| Message ID | cover.1604065156.git.naohiro.aota@wdc.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | btrfs: zoned block device support | expand |
On Fri, Oct 30, 2020 at 10:51:07PM +0900, Naohiro Aota wrote: > This series adds zoned block device support to btrfs. > Changes from v8: > - Direct-IO path now follow several hardware restrictions (other than > max_zone_append_size) by using ZONE_APPEND support of iomap > - introduces union of fs_info->zone_size and fs_info->zoned [Johannes] > - and use btrfs_is_zoned(fs_info) in place of btrfs_fs_incompat(fs_info, > ZONED) > - print if zoned is enabled or not when printing module info [Johannes] > - drop patch of disabling inode_cache on ZONED > - moved for_teelog flag to a proper location [Johannes] > - Code style fixes [Johannes] > - Add comment about adding physical layer things to ordered extent > structure > - Pass file_offset explicitly to extract_ordered_extent() instead of > determining it from bio > - Bug fixes > - write out fsync region so that the logical address of ordered extents > and checksums are properly finalized > - free zone_info at umount time > - fix superblock log handling when entering zones[1] in the first time > - fixes double free of log-tree roots [Johannes] > - Drop erroneous ASSERT in do_allocation_zoned() As discussed, patches 1-10 are preparatory and can be added to misc-next but there are still issues regarding coding style and messages. I'll reply to individual patches as well, list below. They're not the most useful comments regarding functionality but we won't have much chance to fix them later and we want to focus on the hard parts. * all comments start with uppercase, unless it's an identifier * error messages * don't start with uppercase (because there's a prefix already) * wording and style needs to be unified * new locks that are nested in existing locks need to documented * somewhere (treelog_bg_lock) * missing { } in if/else if/else blocks * newlines between function definitions
This series adds zoned block device support to btrfs. This series is also available on github. Kernel https://github.com/naota/linux/tree/btrfs-zoned-v9 Userland https://github.com/naota/btrfs-progs/tree/btrfs-zoned xfstests https://github.com/naota/fstests/tree/btrfs-zoned Userland tool depends on patched util-linux (libblkid and wipefs) to handle log-structured superblock. To ease the testing, pre-compiled static linked userland tools are available here: https://wdc.app.box.com/s/fnhqsb3otrvgkstq66o6bvdw6tk525kp Changes from v8: - Direct-IO path now follow several hardware restrictions (other than max_zone_append_size) by using ZONE_APPEND support of iomap - introduces union of fs_info->zone_size and fs_info->zoned [Johannes] - and use btrfs_is_zoned(fs_info) in place of btrfs_fs_incompat(fs_info, ZONED) - print if zoned is enabled or not when printing module info [Johannes] - drop patch of disabling inode_cache on ZONED - moved for_teelog flag to a proper location [Johannes] - Code style fixes [Johannes] - Add comment about adding physical layer things to ordered extent structure - Pass file_offset explicitly to extract_ordered_extent() instead of determining it from bio - Bug fixes - write out fsync region so that the logical address of ordered extents and checksums are properly finalized - free zone_info at umount time - fix superblock log handling when entering zones[1] in the first time - fixes double free of log-tree roots [Johannes] - Drop erroneous ASSERT in do_allocation_zoned() btrfs-progs and xfstests series will follow. This version of ZONED btrfs switched from normal write command to zone append write command. You do not need to specify LBA (at the write pointer) to write for zone append write command. Instead, you only select a zone to write with its start LBA. Then the device (NVMe ZNS), or the emulation of zone append command in the sd driver in the case of SAS or SATA HDDs, automatically writes the data at the write pointer position and return the written LBA as a command reply. The benefit of using the zone append write command is that write command issuing order does not matter. So, we can eliminate block group lock and utilize asynchronous checksum, which can reorder the IOs. Eliminating the lock improves performance. In particular, on a workload with massive competing to the same zone [1], we observed 36% performance improvement compared to normal write. [1] Fio running 16 jobs with 4KB random writes for 5 minutes However, there are some limitations. We cannot use the non-SINGLE profile. Supporting non-SINGLE profile with zone append writing is not trivial. For example, in the DUP profile, we send a zone append writing IO to two zones on a device. The device reply with written LBAs for the IOs. If the offsets of the returned addresses from the beginning of the zone are different, then it results in different logical addresses. For the same reason, we cannot issue multiple IOs for one ordered extent. Thus, the size of an ordered extent is limited under max_zone_append_size. This limitation will cause fragmentation and increased usage of metadata. In the future, we can add optimization to merge ordered extents after end_bio. * Patch series description A zoned block device consists of a number of zones. Zones are either conventional and accepting random writes or sequential and requiring that writes be issued in LBA order from each zone write pointer position. This patch series ensures that the sequential write constraint of sequential zones is respected while fundamentally not changing BtrFS block and I/O management for block stored in conventional zones. To achieve this, the default chunk size of btrfs is changed on zoned block devices so that chunks are always aligned to a zone. Allocation of blocks within a chunk is changed so that the allocation is always sequential from the beginning of the chunks. To do so, an allocation pointer is added to block groups and used as the allocation hint. The allocation changes also ensure that blocks freed below the allocation pointer are ignored, resulting in sequential block allocation regardless of the chunk usage. The zone of a chunk is reset to allow reuse of the zone only when the block group is being freed, that is, when all the chunks of the block group are unused. For btrfs volumes composed of multiple zoned disks, a restriction is added to ensure that all disks have the same zone size. This restriction matches the existing constraint that all chunks in a block group must have the same size. * Enabling tree-log The tree-log feature does not work on ZONED mode as is. Blocks for a tree-log tree are allocated mixed with other metadata blocks, and btrfs writes and syncs the tree-log blocks to devices at the time of fsync(), which is different timing than a global transaction commit. As a result, both writing tree-log blocks and writing other metadata blocks become non-sequential writes which ZONED mode must avoid. This series introduces a dedicated block group for tree-log blocks to create two metadata writing streams, one for tree-log blocks and the other for metadata blocks. As a result, each write stream can now be written to devices separately and sequentially. * Log-structured superblock Superblock (and its copies) is the only data structure in btrfs which has a fixed location on a device. Since we cannot overwrite in a sequential write required zone, we cannot place superblock in the zone. This series implements superblock log writing. It uses two zones as a circular buffer to write updated superblocks. Once the first zone is filled up, start writing into the second zone. The first zone will be reset once both zones are filled. We can determine the postion of the latest superblock by reading the write pointer information from a device. * Patch series organization Patches 1 and 2 are preparing patches for block and iomap layer. Patch 3 introduces the ZONED incompatible feature flag to indicate that the btrfs volume was formatted for use on zoned block devices. Patches 4 to 6 implement functions to gather information on the zones of the device (zones type, write pointer position, and max_zone_append_size). Patches 7 to 10 disable features which are not compatible with the sequential write constraints of zoned block devices. These includes space_cache, NODATACOW, fallocate, and MIXED_BG. Patch 11 implements the log-structured superblock writing. Patches 12 and 13 tweak the device extent allocation for ZONED mode and add verification to check if a device extent is properly aligned to zones. Patches 14 to 17 implements sequential block allocator for ZONED mode. Patch 18 implement a zone reset for unused block groups. Patches 19 to 30 implement the writing path for several types of IO (non-compressed data, direct IO, and metadata). These include re-dirtying once-freed metadata blocks to prevent write holes. Patches 31 to 40 tweak some btrfs features work with ZONED mode. These include device-replace, relocation, repairing IO error, and tree-log. Finally, patch 41 adds the ZONED feature to the list of supported features. * Patch testing note ** Zone-aware util-linux Since the log-structured superblock feature changed the location of superblock magic, the current util-linux (libblkid) cannot detect ZONED btrfs anymore. You need to apply a to-be posted patch to util-linux to make it "zone aware". ** Testing device You need devices with zone append writing command support to run ZONED btrfs. Other than real devices, null_blk supports zone append write command. You can use memory backed null_blk to run the test on it. Following script creates 12800 MB /dev/nullb0. sysfs=/sys/kernel/config/nullb/nullb0 size=12800 # MB # drop nullb0 if [[ -d $sysfs ]]; then echo 0 > "${sysfs}"/power rmdir $sysfs fi lsmod | grep -q null_blk && rmmod null_blk modprobe null_blk nr_devices=0 mkdir "${sysfs}" echo "${size}" > "${sysfs}"/size echo 1 > "${sysfs}"/zoned echo 0 > "${sysfs}"/zone_nr_conv echo 1 > "${sysfs}"/memory_backed echo 1 > "${sysfs}"/power udevadm settle Zoned SCSI devices such as SMR HDDs or scsi_debug also support the zone append command as an emulated command within the SCSI sd driver. This emulation is completely transparent to the user and provides the same semantic as a NVMe ZNS native drive support. Also, there is a qemu patch available to enable NVMe ZNS device. ** xfstests We ran xfstests on ZONED btrfs, and, if we omit some cases that are known to fail currently, all test cases pass. Cases that can be ignored: 1) failing also with the regular btrfs on regular devices, 2) trying to test fallocate feature without testing with "_require_xfs_io_command "falloc"", 3) trying to test incompatible features for ZONED btrfs (e.g. RAID5/6) 4) trying to use incompatible setup for ZONED btrfs (e.g. dm-linear not aligned to zone boundary, swap) 5) trying to create a file system with too small size, (we require at least 9 zones to initiate a ZONED btrfs) 6) dropping original MKFS_OPTIONS ("-O zoned"), so it cannot create ZONED btrfs (btrfs/003) 7) having ENOSPC which incurred by larger metadata block group size I will send a patch series for xfstests to handle these cases (2-6) properly. Patched xfstests is available here: https://github.com/naota/fstests/tree/btrfs-zoned Also, you need to apply the following patch if you run xfstests with tcmu devices. xfstests btrfs/003 failed to "_devmgt_add" after "_devmgt_remove" without this patch. https://marc.info/?l=linux-scsi&m=156498625421698&w=2 v8 https://lore.kernel.org/linux-btrfs/cover.1601572459.git.naohiro.aota@wdc.com/ v7 https://lore.kernel.org/linux-btrfs/20200911123259.3782926-1-naohiro.aota@wdc.com/ v6 https://lore.kernel.org/linux-btrfs/20191213040915.3502922-1-naohiro.aota@wdc.com/ v5 https://lore.kernel.org/linux-btrfs/20191204082513.857320-1-naohiro.aota@wdc.com/ v4 https://lwn.net/Articles/797061/ v3 https://lore.kernel.org/linux-btrfs/20190808093038.4163421-1-naohiro.aota@wdc.com/ v2 https://lore.kernel.org/linux-btrfs/20190607131025.31996-1-naohiro.aota@wdc.com/ v1 https://lore.kernel.org/linux-btrfs/20180809180450.5091-1-naota@elisp.net/ Changelog v8 - Use bio_add_hw_page() to build up bio to honor hardware restrictions - add bio_add_zone_append_page() as a wrapper of the function - Split file extent on submitting bio - If bio_add_zone_append_page() fails, split the file extent and send out bio - so, we can ensure one bio == one file extent - Fix build bot issues - Rebased on misc-next v7: - Use zone append write command instead of normal write command - Bio issuing order does not matter - No need to use lock anymore - Can use asynchronous checksum - Removed RAID support for now - Rename HMZONED to ZONED - Split some patches - Rebased on kdave/for-5.9-rc3 + iomap direct IO v6: - Use bitmap helpers (Johannes) - Code cleanup (Johannes) - Rebased on kdave/for-5.5 - Enable the tree-log feature. - Treat conventional zones as sequential zones, so we can now allow mixed allocation of conventional zone and sequential write required zone to construct a block group. - Implement log-structured superblock - No need for one conventional zone at the beginning of a device. - Fix deadlock of direct IO writing - Fix building with !CONFIG_BLK_DEV_ZONED (Johannes) - Fix leak of zone_info (Johannes) v5: - Rebased on kdave/for-5.5 - Enable the tree-log feature. - Treat conventional zones as sequential zones, so we can now allow mixed allocation of conventional zone and sequential write required zone to construct a block group. - Implement log-structured superblock - No need for one conventional zone at the beginning of a device. - Fix deadlock of direct IO writing - Fix building with !CONFIG_BLK_DEV_ZONED (Johannes) - Fix leak of zone_info (Johannes) v4: - Move memory allcation of zone informattion out of btrfs_get_dev_zones() (Anand) - Add disabled features table in commit log (Anand) - Ensure "max_chunk_size >= devs_min * data_stripes * zone_size" v3: - Serialize allocation and submit_bio instead of bio buffering in btrfs_map_bio(). -- Disable async checksum/submit in HMZONED mode - Introduce helper functions and hmzoned.c/h (Josef, David) - Add support for repairing IO failure - Add support for NOCOW direct IO write (Josef) - Disable preallocation entirely -- Disable INODE_MAP_CACHE -- relocation is reworked not to rely on preallocation in HMZONED mode - Disable NODATACOW -Disable MIXED_BG - Device extent that cover super block position is banned (David) v2: - Add support for dev-replace -- To support dev-replace, moved submit_buffer one layer up. It now handles bio instead of btrfs_bio. -- Mark unmirrored Block Group readonly only when there are writable mirrored BGs. Necessary to handle degraded RAID. - Expire worker use vanilla delayed_work instead of btrfs's async-thread - Device extent allocator now ensure that region is on the same zone type. - Add delayed allocation shrinking. - Rename btrfs_drop_dev_zonetypes() to btrfs_destroy_dev_zonetypes - Fix -- Use SECTOR_SHIFT (Nikolay) -- Use btrfs_err (Nikolay) Johannes Thumshirn (1): block: add bio_add_zone_append_page Naohiro Aota (40): iomap: support REQ_OP_ZONE_APPEND btrfs: introduce ZONED feature flag btrfs: Get zone information of zoned block devices btrfs: Check and enable ZONED mode btrfs: introduce max_zone_append_size btrfs: disallow space_cache in ZONED mode btrfs: disallow NODATACOW in ZONED mode btrfs: disable fallocate in ZONED mode btrfs: disallow mixed-bg in ZONED mode btrfs: implement log-structured superblock for ZONED mode btrfs: implement zoned chunk allocator btrfs: verify device extent is aligned to zone btrfs: load zone's alloction offset btrfs: emulate write pointer for conventional zones btrfs: track unusable bytes for zones btrfs: do sequential extent allocation in ZONED mode btrfs: reset zones of unused block groups btrfs: redirty released extent buffers in ZONED mode btrfs: extract page adding function btrfs: use bio_add_zone_append_page for zoned btrfs btrfs: handle REQ_OP_ZONE_APPEND as writing btrfs: split ordered extent when bio is sent btrfs: extend btrfs_rmap_block for specifying a device btrfs: use ZONE_APPEND write for ZONED btrfs btrfs: enable zone append writing for direct IO btrfs: introduce dedicated data write path for ZONED mode btrfs: serialize meta IOs on ZONED mode btrfs: wait existing extents before truncating btrfs: avoid async metadata checksum on ZONED mode btrfs: mark block groups to copy for device-replace btrfs: implement cloning for ZONED device-replace btrfs: implement copying for ZONED device-replace btrfs: support dev-replace in ZONED mode btrfs: enable relocation in ZONED mode btrfs: relocate block group to repair IO failure in ZONED btrfs: split alloc_log_tree() btrfs: extend zoned allocator to use dedicated tree-log block group btrfs: serialize log transaction on ZONED mode btrfs: reorder log node allocation btrfs: enable to mount ZONED incompat flag block/bio.c | 36 + fs/btrfs/Makefile | 1 + fs/btrfs/block-group.c | 90 ++- fs/btrfs/block-group.h | 13 + fs/btrfs/ctree.h | 18 +- fs/btrfs/dev-replace.c | 187 ++++++ fs/btrfs/dev-replace.h | 3 + fs/btrfs/disk-io.c | 92 ++- fs/btrfs/disk-io.h | 2 + fs/btrfs/extent-tree.c | 206 +++++- fs/btrfs/extent_io.c | 136 +++- fs/btrfs/extent_io.h | 2 + fs/btrfs/file.c | 6 +- fs/btrfs/free-space-cache.c | 58 ++ fs/btrfs/free-space-cache.h | 4 + fs/btrfs/inode.c | 164 ++++- fs/btrfs/ioctl.c | 16 + fs/btrfs/ordered-data.c | 79 +++ fs/btrfs/ordered-data.h | 10 + fs/btrfs/relocation.c | 35 +- fs/btrfs/scrub.c | 145 ++++ fs/btrfs/space-info.c | 13 +- fs/btrfs/space-info.h | 4 +- fs/btrfs/super.c | 18 +- fs/btrfs/sysfs.c | 4 + fs/btrfs/transaction.c | 10 + fs/btrfs/transaction.h | 3 + fs/btrfs/tree-log.c | 52 +- fs/btrfs/volumes.c | 311 ++++++++- fs/btrfs/volumes.h | 7 + fs/btrfs/zoned.c | 1264 +++++++++++++++++++++++++++++++++++ fs/btrfs/zoned.h | 273 ++++++++ fs/iomap/direct-io.c | 22 +- include/linux/bio.h | 2 + include/linux/iomap.h | 1 + include/uapi/linux/btrfs.h | 1 + 36 files changed, 3176 insertions(+), 112 deletions(-) create mode 100644 fs/btrfs/zoned.c create mode 100644 fs/btrfs/zoned.h