11. Anatomy of stat system call sys_stat(path, buf) { dentry = namei(path); if ( dentry == NULL ) return -ENOENT; inode = dentry->d_inode; rc =inode->i_op->i_permission(inode); if ( rc ) return -EPERM; rc = inode->i_op->i_getattr(inode, buf); dput(dentry); return rc; } Establish VFS data Call into inode layer of filesystem Call into inode layer of filesystem
12. Anatomy of fstatfs system call sys_fstatfs(fd, buf) { /* for things like “df” */ file = fget(fd); if ( file == NULL ) return -EBADF; superb = file->f_dentry->d_inode->i_super; rc = superb->sb_op->sb_statfs(sb, buf); return rc; } Call into superblock layer of filesystem Translate fd to VFS data structure
19. What’s inside an inode - 1 list_head i_hash list_head i_list list_head i_dentry int i_count long i_ino int i_dev {m,a,c}time {u,g}id mode size n_link caching Identifies file Usual stuff
20. What’s inside an inode -2 superblock i_sb inode_ops i_op wait objects, semaphore lock vm_area_struct pipe/socket info page information union { ext2fs_inode_info i_ext2 nfs_inode_info i_nfs coda_inode_info i_coda ..} u Which FS For mmap, networking waiting FS Specific info: blockno’s fids etc
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22. Inode Cache Dirty inodes Inode_hashtable 1. iget: if i_count>0 ++ 2. iput: if i_count>1 - - sss_write_inode (sync one) Used inodes Unused inodes sss_read_inode (iget) sss_clear_inode (freeing inos) or sss_delete_inode (iput) media fs only (mark_inode_dirty) 3. free_inodes 4. syncing inodes Players: Fs storage Fs storage Fs storage
23. Sales Red Hat Software sold 240,000 copies of Red Hat Linux in 1997 and expects to reach 400,000 in 1998. Estimates of installed servers (InfoWorld): - Linux: 7 million - OS/2: 5 million - Macintosh: 1 million
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27. Dentry associated lists d_alias chains place : d_instantiate remove : dentry_iput inode I_dentry list head d_child chains place : d_alloc remove : d_prune, d_invalidate, d_put inode i_dentry list head = d_inode pointer = d_parent pointer dentry inode relationship dentry tree relationship Legend: inode dentry