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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.
Save the list of PVs in /run/lvm/hints. These hints
are used to reduce scanning in a number of commands
to only the PVs on the system, or only the PVs in a
requested VG (rather than all devices on the system.)
vgreduce, vgremove and vgcfgrestore were acquiring
the orphan lock in the midst of command processing
instead of at the start of the command. (The orphan
lock moved to being acquired at the start of the
command back when pvcreate/vgcreate/vgextend were
reworked based on pvcreate_each_device.)
vgsplit also needed a small update to avoid reacquiring
a VG lock that it already held (for the new VG name).
The new check_single_lv() function is called prior to the
existing process_single_lv(). If the check function returns 0,
the LV will not be processed.
The check_single_lv function is meant to be a standard method
to validate the combination of specific command + specific LV,
and decide if the combination is allowed. The check_single
function can be used by anything that calls process_each_lv.
As commands are migrated to take advantage of command
definitions, each command definition gets its own entry
point which calls process_each for itself, passing a
pair of check_single/process_single functions which can
be specific to the narrowly defined command def.
The lvm fullreport works per VG and as such, the vg, lv, pv, seg and
pvseg subreport is done for each VG. However, if the PV is not part of
any VG yet, we still want to display pv and pvseg subreports for these
"orphan" PVs - so enable this for lvm fullreport's process_each_vg call.
Pass the single vgname as a new process_each_vg arg
instead of setting a cmd flag to tell process_each_vg
to take only the first vgname arg from argv.
Other commands with different argv formats will be
able to use it this way.
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.
Though vgremove operates per VG by definition, internally, it
actually means iterating over each LV it contains to do the
remove.
So we need to direct selection a bit in this case so that the
selection is done per-VG, not per-LV.
That means, use processing handle with void_handle.internal_report_for_select=0
for the process_each_lv_in_vg that is called later in vgremove_single fn.
We need to disable internal selection for process_each_lv_in_vg
here as selection is already done by process_each_vg which calls
vgremove_single. Otherwise selection would be done per-LV and not
per-VG as we intend!
An intra-release fix for commit 00744b053f.
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).
Remove the checks for vg_read_error() in most of the tools callback
functions and instead make the check in _process_one_vg() more general.
In all but vgcfgbackup, we do not want to proceed if we get any error
from vg_read(). In vgcfgbackup's case, we may proceed if the backup
is to proceed with inconsistent VGs. This is a special case though,
and we mark it with the READ_ALLOW_INCONSISTENT flag passed to
process_each_vg (and subsequently to _process_one_vg).
NOTE: More cleanup is needed in the vg_read_error() path cases.
This patch is a start.
Split vg_remove_single into vg_remove_check (mandatory checks before
vgremove) and vg_remove (do actual remove by committing to disk).
In liblvm, we'd like to provide an consistent API that allows multiple
changes in memory, then let lvm_vg_write() control the commit to disk. In
some cases (for example, lvresize calls fsadm) this may not be possible.
However, since we are using an object model and dividing things into small
operations, the most logical model seems to be the lvm_vg_write model, and
handling the special cases as they arrive. So as best as possible
we move towards this end.
A possible optimization would be to consolidate vg_remove (committing)
code with vgreduce code. A second possible optimization is making vgreduce
of the last device equivalent to vgremove. Today, lvm_vg_reduce fails if
vgreduce is called with the last device, but from an object model perspective
we could view this as equivalent to vgremove and allow it. My gut feel is
we do not want to do this though.
Author: Dave Wysochanski <dwysocha@redhat.com>
Move the vg orphan lock inside vg_remove_single, now a complete liblvm
function. Note that this changes the order of the locks - originally
VG_ORPHAN was obtained first, then the vgname lock. With the current
policy of non-blocking second locks, this could mean we get a failure
obtaining the orphan lock. In the case of a vg with lvs being removed,
this could result in the lvs being removed but not the vg. Such a
scenario could have happened prior though with a different failure.
Other tools were examined for side-effects, and no major problems
were noted.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Move check for active LVs outside of library function. The vgremove
liblvm function function will fail if there are active LVs. It will
be the application's responsibility to check this condition and remove
the LVs individually before calling vgremove. Note also that we've
duplicated the EXPORTED_VG check in vgremove_single (tools) and
vg_remove_single (library). Duplication seemed the only option here
since we don't want to do the automatic removal of LVs (in the tools)
if the vg is exported, and we still need to protect the library call
from removal if the vg is exported.
We still need to deal with the ORPHAN lock but vg_remove_single is now
very close to our liblvm function.
TODO: Refactor lvremove in a similar way.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Remove unneeded LOCK_NONBLOCKING from vg_read() API and tools that
use it. We no longer need this flag anywhere since we now automatically
set LCK_NONBLOCK inside lock_vol() if vgs_locked().
For further details, see:
commit d52b3fd3fe
Author: Dave Wysochanski <dwysocha@redhat.com>
Date: Wed May 13 13:02:52 2009 +0000
Remove NON_BLOCKING lock flag from tools and set a policy to auto-set.
As a simplification to the tools and further liblvm, this patch pushes
the setting of NON_BLOCKING lock flag inside the lock_vol() call.
The policy we set is if any existing VGs are currently locked, we
set the NON_BLOCKING flag.
At some point it may make sense to add this flag back if we get an
RFE from a liblvm user, but for now let's keep it as simple as
possible.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Sun May 3 12:32:30 CEST 2009 Petr Rockai <me@mornfall.net>
* Rework the toollib interface (process_each_*) on top of new vg_read.
Rebased 6/26/09 by Dave W.
- Add skipping message to process_each_lv
- Remove inconsistent_t.
Several commands calls process_each_vg() and in provided
callback it explicitly recovers VG if inconsistent.
(vgchange, vgconvert, vgscan)
It means that old VG is released and reread but the function
above (process_one_vg) tries to unlock and release old VG.
Patch moves the repair logic into _process_one_vg() function.
It always tries to read vg (even inconsistent) and then decides
what to do according new defined parameter.
Also patch unifies inconsistent error messages.
The only slight change if for vgremove command, where
it now tries to repair VG before it removes if force arg is given.
(It works similar way before, just the order of operation changed).
As a simplification to the tools and further liblvm, this patch pushes
the setting of NON_BLOCKING lock flag inside the lock_vol() call.
The policy we set is if any existing VGs are currently locked, we
set the NON_BLOCKING flag.
Should be no functional change.
Fix missing VG unlocks in some pvchange error paths.
Add some missing validation of VG names.
Rename validate_vg_name() to validate_new_vg_name().
Change orphan lock to VG_ORPHANS.
Change format1 to use ORPHAN as orphan VG name.
Fix some memory leaks in error paths found by coverity.
Use C99 struct initialisers.
Move DEFS into configure.h.
Clean-ups to remove miscellaneous compiler warnings.
