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The LVM devices file lists devices that lvm can use. The default
file is /etc/lvm/devices/system.devices, and the lvmdevices(8)
command is used to add or remove device entries. If the file
does not exist, or if lvm.conf includes use_devicesfile=0, then
lvm will not use a devices file. When the devices file is in use,
the regex filter is not used, and the filter settings in lvm.conf
or on the command line are ignored.
LVM records devices in the devices file using hardware-specific
IDs, such as the WWID, and attempts to use subsystem-specific
IDs for virtual device types. These device IDs are also written
in the VG metadata. When no hardware or virtual ID is available,
lvm falls back using the unstable device name as the device ID.
When devnames are used, lvm performs extra scanning to find
devices if their devname changes, e.g. after reboot.
When proper device IDs are used, an lvm command will not look
at devices outside the devices file, but when devnames are used
as a fallback, lvm will scan devices outside the devices file
to locate PVs on renamed devices. A config setting
search_for_devnames can be used to control the scanning for
renamed devname entries.
Related to the devices file, the new command option
--devices <devnames> allows a list of devices to be specified for
the command to use, overriding the devices file. The listed
devices act as a sort of devices file in terms of limiting which
devices lvm will see and use. Devices that are not listed will
appear to be missing to the lvm command.
Multiple devices files can be kept in /etc/lvm/devices, which
allows lvm to be used with different sets of devices, e.g.
system devices do not need to be exposed to a specific application,
and the application can use lvm on its own set of devices that are
not exposed to the system. The option --devicesfile <filename> is
used to select the devices file to use with the command. Without
the option set, the default system devices file is used.
Setting --devicesfile "" causes lvm to not use a devices file.
An existing, empty devices file means lvm will see no devices.
The new command vgimportdevices adds PVs from a VG to the devices
file and updates the VG metadata to include the device IDs.
vgimportdevices -a will import all VGs into the system devices file.
LVM commands run by dmeventd not use a devices file by default,
and will look at all devices on the system. A devices file can
be created for dmeventd (/etc/lvm/devices/dmeventd.devices) If
this file exists, lvm commands run by dmeventd will use it.
Internal implementaion:
- device_ids_read - read the devices file
. add struct dev_use (du) to cmd->use_devices for each devices file entry
- dev_cache_scan - get /dev entries
. add struct device (dev) to dev_cache for each device on the system
- device_ids_match - match devices file entries to /dev entries
. match each du on cmd->use_devices to a dev in dev_cache, using device ID
. on match, set du->dev, dev->id, dev->flags MATCHED_USE_ID
- label_scan - read lvm headers and metadata from devices
. filters are applied, those that do not need data from the device
. filter-deviceid skips devs without MATCHED_USE_ID, i.e.
skips /dev entries that are not listed in the devices file
. read lvm label from dev
. filters are applied, those that use data from the device
. read lvm metadata from dev
. add info/vginfo structs for PVs/VGs (info is "lvmcache")
- device_ids_find_renamed_devs - handle devices with unstable devname ID
where devname changed
. this step only needed when devs do not have proper device IDs,
and their dev names change, e.g. after reboot sdb becomes sdc.
. detect incorrect match because PVID in the devices file entry
does not match the PVID found when the device was read above
. undo incorrect match between du and dev above
. search system devices for new location of PVID
. update devices file with new devnames for PVIDs on renamed devices
. label_scan the renamed devs
- continue with command processing
84 lines
2.6 KiB
C
84 lines
2.6 KiB
C
/*
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* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
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* Copyright (C) 2004-2007 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,
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* modify, copy, or redistribute it subject to the terms and conditions
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* of the GNU Lesser General Public License v.2.1.
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*
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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,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _LVM_DEV_CACHE_H
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#define _LVM_DEV_CACHE_H
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#include "lib/device/device.h"
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#include "lib/device/dev-type.h"
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#include "lib/misc/lvm-wrappers.h"
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struct cmd_context;
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/*
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* predicate for devices.
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*/
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struct dev_filter {
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int (*passes_filter) (struct cmd_context *cmd, struct dev_filter *f, struct device *dev, const char *use_filter_name);
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void (*destroy) (struct dev_filter *f);
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void (*wipe) (struct cmd_context *cmd, struct dev_filter *f, struct device *dev, const char *use_filter_name);
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void *private;
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unsigned use_count;
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const char *name;
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};
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struct dm_list *dev_cache_get_dev_list_for_vgid(const char *vgid);
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struct dm_list *dev_cache_get_dev_list_for_lvid(const char *lvid);
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/*
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* The global device cache.
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*/
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int dev_cache_init(struct cmd_context *cmd);
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int dev_cache_exit(void);
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/*
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* Returns number of open devices.
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*/
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int dev_cache_check_for_open_devices(void);
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void dev_cache_scan(void);
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int dev_cache_has_scanned(void);
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int dev_cache_add_dir(const char *path);
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struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct dev_filter *f);
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struct device *dev_cache_get_by_devt(struct cmd_context *cmd, dev_t device, struct dev_filter *f, int *filtered);
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struct device *dev_hash_get(const char *name);
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void dev_set_preferred_name(struct dm_str_list *sl, struct device *dev);
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/*
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* Object for iterating through the cache.
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*/
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struct dev_iter;
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struct dev_iter *dev_iter_create(struct dev_filter *f, int unused);
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void dev_iter_destroy(struct dev_iter *iter);
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struct device *dev_iter_get(struct cmd_context *cmd, struct dev_iter *iter);
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void dev_reset_error_count(struct cmd_context *cmd);
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void dev_cache_failed_path(struct device *dev, const char *path);
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bool dev_cache_has_md_with_end_superblock(struct dev_types *dt);
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int get_sysfs_value(const char *path, char *buf, size_t buf_size, int error_if_no_value);
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int setup_devices_file(struct cmd_context *cmd);
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int setup_devices(struct cmd_context *cmd);
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int setup_device(struct cmd_context *cmd, const char *devname);
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#endif
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