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There's no need to have the device open RW while obtaining the readahead value.
The RW open used before caused the CHANGE udev event to be generated if the
WATCH udev rule was set for the underlying device (and that is normally the
case both for non-dm and dm devices by default).
This did not cause any problems before since we were not interested in
*underlying* devices. However, with upcoming changes (autoactivation), we're
watching for events on underlying devices marked as PVs and such a spurious
event could cause the autoactivation code to be triggered. So when trying
to deactivate the volume, we could end up with immediate activation just after
that because of the CHANGE event originated in the WATCH udev rule since the
underlying device was open RW during the deactivation process.
Though maybe a better solution would be to completely filter such spurious
events out of the autoactivation process somehow, it's still useful if there
are as least spurious events generated as possible in the system itself.
Libudev does not provide transactions when querying udev database - once we
get the list of block devices (devices/obtain_device_list_from_udev=1) and
we iterate over the list to get more detailed information about device node
and symlink names used etc., the device could be removed just in between we
get the list and put a query for more info. In this case, libudev returns
NULL value as the device does not exist anymore.
Recently, we've added a warning message to reveal such situations. However,
this could be misleading if the device is not related to the LVM action
we're just processing - the non-related block device could be removed in
parallel and this is not an error but a possible and normal operation.
(N.B. This "missing info" should not happen when devices are related to
the LVM action we're just processing since all such processing should be
synchronized with udev and the udev db must always be in consistent state
after the sync point. But we can't filter this situation out from others,
non-related devices, so we have to lower the message verbosity here for a
general solution.)
Save some relocation entries and use directly char[].
Since we do not need yes more then 127 partitions per device, use just int8_t.
Move lvm_type_filter_destroy into local static function.
Avoid using NULL pointers from udev. It seems like some older versions of udev
were improperly returning NULL in some case, so do not silently break here,
and give at least a warning to the user.
Since the function dev_close() has code path, which really could close
file (for unlocked vg) and destroy dev handler, stay on safe side and move
the close few lines later, even our current use case shouldn't trigger
such scenario.
Since the !(dev->flags & DEV_REGULAR) code path just called
dev_name_confirmed() which has just called 'stat()' inside,
remove duplicate second stat() call here.
When both path have identical prefix i.e. /dev/disk/by-id
skip 2 x lstat() for /dev /dev/disk /dev/disk/by-id
and directly lstat() only different part of the path.
Reduces amount of lstat calls on system with lots of devices.
leaving behind the LVM-specific parts of the code (convenience wrappers that
handle `struct device` and `struct cmd_context`, basically). A number of
functions have been renamed (in addition to getting a dm_ prefix) -- namely,
all of the config interface now has a dm_config_ prefix.
If MD linear device has set rounding (overload chunk size attribute),
the pvcreate command prints this warning:
/dev/md0 sysfs attr level not in expected format: linear
Before, we used vg_write_lock_held call to determnine the way a device is
opened. Unfortunately, this opened many devices in RW mode when it was not
really necessary. With the OPTIONS+="watch" rule used in the udev rules,
this could fire numerous events while closing such devices (and it caused
useless scans from within udev rules in return).
A common bug we hit with this was with the lvremove command which was unable
to remove the LV since it was being opened from within the udev rules. This
patch should minimize such situations (at least with respect to LVM handling
of devices).
Though there's still a possibility someone will open a device 'outside' in
parallel and fire the event based on the watch rule when closing a device
once opened for RW.
Also, add a new 'obtain_device_list_from_udev' setting to lvm.conf with which
we can turn this feature on or off if needed.
If set, the cache of block device nodes with all associated symlinks
will be constructed out of the existing udev database content.
This avoids using and opening any inapplicable non-block devices or
subdirectories found in the device directory. This setting is applied
to udev-managed device directory only, other directories will be scanned
fully. LVM2 needs to be compiled with udev support for this setting to
take effect. N.B. Any device node or symlink not managed by udev in
udev directory will be ignored with this setting on.
Return value of readlink limits valid string size.
Characters after returned size present some garbage to printf.
Fix it by placing '\0' on the return size value.
New strategy for memory locking to decrease the number of call to
to un/lock memory when processing critical lvm functions.
Introducing functions for critical section.
Inside the critical section - memory is always locked.
When leaving the critical section, the memory stays locked
until memlock_unlock() is called - this happens with
sync_local_dev_names() and sync_dev_names() function call.
memlock_reset() is needed to reset locking numbers after fork
(polldaemon).
The patch itself is mostly rename:
memlock_inc -> critical_section_inc
memlock_dec -> critical_section_dec
memlock -> critical_section
Daemons (clmvd, dmevent) are using memlock_daemon_inc&dec
(mlockall()) thus they will never release or relock memory they've
already locked memory.
Macros sync_local_dev_names() and sync_dev_names() are functions.
It's better for debugging - and also we do not need to add memlock.h
to locking.h header (for memlock_unlock() prototyp).
Change API interface to accept even completely const array patterns.
This should present no change for libdm users and allows to pass
pattern arrays without cast to const char **.
To have better control were the config tree could be modified use more
const pointers and very carefully downcast them back to non-const
(for config tree merge).
One shiny day we should use libblkid here. But now using LUKS is
very common together with LVM and pvcreate destroys LUKS completely.
So for user's convenience, try to detect LUKS signature and allow abort.
We can already detect MD devices internally. But when using MD partitions,
these have "block extended major" (blkext) assigned (259). Blkext major
is also used in general, so we need to check whether the original device
is an MD device actually.
