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Some commands scan labels to populate lvmcache multiple
times, i.e. lvmcache_init, scan labels to fill lvmcache,
lvmcache_destroy, then later repeat
Each time labels are scanned, duplicates are detected,
and preferred devices are chosen. Each time this is done
within a single command, we want to choose the same
preferred devices. So, check for existing preferences
when choosing preferred devices.
This also fixes a problem with the list of unused duplicate
devs when run in an lvm shell. The devs had been allocated
from cmd memory, resulting in invalid list entries between
commands.
A number of places are working on a specific dev when they
call lvmcache_info_from_pvid() to look up an info struct
based on a pvid. In those cases, pass the dev being used
to lvmcache_info_from_pvid(). When a dev is specified,
lvmcache_info_from_pvid() will verify that the cached
info it's using matches the dev being processed before
returning the info. Calling code will not mistakenly
get info for the wrong dev when duplicate devs exist.
This confusion was happening when scanning labels when
duplicate devs existed. label_read for the first dev
would add an info struct to lvmcache for that dev/pvid.
label_read for the second dev would see the pvid in
lvmcache from first dev, and mistakenly conclude that
the label_read from the second dev can be skipped
because it's already been done. By verifying that the
dev for the cached pvid matches the dev being read,
this mismatch is avoided and the label is actually read
from the second duplicate.
If duplicate devices exist for a PV, and one device's
size matches the PV size, but the other doesn't, then
prefer the matching device.
If one device is used by an active LV, prefer that device.
When there are duplicate devices for a PV, one device
is preferred and chosen to exist in the VG. The other
devices are not used by lvm, but are displayed by pvs
with a new PV attr "d", indicating that they are
unchosen duplicate PVs.
The "duplicate" reporting field is set to "duplicate"
when the PV is an unchosen duplicate, and that field
is blank for the chosen PV.
Previously, duplicate PVs were processed as a side effect
of processing the "chosen" PV in lvmcache. The duplicate
PV would be hacked into lvmcache temporarily in place of
the chosen PV.
In the old way, we had to always process the "chosen" PV
device, even if a duplicate of it was named on the command
line. This meant we were processing a different device than
was asked for. This could be worked around by naming
multiple duplicate devs on the command line in which case
they were swapped in and out of lvmcache for processing.
Now, the duplicate devs are processed directly in their
own processing loop. This means we can remove the old
hacks related to processing dups as a side effect of
processing the chosen device. We can now simply process
the device that was named on the command line.
When the same PVID exists on two or more devices, one device
is preferred and used in the VG, and the others are duplicates
and are not used in the VG. The preferred device exists in
lvmcache as usual. The duplicates exist in a specical list
of unused duplicate devices.
The duplicate devs have the "d" attribute and the "duplicate"
reporting field displays "duplicate" for them.
'pvs' warns about duplicates, but the formal output only
includes the single preferred PV.
'pvs -a' has the same warnings, and the duplicate devs are
included in the output.
'pvs <path>' has the same warnings, and displays the named
device, whether it is preferred or a duplicate.
Wait to compare and choose alternate duplicate devices until
after all devices are scanned. During scanning, the first
duplicate dev is kept in lvmcache, and others are kept in a
new list (_found_duplicate_devs).
After all devices are scanned, compare all the duplicates
available for a given PVID and decide which is best.
If the dev used in lvmcache is changed, drop the old dev
from lvmcache entirely and rescan the replacement dev.
Previously the VG metadata from the old dev was kept in
lvmcache and only the dev was replaced.
A new config setting devices/allow_changes_with_duplicate_pvs
can be set to 0 which disallows modifying a VG or activating
LVs in it when the VG contains PVs with duplicate devices.
Set to 1 is the old behavior which allowed the VG to be
changed.
The logic for which of two devs is preferred has changed.
The primary goal is to choose a device that is currently
in use if the other isn't, e.g. by an active LV.
. prefer dev with fs mounted if the other doesn't, else
. prefer dev that is dm if the other isn't, else
. prefer dev in subsystem if the other isn't
If neither device is preferred by these rules, then don't
change devices in lvmcache, leaving the one that was found
first.
The previous logic for preferring a device was:
. prefer dev in subsystem if the other isn't, else
. prefer dev without holders if the other has holders, else
. prefer dev that is dm if the other isn't
The lvmetad connection is created within the
init_connections() path during command startup,
rather than via the old lvmetad_active() check.
The old lvmetad_active() checks are replaced
with lvmetad_used() which is a simple check that
tests if the command is using/connected to lvmetad.
The old lvmetad_set_active(cmd, 0) calls, which
stopped the command from using lvmetad (to revert to
disk scanning), are replaced with lvmetad_make_unused(cmd).
This reverts e28e22b9e1
The problem that that commit was fixing (pytest failure)
no longer appears with the current code, so the commit is
not needed.
That commit is a problem for pvchange, because it prevents
lvmcache from retaining VG metadata even while the global
lock is held. pvchange holds the global lock to ensure
that VG metadata is kept in lvmcache throughout processing.
If the cache is not kept, a PV with zero MDAs will appear
first in its actual VG and then appear again in the orphan VG.
It wrongly appears a second time in the orphan VG only if
the actual VG is dropped from lvmcache.
Use process_each_vg() to lock and read the old VG,
and then call the main vgrename code.
When real VG names are used (not a UUID in place of the
old name), the command still pre-locks the new name
(when strcmp wants it locked first), before calling
process_each_vg on the old name.
In the case where the old name is replaced with a UUID,
process_each_vg now translates that UUID into the real
VG name, which it locks and reads. In this case, we
cannot do pre-locking to maintain lock ordering because
the old name is unknown. So, in this case the strcmp
based lock ordering is suppressed and the old name is
always locked first. This opens a remote chance for
lock ordering conflict between racing vgrenames between
two names where one or both commands use the UUID.
Before commit c1f246fedf,
_get_all_devices() did a full device scan before
get_vgnameids() was called. The full scan in
_get_all_devices() is from calling dev_iter_create(f, 1).
The '1' arg forces a full scan.
By doing a full scan in _get_all_devices(), new devices
were added to dev-cache before get_vgnameids() began
scanning labels. So, labels would be read from new devices.
(e.g. by the first 'pvs' command after the new device appeared.)
After that commit, _get_all_devices() was called
after get_vgnameids() was finished scanning labels.
So, new devices would be missed while scanning labels.
When _get_all_devices() saw the new devices (after
labels were scanned), those devices were added to
the .cache file. This meant that the second 'pvs'
command would see the devices because they would be
in .cache.
Now, the full device scan is factored out of
_get_all_devices() and called by itself at the
start of the command so that new devices will
be known before get_vgnameids() scans labels.
When two different VGs with the same name exist,
they are both stored in lvmcache using the vginfo->next
list. Previously, the code would print warnings (sometimes)
when adding VGs to this list. Now the duplicate VG names
are handled by higher level code, so this list no longer
needs to print warnings about duplicate VG names being found.
After recent changes to process_each, vg_read() is usually
given both the vgname and vgid for the intended VG.
However, in some cases vg_read() is given a vgid with
no vgname, or is given a vgname with no vgid.
When given a vgid with no vgname, vg_read() uses lvmcache
to look up the vgname using the vgid. If the vgname is
not found, vg_read() fails.
When given a vgname with no vgid, vg_read() should also
use lvmcache to look up the vgid using the vgname.
If the vgid is not found, vg_read() fails.
If the lvmcache lookup finds multiple vgids for the
vgname, then the lookup fails, causing vg_read() to fail
because the intended VG is uncertain.
Usually, both vgname and vgid for the intended VG are passed
to vg_read(), which means the lvmcache translations
between vgname and vgid are not done.
When not using lvmetad, this uses the system_id field in
the cached vginfo structs that are populated during a scan.
When using lvmetad, this requests the VG from lvmetad, and
checks the system_id field in the returned metadata.
When lvmetad is used and lvmcache update function (lvmcache_update_vgname_and_id)
was called to update existing lvmcache records, a condition was met
which made to retun from the update function immediately, effectively
making it NOOP.
It seems there's no reason for such condition and lvmcache should be
update appropriately even when lvmetad used as lvmcache may be reused,
most notably in lvm shell.
It's possible this is a remnant of the lvmetad development code which
didn't get removed for some reason and the bug didn't get spotted
because lvm shell is not used often (the condition dates back to 2012
or so).
Example, lvmetad and lvm shell used:
lvm> pvs
PV VG Fmt Attr PSize PFree
/dev/sda vg lvm2 a-- 124.00m 124.00m
Before this patch:
==================
lvm> vgremove vg
Volume group "vg" successfully removed
lvm> pvs
With this patch applied:
========================
lvm> vgremove vg
Volume group "vg" successfully removed
lvm> pvs
PV VG Fmt Attr PSize PFree
/dev/sda lvm2 --- 128.00m 128.00m
The old code made two loops through the PVs: in the first
loop it found the max PV and VG name lengths, and in the
second loop it printed each PV using the name lengths as
field widths for aligning columns.
The new code uses process_each_pv() which makes one loop
through the PVs. In the *first* call to pvscan_single(),
the max name lengths are found by looping through the
lvmcache entries which have been populated by the generic
process_each code prior to calling any _single functions.
Subsequent calls to pvscan_single() reuse the max lengths
that were found by the first call.
This reverts commit 70db1d523d.
Since we use 'strncpy' even for case where it exactly matches
the buffer size and \0 is not expected to be added there.
This tries harder to avoid creating duplicate global locks in
sanlock VGs by refusing to create a new sanlock VG with a
global lock if other sanlock VGs exist that may have a gl.
vgsummary information contains provisional VG information
that is obtained without holding the VG lock. This info
can be used to lock the VG, and then read it with vg_read().
After the VG is read properly, the vgsummary info should
be verified.
Add the VG lock_type to the vgsummary. It needs to be
known before the VG can be locked and read.
log_warn was added recently because no known code used
the given condition, but running pvcreate on an existing
PV uses this case, and should not produce a warning.
This is an alternative/equivalent to commit
ca67cf84df
The problem (wrong label->dev after a new preferred
duplicate device is chosen) was isolated to the lvmetad
case (non-lvmetad worked fine), and this fixes the problem
by setting the new label->dev in the lvmetad-specific
code rather than in the general lvmcache code.
In process_each_{vg,lv,pv} when no vgname args are given,
the first step is to get a list of all vgid/vgname on the
system. This is exactly what lvmetad returns from a
vg_list request. The current code is doing a vg_lookup
on each VG after the vg_list and populating lvmcache with
the info for each VG. These preliminary vg_lookup's are
unnecessary, because they will be done again when the
processing functions call vg_read. This patch eliminates
the initial round of vg_lookup's, which can roughly cut in
half the number of lvmetad requests and save a lot of extra work.
Example:
/dev/loop0 and /dev/loop1 are duplicates,
created by copying one backing file to the
other.
'identity /dev/loopX' creates an identity
mapping for loopX named idmloopX, which
adds a duplicate for the named device.
The duplicate selection code for lvmetad is
incomplete, and lvmetad is disabled for this
example.
[~]# losetup -f loopfile0
[~]# pvs
PV VG Fmt Attr PSize PFree
/dev/loop0 foo lvm2 a-- 308.00m 296.00m
[~]# losetup -f loopfile1
[~]# pvs
Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/loop1 not /dev/loop0
Using duplicate PV /dev/loop1 which is more recent, replacing /dev/loop0
PV VG Fmt Attr PSize PFree
/dev/loop1 foo lvm2 a-- 308.00m 308.00m
[~]# ./identity /dev/loop0
[~]# pvs
Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/loop1 not /dev/loop0
Using duplicate PV /dev/loop1 without holders, replacing /dev/loop0
Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/mapper/idmloop0 not /dev/loop1
Using duplicate PV /dev/mapper/idmloop0 from subsystem DM, replacing /dev/loop1
PV VG Fmt Attr PSize PFree
/dev/mapper/idmloop0 foo lvm2 a-- 308.00m 296.00m
[~]# ./identity /dev/loop1
[~]# pvs
WARNING: duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV is being used from both devices /dev/loop0 and /dev/loop1
Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/loop1 not /dev/loop0
Using duplicate PV /dev/loop1 which is more recent, replacing /dev/loop0
Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/mapper/idmloop0 not /dev/loop1
Using duplicate PV /dev/mapper/idmloop0 from subsystem DM, replacing /dev/loop1
Found duplicate PV LnSOEqzEYED3RvIOa5PZP2s7uyuBLmAV: using /dev/mapper/idmloop1 not /dev/mapper/idmloop0
Using duplicate PV /dev/mapper/idmloop1 which is more recent, replacing /dev/mapper/idmloop0
PV VG Fmt Attr PSize PFree
/dev/mapper/idmloop1 foo lvm2 a-- 308.00m 308.00m
pv_write is called both to write orphans and to rewrite PV headers
of PVs in VGs. It needs to select the correct VG id so that the
internal cache state gets updated correctly.
It only affected commands that involved further steps after
the pv_write and was often masked because the metadata would
be re-read off disk and correct itself.
"Incorrect metadata area header checksum" warnings appeared.
Example:
Create vg1 containing dev1, dev2 and dev3.
Hide dev1 and dev2 from the system.
Fix up vg1 with vgreduce --removemissing.
Bring back dev1 and dev2.
In a single operation reinstate dev1 and dev2 into vg1 (vgextend).
Done as separate operations (automatically fix-up dev1 and dev2 as orphans,
then vgextend) it worked, but done all in one go the internal cache got
corrupted and warnings about checksum errors appeared.
Commit 80f4b4b803
introduced undesirable side-effects for lvm2app user
which happens to be our own python binding.
It appear obtaing pvs list keeps global lock.
So restricting this to VG_GLOBAL READ locks and skip
the drop skip if WRITE lock is held.
