Re: [PATCH v2 0/5] md/md-llbitmap: fixes and proactive parity building support

["Yu Kuai" <yukuai@fnnas.com>]

在 2026/2/23 10:40, Yu Kuai 写道:
> Changes in v2:
>   - add error message in error path in patch 3;
>
> This series contains fixes and enhancements for the md-llbitmap (lockless
> bitmap) implementation.
>
> Patches 1-2 are bug fixes:
> - Patch 1 fixes bitmap data being read from spare disks that are not yet
>    in sync, which could lead to incorrect dirty bit tracking.
> - Patch 2 fixes a race condition where the state machine could transition
>    before the barrier is properly raised.
>
> Patch 3 improves compatibility with older mdadm versions by detecting
> on-disk bitmap version and falling back to the correct bitmap_ops when
> there's a version mismatch.
>
> Patch 4 adds support for proactive XOR parity building in RAID-456 arrays.
> This allows users to pre-build parity for unwritten regions via sysfs
> before any user data is written, which can improve write performance for
> workloads that will eventually use all storage. New states (CleanUnwritten,
> NeedSyncUnwritten, SyncingUnwritten) are added to track these regions
> separately from normal dirty/syncing states.
>
> Patch 5 optimizes initial array sync for RAID-456 arrays on devices that
> support write_zeroes with unmap. By zeroing all disks upfront, parity is
> automatically consistent (0 XOR 0 = 0), allowing the bitmap to be
> initialized to BitCleanUnwritten and skipping the initial sync entirely.
> This significantly reduces array initialization time on modern NVMe SSDs.
>
> Yu Kuai (5):
>    md/md-llbitmap: skip reading rdevs that are not in_sync
>    md/md-llbitmap: raise barrier before state machine transition
>    md: add fallback to correct bitmap_ops on version mismatch
>    md/md-llbitmap: add CleanUnwritten state for RAID-5 proactive parity
>      building
>    md/md-llbitmap: optimize initial sync with write_zeroes_unmap support
>
>   drivers/md/md-llbitmap.c | 213 +++++++++++++++++++++++++++++++++++----
>   drivers/md/md.c          | 117 ++++++++++++++++++++-
>   2 files changed, 309 insertions(+), 21 deletions(-)

Apply patch 1 and 2 to md-7.1, will send a new version for others soon.

-- 
Thansk,
Kuai