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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.)
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.
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"
When scanning configured /dev dir, avoid entring
directories with different filesystem.
This minimizes risk we will block on i.e. entring
directory with mount point.
expands commit d5a06f9a7d
"pvscan: skip indexing devices used by LVs"
The dev cache index is expensive and slow, so limit it
to commands that are used to observe the state of lvm.
The index is only used to print warnings about incorrect
device use by active LVs, e.g. if an LV is using a
multipath component device instead of the multipath
device. Commands that continue to use the index and
print the warnings:
fullreport, lvmdiskscan, vgs, lvs, pvs,
vgdisplay, lvdisplay, pvdisplay,
vgscan, lvscan, pvscan (excluding --cache)
A couple other commands were borrowing the DEV_USED_FOR_LV
flag to just check if a device was actively in use by LVs.
These are converted to the new dev_is_used_by_active_lv().
dev_cache_index_devs() is taking a large amount of time
when there are many PVs. The index keeps track of
devices that are currently in use by active LVs. This
info is used to print warnings for users in some limited
cases.
The checks/warnings that are enabled by the index are not
needed by pvscan --cache, so disable it in this case.
This may be expanded to other cases in future commits.
dev_cache_index_devs should also be improved in another
commit to avoid the extreme delays with many devices.
This case happens when i.e. we convert LV to another type,
when we change existing LV into a different type - so change
to debug level and avoid confusing users with message about
Device path not match.
We may eventually enhnace caching code to drop cached info
after taking lock and reading VG.
Use different 'hint' size for dm_hash_create() call - so
when debug info about hash is printed we can recognize which
hash was in use.
This patch doesn't change actual used size since that is always
rounded to be power of 2 and >=16 - so as such is only a
help to developer.
We could eventually use 'name' arg, but since this would have changed
API and this patchset will be routed to libdm & stable - we will
just use this small trick.
Use 'C' for alphasort - there is no need to use localized and slower
sorting for internal directory scanning.
Ensure on all code paths allocated dirent entries are released.
Optimize full path construction.
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
Add a "device index" (di) for each device, and use this
in the bcache api to the rest of lvm. This replaces the
file descriptor (fd) in the api. The rest of lvm uses
new functions bcache_set_fd(), bcache_clear_fd(), and
bcache_change_fd() to control which fd bcache uses for
io to a particular device.
. lvm opens a dev and gets and fd.
fd = open(dev);
. lvm passes fd to the bcache layer and gets a di
to use in the bcache api for the dev.
di = bcache_set_fd(fd);
. lvm uses bcache functions, passing di for the dev.
bcache_write_bytes(di, ...), etc.
. bcache translates di to fd to do io.
. lvm closes the device and clears the di/fd bcache state.
close(fd);
bcache_clear_fd(di);
In the bcache layer, a di-to-fd translation table
(int *_fd_table) is added. When bcache needs to
perform io on a di, it uses _fd_table[di].
In the following commit, lvm will make use of the new
bcache_change_fd() function to change the fd that
bcache uses for the dev, without dropping cached blocks.
Switch remaining zero sized struct to flexible arrays to be C99
complient.
These simple rules should apply:
- The incomplete array type must be the last element within the structure.
- There cannot be an array of structures that contain a flexible array member.
- Structures that contain a flexible array member cannot be used as a member of another structure.
- The structure must contain at least one named member in addition to the flexible array member.
Although some of the code pieces should be still improved.
