Re: [PATCH v7 0/3] writeback: let foreign flushes reach dying cgwbs

[Christian Brauner]

On Thu, 15 Oct 2026 11:40:46 +0000, Liz Fong-Jones wrote:
> writeback: let foreign flushes reach dying cgwbs
> 
> At Honeycomb, a container that reads from Kafka and writes columnar
> files to a host volume stalls for 30-60s after each deploy replaces it
> (v6.18). We're increasingly confident this is the cause: the stall
> looks the same as in the reproducer (little CPU use, lag growing
> linearly and then recovering), and the mitigation it predicts, moving
> our final syncfs after the last write, worked in production (below).
> We haven't caught it with probes in production yet.
> 
> [...]

Applied to the vfs-7.5.writeback branch of the vfs/vfs.git tree.
Patches in the vfs-7.5.writeback 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-7.5.writeback

[1/3] writeback: clear the old wb's dirty IO state after switching inodes
      https://git.kernel.org/vfs/vfs/c/d70ddc66a4ed
[2/3] writeback: let foreign flushes reach dying cgwbs
      https://git.kernel.org/vfs/vfs/c/27f228cac83e
[3/3] writeback: switch a replaced cgwb's inodes to its successor
      https://git.kernel.org/vfs/vfs/c/90158789e8a5