From: Tejun Heo <tj@kernel.org>
To: Liz Fong-Jones <lizf@honeycomb.io>
Cc: Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Jens Axboe <axboe@kernel.dk>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Xin Yin <yinxin.x@bytedance.com>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
ian@honeycomb.io
Subject: Re: [PATCH v5 2/3] writeback: let foreign flushes reach dying cgwbs
Date: Fri, 02 Oct 2026 09:21:11 -1000 [thread overview]
Message-ID: <ccbcb8e5f806ae1d29164b53551d61ef@kernel.org> (raw)
In-Reply-To: <20261001-wb-dying-cgwb-flush-v5-2-8361eb8c65c6@honeycomb.io>
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@kernel.org>
Thanks.
--
tejun
next prev parent reply other threads:[~2026-10-02 19:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-01 23:50 [PATCH v5 0/3] " Liz Fong-Jones
2026-10-01 23:50 ` [PATCH v5 2/3] " Liz Fong-Jones
2026-10-02 19:21 ` Tejun Heo [this message]
2026-10-01 23:50 ` [PATCH v5 1/3] writeback: clear the old wb's dirty IO state after switching inodes Liz Fong-Jones
2026-10-02 19:21 ` Tejun Heo
2026-10-01 23:50 ` [PATCH v5 3/3] writeback: switch a replaced cgwb's inodes to its successor Liz Fong-Jones
2026-10-02 19:23 ` Tejun Heo
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