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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
dm-integrity stores checksums of the data written to an
LV, and returns an error if data read from the LV does
not match the previously saved checksum. When used on
raid images, dm-raid will correct the error by reading
the block from another image, and the device user sees
no error. The integrity metadata (checksums) are stored
on an internal LV allocated by lvm for each linear image.
The internal LV is allocated on the same PV as the image.
Create a raid LV with an integrity layer over each
raid image (for raid levels 1,4,5,6,10):
lvcreate --type raidN --raidintegrity y [options]
Add an integrity layer to images of an existing raid LV:
lvconvert --raidintegrity y LV
Remove the integrity layer from images of a raid LV:
lvconvert --raidintegrity n LV
Settings
Use --raidintegritymode journal|bitmap (journal is default)
to configure the method used by dm-integrity to ensure
crash consistency.
Initialization
When integrity is added to an LV, the kernel needs to
initialize the integrity metadata/checksums for all blocks
in the LV. The data corruption checking performed by
dm-integrity will only operate on areas of the LV that
are already initialized. The progress of integrity
initialization is reported by the "syncpercent" LV
reporting field (and under the Cpy%Sync lvs column.)
Example: create a raid1 LV with integrity:
$ lvcreate --type raid1 -m1 --raidintegrity y -n rr -L1G foo
Creating integrity metadata LV rr_rimage_0_imeta with size 12.00 MiB.
Logical volume "rr_rimage_0_imeta" created.
Creating integrity metadata LV rr_rimage_1_imeta with size 12.00 MiB.
Logical volume "rr_rimage_1_imeta" created.
Logical volume "rr" created.
$ lvs -a foo
LV VG Attr LSize Origin Cpy%Sync
rr foo rwi-a-r--- 1.00g 4.93
[rr_rimage_0] foo gwi-aor--- 1.00g [rr_rimage_0_iorig] 41.02
[rr_rimage_0_imeta] foo ewi-ao---- 12.00m
[rr_rimage_0_iorig] foo -wi-ao---- 1.00g
[rr_rimage_1] foo gwi-aor--- 1.00g [rr_rimage_1_iorig] 39.45
[rr_rimage_1_imeta] foo ewi-ao---- 12.00m
[rr_rimage_1_iorig] foo -wi-ao---- 1.00g
[rr_rmeta_0] foo ewi-aor--- 4.00m
[rr_rmeta_1] foo ewi-aor--- 4.00m
Since we need to preserve allocated strings across 2 separate
activation calls of '_tree_action()' we need to use other mem
pool them dm->mem - but since cmd->mem is released between
individual lvm2 locking calls, we rather introduce a new separate
mem pool just for pending deletes with easy to see life-span.
(not using 'libmem' as it would basicaly keep allocations over
the whole lifetime of clvmd)
This patch is fixing previous commmit where the memory was
improperly used after pool release.
With previous patch 30a98e4d67 we
started to put devices one pending_delete list instead
of directly scheduling their removal.
However we have operations like 'snapshot merge' where we are
resuming device tree in 2 subsequent activation calls - so
1st such call will still have suspened devices and no chance
to push 'remove' ioctl.
Since we curently cannot easily solve this by doing just single
activation call (which would be preferred solution) - we introduce
a preservation of pending_delete via command structure and
then restore it on next activation call.
This way we keep to remove devices later - although it might be
not the best moment - this may need futher tunning.
Also we don't keep the list of operation in 1 trasaction
(unless we do verify udev symlinks) - this could probably
also make it more correct in terms of which 'remove' can
be combined we already running 'resume'.
Save the previous duplicate PVs in a global list instead
of a list on the cmd struct. dmeventd reuses the cmd struct
for multiple commands, and the list entries between commands
were being freed (apparently), causing a segfault in dmeventd
when it tried to use items in cmd->unused_duplicate_devs
that had been saved there by the previous command.
which defines the amount of memory that lvm will allocate
for bcache. Increasing this setting is required if it is
smaller than a single copy of VG metadata.
For users who do not want all of the fields included
in debug lines, let them specify in lvm.conf which
fields to include. timestamp, command[pid], and
file:line fields can all be disabled.
Without this, the output from different commands in a single
log file could not be separated.
Change the default "indent" setting to 0 so that the default
debug output does not include variable spaces in the middle
of debug lines.
Save the list of PVs in /run/lvm/hints. These hints
are used to reduce scanning in a number of commands
to only the PVs on the system, or only the PVs in a
requested VG (rather than all devices on the system.)
io_setup() for aio may fail if a system has reached the
aio request limit. In this case, fall back to using
sync io. Also, lvm use of aio can be disabled entirely
with config setting global/use_aio=0.
The system limit for aio requests can be seen from
/proc/sys/fs/aio-max-nr
The current usage of aio requests can be seen from
/proc/sys/fs/aio-nr
The system limit for aio requests can be increased by
setting fs.aio-max-nr using sysctl.
Also add last-byte limit to the sync io code.
When persistent_filter_create() fails, the existing passed filter
should be preserved, so it could be properly deleted on
error path - so new pfilter is assigned instead.
devices/scan_lvs (default 1) determines whether lvm
will scan LVs for layered PVs. The lvm behavior has
always been to scan LVs, but it's rare for LVs to have
layered PVs, and much more common for there to be many
LVs that substantially slow down scanning with no benefit.
This is implemented in the usable filter, and has the
same effect as listing all LVs in the global_filter.
Native disk scanning is now both reduced and
async/parallel, which makes it comparable in
performance (and often faster) when compared
to lvm using lvmetad.
Autoactivation now uses local temp files to record
online PVs, and no longer requires lvmetad.
There should be no apparent command-level change
in behavior.
It's no longer needed. Clustered VGs are now handled in
the same way as foreign VGs, and as shared VGs that
can't be accessed:
- A command processing all VGs sees a clustered VG,
prints a message ("Skipping clustered VG foo."),
skips it, and does not fail.
- A command where the clustered VG is explicitly
named on the command line, prints a message and fails.
"Cannot access clustered VG foo, see lvmlockd(8)."
The option is listed in the set of ignored options for
the commands that previously accepted it. (Removing it
entirely would cause commands/scripts to fail if they
set it.)
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
Filters are still applied before any device reading or
the label scan, but any filter checks that want to read
the device are skipped and the device is flagged.
After bcache is populated, but before lvm looks for
devices (i.e. before label scan), the filters are
reapplied to the devices that were flagged above.
The filters will then find the data they need in
bcache.
The clvmd saved_vg data is independent from the normal lvm
lvmcache vginfo data, so separate saved_vg from vginfo.
Normal lvm doesn't need to use save_vg at all, and in clvmd,
lvmcache changes on vginfo can be made without worrying
about unwanted effects on saved_vg.
There are likely more bits of code that can be removed,
e.g. lvm1/pool-specific bits of code that were identified
using FMT flags.
The vgconvert command can likely be reduced further.
The lvm1-specific config settings should probably have
some other fields set for proper deprecation.
The copy of VG metadata stored in lvmcache was not being used
in general. It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation. There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.
This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.
This is a way of passing the VG from suspend to resume in
clvmd. Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.) The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo. These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd. The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.
suspend has both old (current) and new (precommitted)
copies of the VG metadata. It stashes both of these in
the vginfo prior to suspending devices. When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.
resume grabs the VG stashed by suspend. If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG. The VG is then used to resume
LVs.
This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.
Sequence of operations:
- lv_suspend() has both vg_old and vg_new
and stashes a copy of each onto the vginfo:
lvmcache_save_suspended_vg(vg_old);
lvmcache_save_suspended_vg(vg_new);
- vg_commit() happens, which causes all clvmd
instances to call lvmcache_commit_metadata(vg).
A flag is set in the vginfo indicating the
transition from the old to new VG:
vginfo->suspended_vg_committed = 1;
- lv_resume() needs either vg_old or vg_new
to use in resuming LVs. It doesn't want to
read the VG from disk since devices are
suspended, so it gets the VG stashed by
lv_suspend:
vg = lvmcache_get_suspended_vg(vgid);
If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
New label_scan function populates bcache for each device
on the system.
The two read paths are updated to get data from bcache.
The bcache is not yet used for writing. bcache blocks
for a device are invalidated when the device is written.
With pthreaded daemons like 'dmeventd' using liblvm via plugin,
lvm2 actually should not 'play' with streams at all - as there
could be parallel outputs running.
As a current quick workaround just disable change for pthreaded
program (gettid() != getpid()).
TODO: it's possible the change of buffering actually doesn't serve us
any measurable benefit and could be dropped as whole later...
Meanwhile this patch is fixing this occasional valgrind race report:
Invalid read of size 4
at 0x571892C: vfprintf (in /usr/lib64/libc-2.26.9000.so)
by 0x57216B3: fprintf (in /usr/lib64/libc-2.26.9000.so)
by 0x5042886: dm_event_log (libdevmapper-event.c:925)
by 0x10B015: _dmeventd_log (dmeventd.c:125)
by 0x10D289: _unregister_for_event (dmeventd.c:1146)
by 0x10E52E: _handle_request (dmeventd.c:1583)
by 0x10E6D7: _do_process_request (dmeventd.c:1631)
by 0x10E7C6: _process_request (dmeventd.c:1660)
by 0x1101A4: main (dmeventd.c:2285)
Address 0x6264d30 is 192 bytes inside a block of size 552 free'd
at 0x4C2ED68: free (vg_replace_malloc.c:530)
by 0x573907D: fclose@@GLIBC_2.2.5 (in /usr/lib64/libc-2.26.9000.so)
by 0x6AC5C00: reopen_standard_stream (log.c:189)
by 0x6A8E62C: destroy_toolcontext (toolcontext.c:2271)
by 0x6BA5C22: lvm_fin (lvmcmdline.c:3339)
by 0x6BD5EF3: lvm2_exit (lvmcmdlib.c:123)
by 0x6856013: dmeventd_lvm2_exit (dmeventd_lvm.c:103)
by 0x66535B8: unregister_device (dmeventd_thin.c:432)
by 0x10CBBC: _do_unregister_device (dmeventd.c:926)
by 0x10CD74: _monitor_unregister (dmeventd.c:979)
by 0x10D094: _monitor_thread (dmeventd.c:1066)
by 0x54B35E0: start_thread (in /usr/lib64/libpthread-2.26.9000.so)
by 0x57C30EE: clone (in /usr/lib64/libc-2.26.9000.so)
Block was alloc'd at
at 0x4C2DBBB: malloc (vg_replace_malloc.c:299)
by 0x573932B: fdopen@@GLIBC_2.2.5 (in /usr/lib64/libc-2.26.9000.so)
by 0x6AC5DC2: reopen_standard_stream (log.c:200)
by 0x6A8D11D: create_toolcontext (toolcontext.c:1898)
by 0x6BA5B6B: init_lvm (lvmcmdline.c:3319)
by 0x6BD5BC8: cmdlib_lvm2_init (lvmcmdlib.c:34)
by 0x6BD5F04: lvm2_init (lvm2cmd.c:20)
by 0x6855EA7: dmeventd_lvm2_init (dmeventd_lvm.c:67)
by 0x665305F: register_device (dmeventd_thin.c:352)
by 0x10CB7A: _do_register_device (dmeventd.c:916)
by 0x10CEE4: _monitor_thread (dmeventd.c:1006)
by 0x54B35E0: start_thread (in /usr/lib64/libpthread-2.26.9000.so)
by 0x57C30EE: clone (in /usr/lib64/libc-2.26.9000.so)
....
Process terminating with default action of signal 6 (SIGABRT): dumping core
at 0x570016B: raise (in /usr/lib64/libc-2.26.9000.so)
by 0x5701520: abort (in /usr/lib64/libc-2.26.9000.so)
by 0x57437D8: __libc_message (in /usr/lib64/libc-2.26.9000.so)
by 0x5743831: __libc_fatal (in /usr/lib64/libc-2.26.9000.so)
by 0x5744056: _IO_vtable_check (in /usr/lib64/libc-2.26.9000.so)
by 0x574751C: __overflow (in /usr/lib64/libc-2.26.9000.so)
by 0x574191A: fputc (in /usr/lib64/libc-2.26.9000.so)
by 0x50428E3: dm_event_log (libdevmapper-event.c:934)
by 0x10B015: _dmeventd_log (dmeventd.c:125)
by 0x10D289: _unregister_for_event (dmeventd.c:1146)
by 0x10E52E: _handle_request (dmeventd.c:1583)
by 0x10E6D7: _do_process_request (dmeventd.c:1631)
by 0x10E7C6: _process_request (dmeventd.c:1660)
by 0x1101A4: main (dmeventd.c:2285)
