Linux 4.0 [https://lkml.org/lkml/2015/4/12/178 has been released] on Sun, 12 Apr 2015.

This page is not complete. It will be completed in the next few days. Meanwhile, you can read about Linux 4.0 in other sites:

• LWN: [http://lwn.net/Articles/632761/ The merge window opens], [http://lwn.net/Articles/633096/ merge window part 2], [http://lwn.net/Articles/634471/ The end of the 4.0 merge window]

1. File systems

• XFS

  • Adds support for sys_renameat2() [http://git.kernel.org/linus/d31a1825450062b85282b4afed1c840fd306d012 commit]

  • Remove deprecated sysctls xfsbufd_centisecs and age_buffer_centisecs [http://git.kernel.org/linus/64af7a6ea5a4c7e12ae79415250d054424b7e0c2 commit]

• UBIFS

  • Add security.* XATTR support for the UBIFS [https://git.kernel.org/linus/d7f0b70d30ffb9bbe6b8a3e1035cf0b79965ef53 commit]

  • Add xattr support for symlinks [https://git.kernel.org/linus/895d9db253a0b0b1f8a6e635fb2460d80bf72d5a commit]

• OCFS2

  • Add a mount option journal_async_commit on ocfs2 filesystem. When this feature is opened, journal commit block can be written to disk without waiting for descriptor blocks, which can improve journal commit performance. Using the fs_mark benchmark, using journal_async_commit shows a 50% improvement [https://git.kernel.org/linus/1dfeb768475dfded66bba03a1744c2e8141d3429 commit]

  • Currently in case of append O_DIRECT write (block not allocated yet), ocfs2 will fall back to buffered I/O. This has some disadvantages. In this version, the direct I/O write doesn't fallback to buffer I/O write any more because the allocate blocks are enabled in direct I/O now [https://git.kernel.org/linus/026749a86ebff68cb2accdcd29872d36ac148920 commit], [https://git.kernel.org/linus/160cc266639d4213c15c103074561c1b44ffe691 commit], [https://git.kernel.org/linus/18d585f0f2d4c9dc7dfe6e69dcae4933d5a428c9 commit]

2. Block

• blk-multiqueue: Add support for tag allocation policies and make libata use this blk-mq tagging, instead of rolling their own [http://git.kernel.org/linus/24391c0dc57c3756a219defaa781e68637d6ab7d commit], [http://git.kernel.org/linus/12cb5ce101abfaf74421f8cc9f196e708209eb79 commit]

• Ported to blk-multiqueue

  • loop: Add blk-mq support, which greatly improves performance for sequential and random reads [https://git.kernel.org/linus/b5dd2f6047ca108001328aac0e8588edd15f1778 commit]

  • Device-mapper [https://git.kernel.org/e5863d9ad754926e7d3f38b43ac8bd48ef73b097 commit]

  • rbd [https://git.kernel.org/linus/7ad18afad02f9802f1eeade91cf880b97e7a9902 commit]

  • UBI [https://git.kernel.org/linus/ff1f48ee3bb3af226f1f8993af0103794b4d4eab commit]

• UBI: Implement UBI_METAONLY, a new open mode for UBI volumes, it indicates that only meta data is being changed [https://git.kernel.org/linus/fafdd2bf2638157670f28462b641150d16dbaeca commit]

3. Core (various)

• rcu: Optionally run grace-period kthreads at real-time priority. Recent testing has shown that under heavy load, running RCU's grace-period kthreads at real-time priority can improve performance and reduce the incidence of RCU CPU stall warnings [https://git.kernel.org/linus/a94844b22a2e2b9155bbc0878c507850477221c2 commit]

• GDB scripts for debugging the kernel. If you load vmlinux into gdb with the option enabled, the helper scripts will be automatically imported by gdb as well, and additional functions are available to analyze a Linux kernel instance. See [https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/gdb-kernel-debugging.txt Documentation/gdb-kernel-debugging.txt] for further details [https://git.kernel.org/linus/3ee7b3fa2cd0182628cca8d9bb5ce2d4722e8dc5 commit]

4. Memory management

• cgroups: Per memory cgroup slab shrinkers [https://git.kernel.org/linus/cb731d6c62bbc2f890b08ea3d0386d5dad887326 commit]

• slub: optimize memory alloc/free fastpath by removing preemption on/off [https://git.kernel.org/linus/9aabf810a67cd97e2d1a48f0bab338b7680f1929 commit]

• Make /dev/mem an optional device [https://git.kernel.org/linus/73f0718e74e25ac7381450a7a21257b8f26f43f0 commit]

• Add support for resetting peak RSS, which can be retrieved from the VmHWM field in /proc/pid/status, by writing "5" to /proc/pid/clear_refs [http://git.kernel.org/linus/695f055936938c674473ea071ca7359a863551e7 commit]

• Show page size in /proc/<pid>/numa_maps as "kernelpagesize_kB" field to help identifying the size of pages that are backing memory areas mapped by a given task. This is specially useful to help differentiating between HUGE and GIGANTIC page backed VMAs [http://git.kernel.org/linus/198d1597cc5a12d04af18b69338a5b1d66ee7020 commit]

• geneve: Add Geneve GRO support [http://git.kernel.org/linus/a4c9ea5e8fec680134d22aa99b54d1cd8c226ebd commit]

• zsmalloc: add statistics support [https://git.kernel.org/linus/0f050d997e275cf0e47ddc7006284eaa3c6fe049 commit]

• Incorporate read-only pages into transparent huge pages [https://git.kernel.org/linus/10359213d05acf804558bda7cc9b8422a828d1cd commit]

• memcontrol cgroup: Introduce the basic control files to account, partition, and limit memory using cgroups in default hierarchy mode. The old interface will be maintained, but a clearer model and improved workload performance should encourage existing users to switch over to the new one eventually [https://git.kernel.org/linus/241994ed8649f7300667be8b13a9e04ae04e05a1 commit]

• Replace remap_file_pages() syscall with emulation [https://git.kernel.org/linus/c8d78c1823f46519473949d33f0d1d33fe21ea16 commit]

5. Virtualization

• KVM: Add generic support for page modification logging, a new feature in Intel "Broadwell" Xeon CPUs that speeds up dirty page tracking [https://git.kernel.org/linus/ba0513b5b8ffbcb0cc89e2f172c0bcb70497ba2e commit]

• vfio: Add device request interface indicating that the device should be released [https://git.kernel.org/linus/6140a8f5623820cec7f56c63444b9551d8d35775 commit]

• vmxnet3: Make Rx ring 2 size configurable by adjusting rx-jumbo parameter of ethtool -G [https://git.kernel.org/linus/53831aa12538f8753fb77b7ab6408cce54973b30 commit]

• virtio_net: add software timestamp support [https://git.kernel.org/linus/074c3582192b6cb340510b2a6e4579e78f671dcf commit]

• virtio_pci: modern driver [https://git.kernel.org/linus/1fcf0512c9c870e78e1c9898ecb9458593403466 commit], add an options to disable legacy driver [https://git.kernel.org/linus/46506da5f365efe7fe3e4c9da73ab679c0382fac commit], [https://git.kernel.org/linus/ac399d8f39a860655961660efa5c67e7f3c47912 commit]

6. Cryptography

• aesni: Add support for 192 & 256 bit keys to AES-NI RFC4106 [https://git.kernel.org/linus/e31ac32d3bc27c33f002e0c9ffd6ae08b65474e6 commit]

• algif_rng: add random number generator support [https://git.kernel.org/linus/5afdfd22e6ba2260129a2a7113ab0916339c4205 commit]

• octeon: add MD5 module [https://git.kernel.org/linus/1953c22f53747035b28c36dbb337ac3c10902644 commit]

• qat: add support for CBC(AES) ablkcipher [https://git.kernel.org/linus/338e84f3a9740ab3582c8b6bc5a1a027794dac72 commit]

7. Security

• Add security hooks to the Android Binder that enable security modules such as SELinux to implement controls over Binder IPC. The security hooks include support for controlling what process can become the Binder context manager, invoke a binder transaction/IPC to another process, transfer a binder reference to another process , transfer an open file to another process. These hooks have been included in the Android kernel trees since Android 4.3 [https://git.kernel.org/linus/79af73079d753b2d04e46f7445716d3b5f914dbd commit]

• Smack: secmark support for netfilter [https://git.kernel.org/linus/69f287ae6fc8357e0bc561353a2d585b89ee8cdc commit]

• TPM 2.0 support [https://git.kernel.org/linus/7a1d7e6dd76a2070e2d86826391468edc33bb6d6 commit], [https://git.kernel.org/linus/30fc8d138e9123f374a3c3867e7c7c5cd4004941 commit], [https://git.kernel.org/linus/aec04cbdf7231c1b0da76172de82dfa2388a80d7 commit]

• Device class for TPM, sysfs files are moved from /sys/class/misc/tpmX/device/ to /sys/class/tpm/tpmX/device/ [https://git.kernel.org/linus/313d21eeab9282e01fdcecd40e9ca87e0953627f commit]

8. Networking

• TCP: Add the possibility to define a per route/destination congestion control algorithm. This opens up the possibility for a machine with different links to enforce specific congestion control algorithms with optimal strategies for each of them based on their network characteristics [https://git.kernel.org/linus/81164413ad096bafe8ad1068f3f095a7dd081d8b commit]

• Mitigate TCP "ACK loop" DoS scenarios by rate-limiting outgoing duplicate ACKs sent in response to incoming "out of window" segments. For more details, see [https://git.kernel.org/linus/f06535c599354816cfbc653ce8965804c7385c61 merge]. Code: [https://git.kernel.org/linus/032ee4236954eb214651cb9bfc1b38ffa8fd7a01 commit], [https://git.kernel.org/linus/a9b2c06dbef48ed31cff1764c5ce824829106f4f commit], [https://git.kernel.org/linus/f2b2c582e82429270d5818fbabe653f4359d7024 commit], [https://git.kernel.org/linus/4fb17a6091674f469e8ac85dc770fbf9a9ba7cc8 commit]

• udpv6: Add lockless sendmsg() support, thus allowing multiple threads to send to a single socket more efficiently [https://git.kernel.org/linus/03485f2adcde0c2d4e9228b659be78e872486bbb commit]

• ipv4: Automatically bring up DSA master network devices, which allows DSA slave network devices to be used as valid interfaces for e.g: NFS root booting by allowing kernel IP auto-configuration to succeed on these interfaces [https://git.kernel.org/linus/728c02089a0e3eefb02e9927bfae50490f40e72e commit]

• ipv6: Add sysctl entry(accept_ra_mtu) to disable MTU updates from router advertisements [https://git.kernel.org/linus/c2943f14534bdc4230f4da6dcd4ea03c5d8c8162 commit]

• vxlan: Implement supports for the [https://tools.ietf.org/html/draft-smith-vxlan-group-policy Group Policy VXLAN extension] to provide a lightweight and simple security label mechanism across network peers based on VXLAN. It allows further mapping to a SELinux context using SECMARK, to implement ACLs directly with nftables, iptables, OVS, tc, etc [https://git.kernel.org/linus/3511494ce2f3d3b77544c79b87511a4ddb61dc89 commit]

• vxlan: Add support for remote checksum offload in VXLAN. It is described [https://tools.ietf.org/html/draft-herbert-vxlan-rco-00 here]. [https://git.kernel.org/linus/dfd8645ea1bd91277f841e74c33e1f4dbbede808 commit]

net: openvswitch: Support masked set actions. [https://git.kernel.org/linus/83d2b9ba1abca241df44a502b6da950a25856b5b commit]

• Infiniband: Add support for extensible query device capabilities verb to allow adding new features [https://git.kernel.org/linus/02d1aa7af17ef0e0655745ce32cab369ed040a67 commit]

• Layer 2 Tunneling Protocol (l2tp): multicast notification to the registered listeners when the tunnels/sessions are created/modified/deleted [https://git.kernel.org/linus/33f72e6f0c67f673fd0c63a8182dbd9ffb8cf50b commit]

• SUNRPC: Set SO_REUSEPORT socket option for TCP connections to bind multiple TCP connections to the same source address+port combination [https://git.kernel.org/linus/4dda9c8a5e34773b290c6b5938ccb36e7fcdf35c commit]

• tipc: involve namespace infrastructure [https://git.kernel.org/linus/c93d3baa24095887005647984cff5de8c63d3611 commit]

• 802.15.4: introduce support for cca settings [https://git.kernel.org/linus/ba2a9506a76450568cbc0d51626d94cf8528c0c7 commit]

• Wireless

  • Add new GCMP, GCMP-256, CCMP-256, BIP-GMAC-128, BIP-GMAC-256, and BIP-CMAC-256 cipher suites. These new cipher suites were defined in IEEE Std 802.11ac-2013 [https://git.kernel.org/linus/cfcf1682c4ca8f601a4702255958e0b1c9aa12cc commit], [https://git.kernel.org/linus/56c52da2d554f081e8fce58ecbcf6a40c605b95b commit], [https://git.kernel.org/linus/8ade538bf39b1ee53418528fdacd36b8e65621b9 commit], [https://git.kernel.org/linus/2b2ba0db1c820d04d5143452d70012cd44d7b578 commit], [https://git.kernel.org/linus/00b9cfa3ff38401bd70c34b250ca13e5ea347b4a commit]

  • New NL80211_ATTR_NETNS_FD which allows to set namespace via nl80211 by fd [https://git.kernel.org/linus/4b681c82d2f9bef121c912ffcaac89a004af3f2c commit]

  • Support per-TID station statistics [https://git.kernel.org/linus/6de39808cf1dd7b02bf42e7d8695d80f5eaf645d commit]

  • Allow including station info in delete event [https://git.kernel.org/linus/cf5ead822d5db2d276616ccca91f00eb3b855db2 commit], [https://git.kernel.org/linus/6f7a8d26e2668e00de524d3da0122a4411047dd2 commit]

  • Allow usermode to query wiphy specific regdom [https://git.kernel.org/linus/ad30ca2c03cecfb1b0749874bdceead269542de6 commit]

• bridge

  • offload bridge port attributes to switch ASIC if feature flag set [https://git.kernel.org/linus/68e331c785b85b78f4155e2ab6f90e976b609dc1 commit]

  • Support for allowing userspace to pack multiple vlans and VLAN ranges in setlink and dellink requests for improved performance [https://git.kernel.org/linus/bdced7ef7838c1c4aebe9f295e44b7f0dcae2109 commit]

  • Add ability to enable TSO [https://git.kernel.org/linus/f902e8812ef657c6cf744ac25e21865217155460 commit]

• Near Field Communication (NFC)

  • HCI over NCI protocol support (Some secure elements only understand HCI and thus we need to send them HCI frames) [https://git.kernel.org/linus/11f54f228643d0248ec00ce8c9fb8d872f87e7b8 commit]

  • NCI NFCEE (NFC Execution Environment, typically an embedded or external secure element) discovery and enabling/disabling support [https://git.kernel.org/linus/8277f6937ae97c51ced5b54faa4934613c76999c commit], [https://git.kernel.org/linus/af9c8aa67d07adcd3b41fb2934af7af056eabecf commit], [https://git.kernel.org/linus/f7f793f31378d5e83276871339c2a8374b0e8657 commit], [https://git.kernel.org/linus/a41bb8448ebaebe1d0d9a268d340fad73c247e09 commit], [https://git.kernel.org/linus/4aeee6871e8c3b043ef02996db8ac70a1af8be92 commit], [https://git.kernel.org/linus/6095b0f07d9b1abd98484bc33b329e06a684115b commit], [https://git.kernel.org/linus/736bb9577407d3556d81c3c3cd57581cd3ae10ea commit]

  • NFC_EVT_TRANSACTION userspace API addition, it is sent through netlink in order for a specific application running on a secure element to notify userspace of an event [https://git.kernel.org/linus/447b27c4f29b510b98e99395120d635f009ed563 commit]

  • Tx timestamps are looped onto the error queue on top of an skb. This mechanism leaks packet headers to processes unless the no-payload options SOF_TIMESTAMPING_OPT_TSONLY is set. A new sysctl (tstamp_allow_data) optionally drops looped timestamp with data. This only affects processes without CAP_NET_RAW [https://git.kernel.org/linus/b245be1f4db1a0394e4b6eb66059814b46670ac3 commit], [https://git.kernel.org/linus/49ca0d8bfaf3bc46d5eef60ce67b00eb195bd392 commit], [https://git.kernel.org/linus/2368592365bc97e941d0c641a3ba24b06d2c469b commit]

• Bluetooth

  • Enable LE Data Length Extension feature from Bluetooth 4.2 specification [https://git.kernel.org/linus/a9f6068e0072839594d246089204644bffd2c988 commit]

  • Expose information in debugfs: Secure Simple Pairing [https://git.kernel.org/linus/6e07231a80de33a3721c971e560316d04db16de8 commit], debug keys usage setting [https://git.kernel.org/linus/0886aea6acd27006888c36bad1fa5f80dac1e171 commit], hardware error code [https://git.kernel.org/linus/5789f37cbc560aff45ff4d00673705eac92d3b4d commit], remote OOB information [https://git.kernel.org/linus/6858bcd073c9ff36f5d341dc6da011a53954fa9a commit]

  • HCI Read Stored Link Keys [https://git.kernel.org/linus/cb9627806ce898c436dc74252718e4a757b33bc3 commit], [https://git.kernel.org/linus/c2f0f979276fc4911cef5da2fc113f0daeda3ebc commit]

  • HCI Delete Stored Link Key [https://git.kernel.org/linus/48ce62c4fae7e817d9018020345bbe30a6b9c446 commit], [https://git.kernel.org/linus/a93661203641eb5e8aa9bbed8d9689e5d5dbe6b1 commit]

  • Support static address when BR/EDR has been disabled [https://git.kernel.org/linus/50b5b952b7c2bf2c75c257a62a6c456a0bbfdfa3 commit]

• tc: add BPF-based action. This action provides a possibility to execute custom BPF code [https://git.kernel.org/linus/d23b8ad8ab23f5a18b91e2396fb63d10f66b08d6 commit]

net: sched: Introduce connmark action [https://git.kernel.org/linus/22a5dc0e5e3e8fef804230cd73ed7b0afd4c7bae commit]

• Add Transparent Ethernet Bridging GRO support [https://git.kernel.org/linus/9b174d88c257150562b0101fcc6cb6c3cb74275c commit]

netdev: introduce new NETIF_F_HW_SWITCH_OFFLOAD feature flag for switch device offloads [https://git.kernel.org/linus/aafb3e98b27977148c8c86499684f8f5c3decfbb commit]

• netfilter: nft_compat: add ebtables support [https://git.kernel.org/linus/5191f4d82daf22b7ee9446f83527d2795e225974 commit]

  • network namespace: Add rtnl cmd to add and get peer netns ids. A user can define an id for a peer netns by providing a FD or a PID. These ids are local to the netns where it is added (i.e. valid only into this netns) [https://git.kernel.org/linus/0c7aecd4bde4b7302cd41986d3a29e4f0b0ed218 commit], [https://git.kernel.org/linus/d37512a277dfb2cef8a578e25a3246f61399a55a commit]

• openvswitch: Add support for checksums on UDP tunnels. [https://git.kernel.org/linus/b8693877ae016ac525d674d5d7a84ea0ea68ba60 commit]

• openvswitch: Support VXLAN Group Policy extension [https://git.kernel.org/linus/1dd144cf5b4b47e12438c2c6883925ce1a9b499f commit]