From nobody Sat May 14 19:53:06 2022 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 8A26A1ADC60D for ; Sat, 14 May 2022 19:53:14 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4L0x5P6Lq7z4TKy for ; Sat, 14 May 2022 19:53:13 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.16.1/8.16.1) with ESMTPS id 24EJr7UP027208 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Sat, 14 May 2022 22:53:10 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 24EJr7UP027208 Received: (from kostik@localhost) by tom.home (8.16.1/8.16.1/Submit) id 24EJr6Af027207; Sat, 14 May 2022 22:53:06 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Sat, 14 May 2022 22:53:06 +0300 From: Konstantin Belousov To: Paul Floyd Cc: freebsd-hackers@freebsd.org Subject: Re: fcntl F_KINFO for Message-ID: References: <5e7863b6-4c57-16a2-0b54-655defefb347@gmail.com> List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e7863b6-4c57-16a2-0b54-655defefb347@gmail.com> X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.5 X-Spam-Checker-Version: SpamAssassin 3.4.5 (2021-03-20) on tom.home X-Rspamd-Queue-Id: 4L0x5P6Lq7z4TKy X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [-2.54 / 15.00]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.99)[-0.994]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_FROM(0.00)[gmail.com]; NEURAL_HAM_LONG(-1.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all]; TO_MATCH_ENVRCPT_SOME(0.00)[]; NEURAL_HAM_SHORT(-0.55)[-0.551]; RCPT_COUNT_TWO(0.00)[2]; MLMMJ_DEST(0.00)[freebsd-hackers]; 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:6939, ipnet:2001:470::/32, country:US]; RCVD_COUNT_TWO(0.00)[2]; FREEMAIL_ENVFROM(0.00)[gmail.com]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none] X-ThisMailContainsUnwantedMimeParts: N On Sat, May 14, 2022 at 09:45:26PM +0200, Paul Floyd wrote: > Hi > > I'm working on updating Valgrind for FreeBSD 13.1. > > I've been trying to rewrite some of the code (used in tracking file > descriptors, --track-fds=yes) to use fcntl and F_KINFO. The old code was IMO > ugly, using KERN_PROC_FILEDESC to get info on all open files and then do a > linear search for the fd. > > The new code is a lot shorter, but it doesn't quite work correctly. The > Valgrind regression test system redirects stdout and stderr, which it then > filters and compares to reference files. fcntl / F_KINFO doesn't seem to > work correctly with fd 1 (or at least, that seems to be the problem the most > often). > > Here is a small reproducer > > #include #include #include #include > #include #include #include > int main(void) { struct kinfo_file kf; kf.kf_structsize = KINFO_FILE_SIZE; > if (0 == fcntl( 1, F_KINFO, &kf )) { printf("fcntl succeeded %s\n", > kf.kf_path); } else { printf("fcntl failed\n"); } } > > Compiled with > > clang -g -o fcntl fcntl.c > > Then run it. > > For the first run > > $ ./fcntl > foo $ cat foo fcntl succeeded > > There's an empty string for kf_path there. > > Now that foo exists > > $ ./fcntl > foo $ cat foo fcntl succeeded /usr/home/paulf/foo > > Am I doing something wrong here or is this a bug / misfeature in the > implementation of gcntl / K_INFO? When open(2) creates a new file, the vnode name is not entered into the name cache. I believe this is done to smoother the case like untarring large set of files, which would replace existing cached entries with probably not too useful new entries. F_KINFO uses name cache to reconstruct the last element of the path, on most real file systems like UFS. If this last element is not cached, F_KINFO is unable to return the path.