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There have been two file locks used to protect lvm
"global state": "ORPHANS" and "GLOBAL".
Commands that used the ORPHAN flock in exclusive mode:
pvcreate, pvremove, vgcreate, vgextend, vgremove,
vgcfgrestore
Commands that used the ORPHAN flock in shared mode:
vgimportclone, pvs, pvscan, pvresize, pvmove,
pvdisplay, pvchange, fullreport
Commands that used the GLOBAL flock in exclusive mode:
pvchange, pvscan, vgimportclone, vgscan
Commands that used the GLOBAL flock in shared mode:
pvscan --cache, pvs
The ORPHAN lock covers the important cases of serializing
the use of orphan PVs. It also partially covers the
reporting of orphan PVs (although not correctly as
explained below.)
The GLOBAL lock doesn't seem to have a clear purpose
(it may have eroded over time.)
Neither lock correctly protects the VG namespace, or
orphan PV properties.
To simplify and correct these issues, the two separate
flocks are combined into the one GLOBAL flock, and this flock
is used from the locking sites that are in place for the
lvmlockd global lock.
The logic behind the lvmlockd (distributed) global lock is
that any command that changes "global state" needs to take
the global lock in ex mode. Global state in lvm is: the list
of VG names, the set of orphan PVs, and any properties of
orphan PVs. Reading this global state can use the global lock
in sh mode to ensure it doesn't change while being reported.
The locking of global state now looks like:
lockd_global()
previously named lockd_gl(), acquires the distributed
global lock through lvmlockd. This is unchanged.
It serializes distributed lvm commands that are changing
global state. This is a no-op when lvmlockd is not in use.
lockf_global()
acquires an flock on a local file. It serializes local lvm
commands that are changing global state.
lock_global()
first calls lockf_global() to acquire the local flock for
global state, and if this succeeds, it calls lockd_global()
to acquire the distributed lock for global state.
Replace instances of lockd_gl() with lock_global(), so that the
existing sites for lvmlockd global state locking are now also
used for local file locking of global state. Remove the previous
file locking calls lock_vol(GLOBAL) and lock_vol(ORPHAN).
The following commands which change global state are now
serialized with the exclusive global flock:
pvchange (of orphan), pvresize (of orphan), pvcreate, pvremove,
vgcreate, vgextend, vgremove, vgreduce, vgrename,
vgcfgrestore, vgimportclone, vgmerge, vgsplit
Commands that use a shared flock to read global state (and will
be serialized against the prior list) are those that use
process_each functions that are based on processing a list of
all VG names, or all PVs. The list of all VGs or all PVs is
global state and the shared lock prevents those lists from
changing while the command is processing them.
The ORPHAN lock previously attempted to produce an accurate
listing of orphan PVs, but it was only acquired at the end of
the command during the fake vg_read of the fake orphan vg.
This is not when orphan PVs were determined; they were
determined by elimination beforehand by processing all real
VGs, and subtracting the PVs in the real VGs from the list
of all PVs that had been identified during the initial scan.
This is fixed by holding the single global lock in shared mode
while processing all VGs to determine the list of orphan PVs.
When lvextend extends an LV that is active with a shared
lock, use this as a signal that other hosts may also have
the LV active, with gfs2 mounted, and should have the LV
refreshed to reflect the new size. Use the libdlmcontrol
run api, which uses dlm_controld/corosync to run an
lvchange --refresh command on other cluster nodes.
If there are two independent scripts doing:
vgchange --lockstart vg
lvchange -ay vg/lv
The first vgchange to do the lockstart will wait for
the lockstart to complete before returning.
The second vgchange to do the lockstart will see that
the start is already in progress (from the first) and
will do nothing. This means the second does not wait
for any lockstart to complete, and moves on to the
lvchange which may find the lockspace still starting
and fail.
To fix this, make the vgchange lockstart command
wait for any lockstart's in progress to complete.
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
If 'vgcreate --shared' finds both sanlock and dlm are running,
print a more accurate error message:
"Found multiple lock managers, select one with --lock-type."
When neither is running, we still print:
"Failed to detect a running lock manager to select lock type."
Add a new arg to lockd_start_vg() that indicates
it is being called for a new lockd VG, so that
lvmlockd knows the lockspace being started is new.
(Will be used by a following commit.)
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.
Remove the existing lock type using the same functions
used to remove the lockd components during vgremove.
This results in a "clean" VG and lvmlockd state after
the vgchange, i.e. no bits left over from previous
lock type.
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.
When lvm is built without lvmlockd support, vgcreate using a
shared lock type would succeed and create a local VG (the
--shared option was effectively ignored). Make it fail.
Fix the same issue when using vgchange to change a VG to a
shared lock type.
Make the error messages consistent.
