0f0869bca3
Without this patch, mountd would delete/load all exports from the exports file(s) when it receives a SIGHUP. This works fine for small exports file(s), but can take several seconds to do when there are large numbers (10000+) of exported file systems. Most of this time is spent doing the system calls that delete/export each of these file systems. When the "-S" option has been specified (the default these days), the nfsd threads are suspended for several seconds while the reload is done. This patch changes mountd so that it only does system calls for file systems where the exports have been changed/added/deleted as compared to the exports done for the previous load/reload of the exports file(s). Basically, when SIGHUP is posted to mountd, it saves the exportlist structures from the previous load and creates a new set of structures from the current exports file(s). Then it compares the current with the previous and only does system calls for cases that have been changed/added/deleted. The nfsd threads do not need to be suspended until the comparison step is being done. This results in a suspension period of milliseconds for a server with 10000+ exported file systems. There is some code using a LOGDEBUG() macro that allow runtime debugging output via syslog(LOG_DEBUG,...) that can be enabled by creating a file called /var/log/mountd.debug. This code is expected to be replaced with code that uses dtrace by cy@ in the near future, once issues w.r.t. dtrace in stable/12 have been resolved. The patch should not change the usage of the exports file(s), but improves the performance of reloading large exports file(s) where there are only a small number of changes done to the file(s). Tested by: pen@lysator.liu.se PR: 237860 Reviewed by: kib MFC after: 1 month Relnotes: yes Differential Revision: https://reviews.freebsd.org/D20487
40 lines
1.9 KiB
C
40 lines
1.9 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)pathnames.h 8.1 (Berkeley) 6/5/93
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* $FreeBSD$
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*/
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#include <paths.h>
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#define _PATH_EXPORTS "/etc/exports"
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#define _PATH_RMOUNTLIST "/var/db/mountdtab"
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#define _PATH_MOUNTDPID "/var/run/mountd.pid"
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#define _PATH_MOUNTDDEBUG "/var/log/mountd.debug"
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