Linux Kernel linux/fs.h
阿新 • • 發佈：2020-09-19
1 // 2 // linux/fs.h 3 // linux檔案系統最外圍結構之一，超級塊 4 // 5 struct super_block { 6 // 7 // 雙向連結串列，所有檔案系統的超級快通過這個連結在一起 8 // 9 struct list_head s_list; /* Keep this first */ 10 // 11 // 裝置???目前不明 12 // 13 dev_t s_dev; /* search index; _not_ kdev_t */ 14unsigned char s_blocksize_bits; 15 unsigned long s_blocksize; 16 // 17 //該檔案系統最大檔案大小 18 // 19 loff_t s_maxbytes; /* Max file size */ 20 // 21 // 檔案系統指標，在一個檔案系統驅動註冊的時候填寫好這個 22 // 結構體，通過 register_filesystem(); 註冊進來!!!!! 23 // 24 struct file_system_type *s_type;25 // 26 // 最重要的結構之一，超級塊的操作 27 // 28 const struct super_operations *s_op; 29 const struct dquot_operations *dq_op; 30 const struct quotactl_ops *s_qcop; 31 const struct export_operations *s_export_op; 32 unsigned long s_flags; 33 unsigned long s_iflags; /*internal SB_I_* flags */ 34 // 35 // 超級塊的魔數 36 // 37 unsigned long s_magic; 38 // 39 // 檔案系統掛載的目錄項 40 // 41 struct dentry *s_root; 42 struct rw_semaphore s_umount; 43 int s_count; 44 atomic_t s_active; 45 #ifdef CONFIG_SECURITY 46 void *s_security; 47 #endif 48 const struct xattr_handler **s_xattr; 49 #ifdef CONFIG_FS_ENCRYPTION 50 const struct fscrypt_operations *s_cop; 51 #endif 52 struct hlist_bl_head s_roots; /* alternate root dentries for NFS */ 53 struct list_head s_mounts; /* list of mounts; _not_ for fs use */ 54 struct block_device *s_bdev; 55 struct backing_dev_info *s_bdi; 56 struct mtd_info *s_mtd; 57 struct hlist_node s_instances; 58 unsigned int s_quota_types; /* Bitmask of supported quota types */ 59 struct quota_info s_dquot; /* Diskquota specific options */ 60 61 struct sb_writers s_writers; 62 63 /* 64 * Keep s_fs_info, s_time_gran, s_fsnotify_mask, and 65 * s_fsnotify_marks together for cache efficiency. They are frequently 66 * accessed and rarely modified. 67 */ 68 void *s_fs_info; /* Filesystem private info */ 69 70 /* Granularity of c/m/atime in ns (cannot be worse than a second) */ 71 u32 s_time_gran; 72 #ifdef CONFIG_FSNOTIFY 73 __u32 s_fsnotify_mask; 74 struct fsnotify_mark_connector __rcu *s_fsnotify_marks; 75 #endif 76 77 char s_id[32]; /* Informational name */ 78 uuid_t s_uuid; /* UUID */ 79 80 unsigned int s_max_links; 81 fmode_t s_mode; 82 83 /* 84 * The next field is for VFS *only*. No filesystems have any business 85 * even looking at it. You had been warned. 86 */ 87 struct mutex s_vfs_rename_mutex; /* Kludge */ 88 89 /* 90 * Filesystem subtype. If non-empty the filesystem type field 91 * in /proc/mounts will be "type.subtype" 92 */ 93 const char *s_subtype; 94 // 95 // 目錄項的操作方法 96 // 97 const struct dentry_operations *s_d_op; /* default d_op for dentries */ 98 99 /* 100 * Saved pool identifier for cleancache (-1 means none) 101 */ 102 int cleancache_poolid; 103 104 struct shrinker s_shrink; /* per-sb shrinker handle */ 105 106 /* Number of inodes with nlink == 0 but still referenced */ 107 atomic_long_t s_remove_count; 108 109 /* Pending fsnotify inode refs */ 110 atomic_long_t s_fsnotify_inode_refs; 111 112 /* Being remounted read-only */ 113 int s_readonly_remount; 114 115 /* AIO completions deferred from interrupt context */ 116 struct workqueue_struct *s_dio_done_wq; 117 struct hlist_head s_pins; 118 119 /* 120 * Owning user namespace and default context in which to 121 * interpret filesystem uids, gids, quotas, device nodes, 122 * xattrs and security labels. 123 */ 124 struct user_namespace *s_user_ns; 125 126 /* 127 * The list_lru structure is essentially just a pointer to a table 128 * of per-node lru lists, each of which has its own spinlock. 129 * There is no need to put them into separate cachelines. 130 */ 131 // 132 // 應該是未使用的dentry和inode連結串列 133 // 134 struct list_lru s_dentry_lru; 135 struct list_lru s_inode_lru; 136 struct rcu_head rcu; 137 struct work_struct destroy_work; 138 139 struct mutex s_sync_lock; /* sync serialisation lock */ 140 141 /* 142 * Indicates how deep in a filesystem stack this SB is 143 */ 144 int s_stack_depth; 145 146 /* s_inode_list_lock protects s_inodes */ 147 spinlock_t s_inode_list_lock ____cacheline_aligned_in_smp; 148 struct list_head s_inodes; /* all inodes */ 149 150 spinlock_t s_inode_wblist_lock; 151 struct list_head s_inodes_wb; /* writeback inodes */ 152 } __randomize_layout; 153 154 155 // 156 // 對應 super_block->s_op 157 // 158 struct super_operations { 159 // 160 // 初始化新的索引節點, inode 161 // 162 struct inode *(*alloc_inode)(struct super_block *sb); 163 void (*destroy_inode)(struct inode *); 164 void (*free_inode)(struct inode *); 165 166 void (*dirty_inode) (struct inode *, int flags); 167 int (*write_inode) (struct inode *, struct writeback_control *wbc); 168 int (*drop_inode) (struct inode *); 169 void (*evict_inode) (struct inode *); 170 void (*put_super) (struct super_block *); 171 int (*sync_fs)(struct super_block *sb, int wait); 172 int (*freeze_super) (struct super_block *); 173 int (*freeze_fs) (struct super_block *); 174 int (*thaw_super) (struct super_block *); 175 int (*unfreeze_fs) (struct super_block *); 176 int (*statfs) (struct dentry *, struct kstatfs *); 177 int (*remount_fs) (struct super_block *, int *, char *); 178 void (*umount_begin) (struct super_block *); 179 180 int (*show_options)(struct seq_file *, struct dentry *); 181 int (*show_devname)(struct seq_file *, struct dentry *); 182 int (*show_path)(struct seq_file *, struct dentry *); 183 int (*show_stats)(struct seq_file *, struct dentry *); 184 #ifdef CONFIG_QUOTA 185 ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t); 186 ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t); 187 struct dquot **(*get_dquots)(struct inode *); 188 #endif 189 int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t); 190 long (*nr_cached_objects)(struct super_block *, 191 struct shrink_control *); 192 long (*free_cached_objects)(struct super_block *, 193 struct shrink_control *); 194 }; 195 196 197 /* 198 * Keep mostly read-only and often accessed (especially for 199 * the RCU path lookup and 'stat' data) fields at the beginning 200 * of the 'struct inode' 201 */ 202 203 // 204 // 檔案系統inode節點 205 // 206 207 struct inode { 208 umode_t i_mode; 209 unsigned short i_opflags; 210 kuid_t i_uid; 211 kgid_t i_gid; 212 unsigned int i_flags; 213 214 // 215 // 當核心配置了POSIX ACL後開啟，一般開啟 216 // 217 #ifdef CONFIG_FS_POSIX_ACL 218 struct posix_acl *i_acl; 219 struct posix_acl *i_default_acl; 220 #endif 221 // 222 // inode操作 223 // 224 const struct inode_operations *i_op; 225 // 226 // 指向超級塊 227 // 228 struct super_block *i_sb; 229 // 230 // 指向address_space 231 // 232 struct address_space *i_mapping; 233 234 #ifdef CONFIG_SECURITY 235 void *i_security; 236 #endif 237 // 238 // inode number 239 // 240 /* Stat data, not accessed from path walking */ 241 unsigned long i_ino; 242 /* 243 * Filesystems may only read i_nlink directly. They shall use the 244 * following functions for modification: 245 * 246 * (set|clear|inc|drop)_nlink 247 * inode_(inc|dec)_link_count 248 */ 249 union { 250 const unsigned int i_nlink; 251 unsigned int __i_nlink; 252 }; 253 dev_t i_rdev; 254 // 255 // 檔案大小，多少個位元組 256 // 257 loff_t i_size; 258 // i_atime access time 259 // i_mtime modify time 260 // i_ctime create time 261 struct timespec64 i_atime; 262 struct timespec64 i_mtime; 263 struct timespec64 i_ctime; 264 spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */ 265 unsigned short i_bytes; 266 u8 i_blkbits; 267 u8 i_write_hint; 268 blkcnt_t i_blocks; 269 270 #ifdef __NEED_I_SIZE_ORDERED 271 seqcount_t i_size_seqcount; 272 #endif 273 274 /* Misc */ 275 unsigned long i_state; 276 struct rw_semaphore i_rwsem; 277 278 unsigned long dirtied_when; /* jiffies of first dirtying */ 279 unsigned long dirtied_time_when; 280 281 struct hlist_node i_hash; 282 struct list_head i_io_list; /* backing dev IO list */ 283 #ifdef CONFIG_CGROUP_WRITEBACK 284 struct bdi_writeback *i_wb; /* the associated cgroup wb */ 285 286 /* foreign inode detection, see wbc_detach_inode() */ 287 int i_wb_frn_winner; 288 u16 i_wb_frn_avg_time; 289 u16 i_wb_frn_history; 290 #endif 291 struct list_head i_lru; /* inode LRU list */ 292 struct list_head i_sb_list; 293 struct list_head i_wb_list; /* backing dev writeback list */ 294 union { 295 struct hlist_head i_dentry; 296 struct rcu_head i_rcu; 297 }; 298 atomic64_t i_version; 299 atomic_t i_count; 300 atomic_t i_dio_count; 301 atomic_t i_writecount; 302 #if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING) 303 atomic_t i_readcount; /* struct files open RO */ 304 #endif 305 union { 306 const struct file_operations *i_fop; /* former ->i_op->default_file_ops */ 307 void (*free_inode)(struct inode *); 308 }; 309 struct file_lock_context *i_flctx; 310 struct address_space i_data; 311 struct list_head i_devices; 312 union { 313 struct pipe_inode_info *i_pipe; 314 struct block_device *i_bdev; 315 struct cdev *i_cdev; 316 char *i_link; 317 unsigned i_dir_seq; 318 }; 319 320 __u32 i_generation; 321 322 #ifdef CONFIG_FSNOTIFY 323 __u32 i_fsnotify_mask; /* all events this inode cares about */ 324 struct fsnotify_mark_connector __rcu *i_fsnotify_marks; 325 #endif 326 327 #ifdef CONFIG_FS_ENCRYPTION 328 struct fscrypt_info *i_crypt_info; 329 #endif 330 // 331 // 私有結構 332 // 333 void *i_private; /* fs or device private pointer */ 334 } __randomize_layout; 335 336 // 337 // inode 節點操作方法 338 // 339 struct inode_operations { 340 //查詢 341 struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int); 342 const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *); 343 int (*permission) (struct inode *, int); 344 struct posix_acl * (*get_acl)(struct inode *, int); 345 346 int (*readlink) (struct dentry *, char __user *,int); 347 // 348 // 建立一個新的索引節點 349 // 350 int (*create) (struct inode *,struct dentry *, umode_t, bool); 351 // 352 // 建立硬連結 353 // 354 int (*link) (struct dentry *,struct inode *,struct dentry *); 355 // 356 // 取消硬連結 357 // 358 int (*unlink) (struct inode *,struct dentry *); 359 // 360 // 建立符號連結 361 // 362 int (*symlink) (struct inode *,struct dentry *,const char *); 363 // 364 // 建立目錄 365 // 366 int (*mkdir) (struct inode *,struct dentry *,umode_t); 367 // 368 // 刪除目錄 369 // 370 int (*rmdir) (struct inode *,struct dentry *); 371 // 372 // 建立塊裝置節點 373 // 374 int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t); 375 // 376 // 重新命名 377 // 378 int (*rename) (struct inode *, struct dentry *, 379 struct inode *, struct dentry *, unsigned int); 380 // 381 // 設定屬性 382 // 383 int (*setattr) (struct dentry *, struct iattr *); 384 // 385 // 得到屬性 386 // 387 int (*getattr) (const struct path *, struct kstat *, u32, unsigned int); 388 ssize_t (*listxattr) (struct dentry *, char *, size_t); 389 // 390 // 從函式名來看是檔案對映 391 // 392 int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, 393 u64 len); 394 int (*update_time)(struct inode *, struct timespec64 *, int); 395 int (*atomic_open)(struct inode *, struct dentry *, 396 struct file *, unsigned open_flag, 397 umode_t create_mode); 398 int (*tmpfile) (struct inode *, struct dentry *, umode_t); 399 int (*set_acl)(struct inode *, struct posix_acl *, int); 400 } ____cacheline_aligned; 401 402 // 403 // dentry --> directory entry 目錄項 404 // 一般結構是: file ==> dentry ==> inode 405 // 對於程序來說: task_struct 有一個結構體叫 406 // task_struct -> files_struct -> fdtable->file 407 // 408 // 409 // 410 // 411 412 413 // 414 // dentry 定義在dcache.h 415 // 416 struct dentry { 417 /* RCU lookup touched fields */ 418 unsigned int d_flags; /* protected by d_lock */ 419 seqcount_t d_seq; /* per dentry seqlock */ 420 // 421 // 查詢hash表 422 // 423 struct hlist_bl_node d_hash; /* lookup hash list */ 424 // 425 // 父目錄項 426 // 427 struct dentry *d_parent; /* parent directory */ 428 struct qstr d_name; 429 // 430 // dentry 對應inode節點 431 // 432 struct inode *d_inode; /* Where the name belongs to - NULL is 433 * negative */ 434 unsigned char d_iname[DNAME_INLINE_LEN]; /* small names */ 435 436 /* Ref lookup also touches following */ 437 struct lockref d_lockref; /* per-dentry lock and refcount */ 438 const struct dentry_operations *d_op; 439 struct super_block *d_sb; /* The root of the dentry tree */ 440 unsigned long d_time; /* used by d_revalidate */ 441 void *d_fsdata; /* fs-specific data */ 442 443 union { 444 struct list_head d_lru; /* LRU list */ 445 wait_queue_head_t *d_wait; /* in-lookup ones only */ 446 }; 447 // 448 // 父目錄目錄項鍊表 449 // 450 struct list_head d_child; /* child of parent list */ 451 // 452 // 自己子目錄連結串列 453 // 454 struct list_head d_subdirs; /* our children */ 455 /* 456 * d_alias and d_rcu can share memory 457 */ 458 union { 459 struct hlist_node d_alias; /* inode alias list */ 460 struct hlist_bl_node d_in_lookup_hash; /* only for in-lookup ones */ 461 struct rcu_head d_rcu; 462 } d_u; 463 } __randomize_layout; 464 465 466 struct dentry_operations { 467 // 468 // 判斷目錄項是否實效 469 // 470 int (*d_revalidate)(struct dentry *, unsigned int); 471 // 472 // 473 // 474 int (*d_weak_revalidate)(struct dentry *, unsigned int); 475 // 476 // 生成hash,VFS插入目錄項時會計算hash 477 // 478 int (*d_hash)(const struct dentry *, struct qstr *); 479 // 480 // 比較字串 481 // 482 int (*d_compare)(const struct dentry *, 483 unsigned int, const char *, const struct qstr *); 484 // 485 // 當d_count 為零是呼叫 486 // 487 int (*d_delete)(const struct dentry *); 488 int (*d_init)(struct dentry *); 489 // 490 // 檔案被釋放時被呼叫 491 // 492 void (*d_release)(struct dentry *); 493 void (*d_prune)(struct dentry *); 494 // 495 // 當目錄項丟失inode節點時候呼叫 496 // 497 void (*d_iput)(struct dentry *, struct inode *); 498 char *(*d_dname)(struct dentry *, char *, int); 499 struct vfsmount *(*d_automount)(struct path *); 500 int (*d_manage)(const struct path *, bool); 501 struct dentry *(*d_real)(struct dentry *, const struct inode *); 502 } ____cacheline_aligned; 503 504 // 505 // path 506 // 507 struct path { 508 struct vfsmount *mnt; 509 struct dentry *dentry; 510 } __randomize_layout; 511 512 struct vfsmount { 513 struct dentry *mnt_root; /* root of the mounted tree */ 514 struct super_block *mnt_sb; /* pointer to superblock */ 515 int mnt_flags; 516 } __randomize_layout; 517 518 // 519 // struct file, 檔案物件 520 // 521 struct file { 522 union { 523 // 524 // 檔案物件連結串列 525 // 526 struct llist_node fu_llist; 527 struct rcu_head fu_rcuhead; 528 } f_u; 529 // 530 // path struct path { 531 // struct vfsmount *mnt; // vfs掛載點 532 // struct dentry *dentry; // 對應目錄項 533 //} __randomize_layout; 534 535 // 536 struct path f_path; 537 struct inode *f_inode; /* cached value */ 538 // 539 // 檔案操作函式 540 // 541 const struct file_operations *f_op; 542 543 /* 544 * Protects f_ep_links, f_flags. 545 * Must not be taken from IRQ context. 546 */ 547 spinlock_t f_lock; 548 enum rw_hint f_write_hint; 549 // 550 // 檔案被多少程序使用 551 // 552 atomic_long_t f_count; 553 unsigned int f_flags; 554 fmode_t f_mode; 555 struct mutex f_pos_lock; 556 // 557 // 檔案指標位置 558 // 559 loff_t f_pos; 560 struct fown_struct f_owner; 561 const struct cred *f_cred; 562 struct file_ra_state f_ra; 563 564 u64 f_version; 565 #ifdef CONFIG_SECURITY 566 void *f_security; 567 #endif 568 /* needed for tty driver, and maybe others */ 569 void *private_data; 570 571 #ifdef CONFIG_EPOLL 572 /* Used by fs/eventpoll.c to link all the hooks to this file */ 573 struct list_head f_ep_links; 574 struct list_head f_tfile_llink; 575 #endif /* #ifdef CONFIG_EPOLL */ 576 // 577 // address_space 578 // 579 struct address_space *f_mapping; 580 errseq_t f_wb_err; 581 } __randomize_layout 582 __attribute__((aligned(4))); /* lest something weird decides that 2 is OK */ 583 584 struct file_handle { 585 __u32 handle_bytes; 586 int handle_type; 587 /* file identifier */ 588 unsigned char f_handle[0]; 589 }; 590 591 // 592 // 593 // 594 struct file_operations { 595 struct module *owner; 596 loff_t (*llseek) (struct file *, loff_t, int); 597 ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); 598 ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); 599 ssize_t (*read_iter) (struct kiocb *, struct iov_iter *); 600 ssize_t (*write_iter) (struct kiocb *, struct iov_iter *); 601 int (*iopoll)(struct kiocb *kiocb, bool spin); 602 int (*iterate) (struct file *, struct dir_context *); 603 int (*iterate_shared) (struct file *, struct dir_context *); 604 __poll_t (*poll) (struct file *, struct poll_table_struct *); 605 long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); 606 long (*compat_ioctl) (struct file *, unsigned int, unsigned long); 607 int (*mmap) (struct file *, struct vm_area_struct *); 608 unsigned long mmap_supported_flags; 609 int (*open) (struct inode *, struct file *); 610 int (*flush) (struct file *, fl_owner_t id); 611 int (*release) (struct inode *, struct file *); 612 int (*fsync) (struct file *, loff_t, loff_t, int datasync); 613 int (*fasync) (int, struct file *, int); 614 int (*lock) (struct file *, int, struct file_lock *); 615 ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int); 616 unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); 617 int (*check_flags)(int); 618 int (*flock) (struct file *, int, struct file_lock *); 619 ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int); 620 ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int); 621 int (*setlease)(struct file *, long, struct file_lock **, void **); 622 long (*fallocate)(struct file *file, int mode, loff_t offset, 623 loff_t len); 624 void (*show_fdinfo)(struct seq_file *m, struct file *f); 625 #ifndef CONFIG_MMU 626 unsigned (*mmap_capabilities)(struct file *); 627 #endif 628 ssize_t (*copy_file_range)(struct file *, loff_t, struct file *, 629 loff_t, size_t, unsigned int); 630 loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in, 631 struct file *file_out, loff_t pos_out, 632 loff_t len, unsigned int remap_flags); 633 int (*fadvise)(struct file *, loff_t, loff_t, int); 634 } __randomize_layout; 635 636 // 637 // 檔案系統型別 638 // 639 struct file_system_type { 640 const char *name; 641 int fs_flags; 642 #define FS_REQUIRES_DEV 1 643 #define FS_BINARY_MOUNTDATA 2 644 #define FS_HAS_SUBTYPE 4 645 #define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */ 646 #define FS_DISALLOW_NOTIFY_PERM 16 /* Disable fanotify permission events */ 647 #define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */ 648 int (*init_fs_context)(struct fs_context *); 649 const struct fs_parameter_description *parameters; 650 struct dentry *(*mount) (struct file_system_type *, int, 651 const char *, void *); 652 void (*kill_sb) (struct super_block *); 653 struct module *owner; 654 struct file_system_type * next; 655 struct hlist_head fs_supers; 656 657 struct lock_class_key s_lock_key; 658 struct lock_class_key s_umount_key; 659 struct lock_class_key s_vfs_rename_key; 660 struct lock_class_key s_writers_key[SB_FREEZE_LEVELS]; 661 662 struct lock_class_key i_lock_key; 663 struct lock_class_key i_mutex_key; 664 struct lock_class_key i_mutex_dir_key; 665 }; 666 // 667 // 掛載點 668 // 669 struct vfsmount { 670 struct dentry *mnt_root; /* root of the mounted tree */ 671 struct super_block *mnt_sb; /* pointer to superblock */ 672 int mnt_flags; 673 } __randomize_layout;