Mo Zou, Haoran Ding, Dong Du, Ming Fu, Ronghui Gu, Haibo Chen
{"title":"Using concurrent relational logic with helpers for verifying the AtomFS file system","authors":"Mo Zou, Haoran Ding, Dong Du, Ming Fu, Ronghui Gu, Haibo Chen","doi":"10.1145/3341301.3359644","DOIUrl":null,"url":null,"abstract":"Concurrent file systems are pervasive but hard to correctly implement and formally verify due to nondeterministic interleavings. This paper presents AtomFS, the first formally-verified, fine-grained, concurrent file system, which provides linearizable interfaces to applications. The standard way to prove linearizability requires modeling linearization point of each operation---the moment when its effect becomes visible atomically to other threads. We observe that path inter-dependency, where one operation (like rename) breaks the path integrity of other operations, makes the linearization point external and thus poses a significant challenge to prove linearizability. To overcome the above challenge, this paper presents Concurrent Relational Logic with Helpers (CRL-H), a framework for building verified concurrent file systems. CRL-H is made powerful through two key contributions: (1) extending prior approaches using fixed linearization points with a helper mechanism where one operation of the thread can logically help other threads linearize their operations; (2) combining relational specifications and rely/guarantee conditions for relational and compositional reasoning. We have successfully applied CRL-H to verify the linearizability of AtomFS directly in C code. All the proofs are mechanized in Coq. Evaluations show that AtomFS speeds up file system workloads by utilizing fine-grained, multicore concurrency.","PeriodicalId":331561,"journal":{"name":"Proceedings of the 27th ACM Symposium on Operating Systems Principles","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2019-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"25","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Proceedings of the 27th ACM Symposium on Operating Systems Principles","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1145/3341301.3359644","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 25
Abstract
Concurrent file systems are pervasive but hard to correctly implement and formally verify due to nondeterministic interleavings. This paper presents AtomFS, the first formally-verified, fine-grained, concurrent file system, which provides linearizable interfaces to applications. The standard way to prove linearizability requires modeling linearization point of each operation---the moment when its effect becomes visible atomically to other threads. We observe that path inter-dependency, where one operation (like rename) breaks the path integrity of other operations, makes the linearization point external and thus poses a significant challenge to prove linearizability. To overcome the above challenge, this paper presents Concurrent Relational Logic with Helpers (CRL-H), a framework for building verified concurrent file systems. CRL-H is made powerful through two key contributions: (1) extending prior approaches using fixed linearization points with a helper mechanism where one operation of the thread can logically help other threads linearize their operations; (2) combining relational specifications and rely/guarantee conditions for relational and compositional reasoning. We have successfully applied CRL-H to verify the linearizability of AtomFS directly in C code. All the proofs are mechanized in Coq. Evaluations show that AtomFS speeds up file system workloads by utilizing fine-grained, multicore concurrency.