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7f16b501e2
Traditionally the GEOM's primary channel of information from kernel to user-space was confxml, fetched by libgeom through kern.geom.confxml sysctl. It is convenient and informative, representing full state of GEOM in a single XML document. But problems start to arise on systems with hundreds of disks, where the full confxml size reaches many megabytes, taking significant time to first write it and then parse. This patch introduces alternative solution, allowing to fetch much smaller XML document, subset of the full confxml, limited to 64KB and representing only one specified geom and optionally its parents. It uses existing GEOM control interface, extended with new "getxml" verb. In case of any error, such as the buffer overflow, it just transparently falls back to traditional full confxml. This patch uses the new API in user-space GEOM tools where it is possible. Reviewed by: imp MFC after: 2 month Sponsored by: iXsystems, Inc. Differential Revision: https://reviews.freebsd.org/D34529
131 lines
3.6 KiB
C
131 lines
3.6 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause-FreeBSD
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*
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* Copyright (c) 2003 Poul-Henning Kamp
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* All rights reserved.
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* Copyright (c) 2022 Alexander Motin <mav@FreeBSD.org>
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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. The names of the authors may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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* $FreeBSD$
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*/
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#include <sys/types.h>
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#include <sys/sysctl.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include "libgeom.h"
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/*
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* Amount of extra space we allocate to try and anticipate the size of
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* confxml.
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*/
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#define GEOM_GETXML_SLACK 4096
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/*
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* Number of times to retry in the face of the size of confxml exceeding
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* that of our buffer.
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*/
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#define GEOM_GETXML_RETRIES 4
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/*
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* Size of confxml buffer to request via getxml control request. It is
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* expected to be sufficient for single geom and its parents. In case of
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* overflow fall back to requesting full confxml via sysctl interface.
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*/
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#define GEOM_GETXML_BUFFER 65536
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char *
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geom_getxml(void)
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{
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char *p;
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size_t l = 0;
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int mib[3];
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size_t sizep;
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int retries;
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sizep = sizeof(mib) / sizeof(*mib);
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if (sysctlnametomib("kern.geom.confxml", mib, &sizep) != 0)
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return (NULL);
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if (sysctl(mib, sizep, NULL, &l, NULL, 0) != 0)
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return (NULL);
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l += GEOM_GETXML_SLACK;
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for (retries = 0; retries < GEOM_GETXML_RETRIES; retries++) {
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p = malloc(l);
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if (p == NULL)
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return (NULL);
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if (sysctl(mib, sizep, p, &l, NULL, 0) == 0)
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return (reallocf(p, strlen(p) + 1));
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free(p);
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if (errno != ENOMEM)
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return (NULL);
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/*
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* Our buffer wasn't big enough. Make it bigger and
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* try again.
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*/
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l *= 2;
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}
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return (NULL);
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}
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char *
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geom_getxml_geom(const char *class, const char *geom, int parents)
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{
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struct gctl_req *r;
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char *p;
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const char *errstr;
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int nargs = 0;
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p = malloc(GEOM_GETXML_BUFFER);
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if (p == NULL)
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return (NULL);
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r = gctl_get_handle();
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gctl_ro_param(r, "class", -1, class);
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gctl_ro_param(r, "verb", -1, "getxml");
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gctl_ro_param(r, "parents", sizeof(parents), &parents);
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if (geom) {
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gctl_ro_param(r, "arg0", -1, geom);
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nargs = 1;
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}
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gctl_ro_param(r, "nargs", sizeof(nargs), &nargs);
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p[0] = '\0';
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gctl_add_param(r, "output", GEOM_GETXML_BUFFER, p,
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GCTL_PARAM_WR | GCTL_PARAM_ASCII);
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errstr = gctl_issue(r);
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if (errstr != NULL && errstr[0] != '\0') {
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gctl_free(r);
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free(p);
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return (geom_getxml());
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}
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gctl_free(r);
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return (p);
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}
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