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lvm2/tools/commands.h
David Teigland d9a77e8bb4 lvmcache: simplify metadata cache 
The copy of VG metadata stored in lvmcache was not being used
in general.  It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation.  There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.

This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.

This is a way of passing the VG from suspend to resume in
clvmd.  Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.)  The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo.  These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd.  The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.

suspend has both old (current) and new (precommitted)
copies of the VG metadata.  It stashes both of these in
the vginfo prior to suspending devices.  When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.

resume grabs the VG stashed by suspend.  If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG.  The VG is then used to resume
LVs.

This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.

Sequence of operations:

- lv_suspend() has both vg_old and vg_new
  and stashes a copy of each onto the vginfo:
  lvmcache_save_suspended_vg(vg_old);
  lvmcache_save_suspended_vg(vg_new);

- vg_commit() happens, which causes all clvmd
  instances to call lvmcache_commit_metadata(vg).
  A flag is set in the vginfo indicating the
  transition from the old to new VG:
  vginfo->suspended_vg_committed = 1;

- lv_resume() needs either vg_old or vg_new
  to use in resuming LVs.  It doesn't want to
  read the VG from disk since devices are
  suspended, so it gets the VG stashed by
  lv_suspend:
  vg = lvmcache_get_suspended_vg(vgid);

If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
2018-04-20 11:22:45 -05:00

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/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2014 Red Hat, Inc. All rights reserved.
*
* This file is part of LVM2.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU Lesser General Public License v.2.1.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
xx(config,
"Display and manipulate configuration information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(devtypes,
"Display recognised built-in block device types",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(dumpconfig,
"Display and manipulate configuration information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(formats,
"List available metadata formats",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(help,
"Display help for commands",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(fullreport,
"Display full report",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(lastlog,
"Display last command's log report",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(lvchange,
"Change the attributes of logical volume(s)",
PERMITTED_READ_ONLY)
xx(lvconvert,
"Change logical volume layout",
GET_VGNAME_FROM_OPTIONS)
xx(lvcreate,
"Create a logical volume",
0)
xx(lvdisplay,
"Display information about a logical volume",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(lvextend,
"Add space to a logical volume",
0)
xx(lvmchange,
"With the device mapper, this is obsolete and does nothing.",
0)
xx(lvmconfig,
"Display and manipulate configuration information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(lvmdiskscan,
"List devices that may be used as physical volumes",
PERMITTED_READ_ONLY | ENABLE_ALL_DEVS)
xx(lvmsadc,
"Collect activity data",
0)
xx(lvmsar,
"Create activity report",
0)
xx(lvreduce,
"Reduce the size of a logical volume",
0)
xx(lvremove,
"Remove logical volume(s) from the system",
ALL_VGS_IS_DEFAULT) /* all VGs only with --select */
xx(lvrename,
"Rename a logical volume",
0)
xx(lvresize,
"Resize a logical volume",
0)
xx(lvs,
"Display information about logical volumes",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(lvscan,
"List all logical volumes in all volume groups",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | NO_LVMETAD_AUTOSCAN)
xx(pvchange,
"Change attributes of physical volume(s)",
0)
xx(pvresize,
"Resize physical volume(s)",
0)
xx(pvck,
"Check the consistency of physical volume(s)",
LOCKD_VG_SH)
xx(pvcreate,
"Initialize physical volume(s) for use by LVM",
ENABLE_ALL_DEVS)
xx(pvdata,
"Display the on-disk metadata for physical volume(s)",
0)
xx(pvdisplay,
"Display various attributes of physical volume(s)",
PERMITTED_READ_ONLY | ENABLE_ALL_DEVS | ENABLE_DUPLICATE_DEVS | LOCKD_VG_SH)
/* ALL_VGS_IS_DEFAULT is for polldaemon to find pvmoves in-progress using process_each_vg. */
xx(pvmove,
"Move extents from one physical volume to another",
ALL_VGS_IS_DEFAULT | DISALLOW_TAG_ARGS)
xx(lvpoll,
"Continue already initiated poll operation on a logical volume",
0)
xx(pvremove,
"Remove LVM label(s) from physical volume(s)",
ENABLE_ALL_DEVS)
xx(pvs,
"Display information about physical volumes",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | ENABLE_ALL_DEVS | ENABLE_DUPLICATE_DEVS | LOCKD_VG_SH)
xx(pvscan,
"List all physical volumes",
PERMITTED_READ_ONLY | LOCKD_VG_SH | NO_LVMETAD_AUTOSCAN | IGNORE_PERSISTENT_FILTER)
xx(segtypes,
"List available segment types",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(systemid,
"Display the system ID, if any, currently set on this host",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(tags,
"List tags defined on this host",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
xx(vgcfgbackup,
"Backup volume group configuration(s)",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(vgcfgrestore,
"Restore volume group configuration",
0)
xx(vgchange,
"Change volume group attributes",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT)
xx(vgck,
"Check the consistency of volume group(s)",
ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(vgconvert,
"Change volume group metadata format",
0)
xx(vgcreate,
"Create a volume group",
MUST_USE_ALL_ARGS | ENABLE_ALL_DEVS)
xx(vgdisplay,
"Display volume group information",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(vgexport,
"Unregister volume group(s) from the system",
ALL_VGS_IS_DEFAULT)
xx(vgextend,
"Add physical volumes to a volume group",
MUST_USE_ALL_ARGS | ENABLE_ALL_DEVS)
xx(vgimport,
"Register exported volume group with system",
ALL_VGS_IS_DEFAULT | NO_LVMETAD_AUTOSCAN)
xx(vgimportclone,
"Import a VG from cloned PVs",
NO_LVMETAD_AUTOSCAN)
xx(vgmerge,
"Merge volume groups",
0)
xx(vgmknodes,
"Create the special files for volume group devices in /dev",
ALL_VGS_IS_DEFAULT)
xx(vgreduce,
"Remove physical volume(s) from a volume group",
0)
xx(vgremove,
"Remove volume group(s)",
ALL_VGS_IS_DEFAULT) /* all VGs only with select */
xx(vgrename,
"Rename a volume group",
ALLOW_UUID_AS_NAME | REQUIRES_FULL_LABEL_SCAN)
xx(vgs,
"Display information about volume groups",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH)
xx(vgscan,
"Search for all volume groups",
PERMITTED_READ_ONLY | ALL_VGS_IS_DEFAULT | LOCKD_VG_SH | NO_LVMETAD_AUTOSCAN | IGNORE_PERSISTENT_FILTER)
xx(vgsplit,
"Move physical volumes into a new or existing volume group",
0)
xx(version,
"Display software and driver version information",
PERMITTED_READ_ONLY | NO_METADATA_PROCESSING)
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