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bh=NomRgZhAnCadauaNPou4fifv4G+IJxYhxbkOJyVdeaY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gC9tn+qCRdX2PPavqpJdx8Gqi2XJrpEt/lxYjeSZMFH1MkwOPTnWeGZSSFyrivHHz y+G2Ujnzj5zWphHDQNoj18ubFP9kBGdM1QlEVrI/nK1xvmeQH5ySs/ol0TpkotjjJb /sP1lQwiBZp3nUCCxtQ1UZ3IMNi7g58hng+JOqyw= Date: Tue, 28 Feb 2023 11:13:10 -0800 From: Andrew Morton To: Jiri Olsa Cc: Alexei Starovoitov , Andrii Nakryiko , Hao Luo , Alexander Viro , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Matthew Wilcox , bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Daniel Borkmann , Namhyung Kim Subject: Re: [PATCH RFC v2 bpf-next 1/9] mm: Store build id in inode object Message-Id: <20230228111310.05f339a0a1a00e919859ffad@linux-foundation.org> In-Reply-To: <20230228093206.821563-2-jolsa@kernel.org> References: <20230228093206.821563-1-jolsa@kernel.org> <20230228093206.821563-2-jolsa@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 19E35120017 X-Stat-Signature: nu4d7f3duf1x1znzf5eqddmjhm53pq9t X-HE-Tag: 1677611592-369083 X-HE-Meta: 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 OeyXyLpq W57uvoZ1zt+UMqF8Z75QBw/rF0fOu3JU0/h+ZGXkkJUOlbUhVwUoneOaoY5BQern6EcAiE1cZVwfJLtSVmHkO4f51iijAs8siVCVcUw0TkDAcG3SYB6Qd2Zy6MEvyKEs7U9tTNyf7PT+8sNQxEYVLsckXBdP4ZUtmo4C93nqXHXjhznwHZAzeSPZ1z5KCyoC87WbXeogC6zdr8miJLsTm1BnpN/KoLqsyB0PWdy3YuzlXd9XzCC8fDPDQRxng+tly/vvUdgD637k0iPTiVtf1eJihnVD0AoTduC0OZ1MKcKxQn/4ywiApPxXgo0+ObMPS30JTV6w+SwaH6TQSFqpOfK73jMJLuXKzk6KfznHwpnomwByJxmMrCmw4r/6DbHgJm/PiPzY3ExUFhtEpQCwlpkWPGt89fj8slxd8BGWm1esxIUijCvdCzLMGsR+pOEj7d70kn61CaT/pmTRzSAdKLvboNQcJIyIyaQ5F 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: On Tue, 28 Feb 2023 10:31:58 +0100 Jiri Olsa wrote: > Storing build id in file's inode object for elf executable with build > id defined. The build id is stored when file is mmaped. > > This is enabled with new config option CONFIG_INODE_BUILD_ID. > > The build id is valid only when the file with given inode is mmap-ed. > > We store either the build id itself or the error we hit during > the retrieval. > > ... > > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -699,6 +700,12 @@ struct inode { > struct fsverity_info *i_verity_info; > #endif > > +#ifdef CONFIG_INODE_BUILD_ID > + /* Initialized and valid for executable elf files when mmap-ed. */ > + struct build_id *i_build_id; > + spinlock_t i_build_id_lock; > +#endif > + Remember we can have squillions of inodes in memory. So that's one costly spinlock! AFAICT this lock could be removed if mmap_region() were to use an atomic exchange on inode->i_build_id? If not, can we use an existing lock? i_lock would be appropriate (don't forget to update its comment). Also, the code in mmap_region() runs build_id_free() inside the locked region, which seems unnecessary.