This patch series introduces the mpool object storage media pool driver. Mpool implements a simple transactional object store on top of block storage devices. Mpool was developed for the Heterogeneous-Memory Storage Engine (HSE) project, which is a high-performance key-value storage engine designed for SSDs. HSE stores its data exclusively in mpool. Mpool is readily applicable to other storage systems built on immutable objects. For example, the many databases that store records in immutable SSTables organized as an LSM-tree or similar data structure. We developed mpool for HSE storage, versus using a file system or raw block device, for several reasons. A primary motivator was the need for a storage model that maps naturally to conventional block storage devices, as well as to emerging device interfaces we plan to support in the future, such as * NVMe Zoned Namespaces (ZNS) * NVMe Streams * Persistent memory accessed via CXL or similar technologies Another motivator was the need for a storage model that readily supports multiple classes of storage devices or media in a single storage pool, such as * QLC SSDs for storing the bulk of objects, and * 3DXP SSDs or persistent memory for storing objects requiring low-latency access The mpool object storage model meets these needs. It also provides other features that benefit storage systems built on immutable objects, including * Facilities to memory-map a specified collection of objects into a linear address space * Concurrent access to object data directly and memory-mapped to greatly reduce page cache pollution from background operations such as LSM-tree compaction * Proactive eviction of object data from the page cache, based on object-level metrics, to avoid excessive memory pressure and its associated performance impacts * High concurrency and short code paths for efficient access to low-latency storage devices HSE takes advantage of all these mpool features to achieve high throughput with low tail-latencies. Mpool is implemented as a character device driver where * /dev/mpoolctl is the control file (minor number 0) supporting mpool management ioctls * /dev/mpool/<mpool-name> are mpool files (minor numbers >0), one per mpool, supporting object management ioctls CLI/UAPI access to /dev/mpoolctl and /dev/mpool/<mpool-name> are controlled by their UID, GID, and mode bits. To provide a familiar look and feel, the mpool management model and CLI are intentionally aligned to those of LVM to the degree practical. An mpool is created with a block storage device specified for its required capacity media class, and optionally a second block storage device specified for its staging media class. We recommend virtual block devices (such as LVM logical volumes) to aggregate the performance and capacity of multiple physical block devices, to enable sharing of physical block devices between mpools (or for other uses), and to support extending the size of a block device used for an mpool media class. The libblkid library recognizes mpool formatted block devices as of util-linux v2.32. Mpool implements a transactional object store with two simple object abstractions: mblocks and mlogs. Mblock objects are containers comprising a linear sequence of bytes that can be written exactly once, are immutable after writing, and can be read in whole or in part as needed until deleted. Mblocks in a media class are currently fixed size, which is configured when an mpool is created, though the amount of data written to mblocks will differ. Mlog objects are containers for record logging. Records of arbitrary size can be appended to an mlog until it is full. Once full, an mlog must be erased before additional records can be appended. Mlog records can be read sequentially from the beginning at any time. Mlogs in a media class are always a multiple of the mblock size for that media class. Mblock and mlog writes avoid the page cache. Mblocks are written, committed, and made immutable before they can be read either directly (avoiding the page cache) or mmaped. Mlogs are always read and updated directly (avoiding the page cache) and cannot be mmaped. Mpool also provides the metadata container (MDC) APIs that clients can use to simplify storing and maintaining metadata. These MDC APIs are helper functions built on a pair of mlogs per MDC. The mpool Wiki contains full details on the * Management model in the "Configure mpools" section * Object model in the "Develop mpool Applications" section * Kernel module architecture in the "Explore mpool Internals" section, which provides context for reviewing this patch series See https://github.com/hse-project/mpool/wiki The mpool UAPI and kernel module (not the patchset) are available on GitHub at: https://github.com/hse-project/mpool https://github.com/hse-project/mpool-kmod The HSE key-value storage engine is available on GitHub at: https://github.com/hse-project/hse Changes in v2: - Fixes build errors/warnings reported by bot on ARCH=m68k Reported-by: kernel test robot <lkp@xxxxxxxxx> - Addresses review comments from Randy and Hillf: * Updates ioctl-number.rst file with mpool driver's ioctl code * Fixes issues in the usage of printk_timed_ratelimit() - Fixes a readahead issue found by internal testing Nabeel M Mohamed (22): mpool: add utility routines and ioctl definitions mpool: add in-memory struct definitions mpool: add on-media struct definitions mpool: add pool drive component which handles mpool IO using the block layer API mpool: add space map component which manages free space on mpool devices mpool: add on-media pack, unpack and upgrade routines mpool: add superblock management routines mpool: add pool metadata routines to manage object lifecycle and IO mpool: add mblock lifecycle management and IO routines mpool: add mlog IO utility routines mpool: add mlog lifecycle management and IO routines mpool: add metadata container or mlog-pair framework mpool: add utility routines for mpool lifecycle management mpool: add pool metadata routines to create persistent mpools mpool: add mpool lifecycle management routines mpool: add mpool control plane utility routines mpool: add mpool lifecycle management ioctls mpool: add object lifecycle management ioctls mpool: add support to mmap arbitrary collection of mblocks mpool: add support to proactively evict cached mblock data from the page-cache mpool: add documentation mpool: add Kconfig and Makefile .../userspace-api/ioctl/ioctl-number.rst | 3 +- drivers/Kconfig | 2 + drivers/Makefile | 1 + drivers/mpool/Kconfig | 28 + drivers/mpool/Makefile | 11 + drivers/mpool/assert.h | 25 + drivers/mpool/init.c | 126 + drivers/mpool/init.h | 17 + drivers/mpool/mblock.c | 432 +++ drivers/mpool/mblock.h | 161 + drivers/mpool/mcache.c | 1072 +++++++ drivers/mpool/mcache.h | 104 + drivers/mpool/mclass.c | 103 + drivers/mpool/mclass.h | 137 + drivers/mpool/mdc.c | 486 +++ drivers/mpool/mdc.h | 106 + drivers/mpool/mlog.c | 1667 ++++++++++ drivers/mpool/mlog.h | 212 ++ drivers/mpool/mlog_utils.c | 1352 ++++++++ drivers/mpool/mlog_utils.h | 63 + drivers/mpool/mp.c | 1086 +++++++ drivers/mpool/mp.h | 231 ++ drivers/mpool/mpcore.c | 987 ++++++ drivers/mpool/mpcore.h | 354 +++ drivers/mpool/mpctl.c | 2747 +++++++++++++++++ drivers/mpool/mpctl.h | 58 + drivers/mpool/mpool-locking.rst | 90 + drivers/mpool/mpool_ioctl.h | 636 ++++ drivers/mpool/mpool_printk.h | 43 + drivers/mpool/omf.c | 1316 ++++++++ drivers/mpool/omf.h | 593 ++++ drivers/mpool/omf_if.h | 381 +++ drivers/mpool/params.h | 116 + drivers/mpool/pd.c | 424 +++ drivers/mpool/pd.h | 202 ++ drivers/mpool/pmd.c | 2046 ++++++++++++ drivers/mpool/pmd.h | 379 +++ drivers/mpool/pmd_obj.c | 1569 ++++++++++ drivers/mpool/pmd_obj.h | 499 +++ drivers/mpool/reaper.c | 686 ++++ drivers/mpool/reaper.h | 71 + drivers/mpool/sb.c | 625 ++++ drivers/mpool/sb.h | 162 + drivers/mpool/smap.c | 1031 +++++++ drivers/mpool/smap.h | 334 ++ drivers/mpool/sysfs.c | 48 + drivers/mpool/sysfs.h | 48 + drivers/mpool/upgrade.c | 138 + drivers/mpool/upgrade.h | 128 + drivers/mpool/uuid.h | 59 + 50 files changed, 23194 insertions(+), 1 deletion(-) create mode 100644 drivers/mpool/Kconfig create mode 100644 drivers/mpool/Makefile create mode 100644 drivers/mpool/assert.h create mode 100644 drivers/mpool/init.c create mode 100644 drivers/mpool/init.h create mode 100644 drivers/mpool/mblock.c create mode 100644 drivers/mpool/mblock.h create mode 100644 drivers/mpool/mcache.c create mode 100644 drivers/mpool/mcache.h create mode 100644 drivers/mpool/mclass.c create mode 100644 drivers/mpool/mclass.h create mode 100644 drivers/mpool/mdc.c create mode 100644 drivers/mpool/mdc.h create mode 100644 drivers/mpool/mlog.c create mode 100644 drivers/mpool/mlog.h create mode 100644 drivers/mpool/mlog_utils.c create mode 100644 drivers/mpool/mlog_utils.h create mode 100644 drivers/mpool/mp.c create mode 100644 drivers/mpool/mp.h create mode 100644 drivers/mpool/mpcore.c create mode 100644 drivers/mpool/mpcore.h create mode 100644 drivers/mpool/mpctl.c create mode 100644 drivers/mpool/mpctl.h create mode 100644 drivers/mpool/mpool-locking.rst create mode 100644 drivers/mpool/mpool_ioctl.h create mode 100644 drivers/mpool/mpool_printk.h create mode 100644 drivers/mpool/omf.c create mode 100644 drivers/mpool/omf.h create mode 100644 drivers/mpool/omf_if.h create mode 100644 drivers/mpool/params.h create mode 100644 drivers/mpool/pd.c create mode 100644 drivers/mpool/pd.h create mode 100644 drivers/mpool/pmd.c create mode 100644 drivers/mpool/pmd.h create mode 100644 drivers/mpool/pmd_obj.c create mode 100644 drivers/mpool/pmd_obj.h create mode 100644 drivers/mpool/reaper.c create mode 100644 drivers/mpool/reaper.h create mode 100644 drivers/mpool/sb.c create mode 100644 drivers/mpool/sb.h create mode 100644 drivers/mpool/smap.c create mode 100644 drivers/mpool/smap.h create mode 100644 drivers/mpool/sysfs.c create mode 100644 drivers/mpool/sysfs.h create mode 100644 drivers/mpool/upgrade.c create mode 100644 drivers/mpool/upgrade.h create mode 100644 drivers/mpool/uuid.h -- 2.17.2
