From owner-freebsd-hackers@freebsd.org Sun Jul 12 19:55:58 2020 Return-Path: Delivered-To: freebsd-hackers@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id EFD6636CAB7 for ; Sun, 12 Jul 2020 19:55:58 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from hz.grosbein.net (hz.grosbein.net [IPv6:2a01:4f8:c2c:26d8::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "hz.grosbein.net", Issuer "hz.grosbein.net" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4B4cwG11qWz3y1H for ; Sun, 12 Jul 2020 19:55:57 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from eg.sd.rdtc.ru (eg.sd.rdtc.ru [IPv6:2a03:3100:c:13:0:0:0:5]) by hz.grosbein.net (8.15.2/8.15.2) with ESMTPS id 06CJtp42048131 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 12 Jul 2020 19:55:53 GMT (envelope-from eugen@grosbein.net) X-Envelope-From: eugen@grosbein.net X-Envelope-To: kostikbel@gmail.com Received: from [10.58.0.10] (dadvw [10.58.0.10]) by eg.sd.rdtc.ru (8.15.2/8.15.2) with ESMTPS id 06CJtioR036077 (version=TLSv1.2 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Mon, 13 Jul 2020 02:55:45 +0700 (+07) (envelope-from eugen@grosbein.net) Subject: Re: fsync(2) To: Konstantin Belousov References: <0cdc3315-0213-8522-c8d6-695c2ee02923@grosbein.net> <20200712190517.GA44314@kib.kiev.ua> Cc: Freebsd hackers list From: Eugene Grosbein Message-ID: <12fb648f-8c37-be9b-f18a-5dc2ec9a09c9@grosbein.net> Date: Mon, 13 Jul 2020 02:55:32 +0700 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20200712190517.GA44314@kib.kiev.ua> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=0.3 required=5.0 tests=BAYES_00,LOCAL_FROM, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.2 X-Spam-Report: * -2.3 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record * -0.0 SPF_PASS SPF: sender matches SPF record * 2.6 LOCAL_FROM From my domains * 0.0 NICE_REPLY_A Looks like a legit reply (A) X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on hz.grosbein.net X-Rspamd-Queue-Id: 4B4cwG11qWz3y1H X-Spamd-Bar: / Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=permerror (mx1.freebsd.org: domain of eugen@grosbein.net uses mechanism not recognized by this client) smtp.mailfrom=eugen@grosbein.net X-Spamd-Result: default: False [0.31 / 15.00]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; NEURAL_SPAM_SHORT(0.12)[0.120]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[grosbein.net]; NEURAL_SPAM_MEDIUM(0.17)[0.171]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; TO_DN_ALL(0.00)[]; R_SPF_PERMFAIL(0.00)[empty SPF record]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_SPAM_LONG(0.12)[0.121]; FREEMAIL_TO(0.00)[gmail.com]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:2a01:4f8::/29, country:DE]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.33 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 12 Jul 2020 19:55:59 -0000 13.07.2020 2:05, Konstantin Belousov wrote: > On Mon, Jul 13, 2020 at 01:49:22AM +0700, Eugene Grosbein wrote: >> Hi! >> >> Assume we have parent process that created a file and keeps it open not writing anything there. >> The parent spawns a child passing file name and the child opens it, >> fills it with data and exits without fsync()'ing the file. >> >> In case of UFS there is upto 30 seconds time gap when file size is not updated, >> so if crash occurs, the file ends up empty. >> >> The question: will fsync() in parent work for such still open file descriptor? > > fsync() syncs the vnode, not the file or file descriptor. So fsync() on > any file descriptor referencing the same vnode, is enough to ensure that > the data is written to the underlying volume. Thanks! This seems to be undocumented. https://pubs.opengroup.org/onlinepubs/009695399/functions/fsync.html does not mention implementation details (and could not) but our manual page could be improved, could it?