From owner-freebsd-hackers@freebsd.org Sun Jul 12 18:49:58 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 2ED4436B04F for ; Sun, 12 Jul 2020 18:49:58 +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 4B4bS50t0qz3cM7 for ; Sun, 12 Jul 2020 18:49:56 +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 06CIneWS047061 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sun, 12 Jul 2020 18:49:44 GMT (envelope-from eugen@grosbein.net) X-Envelope-From: eugen@grosbein.net X-Envelope-To: 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 06CInZoT035645 (version=TLSv1.2 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT) for ; Mon, 13 Jul 2020 01:49:35 +0700 (+07) (envelope-from eugen@grosbein.net) To: Freebsd hackers list From: Eugene Grosbein Subject: fsync(2) Message-ID: <0cdc3315-0213-8522-c8d6-695c2ee02923@grosbein.net> Date: Mon, 13 Jul 2020 01:49:22 +0700 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=0.3 required=5.0 tests=BAYES_00,LOCAL_FROM, 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 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on hz.grosbein.net X-Rspamd-Queue-Id: 4B4bS50t0qz3cM7 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 [1.50 / 15.00]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_SPAM_SHORT(0.90)[0.896]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[freebsd-hackers@freebsd.org]; DMARC_NA(0.00)[grosbein.net]; NEURAL_SPAM_MEDIUM(0.31)[0.310]; RCPT_COUNT_ONE(0.00)[1]; RCVD_COUNT_THREE(0.00)[3]; TO_DN_ALL(0.00)[]; R_SPF_PERMFAIL(0.00)[empty SPF record]; NEURAL_SPAM_LONG(0.39)[0.394]; 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 18:49:58 -0000 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?