadAheadSectors|auto|nonen t-R|-regionsize MirrorLogRegionSizen t-t|-testn t-type VolumeTypen t-v|-verbosen t-Z|-zero y|nn t-versionn tVolumeGroupName PhysicalVolumePath.nn lvcreate -s|-snapshotn t-c|-chunksizen t-A|-autobackup y|nn t-addtag Tagn t-alloc AllocationPolicyn t-C|-contiguous y|nn t-d|-debugn t-h|-?|-helpn t-i|-stripes Stripes -I|-stripesize StripeSizen t-l|-extents LogicalExtentsNumber%VG|LV|PVS|FREE |n t -L|-size LogicalVolumeSizekKmMgGtTpPeEn t-M|-persistent y|n -major major -minor minorn t-n|-name LogicalVolumeNamen t-p|-permission r|rwn t-r|-readahead ReadAheadSectors|auto|nonen t-t|-testn t-v|-verbosen t-versionn tOriginalLogicalVolumePath PhysicalVolumePath.nn, addtag_ARG, alloc_ARG, autobackup_ARG, chunksize_ARG, contiguous_ARG, corelog_ARG, extents_ARG, major_ARG, minor_ARG, mirrorlog_ARG, mirrors_ARG, name_ARG, nosync_ARG, permission_ARG, persistent_ARG, readahead_ARG, regionsize_ARG, size_ARG, snapshot_ARG, stripes_ARG, stripesize_ARG, test_ARG, type_ARG, zero_ARG)xx(lvdisplay, Display information about a logical volume, 0, lvdisplayn t-a|-alln t-c|-colonn t-d|-debugn t-h|-helpn t-ignorelockingfailuren t-m|-mapsn t-nosuffixn t-P|-partial n t-units hsbkmgtHKMGTn t-v|-verbosen t-version n tLogicalVolumePath LogicalVolumePath.n n lvdisplay