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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.
Previous versions of lvm will not obey the restrictions
imposed by the new system_id, and would allow such a VG
to be written. So, a VG with a new system_id is further
changed to force previous lvm versions to treat it as
read-only. This is done by removing the WRITE flag from
the metadata status line of these VGs, and putting a new
WRITE_LOCKED flag in the flags line of the metadata.
Versions of lvm that recognize WRITE_LOCKED, also obey the
new system_id. For these lvm versions, WRITE_LOCKED is
identical to WRITE, and the rules associated with matching
system_id's are imposed.
A new VG lock_type field is also added that causes the same
WRITE/WRITE_LOCKED transformation when set. A previous
version of lvm will also see a VG with lock_type as read-only.
Versions of lvm that recognize WRITE_LOCKED, must also obey
the lock_type setting. Until the lock_type feature is added,
lvm will fail to read any VG with lock_type set and report an
error about an unsupported lock_type. Once the lock_type
feature is added, lvm will allow VGs with lock_type to be
used according to the rules imposed by the lock_type.
When both system_id and lock_type settings are removed, a VG
is written with the old WRITE status flag, and without the
new WRITE_LOCKED flag. This allows old versions of lvm to
use the VG as before.
Set ACCESS_NEEDS_SYSTEM_ID VG status flag whenever there is
a non-lvm1 system_id set. Prevents concurrent access from
older LVM2 versions.
Not set on VGs that bear a system_id only due to conversion
from lvm1 metadata.
Export _lvm1_system_id as generate_lvm1_system_id and call it in
vg_setup() so it is set before writing the metadata to disk
and not missing from the initial metadata backup file.
Move the lvm1 sys ID into vg->lvm1_system_id and reenable the #if 0
LVM1 code. Still display the new-style system ID in the same
reporting field, though, as only one can be set.
Add a format feature flag FMT_SYSTEM_ON_PVS for LVM1 and disallow
access to LVM1 VGs if a new-style system ID has been set.
Treat the new vg->system_id as const.
Move code for creation of thin volume into a single place
out of lv_extend(). This allows to drop extra pool arg
for alloc_lv_segment() && lv_extend() and makes code
more easier to read and follow.
This is addendum for commit 6dc7b783c8.
LVM1 format stores the ALLOCATABLE flag directly in PV header, not
in VG metadata. So the code needs to be fixed further to work
properly for lvm1 format so that the correct PV header is written
(the flag is set only if the PV is in some VG, unset otherwise).
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).
DO NOT USE LVMETAD IF YOU HAVE ANY LVM1-FORMATTED PVS.
You may continue to use it without lvmetad, but do please schedule
an upgrade to the lvm2 format (with 'vgconvert').
Sending the original LVM1 formatted metadata to lvmetad is breaking
assumptions made by the code, so I am marking the format as obsolete for
now and no longer sending it to lvmetad.
This means that if you are using lvmetad, lvm1 volumes will usually
appear invisible - though not always: it depends on exactly what
sequence of commands you run!
The current situation is not satisfactory.
We'll either fix lvmetad and reenable this or we'll fix the code to
issue appropriate warning messages when lvm1 PVs are encountered
to avoid accidents.
(The latest unfixed problem is that lvmetad assumes metadata sequence
numbers exist and always increase - but the lvm1 format does not define
or store any sequence number, confusing both the daemon and client
when default values get passed to-and-fro.)
All labellers always use the "private" (void *) field as the fmt pointer. Making
this fact explicit in the type of the labeller simplifies the label reporting
code which needs to extract the format. Moreover, it removes a number of
error-prone casts from the code.
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
Assign fid as the last step before returning VG.
Make the format reader for 'lvm1' and 'pool' equal to 'lvm2' format reader.
It has caused memory corruption to lvmetad as it later calls
destroy_instance() to allocated fid. This patch should fix problems
with crashing test lvmetad-lvm1.sh.
...to not pollute the common and format-independent code in the
abstraction layer above.
The format1 pv_write has common code for writing metadata and
PV header by calling the "write_disks" fn and when rewriting
the header itself only (e.g. just for the purpose of changing
the PV UUID) during the pvchange operation, we had to tweak
this functionality for the format1 case and we had to assign
the PV the orphan state temporarily.
This patch removes the need for this format1 tweak and it calls
the write_disks with appropriate flag indicating whether this is
a PV write call or a VG write call, allowing for metatada update
for the latter one.
Also, a side effect of the former tweak was that it effectively
invalidated the cache (even for the non-format1 PVs) as we
assigned it the orphan state temporarily just for the format1
PV write to pass.
Also, that tweak made it difficult to directly detect whether
a PV was part of a VG or not because the state was incorrect.
Also, it's not necessary to backup and restore some PV fields
when doing a PV write:
orig_pe_size = pv_pe_size(pv);
orig_pe_start = pv_pe_start(pv);
orig_pe_count = pv_pe_count(pv);
...
pv_write(pv)
...
pv->pe_size = orig_pe_size;
pv->pe_start = orig_pe_start;
pv->pe_count = orig_pe_count;
...this is already done by the layer below itself (the _format1_pv_write fn).
So let's have this cleaned up so we don't need to be bothered
about any 'format1 special case for pv_write' anymore.
The PV header extension information (PV header extension version, flags
and list of Embedding Area locations) is stored just beyond the PV header base.
When calculating the Embedding Area start value (ea_start), the same logic is
used as when calculating the pe_start value for Data Area - the value must
follow exactly the same alignment restrictions for its start value
(the alignment detected automatically or provided via command line using
the --dataalignment and --dataalignmentoffset arguments).
The Embedding Area is placed at the very start of the PV, starting at
ea_start. The Data Area starting at pe_start is placed next. The pe_start is
still properly aligned. Due to the pe_start alignment, it's possible that the
resulting Embedding Area size (ea_size) ends up bigger in size than requested
(but never less than requested).
New tools with PV header extension support will read the extension
if it exists and it's not an error if it does not exist (so old PVs
will still work seamlessly with new tools).
Old tools without PV header extension support will just ignore any
extension.
As for the Embedding Area location information (its start and size),
there are actually two places where this is stored:
- PV header extension
- VG metadata
The VG metadata contains a copy of what's written in the PV header
extension about the Embedding Area location (NULL value is not copied):
physical_volumes {
pv0 {
id = "AkSSRf-difg-fCCZ-NjAN-qP49-1zzg-S0Fd4T"
device = "/dev/sda" # Hint only
status = ["ALLOCATABLE"]
flags = []
dev_size = 262144 # 128 Megabytes
pe_start = 67584
pe_count = 23 # 92 Megabytes
ea_start = 2048
ea_size = 65536 # 32 Megabytes
}
}
The new metadata fields are "ea_start" and "ea_size".
This is mostly useful when restoring the PV by using existing
metadata backups (e.g. pvcreate --restorefile ...).
New tools does not require these two fields to exist in VG metadata,
they're not compulsory. Therefore, reading old VG metadata which doesn't
contain any Embedding Area information will not end up with any kind
of error but only a debug message that the ea_start and ea_size values
were not found.
Old tools just ignore these extra fields in VG metadata.
Move commod code to destroy orphan VG into free_orphan_vg() function.
Use orphan vgmem for creation of PV lists.
Remove some free_pv_fid() calls (FIXME: check all of them)
FIXME: Check whether we could merge release_vg back again for all VGs.
Before, we used vg_write_lock_held call to determnine the way a device is
opened. Unfortunately, this opened many devices in RW mode when it was not
really necessary. With the OPTIONS+="watch" rule used in the udev rules,
this could fire numerous events while closing such devices (and it caused
useless scans from within udev rules in return).
A common bug we hit with this was with the lvremove command which was unable
to remove the LV since it was being opened from within the udev rules. This
patch should minimize such situations (at least with respect to LVM handling
of devices).
Though there's still a possibility someone will open a device 'outside' in
parallel and fire the event based on the watch rule when closing a device
once opened for RW.
Could be reached via few of our lvm2 test cases:
==11501== Invalid read of size 8
==11501== at 0x49B2E0: _area_length (import-extents.c:204)
==11501== by 0x49B40C: _read_linear (import-extents.c:222)
==11501== by 0x49B952: _build_segments (import-extents.c:323)
==11501== by 0x49B9A0: _build_all_segments (import-extents.c:334)
==11501== by 0x49BB4C: import_extents (import-extents.c:364)
==11501== by 0x497655: _format1_vg_read (format1.c:217)
==11501== by 0x47E43E: _vg_read (metadata.c:2901)
cut from t-vgcvgbackup-usage.sh
--
pvcreate -M1 $(cat DEVICES)
vgcreate -M1 -c n $vg $(cat DEVICES)
lvcreate -l1 -n $lv1 $vg $dev1
--
Idea of the fix is rather defensive - to allocate one extra element
to 'map' array which is then used in _area_length() - where the
loop checks, whether next map entry is continuous.
By placing there always one extra zero entry -
we fix the read of unallocated memory, and we make sure the data would
not make a continous block.
FIXME: there could be a problem if some special broken lvm1 data would be imported.
As the format1 is currently not really used - leave it for future fix
and use this small hotfix for now.
As code uses strncpy(system_id, NAME_LEN) and doesn't set '\0'
Fix it by always allocating NAME_LEN + 1 buffer size and with zalloc
we always get '\0' as the last byte.
This bug may trigger some unexpected behavior of the string operation
code - depends on the pool allocator.
FIXME: refactor this code to alloc_vg.
This is essential for proper format instance ref_count support. We must
use these functions to set the fid everywhere from now on, even the NULL
value!
