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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 two reasons for this: first, this allows the client side to notice
that some PV has multiple devices associated with it and print appropriate
warnings. Second, if a duplicate device pops up and disappears, after this
change the original connection between the PV and device is not lost.
Free (and clear) h.protocol string on daemon_open() error paths
so it's OK for caller to skip calling daemon_close() if returned
h.socket_fd is -1.
Close h.socket_fd in daemon_close() to avoid possible leak.
https://bugzilla.redhat.com/1164234
"%d" in buffer_append_vf is 64 bit wide. Using just `int` for the
variable will fetch more from va_list than intended and shifting
remaining arguments resulting in errors like:
Internal error: Bad format string at '#orphan'
In cases where PV appears on a new device without disappearing from an old one
first, the device->pvid pointers could become ambiguous. This could cause the
ambiguous PV to be lost from the cache when a different PV comes up on one of
the ambiguous devices.
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.
Make it easier to run a live lvmetad in debugging mode and
to avoid conflicts if multiple test instances need to be run
alongside a live one.
No longer require -s when -f is used: use built-in default.
Add -p to lvmetad to specify the pid file.
No longer disable pidfile if -f used to run in foreground.
If specified socket file appears to be genuine but stale, remove it
before use.
On error, only remove lvmetad socket file if created by the same
process. (Previous code removes socket even while a running instance
is using it!)
If using lv/vgchange --sysinit -aay and lvmetad is enabled, we'd like to
avoid the direct activation and rely on autoactivation instead so
it fits system initialization scripts.
But if we're calling lv/vgchange --sysinit -aay too early when even
lvmetad service is not started yet, we just need to do the direct
activation instead without printing any error messages (while
trying to connect to lvmetad and not finding its socket).
This patch adds two helper functions - "lvmetad_socket_present" and
"lvmetad_used" which can be used to check for this condition properly
and avoid these lvmetad connections when the socket is not present
(and hence lvmetad is not yet running).
The idea is to avoid a period when an existing VG is not mapped to either the
old or the new name. (Note that the brief "blackout" was present even if the
name did not actually change.) We instead allow a brief overlap of a VG existing
under both names, i.e. a query for a VG might succeed but before a lock is
acquired the VG disappears.
This reverts commit ed23da95b6.
Hash table device_to_pvid seems to contain references to
already deleted pvids and so revert to the older
behaviour using allocated memory.
All operations on shared hash tables need to be protected by mutexes. Moreover,
lookup and subsequent key removal need to happen atomically, to avoid races (and
possible double free-ing) between multiple threads trying to manipulate the same
VG.
If we fail to get memory for mutex, hash the mutex
or fail somewhere along pthread function calls
return allocated resources back and unlock vg_lock_map mutex.
Since we are doing just dump and function doesn't report
any error, explicitely ignore return values from
dm_config_write_node and dm_asprintf.
Same applies for the logging function.
Try to bring the lvmetad usage text and man page closer to the code.
There seem to be 3 useful ways to use -d with lvmetad at the moment:
-d all
-d wire
-d debug
(They can also be comma-separated like -d wire,debug.)
Prior to the last release, -d, -dd and -ddd were supported.
Fail if an unrecognised debug arg is supplied on the command line.
Change -V to report the same version as the lvm binary: previously it
just reported version 0.
- move common dm_config_tree manipulation functions from lvmetad-core to
daemon-shared
- add config-tree-based request manipulation APIs to daemon-client
- factor out _v (va_list) variants of most variadic functions in libdaemon
If we were defining a section (which is a node without a value) and
the value was created automatically on dm_config_create_node call,
we were wasting resources as the next step after creating the config
node itself was assigning NULL for the node's value.
The dm_config_node_create + dm_config_create_value sequence should be
used instead for settings and dm_config_node_create alone for sections.
The majority of the code already used the correct sequence. Though
with dm_config_node_create fn creating the value as well, the pool
memory was being trashed this way.
This patch removes the node value initialization on dm_config_create_node
fn call and keeps it for the direct dm_config_create_value fn call.
- logging is not controlled by "levels" but by "types"; types are
independent of each other... implementation of the usual "log level"
user-level semantics can be simply done on top; the immediate
application is enabling/disabling wire traffic logging independently
of other debug data, since the former is rather bulky and can easily
obscure almost everything else
- all logs go to "outlets", of which we currently have 2: syslog and
stderr; which "types" go to which "outlets" is entirely configurable
There were several hard-coded values for run directory around the code.
Also, some tools are DM specific only, others are LVM specific and there
was no distinction made here before. With this patch applied, we have
this cleaned up a bit (subsystem in brackets, defaults in parentheses):
[common] configurable PID_DIR (/var/run)
lvm [lvm] configurable RUN_DIR (/var/run/lvm)
configurable locking dir (/var/lock/lvm)
clvmd [lvm] configurable pid file (PID_DIR/clvmd.pid)
socket (RUN_DIR/clvmd.sock)
lvmetad [lvm] configurable pid file (PID_DIR/lvmetad.pid)
socket (RUN_DIR/lvmetad.socket)
dm [dm] configurable DM_RUN_DIR (/var/run)
cmirrord [dm] configurable pid file (PID_DIR/cmirrord.pid)
dmeventd [dm] configurable pid file (PID_DIR/dmeventd.pid)
server fifo (DM_RUN_DIR/dmeventd-server)
client fifo (DM_RUN_DIR/dmeventd-client)
The changes briefly:
- added configure --with-default-pid-dir
- added configure --with-default-dm-run-dir
- added configure --with-lvmetad-pidfile
- by default, using one common pid directory for everything
(only lvmetad was not following this before)
Add 3rd daemon return state "unknown" for lookups that are carried out
successfully but don't find the item requested.
Avoid issuing error messages when it's expected that a device that's
being looked up in lvmetad might not be there.
Code cannot proceed if oldname would be NULL.
Since lvmetad currently doesn't use logging mechanism of lvm to report
internal errors - stay with current code style of lvmetad which uses
plain asserts for cases like this.
