linux-toradex.git/drivers/md/md.h, branch v6.18-rc4

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: add a new recovery_flag MD_RECOVERY_LAZY_RECOVER

2025-09-06T09:20:32+00:00

This flag is used by llbitmap in later patches to skip raid456 initial
recover and delay building initial xor data to first write.

https://lore.kernel.org/linux-raid/20250829080426.1441678-10-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai

md: add a new mddev field 'bitmap_id'

2025-09-06T09:18:48+00:00

Prepare to store the bitmap id selected by user, also refactor
mddev_set_bitmap_ops a bit in case the value is invalid.

Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-5-yukuai1@huaweicloud.com
Signed-off-by: Yu Kuai 
Reviewed-by: Hannes Reinecke 
Reviewed-by: Li Nan 
Reviewed-by: Xiao Ni

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: factor out a helper raid_is_456()

2025-09-06T09:17:58+00:00

There are no functional changes, the helper will be used by llbitmap in
following patches.

Link: https://lore.kernel.org/linux-raid/20250829080426.1441678-3-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: 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/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

md: rename recovery_cp to resync_offset

2025-07-30T17:26:04+00:00

'recovery_cp' was used to represent the progress of sync, but its name
contains recovery, which can cause confusion. Replaces 'recovery_cp'
with 'resync_offset' for clarity.

Signed-off-by: Li Nan 
Link: https://lore.kernel.org/linux-raid/20250722033340.1933388-1-linan666@huaweicloud.com
Signed-off-by: Yu Kuai

md: call del_gendisk in control path

2025-07-12T09:51:54+00:00

Now del_gendisk and put_disk are called asynchronously in workqueue work.
The asynchronous way has a problem that the device node can still exist
after mdadm --stop command returns in a short window. So udev rule can
open this device node and create the struct mddev in kernel again. So put
del_gendisk in control path and still leave put_disk in md_kobj_release
to avoid uaf of gendisk.

Function del_gendisk can't be called with reconfig_mutex. If it's called
with reconfig mutex, a deadlock can happen. del_gendisk waits all sysfs
files access to finish and sysfs file access waits reconfig mutex. So
put del_gendisk after releasing reconfig mutex.

But there is still a window that sysfs can be accessed between mddev_unlock
and del_gendisk. So some actions (add disk, change level, .e.g) can happen
which lead unexpected results. MD_DELETED is used to resolve this problem.
MD_DELETED is set before releasing reconfig mutex and it should be checked
for these sysfs access which need reconfig mutex. For sysfs access which
don't need reconfig mutex, del_gendisk will wait them to finish.

But it doesn't need to do this in function mddev_lock_nointr. There are
ten places that call it.
* Five of them are in dm raid which we don't need to care. MD_DELETED is
only used for md raid.
* stop_sync_thread, md_do_sync and md_start_sync are related sync request,
and it needs to wait sync thread to finish before stopping an array.
* md_ioctl: md_open is called before md_ioctl, so ->openers is added. It
will fail to stop the array. So it doesn't need to check MD_DELETED here
* md_set_readonly:
It needs to call mddev_set_closing_and_sync_blockdev when setting readonly
or read_auto. So it will fail to stop the array too because MD_CLOSING is
already set.

Reviewed-by: Yu Kuai 
Signed-off-by: Xiao Ni 
Link: https://lore.kernel.org/linux-raid/20250611073108.25463-2-xni@redhat.com
Signed-off-by: Yu Kuai