Re: [PATCH v5 2/3] writeback: let foreign flushes reach dying cgwbs

[Tejun Heo]

Hello, Liz.

On Thu, Oct 01, 2026 at 11:50:20PM +0000, Liz Fong-Jones wrote:
> + * The wb may have been killed and its blkcg association may be stale.  This
> + * is what foreign flushes want: they target the wb that owns the dirty
> + * inodes, which can be a killed one.  Use wb_get_create() to get a wb to
> + * attach inodes to.

The next patch attaches inodes to what this returns. Maybe just say that it
returns the wb in @memcg_css's slot, killed or not?

> + * This function uses css_get() on @memcg_css and thus expects its refcnt
> + * to be positive on invocation.  IOW, rcu_read_lock() protection on
> + * @memcg_css isn't enough.  try_get it before calling this function.

This describes cgwb_create(), so wb_get_create() is where it belongs.

The struct bdi_writeback comment in backing-dev-defs.h and wb_dying()'s
still describe the old lifetime rule. Can you update them too?

Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Thanks.

--
tejun