vfs.rar_VFS_linux vfs_linux 文件系统_vfs.c_vfs文件系统

The Linux Kernel Virtual File System (VFS) Reference ==================================================== Based on kernel version 2.1.61 First Edition November 3, 1997 Written by Andrew E. Mileski Abstract -------- The Linux Kernel Virtual File System is simple in concept, but complex in implementation, which makes it difficult for the first time file system developer to quickly understand. Having the kernel source code at hand makes it possible to learn all of the kernel's secrets, but this can consume much valuable development time. This document strives to flatten the normally steep learning curve into a gentle slope, so that a file system developer can spend less time studying the kernel source code, and more time on programming. Even so, this document is only a reference, and not a how-to manual. Table of Contents ----------------- 0. File System Type Structure 0.1 name 0.2 fs_flags 0.3 read_super 0.4 next 1. Super blocks 1.1 Super block Structure 1.1.1 s_dev 1.1.2 s_blocksize 1.1.3 s_blocksize_bits 1.1.4 s_lock 1.1.5 s_rd_only 1.1.6 s_dirt 1.1.7 s_type 1.1.8 s_op 1.1.9 dq_op 1.1.10 s_flags 1.1.11 s_magic 1.1.12 s_time 1.1.13 s_root 1.1.14 s_wait 1.1.15 s_ibasket 1.1.16 s_ibasket_count 1.1.17 s_ibasket_max 1.1.18 s_dirty 1.1.19 u 1.2 Super block Operations Structure 1.2.1 read_inode 1.2.2 write_inode 1.2.3 put_inode 1.2.4 delete_inode 1.2.5 notify_change 1.2.6 put_super 1.2.7 write_super 1.2.8 statfs 1.2.9 remount_fs 2. Inodes 2.1 Inode Structure 2.1.1 i_hash 2.1.2 i_list 2.1.3 i_ino 2.1.4 i_dev 2.1.5 i_count 2.1.6 i_mode 2.1.7 i_nlink 2.1.8 i_uid 2.1.9 i_gid 2.1.10 i_rdev 2.1.11 i_size 2.1.12 i_atime 2.1.13 i_mtime 2.1.14 i_ctime 2.1.15 i_blksize 2.1.16 i_blocks 2.1.17 i_version 2.1.18 i_nrpages 2.1.19 i_sem 2.1.20 i_op 2.1.21 i_sb 2.1.22 i_wait 2.1.23 i_flock 2.1.24 i_mmap 2.1.25 i_pages 2.1.26 i_dquot 2.1.27 i_state 2.1.28 i_flags 2.1.29 i_pipe 2.1.30 i_sock 2.1.31 i_writecount 2.1.32 i_attr_flags 2.1.33 u 2.2 Inode Operations Structure 2.2.1 default_file_ops 2.2.2 create 2.2.3 lookup 2.2.4 link 2.2.5 unlink 2.2.6 symlink 2.2.7 mkdir 2.2.8 rmdir 2.2.9 mknod 2.2.10 rename 2.2.11 readlink 2.2.12 follow_link 2.2.13 readpage 2.2.14 writepage 2.2.15 bmap 2.2.16 truncate 2.2.17 permission 2.2.18 smap 2.2.19 updatepage 2.2.20 revalidate 2.3 The Inode Cache 3. Files 3.1 File Structure 3.1.1 f_next 3.1.2 f_pprev 3.1.3 f_dentry 3.1.4 f_op 3.1.5 f_mode 3.1.6 f_pos 3.1.7 f_count 3.1.8 f_flags 3.1.9 f_reada 3.1.10 f_ramax 3.1.11 f_raend 3.1.12 f_ralen 3.1.13 f_rawin 3.1.14 f_owner 3.1.15 f_version 3.1.16 private_data 3.2 File Operations Structure 3.2.1 llseek 3.2.2 read 3.2.3 write 3.2.4 readdir 3.2.5 poll 3.2.6 ioctl 3.2.7 mmap 3.2.8 open 3.2.9 release 3.2.10 fsync 3.2.11 fasync 3.2.12 check_media_change 3.2.13 revalidate 3.2.14 lock 3.3 The File Table 4. The Directory Entry Cache 4.1 Dentry Structure 4.1.1 d_count 4.1.2 d_flags 4.1.3 d_inode 4.1.4 d_parent 4.1.5 d_mounts 4.1.6 d_covers 4.1.7 d_hash 4.1.8 d_lru 4.1.9 d_name 4.1.10 d_time 4.1.11 d_op 4.1.12 d_sb 4.2 Dentry Operations Structure 4.2.1 d_revalidate 4.2.2 d_hash 4.2.3 d_compare 4.2.4 d_delete 4.3 Quick Strings 4.3.1 Quick String Structure 4.3.1.1 name 4.3.1.2 len 4.3.1.3 hash 4.3.2 Hashing a Quick String 5. The Buffer Cache 5.1 The Buffer Head Structure 5.1.1 b_next 5.1.2 b_blocknr 5.1.3 b_size 5.1.4 b_dev 5.1.5 b_rdev 5.1.6 b_rsector 5.1.7 b_this_page 5.1.8 b_state 5.1.9 b_next_free 5.1.10 b_count 5.1.11 b_data 5.1.12 b_list 5.1.13 b_flushtime 5.1.14 b_lru_time 5.1.15 b_wait 5.1.16 b_pprev 5.1.17 b_prev_free 5.1.18 b_reqnext 5.2 Reading a Buffer 5.3 Writing a Buffer 4. Regular files 5. Directories 6. Links 7. Symbolic links 8. Block Devices 9. Character Devices 10. Memory Mapped Files 11. Quotas 11.1 Quota Operations Structure 11.1.1 initialize 11.1.2 drop 11.1.3 alloc_block 11.1.4 alloc_inode 11.1.5 free_block 11.1.6 free_inode 11.1.7 transfer 12. The VFS Character Set 12.1 Encoding with UTF-8. Appendix A List of Kernel Filesystem Routines Appendix B Linux on the Internet ----------------- Preface ------- This document is a result of many hours of studying the Linux kernel source code by the author, in an attempt to implement a new file system type [OSTA-UDF(tm) to be exact]. Like all tools, this document was born out of frustration with the lack of documention available on the subject. A few seasoned Linux kernel developers claim the kernel source code is "self documenting", which the author of this document strongly disagrees with. Though every attempt has been made to ensure the correctness of this document, the author cannot make any guarantees as to its accuracy. The Linux kernel source code is constantly being revised, debugged, and upgraded by volunteer programmers from around the globe. This particular document is based on the 2.1.61 experimental kernel, which was the latest available at the time of writing. 0. File System Type Structure ------------------------------ The following definition of the file system type structure can be found in the header file linux/include/linux/fs.h struct file_system_type { const char *name; int fs_flags; struct super_block *(*read_super) (struct super_block *, void *, int); struct file_system_type * next; }; This structure is registered with the kernel to add support for the new file system type. 0.1 name --------- Definition: const char *name; Purpose: Pointer to a name string for the file system type. Description: The name string is used to locate the file system driver to use when mounting. For convenience, the name should be short (8 characters or less is reasonable), and should only contain printable lower case letters [a-z] and numbers [0-9]. The following are reserved: affs Amiga Fast File System afs Andrew File System autofs AUTO-mounter File System coherent Coherent ext EXTended (obsolete) ext2 Second EXTended (Linux native) hpfs High Performance File System (OS/2) iso9660 ISO 9660 compliant minix Minix msdos MS-DOS (FAT12 and FAT16) ncpfs Novell File System nfs Network File System proc PROCess romfs ROM File System smbfs SamBA File System sysv SYSV (and SYSV2, SYSV4) udf Universal Disk Format ufs umsdos Use MS-DOS vfat Versatile FAT (extended FAT16, FAT32) xenix Xenix Status: Required. 0.2 fs_flags ------------- Definition: int fs_flags; Purpose: File system flags. Description: The following flags can be combined with a bitwise OR: FS_REQUIRES_DEV File system requires a block device. FS_NO_DCACHE Only dcache the necessary things. FS_NO_PRELIM Prevent preloading of dentries, even if FS_NO_DCACHE is not set. FS_IBASKET File syst