Re: [PATCH v13 0/3] md/md-bitmap: restore bitmap grow through sysfs

[Su Yue <l@damenly.org>]

On Sat 25 Apr 2026 at 10:46, Yu Kuai <yukuai@fnnas.com> wrote:

> mdadm --grow adds an internal bitmap by writing bitmap/location 
> for an
> array that currently has no bitmap. That requires the bitmap 
> directory
> and location attribute to exist before the classic bitmap 
> backend is
> created.
>
> This series separates bitmap backend lifetime from bitmap sysfs 
> lifetime,
> splits the sysfs layout into common and backend-specific groups, 
> and adds
> a small "none" bitmap backend. The none backend keeps 
> bitmap/location
> available while no real bitmap is active, and the location store 
> path can
> then switch between the none backend and the classic bitmap 
> backend
> without tearing down the common bitmap sysfs directory.
>
> Patch 1 factors bitmap creation and destruction into helpers 
> that do not
> touch sysfs registration.
>
> Patch 2 splits the classic bitmap sysfs files into a common 
> group and an
> internal-bitmap group, and converts bitmap backend operations to 
> use a
> sysfs group array.
>
> Patch 3 adds the none backend and uses it to restore mdadm 
> --grow bitmap
> addition through bitmap/location.
>
> Changes since v12:
> - Keep the factoring patch focused on no-sysfs bitmap lifetime 
> helpers.
> - Make bitmap operation lookup depend only on the current bitmap 
> id
>   matching the installed backend.
> - Trim the none backend to only the operations required by the 
> active
>   call paths.
> - Rework bitmap/location error handling with explicit cleanup 
> labels.
> - Restore the none backend after bitmap removal and 
> creation/load
>   failures so bitmap/location stays available.
>
> Validation:
>   - create a RAID1 array with --bitmap=none
>   - verify /sys/block/md0/md/bitmap/location exists and reports 
>   "none"
>   - mdadm --grow /dev/md0 --bitmap=internal
>   - verify location switches to "+8", mdadm reports "Intent 
>   Bitmap:
>     Internal", and /proc/mdstat reports a bitmap
>   - mdadm --grow /dev/md0 --bitmap=none
>   - verify location switches back to "none" and only the common 
>   location
>     attribute remains under md/bitmap
>   - repeat the internal/none switch once more
> - Checked the QEMU serial log for panic, Oops, BUG, WARNING, 
> Call Trace,
>   RCU stall, and hung-task patterns; none were found.
>
> Yu Kuai (3):
>   md: factor bitmap creation away from sysfs handling
>   md/md-bitmap: split bitmap sysfs groups
>   md/md-bitmap: add a none backend for bitmap grow
>

Thanks for all.
Would you like to add tag Fixes: fb8cc3b0d9db for the whole series 
while merging?

--
Su

>  drivers/md/md-bitmap.c   | 131 
>  +++++++++++++++++++++++++++++++++++----
>  drivers/md/md-bitmap.h   |   2 +-
>  drivers/md/md-llbitmap.c |   7 ++-
>  drivers/md/md.c          | 125 
>  ++++++++++++++++++++++++++-----------
>  drivers/md/md.h          |   3 +
>  5 files changed, 218 insertions(+), 50 deletions(-)
>
> base-commit: c85d314b135ff569c1031f2ef8e40368bcfe72ac