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Wed, 20 Nov 2024 10:18:17 +0000 (GMT) Date: Wed, 20 Nov 2024 15:48:15 +0530 From: Ojaswin Mujoo To: Genes Lists Cc: song@kernel.org, yukuai3@huawei.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, linux@leemhuis.info Subject: Re: md-raid 6.11.8 page fault oops Message-ID: References: <0b579808e848171fc64e04f0629e24735d034d32.camel@sapience.com> <34333c67f5490cda041bc0cbe4336b94271d5b49.camel@sapience.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: reiykG7LFyPxA9MFJVI11BYNXOsDmKG9 X-Proofpoint-ORIG-GUID: reiykG7LFyPxA9MFJVI11BYNXOsDmKG9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 phishscore=0 mlxscore=0 malwarescore=0 mlxlogscore=711 adultscore=0 priorityscore=1501 bulkscore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2411200070 On Tue, Nov 19, 2024 at 08:31:02AM -0500, Genes Lists wrote: > On Tue, 2024-11-19 at 17:04 +0530, Ojaswin Mujoo wrote: > > > > ... > > > >  (gdb) list *(rb_first+0x13) > > >   0xffffffff81de1af3 is in rb_first (lib/rbtree.c:473). > > >   468       struct rb_node  *n; > > >   469 > > >   470       n = root->rb_node; > > >   471       if (!n) > > >   472           return NULL; > > >   473       while (n->rb_left) > > > > Now this looks strange, we already make sure n is not NULL and then > > somehow this line ends up in > > > >  BUG: unable to handle page fault for address: 0000000000200010 > > > > Now, decoding the code with an x86 vmlinux, I see the fauling opcode > > faulting: > > > > Code starting with the faulting instruction > > =========================================== > >    0:   0f 1f 80 00 00 00 00    nopl   0x0(%rax) > >    7:   90                      nop > >    8:   90                      nop > >    9:   90                      nop > >    a:   90                      nop > >    b:   90                      nop > >    c:   90                      nop > >    d:   90                      nop > >    e:   90                      nop > >    f:   90                      nop > > > > Now RAX is 0x200000 but I don't think the nopl instruction should > > have resulted > > in a mem access AFA my limited understanding of x86 ISA goes. > > > > I also don't see nopl in my vmlinux in rb_first, my binary being > > compiled with > > gcc 8.5. Are you by chance using clang or higher version or higher > > optimization in gcc. > > > > Regards, > > ojaswin > > I am using Arch toolchain with  > >    gcc 14.2.1+r134+gab884fffe3fc-1 > > I do not set CFLAGS_KERNEL  so compile options are the default. Got it, I'm still not sure what might be causing this oops. Would you happen to a have a reproducer that I can play around with on my system? Regards, ojaswin > > thanks > > gene > >