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b=ZXHKEJiHam3Z2xUpQMDGRKdXcZRxWTOI/dwRFHVYOszxIyjzXh/2KukXPW5tcl6+v 5qXOQIL9wrwUJHtf5jzaTWLy2Z83KOGJeqqy6Buv03l9TZqulFqoiLscBARN4GZGzX Fr3btU8qMBKAe5LomhIa2cKvT2m8V8Cka5j4wJgcTBrUwd/lWbXW73ScaIkA1yLcn3 a0u65q04EujCObMXKy8nWmY1Jz/aCW7m+k+LDlbgTOkkFX2Cs/H3xlwLiBZ2cAejsf tY3qJke5nvl+aDB0xe9MuWUD5j1YJvx470DP3iuL4299Zxj3vJSTktKdKzQ/pNadu+ oq8pn8LPrT5FA== Date: Thu, 01 Oct 2026 08:43:41 -1000 Message-ID: From: Tejun Heo To: Liz Fong-Jones Cc: Christian Brauner , Jan Kara , Alexander Viro , Jens Axboe , Andrew Morton , Johannes Weiner , Roman Gushchin , Shakeel Butt , Xin Yin , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, ian@honeycomb.io Subject: Re: [PATCH v4 1/2] writeback: let foreign flushes reach dying cgwbs In-Reply-To: <20260930-wb-dying-cgwb-flush-v4-1-bde637803a96@honeycomb.io> References: <20260930-wb-dying-cgwb-flush-v4-0-bde637803a96@honeycomb.io> <20260930-wb-dying-cgwb-flush-v4-1-bde637803a96@honeycomb.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 891C5C0002 X-Stat-Signature: smapbqbziwkgcnkgk67mhwzfrbodp91q X-Rspam-User: X-HE-Tag: 1790880222-651612 X-HE-Meta: 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 iJPp8f3L eP09FsjfyOxEKYErvjlExpkqqV5Go/yoWifX7Gv0SgPnnXPAnbSO8KlHavHf6RbicgSNBlrquFn4ajzeMzW9wr2SI5PmtD5uR/v8OqblmBdNpHEkvJqmQLOdBIzNy07vOPva9yU895i3hLG6SQiGIyAsicqW/pcHqDBbJ5gMh89VGE8U2ef+nf3UJGONB8tgJ0n9zuxCEQ1ZiGR0qD78fM6jsk5eFYa5ucRd22KkejjU/NleEhkgr8RS4zcyPDPUWQ5Kp Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, Liz. On Wed, Sep 30, 2026 at 07:35:37PM +0000, Liz Fong-Jones wrote: > if (test_bit(WB_registered, &bdi->wb.state) && > - blkcg_cgwb_list->next && memcg_cgwb_list->next) { > + blkcg_cgwb_list->next && memcg_cgwb_list->next && > + !css_is_dying(memcg_css)) { With patch 2 switching a replaced wb's inodes to its successor instead of flushing them in place, this doesn't matter anymore. If a removed memcg's wb gets replaced, the successor takes over the inodes and stays in the tree until released, so foreign flushes still reach them. I asked for it against v3, where patch 2 only kicked writeback on the old wb. Can you drop it and the description sentence about it? Thanks. -- tejun