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Recent changes allow some major simplification of the way
lvmcache works and is used. lvmcache_label_scan is now
called in a controlled fashion at the start of commands,
and not via various unpredictable side effects. Remove
various calls to it from other places. lvmcache_label_scan
should not be called from anywhere during a command, because
it produces an incorrect representation of PVs with no MDAs,
and misclassifies them as orphans. This has been a long
standing problem. The invalid flag and rescanning based on
that is no longer used and removed. The 'force' variation is
no longer needed and removed.
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.
When process_each_pv() calls vg_read() on the orphan VG, the
internal implementation was doing an unnecessary
lvmcache_label_scan() and two unnecessary label_read() calls
on each orphan. Some of those unnecessary label scans/reads
would sometimes be skipped due to caching, but the code was
always doing at least one unnecessary read on each orphan.
The common format_text case was also unecessarily calling into
the format-specific pv_read() function which actually did nothing.
By analyzing each case in which vg_read() was being called on
the orphan VG, we can say that all of the label scans/reads
in vg_read_orphans are unnecessary:
1. reporting commands: the information saved in lvmcache by
the original label scan can be reported. There is no advantage
to repeating the label scan on the orphans a second time before
reporting it.
2. pvcreate/vgcreate/vgextend: these all share a common
implementation in pvcreate_each_device(). That function
already rescans labels after acquiring the orphan VG lock,
which ensures that the command is using valid lvmcache
information.
To do label scanning, lvm code calls lvmcache_label_scan().
Change lvmcache_label_scan() to use the new label_scan()
based on bcache.
Also add lvmcache_label_rescan_vg() which calls the new
label_scan_devs() which does label scanning on only the
specified devices. This is for a subsequent commit and
is not yet used.
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.
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
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.
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.
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 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.
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.
Refactor the recent metadata-reading optimisation patches.
Remove the recently-added cache fields from struct labeller
and struct format_instance.
Instead, introduce struct lvmcache_vgsummary to wrap the VG information
that lvmcache holds and add the metadata size and checksum to it.
Allow this VG summary information to be looked up by metadata size +
checksum. Adjust the debug log messages to make it clear when this
shortcut has been successful.
(This changes the optimisation slightly, and might be extendable
further.)
Add struct cached_vg_fmtdata to format-specific vg_read calls to
preserve state alongside the VG across separate calls and indicate
if the details supplied match, avoiding the need to read and
process the VG metadata again.
A full search for duplicate PVs in the case of pvs -a
is only necessary when duplicates have previously been
detected in lvmcache. Use a global variable from lvmcache
to indicate that duplicate PVs exist, so we can skip the
search for duplicates when none exist.
When multiple duplicate devices are specified on the
command line, the PV is processed once for each of them,
but pv->dev is the device used each time.
This overrides the PV device to reflect the duplicate
device that was specified on the command line. This is
done by hacking the lvmcache to replace pv->dev with the
device of the duplicate being processed. (It would be
preferable to override pv->dev without munging the content
of the cache, and without sprinkling special cases throughout
the code.)
This override only applies when multiple duplicate devices are
specified on the command line. When only a single duplicate
device of pv->dev is specified, the priority is to display the
cached pv->dev, so pv->dev is not overridden by the named
duplicate device.
In the examples below, loop3 is the cached device referenced
by pv->dev, and is given priority for processing. Only after
loop3 is processed/displayed, will other duplicate devices
loop0/loop1 appear (when requested on the command line.)
With two duplicate devices, loop0 and loop3:
# pvs
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop0
PV VG Fmt Attr PSize PFree
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m
# pvs /dev/loop3
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop0
PV VG Fmt Attr PSize PFree
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m
# pvs /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop0
PV VG Fmt Attr PSize PFree
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m
# pvs -o+dev_size /dev/loop0 /dev/loop3
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop0
PV VG Fmt Attr PSize PFree DevSize
/dev/loop0 loopa lvm2 a-- 12.00m 12.00m 16.00m
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
With three duplicate devices, loop0, loop1, loop3:
# pvs -o+dev_size
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop3
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop1
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop3 /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop0 loopa lvm2 a-- 12.00m 12.00m 16.00m
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop3 /dev/loop1
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop1 loopa lvm2 a-- 12.00m 12.00m 32.00m
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop0 /dev/loop1
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop1 loopa lvm2 a-- 12.00m 12.00m 32.00m
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
# pvs -o+dev_size /dev/loop0 /dev/loop1 /dev/loop3
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop1 not /dev/loop0
Found duplicate PV XhLbpVo0hmuwrMQLjfxuAvPFUFZqD4vr: using /dev/loop3 not /dev/loop1
PV VG Fmt Attr PSize PFree DevSize
/dev/loop0 loopa lvm2 a-- 12.00m 12.00m 16.00m
/dev/loop1 loopa lvm2 a-- 12.00m 12.00m 32.00m
/dev/loop3 loopa lvm2 a-- 12.00m 12.00m 32.00m
The list of strings is used quite frequently and we'd like to reuse
this simple structure for report selection support too. Make it part
of libdevmapper for general reuse throughout the code.
This also simplifies the LVM code a bit since we don't need to
include and manage lvm-types.h anymore (the string list was the
only structure defined there).
Since commit f12ee43f2e call destroy,
it start to check all VGs are unlocked. However when we become_daemon,
we simply reset locking (since lock is still kept by parent process).
So implement a simple 'reset' flag.
Changes:
- move device type registration out of "type filter" (filter.c)
to a separate and new dev-type.[ch] for common use throughout the code
- the structure for keeping the major numbers detected for available
device types and available partitioning available is stored in
"dev_types" structure now
- move common partitioning detection code to dev-type.[ch] as well
together with other device-related functions bound to dev_types
(see dev-type.h for the interface)
The dev-type interface contains all common functions used to detect
subsystems/device types, signature/superblock recognition code,
type-specific device properties and other common device properties
(bound to dev_types), including partitioning support.
- add dev_types instance to cmd context as cmd->dev_types for common use
- use cmd->dev_types throughout as a central point for providing
information about device types
PV header extension comes just beyond the existing PV header base:
PV header base (existing):
- uuid
- device size
- null-terminated list of Data Areas
- null-terminater list of MetaData Areas
PV header extension:
- extension version
- flags
- null-terminated list of Embedding Areas
This patch also adds "eas" (Embedding Areas) list to lvmcache (lvmcache_info)
and it also adds support for common operations on the list (just like for
already existing "das" - Data Areas list):
- lvmcache_add_ea
- lvmcache_update_eas
- lvmcache_foreach_ea
- lvmcache_del_eas
Also, add ea_start and ea_size to struct physical_volume for processing
PV Embedding Area location throughout the code (currently only one
Embedding Area is supported, though the definition on disk allows for
more if needed in the future...).
Also, define FMT_EAS format flag to mark that the format actually
supports Embedding Areas (currently format-text only).
leaving behind the LVM-specific parts of the code (convenience wrappers that
handle `struct device` and `struct cmd_context`, basically). A number of
functions have been renamed (in addition to getting a dm_ prefix) -- namely,
all of the config interface now has a dm_config_ prefix.
Extend vginfo cache with cached VG structure. So if the same metadata
are use, skip mda decoding in the case, the same data are in use.
This helps for operations like activation of all LVs in one VG,
where same data were decoded giving the same output result.
Patch adds 1-to-1 connection between volume_group and lvmcache_vginfo.
Instead of regenerating config tree and parsing same data again,
check whether export_vg_to_buffer does not produce same string as
the one already cached - in this case keep it, otherwise throw cached
content away.
For the code simplicity calling _free_cached_vgmetadata() with
vgmetadata == NULL as the function handles this itself.
Note: sometimes export_vg_to_buffer() generates almost the same data
with just different time stamp, but for the patch simplicity,
data are reparsed in this case.
This patch currently helps for vgrefresh.
Change function import_vg_from_buffer() to import_vg_from_config_tree().
Instead of creating config tree inside the function allow config tree to
be passed as parameter - usable later for caching.
Set cmd->independent_metadata_areas if metadata/dirs or disk_areas in use.
- Identify and record this state.
Don't skip full scan when independent mdas are present even if memlock is set.
- Clusters and OOM aren't supported, so no problem doing the proper scans.
Avoid revalidating the label cache immediately after scanning.
- A simple optimisation.
Support scanning for a single VG in independent mdas.
- Not used by the fix but I left it in anyway as later patches might use it.
where we should not expose internal VG names/uuids (the ones with "#" prefix )through the
interface. Otherwise, we could end up with library users opening internal VGs which will
initiate locking mechanism that won't be cleaned up properly.
"#orphans_{lvm1, lvm2, pool}" names are treated in a special way, they are truncated first
to "orphans" and this is used as a part of the lock name then (e.g. while calling lvm_vg_open()).
When library user calls lvm_vg_close(), the original name "orphans_{lvm1, lvm2, pool}"
is used directly and therefore no unlock occurs.
We should exclude internal VG names and uuids in the lists provided by lvmcache:
lvmcache_get_vgids() and lvmcache_get_vgnames().
- Add drop_precommitted flag to force drop precommitted metadata
- add lvmcache_commit_metadata() which upgrades precommitted metadata in cache
No functional change in this patch - just preparation for following change.
Add a new constraint that vgname locks must be obtained in
alphabetical order. At this point, we have test coverage for
the 3 commands affected - vgsplit, vgmerge, and vgrename.
Tests have been updated to cover these commands.
Going forward any command or library call that must obtain
more than one vgname lock must do so in alphabetical order.
Future patches will update lvm2app to enforce this ordering.
Author: Dave Wysochanski <dwysocha@redhat.com>
