Linux文件系统
2015-11-19 19:46
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首先要从fs.h头文件开始,file的定义为:
其中struct path的定义为:
dentry的定义为:
dentry里有一个结构体inode,记录了file的重要相关信息
里面有个关键成员const struct file_operations *i_fop;,定义为:
这些函数就是底层需要实现的部分,当然不需要实现所有的部分,具体看是什么设备,和具体需要的功能,来实现相应的函数。
<span style="font-size:14px;"> /* * fu_list becomes invalid after file_free is called and queued via * fu_rcuhead for RCU freeing */ union { struct list_head fu_list; struct rcu_head fu_rcuhead; } f_u; struct path f_path; #define f_dentry f_path.dentry #define f_vfsmnt f_path.mnt const struct file_operations *f_op; spinlock_t f_lock; /* f_ep_links, f_flags, no IRQ */ atomic_long_t f_count; unsigned int f_flags; fmode_t f_mode; loff_t f_pos; struct fown_struct f_owner; const struct cred *f_cred; struct file_ra_state f_ra; u64 f_version; #ifdef CONFIG_SECURITY void *f_security; #endif /* needed for tty driver, and maybe others */ void *private_data; #ifdef CONFIG_EPOLL /* Used by fs/eventpoll.c to link all the hooks to this file */ struct list_head f_ep_links; struct list_head f_tfile_llink; #endif /* #ifdef CONFIG_EPOLL */ struct address_space *f_mapping; #ifdef CONFIG_DEBUG_WRITECOUNT unsigned long f_mnt_write_state; #endif };</span>
其中struct path的定义为:
<span style="font-size:14px;">struct path { struct vfsmount *mnt; struct dentry *dentry; </span><span style="font-family:KaiTi_GB2312;font-size:14px;">}; </span>
dentry的定义为:
<span style="font-size:14px;">struct dentry { atomic_t d_count; unsigned int d_flags; /* protected by d_lock */ spinlock_t d_lock; /* per dentry lock */ int d_mounted; struct inode *d_inode; /* Where the name belongs to - NULL is * negative */ /* </span><span style="font-size:14px;"> * The next three fields are touched by __d_lookup. Place them here * so they all fit in a cache line. */ struct hlist_node d_hash; /* lookup hash list */ 通过查询哈希表的方式,可以比较快的找到一个inode。 struct dentry *d_parent; /* parent directory */ struct qstr d_name; struct list_head d_lru; /* LRU list */ /* * d_child and d_rcu can share memory */ union { struct list_head d_child; /* child of parent list */ struct rcu_head d_rcu; } d_u; struct list_head d_subdirs; /* our children */ struct list_head d_alias; /* inode alias list */ unsigned long d_time; /* used by d_revalidate */ const struct dentry_operations *d_op; struct super_block *d_sb; /* The root of the dentry tree */ void *d_fsdata; /* fs-specific data */ unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */ }; </span>
dentry里有一个结构体inode,记录了file的重要相关信息
<span style="font-size:14px;">struct inode { struct hlist_node i_hash; struct list_head i_list; /* backing dev IO list */ struct list_head i_sb_list; struct list_head i_dentry; unsigned long i_ino; atomic_t i_count; unsigned int i_nlink; //link数 uid_t i_uid; //用户,组信息, gid_t i_gid; dev_t i_rdev; u64 i_version; loff_t i_size; #ifdef __NEED_I_SIZE_ORDERED seqcount_t i_size_seqcount; #endif struct timespec i_atime; struct timespec i_mtime; struct timespec i_ctime; blkcnt_t i_blocks; unsigned int i_blkbits; unsigned short i_bytes; umode_t i_mode; spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */ struct mutex i_mutex; struct rw_semaphore i_alloc_sem; const struct inode_operations *i_op; //默认文件操作。 const struct file_operations *i_fop; /* former ->i_op->default_file_ops */ struct super_block *i_sb; struct file_lock *i_flock; struct address_space *i_mapping; struct address_space i_data; #ifdef CONFIG_QUOTA struct dquot *i_dquot[MAXQUOTAS]; #endif struct list_head i_devices; union { struct pipe_inode_info *i_pipe; struct block_device *i_bdev; struct cdev *i_cdev; }; __u32 i_generation; #ifdef CONFIG_FSNOTIFY __u32 i_fsnotify_mask; /* all events this inode cares about */ struct hlist_head i_fsnotify_mark_entries; /* fsnotify mark entries */ #endif #ifdef CONFIG_INOTIFY struct list_head inotify_watches; /* watches on this inode */ struct mutex inotify_mutex; /* protects the watches list */ #endif unsigned long i_state; unsigned long dirtied_when; /* jiffies of first dirtying */ unsigned int i_flags; atomic_t i_writecount; #ifdef CONFIG_SECURITY void *i_security; #endif #ifdef CONFIG_FS_POSIX_ACL struct posix_acl *i_acl; struct posix_acl *i_default_acl; #endif void *i_private; /* fs or device private pointer */ };</span>
里面有个关键成员const struct file_operations *i_fop;,定义为:
<span style="font-size:14px;">struct file_operations { struct module *owner; loff_t (*llseek) (struct file *, loff_t, int); ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t); ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t); int (*readdir) (struct file *, void *, filldir_t); unsigned int (*poll) (struct file *, struct poll_table_struct *); int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long); long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); long (*compat_ioctl) (struct file *, unsigned int, unsigned long); int (*mmap) (struct file *, struct vm_area_struct *); int (*open) (struct inode *, struct file *); int (*flush) (struct file *, fl_owner_t id); int (*release) (struct inode *, struct file *); int (*fsync) (struct file *, struct dentry *, int datasync); int (*aio_fsync) (struct kiocb *, int datasync); int (*fasync) (int, struct file *, int); int (*lock) (struct file *, int, struct file_lock *); ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int); unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); int (*check_flags)(int); int (*flock) (struct file *, int, struct file_lock *); ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int); ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int); int (*setlease)(struct file *, long, struct file_lock **); };</span>
这些函数就是底层需要实现的部分,当然不需要实现所有的部分,具体看是什么设备,和具体需要的功能,来实现相应的函数。