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lvm2/lib/device/device.h
David Teigland 83fe6e720f 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
2021-02-23 16:43:32 -06:00

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/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004-2007 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
*/
#ifndef _LVM_DEVICE_H
#define _LVM_DEVICE_H
#include "lib/uuid/uuid.h"
#include <fcntl.h>
#define DEV_REGULAR 0x00000002 /* Regular file? */
#define DEV_ALLOCED 0x00000004 /* malloc used */
#define DEV_OPENED_RW 0x00000008 /* Opened RW */
#define DEV_OPENED_EXCL 0x00000010 /* Opened EXCL */
#define DEV_O_DIRECT 0x00000020 /* Use O_DIRECT */
#define DEV_O_DIRECT_TESTED 0x00000040 /* DEV_O_DIRECT is reliable */
#define DEV_OPEN_FAILURE 0x00000080 /* Has last open failed? */
#define DEV_USED_FOR_LV 0x00000100 /* Is device used for an LV */
#define DEV_ASSUMED_FOR_LV 0x00000200 /* Is device assumed for an LV */
#define DEV_NOT_O_NOATIME 0x00000400 /* Don't use O_NOATIME */
#define DEV_IN_BCACHE 0x00000800 /* dev fd is open and used in bcache */
#define DEV_BCACHE_EXCL 0x00001000 /* bcache_fd should be open EXCL */
#define DEV_FILTER_AFTER_SCAN 0x00002000 /* apply filter after bcache has data */
#define DEV_FILTER_OUT_SCAN 0x00004000 /* filtered out during label scan */
#define DEV_BCACHE_WRITE 0x00008000 /* bcache_fd is open with RDWR */
#define DEV_SCAN_FOUND_LABEL 0x00010000 /* label scan read dev and found label */
#define DEV_IS_MD_COMPONENT 0x00020000 /* device is an md component */
#define DEV_UDEV_INFO_MISSING 0x00040000 /* we have no udev info for this device */
#define DEV_IS_NVME 0x00080000 /* set if dev is nvme */
#define DEV_MATCHED_USE_ID 0x00100000 /* matched an entry from cmd->use_devices */
/*
* Support for external device info.
* Any new external device info source needs to be
* registered using EXT_REGISTER macro in dev-ext.c.
*/
typedef enum dev_ext_e {
DEV_EXT_NONE,
DEV_EXT_UDEV,
DEV_EXT_NUM
} dev_ext_t;
struct dev_ext {
int enabled;
dev_ext_t src;
void *handle;
};
#define DEV_ID_TYPE_SYS_WWID 0x0001
#define DEV_ID_TYPE_SYS_SERIAL 0x0002
#define DEV_ID_TYPE_MPATH_UUID 0x0003
#define DEV_ID_TYPE_MD_UUID 0x0004
#define DEV_ID_TYPE_LOOP_FILE 0x0005
#define DEV_ID_TYPE_CRYPT_UUID 0x0006
#define DEV_ID_TYPE_LVMLV_UUID 0x0007
#define DEV_ID_TYPE_DEVNAME 0x0008
/*
* A device ID of a certain type for a device.
* A struct device may have multiple dev_id structs on dev->ids.
* One of them will be the one that's used, pointed to by dev->id.
*/
struct dev_id {
struct dm_list list;
struct device *dev;
uint16_t idtype; /* DEV_ID_TYPE_ */
char *idname; /* id string determined by idtype */
};
/*
* A device listed in devices file that lvm should use.
* Each entry in the devices file is represented by a struct dev_use.
* The structs are kept on cmd->use_devices.
* idtype/idname/pvid/part are set when reading the devices file.
* du->dev is set when a struct dev_use is matched to a struct device.
*/
struct dev_use {
struct dm_list list;
struct device *dev;
int part;
uint16_t idtype;
char *idname;
char *devname;
char *pvid;
};
/*
* All devices in LVM will be represented by one of these.
* pointer comparisons are valid.
*/
struct device {
struct dm_list aliases; /* struct dm_str_list */
struct dm_list ids; /* struct dev_id, different entries for different idtypes */
struct dev_id *id; /* points to the the ids entry being used for this dev */
dev_t dev;
/* private */
int fd;
int open_count;
int physical_block_size; /* From BLKPBSZGET: lowest possible sector size that the hardware can operate on without reverting to read-modify-write operations */
int logical_block_size; /* From BLKSSZGET: lowest possible block size that the storage device can address */
int read_ahead;
int bcache_fd;
int bcache_di;
int part; /* partition number */
uint32_t flags;
uint32_t filtered_flags;
unsigned size_seqno;
uint64_t size;
uint64_t end;
struct dev_ext ext;
const char *duplicate_prefer_reason;
const char *vgid; /* if device is an LV */
const char *lvid; /* if device is an LV */
char pvid[ID_LEN + 1]; /* if device is a PV */
char _padding[7];
};
/*
* All I/O is annotated with the reason it is performed.
*/
typedef enum dev_io_reason {
DEV_IO_SIGNATURES = 0, /* Scanning device signatures */
DEV_IO_LABEL, /* LVM PV disk label */
DEV_IO_MDA_HEADER, /* Text format metadata area header */
DEV_IO_MDA_CONTENT, /* Text format metadata area content */
DEV_IO_MDA_EXTRA_HEADER, /* Header of any extra metadata areas on device */
DEV_IO_MDA_EXTRA_CONTENT, /* Content of any extra metadata areas on device */
DEV_IO_FMT1, /* Original LVM1 metadata format */
DEV_IO_POOL, /* Pool metadata format */
DEV_IO_LV, /* Content written to an LV */
DEV_IO_LOG /* Logging messages */
} dev_io_reason_t;
struct device_list {
struct dm_list list;
struct device *dev;
};
struct device_area {
struct device *dev;
uint64_t start; /* Bytes */
uint64_t size; /* Bytes */
};
/*
* Support for external device info.
*/
const char *dev_ext_name(struct device *dev);
int dev_ext_enable(struct device *dev, dev_ext_t src);
int dev_ext_disable(struct device *dev);
struct dev_ext *dev_ext_get(struct device *dev);
int dev_ext_release(struct device *dev);
/*
* Increment current dev_size_seqno.
* This is used to control lifetime
* of cached device size.
*/
void dev_size_seqno_inc(void);
/*
* All io should use these routines.
*/
int dev_get_direct_block_sizes(struct device *dev, unsigned int *physical_block_size,
unsigned int *logical_block_size);
int dev_get_size(struct device *dev, uint64_t *size);
int dev_get_read_ahead(struct device *dev, uint32_t *read_ahead);
int dev_discard_blocks(struct device *dev, uint64_t offset_bytes, uint64_t size_bytes);
/* Use quiet version if device number could change e.g. when opening LV */
int dev_open(struct device *dev);
int dev_open_quiet(struct device *dev);
int dev_open_flags(struct device *dev, int flags, int direct, int quiet);
int dev_open_readonly(struct device *dev);
int dev_open_readonly_buffered(struct device *dev);
int dev_open_readonly_quiet(struct device *dev);
int dev_close(struct device *dev);
int dev_close_immediate(struct device *dev);
int dev_fd(struct device *dev);
const char *dev_name(const struct device *dev);
void dev_flush(struct device *dev);
struct device *dev_create_file(const char *filename, struct device *dev,
struct dm_str_list *alias, int use_malloc);
void dev_destroy_file(struct device *dev);
/* Return a valid device name from the alias list; NULL otherwise */
const char *dev_name_confirmed(struct device *dev, int quiet);
#endif
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