{"id":115726,"date":"2024-05-13T13:52:06","date_gmt":"2024-05-13T11:52:06","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/reliz-yadra-linux-6-9"},"modified":"2024-05-13T13:52:06","modified_gmt":"2024-05-13T11:52:06","slug":"reliz-yadra-linux-6-9","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/reliz-yadra-linux-6-9","title":{"rendered":"Release of Linux Kernel 6.9","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"
After two months of development, Linus Torvalds released the Linux kernel 6.9. Among the most notable changes are the dm-vdo module for deduplication and compression of block devices, a direct access mode for files in FUSE, support for creating pidfd for individual threads, the BPF token mechanism, Rust support on ARM64 systems, the classification of the Ext2 FS as deprecated, removal of the old NTFS driver, and support for the Intel FRED mechanism. <\/p>\n
The new version includes 15,680 fixes from 2,106 developers, with a patch size of 54 MB (the changes affected 11,825 files, adding 687,954 lines of code and removing 225,344 lines). The previous release contained 15,641 fixes from 2,018 developers, with a patch size of 44 MB. Approximately 42% of all changes presented in version 6.9 are related to device drivers, about 17% pertain to updating architecture-specific code, 13% are related to the network stack, 7% to file systems, and 4% to internal kernel subsystems. <\/p>\n
Key innovations in kernel 6.9: <\/p>\n
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Disk subsystem, input\/output, and file systems<\/b>\n
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A new dm-vdo (virtual data optimizer) handler has been added to the Device Mapper (DM), allowing for the realization of a virtual block device based on existing block devices with features such as deduplication of repeating data, data compression, exclusion of empty blocks, and increasing the size of the block device as needed (thin provisioning). These capabilities are implemented at the block device level and are independent of the file system used (for example, dm-vdo can automatically merge duplicate data and store information in a compressed format for any FS). Use of dm-vdo is supported for physical storage up to 256TB, and logical volumes can be created of up to 4PB. It is recommended to use lvm for managing vdo partitions. The VDO technology was developed by Permabit and was opened after its acquisition by Red Hat in 2017.\n
In the FUSE subsystem, used for implementing file systems in user space, an initial implementation of the 'passthrough' mode has been added, allowing direct access to file data at the kernel level, bypassing the user-space process, which can significantly enhance performance in certain situations. For example, FUSE implementations of file systems that operate in read-only mode and restrict access to files can return the contents of files from the original file system without passing them to the FUSE process.\n
The driver implementing the Ext2 file system has been marked as deprecated. The reason given is that the driver only supports 32-bit timestamps in inodes, which will overflow on January 19, 2038. It is recommended to use the ext4 driver instead, which supports Ext2 file systems and is fully compatible with them, but may use timestamps in Ext2 partitions that are not affected by the 2038 problem, provided the FS was created with inodes larger than 255 bytes (in the ext2 driver, 32-bit timestamps were used regardless of the inode size).\n
The old NTFS file system driver has been removed, and starting with version 5.15, it has been replaced by a new NTFS3 driver. Having two drivers implementing NTFS in the kernel has been deemed unnecessary, given that the old driver had not been updated for many years, is in a poor state, and can only operate in read-only mode.\n
Support for mapping user IDs of mounted file systems has been added to the zonefs and hugetlbfs file systems, which is used to map files of a certain user on a mounted foreign partition to another user in the current system.\n
In NFSv4, administrators have been given the ability to clear file open and locking states.\n
For the Ext4 file system, only bug fixes and updates to kunit tests are noted.\n
In Btrfs, the transition of functions to the use of page folios has continued.\n
In the XFS file system, work has continued on implementing the ability to use the fsck utility for checking and fixing identified problems in online mode, without unmounting the file system.\n
The system call pwritev2() has been updated to include the RWF_NOAPPEND flag, which allows specifying an offset for writing, even if the file was opened in append mode.\n
New ioctl commands have been added: FS_IOC_GETUUID \u2014 returns the UUID identifier of the specified file system, and FS_IOC_GETFSSYSFSPATH \u2014 determines the location in \/sys\/fs of the specified mounted file system.\n
The efs, qnx4, and coda filesystems have been transitioned to use the new partition mounting API.\n
The implementation of file operations in case-insensitive mode has been improved. Performance has increased by initially performing case-sensitive comparisons and reverting to case-insensitive searches. Issues have been resolved when mounting overlayfs on directories with case-insensitive settings. <\/ul>\n
Memory and system services<\/b>\n
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Support for the Intel FRED (Flexible Return and Event Delivery) mechanism has been implemented, designed to enhance the efficiency and reliability of low-level event delivery compared to the currently used IDT (Interrupt Descriptor Table) mechanism. Performance improvements and reduced latency are achieved by returning events via the IRET processor instruction rather than passing them through the IDT table. Reliability is enhanced due to the separate handling of event arrival in kernel context and user context, protection against nested NMI execution, and saving all CPU registers related to exceptions in an extended stack frame.\n
The ability to optimize data access for individual CPU cores has been added through the use of named address spaces implemented in the GCC as an extension of GNU C.\n
The PIDFD_THREAD flag has been added to the pidfd_open() function, allowing the creation of pidfd for individual threads rather than only using pidfd in the context of the thread group leader. A pseudo-filesystem has also been proposed for access to pidfd through the virtual filesystem. Unlike process identification using pid, the pidfd identifier is linked to a specific process and does not change, while the PID may be reassigned to another process after the current process completes.\n
The BPF subsystem has introduced a BPF-token mechanism that allows selective delegation of access rights to privileged BPF operations for applications. For example, it is possible to grant an unprivileged application access to specific BPF subsystems without providing full CAP_BPF rights.\n
A new type of shared memory, bpf_arena, has been added to the BPF subsystem, defining an area accessible for sharing between BPF programs and user-space processes. The may_goto instruction has been added, enabling the organization of loop operations that can be interrupted by the verifier. It is now possible to generate arbitrary TCP SYN cookies from BPF programs and create BPF handlers to combat SYN flooding.\n
The transition of changes from the Rust-for-Linux branch continues, related to the use of the Rust language as a secondary language for developing drivers and kernel modules (Rust support is not enabled by default and does not make Rust a mandatory build dependency for the kernel). Support for using the Rust language on 64-bit ARM processors has been added. The transition to Rust version 1.76 has been made. The 'container_of!' macro has been added. Instead of the unstable 'ptr_metadata' feature, the stable 'byte_sub' method has been implemented. The 'time' module has been added with the time conversion function 'msecs_to_jiffies()'.\n
The io_uring subsystem has gained the ability to truncate files (ftruncate_file).\n
A new type of workqueues, WQ_BH (workqueue Bottom Halves), has been added for asynchronous code execution in the context of software interrupts, aimed at replacing deprecated tasklets.\n
The timer subsystem has been significantly reworked, improving the logic for selecting the active CPU core to execute the triggered timer, so as not to wake up inactive cores from sleep.\n
The ability to update the energy consumption model of the core (EM, Energy Model) during operation has been implemented, which can be used, for example, to account for the impact of operating temperature on CPU energy efficiency. The performance of the em_cpu_energy() function has been significantly improved, now executing 1.43 times faster in tests on a stationary system, and 1.69 times faster in tests on the RockPi 4B board.\n
Support has been added for running ARM64-based systems in LPA2 mode with a 52-bit virtual address space.\n
Continuous recording of PTE (Page Table Entry) has been implemented for ARM64 systems, increasing performance by enhancing the efficiency of TLB (Translation Lookaside Buffer) usage.\n
Patches have been accepted to enhance the performance of the memory management subsystem by reducing the occurrence of competing locks in vmalloc().\n
A live patching mechanism has been implemented for the LoongArch architecture, allowing for kernel fixes to be applied without rebooting.\n
Support for the membarrier() system call has been implemented for RISC-V systems, providing memory barriers for threads running in the system.\n
Requirements have been raised for the version of LLVM\/Clang that can be used to build the kernel. Building now requires at least LLVM release 13.0.1 (previously supported builds in LLVM 11+).\n
The 'User trace events' mechanism, which allows creating tracing events from user processes to track activity in user space, has been enhanced with support for exporting event information in various formats (USER_EVENT_REG_MULTI_FORMAT).\n
The function call tracing mechanism has been enhanced to track the state of incoming function arguments when tracing function exits. The return operator values can now be matched with the arguments used during the function call.\n
The perf utility now includes support for the 'cluster' output aggregation mode ('perf stat -a --per-cluster') to combine statistics of shared resources. The ability to use the libcapstone library for disassembling processor instructions ('perf script -F disasm') has been implemented. Memory consumption optimizations have been made during the execution of the 'perf report' and 'perf annotate' commands. <\/ul>\n
Virtualization and Security<\/b>\n
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Protection against the RFDS (Register File Data Sampling) vulnerability in Intel Atom processors has been added, allowing the extraction of residual information from the register files (RF, Register File) of the processor, which are used to share register contents across tasks on the same CPU core. Blocking the vulnerability requires a microcode update and the use of the VERW instruction to clear the contents of microarchitectural buffers when returning from kernel to user space. To enable protection during kernel boot, the flag 'reg_file_data_sampling=on' can be specified. Information about vulnerability exposure and the presence of required protection microcode can be assessed in the file '\/sys\/devices\/system\/cpu\/vulnerabilities\/reg_file_data_sampling'.\n
Basic support for guest system protection via the AMD SEV-SNP (Secure Nested Paging) extension has been added, ensuring secure operation with nested page tables and protecting against 'undeSErVed' and 'SEVerity' attacks on AMD EPYC processors, which can bypass the AMD SEV (Secure Encrypted Virtualization) protection mechanism. KVM<\/a> The necessary changes for using SNP are planned to be added in the 6.10 branch.\n