Linux 5.15 with fresh NTFS driver and SMB server
The new kernel facilitates data exchange with Windows with a stable and secure NTFS driver. It also includes the SMB server in the kernel.
In the night from Sunday to Monday, Linus Torvalds has released the Linux kernel in version 5.15. The new version is not just a maintenance release, but brings new features. Especially for cross-platform data exchange with other systems, the release offers a rich plus in the form of a new NTFS driver. Other important innovations: Samba in the kernel and optimizations in the file system area. In the following, we take a brief look at the highlights in Linux 5.15.
Stable NTFS thanks to Paragon driver
Paragon Software GmbH has contributed a driver for the NTFS file system in Linux 5.15. It replaces the old kernel NTFS driver. Since this only controlled read access, most users had previously relied on the FUSE driver (Filesystem in USErspace) NTFS-3G. However, its incompletely implemented NTFS specification could leave file systems damaged in crashes.
The new driver fully implements NTFS in version 3.1. This also includes the journal replay, which can restore the file system as far as possible in the event of a crash. Paragon intends to maintain the driver in the Linux kernel in the future. New features are already planned for the next Linux versions.
We had already dedicated a longer report to Paragon’s NTFS3 driver in September shortly after its integration into the kernel:
KSMBD: Samba in the kernel
With KSMBD, Linux 5.15 introduces a new module that moves the SMB3 protocol into the kernel. The SMB (Server Message Block) or CIFS (Commin Internet File System) protocol has so far been the domain of Samba under Linux. With the new kernel module, the kernel developers are creating an optimized SMB server, which will be trimmed for performance and data throughput. It is not supposed to be a competitor to Samba, but a supplement.
KSMBD only provides the server; clients are reserved for Samba. In addition, KSMBD only speaks SMB version 3; clients with earlier SMB versions cannot connect to the kernel SMB. Likewise, old insecure authentication protocols like NTLMv1 are left out. This creates a lean server, which in the future - due to its proximity to the hardware in the kernel - should bring more features to Linux. For example, “SMB Direct” is at the top of the agenda for future enhancements. It is supposed to increase the performance of the SMB server considerably.
KSMBD aims at high data throughput. Samba, on the other hand, is broadly and openly positioned and scores with the tools, the various security services and the connection to LDAP and Active Directory.
File systems optimized
Linux 5.15 has made significant improvements to the file systems. Ext4 shines with faster handling of orphan files and also increases performance from the delalloc write buffer.
XFS has also seen performance improvements. In addition, the file system can now handle data beyond the year 2038. This “feature” was already available, but was previously classified as “experimental”. Now it is considered stable for productive use. Another novelty in XFS: As of now, it is no longer possible to switch off the so-called quota accounting. Although the corresponding enforcement can be shut down, the “accounting” now continues to run in the background - albeit without consequences. Reason for this solution were not comprehensible crashes when switching off the quotas.
btfs follows suit with the so-called ID-Mapped Mounts, which we had discussed in detail in our Linux 5.12 release. In addition, it can now handle fs-verify, a generic layer for transparent integrity and authenticity protection of read-only files. This brings it in line with ext2 and F2FS, which have offered this feature for some time.
Other new features and even more kernel details
Linux 5.15 removes the LightNVM subsystem, considered obsolete and replaced by newer NVMe (Non-Volatile Memory Express) standards, which previously allowed direct access to SSDs without an emulation layer. The support for Apple’s M1 was further expanded with Linux 5.15, but is not yet considered production stable.
Furthermore, the data access monitor DAMON was included in the kernel. And also in the memory management Linux 5.15 brings innovations: It introduces the system call process_mrelease(). cgroup receives support for SCHED_IDLE. SCHED_IDLE tasks run only if no other tasks are ready for execution. However, within cgroup, the associated tasks retain their weights.
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