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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).
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]
When responding to DM_EVENT_CMD_GET_REGISTERED_DEVICE no longer
ignore threads that have already been unregistered but which
are still present.
This means the caller can unregister a device and poll dmeventd
to ensure the monitoring thread has gone away before removing
the device. If a device was registered and unregistered in quick
succession and then removed, WAITEVENT could run in parallel with
the REMOVE.
Threads are moved to the _thread_registry_unused list when they
are unregistered.
Switch to allocate buffer from heap, since it might be potentially
bigger when extremaly large set of volumes would be monitored.
In case of allocation failure send ENOMEM message.
Also implicitelly ignore msg->size when msg->data is NULL.
When the last entry in the timeout queue is unregistered,
wakeup sleeping condition, so the thread is deleted earlier.
So the thread resource is release earlier.
Also when monitored with tools like valgrind this eliminites reported
leak.
Individual events are handled through separate threads,
so once we have more then a single thread in this eventwait
sleeping, we got race on the dm_log setting, since
if one event is timeout out on alarm, while another is still waiting,
then dm log has been restored to NULL and the next sigalarm
has been reported as error.
Fix it by introducing counter which is protected via mutex,
and only when the last event is released, logging is restored.
TODO: libdm seems to have some static vars which may audit
for this type of use.
The DM_EVENT_GET_PARAMETERS requests the parameters under which
the running dmeventd is run and the it sends them to caller.
The parameters sent:
- the pid of the running dmeventd
- foreground state
- exec_method (currently either "direct" or "systemd")
The exact message sent back:
pid=<pid> daemon=<no/yes> exec_method=<direct/systemd>
Trying to restart dmeventd as a reload action is causing problems
under systemd environment. The systemd loses track of new dmeventd
this way. See also https://bugzilla.redhat.com/show_bug.cgi?id=1060134
for more info.
We need to call dmeventd -R directly instead of "systemctl reload dm-event.service"
that was used before (the reload is aimed at configuration reload anyway,
not stateful restart of the daemon - we did this before just because
there's no ExecRestart in systemd and there's only ExecStart and
ExecStop with which we'd lose the state).
Also, use ExecStart="dmeventd -f" to run dmeventd in foreground
(and let's rely on systemd to daemonize it) and change the
service type from "forking" to "simple".
The PIE and RELRO compiler/linker options can be used to produce a code
some techniques applied that makes the code more immune to some attacks:
- PIE (Position Independent Executable). It can make use of the ASLR
(Address Space Layout Randomization) provided by kernel to avoid
static locations for .text regions of executables (this is the 'pie'
compiler and linker option)
- RELRO (Relocation Read-Only). This prevents overwrite attacks of
the GOT (Global Offset Table) and PLT (Procedure Lookup Table)
used for relocations by making it read-only after all relocations
are resolved (these are the 'relro' and 'now' linker options) -
hence all symbols are resolved at the very start so there's no
need for those tables to be writeable later.
These compiler/linker options are now used by default for daemons
if the compiler/linker supports it.
Failures in the temporary mirror used when up-converting cause dmeventd
to issue 'lvconvert --repair' on the sub-LV, <lv_name>_mimagetmp_?. The
'lvconvert' command refuses to deal with this sub-LV outright - it
expects to be given the name of the top-level LV. So, just like we do
with mirrored logs, we strip-off the portion of the name that is not
the top-level LV and issue the command on the top-level LV instead.
When creating a timeout thread for snapshots, the thread is not
tracked and thus never joined. This means that the exit status
of the timeout thread is held indefinitely. Saves a bit of
memory to set PTHREAD_CREATE_DETACHED when creating this thread.
I've also added pthread_attr_init|destroy to setup the creation
pthread_attr_t.
Reported-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Start separating the validation from the action in the basic lvresize
code moved to the library.
Remove incorrect use of command line error codes from lvresize library
functions. Move errors.h to tools directory to reinforce this,
exporting public versions of the error codes in lvm2cmd.h for dmeventd
plugins to use.
Instead of calling syslog() from signal event handler,
run all logging code in the main loop.
Also it needs to take the lock and check for list
only when really needed.
Switch to use libdm dm_get_status_snapshot() function for
reading status info.
This fixes bug, where the code was using 32bit integers,
while the snapshot target is able to return 64bit sizes.
However this also means, someone is using >1TB snapshot
cow devices, which is actually very bad idea anyway, since the
perfomance and memory usage in this case is very bad.
