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

2 files changed, 33 insertions, 1 deletions

diff --git a/lib/commands/toolcontext.c b/lib/commands/toolcontext.c
index 63b6811e5..c3de18d7f 100644
--- a/lib/commands/toolcontext.c
+++ b/lib/commands/toolcontext.c
@@ -32,6 +32,7 @@
 #include "lib/cache/lvmcache.h"
 #include "lib/format_text/archiver.h"
 #include "lib/lvmpolld/lvmpolld-client.h"
+#include "lib/device/device_id.h"
 
 #include <locale.h>
 #include <sys/stat.h>
@@ -1066,7 +1067,7 @@ static int _init_dev_cache(struct cmd_context *cmd)
 	return 1;
 }
 
-#define MAX_FILTERS 10
+#define MAX_FILTERS 11
 
 static struct dev_filter *_init_filter_chain(struct cmd_context *cmd)
 {
@@ -1085,6 +1086,9 @@ static struct dev_filter *_init_filter_chain(struct cmd_context *cmd)
 	 * sysfs filter. Only available on 2.6 kernels.  Non-critical.
 	 * Listed first because it's very efficient at eliminating
 	 * unavailable devices.
+	 *
+	 * TODO: I suspect that using the lvm_type and device_id
+	 * filters before this one may be more efficient.
 	 */
 	if (find_config_tree_bool(cmd, devices_sysfs_scan_CFG, NULL)) {
 		if ((filters[nr_filt] = sysfs_filter_create()))
@@ -1123,6 +1127,13 @@ static struct dev_filter *_init_filter_chain(struct cmd_context *cmd)
 	}
 	nr_filt++;
 
+	/* filter based on the device_ids saved in the devices file */
+	if (!(filters[nr_filt] = deviceid_filter_create(cmd))) {
+		log_error("Failed to create deviceid device filter");
+		goto bad;
+	}
+	nr_filt++;
+
 	/* usable device filter. Required. */
 	if (!(filters[nr_filt] = usable_filter_create(cmd, cmd->dev_types, FILTER_MODE_NO_LVMETAD))) {
 		log_error("Failed to create usabled device filter");
@@ -1485,6 +1496,7 @@ int init_run_by_dmeventd(struct cmd_context *cmd)
 	init_dmeventd_monitor(DMEVENTD_MONITOR_IGNORE);
 	init_ignore_suspended_devices(1);
 	init_disable_dmeventd_monitoring(1); /* Lock settings */
+	cmd->run_by_dmeventd = 1;
 
 	return 0;
 }
@@ -1717,6 +1729,8 @@ struct cmd_context *create_toolcontext(unsigned is_clvmd,
 	if (!_init_dev_cache(cmd))
 		goto_out;
 
+	devices_file_init(cmd);
+
 	memlock_init(cmd);
 
 	if (!_init_formats(cmd))
@@ -1842,6 +1856,7 @@ int refresh_toolcontext(struct cmd_context *cmd)
 	_destroy_segtypes(&cmd->segtypes);
 	_destroy_formats(cmd, &cmd->formats);
 
+	devices_file_exit(cmd);
 	if (!dev_cache_exit())
 		stack;
 	_destroy_dev_types(cmd);
@@ -1921,6 +1936,8 @@ int refresh_toolcontext(struct cmd_context *cmd)
 	if (!_init_dev_cache(cmd))
 		return_0;
 
+	devices_file_init(cmd);
+
 	if (!_init_formats(cmd))
 		return_0;
 
@@ -1970,6 +1987,7 @@ void destroy_toolcontext(struct cmd_context *cmd)
 	_destroy_filters(cmd);
 	if (cmd->mem)
 		dm_pool_destroy(cmd->mem);
+	devices_file_exit(cmd);
 	dev_cache_exit();
 	_destroy_dev_types(cmd);
 	_destroy_tags(cmd);
diff --git a/lib/commands/toolcontext.h b/lib/commands/toolcontext.h
index d20768ad0..977b31412 100644
--- a/lib/commands/toolcontext.h
+++ b/lib/commands/toolcontext.h
@@ -182,14 +182,27 @@ struct cmd_context {
 	unsigned pvscan_recreate_hints:1;	/* enable special case hint handling for pvscan --cache */
 	unsigned scan_lvs:1;
 	unsigned wipe_outdated_pvs:1;
+	unsigned enable_devices_list:1;		/* command is using --devices option */
+	unsigned enable_devices_file:1;		/* command is using devices file */
+	unsigned pending_devices_file:1;	/* command may create and enable devices file */
+	unsigned create_edit_devices_file:1;	/* command expects to create and/or edit devices file */
+	unsigned edit_devices_file:1;		/* command expects to edit devices file */
+	unsigned filter_deviceid_skip:1;	/* don't use filter-deviceid */
+	unsigned filter_regex_with_devices_file:1; /* use filter-regex even when devices file is enabled */
 	unsigned filter_nodata_only:1;          /* only use filters that do not require data from the dev */
+	unsigned run_by_dmeventd:1;		/* command is being run by dmeventd */
+	unsigned sysinit:1;			/* --sysinit is used */
 
 	/*
 	 * Devices and filtering.
 	 */
 	struct dev_filter *filter;
 	struct dm_list hints;
+	struct dm_list use_devices;		/* struct dev_use for each entry in devices file */
 	const char *md_component_checks;
+	const char *search_for_devnames;	/* config file setting */
+	const char *devicesfile;                /* from --devicesfile option */
+	struct dm_list deviceslist;             /* from --devices option, struct dm_str_list */
 
 	/*
 	 * Configuration.
@@ -221,6 +234,7 @@ struct cmd_context {
 	char system_dir[PATH_MAX];
 	char dev_dir[PATH_MAX];
 	char proc_dir[PATH_MAX];
+	char devices_file_path[PATH_MAX];
 
 	/*
 	 * Reporting.