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lvm2/tools/vgcfgrestore.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.
*
* 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"
#include "daemons/lvmetad/lvmetad-client.h"
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int vgcfgrestore(struct cmd_context *cmd, int argc, char **argv)
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{
const char *vg_name = NULL;
int lvmetad_rescan = 0;
int ret;
if (argc == 1) {
vg_name = skip_dev_dir(cmd, argv[0], NULL);
if (!validate_name(vg_name)) {
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log_error("Volume group name \"%s\" is invalid.", vg_name);
return EINVALID_CMD_LINE;
}
} else if (!(arg_is_set(cmd, list_ARG) && arg_is_set(cmd, file_ARG))) {
log_error("Please specify a *single* volume group to restore.");
return EINVALID_CMD_LINE;
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}
/*
* FIXME: overloading the -l arg for now to display a
* list of archive files for a particular vg
*/
if (arg_is_set(cmd, list_ARG)) {
if (!(arg_is_set(cmd,file_ARG) ?
archive_display_file(cmd,
arg_str_value(cmd, file_ARG, "")) :
archive_display(cmd, vg_name)))
return_ECMD_FAILED;
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return ECMD_PROCESSED;
}
/*
* lvmetad does not handle a VG being restored, which would require
* vg_remove of the existing VG, then vg_update of the restored VG. A
* command failure after removing the existing VG from lvmetad would
* not be easily recovered from. So, disable the lvmetad cache before
* doing the restore. After the VG is restored on disk, rescan
* metadata from disk to populate lvmetad from scratch which will pick
* up the VG that was restored on disk.
*/
if (lvmetad_used()) {
lvmetad_set_disabled(cmd, LVMETAD_DISABLE_REASON_VGRESTORE);
lvmetad_disconnect();
lvmetad_rescan = 1;
}
if (!lock_vol(cmd, VG_ORPHANS, LCK_VG_WRITE, NULL)) {
log_error("Unable to lock orphans.");
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return ECMD_FAILED;
}
if (!lock_vol(cmd, vg_name, LCK_VG_WRITE, NULL)) {
log_error("Unable to lock volume group %s.", vg_name);
unlock_vg(cmd, NULL, VG_ORPHANS);
return ECMD_FAILED;
}
scan: do scanning at the start of a command Move the location of scans to make it clearer and avoid unnecessary repeated scanning. There should be one scan at the start of a command which is then used through the rest of command processing. Previously, the initial label scan was called as a side effect from various utility functions. This would lead to it being called unnecessarily. It is an expensive operation, and should only be called when necessary. Also, this is a primary step in the function of the command, and as such it should be called prominently at the top level of command processing, not as a hidden side effect of a utility function. lvm knows exactly where and when the label scan needs to be done. Because of this, move the label scan calls from the internal functions to the top level of processing. Other specific instances of lvmcache_label_scan() are still called unnecessarily or unclearly by specific commands that do not use the common process_each functions. These will be improved in future commits. During the processing phase, rescanning labels for devices in a VG needs to be done after the VG lock is acquired in case things have changed since the initial label scan. This was being done by way of rescanning devices that had the INVALID flag set in lvmcache. This usually approximated the right set of devices, but it was not exact, and obfuscated the real requirement. Correct this by using a new function that rescans the devices in the VG: lvmcache_label_rescan_vg(). Apart from being inexact, the rescanning was extremely well hidden. _vg_read() would call ->create_instance(), _text_create_text_instance(), _create_vg_text_instance() which would call lvmcache_label_scan() which would call _scan_invalid() which repeats the label scan on devices flagged INVALID. lvmcache_label_rescan_vg() is now called prominently by _vg_read() directly.
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lvmcache_label_scan(cmd);
cmd->handles_unknown_segments = 1;
if (!(arg_is_set(cmd, file_ARG) ?
backup_restore_from_file(cmd, vg_name,
arg_str_value(cmd, file_ARG, ""),
arg_count(cmd, force_long_ARG)) :
backup_restore(cmd, vg_name, arg_count(cmd, force_long_ARG)))) {
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_name);
unlock_vg(cmd, NULL, VG_ORPHANS);
log_error("Restore failed.");
ret = ECMD_FAILED;
goto rescan;
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}
ret = ECMD_PROCESSED;
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log_print_unless_silent("Restored volume group %s.", vg_name);
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_ORPHANS);
unlock_vg(cmd, NULL, vg_name);
rescan:
if (lvmetad_rescan) {
if (!lvmetad_connect(cmd)) {
log_warn("WARNING: Failed to connect to lvmetad.");
log_warn("WARNING: Update lvmetad with pvscan --cache.");
goto out;
}
if (!refresh_filters(cmd))
stack;
if (!lvmetad_pvscan_all_devs(cmd, 1)) {
log_warn("WARNING: Failed to scan devices.");
log_warn("WARNING: Update lvmetad with pvscan --cache.");
goto out;
}
}
out:
return ret;
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}