Summary: Linux 4.4 has not been released
1. Prominent features
2. Drivers and architectures
All the driver and architecture-specific changes can be found in the [http://kernelnewbies.org/Linux_4.4-DriversArch Linux_4.4-DriversArch] page
3. Core (various)
4. File systems
- XFS
Add per-filesystem stats in /sys/fs/xfs/<block>/stats/stats, and a stats_clear file to clear them. Also, the global stats that are currently present in /proc are duplicated in /sys/fs/xfs/stats/stats (along with a stats_clear file) [https://git.kernel.org/torvalds/c/bb230c124730f21eea13deab433f9f8fc96bd5f3 commit], [https://git.kernel.org/torvalds/c/225e4635580ce9fb12f8a2dc88473161cd64dbf6 commit], [https://git.kernel.org/torvalds/c/ff6d6af2351caea7db681f4539d0d893e400557a commit]
- CIFS
Allow duplicate extents (cp --reflink) in SMB3.0 not just SMB3.1.1 [https://git.kernel.org/torvalds/c/ca9e7a1c85594f61d7ffb414071e6cae82eae23a commit]
Add resilienthandles mount parameter. Since many servers (Windows clients, and non-clustered servers) do not support persistent handles but do support resilient handles, allow the user to specify a mount option "resilienthandles" in order to get more reliable connections and less chance of data loss (at least when SMB2.1 or later). Default resilient handle timeout (120 seconds to recent Windows server) is used [https://git.kernel.org/torvalds/c/592fafe644bf3a48b9e00e182a67d301493634fc commit]
Add support for persistent handles, which are like durable file handles with strong guarantees [https://git.kernel.org/torvalds/c/b2a3077414fd6ff1de8972ea55e91f27bcabd913 commit], [https://git.kernel.org/torvalds/c/f16dfa7cd1b588e5d7ef4b5a19ee579f11b7a41f commit], [https://git.kernel.org/torvalds/c/b618f001a20e44f691dd0e2ffea651a40a651871 commit]
Allow copy offload (CopyChunk) across shares [https://git.kernel.org/torvalds/c/7b52e2793a58af61b5d349c2c080437a437a4edb commit]
5. Memory management
6. Block layer
Add Persistent Reservations support. It includes a user space interface for simplified Persistent Reservations which map to block devices that support these (only SCSI for now). Persistent Reservations allow restricting access to block devices to specific initiators in a shared storage setup [https://git.kernel.org/torvalds/c/bbd3e064362e5057cc4799ba2e4d68c7593e490b commit], [https://git.kernel.org/torvalds/c/924d55b06347d813b38c51e75ce1a6666c113933 commit], [https://git.kernel.org/torvalds/c/71cdb6978a80f9f6c51bef0622388c1414c2fe32 commit]
Add support for polling for specific IO to complete. This will be combined with request latency tracking later, so that the kernel can make qualified decisions about when to poll and when not to. For now, for benchmark purposes, a sysfs file (io_poll) is added to control whether polling is enabled or not [https://git.kernel.org/torvalds/c/05229beeddf7e75e2e616ddaad4b70e7fca9528d commit]
Export integrity data interval size in /sys/block/<disk>/integrity/protection_interval_bytes , so that apps can tell whether the interval is different from the device's logical block size [https://git.kernel.org/torvalds/c/4c241d08dbfcbdc7a949b91d72707a289d464954 commit]
7. Cryptography
8. Security
9. Tracing and perf tool
10. Networking