Emc Corporation

Emc IP Holding Company LLC

Michael D Schouten

Jean-Pierre Bono

Morgan A Clark

Philippe Armangau

William C Davenport

Feng Zhang

Alexander S Mathews

Yingchao Zhou

Srinivasa Rao Vempati

Marc DeSouter

Michael Scheer

Qi Mao

Yunfei Chen

Praveen S Solanki

A technique for managing storage of directories in a file system performs a testing operation on a file-system block of a directory file. The testing operation determines whether the file-system block contains any directory element that identifies a currently-present content object in the directory. In response to the testing operation determining that the file-system block contains no directory element that identifies any currently-present content object, the file system performs a hole-punching operation on the file-system block, removing the block from the directory file and freeing the block for other use.

Scavenging directories for free space

Described are methods, systems, and apparatus, including computer program products for de-duplicating access control lists (ACLs). A first ACL associated with a first computer file is received. A first checksum based at least in part on the first ACL is calculated. One or more directory entries based on the first checksum are retrieved from a de-duplication directory, wherein each directory entry of the one or more directory entries comprises a reference to an ACL and a name comprising the first checksum. A directory entry of the one or more directory entries is identified that references a second ACL that specifies the same permissions as the first ACL. A reference to the second ACL of the directory entry is added to the first computer file.

De-duplication of access control lists

A method is used in recovering file mapping information in file systems. Metadata of a file of a file system is evaluated. Mapping information associating the file to a file system hierarchy of the file system is missing a reference to an inode of the file. Based on the evaluation, the mapping information is updated for including the file to the file system hierarchy of the file system.

Recovering file mapping information in file systems

An improved technique involves providing a naming scheme that uses a unique numeric identifier associated with a particular naming protocol. Along these lines, when a storage processor receives a first name of a file that conforms to a first naming protocol, the storage processor places the first name and an inode number corresponding to the file in a directory entry. The storage processor associates this entry with a unique numeric identifier by which the entry can be located within the directory. Based on this unique identifier, the storage processor is configured to generate the second name that conforms to the second naming protocol.

Implied M83 names in alternate name generation in directories supporting multiple naming protocols

An improved technique involves providing a pair of inode numbers in a directory entry for a file in a directory of a target file system. Along these lines, the target file system writes a first inode number and a second inode number to the directory entry for the file. While the client has not yet remounted its file system, that client may continue to use the file handle provided for the original file system. The data storage system continues to refer to a mapping table that cross-references initial inode numbers to target ones, at some cost in performance. Nevertheless, the client has an option to remount the file system at a time that is convenient to the client, so that the client may obtain a new handle. The client may subsequently use the new file handle to access the file.

Recovering performance of a file system post-migration

For enabling a fast reverse lookup of parent directories storing records of hard links to a specified regular file, a file system manager maintains a hard link database (HLDB) storing information for addressing hard links to the regular files having multiple hard links. The HLDB contains a corresponding HLDB file for each regular file having multiple hard links. In a preferred implementation, the inode of each regular file stores the addressing information for one hard link to the regular file, a corresponding HLDB file stores the addressing information for other hard links to the regular file, each HLDB file is a directory accessed by invoking file system manager directory access routines, and the HLDB has a directory tree providing a multi-level hash index for searching the HLDB given the inode number of a regular file.

Inode to pathname support with a hard link database

An improved technique for managing directory objects accessible via multiple protocols includes storing directory entry components in leaves of an extendible hash tree. Each directory entry component includes an indication of each protocol to which the name conforms, thereby allowing the same directory entry component to be used for representing directory object names in multiple protocols. Efficiency is improved, especially for large directory structures, by keeping related information about directory objects together, in the same directory entry components and/or in the same leaves of the extendible hash tree.

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Lake Katrine, NY, United States of America

Michael D Schouten