dentryinode

Dentryinode is an informal expression used to describe the link between a directory entry (dentry) and the inode that represents a file in the virtual file system (VFS) of Unix-like systems. The dentry maps a file name within a directory to the corresponding inode, while the inode holds the file’s metadata and data blocks. There is no single object named dentryinode; the term highlights their combined role in locating and describing files.

Dentry: The dentry is a cached pathname component in the VFS. It records the file name, a link to its parent directory, and, when resolved, a pointer to the inode. Dentries are stored in the dcache to speed lookups and can be positive (pointing to an inode) or negative (the name does not exist). They are reference counted and participate in path operations such as lookup and rename.

Inode: The inode is the filesystem’s metadata object for a file or directory. It contains attributes such as permissions, ownership, size, timestamps, and pointers to the data blocks. Multiple dentries may refer to the same inode in the case of hard links; when the last hard link is removed, the filesystem may reclaim the inode.

Relationship and lifecycle: During path resolution, the VFS checks the dcache for a matching dentry. If found, it uses the dentry’s inode pointer; if not, it creates a new dentry and binds it to the inode after a filesystem lookup. Dentry and inode reference counting, locking, and caching ensure consistency across operations like create, rename, and unlink. Negative dentries prevent repeated failed lookups; inodes persist while referenced.