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There's a race when asking lvmpolld about progress_status and
actually reading the progress info from kernel:
Even with lvmpolld being used we read status info from
LVM2 command issued by a user (client side from lvmpolld perspective).
The whole cycle may look like following:
1) set up an operation that requires polling (i.e. pvmove /dev/sda)
2) notify lvmpolld about such operation (lvmpolld_poll_init())
3) in case 1) was not called with --background it would continue with:
4) Ask lvmpolld about progress status. it may respond with one of:
a) in_progress
b) not_found
c) finished
d) any low level error
5) provided the answer was 4a) try to read progress info from polling LV
(i.e. vg00/pvmove1). Repeat steps 4) and 5) until the answer is != 4a).
And now we got into racy configuration: lvmpolld answered with in_progress
but it may be the that in_between 4) and 5) the operation has already
finished and polling LV is already gone or there's nothing to ask for.
Up to now, 5) would report warning and it could print such warning many
times if --interval was set to 0.
We don't want to scary users by warnings in such situation so let's just
print these messages in verbose mode. Error messages due to error while
reading kernel status info (on existing, active and locked LV) remained
the same.
currently in wait_for_single_lv() fn trying to poll missing pvmove LV
is considered success. It may have been already finished by another
instance of polldaemon. either by another forked off polldaemon
or by lvmpolld.
Let's try to handle the mirror conversion and snapshot merge the same
way.
These wrappers have been replaced by direct calls
to vg_read() and find_lv() in previous commits.
This commit should have no functional impact since
all bits were already unreachable.
let's call dev_close_all() only before we're about to 'sleep'
for at least one second during the polling.
(it's questionable whether to call dev_close_all() at all in
polldaemon code. Natural extension would be to drop it completely)
querying future lvmpolld with zero wait time is highly undesirable
and can cause serious performance drop of the future daemon. The new
wrapper function may avoid immediate return from syscal by
introducing minimal wait time on demand.
Routines responsible for polling of in-progress pvmove, snapshot merge
or mirror conversion each used custom lookup functions to find vg and
lv involved in polling.
Especially pvmove used pvname to lookup pvmove in-progress. The future
lvmpolld will poll each operation by vg/lv name (internally by lvid).
Also there're plans to make pvmove able to move non-overlaping ranges
of extents instead of single PVs as of now. This would also require
to identify the opertion in different manner.
The poll_operation_id structure together with daemon_parms structure they
identify unambiguously the polling task.
Waiting even after _check_lv_status returned success and
'finished' flag was set to true doesn't make much sense.
Note that while we skip the wait() we also skip the
init_full_scan_done(0) inside the routine. This should
have no impact as long as the code after _wait_for_single_lv
doesn't presume anything about the state of the cache.
as a part of bigger effort to unify polling intefaces
poll_get_copy_lv should be able to look up LVs based
on theirs lv->status field.
Effective after pvmove starts using poll_get_copy_lv
fn as well.
If the device name is not found in our metadata,
we cannot call strdup few lines later with NULL name.
More intersting story goes behind how it happens -
pvmove removal is unfortunatelly 'multi-state' process
and at some point (for now) we have in lvm2 metadata
LV pvmove0 as stripe and mirror image as error.
If such metadata are left - we fail with any further removal.
we do not allow 0 interval for pvmove command issued
without parameters with classical polldaemon. It would
query the kernel too often with possibly many pvmoves
in-progress.
_check_lv_status was called from within dm_list_iterate_items cycle.
This was utterly wrong! _check_lv_status may remove more than one LV from
vg->lvs list we iterated in the same time.
In some scenarios this could lead to deadlock iterationg over same LV
indefinitely or segfault depending on the circumstances.
Fixed by moving the _check_lv_status outside iterating the vg->lvs
list.
Note that commit 6e7b24d34f was not enough
as _check_lv_status may result in removal of more than one LV from the list.
When we're iterating over LVs in _poll_vg fn, we need to use the safe
version of iteration - the LV can be removed from the list which we're
just iterating over if we're finishing or aborting pvmove operation.
It's cleaner this way - do not mix static and dynamic
(init_processing_handle) initializers. Use the dynamic one everywhere.
This makes it easier to manage the code - there are no "exceptions"
then and we don't need to take care about two ways of initializing the
same thing - just use one common initializer throughout and it's clear.
Also, add more comments, mainly in the report_for_selection fn explaining
what is being done and why with respect to the processing_handle and
selection_handle.
Call _init_processing_handle, _init_selection_handle and
_destroy_processing_handle in process_each_* and related functions to
set up and destroy handles used while processing items.
This patch replaces "void *handle" with "struct processing_handle *handle"
in process_each_*, process_single_* and related functions.
The struct processing_handle consists of two handles inside now:
- the "struct selection_handle *selection_handle" used for
applying selection criteria while processing process_each_*,
process_single_* and related functions (patches using this
logic will follow)
- the "void* custom_handle" (this is actually the original handle
used before this patch - a pointer to custom data passed into
process_each_*, process_single_* and related functions).
If the we are polling an LV due to some sort of conversion and it
becomes inactive, a rather worrisome message is produced, e.g.:
" ABORTING: Mirror percentage check failed."
We can cleanly exit if we do a simple check to see if the LV is
active before performing the check. This eliminates the scary
message.
Udev daemon has recently introduced a limit on the number of udev
processes (there was no limit before). This causes a problem
when calling pvscan --cache -aay in lvmetad udev rules which
is supposed to activate the volumes. This activation is itself
synced with udev and so it waits for the activation to complete
before the pvscan finishes. The event processing can't continue
until this pvscan call is finished.
But if we're at the limit with the udev process count, we can't
instatiate any more udev processes, all such events are queued
and so we can't process the lvm activation event for which the
pvscan is waiting.
Then we're in a deadlock since the udev process with the
pvscan --cache -aay call waits for the lvm activation udev
processing to complete, but that will never happen as there's
this limit hit with the number of udev processes.
The process with pvscan --cache -aay actually times out eventually
(3min or 30sec, depends on the version of udev).
This patch makes it possible to run the pvscan --cache -aay
in the background so the udev processing can continue and hence
we can avoid the deadlock mentioned above.
For example, the old call and reference:
find_config_tree_str(cmd, "devices/dir", DEFAULT_DEV_DIR)
...now becomes:
find_config_tree_str(cmd, devices_dir_CFG)
So we're referring to the named configuration ID instead
of passing the configuration path and the default value
is taken from central config definition in config_settings.h
automatically.
Accept -q as the short form of --quiet.
Suppress non-essential standard output if -q is given twice.
Treat log/silent in lvm.conf as equivalent to -qq.
Review all log_print messages and change some to
log_print_unless_silent.
When silent, the following commands still produce output:
dumpconfig, lvdisplay, lvmdiskscan, lvs, pvck, pvdisplay,
pvs, version, vgcfgrestore -l, vgdisplay, vgs.
[Needs checking.]
Non-essential messages are shifted from log level 4 to log level 5
for syslog and lvm2_log_fn purposes.
Adding couple INTERNAL_ERROR reports for unwanted parameters:
Ensure the 'top' metadata node cannot be NULL for lvmetad.
Make obvious vginfo2 cannot be NULL.
Report internal error if handler and vg is undefined.
Check for handle in poll_vg().
Ensure seg is not NULL in dev_manager_transient().
Report missing read_ahead for _lv_read_ahead_single().
Check for report handler in dm_report_object().
Check missing VG in _vgreduce_single().
Addressing somewhat tricky bug here.
Since stdin,stdout,stderr were closed it's been occasionally possible to
see some unexpected messages to be flowing into a clvmd and generating some
randomly sized allocation of many megabytes. Since the message was not
being generated by standard send_message() construction, after some more
testing it apperead to be a debug log message - thus something has flown
to local socket opened on strandard out descriptor.
To fix the issue - use standard file descriptor duplication code for daemons.
For making easier debugging of polling daemon - developer might want to recompile
without modifition of standard file descriptors.
Move the free_vg() to vg.c and replace free_vg with release_vg
and make the _free_vg internal.
Patch is needed for sharing VG in vginfo cache so the release_vg function name
is a better fit here.
may never complete.
If you convert from a linear to a mirror and then convert that
mirror back to linear /while/ the previous (up)convert is
taking place, the mirror polling process will never complete.
This is because the function that polls the mirror for
completion doesn't check if it is still polling a mirror and
the copy_percent that it gets back from the linear device is
certainly never 100%.
The fix is simply to check if the daemon is still looking at
a mirror device - if not, return PROGRESS_CHECK_FAILED.
The user sees the following output from the first (up)convert
if someone else sneaks in and does a down-convert shortly
after their convert:
[root@bp-01 ~]# lvconvert -m1 vg/lv
vg/lv: Converted: 43.4%
ABORTING: Mirror percentage check failed.
