Re: [RFC v1 0/4] xfs: Add support to shrink multiple empty rtgroups

["Nirjhar Roy (IBM)" <nirjhar.roy.lists@gmail.com>]

On 2/19/26 11:33, Nirjhar Roy (IBM) wrote:
> From: "Nirjhar Roy (IBM)" <nirjhar.roy.lists@gmail.com>
>
> This work is based on a previous RFC[1] by Gao Xiang and various ideas
> proposed by Dave Chinner in the RFC[1].
>
> The patch begins with the re-introduction of some of the data
> structures that were removed, some code refactoring and
> finally the patch that implements the multi rtgroup shrink design.
> We can remove only those rtgroups which are empty.
> For non-empty rtgroups the rtextents can migrated to other rtgroups
> (assuming the required amount of space is available).
> I am working on the patch series [2](by Darrick and
> Dave) for completion of the data block migration from the end of the
> filesystem for emptying an realtime group. That will be a future work
> after this.
> The final patch has all the details including the definition of the
> terminologies and the overall design.
>
> The design is quite similar to the design of data AG removal implemented
> in the patch series[3] that I have posted earlier.
> The reason for keeping [3] on hold and posting this patch series is
> that (based on the discussion in [5], [6]), realtime devices won't have any
> metadata/inodes and migrating data from the end of realtime devices will
> be simpler. On the other hand there are challenges in moving metadata
> from regular AGs especially inodes.
>
> Please note that I have added RBs from Darrick in patch 1 which was
> given in [4].
>
> Instructions to test this patch:
> $ Apply the patch for xfsprogs sent with this series and install it.
> $ mkfs.xfs -f -m metadir=1  -r rtdev=/dev/loop2,extsize=4096,rgcount=4,size=1G \
> 	-d size=1G /dev/loop1
> $ mount -o rtdev=/dev/loop2 /dev/loop1 /mnt/scratch
> $ # shrink by 1.5 rtgroups
> $ xfs_growfs -R $(( 65536 * 2 + 32768 ))  /mnt1/scratch
>
> I have also sent the tests.
>
> [1] https://lore.kernel.org/all/20210414195240.1802221-1-hsiangkao@redhat.com/
> [2] https://lore.kernel.org/linux-xfs/173568777852.2709794.6356870909327619205.stgit@frogsfrogsfrogs/
> [3] https://lore.kernel.org/linux-xfs/cover.1760640936.git.nirjhar.roy.lists@gmail.com/
> [4] https://lore.kernel.org/all/20250729202632.GF2672049@frogsfrogsfrogs/
> [5] https://lore.kernel.org/linux-xfs/aPnMk_2YNHLJU5wm@infradead.org/
> [6] https://lore.kernel.org/linux-xfs/aPiFBxhc34RNgu5h@infradead.org/

Hi Christoph and Darrick,
I am preparing a v2 incorporating all the initial review feedback 
received so far. In parallel, I am looking into adding shrinkfs support 
for zoned XFS  -  however, it would be great if we can discuss the 
current design and get a full review of the changes so far to get this 
work (shrinkfs for non-zoned realtime groups) into proper shape for the 
upcoming merge window first and submit zoned XFS shrinkfs support 
separately afterward. Do you think that make sense?

--NR

>
> Nirjhar Roy (IBM) (4):
>    xfs: Re-introduce xg_active_wq field in struct xfs_group
>    xfs: Introduce xfs_rtginodes_ensure_all()
>    xfs: Add a new state for shrinking
>    xfs: Add support to shrink multiple empty realtime groups
>
>   fs/xfs/libxfs/xfs_group.c     |  18 +-
>   fs/xfs/libxfs/xfs_group.h     |   4 +
>   fs/xfs/libxfs/xfs_rtgroup.c   | 105 ++++-
>   fs/xfs/libxfs/xfs_rtgroup.h   |  31 ++
>   fs/xfs/xfs_buf_item_recover.c |  25 +-
>   fs/xfs/xfs_extent_busy.c      |  30 ++
>   fs/xfs/xfs_extent_busy.h      |   2 +
>   fs/xfs/xfs_inode.c            |   8 +-
>   fs/xfs/xfs_mount.h            |   3 +
>   fs/xfs/xfs_rtalloc.c          | 824 +++++++++++++++++++++++++++++++++-
>   fs/xfs/xfs_trans.c            |   1 -
>   11 files changed, 1023 insertions(+), 28 deletions(-)
>
> --
> 2.43.5
>
-- 
Nirjhar Roy
Linux Kernel Developer
IBM, Bangalore