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BeeGFS源码分析2-客户端概要分析

日期:2019-07-09点击:269

BeeGFS的客户端是由一个内核模块和两个系统服务组成的,这里我们主要分析内核模块。内核模块主要实现了一个Linux的文件系统,因此注册了一个文件系统类型。因为BeeGFS的目录树解析,是在父目录DEntry里找子目录或文件DEntry,逐级迭代完成的,因此在Mount文件系统时,需要从管理节点获取根元数据节点的ID,然后再向根元数据节点查询根目录的DEntry的信息,为后续的目录解析打下基础。

注册文件系统类型

init_fhgfs_client

  • 内核模块初始化:
// fhgfs_client_module\source\program\Main.c #define BEEGFS_LICENSE "GPL v2" static int __init init_fhgfs_client(void) { #define fail_to(target, msg) \ do { \ printk_fhgfs(KERN_WARNING, msg "\n"); \ goto target; \ } while (0) if (!beegfs_fault_inject_init() ) fail_to(fail_fault, "could not register fault-injection debugfs dentry"); if (!beegfs_native_init() ) fail_to(fail_native, "could not allocate emergency pools"); if (!FhgfsOpsCommKit_initEmergencyPools() ) fail_to(fail_commkitpools, "could not allocate emergency pools"); if (!SocketTk_initOnce() ) fail_to(fail_socket, "SocketTk initialization failed"); if (!FhgfsOps_initInodeCache() ) fail_to(fail_inode, "Inode cache initialization failed"); if (!RWPagesWork_initworkQueue() ) fail_to(fail_rwpages, "Page work queue registration failed"); if (!FhgfsOpsRemoting_initMsgBufCache() ) fail_to(fail_msgbuf, "Message cache initialization failed"); if (!FhgfsOpsPages_initPageListVecCache() ) fail_to(fail_pagelists, "PageVec cache initialization failed"); if (FhgfsOps_registerFilesystem() ) fail_to(fail_register, "File system registration failed"); ProcFs_createGeneralDir(); printk_fhgfs(KERN_INFO, "File system registered. Type: %s. Version: %s\n", BEEGFS_MODULE_NAME_STR, App_getVersionStr() ); return 0; fail_register: FhgfsOpsPages_destroyPageListVecCache(); fail_pagelists: FhgfsOpsRemoting_destroyMsgBufCache(); fail_msgbuf: RWPagesWork_destroyWorkQueue(); fail_rwpages: FhgfsOps_destroyInodeCache(); fail_inode: SocketTk_uninitOnce(); fail_socket: FhgfsOpsCommKit_releaseEmergencyPools(); fail_commkitpools: beegfs_native_release(); fail_native: beegfs_fault_inject_release(); fail_fault: return -EPERM; } static void __exit exit_fhgfs_client(void) { ProcFs_removeGeneralDir(); BUG_ON(FhgfsOps_unregisterFilesystem() ); FhgfsOpsPages_destroyPageListVecCache(); FhgfsOpsRemoting_destroyMsgBufCache(); RWPagesWork_destroyWorkQueue(); FhgfsOps_destroyInodeCache(); SocketTk_uninitOnce(); FhgfsOpsCommKit_releaseEmergencyPools(); beegfs_native_release(); beegfs_fault_inject_release(); printk_fhgfs(KERN_INFO, "BeeGFS client unloaded.\n"); } module_init(init_fhgfs_client) module_exit(exit_fhgfs_client) MODULE_LICENSE(BEEGFS_LICENSE); MODULE_DESCRIPTION("BeeGFS parallel file system client (http://www.beegfs.com)"); MODULE_AUTHOR("Fraunhofer ITWM, CC-HPC"); 

FhgfsOps_registerFilesystem

  • 初始化时,向内核注册BeeGFS文件系统类型:
// fhgfs_client_module\source\filesystem\FhgfsOpsSuper.c static struct file_system_type fhgfs_fs_type = { .name = BEEGFS_MODULE_NAME_STR, .owner = THIS_MODULE, .kill_sb = FhgfsOps_killSB, //.fs_flags = FS_BINARY_MOUNTDATA, // not required currently #ifdef KERNEL_HAS_GET_SB_NODEV .get_sb = FhgfsOps_getSB, #else .mount = FhgfsOps_mount, // basically the same thing as get_sb before #endif }; int FhgfsOps_registerFilesystem(void) { return register_filesystem(&fhgfs_fs_type); } 

挂载文件系统

FhgfsOps_mount

  • Mount文件系统时,间接调用FhgfsOps_fillSuper来填充文件系统超级块。
// fhgfs_client_module\source\filesystem\FhgfsOps_versions.c #ifdef KERNEL_HAS_GET_SB_NODEV int FhgfsOps_getSB(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { return get_sb_nodev(fs_type, flags, data, FhgfsOps_fillSuper, mnt); } #else /* kernel 2.6.39 switched from get_sb() to mount(), which provides similar functionality from our point of view. */ struct dentry* FhgfsOps_mount(struct file_system_type *fs_type, int flags, const char *dev_name, void *data) { return mount_nodev(fs_type, flags, data, FhgfsOps_fillSuper); } #endif // LINUX_VERSION_CODE 

FhgfsOps_fillSuper

  • 初始化文件系统实例的超级块,并初始化根目录的inode,此时ID只是简单的初始化为0,后面会更新成真正的ID
// fhgfs_client_module\source\filesystem\FhgfsOpsSuper.c /** * Fill the file system superblock (vfs object) */ int FhgfsOps_fillSuper(struct super_block* sb, void* rawMountOptions, int silent) { App* app = NULL; Config* cfg = NULL; struct inode* rootInode; struct dentry* rootDentry; struct kstat kstat; EntryInfo entryInfo; FhgfsIsizeHints iSizeHints; // init per-mount app object if(__FhgfsOps_constructFsInfo(sb, rawMountOptions) ) return -ECANCELED; app = FhgfsOps_getApp(sb); cfg = App_getConfig(app); // set up super block data sb->s_maxbytes = MAX_LFS_FILESIZE; sb->s_blocksize = PAGE_SIZE; sb->s_blocksize_bits = PAGE_SHIFT; sb->s_magic = BEEGFS_MAGIC; sb->s_op = &fhgfs_super_ops; sb->s_time_gran = 1000000000; // granularity of c/m/atime in ns sb->s_flags |= MS_NODIRATIME; if (Config_getSysXAttrsEnabled(cfg ) ) sb->s_xattr = fhgfs_xattr_handlers_noacl; // handle only user xattrs #ifdef KERNEL_HAS_POSIX_GET_ACL if (Config_getSysACLsEnabled(cfg) ) { sb->s_xattr = fhgfs_xattr_handlers; // replace with acl-capable xattr handlers sb->s_flags |= MS_POSIXACL; } #endif // KERNEL_HAS_POSIX_GET_ACL /* MS_ACTIVE is rather important as it marks the super block being successfully initialized and * allows the vfs to keep important inodes in the cache. However, it seems it is already * initialized in vfs generic mount functions. sb->s_flags |= MS_ACTIVE; // used in iput_final() */ // NFS kernel export is probably not worth the backport efforts for kernels before 2.6.29 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,29) sb->s_export_op = &fhgfs_export_ops; #endif #if defined(KERNEL_HAS_SB_BDI) sb->s_bdi = FhgfsOps_getBdi(sb); #endif // init root inode memset(&kstat, 0, sizeof(struct kstat) ); kstat.ino = BEEGFS_INODE_ROOT_INO; kstat.mode = S_IFDIR | 0777; // allow access for everyone kstat.atime = kstat.mtime = kstat.ctime = current_fs_time(sb); kstat.uid = FhgfsCommon_getCurrentKernelUserID(); kstat.gid = FhgfsCommon_getCurrentKernelGroupID(); kstat.blksize = Config_getTuneInodeBlockSize(cfg); kstat.nlink = 1; // root entryInfo is always updated when someone asks for it (so we just set dummy values here) EntryInfo_init(&entryInfo, NodeOrGroup_fromGroup(0), StringTk_strDup(""), StringTk_strDup(""), StringTk_strDup(""), DirEntryType_DIRECTORY, 0); rootInode = __FhgfsOps_newInode(sb, &kstat, 0, &entryInfo, &iSizeHints); if(!rootInode || IS_ERR(rootInode) ) { __FhgfsOps_destructFsInfo(sb); return IS_ERR(rootInode) ? PTR_ERR(rootInode) : -ENOMEM; } rootDentry = d_make_root(rootInode); if(!rootDentry) { __FhgfsOps_destructFsInfo(sb); return -ENOMEM; } #ifdef KERNEL_HAS_S_D_OP // linux 2.6.38 switched from individual per-dentry to defaul superblock d_ops. /* note: Only set default dentry operations here, as we don't want those OPs set for the root * dentry. In fact, setting as before would only slow down everything a bit, due to * useless revalidation of our root dentry. */ sb->s_d_op = &fhgfs_dentry_ops; #endif // KERNEL_HAS_S_D_OP rootDentry->d_time = jiffies; sb->s_root = rootDentry; return 0; } 

初始化文件系统

__FhgfsOps_constructFsInfo

  • 申请内存,构造文件系统基本数据结构:
// fhgfs_client_module\source\filesystem\FhgfsOpsSuper.c /** * Initialize sb->s_fs_info * * @return 0 on success, negative linux error code otherwise */ int __FhgfsOps_constructFsInfo(struct super_block* sb, void* rawMountOptions) { int res; int appRes; App* app; Logger* log; #if defined(KERNEL_HAS_SB_BDI) && !defined(KERNEL_HAS_SUPER_SETUP_BDI_NAME) struct backing_dev_info* bdi; #endif // use kzalloc to also zero the bdi FhgfsSuperBlockInfo* sbInfo = kzalloc(sizeof(FhgfsSuperBlockInfo), GFP_KERNEL); if (!sbInfo) { printk_fhgfs_debug(KERN_INFO, "Failed to allocate memory for FhgfsSuperBlockInfo"); sb->s_fs_info = NULL; return -ENOMEM; } sb->s_fs_info = sbInfo; appRes = __FhgfsOps_initApp(sb, rawMountOptions); if(appRes) { printk_fhgfs_debug(KERN_INFO, "Failed to initialize App object"); res = -EINVAL; goto outFreeSB; } app = FhgfsOps_getApp(sb); log = App_getLogger(app); IGNORE_UNUSED_VARIABLE(log); #if defined(KERNEL_HAS_SB_BDI) #if defined(KERNEL_HAS_SUPER_SETUP_BDI_NAME) && !defined(KERNEL_HAS_BDI_SETUP_AND_REGISTER) { static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); res = super_setup_bdi_name(sb, BEEGFS_MODULE_NAME_STR "-%ld", atomic_long_inc_return(&bdi_seq)); } #else bdi = &sbInfo->bdi; /* NOTE: The kernel expects a fully initialized bdi structure, so at a minimum it has to be * allocated by kzalloc() or memset(bdi, 0, sizeof(*bdi)). * we don't set the congest_* callbacks (like every other filesystem) because those are * intended for dm and md. */ bdi->ra_pages = BEEGFS_DEFAULT_READAHEAD_PAGES; #if defined(KERNEL_HAS_BDI_CAP_MAP_COPY) res = bdi_setup_and_register(bdi, BEEGFS_MODULE_NAME_STR, BDI_CAP_MAP_COPY); #else res = bdi_setup_and_register(bdi, BEEGFS_MODULE_NAME_STR); #endif #endif if (res) { Logger_logFormatted(log, 2, __func__, "Failed to init super-block (bdi) information: %d", res); __FhgfsOps_uninitApp(app); goto outFreeSB; } #endif // set root inode attribs to uninit'ed FhgfsOps_setHasRootEntryInfo(sb, false); FhgfsOps_setIsRootInited(sb, false); printk_fhgfs(KERN_INFO, "BeeGFS mount ready.\n"); return 0; // all ok, res should be 0 here outFreeSB: kfree(sbInfo); sb->s_fs_info = NULL; return res; } 

__FhgfsOps_initApp

  • 解析参数,继续初始化:
// fhgfs_client_module\source\filesystem\FhgfsOpsSuper.c /** * Creates and initializes the per-mount application object. */ int __FhgfsOps_initApp(struct super_block* sb, char* rawMountOptions) { MountConfig* mountConfig; bool parseRes; App* app; int appRes; // create mountConfig (parse from mount options) mountConfig = MountConfig_construct(); parseRes = MountConfig_parseFromRawOptions(mountConfig, rawMountOptions); if(!parseRes) { MountConfig_destruct(mountConfig); return APPCODE_INVALID_CONFIG; } //printk_fhgfs(KERN_INFO, "Initializing App...\n"); // debug in app = FhgfsOps_getApp(sb); App_init(app, mountConfig); appRes = App_run(app); if(appRes != APPCODE_NO_ERROR) { // error occurred => clean up printk_fhgfs_debug(KERN_INFO, "Stopping App...\n"); App_stop(app); printk_fhgfs_debug(KERN_INFO, "Cleaning up...\n"); App_uninit(app); printk_fhgfs_debug(KERN_INFO, "App unitialized.\n"); return appRes; } ProcFs_createEntries(app); return appRes; } 

App_run

  • 初始化客户端基本组件:
// fhgfs_client_module\source\app\App.c int App_run(App* this) { // init data objects & storage if(!__App_initDataObjects(this, this->mountConfig) ) { printk_fhgfs(KERN_WARNING, "Configuration error: Initialization of common objects failed. " "(Log file may provide additional information.)\n"); this->appResult = APPCODE_INVALID_CONFIG; return this->appResult; } if(!__App_initInodeOperations(this) ) { printk_fhgfs(KERN_WARNING, "Initialization of inode operations failed."); this->appResult = APPCODE_INITIALIZATION_ERROR; return this->appResult; } if(!__App_initStorage(this) ) { printk_fhgfs(KERN_WARNING, "Configuration error: Initialization of storage failed\n"); this->appResult = APPCODE_INVALID_CONFIG; return this->appResult; } // init components if(!__App_initComponents(this) ) { printk_fhgfs(KERN_WARNING, "Component initialization error. " "(Log file may provide additional information.)\n"); this->appResult = APPCODE_INITIALIZATION_ERROR; return this->appResult; } __App_logInfos(this); // start components __App_startComponents(this); // Note: We wait some ms for the node downloads here because the kernel would like to // check the properties of the root directory directly after mount. InternodeSyncer_waitForMgmtInit(this->internodeSyncer, 1000); if(!__App_mountServerCheck(this) ) { // mount check failed => cancel mount printk_fhgfs(KERN_WARNING, "Mount sanity check failed. Canceling mount. " "(Log file may provide additional information. Check can be disabled with " "sysMountSanityCheckMS=0 in the config file.)\n"); this->appResult = APPCODE_INITIALIZATION_ERROR; return this->appResult; } // mark: mount succeeded if we got here! return this->appResult; } 

__App_initInodeOperations

  • 初始化inode基本操作,以备后面新建inode时使用:
// fhgfs_client_module\source\app\App.c /** * Initialized the inode_operations structs depending on what features have been enabled in * the config. */ bool __App_initInodeOperations(App* this) { Config* cfg = App_getConfig(this); this->fileInodeOps = os_kzalloc(sizeof(struct inode_operations) ); this->symlinkInodeOps = os_kzalloc(sizeof(struct inode_operations) ); this->dirInodeOps = os_kzalloc(sizeof(struct inode_operations) ); this->specialInodeOps = os_kzalloc(sizeof(struct inode_operations) ); if (!this->fileInodeOps || !this->symlinkInodeOps || !this->dirInodeOps || !this->specialInodeOps) { SAFE_KFREE(this->fileInodeOps); SAFE_KFREE(this->symlinkInodeOps); SAFE_KFREE(this->dirInodeOps); SAFE_KFREE(this->specialInodeOps); return false; } this->fileInodeOps->getattr = FhgfsOps_getattr; this->fileInodeOps->permission = FhgfsOps_permission; this->fileInodeOps->setattr = FhgfsOps_setattr; #ifdef KERNEL_HAS_GENERIC_READLINK this->symlinkInodeOps->readlink = generic_readlink; // default is fine for us currently #endif #ifdef KERNEL_HAS_GET_LINK this->symlinkInodeOps->get_link = FhgfsOps_get_link; #else this->symlinkInodeOps->follow_link = FhgfsOps_follow_link; this->symlinkInodeOps->put_link = FhgfsOps_put_link; #endif this->symlinkInodeOps->getattr = FhgfsOps_getattr; this->symlinkInodeOps->permission = FhgfsOps_permission; this->symlinkInodeOps->setattr = FhgfsOps_setattr; #ifdef KERNEL_HAS_ATOMIC_OPEN #ifdef BEEGFS_ENABLE_ATOMIC_OPEN this->dirInodeOps->atomic_open = FhgfsOps_atomicOpen; #endif // BEEGFS_ENABLE_ATOMIC_OPEN #endif this->dirInodeOps->lookup = FhgfsOps_lookupIntent; this->dirInodeOps->create = FhgfsOps_createIntent; this->dirInodeOps->link = FhgfsOps_link; this->dirInodeOps->unlink = FhgfsOps_unlink; this->dirInodeOps->mknod = FhgfsOps_mknod; this->dirInodeOps->symlink = FhgfsOps_symlink; this->dirInodeOps->mkdir = FhgfsOps_mkdir; this->dirInodeOps->rmdir = FhgfsOps_rmdir; this->dirInodeOps->rename = FhgfsOps_rename; this->dirInodeOps->getattr = FhgfsOps_getattr; this->dirInodeOps->permission = FhgfsOps_permission; this->dirInodeOps->setattr = FhgfsOps_setattr; this->specialInodeOps->setattr = FhgfsOps_setattr; if (Config_getSysXAttrsEnabled(cfg) ) { this->fileInodeOps->listxattr = FhgfsOps_listxattr; this->dirInodeOps->listxattr = FhgfsOps_listxattr; #ifdef KERNEL_HAS_GENERIC_GETXATTR this->fileInodeOps->getxattr = generic_getxattr; this->fileInodeOps->removexattr = FhgfsOps_removexattr; this->fileInodeOps->setxattr = generic_setxattr; this->dirInodeOps->getxattr = generic_getxattr; this->dirInodeOps->removexattr = FhgfsOps_removexattr; this->dirInodeOps->setxattr = generic_setxattr; #endif if (Config_getSysACLsEnabled(cfg) ) { #ifdef KERNEL_HAS_POSIX_GET_ACL this->fileInodeOps->get_acl = FhgfsOps_get_acl; this->dirInodeOps->get_acl = FhgfsOps_get_acl; // Note: symlinks don't have ACLs #ifdef KERNEL_HAS_SET_ACL this->fileInodeOps->set_acl = FhgfsOps_set_acl; this->dirInodeOps->set_acl = FhgfsOps_set_acl; #endif // LINUX_VERSION_CODE #else Logger_logErr(this->logger, "Init inode operations", "ACLs activated in config, but not supported on this kernel version."); return false; #endif // KERNEL_HAS_POSIX_GET_ACL } } return true; } 

创建和初始化Inode

FhgfsOps_fillSuper函数初始化调用。

__FhgfsOps_newInode

  • 创建新的Inode时,会调用此函数,根据父目录的DEntry信息(其中保存有父目录所在的元数据节点ID,以及目录ID),访问相应的元数据节点进行子目录或者文件的操作:
// fhgfs_client_module\source\filesystem\FhgfsOpsInode.h /** * See __FhgfsOps_newInodeWithParentID for details. This is just a wrapper function. */ struct inode* __FhgfsOps_newInode(struct super_block* sb, struct kstat* kstat, dev_t dev, EntryInfo* entryInfo, FhgfsIsizeHints* iSizeHints) { return __FhgfsOps_newInodeWithParentID(sb, kstat, dev, entryInfo, (NumNodeID){0}, iSizeHints); } /** * Creates a new inode, inits it from the kstat, inits the ops (depending on the mode) * and hashes it. * * Note: Make sure everything is set in the kstat _before_ you call this, because we hash * the inode in here (so it can be found and accessed by others when this method returns). * Note: Consider using the _instantiateInode()-wrapper instead of calling this directly for new * files/dirs. * * @param kstat must have a valid .ino (inode number) * @param dev set to 0 if not required (only used for special files) * @param entryInfoPtr contained strings will just be moved to the new inode or free'd in case of an * error (or cached inode), so don't access the given entryInfoPtr anymore after calling this. * @param parentNodeID: usually 0, except for NFS export callers, which needs it to connect dentries * with their parents. By default dentries are connected to their parents, so usually this * is not required (nfs is an exception). * @return NULL if not successful */ struct inode* __FhgfsOps_newInodeWithParentID(struct super_block* sb, struct kstat* kstat, dev_t dev, EntryInfo* entryInfo, NumNodeID parentNodeID, FhgfsIsizeHints* iSizeHints) { App* app = FhgfsOps_getApp(sb); Config* cfg = App_getConfig(app); FhgfsInode* fhgfsInode; FhgfsInodeComparisonInfo comparisonInfo = { .inodeHash = kstat->ino, // pre-set by caller .entryID = entryInfo->entryID, }; // check inode cache for an existing inode with this ID (and get it) or allocate a new one struct inode* inode = iget5_locked(sb, kstat->ino, __FhgfsOps_compareInodeID, __FhgfsOps_initNewInodeDummy, &comparisonInfo); if(unlikely(!inode || IS_ERR(inode) ) ) goto cleanup_entryInfo; // allocation of new inode failed fhgfsInode = BEEGFS_INODE(inode); if( !(inode->i_state & I_NEW) ) { // Found an existing inode, which is possibly actively used. We still need to update it. FhgfsInode_entryInfoWriteLock(fhgfsInode); // LOCK EntryInfo FhgfsInode_updateEntryInfoUnlocked(fhgfsInode, entryInfo); FhgfsInode_entryInfoWriteUnlock(fhgfsInode); // UNLOCK EntryInfo spin_lock(&inode->i_lock); __FhgfsOps_applyStatDataToInodeUnlocked(kstat, iSizeHints, inode); // already locked Time_setToNow(&fhgfsInode->dataCacheTime); spin_unlock(&inode->i_lock); goto outNoCleanUp; // we found a matching existing inode => no init needed } fhgfsInode->parentNodeID = parentNodeID; /* note: new inodes are protected by the I_NEW flag from access by other threads until we * call unlock_new_inode(). */ // init this fresh new inode... // no one can access inode yet => unlocked __FhgfsOps_applyStatDataToInodeUnlocked(kstat, iSizeHints, inode); inode->i_ino = kstat->ino; // pre-set by caller inode->i_flags |= S_NOATIME | S_NOCMTIME; // timestamps updated by server mapping_set_gfp_mask(&inode->i_data, GFP_USER); // avoid highmem for page cache pages // move values (no actual string copy) fhgfsInode->entryInfo = *entryInfo; switch (kstat->mode & S_IFMT) { case S_IFREG: // regular file { if(Config_getTuneFileCacheTypeNum(cfg) == FILECACHETYPE_Native) { inode->i_fop = &fhgfs_file_native_ops; inode->i_data.a_ops = &fhgfs_addrspace_native_ops; } else if(Config_getTuneFileCacheTypeNum(cfg) == FILECACHETYPE_Paged) { // with pagecache inode->i_fop = &fhgfs_file_pagecache_ops; inode->i_data.a_ops = &fhgfs_address_pagecache_ops; } else { // no pagecache (=> either none or buffered cache) inode->i_fop = &fhgfs_file_buffered_ops; inode->i_data.a_ops = &fhgfs_address_ops; } #ifdef KERNEL_HAS_ADDRESS_SPACE_BDI inode->i_data.backing_dev_info = FhgfsOps_getBdi(sb); #endif inode->i_op = App_getFileInodeOps(app); } break; case S_IFDIR: // directory { inode->i_op = App_getDirInodeOps(app); inode->i_fop = &fhgfs_dir_ops; } break; case S_IFLNK: // symlink { inode->i_op = App_getSymlinkInodeOps(app); } break; default: // pipes and other special files { inode->i_op = App_getSpecialInodeOps(app); init_special_inode(inode, kstat->mode, dev); } break; } unlock_new_inode(inode); // remove I_NEW flag, so the inode can be accessed by others return inode; // error occured cleanup_entryInfo: EntryInfo_uninit(entryInfo); // found an existing inode outNoCleanUp: return inode; } 

App_getFileInodeOps

  • 最后根据文件类型,赋予之前初始化好的inode操作指针:
// fhgfs_client_module\source\app\App.h struct inode_operations* App_getFileInodeOps(App* this) { return this->fileInodeOps; } struct inode_operations* App_getSymlinkInodeOps(App* this) { return this->symlinkInodeOps; } struct inode_operations* App_getDirInodeOps(App* this) { return this->dirInodeOps; } struct inode_operations* App_getSpecialInodeOps(App* this) { return this->specialInodeOps; } 
原文链接:https://my.oschina.net/LastRitter/blog/3071864
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