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When a PV is stacked on an LV, the LV will be kept in
bcache, and the open fd on the LV may interfere with
processing the LV. So, drop/close a bcache fd for
an LV before processing the LV.
Create a new dev->bcache_fd that the scanning code owns
and is in charge of opening/closing. This prevents other
parts of lvm code (which do various open/close) from
interfering with the bcache fd. A number of dev_open
and dev_close are removed from the reading path since
the read path now uses the bcache.
With that in place, open(O_EXCL) for pvcreate/pvremove
can then be fixed. That wouldn't work previously because
of other open fds.
In the same way as the other process_each functions.
In the common case all the info that's needed can be
used from lvmcache after a label scan. But this means
that unchosen devs for duplicate PVs need to be handled
explicitly.
The copy of VG metadata stored in lvmcache was not being used
in general. It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation. There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.
This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.
This is a way of passing the VG from suspend to resume in
clvmd. Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.) The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo. These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd. The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.
suspend has both old (current) and new (precommitted)
copies of the VG metadata. It stashes both of these in
the vginfo prior to suspending devices. When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.
resume grabs the VG stashed by suspend. If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG. The VG is then used to resume
LVs.
This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.
Sequence of operations:
- lv_suspend() has both vg_old and vg_new
and stashes a copy of each onto the vginfo:
lvmcache_save_suspended_vg(vg_old);
lvmcache_save_suspended_vg(vg_new);
- vg_commit() happens, which causes all clvmd
instances to call lvmcache_commit_metadata(vg).
A flag is set in the vginfo indicating the
transition from the old to new VG:
vginfo->suspended_vg_committed = 1;
- lv_resume() needs either vg_old or vg_new
to use in resuming LVs. It doesn't want to
read the VG from disk since devices are
suspended, so it gets the VG stashed by
lv_suspend:
vg = lvmcache_get_suspended_vg(vgid);
If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
The old code was doing unnecessary label scans when
checking to see if the new VG name exists. A single
label_scan is sufficient if it is done after the
new VG lock is held.
Move the location of scans to make it clearer and avoid
unnecessary repeated scanning. There should be one scan
at the start of a command which is then used through the
rest of command processing.
Previously, the initial label scan was called as a side effect
from various utility functions. This would lead to it being called
unnecessarily. It is an expensive operation, and should only be
called when necessary. Also, this is a primary step in the
function of the command, and as such it should be called prominently
at the top level of command processing, not as a hidden side effect
of a utility function. lvm knows exactly where and when the
label scan needs to be done. Because of this, move the label scan
calls from the internal functions to the top level of processing.
Other specific instances of lvmcache_label_scan() are still called
unnecessarily or unclearly by specific commands that do not use
the common process_each functions. These will be improved in
future commits.
During the processing phase, rescanning labels for devices in a VG
needs to be done after the VG lock is acquired in case things have
changed since the initial label scan. This was being done by way
of rescanning devices that had the INVALID flag set in lvmcache.
This usually approximated the right set of devices, but it was not
exact, and obfuscated the real requirement. Correct this by using
a new function that rescans the devices in the VG:
lvmcache_label_rescan_vg().
Apart from being inexact, the rescanning was extremely well hidden.
_vg_read() would call ->create_instance(), _text_create_text_instance(),
_create_vg_text_instance() which would call lvmcache_label_scan()
which would call _scan_invalid() which repeats the label scan on
devices flagged INVALID. lvmcache_label_rescan_vg() is now called
prominently by _vg_read() directly.
When adjusting region size for clustered VG it always needs to fit
2 full bitset into 1MB due to old limits of CPG.
This is relatively big amount of bits, but we have still limitation
for region size to fit into 32bits (0x8000000).
So for too big mirrors this operation needs to fail - so whenever
function returns now 0, it means we can't find matching region_size.
Since return 0 is now 'error' we need to also pass proper region_size
when creating pvmove mirror.
Fixing regresion on argument acceptance where any lv can be passed
with paramaterless lvconvert which is meant to figure out needed
operation - i.e. wait for mirror synchronization.
User has no other 'effective' method to wait for mirror getting in-sync.
Since we support snapshot of mirrors, we do need to properly check
for stacked lock holder - fixes problem of pvmove in cluster
with mirrors under snapshot.
WHATS_NEW for this patch goes with 'Restore pvmove support...'
Prevent call of dm_stats_populate(), when there has been no
stats region detected for a DM device.
Such skip is evaluated as 'correct' visit of stats call and
not causing 'dmstats' command failure.
Resulting loop table line was streamed to 'stderr' stream - assuming this
was not a feature when user used '-v' for more verbose output
and properly show it via 'log_verbose()' on 'stdout'.
Occasionaly users may need to peek into 'component devices.
Normally lvm2 does not let users activation component.
This patch adds special mode where user can activate
component LV in a 'read-only' mode i.e.:
lvchange -ay vg/pool_tdata
All devices can be deactivated with:
lvchange -an vg | vgchange -an....
If componet devices could be activated alone, ensure they are not breaking
common commands.
TODO: mostly likely this is not a definite list of all needed checks
and more will come later.
Improve pvmove to accept 'locally' active LVs together with
exclusive active LVs.
In the 1st. phase it now recognizes whether exclusive pvmove is needed.
For this case only 'exclusively' or 'locally-only without remote
activative state' LVs are acceptable and all others are skipped.
During build-up of pvmove 'activation' steps are taken, so if
there is any problem we can now 'skip' LVs from pvmove operation
rather then giving-up whole pvmove operation.
Also when pvmove is restarted, recognize need of exclusive pvmove,
and use it whenever there is LV, that require exclusive activation.
