2013年02月19日 情報科学類 オペレーティングシステム II 筑波大学 システム情報工学研究科 コンピュータサイエンス専攻, 電子・情報工学系 新城 靖 <yas@cs.tsukuba.ac.jp>
このページは、次の URL にあります。
http://www.coins.tsukuba.ac.jp/~yas/coins/os2-2012/2013-02-19
あるいは、次のページから手繰っていくこともできます。
http://www.coins.tsukuba.ac.jp/~yas/
http://www.cs.tsukuba.ac.jp/~yas/
試験について
解決策:
図? ファイル・システム実現に置ける層構造
ディスク・キャッシュの層もある。解決策
$ ls -l /bin/{gunzip,gzip,zcat}
-rwxr-xr-x 3 root root 62872 Jan 21 2010 /bin/gunzip
-rwxr-xr-x 3 root root 62872 Jan 21 2010 /bin/gzip
-rwxr-xr-x 3 root root 62872 Jan 21 2010 /bin/zcat
$ ls -li /bin/{gunzip,gzip,zcat}
5636134 -rwxr-xr-x 3 root root 62872 Jan 21 2010 /bin/gunzip
5636134 -rwxr-xr-x 3 root root 62872 Jan 21 2010 /bin/gzip
5636134 -rwxr-xr-x 3 root root 62872 Jan 21 2010 /bin/zcat
$
$ cat /etc/fstab
LABEL=/ / ext3 defaults 1 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
LABEL=SWAP-sda3 swap swap defaults 0 0
130.158.86.2:/vol/vol1/home /home nfs rw,hard,bg,nfsvers=3,intr 0 0
130.158.86.2:/vol/vol5/local3 /usr/local3 nfs rw,hard,bg,nfsvers=3,intr 0 0
$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 222G 13G 198G 6% /
tmpfs 2.0G 0 2.0G 0% /dev/shm
130.158.86.2:/vol/vol1/home
4.0T 1.5T 2.5T 38% /home
130.158.86.2:/vol/vol5/local3
80G 4.9G 76G 7% /usr/local3
$
図? スーパーブロック、inode、dentry、file
linux-3.6.8/include/linux/fs.h 1022: struct file { ... 1031: struct path f_path; 1032: #define f_dentry f_path.dentry ... 1044: atomic_long_t f_count; ... 1046: fmode_t f_mode; 1047: loff_t f_pos; ... 1057: void *private_data; ... 1068: };
図? C言語によるオブジェクト指向の継承の実装方法。共通インスタンス変数・関数、固有インスタンス変数関数の置き方
struct fileの操作は、たとえば次のような形で行われる。 第1引数は、struct file *。
struct file *file; file->f_op->read(file, buf, count, pos);f_op には、次のような手続きがある。各ファイルシステム (ext4,nfs,tmpfs,...) ごとに、手続きの実体は異なるが、インタフェースは同じ。
linux-3.6.8/include/linux/fs.h 1777: struct file_operations { 1778: struct module *owner; 1779: loff_t (*llseek) (struct file *, loff_t, int); 1780: ssize_t (*read) (struct file *, char __user *, size_t, loff_t *); 1781: ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *); 1782: ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t); 1783: ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long, loff_t); 1784: int (*readdir) (struct file *, void *, filldir_t); 1785: unsigned int (*poll) (struct file *, struct poll_table_struct *); 1786: long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); 1787: long (*compat_ioctl) (struct file *, unsigned int, unsigned long); 1788: int (*mmap) (struct file *, struct vm_area_struct *); 1789: int (*open) (struct inode *, struct file *); 1790: int (*flush) (struct file *, fl_owner_t id); 1791: int (*release) (struct inode *, struct file *); 1792: int (*fsync) (struct file *, loff_t, loff_t, int datasync); 1793: int (*aio_fsync) (struct kiocb *, int datasync); 1794: int (*fasync) (int, struct file *, int); 1795: int (*lock) (struct file *, int, struct file_lock *); 1796: ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int); 1797: unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); 1798: int (*check_flags)(int); 1799: int (*flock) (struct file *, int, struct file_lock *); 1800: ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int); 1801: ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int); 1802: int (*setlease)(struct file *, long, struct file_lock **); 1803: long (*fallocate)(struct file *file, int mode, loff_t offset, 1804: loff_t len); 1805: };主な手続きの意味
linux-3.6.8/include/linux/dcache.h 103: struct dentry { ... 108: struct dentry *d_parent; /* parent directory */ 109: struct qstr d_name; 110: struct inode *d_inode; /* Where the name belongs to - NULL is ... 115: unsigned int d_count; /* protected by d_lock */ ... 117: const struct dentry_operations *d_op; 118: struct super_block *d_sb; /* The root of the dentry tree */ ... 120: void *d_fsdata; /* fs-specific data */ ... 130: struct list_head d_subdirs; /* our children */ ... 132: }; 30: #define HASH_LEN_DECLARE u32 hash; u32 len; 42: struct qstr { ... 45: HASH_LEN_DECLARE; ... 49: const unsigned char *name; 50: }; ... 99: # define DNAME_INLINE_LEN 40 /* 128 bytes */
linux-3.6.8/include/linux/fs.h 782: struct inode { 783: umode_t i_mode; 784: unsigned short i_opflags; 785: kuid_t i_uid; 786: kgid_t i_gid; ... 794: const struct inode_operations *i_op; 795: struct super_block *i_sb; ... 803: unsigned long i_ino; ... 812: const unsigned int i_nlink; ... 815: dev_t i_rdev; 816: loff_t i_size; 817: struct timespec i_atime; 818: struct timespec i_mtime; 819: struct timespec i_ctime; 820: spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */ 821: unsigned short i_bytes; 822: unsigned int i_blkbits; 823: blkcnt_t i_blocks; ... 830: unsigned long i_state; ... 835: struct hlist_node i_hash; ... 840: struct hlist_head i_dentry; ... 844: atomic_t i_count; ... 870: void *i_private; /* fs or device private pointer */ 871: };
struct inode *inode; ... inode->i_op->truncate(inode);i_op には、次のような手続きがある。各ファイルシステム (ext3,nfs,tmpfs,...) ごとに、手続きの実体は異なるが、インタフェースは同じ。
linux-3.6.8/include/linux/fs.h 1807: struct inode_operations { 1808: struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int); 1809: void * (*follow_link) (struct dentry *, struct nameidata *); 1810: int (*permission) (struct inode *, int); 1811: struct posix_acl * (*get_acl)(struct inode *, int); 1812: 1813: int (*readlink) (struct dentry *, char __user *,int); 1814: void (*put_link) (struct dentry *, struct nameidata *, void *); 1815: 1816: int (*create) (struct inode *,struct dentry *, umode_t, bool); 1817: int (*link) (struct dentry *,struct inode *,struct dentry *); 1818: int (*unlink) (struct inode *,struct dentry *); 1819: int (*symlink) (struct inode *,struct dentry *,const char *); 1820: int (*mkdir) (struct inode *,struct dentry *,umode_t); 1821: int (*rmdir) (struct inode *,struct dentry *); 1822: int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t); 1823: int (*rename) (struct inode *, struct dentry *, 1824: struct inode *, struct dentry *); 1825: void (*truncate) (struct inode *); 1826: int (*setattr) (struct dentry *, struct iattr *); 1827: int (*getattr) (struct vfsmount *mnt, struct dentry *, struct kstat *); 1828: int (*setxattr) (struct dentry *, const char *,const void *,size_t,int); 1829: ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t); 1830: ssize_t (*listxattr) (struct dentry *, char *, size_t); 1831: int (*removexattr) (struct dentry *, const char *); 1832: int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, 1833: u64 len); 1834: int (*update_time)(struct inode *, struct timespec *, int); 1835: int (*atomic_open)(struct inode *, struct dentry *, 1836: struct file *, unsigned open_flag, 1837: umode_t create_mode, int *opened); 1838: } ____cacheline_aligned;
p->files->fd_array[fd]
の struct file を表
す。
linux-3.6.8/include/linux/sched.h 1234: struct task_struct { ... 1400: struct files_struct *files; ... 1592: }; linux-3.6.8/include/linux/fdtable.h 66: struct files_struct { ... 80: struct file __rcu * fd_array[NR_OPEN_DEFAULT]; 81: };
図? task_struct、ファイル記述子、file構造体、その他
linux-3.6.8/fs/read_write.c 462: SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count) 463: { 464: struct file *file; 465: ssize_t ret = -EBADF; 466: int fput_needed; 467: 468: file = fget_light(fd, &fput_needed); 469: if (file) { 470: loff_t pos = file_pos_read(file); 471: ret = vfs_read(file, buf, count, &pos); 472: file_pos_write(file, pos); 473: fput_light(file, fput_needed); 474: } 475: 476: return ret; 477: }
linux-3.6.8/fs/read_write.c 366: ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos) 367: { 368: ssize_t ret; 369: 370: if (!(file->f_mode & FMODE_READ)) 371: return -EBADF; 372: if (!file->f_op || (!file->f_op->read && !file->f_op->aio_read)) 373: return -EINVAL; 374: if (unlikely(!access_ok(VERIFY_WRITE, buf, count))) 375: return -EFAULT; 376: 377: ret = rw_verify_area(READ, file, pos, count); 378: if (ret >= 0) { 379: count = ret; 380: if (file->f_op->read) 381: ret = file->f_op->read(file, buf, count, pos); 382: else 383: ret = do_sync_read(file, buf, count, pos); 384: if (ret > 0) { 385: fsnotify_access(file); 386: add_rchar(current, ret); 387: } 388: inc_syscr(current); 389: } 390: 391: return ret; 392: }
linux-3.6.8/fs/ext4/file.c 307: const struct file_operations ext4_file_operations = { 308: .llseek = ext4_llseek, 309: .read = do_sync_read, 310: .write = do_sync_write, 311: .aio_read = generic_file_aio_read, 312: .aio_write = ext4_file_write, 313: .unlocked_ioctl = ext4_ioctl, 314: #ifdef CONFIG_COMPAT 315: .compat_ioctl = ext4_compat_ioctl, 316: #endif 317: .mmap = ext4_file_mmap, 318: .open = ext4_file_open, 319: .release = ext4_release_file, 320: .fsync = ext4_sync_file, 321: .splice_read = generic_file_splice_read, 322: .splice_write = generic_file_splice_write, 323: .fallocate = ext4_fallocate, 324: }; 326: const struct inode_operations ext4_file_inode_operations = { ... 337: }; linux-3.1.3/fs/ext4/super.c 1256: static const struct super_operations ext4_sops = { ... 1275: };
linux-3.6.8/fs/ext4/ext4.h 818: struct ext4_inode_info { ... 878: struct inode vfs_inode; ... 930: }; 1304: static inline struct ext4_inode_info *EXT4_I(struct inode *inode) 1305: { 1306: return container_of(inode, struct ext4_inode_info, vfs_inode); 1307: } linux-3.6.8/include/linux/kernel.h 684: /** 685: * container_of - cast a member of a structure out to the containing structure 686: * @ptr: the pointer to the member. 687: * @type: the type of the container struct this is embedded in. 688: * @member: the name of the member within the struct. 689: * 690: */ 691: #define container_of(ptr, type, member) ({ \ 692: const typeof( ((type *)0)->member ) *__mptr = (ptr); \ 693: (type *)( (char *)__mptr - offsetof(type,member) );} )
図? Ext4 ファイルシステムで使う構造体 ext4_inode_info での struct inode の保持
ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos) { .... ret = rw_verify_area(WRITE, file, pos, count); if (file->f_op->/*空欄(a)*/) ret = file->f_op->/*空欄(b)*/(/*空欄(c)*/, buf, count, pos); ... } return ret; }