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arrangement that has no intrinsic internal knowledge of whether devices it is given are truly multipath devices. As such, this is a simplistic approach, but still a useful one. The basic approach is to (at present- this will change soon) use camcontrol to find likely identical devices and and label the trailing sector of the first one. This label contains both a full UUID and a name. The name is what is presented in /dev/multipath, but the UUID is used as a true distinguishor at g_taste time, thus making sure we don't have chaos on a shared SAN where everyone names their data multipath as "Fred". The first of N identical devices (and N *may* be 1!) becomes the active path until a BIO request is failed with EIO or ENXIO. When this occurs, the active disk is ripped away and the next in a list is picked to (retry and) continue with. During g_taste events new disks that meet the match criteria for existing multipath geoms get added to the tail end of the list. Thus, this active/passive setup actually does work for devices which go away and come back, as do (now) mpt(4) and isp(4) SAN based disks. There is still a lot to do to improve this- like about 5 of the 12 recommendations I've received about it, but it's been functional enough for a while that it deserves a broader test base. Reviewed by: pjd Sponsored by: IronPort Systems MFC: 2 months
100 lines
3.4 KiB
C
100 lines
3.4 KiB
C
/*-
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* Copyright (c) 2006-2007 Matthew Jacob <mjacob@FreeBSD.org>
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* 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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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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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/*
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* Based upon work by Pawel Jakub Dawidek <pjd@FreeBSD.org> for all of the
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* fine geom examples, and by Poul Henning Kamp <phk@FreeBSD.org> for GEOM
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* itself, all of which is most gratefully acknowledged.
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*/
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#ifndef _G_MULTIPATH_H_
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#define _G_MULTIPATH_H_
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#define G_MULTIPATH_CLASS_NAME "MULTIPATH"
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#define G_MULTIPATH_VERSION 1
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#define G_MULTIPATH_MAGIC "GEOM::MULTIPATH"
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#include <sys/endian.h>
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#ifdef _KERNEL
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struct g_multipath_softc {
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struct g_provider * pp;
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struct g_consumer * cp_active;
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char sc_name[16];
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char sc_uuid[40];
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};
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#endif /* _KERNEL */
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struct g_multipath_metadata {
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char md_magic[16]; /* Magic Value */
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char md_uuid[40]; /* more magic */
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char md_name[16]; /* a friendly name */
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uint32_t md_version; /* version */
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uint32_t md_sectorsize; /* sectorsize of provider */
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uint64_t md_size; /* absolute size of provider */
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};
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static __inline void
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multipath_metadata_encode(const struct g_multipath_metadata *, u_char *);
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static __inline void
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multipath_metadata_decode(u_char *, struct g_multipath_metadata *);
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static __inline void
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multipath_metadata_encode(const struct g_multipath_metadata *md, u_char *data)
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{
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bcopy(md->md_magic, data, sizeof(md->md_magic));
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data += sizeof(md->md_magic);
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bcopy(md->md_uuid, data, sizeof(md->md_uuid));
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data += sizeof(md->md_uuid);
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bcopy(md->md_name, data, sizeof(md->md_name));
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data += sizeof(md->md_name);
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le32enc(data, md->md_version);
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data += sizeof(md->md_version);
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le32enc(data, md->md_sectorsize);
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data += sizeof(md->md_sectorsize);
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le64enc(data, md->md_size);
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}
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static __inline void
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multipath_metadata_decode(u_char *data, struct g_multipath_metadata *md)
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{
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bcopy(data, md->md_magic, sizeof(md->md_magic));
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data += sizeof(md->md_magic);
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bcopy(data, md->md_uuid, sizeof(md->md_uuid));
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data += sizeof(md->md_uuid);
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bcopy(data, md->md_name, sizeof(md->md_name));
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data += sizeof(md->md_name);
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md->md_version = le32dec(data);
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data += sizeof(md->md_version);
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md->md_sectorsize = le32dec(data);
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data += sizeof(md->md_sectorsize);
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md->md_size = le64dec(data);
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}
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#endif /* _G_MULTIPATH_H_ */
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