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Previously, a command sent lvmetad new VG metadata in vg_commit().
In vg_commit(), devices are suspended, so any memory allocation
done by the command while sending to lvmetad, or by lvmetad while
updating its cache could deadlock if memory reclaim was triggered.
Now lvmetad is updated in unlock_vg(), after devices are resumed.
The new method for updating VG metadata in lvmetad is in two phases:
1. In vg_write(), before devices are suspended, the command sends
lvmetad a short message ("set_vg_info") telling it what the new
VG seqno will be. lvmetad sees that the seqno is newer than
the seqno of its cached VG, so it sets the INVALID flag for the
cached VG. If sending the message to lvmetad fails, the command
fails before the metadata is committed and the change is not made.
If sending the message succeeds, vg_commit() is called.
2. In unlock_vg(), after devices are resumed, the command sends
lvmetad the standard vg_update message with the new metadata.
lvmetad sees that the seqno in the new metadata matches the
seqno it saved from set_vg_info, and knows it has the latest
copy, so it clears the INVALID flag for the cached VG.
If a command fails between 1 and 2 (after committing the VG on disk,
but before sending lvmetad the new metadata), the cached VG retains
the INVALID flag in lvmetad. A subsequent command will read the
cached VG from lvmetad, see the INVALID flag, ignore the cached
copy, read the VG from disk instead, update the lvmetad copy
with the latest copy from disk, (this clears the INVALID flag
in lvmetad), and use the correct VG metadata for the command.
(This INVALID mechanism already existed for use by lvmlockd.)
Reconnect to lvmetad if either the send fails (e.g. lvmetad
was restarted since lvmlockd last connected), or if no
lvmetad connection exists (e.g. lvmetad was started after
lvmlockd so no previous connection existed.)
Previously, vgcfgrestore would attempt to vg_remove the
existing VG from lvmetad and then vg_update to add the
restored VG. But, if there was a failure in the command
or with vg_update, the lvmetad cache would be left incorrect.
Now, disable lvmetad before the restore begins, and then
rescan to populate lvmetad from disk after restore has
written the new VG to disk.
We were initially looking to see if an LV was hidden and if it was we were
creating an instance of a LvCommon object to represent it. Thus if we
had a hidden cache pool for example we were missing the methods and
properties for the cache pool. However, when we create the object path,
any hidden LVs, regardless of type/functionality will be placed in the
hidden path.
The object manager method get_object_by_lvm_id was used in many cases for
the sole reason of getting the object path for the object. Instead of
retrieving the object and then calling 'dbus_object_path' on the object, we
are adding a method which returns the object path.
When we are processing the LVs we need to build up dbus objects from least
dependent to most dependent, so that we have information available when
constructing.
If a command gets stuck during an lvmetad update, lvmetad
will cancel that update after the timeout. The next command
to check the lvmetad will see that lvmetad needs to be
populated because lvmetad will return token of "none" after
a timed out update (same as when lvmetad is not populated
at all after starting.)
If a command gets an error during an lvmetad update, it
will now just quit and leave its updating token in place.
That update will be cancelled after the timeout.
All the variables for sscanf in lvmlockctl.c and lvmlockd-sanlock.c are
zeroed before sscanf call so the failure is detected by seeing the zero
value instead of proper one in subsequent code - so use (void) for
sscanf calls to ignore return value here.
If a command begins repopulating the lvmetad cache,
and fails part way through, it should set the disabled
state in lvmetad so other commands don't use bad data.
If a subsequent scan succeeds, the disabled state is
cleared.
When duplicate PVs are detected, set the disabled
flag so that commands will disable use of lvmetad.
This duplicate detection is done by lvmetad itself
when it's told about a single new PV with a PVID
that matches an existing PV on another device.
(This is different from the case where the command
is scanning all devices and detects the duplicate.)
Remove the "altdev" logic that attempted to keep
track of multiple devices for a single PV. It
is no longer used since lvmetad is disabled in
this case.
A global flag in lvmetad indicates it has been disabled.
Other flags indicate the reason it was disabled.
These flags can be queried using get_global_info.
The lvmetactl debugging utility can set and clear the
disabled flag in lvmetad. Nothing else sets the
disabled flag yet.
Commands will check these flags after connecting to
lvmetad. If the disabled flag is set, the command
will not use the lvmetad cache, but revert to disk
scanning.
To test this feature:
$ lvmetactl get_global_info
response = "OK"
global_invalid = 0
global_disable = 0
disable_reason = "none"
token = "filter:3041577944"
$ vgs
(should report VGs from lvmetad)
$ lvmetactl set_global_disable 1
$ lvmetactl get_global_info
response = "OK"
global_invalid = 0
global_disable = 1
disable_reason = "DIRECT"
token = "filter:3041577944"
$ vgs
WARNING: Not using lvmetad because the disable flag was set directly.
(should report VGs without contacting lvmetad)
$ lvmetactl set_global_disable 0
$ vgs
(should report VGs from lvmetad)
Move checking the lvmetad state, and the possible rescan,
out of lvmetad_send() to the start of the command.
Previously, the token mismatch and rescan would occur
within lvmetad_send() for some other request. Now,
the token mismatch is detected earlier, so the
rescan can be done before the main command is in
progress. Rescanning deep within the processing of
another command will disturb the lvmcache state of
that other command.
A rescan already exists at the start of the command
for the case where foreign VGs are going to be read.
This same rescan is now also performed when there is
an lvmetad token mismatch (from a changed global_filter).
The commands pvscan/vgscan/lvscan/vgimport are excluded
from this preemptive checking/rescanning for lvmetad
because they want to do rescanning themselves explicitly.
If rescanning devices fails, then lvmetad has not been
correctly repopulated and should not be used, so make
the command revert to not using lvmetad.
To help out with debug, when an exception is thrown in the dbus service we
will dump all the information we have on the last 16 commands that were
executed along with the stack strace.
Signed-off-by: Tony Asleson <tasleson@redhat.com>
While running on F24 a number of warnings were being emitted from using the
deprecated GObject instead of GLib. Tested on python 3.4 and 3.5.
Signed-off-by: Tony Asleson <tasleson@redhat.com>
Python 3.5 in F24 was throwing the following exception:
Traceback (most recent call last):
File "/usr/lib/python3.5/site-packages/lvmdbusd/main.py", line 73, in process_request
req.run_cmd()
File "/usr/lib/python3.5/site-packages/lvmdbusd/request.py", line 73, in run_cmd
self.register_error(-1, st)
File "/usr/lib/python3.5/site-packages/lvmdbusd/request.py", line 123, in register_error
self._reg_ending(None, error_rc, error)
File "/usr/lib/python3.5/site-packages/lvmdbusd/request.py", line 115, in _reg_ending
self.cb_error(self._rc_error)
File "/usr/lib64/python3.5/site-packages/dbus/service.py", line 669, in <lambda>
keywords[error_callback] = lambda exception: _method_reply_error(connection, message, exception)
File "/usr/lib64/python3.5/site-packages/dbus/service.py", line 293, in _method_reply_error
exception))
File "/usr/lib64/python3.5/traceback.py", line 136, in format_exception_only
return list(TracebackException(etype, value, None).format_exception_only())
File "/usr/lib64/python3.5/traceback.py", line 442, in __init__
if (exc_value and exc_value.__cause__ is not None
AttributeError: 'str' object has no attribute '__cause__'
This was caused because we were calling the dbus error callback with a
string instead of an actual exception. On python 3.4 this was apparently
OK, but not with 3.5. Corrected to pass the exception to error callback.
Change tested on both python 3.4 and 3.5.
Reported-by: Vratislav Podzimek <vpodzime@redhat.com>
Signed-off-by: Tony Asleson <tasleson@redhat.com>
When we use udev or have lvm call back into the dbus service when a
change occurs, even if that change originated from the dbus service
we end up refreshing the state of the system twice which is not
needed or wanted. This change handles this case by removing any
pending refreshes in the worker queue if the state of the system
was just updated.
Signed-off-by: Tony Asleson <tasleson@redhat.com>
Use #define instead, since we do not require actually buffer needs
to exists to eliminated new gcc6 warning:
clvm.h:53:19: warning: ‘CLVMD_SOCKNAME’ defined but not used
[-Wunused-const-variable]
export LVMDBUSD_SESSION=True to run on the session bus instead
of the system bus so that we can run the unit test without
installing the dbus conf file.
Signed-off-by: Tony Asleson <tasleson@redhat.com>
It appears that the output of lvconvert --merge can vary some. The code
was blowing up as it was trying to parse a line of stdout to retrieve the
% complete, but the line did not have the needed format and an execption
was thrown. The uncaught exception caused the background thread to exit
without updating the job object, which caused the client to hang forever
waiting. Added a default exception handler to prevent unhandled execptions
causing hangs and removed the parameter skip_first_line as it's no longer
needed. The code checks to see if the line can be parsed before doing so.
Signed-off-by: Tony Asleson <tasleson@redhat.com>
After the lockspace has been successfully removed,
invalidate the name field in the lockspace struct.
The struct remains on the list of lockspaces until
the struct can be freed later. Until the struct is
freed, its name will prevent another new lockspace
from being created with the same name.
Since commit 2fc126b00d, the library
code requires udev to be initialised for device scanning and
clvmd can fail to find VGs if devices/external_device_info_source
is set to "udev".
Make the lvb validation rules for convert match
those for unlock (even though it would be very
unlikely or impossible for convert to deal with
zero lvb.)
Have commands send lvmlockd the update message
in vg_write instead of vg_commit, so that it's
not done while LVs are suspended. If the vg_write
is not committed, and the seqno sent to lvmlockd
is not used, then lvmlockd can detect this when
the next update uses the same seqno.
Use process_each_vg() to lock and read the old VG,
and then call the main vgrename code.
When real VG names are used (not a UUID in place of the
old name), the command still pre-locks the new name
(when strcmp wants it locked first), before calling
process_each_vg on the old name.
In the case where the old name is replaced with a UUID,
process_each_vg now translates that UUID into the real
VG name, which it locks and reads. In this case, we
cannot do pre-locking to maintain lock ordering because
the old name is unknown. So, in this case the strcmp
based lock ordering is suppressed and the old name is
always locked first. This opens a remote chance for
lock ordering conflict between racing vgrenames between
two names where one or both commands use the UUID.
If an existing fifo has the wrong attributes it cannot be trusted
so we must unlink it and recreate it correctly.
(Replaces 2c8d6f5c90: if the other end of
the fifo already got opened while its mode was insecure, delaying the
chmod isn't going to make any difference!)
Reinstate and extend checks removed by e1b111b02a.
The code has always assumed that only root has access to the directory
containing the fifos and that they are under the complete control of
dmeventd code. If anything is found not to be as expected, then open()
should certainly not be attempted!
In lookup, return a count of entries with the
same key rather than the value from a second
entry with the same key.
Using some slightly different names.
Simply use lookup_withval right away rather than doing a
standard lookup, checking for the wrong mapping, then
repeating with lookup_withval to get the right mapping.
If the data len is passed into the hash table
and saved there, then the hash table internals
do not need to assume that the data value is
a string at any point.
New hash table functions are added that allow for
multiple entries with the same key. Use of the
vgname_to_vgid hash table is converted to these
new functions since there are multiple entries
in vgname_to_vgid that have the same key (vgname).
When multiple VGs with the same name exist, commands
that reference only a VG name will fail saying the
VG could not be found (that error message could be
improved.) Any command that works with the select
option can access one of the VGs with -S vg_uuid=X.
vgrename is a special case that allows the first VG
name arg to be replaced by a uuid, which also works.
(The existing hash table implementation is not well
suited for handling this case, but it works ok with
the new extensions. Changing lvmetad to use its own
custom hash tables may be preferable at some point.)
Recent change 2c8d6f5c90
actually droped restart when the reason of failing open is missing
device completely - check for ENOENT now as another reason
to start new dmeventd server (when there is no systemd to maintain it).
While through all codepaths we never 'read' lock_id unless LCKF_CONVERT,
coverity cannot decrypt this.
As since it's usually better to pass in 'well-defined' data structures
preset lock_id to 0.
Use fputs() when printing plain string,
easier then fprintf which needs to parse it.
Also check fd before close is >= 0 -
it is - but coverity fail to see it, so eliminate
this false-positive warning.
Check for arg_vgid_lookup and arg_name_lookup not being NULL.
Drop checking arg_vgid and arg_name for NULL since they
are already dereference earlier - thus mostly must be NOT NULL.
(If that would be possible larger rework of this function would be
required).
Put calls related to fifo opening into a single function.
Fix Time-Of-Check-Time-Of-Use and use fstat()
and fchmod() on already opened fd instead of
checking first path and then risking to open something
different.
update_metadata and pv_found update the cached metadata;
these are both reworked to improve the code, organize it
by each possible state and transition, make it much more
clear what's changing, add more error checking and
handling, and add comments.
The state and content of the cache (hash tables) does not
change (apart from some things that didn't work before),
and the communication to/from commands does not change.
The implementation and organization of the code making
the state changes does change significantly.
One detail related to the content of the cache does change:
different hash tables do not reference the same memory any more;
the target values in each hash table are allocated and freed
individually.
If plugin's lvm command execution fails too often (>10 times),
there is no point to torture system more then necessary, just log
and drop monitoring in this case.
Improve event string parser to avoid unneeded alloc+free.
Daemon talk function uses '-' to mark NULL/missing field.
So restore the NULL pointer back on parser.
This should have made old tools like 'dmevent_tool' work again.
As now 'uuid' or 'dso' could become NULL and then be
properly used in _want_registered_device() function.
Since lvm2 always fill these parameters, this change should
have no effect on lvm2.
Older pthread library was missing 'trick'
in pthread_cleanup_pop() which lead to
compilation error:
error: label at end of compound statement
Use explicit ';' to fix it.
Implementing exit when 'dmeventd' is idle.
Default idle timeout set to 1 hour - after this time period
dmeventd will cleanly exit.
On systems with 'systemd' - service is automatically started with
next contact on dmeventd communication socket/fifo.
On other systems - new dmeventd starts again when lvm2 command detects
its missing and monitoring is needed.
Add support to unmonitor device when monitor recognizes there is
nothing to monitor anymore.
TODO: possibly API change with return value could be also used.
Redesign threading code:
- plugin registration runs within its new created thread for
improved parallel usage.
- wait task is created just once and used during whole plugin lifetime.
- event thread is based over 'events' filter being set - when
filter is 0, such thread is 'unused'.
- event loop is simplified.
- timeout thread is never signaling 'processing' thread.
- pending of events filter cnange is properly reported and
running event thread is signalled when possible.
- helgrind is not reporting problems.
Need here to keep control device opened while there is 'any' dso
plugin loaded - otherwise there would a race closing controlfd
inside lvm2 plugin while some other monitoring thread would
tried to execute another WAITEVENT task.
Move all DSO related function in front, so they could be easily
referenced from rest of code.
Add proper error paths with logging and error reporting.
Drop mutex locking when releasing DSO - since DSO is always
allocated and released in main 'event' processing thread.
If a host failed while holding a sanlock lease,
sanlock_acquire will by default block and wait
for the lease to expire before returning. We
want it to return with an error so we can retry
instead of blocking, which allows us to process
other lock operations.
(Enclose this in an ifdef until the new flag
appears in a sanlock release.)
Respect lvm2_log_fn prototype. The idea of 'reusing' print_log with
plain cast is causing very strange crashes with some older 'gcc' compilers.
So just do it cleanly...
Rework thread creation code to better use resources.
New code will not leak 'timeout' registered thread on error path.
Also if the thread already exist - avoid creation of thread
object and it's later destruction.
If the race is noticed during adding new monitoring thread,
such thread is put on cleanup list and -EEXIST is reported.
As we now use 'unified' logging macro system - we no longer need
to protect from change of logging function pointer - it's set
once at the start of dmeventd and not change anymore
(as lvm2 library no longer interferers here).
If lvmlockd acquires an lv lock for a command, but the
command exits before the reply, then the command has
not activated the lv and lvmlockd should unlock it.
This only applies when the lv was not already locked.
(There will always be a chance that the lv lock is held
while the lv is not active, i.e. if the command fails in
the small window between getting the lv lock and before
doing the activation. In that case, rerunning the
activation command corrects the inconsistency.)
This commit helps by automatically clearing the
inconsistency (lv locked by not activated) in the most
common case when the lv lock operation is slow to
complete and the command is canceled by the user.
This commit also adds and cleans up references to the
client id in a bunch of log messages, which is useful
to follow processing on each independent lock request.
This applies the same rule/logic to dlm VGs that has always
existed for sanlock VGs. Allowing a dlm VG to be removed
while its lockspace was still running on other hosts largely
worked, but there were difficult problems if another VG with
the same name was recreated. Forcing the VG lockspace to
be stopped, gives both sanlock and dlm VGs the same behavior.
This shortcut was added for an odd case that I do not
believe is relevant any more. Having an alternate
path for lockspace thread cleanup is a complication
that could lead to problems.
The dlm will often lose the lvb content, so we need to
check quite a few possibilities for lvb values that
were not being checked before.
Refactoring was required to pass the entire lvb value
back to the core code instead of the single value.
The only functional change should be detecting new
lvb states where metadata is now invalidated where
it wasn't before.
When an action is created by lvmlockd for itself,
there is no client to send the result to. Add
the NO_CLIENT flag to the action to skip sending
the result to a client.
Undo the part of the recent EREMOVED change which
automatically stopped the lockspace for a remotely
removed VG. It didn't always work (would not work
when lvb content was rebuilt in the dlm). This will
be handled better when the lvb content is controlled
more strictly.
Remove the optimization/shortcut for starting the dlm global
lockspace when it was already running.
Reenable automatically starting the dlm global lockspace
when a command attempts to use it and it's not yet started.
This had become disabled at some point.
Previously all stderr messages issued by spawned lvpoll command were reported
as INFO only. This made all such messages invisible in syslog or lvmpolld log
while running default configuration.
All lvpoll stderr messages are loged with WARN priority now and lvpoll
command exiting with retcode != 0 is logged with ERROR priority in
syslog and lvmpolld log
Include both the VG uuid and name in the lvmetad
set_vg_info message. This works around an obscure
problem where the VG uuid in lvmlockd is wrong
when one host removes a dlm VG, then creates a new
VG with the same name. If the dlm lockspace for
the initial VG was never stopped on another host,
that other host will be using the old uuid in its
lvmetad set_vg_info message. (That can be
corrected with a larger change, but this is an
effective workaround.)
set_vg_info previously accepted only vg uuid,
now accept both vg uuid and vg name. If the
uuid is provided, it's used just as before,
but if the uuid is not provided, or if it's
not found, then fall back to using the vg
name if that is provided.
lvmlockd would fail to recognize that the global lockspace
failed to start if the dlm wasn't running, so future attempts
to start the dlm global lockspace would do nothing, thinking
it was already running.
This was only used to return two flags indicating specific
reasons for a lock failure so that a more specific error
message could be printed by the command (lockspace had been
stopped, or lockspace had an error starting.)
Remove the list, given its limited usefulness, the fact it
would easily become inaccurate, and the fact it was causing
misleading error messages. The error conditions it was meant
to help could be reported differently.
This makes lvmlockd removal steps for dlm VGs closely match
sanlock VGs. Because dlm lockspaces are not required to be
stopped on all hosts before vgremove, there is an extra bit
for dlm lockspaces, where a flag is set in the VG lock lvb
indicating that the VG was removed. If other hosts happen
to use the VG lock they will see this flag and stop their
lockspace.
Single messages sent over unix sockets are limited in
size to /proc/sys/net/core/wmem_max, so send the 1MB
debug buffer in smaller chunks to avoid EMSGSIZE.
Also look for EAGAIN and retry sending for a limited
time when the reader is slower than the writer.
Also shift the location of that code so it's the same
as other requests.
With clusters larger than 3 nodes, the 32-byte debug buffer in
cpg_join_callback() is too small to contain all the node IDs, because
32-bit identifiers are generally rendered in 10 decimal digits. No fixed
size is good in all cases, but this is conditionally logged debug info,
so we can simply truncate it. Double the size, nevertheless.
The check for other sanlock lockspaces was not checking
that the lockspace type was sanlock, so if dlm lockspaces
were visible, they were wrongly included.
This adds the infrastructure, code paths, error reporting,
etc. to handle storage errors, or storage loss, under the
sanlock leases in a VG that is being used. The loss of
storage means sanlock cannot renew its leases, which means
that the host needs to stop using the shared VG before its
leases expire.
This still requires manually shutting down a VG that has
lost lease storage, e.g. unmounting file systems,
deactivating LVs in the VG. The next step is to
automatically use a command like blkdeactivate to do that.
/lib/log/log.c:88: warning[invalidScanfArgType_int]: %llu in format string (no. 2) requires 'unsigned long long *' but the argument type is 'long long *'.
daemons/lvmlockd/lvmlockd-core.c:791: error[uninitstring]: Dangerous usage of 'version' (strncpy doesn't always null-terminate it).
The dlm global lockspace is automatically added when the
first dlm VG lockspace is added. Reverse this by removing
the dlm global lockspace after the last dlm VG lockspace
is removed. (Remove old non-working code that did this
based on an old command that could explicitly add/remove
the dlm global lockspace.)
Make it possible to decide whether we want to initialize connections and
filters together with toolcontext creation.
Add "filters" and "connections" fields to struct
cmd_context_initialized_parts and set these in cmd_context.initialized
instance accordingly.
(For now, all create_toolcontext calls do initialize connections and
filters, we'll change that in subsequent patch appropriately.)
Add struct cmd_context_initialized_parts to wrap up information
about which cmd context pieces are initialized and add variable
of this struct type into struct cmd_context.
Also, move existing "config_initialized" variable that was directly
part of cmd_context into the new cmd_context.initialized wrapper.
We'll be adding more items into the struct cmd_context_initialized_parts
with subsequent patches...
This tries harder to avoid creating duplicate global locks in
sanlock VGs by refusing to create a new sanlock VG with a
global lock if other sanlock VGs exist that may have a gl.
Simply running concurrent copies of 'pvscan | true' is enough to make
clvmd freeze: pvscan exits on the EPIPE without first releasing the
global lock.
clvmd notices the client disappear but because the cleanup code that
releases the locks is triggered from within some processing after the
next select() returns, and that processing can 'break' after doing just
one action, it sometimes never releases the locks to other clients.
Move the cleanup code before the select.
Check all fds after select().
Improve some debug messages and warn in the unlikely event that
select() capacity could soon be exceeded.
When there are duplicate global locks, check if the gl
is still enabled each time a gl or vg lock is acquired
in the lockspace. Once one of the duplicates is disabled,
then other hosts will recognize that the issue is resolved
without needing to restart the lockspaces.
When lvmlockd is compiled without support for one of the
lock managers (sanlock or dlm), and a command tries to use
one of them, explain that in the error message.
lib/format1/import-export.c:167: var_deref_op: Dereferencing null pointer "vg->lvm1_system_id"
lib/cache/lvmetad.c:1023: var_deref_op: Dereferencing null pointer "this"
daemons/lvmlockd/lvmlockd-core.c:2659: check_after_deref: Null-checking "act" suggests that it may be null, but it has already been dereferenced on all paths leading to the check
/daemons/lvmetad/lvmetad-core.c:1024: check_after_deref: Null-checking "pvmeta" suggests that it may be null, but it has already been dereferenced on all paths leading to the check
... Using uninitialized value "lockd_state" when calling "lockd_vg"
(even though lockd_vg assigns 0 to the lockd_state, but it looks at
previous state of lockd_state just before that so we need to have
that properly initialized!)
libdm/libdm-report.c:2934: uninit_use_in_call: Using uninitialized value "tm". Field "tm.tm_gmtoff" is uninitialized when calling "_get_final_time".
daemons/lvmlockd/lvmlockctl.c:273: uninit_use_in_call: Using uninitialized element of array "r_name" when calling "format_info_r_action". (just added FIXME as this looks unfinished?)
lib/log/log.c:115: leaked_storage: Variable "st" going out of scope leaks the storage it points to
daemons/lvmpolld/lvmpolld-core.c:573: leaked_storage: Variable "cmdargv" going out of scope leaks the storage it points to
daemons/lvmlockd/lvmlockd-core.c:5341: leaked_handle: Handle variable "fd" going out of scope leaks the handle
daemons/lvmlockd/lvmlockctl.c:575: overwrite_var: Overwriting "able_vg_name" in "able_vg_name = strdup(optarg)" leaks the storage that "able_vg_name" points to
daemons/lvmlockd/lvmlockctl.c:571: overwrite_var: Overwriting "able_vg_name" in "able_vg_name = strdup(optarg)" leaks the storage that "able_vg_name" points to
daemons/lvmlockd/lvmlockctl.c:385: leaked_handle: Handle variable "s" going out of scope leaks the handle
if lvm2 is built with debug memory options dm_free() is not
mapped directly to std library's free(). This may cause memory corruption
as a line buffer may get reallocated in getline with realloc.
This is a temporary hotfix. Other debug memory failure needs to
be investigated and explained.
Add the ability to invalidate global or individual VG metadata.
The invalid state is returned to lvm commands along with the metadata.
This allows lvm commands to detect stale metadata from the cache and
reread the latest metadata from disk (in a subsequent patch.)
These changes do not change the protocol or compatibility between
lvm commands and lvmetad.
Global information
------------------
Global information refers to metadata that is not isolated
to a single VG , e.g. the list of vg names, or the list of pvs.
When an external system, e.g. a locking system, detects that global
information has been changed from another host (e.g. a new vg has been
created) it sends lvmetad the message: set_global_info: global_invalid=1.
lvmetad sets the global invalid flag to indicate that its cached data is
stale.
When lvm commands request information from lvmetad, lvmetad returns the
cached information, along with an additional top-level config node called
"global_invalid". This new info tells the lvm command that the cached
information is stale.
When an lvm command sees global_invalid from lvmated, it knows it should
rescan devices and update lvmetad with the latest information. When this
is complete, it sends lvmetad the message: set_global_info:
global_invalid=0, and lvmetad clears the global invalid flag. Further lvm
commands will use the lvmetad cache until it is invalidated again.
The most common commands that cause global invalidation are vgcreate and
vgextend. These are uncommon compared to commands that report global
information, e.g. vgs. So, the percentage of lvmetad replies containing
global_invalid should be very small.
VG information
--------------
VG information refers to metadata that is isolated to a single VG,
e.g. an LV or the size of an LV.
When an external system determines that VG information has been changed
from another host (e.g. an lvcreate or lvresize), it sends lvmetad the
message: set_vg_info: uuid=X version=N. X is the VG uuid, and N is the
latest VG seqno that was written. lvmetad checks the seqno of its cached
VG, and if the version from the message is newer, it sets an invalid flag
for the cached VG. The invalid flag, along with the newer seqno are saved
in a new vg_info struct.
When lvm commands request VG metadata from lvmetad, lvmetad includes the
invalid flag along with the VG metadata. The lvm command checks for this
flag, and rereads the VG from disk if set. The VG read from disk is sent
to lvmetad. lvmetad sees that the seqno in the new version matches the
seqno from the last set_vg_info message, and clears the vg invalid flag.
Further lvm commands will use the VG metadata from lvmetad until it is
next invalidated.
There are reports of unexplained ioctl failures when using dmeventd.
An explanation might be that the wrong value of errno is being used.
Change libdevmapper to store an errno set by from dm ioctl() directly
and provide it to the caller through a new dm_task_get_errno() function.
[Replaced f9510548667754d9209b232348ccd2d806c0f1d8]
