User`s guide

Core Kernel Functionality

• RAID-5 XOR checksumming is optimized by taking advantage of the 256-bit YMM registers introduced

by Advanced Vector Extensions (AVX). (3.5)

• RAID-6 includes Supplemental Streaming SIMD Extensions 3 (SSSE3) optimized recovery functions and

a new algorithm for selecting the most appropriate function to use for recovery. (3.5)

• MD allows a reshape operation to be reversed by implementing a new reshape_direction attribute

that can be set when delta_disks is zero, and which can take one of the values forward or

backwards. (3.5)

• A RAID-10 array can be reshaped to a different near or offset layout, a different chunk size, and a

different number of devices. The number of copies cannot be changed. (3.5)

• An existing partition can be resized, even if currently in use, by using the operation code

BLKPG_RESIZE_PARTITION with the BLKPG ioctl(). (3.6)

• Add MD support for RAID10 (striped mirrors) and RAID1E (integrated adjacent stripe mirroring). (3.6)

• Thin target in the device mapper adds read-only and fail-io modes to thin provisioning. If a

transaction commit fails, a pool's metadata device transitions to read-only mode. If a commit fails

when the device is in read-only mode, a transition to fail-io mode occurs. In fail-io mode, the

pool and all associated thin devices report a status of fail if a commit fails. (3.6)

• The persistent data debug space map checker has been removed from the device mapper. The feature

consumed a lot of memory and caused other issues when enabled on large pools. (3.6)

• RAID-1 in MD now prevents the merging of large requests to enhance the performance of SSD devices

that function more efficiently with large request transfers. (3.6)

• Support for the WRITE SAME request implemented on some SCSI devices to allow a block to be

efficiently replicated throughout a block range. Only a single logical block need be transferred from the

host. The storage device writes the same data to all blocks specified by the request. (3.7)

• The BLKZEROOUT ioctl() can be used to zero out block ranges via blkdev_issue_zerooout().

(3.7)

• Fastmap support provides a method for attaching an unsorted block image (UBI) device in real-time.

Rather than scanning the entire device, Fastmap locates a checkpoint. (3.7)

• MD adds TRIM discard support for linear RAID-0, RAID-1, RAID-5, and RAID-10. (3.7)

• DM adds rebuild capacity and replacement slot validation for RAID-10 arrays. (3.7)

• RAID-6 recovery is optimized by taking advantage of the 256-bit YMM registers introduced by Advanced

Vector Extensions 2 (AVX2). (3.8)

A.3 Core Kernel Functionality

• Add a lock-less NULL-terminated single list. (3.1)

• Add a library function implementing a crc8 algorithm to support the brcm80211 driver. (3.1)

• Make the gen_pool memory allocator lockless. This change makes it safe to use the memory allocator

in NMI handlers and other special unblockable contexts where deadlocks might occur. (3.1)

• Implement the PTRACE_INTERRUPT, PTRACE_LISTEN, PTRACE_SEIZE, and TRAP_NOTIFY

ptrace() requests. (3.1)

• Adds /sys/module/module_name/uevent files to all module entries to provide a method for

managing built-in modules from user space. (3.1)