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lvm2/lib/device/dev-cache.h

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/*
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* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
*
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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
*/
#ifndef _LVM_DEV_CACHE_H
#define _LVM_DEV_CACHE_H
#include "lib/device/device.h"
#include "lib/device/dev-type.h"
#include "lib/misc/lvm-wrappers.h"
struct cmd_context;
/*
* predicate for devices.
*/
struct dev_filter {
int (*passes_filter) (struct cmd_context *cmd, struct dev_filter *f, struct device *dev, const char *use_filter_name);
void (*destroy) (struct dev_filter *f);
void (*wipe) (struct cmd_context *cmd, struct dev_filter *f, struct device *dev, const char *use_filter_name);
void *private;
unsigned use_count;
const char *name;
};
dev: detect mismatch between devices used and devices assumed for an LV It's possible for an LVM LV to use a device during activation which then differs from device which LVM assumes based on metadata later on. For example, such device mismatch can occur if LVM doesn't have complete view of devices during activation or if filters are misbehaving or they're incorrectly set during activation. This patch adds code that can detect this mismatch by creating VG UUID and LV UUID index while scanning devices for device cache. The VG UUID index maps VG UUID to a device list. Each device in the list has a device layered above as a holder which is an LVM LV device and for which we know the VG UUID (and similarly for LV UUID index). We can acquire VG and LV UUID by reading /sys/block/<dm_dev_name>/dm/uuid. So these indices represent the actual state of PV device use in the system by LVs and then we compare that to what LVM assumes based on metadata. For example: [0] fedora/~ # lsblk /dev/sdq /dev/sdr /dev/sds /dev/sdt NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sdq 65:0 0 104M 0 disk |-vg-lvol0 253:2 0 200M 0 lvm `-mpath_dev1 253:3 0 104M 0 mpath sdr 65:16 0 104M 0 disk `-mpath_dev1 253:3 0 104M 0 mpath sds 65:32 0 104M 0 disk |-vg-lvol0 253:2 0 200M 0 lvm `-mpath_dev2 253:4 0 104M 0 mpath sdt 65:48 0 104M 0 disk `-mpath_dev2 253:4 0 104M 0 mpath In this case the vg-lvol0 is mapped onto sdq and sds becauset this is what was available and seen during activation. Then later on, sdr and sdt appeared and mpath devices were created out of sdq+sdr (mpath_dev1) and sds+sdt (mpath_dev2). Now, LVM assumes (correctly) that mpath_dev1 and mpath_dev2 are the PVs that should be used, not the mpath components (sdq/sdr, sds/sdt). [0] fedora/~ # pvs Found duplicate PV xSUix1GJ2SK82ACFuKzFLAQi8xMfFxnO: using /dev/mapper/mpath_dev1 not /dev/sdq Using duplicate PV /dev/mapper/mpath_dev1 from subsystem DM, replacing /dev/sdq Found duplicate PV MvHyMVabtSqr33AbkUrobq1LjP8oiTRm: using /dev/mapper/mpath_dev2 not /dev/sds Using duplicate PV /dev/mapper/mpath_dev2 from subsystem DM, ignoring /dev/sds WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/sdq, /dev/sds instead of /dev/mapper/mpath_dev1, /dev/mapper/mpath_dev2. PV VG Fmt Attr PSize PFree /dev/mapper/mpath_dev1 vg lvm2 a-- 100.00m 0 /dev/mapper/mpath_dev2 vg lvm2 a-- 100.00m 0
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struct dm_list *dev_cache_get_dev_list_for_vgid(const char *vgid);
struct dm_list *dev_cache_get_dev_list_for_lvid(const char *lvid);
/*
* The global device cache.
*/
int dev_cache_init(struct cmd_context *cmd);
int dev_cache_exit(void);
/*
* Returns number of open devices.
*/
int dev_cache_check_for_open_devices(void);
void dev_cache_scan(struct cmd_context *cmd);
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int dev_cache_has_scanned(void);
int dev_cache_add_dir(const char *path);
struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct dev_filter *f);
struct device *dev_cache_get_existing(struct cmd_context *cmd, const char *name, struct dev_filter *f);
struct device *dev_cache_get_by_devt(struct cmd_context *cmd, dev_t devt);
struct device *dev_cache_get_by_pvid(struct cmd_context *cmd, const char *pvid);
void dev_cache_verify_aliases(struct device *dev);
struct device *dev_hash_get(const char *name);
void dev_set_preferred_name(struct dm_str_list *sl, struct device *dev);
/*
* Object for iterating through the cache.
*/
struct dev_iter;
struct dev_iter *dev_iter_create(struct dev_filter *f, int unused);
void dev_iter_destroy(struct dev_iter *iter);
struct device *dev_iter_get(struct cmd_context *cmd, struct dev_iter *iter);
void dev_cache_failed_path(struct device *dev, const char *path);
bool dev_cache_has_md_with_end_superblock(struct dev_types *dt);
device usage based on devices file 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
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int get_sysfs_value(const char *path, char *buf, size_t buf_size, int error_if_no_value);
int get_sysfs_binary(const char *path, char *buf, size_t buf_size, int *retlen);
device usage based on devices file 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
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int setup_devices_file(struct cmd_context *cmd);
int setup_devices(struct cmd_context *cmd);
int setup_device(struct cmd_context *cmd, const char *devname);
int setup_devices_for_online_autoactivation(struct cmd_context *cmd);
int setup_devname_in_dev_cache(struct cmd_context *cmd, const char *devname);
int setup_devno_in_dev_cache(struct cmd_context *cmd, dev_t devno);
struct device *setup_dev_in_dev_cache(struct cmd_context *cmd, dev_t devno, const char *devname);
#endif