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lvm2/tools/vgscan.c

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/*
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* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2009 Red Hat, Inc. All rights reserved.
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*
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* This file is part of LVM2.
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*
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* 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.
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*
* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
#include "tools.h"
static int _vgscan_single(struct cmd_context *cmd, const char *vg_name,
struct volume_group *vg,
struct processing_handle *handle __attribute__((unused)))
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{
log_print_unless_silent("Found %svolume group \"%s\" using metadata type %s",
vg_is_exported(vg) ? "exported " : "", vg_name,
vg->fid->fmt->name);
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check_current_backup(vg);
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return ECMD_PROCESSED;
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}
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int vgscan(struct cmd_context *cmd, int argc, char **argv)
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{
int maxret, ret;
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if (arg_is_set(cmd, notifydbus_ARG)) {
if (!lvmnotify_is_supported()) {
log_error("Cannot notify dbus: lvm is not built with dbus support.");
return ECMD_FAILED;
}
if (!find_config_tree_bool(cmd, global_notify_dbus_CFG, NULL)) {
log_error("Cannot notify dbus: notify_dbus is disabled in lvm config.");
return ECMD_FAILED;
}
set_pv_notify(cmd);
set_vg_notify(cmd);
set_lv_notify(cmd);
return ECMD_PROCESSED;
}
if (!lock_vol(cmd, VG_GLOBAL, LCK_VG_WRITE, NULL)) {
log_error("Unable to obtain global lock.");
return ECMD_FAILED;
}
if (arg_is_set(cmd, cache_long_ARG)) {
log_warn("Ignoring vgscan --cache command because lvmetad is no longer used.");
return ECMD_PROCESSED;
}
maxret = process_each_vg(cmd, argc, argv, NULL, NULL, 0, 0, NULL, &_vgscan_single);
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if (arg_is_set(cmd, mknodes_ARG)) {
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ret = vgmknodes(cmd, argc, argv);
if (ret > maxret)
maxret = ret;
}
lvmetad: two phase vg_update Previously, a command sent lvmetad new VG metadata in vg_commit(). In vg_commit(), devices are suspended, so any memory allocation done by the command while sending to lvmetad, or by lvmetad while updating its cache could deadlock if memory reclaim was triggered. Now lvmetad is updated in unlock_vg(), after devices are resumed. The new method for updating VG metadata in lvmetad is in two phases: 1. In vg_write(), before devices are suspended, the command sends lvmetad a short message ("set_vg_info") telling it what the new VG seqno will be. lvmetad sees that the seqno is newer than the seqno of its cached VG, so it sets the INVALID flag for the cached VG. If sending the message to lvmetad fails, the command fails before the metadata is committed and the change is not made. If sending the message succeeds, vg_commit() is called. 2. In unlock_vg(), after devices are resumed, the command sends lvmetad the standard vg_update message with the new metadata. lvmetad sees that the seqno in the new metadata matches the seqno it saved from set_vg_info, and knows it has the latest copy, so it clears the INVALID flag for the cached VG. If a command fails between 1 and 2 (after committing the VG on disk, but before sending lvmetad the new metadata), the cached VG retains the INVALID flag in lvmetad. A subsequent command will read the cached VG from lvmetad, see the INVALID flag, ignore the cached copy, read the VG from disk instead, update the lvmetad copy with the latest copy from disk, (this clears the INVALID flag in lvmetad), and use the correct VG metadata for the command. (This INVALID mechanism already existed for use by lvmlockd.)
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unlock_vg(cmd, NULL, VG_GLOBAL);
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return maxret;
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}