License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.ECOOP.2018.4
URN: urn:nbn:de:0030-drops-92092
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2018/9209/
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Ntzik, Gian ; da Rocha Pinto, Pedro ; Sutherland, Julian ; Gardner, Philippa

A Concurrent Specification of POSIX File Systems

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Abstract

POSIX is a standard for operating systems, with a substantial part devoted to specifying file-system operations. File-system operations exhibit complex concurrent behaviour, comprising multiple actions affecting different parts of the state: typically, multiple atomic reads followed by an atomic update. However, the standard's description of concurrent behaviour is unsatisfactory: it is fragmented; contains ambiguities; and is generally under-specified. We provide a formal concurrent specification of POSIX file systems and demonstrate scalable reasoning for clients. Our specification is based on a concurrent specification language, which uses a modern concurrent separation logic for reasoning about abstract atomic operations, and an associated refinement calculus. Our reasoning about clients highlights an important difference between reasoning about modules built over a heap, where the interference on the shared state is restricted to the operations of the module, and modules built over a file system, where the interference cannot be restricted as the file system is a public namespace. We introduce specifications conditional on context invariants used to restrict the interference, and apply our reasoning to the example of lock files.

BibTeX - Entry

@InProceedings{ntzik_et_al:LIPIcs:2018:9209,
  author =	{Gian Ntzik and Pedro da Rocha Pinto and Julian Sutherland and Philippa Gardner},
  title =	{{A Concurrent Specification of POSIX File Systems}},
  booktitle =	{32nd European Conference on Object-Oriented Programming  (ECOOP 2018)},
  pages =	{4:1--4:28},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-079-8},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{109},
  editor =	{Todd Millstein},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{http://drops.dagstuhl.de/opus/volltexte/2018/9209},
  URN =		{urn:nbn:de:0030-drops-92092},
  doi =		{10.4230/LIPIcs.ECOOP.2018.4},
  annote =	{Keywords: POSIX, concurrency, file systems, refinement, separation logic, atomicity}
}

Keywords: POSIX, concurrency, file systems, refinement, separation logic, atomicity
Collection: 32nd European Conference on Object-Oriented Programming (ECOOP 2018)
Issue Date: 2018
Date of publication: 10.07.2018

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