Messages in this thread | | | Subject | Re: [RFC PATCH 00/17] btrfs zoned block device support | From | Nikolay Borisov <> | Date | Fri, 10 Aug 2018 10:53:22 +0300 |
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On 9.08.2018 21:04, Naohiro Aota wrote: > This series adds zoned block device support to btrfs. > > 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 dev extent size of btrfs is changed on zoned > block devices so that dev extents are always aligned to a zone. Allocation > of blocks within a block group is changed so that the allocation is always > sequential from the beginning of the block groups. To do so, an allocation > pointer is added to block groups and used as the allocation hint. The > allocation changes also ensures that block freed below the allocation > pointer are ignored, resulting in sequential block allocation regardless of > the block group usage. > > While the introduction of the allocation pointer ensure that blocks will be > allocated sequentially, I/Os to write out newly allocated blocks may be > issued out of order, causing errors when writing to sequential zones. This > problem s solved by introducing a submit_buffer() function and changes to > the internal I/O scheduler to ensure in-order issuing of write I/Os for > each chunk and corresponding to the block allocation order in the chunk. > > The zones of a chunk are reset to allow reusing of the zone only when the > block group is being freed, that is, when all the extents of the block group > are unused. > > For btrfs volumes composed of multiple zoned disks, restrictions are added > to ensure that all disks have the same zone size. This matches the existing > constraint that all dev extents in a chunk must have the same size. > > It requires zoned block devices to test the patchset. Even if you don't > have zone devices, you can use tcmu-runner [1] to emulate zoned block > devices. It can export emulated zoned block devices via iSCSI. Please see > the README.md of tcmu-runner [2] for howtos to generate a zoned block > device on tcmu-runner. > > [1] https://github.com/open-iscsi/tcmu-runner > [2] https://github.com/open-iscsi/tcmu-runner/blob/master/README.md > > Patch 1 introduces the HMZONED incompatible feature flag to indicate that > the btrfs volume was formatted for use on zoned block devices. > > Patches 2 and 3 implement functions to gather information on the zones of > the device (zones type and write pointer position). > > Patch 4 restrict the possible locations of super blocks to conventional > zones to preserve the existing update in-place mechanism for the super > blocks. > > Patches 5 to 7 disable features which are not compatible with the sequential > write constraints of zoned block devices. This includes fallocate and > direct I/O support. Device replace is also disabled for now. > > Patches 8 and 9 tweak the extent buffer allocation for HMZONED mode to > implement sequential block allocation in block groups and chunks. > > Patches 10 to 12 implement the new submit buffer I/O path to ensure sequential > write I/O delivery to the device zones. > > Patches 13 to 16 modify several parts of btrfs to handle free blocks > without breaking the sequential block allocation and sequential write order > as well as zone reset for unused chunks. > > Finally, patch 17 adds the HMZONED feature to the list of supported > features. > > Naohiro Aota (17): > btrfs: introduce HMZONED feature flag > btrfs: Get zone information of zoned block devices > btrfs: Check and enable HMZONED mode > btrfs: limit super block locations in HMZONED mode > btrfs: disable fallocate in HMZONED mode > btrfs: disable direct IO in HMZONED mode > btrfs: disable device replace in HMZONED mode > btrfs: align extent allocation to zone boundary > btrfs: do sequential allocation on HMZONED drives > btrfs: split btrfs_map_bio() > btrfs: introduce submit buffer > btrfs: expire submit buffer on timeout > btrfs: avoid sync IO prioritization on checksum in HMZONED mode > btrfs: redirty released extent buffers in sequential BGs > btrfs: reset zones of unused block groups > btrfs: wait existing extents before truncating > btrfs: enable to mount HMZONED incompat flag > > fs/btrfs/async-thread.c | 1 + > fs/btrfs/async-thread.h | 1 + > fs/btrfs/ctree.h | 36 ++- > fs/btrfs/dev-replace.c | 10 + > fs/btrfs/disk-io.c | 48 +++- > fs/btrfs/extent-tree.c | 281 +++++++++++++++++- > fs/btrfs/extent_io.c | 1 + > fs/btrfs/extent_io.h | 1 + > fs/btrfs/file.c | 4 + > fs/btrfs/free-space-cache.c | 36 +++ > fs/btrfs/free-space-cache.h | 10 + > fs/btrfs/inode.c | 14 + > fs/btrfs/super.c | 32 ++- > fs/btrfs/sysfs.c | 2 + > fs/btrfs/transaction.c | 32 +++ > fs/btrfs/transaction.h | 3 + > fs/btrfs/volumes.c | 551 ++++++++++++++++++++++++++++++++++-- > fs/btrfs/volumes.h | 37 +++ > include/uapi/linux/btrfs.h | 1 + > 19 files changed, 1061 insertions(+), 40 deletions(-) >
There are multiple places where you do naked shifts by ilog2(sectorsize). There is a perfectly well named define: SECTOR_SHIFT which a lot more informative for someone who doesn't necessarily have experience with linux storage/fs layers. Please fix such occurrences of magic values shifting.
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