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The cmd struct is now required in many more functions, and
it's added as a function arg for most direct dev-cache function
calls. The cmd struct is added to struct device (dev->cmd) so
that it can be accessed in many other cases where dev-cache
functions are being called from places where getting the cmd
struct is too difficult.
Resolve reported leak by renaming existing pckk() to pvck_mf()
and wrapping pvck() over this. This function can easily
free allocated buffer within the subfunction.
This sanity check actually confused in some way Coverity
giving it some assumption about array access.
Since these two checks basically validated compiler's capability
to add and then substract the number from char pointer we likely
don't really need them - as if this base math would not work,
compiler would be having far more troubles...
So drop them - and get rid of report:
Event overrun-call: Overrunning callee's array of size 513 by...
pvid and vgid are sometimes a null-terminated string, and
other times a 'struct id', and the two types were often
cast between each other. When a struct id was cast to a char
pointer, the resulting string would not necessarily be null
terminated. Casting a null-terminated string id to a
struct id is fine, but is still avoided when possible.
A struct id is: int8_t uuid[ID_LEN]
A string id is: char pvid[ID_LEN + 1]
A convention is introduced to help distinguish them:
- variables and struct fields named "pvid" or "vgid"
should be null-terminated strings.
- variables and struct fields named "pv_id" or "vg_id"
should be struct id's.
- examples:
char pvid[ID_LEN + 1];
char vgid[ID_LEN + 1];
struct id pv_id;
struct id vg_id;
Function names also attempt to follow this convention.
Avoid casting between the two types as much as possible,
with limited exceptions when known to be safe and clearly
commented.
Avoid using variations of strcpy and strcmp, and instead
use memcpy/memcmp with ID_LEN (with similar limited
exceptions possible.)
Fix memory leaks on error paths for allocated
path and backup_file name by converting allocation to
dm_pool_alloc and also change devicefile structure to contain
embeded path as last struct member - so we could allocate
only needed string size instead of PATH_MAX from pool.
TODO: still to be fixed 'mf' struct.
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
filters needing io weren't being run because bcache
wasn't set up. Read the first 4k of the device
before doing filtering or reading ondisk structs to
reduce reads.
It's possible for a machine with a non-4k page size
to create a PV with an mda_header at an offset other
than 4k. Fix pvck --dump to work with these other
mda offsets. pvck --repair will write a new first
mda at 4096 but lvm with other page sizes will work
with this.
pvck --dump headers reads the metadata text area
to compute the text metadata checksum to compare
with the mda_header checksum.
The new header_only will skip reading the metadata
text and not validate the mda_header checksum.
