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Fri, 04 Jun 2021 08:51:04 -0700 (PDT) Received: from localhost ([199.192.137.73]) by smtp.gmail.com with ESMTPSA id z136sm1079735qkb.34.2021.06.04.08.51.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Jun 2021 08:51:03 -0700 (PDT) Date: Fri, 4 Jun 2021 11:51:02 -0400 From: Tejun Heo To: Roman Gushchin Cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Dennis Zhou , Dave Chinner , cgroups@vger.kernel.org Subject: Re: [PATCH v7 6/6] writeback, cgroup: release dying cgwbs by switching attached inodes Message-ID: References: <20210604013159.3126180-1-guro@fb.com> <20210604013159.3126180-7-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210604013159.3126180-7-guro@fb.com> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 896F0A00027E Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=bY59MWvf; spf=pass (imf15.hostedemail.com: domain of htejun@gmail.com designates 209.85.160.170 as permitted sender) smtp.mailfrom=htejun@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-Stat-Signature: h4xhnpm67ijiaswwtskfgiy3ueprtktc X-HE-Tag: 1622821856-108990 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, On Thu, Jun 03, 2021 at 06:31:59PM -0700, Roman Gushchin wrote: > +bool cleanup_offline_cgwb(struct bdi_writeback *wb) > +{ > + struct inode_switch_wbs_context *isw; > + struct inode *inode; > + int nr; > + bool restart = false; > + > + isw = kzalloc(sizeof(*isw) + WB_MAX_INODES_PER_ISW * > + sizeof(struct inode *), GFP_KERNEL); > + if (!isw) > + return restart; > + > + /* no need to call wb_get() here: bdi's root wb is not refcounted */ > + isw->new_wb = &wb->bdi->wb; Not a deal breaker but I wonder whether it'd be safer to migrate it to the nearest live ancestor rather than directly to the root. As adaptive migration isn't something guaranteed, there's some chance that this can behave as escape-to-root path in pathological cases especially for inodes which may be written to by multiple cgroups. Thanks. -- tejun