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smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-c2dff70000001609-de-693f996afb50 Date: Mon, 15 Dec 2025 14:15:17 +0900 From: Byungchul Park To: Jeff Layton Cc: linux-kernel@vger.kernel.org, kernel_team@skhynix.com, torvalds@linux-foundation.org, damien.lemoal@opensource.wdc.com, linux-ide@vger.kernel.org, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, will@kernel.org, tglx@linutronix.de, rostedt@goodmis.org, joel@joelfernandes.org, sashal@kernel.org, daniel.vetter@ffwll.ch, duyuyang@gmail.com, johannes.berg@intel.com, tj@kernel.org, tytso@mit.edu, willy@infradead.org, david@fromorbit.com, amir73il@gmail.com, gregkh@linuxfoundation.org, kernel-team@lge.com, linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, minchan@kernel.org, hannes@cmpxchg.org, vdavydov.dev@gmail.com, sj@kernel.org, jglisse@redhat.com, dennis@kernel.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, vbabka@suse.cz, ngupta@vflare.org, linux-block@vger.kernel.org, josef@toxicpanda.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, dan.j.williams@intel.com, hch@infradead.org, djwong@kernel.org, dri-devel@lists.freedesktop.org, rodrigosiqueiramelo@gmail.com, melissa.srw@gmail.com, hamohammed.sa@gmail.com, harry.yoo@oracle.com, chris.p.wilson@intel.com, gwan-gyeong.mun@intel.com, max.byungchul.park@gmail.com, boqun.feng@gmail.com, longman@redhat.com, yunseong.kim@ericsson.com, ysk@kzalloc.com, yeoreum.yun@arm.com, netdev@vger.kernel.org, matthew.brost@intel.com, her0gyugyu@gmail.com, corbet@lwn.net, catalin.marinas@arm.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, luto@kernel.org, sumit.semwal@linaro.org, gustavo@padovan.org, christian.koenig@amd.com, andi.shyti@kernel.org, arnd@arndb.de, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mcgrof@kernel.org, petr.pavlu@suse.com, da.gomez@kernel.org, samitolvanen@google.com, paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, urezki@gmail.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, chuck.lever@oracle.com, neil@brown.name, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, trondmy@kernel.org, anna@kernel.org, kees@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, mark.rutland@arm.com, ada.coupriediaz@arm.com, kristina.martsenko@arm.com, wangkefeng.wang@huawei.com, broonie@kernel.org, kevin.brodsky@arm.com, dwmw@amazon.co.uk, shakeel.butt@linux.dev, ast@kernel.org, ziy@nvidia.com, yuzhao@google.com, baolin.wang@linux.alibaba.com, usamaarif642@gmail.com, joel.granados@kernel.org, richard.weiyang@gmail.com, geert+renesas@glider.be, tim.c.chen@linux.intel.com, linux@treblig.org, alexander.shishkin@linux.intel.com, lillian@star-ark.net, chenhuacai@kernel.org, francesco@valla.it, guoweikang.kernel@gmail.com, link@vivo.com, jpoimboe@kernel.org, masahiroy@kernel.org, brauner@kernel.org, thomas.weissschuh@linutronix.de, oleg@redhat.com, mjguzik@gmail.com, andrii@kernel.org, wangfushuai@baidu.com, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-i2c@vger.kernel.org, linux-arch@vger.kernel.org, linux-modules@vger.kernel.org, rcu@vger.kernel.org, linux-nfs@vger.kernel.org, linux-rt-devel@lists.linux.dev, 2407018371@qq.com, dakr@kernel.org, miguel.ojeda.sandonis@gmail.com, neilb@ownmail.net, bagasdotme@gmail.com, wsa+renesas@sang-engineering.com, dave.hansen@intel.com, geert@linux-m68k.org, ojeda@kernel.org, alex.gaynor@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, rust-for-linux@vger.kernel.org Subject: Re: [PATCH v18 41/42] SUNRPC: relocate struct rcu_head to the first field of struct rpc_xprt Message-ID: <20251215051517.GB49936@system.software.com> References: <20251205071855.72743-1-byungchul@sk.com> <20251205071855.72743-42-byungchul@sk.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0yTZxiG837nFko+OpivsOhSJXMaRBe3PMmM29yPfdkfl+3Hkrlk68Y3 aTjVFtCaGMtJGauu0xRC67RF6JgrhnHY5NCIzBQZNC0QpTOwFsQKKbCNCKZIZf0gy/jz5M79 3M99vT9ejlS2M2mcpqBI1BWo81SMnJLPJzoyc+ve0uw7P/gSjAenabhf2kvB3bEyCoJLVQjW 3B4EAf8tElztpQTUzpZS8JfThMAatrEwH+ymIVaTC1fr2xiI1PzNwDOvj4Raix+BY3KChMXZ EIJ2z58I3E1lDDwyd5AwOp0ECy0M2MvcNAwPRRB8b7uIIPzATUBnqIuF4cgqAUFnmIJBc70E ZaDm5y1gqy0n4mOGAEtzNwFR53UWhq6NU+A0ZoDNO0rDVJOVhdXJ/bBmLwTPT49ZuDHvoyES vshAsP8sDb8aQyy4TGESqrqWKGh9eJ+GHvcABVWxJwg8N6cIGO26zICppYMGo+0pDf7eQRoa x4YJmAwFaGjzDpGwfCEdAuZHCC4thNHb2ULlSIwRXFdcSHjSWE4Klea4ahycY4SVpXuM4F62 U8Lv9Vho+HqFEL7zZgqd1glWsLcWCxV35mmhrWm3cK1nlhAci0v0B5mfyA9mi3maElGXdehz ec5i+TirvfriyWj3diP6lq9GMg7zB3DFmoeuRty6dj/fJdkUn4HH7sUYSTP8KzgQiJJSJIXf iR8YNdVIzpG8ZRuem1mhpMwL/DHc0mkhJa3gAbtnbpFSSMnbEXbUuNiNRTIeqJtePyDjpatX RtZLST4d//Cc27C34/IO27ot4wU8+41BslP5Hbj3l35CqsT8ggw77/rIjedvxbebApQZJVs3 EaybCNb/CdZNBDuiriOlpqAkX63JO7A3x1CgObn3y8L8VhT/y87Tq0dvokX/R32I55AqUeFv P6RR0uoSvSG/D2GOVKUoqgJxS5GtNpwSdYWf6YrzRH0fSuco1RbFa8snspX8MXWRmCuKWlH3 35bgZGlGtGeX1p/00PJ0YLL49X9efTfhi/7pZhe7w3TYPJZwPulc8puhUpt4JrIno/qr2+Ej lcffSHy5Qryckko0RHs+ftw/fvTH0760DynXH+zUkRsOx05edkcbeC/fkDV3JrjNxDSMZA1/ OnNB8U7dYdbrS0htvjQR5bfqi96P/aaVTXSaM1SUPke9fzep06v/BfYi22nHAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA02SbUxbZRTH89zn9t5LtcsFcTzZjDOdi2buReNMjlG3GZPxxDizxA/LFhOp 2824AwppkVGNSqnName2rqZF2rG1KJVAHW/bFEldAxOdE0YZSMPLgKwyCEwMFrYWCrYsRr6c /M///M8v58MRcMaX3AZB1hZLOq0mX80pWeXbr5i2H6/cIz/fFdgKFvOnMDwaUcAfxiAL81EL C+ca/Bwk3N/zYGmuVMCvA+Us9FysRzA6b0Fwf9GNwdy6wkLC3slDNDbEg8OIYCXQicAZsmMI 91zF4L9kZOCfxmUOpjvmEDjGIxxUTBlZmPV9gcA14eZh6udsuDfapoCVkbsMDCzMIPBFlhmI BE8iSDjz4EJ1S3Ld+TcHi103MVQ4ehB4x0cwzE2NIbjUeRtBoLacgz9tlzHciqyDvvlZDq47 TnFwL3SOgb8aOfCUBxQQ+n0aQZXbjmBiMMCA6esGDpxVzSy0jv3IQ2h6iYFhp52B+ub9MOqb YOGGrZpJnptMNWWBu8LEJMskA47v2hiI+er4vTWI3jefZmldyxWGmnsTHPWf9yO6GLcjGq0x YWq2JduOmVlMP2s5QWtuzHA0Pt/P0cCCh6W/VRP6zedxhp7t2k5bXSP8gdcPK189KuXLJZJu 5+4cZe6caZgvurC+NNa2qQydEa1IEIi4iwSWn7WiNIEVt5CB/gSX0pz4DAmHYzgVyRSfJoNl shUpBSw6niQzk3E2lXlMPEYaWx04pVUikMDkVZwKZYgeRLxOP/9wkE6uV0ZWF3ASunS+dxWK xY3k22Xhob2JmC67V+00kZKpU4aU/bi4mQSv/MLY0DrXGpBrDcj1P8i1BuRBbB3KlLUlBRo5 /6Ud+rxcg1Yu3XGksKAZJV/V9/HS2R9Q9FZ2OxIFpH5UFW7bLWcoNCV6Q0E7IgJWZ6os4aSl OqoxfCjpCt/TfZAv6dvRRoFVZ6nePCjlZIjHNMVSniQVSbr/poyQtqEMXfvkq13vW2ZdQWuY dMefe6Ij54j13TdO9598ai5EFofEvvTgcPYd7519fnrxTJWye/Px2sOG17r3+uvWNyTe2jlo Gw9n5WiMRfv3NDnQOx/x3n1jL9tevG3sS1uY8Dy4+WDbCm1K9/Qe3PbIoWis9NqQ8W7Em1Vf LGsLa/UlP52wqVl9ruaFrVin1/wLMb4wZaYDAAA= X-CFilter-Loop: Reflected On Fri, Dec 05, 2025 at 04:27:52AM -0500, Jeff Layton wrote: > On Fri, 2025-12-05 at 16:18 +0900, Byungchul Park wrote: > > While compiling Linux kernel with DEPT on, the following error was > > observed: > > > > ./include/linux/rcupdate.h:1084:17: note: in expansion of macro > > ‘BUILD_BUG_ON’ > > 1084 | BUILD_BUG_ON(offsetof(typeof(*(ptr)), rhf) >= 4096); \ > > | ^~~~~~~~~~~~ > > ./include/linux/rcupdate.h:1047:29: note: in expansion of macro > > 'kvfree_rcu_arg_2' > > 1047 | #define kfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf) > > | ^~~~~~~~~~~~~~~~ > > net/sunrpc/xprt.c:1856:9: note: in expansion of macro 'kfree_rcu' > > 1856 | kfree_rcu(xprt, rcu); > > | ^~~~~~~~~ > > CC net/kcm/kcmproc.o > > make[4]: *** [scripts/Makefile.build:203: net/sunrpc/xprt.o] Error 1 > > > > Since kfree_rcu() assumes 'offset of struct rcu_head in a rcu-managed > > struct < 4096', the offest of struct rcu_head in struct rpc_xprt should > > not exceed 4096 but does, due to the debug information added by DEPT. > > > > Relocate struct rcu_head to the first field of struct rpc_xprt from an > > arbitrary location to avoid the issue and meet the assumption. > > > > Reported-by: Yunseong Kim > > Signed-off-by: Byungchul Park > > --- > > include/linux/sunrpc/xprt.h | 9 ++++++++- > > 1 file changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h > > index f46d1fb8f71a..666e42a17a31 100644 > > --- a/include/linux/sunrpc/xprt.h > > +++ b/include/linux/sunrpc/xprt.h > > @@ -211,6 +211,14 @@ enum xprt_transports { > > > > struct rpc_sysfs_xprt; > > struct rpc_xprt { > > + /* > > + * Place struct rcu_head within the first 4096 bytes of struct > > + * rpc_xprt if sizeof(struct rpc_xprt) > 4096, so that > > + * kfree_rcu() can simply work assuming that. See the comment > > + * in kfree_rcu(). > > + */ > > + struct rcu_head rcu; > > + > > struct kref kref; /* Reference count */ > > const struct rpc_xprt_ops *ops; /* transport methods */ > > unsigned int id; /* transport id */ > > @@ -317,7 +325,6 @@ struct rpc_xprt { > > #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) > > struct dentry *debugfs; /* debugfs directory */ > > #endif > > - struct rcu_head rcu; > > const struct xprt_class *xprt_class; > > struct rpc_sysfs_xprt *xprt_sysfs; > > bool main; /*mark if this is the 1st transport */ > > Seems fine to me. > > Reviewed-by: Jeff Layton Thank you, Jeff. Byungchul