Linux 4.1 has been released on Sun, 21 Jun 2015

Summary: This release adds support for Ext4 encryption, experimental support for managing clustered raid arrays, a new device mapper target that logs all writes to the devices and allows to replay them, a driver to turn the memory in persistent memory systems in a block device, support for disabling multi-user support, support for the Multiprotocol Label Switching which routes packets based on path labels rather than long network addresses, allow to attach BPF programs to kprobes for better probing, ACPI support for the ARM64 architecture, and a virtual GEM driver that allows improved software rasterizers. There are also new drivers and many other small improvements.

1. Prominent features

1.1. Ext4 encryption support

Linux already has support for data encryption facilities such as dm-crypt or ecryptfs, but they have performance and memory consumption costs. The Ext4 filesystem now supports encryption support: both data and file names can be encrypted with a key provided by the user. The key is used for the files of a directory and all the subdirectories. When reading, if a valid key is not provided, only the encrypted file names can be read, but not the decrypted ones, and the encrypted data can not be read.

To use this feature, you need e2fsprogs version 1.43, the keyutils software. A small howto can be found here.

For details about the internal design of this feature, see here

Recommended LWN article: Ext4 encryption

Code: (merge)

1.2. Experimental cluster support for MD

This release adds clustering support for MD (Linux software RAID). Cluster MD is a shared-device RAID for a cluster. It enables locking and synchronization across multiple systems on the cluster, so all nodes in the cluster can access the MD devices simultaneously, bringing the redundancy (and uptime) of RAID levels across the nodes of the cluster. Currently, the implementation is limited to RAID1 but with further work (and some positive feedback), it could be extend to other RAID levels. The code in this version is is high experimental and not recommended to use except for experimentation.

Small howto: howto Design Documentation: commit

Code: merge

1.3. Device mapper: new target that logs writes

The device mapper layer introduces a new target that log all write operations to a separate device, for later replay. The motivation behind this is to give file system developers a tool to verify that the file system is always consistent at particular points in the life of a file system by allowing them to replay the log in a variety of ways

Code: commit

1.4. Single user support

It may be strange that a multi-user system such as Linux would consider a return to the past, such a single-user opearting mode, a feature. But it turns out that embedded targets that want to make Linux as small as possible and don't care about multi-user separation. In this release, it's possible to configure the kernel without multi-user support, under this option UID and GID are zero in any possible case and processes always have all capabilities

Code: commit

Recommended LWN article: Linux as a single-user system

1.5. Virtual GEM driver for improved software rasterizers

The vGEM (virtual graphics memory manager) DRM driver allows to import a GEM object from other graphic drivers and mmap them to user-space, which can use it as a GEM shared memory handler. This makes it a lot easier to do certain things when you have no GPU but still have to deal with DRI expectations. It's used by Mesa's software renderer for enhanced performance.

Code: commit

1.6. Block device for persistent memory

There are new types of memory that can be accessed almost as fast as RAM, but don't lose data after powering off the system. This kind of memory is called persistent memory. In this release Linux includes PMEM, a driver that presents a reserved range of memory as a block device, which can be used by file systems. This is useful for developing with non-volatile DIMMs, and can be used with volatile memory as a development platform.

Recommended LWN article: Persistent memory support progress

Code: commit

1.7. Multiprotocol Label Switching

This release adds support for Multiprotocol Label Switching (MPLS). MPLS is a scalable, protocol-independent networking transport that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table, because packet-forwarding decisions are made solely on the contents of the label, without the need to examine the packet itself. The labels identify virtual links (paths) between distant nodes rather than endpoints. MPLS can encapsulate packets of various network protocols.

Code: (merge), (merge)

1.8. BPF programs can be attached to kprobes

In this release, Linux allow to attach small BPF programs to kprobes, providing a safe way to execute user-defined BPF byte-code programs without being able to crash or hang the kernel in any way. The BPF engine makes sure that such programs have a finite execution time and that they cannot break out of their sandbox. This allows user-defined instrumentation on a live kernel image that can never crash, hang or interfere with the kernel negatively. In this release, it's limited to root only

Code: commit

1.9. ACPI support for the ARM64 architecture

For a long time, ACPI has mostly been a x86 feature. Despite the controversies, some parts of the ARM world have been pushing for ACPI support. In this release, Linux adds preliminary ACPI 5.1 support to the arm64 architecture.

Documentation: Documentation/arm64/arm-acpi.txt

Recommended LWN article: ACPI for ARM?

Merge: commit

2. Drivers and architectures

3. Core (various)

4. File systems

5. Block

6. Cryptography

7. Memory management

8. Security

9. Tracing & perf

10. Virtualization

11. Networking

12. List of merges

13. Other news sites

KernelNewbies: Linux_4.1 (last edited 2017-12-30 01:30:21 by localhost)