kernel/linux.git/drivers/md/md-bitmap.h, branch v6.19.11

md/md-llbitmap: introduce new lockless bitmap

2025-09-06T09:27:51+00:00

Redundant data is used to enhance data fault tolerance, and the storage method for redundant data vary depending on the RAID levels. And it's important to maintain the consistency of redundant data. Bitmap is used to record which data blocks have been synchronized and which ones need to be resynchronized or recovered. Each bit in the bitmap represents a segment of data in the array. When a bit is set, it indicates that the multiple redundant copies of that data segment may not be consistent. Data synchronization can be performed based on the bitmap after power failure or readding a disk. If there is no bitmap, a full disk synchronization is required. Due to known performance issues with md-bitmap and the unreasonable implementations: - self-managed IO submitting like filemap_write_page(); - global spin_lock I have decided not to continue optimizing based on the current bitmap implementation, this new bitmap is invented without locking from IO fast path and can be used with fast disks. For designs and details, see the comments in drivers/md-llbitmap.c. Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-12-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Li Nan

md/md-bitmap: add a new method blocks_synced() in bitmap_operations

2025-09-06T09:20:01+00:00

Currently, raid456 must perform a whole array initial recovery to build initail xor data, then IO to the array won't have to read all the blocks in underlying disks. This behavior will affect IO performance a lot, and nowadays there are huge disks and the initial recovery can take a long time. Hence llbitmap will support lazy initial recovery in following patches. This method is used to check if data blocks is synced or not, if not then IO will still have to read all blocks for raid456. Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-9-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai

md/md-bitmap: add a new method skip_sync_blocks() in bitmap_operations

2025-09-06T09:19:45+00:00

This method is used to check if blocks can be skipped before calling into pers->sync_request(), llbitmap will use this method to skip resync for unwritten/clean data blocks, and recovery/check/repair for unwritten data blocks; Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-8-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Christoph Hellwig Reviewed-by: Xiao Ni Reviewed-by: Hannes Reinecke Reviewed-by: Li Nan

md/md-bitmap: support discard for bitmap ops

2025-09-06T09:18:19+00:00

Use two new methods {start, end}_discard in bitmap_ops and a new field 'rw' in struct md_io_clone to handle discard IO, prepare to support new md bitmap. Since all bitmap functions to hanlde write IO are the same, also add typedef to make code cleaner. Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-4-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni Reviewed-by: Hannes Reinecke Reviewed-by: Li Nan

md/md-bitmap: introduce CONFIG_MD_BITMAP

2025-09-06T09:12:22+00:00

Now that all implementations are internal, it's sensible to add a config option for md-bitmap, and it's a good way for isolation. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-16-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni

md/md-bitmap: handle the case bitmap is not enabled before end_sync()

2025-09-06T09:11:54+00:00

This case can be handled without knowing internal implementation. Prepare to introduce CONFIG_MD_BITMAP. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-9-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni

md/md-bitmap: handle the case bitmap is not enabled before start_sync()

2025-09-06T09:11:50+00:00

This case can be handled without knowing internal implementation. Prepare to introduce CONFIG_MD_BITMAP. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-8-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni

md/md-bitmap: add md_bitmap_registered/enabled() helper

2025-09-06T09:11:45+00:00

There are no functional changes, prepare to handle the case that mddev->bitmap_ops can be NULL, which is possible after introducing CONFIG_MD_BITMAP. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-7-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni

md/md-bitmap: add a new parameter 'flush' to bitmap_ops->enabled

2025-09-06T09:11:42+00:00

The method is only used from raid1/raid10 IO path, to check if write bio should be pluged, the parameter is always set to true for now, following patch will use this helper in other context like updating superblock. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-6-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni

md/md-bitmap: merge md_bitmap_group into bitmap_operations

2025-09-06T09:11:40+00:00

Now that all bitmap implementations are internal, it doesn't make sense to export md_bitmap_group anymore. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-5-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni