Re: [PATCH v2] writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes

[Christian Brauner]

On Fri, 11 Sep 2026 18:49:49 +0000, Patrick Lu (Anthropic) wrote:
> cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes
> per call and is called again until the dying wb is drained, but every
> call walks wb->b_attached and then wb->b_dirty_time from the same end.
> Inodes already prepared (they stay on the list with I_WB_SWITCH set
> until the switch worker runs) and inodes that cannot be switched
> (I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb)
> stay where they are, so each pass rescans a growing run of them under
> wb->list_lock and a full drain is quadratic in the number of inodes on
> the list. With ~17M inodes attached to one dying cgwb we saw this end
> in soft lockups, with CPUs reported stuck for 21-48s.
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.fixes

[1/1] writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes
      https://git.kernel.org/vfs/vfs/c/f6988c90671e