kernel/linux.git/drivers/md/md-bitmap.c, branch v6.18.43

md/raid1: honor REQ_NOWAIT when waiting for behind writes

2026-07-24T14:16:32+00:00

[ Upstream commit a286cb88ddb26c5f4377859d8e77233d9181eb82 ] raid1 supports REQ_NOWAIT reads by avoiding waits in the barrier path through wait_read_barrier(). However, a read can still block on a WriteMostly device when the array uses a bitmap and there are outstanding behind writes. In that case raid1 unconditionally calls wait_behind_writes(), which may sleep until all behind writes complete. As a result, a REQ_NOWAIT read can block despite the caller explicitly requesting non-blocking behavior. This ensures that raid1 consistently honors REQ_NOWAIT reads across all paths that may otherwise wait for behind writes. Fixes: 5aa705039c4f ("md: raid1 add nowait support") Signed-off-by: Abd-Alrhman Masalkhi Link: https://patch.msgid.link/20260611083514.754922-1-abd.masalkhi@gmail.com Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin

md: merge mddev serialize_policy into mddev_flags

2026-07-24T14:16:32+00:00

[ Upstream commit 10787568cc1f3f80afc510b2728751989dfa0ae6 ] There is not need to use a separate field in struct mddev, there are no functional changes. Link: https://lore.kernel.org/linux-raid/20260114171241.3043364-5-yukuai@fnnas.com Signed-off-by: Yu Kuai Reviewed-by: Li Nan Stable-dep-of: a286cb88ddb2 ("md/raid1: honor REQ_NOWAIT when waiting for behind writes") Signed-off-by: Sasha Levin

md/md-bitmap: add a none backend for bitmap grow

2026-05-23T11:07:10+00:00

[ Upstream commit f2926a533d03fe70d753b512b713e06a2aa174af ] Add a real none bitmap backend that exposes the common bitmap sysfs group and use it to keep bitmap/location available when an array has no bitmap. Then switch the bitmap location sysfs path to move only between none and the classic bitmap backend, using the no-sysfs bitmap helpers while merging or unmerging the internal bitmap sysfs group. This restores mdadm --grow bitmap addition through bitmap/location. Fixes: fb8cc3b0d9db ("md/md-bitmap: delay registration of bitmap_ops until creating bitmap") Reviewed-by: Su Yue Link: https://lore.kernel.org/r/20260425024615.1696892-4-yukuai@fnnas.com Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin

md/md-bitmap: split bitmap sysfs groups

2026-05-23T11:07:10+00:00

[ Upstream commit aba3d6d6cb55c6e1116d1215140559dd7ecdf9a9 ] Split the classic bitmap sysfs files into a common bitmap group with the location attribute and a separate internal bitmap group for the remaining files. At the same time, convert bitmap operations from a single sysfs group to a sysfs group array so backends can share part of their sysfs layout while adding backend-specific attributes separately. Switch the bitmap sysfs helpers to use sysfs_update_groups() for the add and update path, and remove groups in reverse order so shared named groups are unmerged before the last group removes the directory. Also make bitmap operation lookup depend only on the currently selected bitmap id matching the installed backend. This prepares the lookup path for a later registered none backend. Reviewed-by: Su Yue Link: https://lore.kernel.org/r/20260425024615.1696892-3-yukuai@fnnas.com Signed-off-by: Yu Kuai Stable-dep-of: f2926a533d03 ("md/md-bitmap: add a none backend for bitmap grow") Signed-off-by: Sasha Levin

md/bitmap: fix GPF in write_page caused by resize race

2026-03-04T12:21:16+00:00

[ Upstream commit 46ef85f854dfa9d5226b3c1c46493d79556c9589 ] A General Protection Fault occurs in write_page() during array resize: RIP: 0010:write_page+0x22b/0x3c0 [md_mod] This is a use-after-free race between bitmap_daemon_work() and __bitmap_resize(). The daemon iterates over `bitmap->storage.filemap` without locking, while the resize path frees that storage via md_bitmap_file_unmap(). `quiesce()` does not stop the md thread, allowing concurrent access to freed pages. Fix by holding `mddev->bitmap_info.mutex` during the bitmap update. Link: https://lore.kernel.org/linux-raid/20260120102456.25169-1-jinpu.wang@ionos.com Closes: https://lore.kernel.org/linux-raid/CAMGffE=Mbfp=7xD_hYxXk1PAaCZNSEAVeQGKGy7YF9f2S4=NEA@mail.gmail.com/T/#u Cc: stable@vger.kernel.org Fixes: d60b479d177a ("md/bitmap: add bitmap_resize function to allow bitmap resizing.") Signed-off-by: Jack Wang Signed-off-by: Yu Kuai Signed-off-by: Sasha Levin

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: 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: add a new parameter 'offset' to md_super_write()

2025-09-06T09:17:26+00:00

The parameter is always set to 0 for now, following patches will use this helper to write llbitmap to underlying disks, allow writing dirty sectors instead of the whole page. Also rename md_super_write to md_write_metadata since there is nothing super-block specific. Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-2-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni Reviewed-by: Christoph Hellwig 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/raid1: check bitmap before behind write

2025-09-06T09:11:58+00:00

behind write rely on bitmap, because the number of IO are recorded in bitmap->behind_writes, and callers rely on bitmap_wait_behind_writes() to wait for IO to be done. However, currently callers doesn't check if bitmap is enabeld before calling into behind methods. Hence if behind write start without bitmap, readers will not wait for slow write IO to be done and old data can be read in some corner cases. Link: https://lore.kernel.org/linux-raid/20250707012711.376844-10-yukuai1@huaweicloud.com Signed-off-by: Yu Kuai Reviewed-by: Xiao Ni