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With existing code, the cache was working only to the 2nd. locking.
So i.e. when 'lvs' scans system with more then one VG, the caching
was effectively not working.
Update the code, so the label invalidate code is able to update DM
cache - so whenever we take a new lock - we will refresh the cache.
TODO: the refresh ATM does a very simple compare of old a new list
of cached DM device, and with the first spotted difference, it just
fallback to the full rebuild of DM cache - with large amount of active
devices this might not the most efficient way....
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.
The dm devs cache is separate from the ordinary dev cache,
so give the function names distinct prefixes, using
"dm_devs_cache" to prefix dm devs cache functions.
When a PV is stacked on an LV, the PV needs to be
dropped from bcache before the LV is processed.
The LV can be found in dev-cache using its name
rather than the devno.
The list of dm devs was in the cmd struct and had a
different lifetime than the radix trees referencing
those dm devs. Now the list and radix trees are
created and destroyed together.
In the context of dm, 'device' refers to a dm device, but
in the context of lvm, 'device' refers to struct device.
Change some lvm function names to make that difference clearer.
dev_manager_get_device_list() -> dev_manager_get_dm_active_devices()
get_device_list() -> get_dm_active_devices()
device_get_uuid() -> dev_dm_uuid(), devno_dm_uuid()
For large device sets our dm_hash can produce larger amounf of mapping
collision and we would need to further increase our has size.
So instead use the radix_tree code which is immune agains growing size
of devices and uses memory more effiecently to store all the paths.
Instead of less efficient 'btree' switch dev_cache to use
radix_tree, that is generating more efficient tree mapping.
Some direct use of btree iteration replace with our dev_iter code.
Move the code around caching active dm device devno, name and uuid
from device_mapper/libdm-iface to dev_cache file - as libdm layer
cares about 'decoding' ioctl data from kernel and caching for use by
lvm stays within lvm.
Introduce:
dev_cache_update_dm_devs
dev_cache_get_dm_dev_by_devno
dev_cache_get_dm_dev_by_uuid
Use radix_tree for searching.
Size of these hashes was quite small, so raise the size of
hashed entries to reduce amount of hash collistion.
Select some unique/unused number for hash_create below 8192.
Replace call to get_dm_uuid_from_sysfs() with use of
device_get_uuid() which gets the same information,
but instead of several syscalls it need either 1 or even 0
when the information is cached with newer kernels.
For better use of cached data located within cmd_context,
pass this structure from the top level function.
Also add missing '_' for static _dev_cache_index_devs.
No other change here.
Skip scan and stat() for dirs and nodes within known /dev/ paths,
where no block devices are located.
Also strlen(_cache.dev_dir) just once.
TODO: add more dirs to _no_scan (configurable via lvm.conf ?)
If lvm.conf has use_devicesfile=0 and /etc/lvm/device/system.devices
exists, then rename it to system.devices-unused.YYYYMMDD.HHMMSS.
This prevents an old, incorrect system.devices from being used in
the future if lvm.conf is changed to use_devicesfile=1.
Take the devices file lock before creating a new devices file.
(Was missed by the change to preemptively create the devices
file prior to setup_devices(), which was done to improve the
error path.)
to compare with wwids in /etc/multipath/wwids when
excluding multipath components. The wwid printed
from the sysfs wwid file may not be the wwid used
in multipath wwids. Save the wwids found for each
device on dev->wwids to avoid repeating reading
and parsing the sysfs files.
A typo of the filename after --devicesfile should result in a
command error rather than the command falling back to using no
devices file at all. Exception is vgcreate|pvcreate which
create a new devices file if the file name doesn't exist.
along with some basic checks for cases when a device
has no aliases.
lvm itself creates many situations where a struct device
has no valid paths, when it activates and opens an LV,
does something with it, e.g. zeroing, and then closes
and deactivates it. (dev-cache is intended for PVs, and
the use of LVs should be moved out of dev-cache in a
future patch.)
