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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
Dop unused value assignments.
Unknown is detected via other combination
(!linear && !striped).
Also change the log_error() message into a warning,
since the function is not really returning error,
but still keep the INTERNAL_ERROR.
Ret value is always set later.
We exclude some signatures from being wiped when using blkid wiping.
These are signatures which we simply overwrite. For example, the
LVM2_member signature which denotes a PV - if we call pvcreate on
existing PV, we just overwrite the PV header, no need to wipe it.
Previously, we counted such signatures as if they were wiped
and they were counted in the final number of wiped signatures
that _wipe_known_signatures_with_blkid fn returned in the "wiped"
output arg. Then the code checking this output arg could be
mislead that wiping happened while no wiping took place in real
and we could fire some code uselessly based on this information
(e.g. refreshing filters/rescanning - see also
commit 6b4066585f).
Before, we refreshed filters and we did full rescan of devices if
we passed through wiping (wipe_known_signatures fn call). However,
this fn returns success even if no signatures were found and so
nothing was wiped. In this case, it's not necessary to do the
filter refresh/rescan of devices as nothing changed clearly.
This patch exports number of wiped signatures from all the
wiping functions below. The caller (_pvcreate_check) then checks
whether any wiping was done at all and if not, no refresh/rescan
is done, saving some time and resources.
Partitioned devices are marked in udev db as:
ID_PART_TABLE="<partition table type name>"
and at the same time they are *not* marked with:
ID_PART_ENTRY_DISK="<parent disk major:minor>"
Where partition table type name is dos/gpt/... But checking the presence
of this variable is enough for LVM here - it just needs to know whether
there's a partition table or not, not interested in the actual type.
The same applies for parent disk major:minor.
Normally, if there are partitions defined on top of device-mapper
device, there should be a device-mapper device created for each
partiton on top of the old one and once the underlying DM device
is used by another devices (partition mappings in this case),
it can't be used as a PV anymore.
However, sometimes, it may happen the partition mappings are
missing - either the partitioning tool is not creating them if
it does not contain full support for device-mapper devices or
the mappings were removed.
Better safe than sorry - check for partition header on DM devs
and filter them out as unsuitable for PVs in case the check is
positive. Whatever the user is doing, let's do our best to prevent
unwanted corruption (...by running pvcreate on top of such device
that would corrupt the partition header).
Avoid playing with +1.
PATH_MAX code needs probably more thinking anyway, since
there is no MAX path in Linux - user may easily create path
with 64kB chars - so 4kB buffer is surelly not enough for
such dirs.
Note:
http://insanecoding.blogspot.cz/2007/11/pathmax-simply-isnt.html
The libblkid can detect DM_snapshot_cow signature and when creating
new LVs with blkid wiping used (allocation/use_blkid_wiping=1 lvm.conf
setting and --wipe y used at the same time - which it is by default).
Do not issue any prompts about this signature when new LV is created
and just wipe it right away without asking questions. Still keep the
log in verbose mode though.
We need both offset and length when trying to wipe detected signatures.
The libblkid can fail so it's good to have an error message issued for
this state instead of being silent (libblkid does not issue any error
messages here). We just issued "stack" here before but that was not
quite useful if some error occurs...
If we're calling pvcreate on a device that already has a PV label,
the blkid detects the existing PV and then we consider it for wiping
before we continue creating the new PV label and we issue a warning
with a prompt whether such old PV label should be removed. We don't
do this with native signature detection code. Let's make it consistent
with old behaviour.
But still keep this "PV" (identified as "LVM1_member" or "LVM2_member"
by blkid) detection when creating new LVs to avoid unexpected PV label
appeareance inside LV.
This is actually the wipefs functionailty as a matter of fact
(wipefs uses the same libblkid calls).
libblkid is more rich when it comes to detecting various
signatures, including filesystems and users can better
decide what to erase and what should be kept.
The code is shared for both pvcreate (where wiping is necessary
to complete the pvcreate operation) and lvcreate where it's up
to the user to decide.
The verbose output contains a bit more information about the
signature like LABEL and UUID.
For example:
raw/~ # lvcreate -L16m vg
WARNING: linux_raid_member signature detected on /dev/vg/lvol0 at offset 4096. Wipe it? [y/n]
or more verbose one:
raw/~ # lvcreate -L16m vg -v
...
Found existing signature on /dev/vg/lvol0 at offset 4096: LABEL="raw.virt:0" UUID="da6af139-8403-5d06-b8c4-13f6f24b73b1" TYPE="linux_raid_member" USAGE="raid"
WARNING: linux_raid_member signature detected on /dev/vg/lvol0 at offset 4096. Wipe it? [y/n]
The verbose output is the same output as found in blkid.
The wipe_known_signatures fn now wraps the _wipe_signature fn that is called
for each known signature (currently md, swap and luks). This patch makes the
code more readable, not repeating the same sequence when used anywhere in the
code. We're going to reuse this code later...
Put common printf() case into a function and use
the string with text format as direct arg to make
the compile time validation of args easier and
code shorter.
Switch log_error() to log_warn(), since 'return 0'
doesn't cause any failure here.
The dev_get_primary_dev fn now returns:
0 if the dev is already a primary dev
1 if the dev is a partition, primary dev is returned in "result" (output arg)
-1 on error
This way, we can better differentiate between the error state
and the state in which the dev supplied is not a partition
in the caller (this was same return value before).
Also, if we already have information about the device type,
we can check its major number against the list of known device
types (cmd->dev_types) directly, so we don't need to go through
the sysfs - we only check the major:minor pair which is a bit
more straightforward and faster. If the dev_types does not have
any info about this device type, the code just fallbacks to
the original sysfs interface to get the partition info.
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
