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[2001:468:c80:2103:f21f:afff:fe0c:8ada]) by smtp.gmail.com with ESMTPSA id y190-v6sm8314539qkc.84.2018.10.16.09.12.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 16 Oct 2018 09:12:14 -0700 (PDT) From: valdis.kletnieks@vt.edu X-Google-Original-From: Valdis.Kletnieks@vt.edu X-Mailer: exmh version 2.8.0 04/21/2017 with nmh-1.7+dev To: "Theodore Y. Ts'o" , Dennis Zhou , Jens Axboe , Tejun Heo Cc: linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [BUG] ext4/block null pointer crashes in linux-next In-Reply-To: <66480.1539693734@turing-police.cc.vt.edu> References: <13987.1539646128@turing-police.cc.vt.edu> <20181016015201.GB18547@thunk.org> <66480.1539693734@turing-police.cc.vt.edu> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1539706333_2381P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Tue, 16 Oct 2018 12:12:13 -0400 Message-ID: <12638.1539706333@turing-police.cc.vt.edu> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1539706333_2381P Content-Type: text/plain; charset=us-ascii On Tue, 16 Oct 2018 08:42:14 -0400, valdis.kletnieks@vt.edu said: > [~] zgrep CGROUP /proc/config.gz > CONFIG_CGROUPS=y > CONFIG_BLK_CGROUP=y > # CONFIG_DEBUG_BLK_CGROUP is not set > (...) > Looks like I should enable DEBUG_BLK_CGROUP and see what that says. Built next-20181016 with that enabled - and the exact same kablam. Started looking at the code, and I noticed that if the .config has CONFIG_IOSCHED_CFQ=y # CONFIG_CFQ_GROUP_IOSCHED is not set CONFIG_BLK_CGROUP=y then the 'struct cfqg_stats' at line 185 of block/cfq-iosched.c ends up being zero length (which hints that combo of config variables is a pathological case). I haven't delved through all the #ifdef'ery, but I wonder if there may be other corner-case issues with that combo.... --==_Exmh_1539706333_2381P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Comment: Exmh version 2.8.0 04/21/2017 iQEVAwUBW8YN3Y0DS38y7CIcAQKm1Af9E7hXxt6027MX7A17TQoxeQAQZXV4hw+I /kyOqhvtGZuEr+BQdtXAUpDlQwPs74uQOByPy08dvleO7DwZvS6jbdtZEPyW/kxD Y1y1SahHpyRXAx2ngE6WSv2kzNGV9KgU5RKMcBNSpX53wM5eRNk+meRPXqgqVaLL dTe3QL1mcmWrsOX3d35uYbi15q0+2nkXDD7M1oZVaCDenVzxZ8W07KzjzD+swClc SQV2gQdXnEFBQeEEPuYQQI1Uzy8CItVI+bJ6yO1vc336vtu66sN2w0XIAB2AYi/N zPbZMcXA+rp37FHc+uYRJBqOSqGfFGBqZNQj97Gc0yO6k3SaI1uhCA== =X1MR -----END PGP SIGNATURE----- --==_Exmh_1539706333_2381P--