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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.
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.
Fixes commit 63b469c160
"device_id: fix hints with device ids"
It's not correct for internal filtering to be a factor
in validating the set of devs that are the basis for hints.
Instead, look for inconsistencies between a hint entry and
the corresponding devices file entry.
Fix some interactions between device IDs and hints. Hints
may limit the scanned devices which should not always trigger
a search for the PVs that were intentionally not scanned.
Hints should also be invalidated if they contain a device
that's become excluded by an internal filter such as the
device_id filter.
Fix commit 847f1dd99c
"device_id: rewrite validation of devname entries"
which began calling device_ids_refresh() in cases where it
was unnecessary, leading to extra PV searches and warnings.
Specifically, a command like "lvs <vg>" would use the hints
file to scan only devices for the named VG. This means that
scanning other PVs would be skipped, and device IDs of those
PVs could not be validated because there are no PVID values
to verify. This missing info would cause messages about
the missing info, and would cause device_ids_refresh to
search for the PVs that had been intentionally skipped.
If the system changes, locate PVs that appear on different devices,
and update the device IDs in the devices file. A system change is
detected by saving the DMI product_uuid or hostname in the devices
file, and comparing it to the current system value. If a root PV
is restored or copied to a new system with different devices, then
the product_uuid or hostname should change, and trigger lvm to
locate PVIDs from system.devices on new devices.
With the recent use of DEVLINKS, there is no longer any real
point in checking the filter for symlink names. Removing
this check should not change behavior with or without symlinks
in the filter.
"vgchange -aay --autoactivation event" is called by our udev rule.
When the udev rule runs, symlinks for devices may not all be created
yet. If the regex filter contains symlinks, it won't work correctly.
This command uses devices that already passed through pvscan. Since
pvscan applies the regex filter correctly, this command inherits the
filtering from pvscan and can skip the regex filter itself.
See the previous commit
"pvscan: use alternate device names from DEVLINKS to check filter"
Change messages that refer to devices being "excluded by filters"
to say just "excluded". This will avoid mistaking the word
"filters" with the lvm.conf filter setting.
dev_name(dev) returns "[unknown]" if there are no names
on dev->aliases. It's meant mainly for log messages.
Many places assume a valid path name is returned, and
use it directly. A caller that wants to use the path
from dev_name() must first check if the dev has any
paths with dm_list_empty(&dev->aliases).
In a certain disconnected state, a block device is present on
the system, can be opened, reports a valid size, reports the
correct device id (wwid), and matches a devices file entry.
But, reading the device can still fail. In this case,
device_ids_validate() was misinterpreting the read error as
the device having no data/label on it (and no PVID).
The validate function would then clear the PVID from the
devices file entry for the device, thinking that it was
fixing the devices file (making it consistent with the on disk
state.) Fix this by not attempting to check and correct a
devices file entry that cannot be read. Also make this case
explicit in the hints validation code (which was doing the
right thing but indirectly.)
Since we check for present DM devices - cache result for
futher use of checking presence of such device.
lvm2 uses cache result for label scan, but also when
it tries to activate or deactivate LV - however only simple
target 'striped' is reasonably supported.
Use disable_dm_devs to be able to control when lv_info()
get cache or uncached results.
TODO: support more type, however this is getting very complicated.
Remove the searched_devnames file in a couple more places:
. When hints need refreshing it's possible that a missing
devices file entry could be found by searching devices
again.
. When a devices file entry devname is first found to be
incorrect, a new search for missing entries may be
useful.
If the optimized label scan fails (using online files),
then clear the device state prior to falling back to the
standard label_scan. This avoids printing output about
unexpected state.
Copy another optimization from pvscan -aay to vgchange -aay.
When using the optimized label scan for only one VG, acquire the
VG lock prior to the scan. This allows vg_read to then skip the
repeated label scan that normally happens after locking the vg.
Include the device name in the /run/lvm/pvs_online/pvid files.
Commands using the pvid file can use the devname to more quickly
find the correct device, vs finding the device using the
major:minor number. If the devname in the pvid file is missing
or incorrect, fall back to using the devno.
For completeness and consistency, adjust the behavior
for some variations of:
vgchange -aay --autoactivation event [vgname]
The current standard use is with a VG name arg, and the
command is only called when all pvs_online files exist.
This is the optimal case, in which only pvs_online devs
are read. This remains the same.
Clean up behaviors for some other unexpected uses of the
command:
. With no VG name arg, the command activates any VGs
that are complete according to pvs_online. If no
pvs_online files exist, it does nothing.
. If a VG name is used but no PVs online files exist for
the VG, or the PVs online files are incomplete, then
consider there could be a problem with the pvs_online
files, and fall back to a full label scan prior to
attempting the activation.
Part of the optimization to avoid a full dev_cache_scan requires
translating major:minor numbers to a device name. If this devno
translation fails, then fall back to doing a full dev_cache_scan
which is slower but certain to provide the info. This preserves
the most important part of the label scanning optimization in the
vgchange aay (avoiding dev_cache_scan is a relatively small part
of the optimized activation compared to label scanning.)
Port another optimization from pvscan -aay to vgchange -aay:
"pvscan: only add device args to dev cache"
This optimization avoids doing a full dev_cache_scan, and
instead populates dev-cache with only the devices in the
VG being activated.
This involves shifting the use of pvs_online files from
the hints interface up to the higher level label_scan
interface. This specialized label_scan is structured
around creating a list of devices from the pvs_online
files. Previously, a list of all devices was created
first, and then reduced based on the pvs_online files.
The initial step of listing all devices was slow when
thousands of devices are present on the system.
This optimization extends the previous optimization that
used pvs_online files to limit the devices that were
actually scanned (i.e. reading to identify the device):
"vgchange -aay: optimize device scan using pvs_online files"
The information in /run/lvm/pvs_online/<pvid> files can
be used to build a list of devices for a given VG.
The pvscan -aay command has long used this information to
activate a VG while scanning only devices in that VG, which
is an important optimization for autoactivation.
This patch implements the same thing through the existing
device hints interface, so that the optimization can be
applied elsewhere. A future patch will take advantage of
this optimization in vgchange -aay, which is now used in
place of pvscan -aay for event activation.
Reporting non-PVs / "all devices" is only done by
pvs -a or pvdisplay -a, so avoid the work managing
a list of all devices in process_each_pv.
In the case when it's needed, use the results of
label_scan which already determines which devs
are not PVs.
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.)
If label_scan encounters bad vg metadata, invalidate
bcache data for the device and reread the mda_header
and metadata text back to back. With concurrent commands
modifying large metadata, it's possible that the entire
metadata area can be rewritten in the time between a
command reading the mda_header and reading the metadata
text that the header points to. Since the label_scan
is just assembling an initial overview of devices, it
doesn't use locking to serialize with other commands
that may be modifying the vg metadata at the same time.
