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[50.207.252.210]) by smtp.gmail.com with ESMTPSA id v83-v6sm51265542pfa.103.2018.10.20.14.40.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 20 Oct 2018 14:40:22 -0700 (PDT) Subject: Re: [PATCH 0/2] block: fixes for always associate blkg To: Dennis Zhou Cc: Tejun Heo , Valdis Kletnieks , kernel-team@fb.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <20181020185612.51587-1-dennis@kernel.org> From: Jens Axboe Message-ID: Date: Sat, 20 Oct 2018 15:40:22 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181020185612.51587-1-dennis@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/20/18 12:56 PM, Dennis Zhou wrote: > Hi everyone, > > It was reported in [1] that blk_get_rl() cleanup patch was causing a > null pointer dereference. After some back and forth debugging with > Valdis, it turns out I wasn't properly handling association with > recursive calls to make_request(). > > Another issue was identified with the blk_get_rl() update as it is > possible under certain circumstances that a blkg cannot be allocated > when called in blk_get_rl(). This could result in the blkcg_root being > returned. However, the blkcg_root is a special case where all blkgs > share the request_queue's request_list. > > The original series can be found at [2]. > > [1] https://lore.kernel.org/lkml/13987.1539646128@turing-police.cc.vt.edu/ > [2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/ > > This patchset contains the following 2 patches: > 0001-blkcg-fix-edge-case-for-blk_get_rl-under-memory-pres.patch > 0002-blkcg-reassociate-bios-when-make_request-is-called-r.patch > > 0001 addresses an edge case where a blkg cannot be created and can > possibly return a blkg associated with the blkcg_root. 0002 fixes the > stale association when make_request() is called recursively. Thanks Dennis, applied. -- Jens Axboe