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devices/scan_lvs (default 1) determines whether lvm
will scan LVs for layered PVs. The lvm behavior has
always been to scan LVs, but it's rare for LVs to have
layered PVs, and much more common for there to be many
LVs that substantially slow down scanning with no benefit.
This is implemented in the usable filter, and has the
same effect as listing all LVs in the global_filter.
The md filter can operate in two native modes:
- normal: reads only the start of each device
- full: reads both the start and end of each device
md 1.0 devices place the superblock at the end of the device,
so components of this version will only be identified and
excluded when lvm uses the full md filter.
Previously, the full md filter was only used in commands
that could write to the device. Now, the full md filter
is also applied when there is an md 1.0 device present
on the system. This means the 'pvs' command can avoid
displaying md 1.0 components (at the cost of doubling
the i/o to every device on the system.)
(The md filter can operate in a third mode, using udev,
but this is disabled by default because there have been
problems with reliability of the info returned from udev.)
As we start refactoring the code to break dependencies (see doc/refactoring.txt),
I want us to use full paths in the includes (eg, #include "base/data-struct/list.h").
This makes it more obvious when we're breaking abstraction boundaries, eg, including a file in
metadata/ from base/
Filters are still applied before any device reading or
the label scan, but any filter checks that want to read
the device are skipped and the device is flagged.
After bcache is populated, but before lvm looks for
devices (i.e. before label scan), the filters are
reapplied to the devices that were flagged above.
The filters will then find the data they need in
bcache.
- Use 'lvmcache' consistently instead of 'metadata cache'
- Always use 5 characters for source line number
- Remember to convert uuids into printable form
- Use <no name> rather than (null) when VG has no name.
If we're using persistent .cache file, we're reading this file instead
of traversing the /dev content. Fix missing indexing by VGID and LVID
here - hook this into persistent_filter_load where we populate device
cache from persistent .cache file instead of scanning /dev.
For example, inducing situation in which we warn about different device
actually used than what LVM thinks should be used based on metadata:
$ lsblk -s /dev/vg/lvol0
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vg-lvol0 253:4 0 124M 0 lvm
`-loop1 7:1 0 128M 0 loop
$ lvmconfig --type diff
global {
use_lvmetad=0
}
devices {
obtain_device_list_from_udev=0
}
(obtain_device_list_from_udev=0 also means the persistent .cache file is used)
Before this patch - pvs is fine as it does the dev scan, but lvs relies
on persistent .cache file and it misses the VGID/LVID indices to check
and warn about incorrect devices used:
$ pvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
PV VG Fmt Attr PSize PFree
/dev/loop0 vg lvm2 a-- 124.00m 0
$ lvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
LV VG Attr LSize
lvol0 vg -wi-a----- 124.00m
With this patch applied - both pvs and lvs is fine - the indices are
always created correctly (lvs just an example here, other LVM commands
that rely on persistent .cache file are fixed with this patch too):
$ pvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
PV VG Fmt Attr PSize PFree
/dev/loop0 vg lvm2 a-- 124.00m 0
$ lvs
Found duplicate PV B9gXTHkIdEIiMVwcOoT2LX3Ywh4YIHgR: using /dev/loop0 not /dev/loop1
Using duplicate PV /dev/loop0 without holders, ignoring /dev/loop1
WARNING: Device mismatch detected for vg/lvol0 which is accessing /dev/loop1 instead of /dev/loop0.
LV VG Attr LSize
lvol0 vg -wi-a----- 124.00m
We already do check for suspended devs within udev rules where
the pvscan is to update lvmetad. So the check for suspended devs
in "pre-lvmetad" chain is not useful here - remove it - it may
be a source of hardly to detect races anyway (if udev rule detects
the device is not suspended and then the pvscan instance sees the
dev as suspended, we may end up not reacting to the event properly).
Fix regression introduced with commit:
2fc126b00d
This commit has moved pv_min_size() test in front
of device_is_usable(). However pv_min_size needs to open device,
so it may have actually get blocked.
So restore the original order and first validate
dm device to be usable for open.
It's worth to note that such check is not 'race-free',
but it usually eliminates 99.99% of problems ;).
Print [source:handler] in filters' debug messages only if external
device info source other than "none" is used.
$ lvmconfig --type full devices/external_device_info_source
external_device_info_source="none
Before this patch (from the -vvvv log):
filters/filter-usable.c:47 /dev/mapper/test: Skipping: Too small to hold a PV [none:(nil)]
filters/filter-md.c:33 /dev/sdb: Skipping md component device [none:(nil)]
filters/filter-partitioned.c:25 /dev/vda: Skipping: Partition table signature found [none:(nil)]
With this patch applied:
filters/filter-usable.c:44 /dev/mapper/test: Skipping: Too small to hold a PV
filters/filter-md.c:35 /dev/sdb: Skipping md component device
filters/filter-partitioned.c:27 /dev/vda: Skipping: Partition table signature found
Just like MD filtering that detects components of software RAID (md),
add detection for firmware RAID.
We're not adding any native code to detect this - there are lots of
firmware RAIDs out there which is just out of LVM scope. However,
with current changes with which we're able to get device info from
external sources (e.g. external_device_info_source="udev"), we can
do this easily if the external device status source has this kind
of information - which is the case of "udev" source where the results
of blkid scans are stored.
This detection should cover all firmware RAIDs that blkid can detect and
which are identified as:
ID_FS_TYPE = {adaptec,ddf,hpt45x,hpt37x,isw,jmicron,lsi_mega,nvidia,promise_fasttrack,silicon_medley,via}_raid_member
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.
The filter-partitioned code should contain only checks in "partition" domain.
The check for pv_min_size should actually be a part of filter-usable.
If the device size is less than pv_min_size, such device is not usable
as a PV so this check clearly belongs here logically.
With udev external info source, we can get device size via libudev's
sysfs reading interface and we can avoid opening the device this way
effectively.
mpath components are marked in udev db as:
ID_FS_TYPE="mpath_member"
or
DM_MULTIPATH_DEVICE_PATH="1"
(it depends on udev rule/blkid version used for handling mpath)
Composite filter is a filter that can put several filters in one set.
This patch adds a switch when creating the composite filter which will
enable or disable external device info handles for all the filters
the composite filter encompasses.
We want to use this external device info for majority of the filters
which are in the "lvmetad filter chain" (or the respective part if
we're not using lvmetad).
Following patches will use the enabled external device handle in
concrete filters from the composite filter...
LVM2.2.02.112/tools/toollib.c:1991: leaked_storage: Variable "iter" going out of scope leaks the storage it points to.
LVM2.2.02.112/lib/filters/filter-usable.c:89: leaked_storage: Variable "f" going out of scope leaks the storage it points to.
LVM2.2.02.112/lib/activate/dev_manager.c:1874: leaked_handle: Handle variable "fd" going out of scope leaks the handle.
We can't hang on blocked or suspended devices when the scan is done
for lvmetad update - when the device gets unblocked or resumed, there's
always CHANGE event generated which will fire the udev rule to run
extra pvscan --cache for that device which makes sure that lvmetad
is up-to-date.
filters/filter-usable.c:22: warning: "ucp.check_..." may be used uninitialized in this function
This can't actually be hit in real, but let's clean this up for the compiler
to be happy again.
With this change, the filter chains used look like this now:
A) When *lvmetad is not used*:
- persistent filter -> regex filter -> sysfs filter ->
global regex filter -> type filter ->
usable device filter(FILTER_MODE_NO_LVMETAD) ->
mpath component filter -> partitioned filter ->
md component filter
B) When *lvmetad is used* (two separate filter chains):
- the lvmetad filter chain used when scanning devs for lvmetad update:
sysfs filter -> global regex filter -> type filter ->
usable device filter(FILTER_MODE_PRE_LVMETAD) ->
mpath component filter -> partitioned filter ->
md component filter
- the filter chain used for lvmetad responses:
persistent filter -> usable device filter(FILTER_MODE_POST_LVMETAD) ->
regex filter
Usable device filter is responsible for filtering out unusable DM devices.
The filter has 3 modes of operation:
- FILTER_MODE_NO_LVMETAD:
When this mode is used, we check DM device usability by looking:
- whether device is empty
- whether device is blocked
- whether device is suspended (only on devices/ignore_suspended_devices=1)
- whether device uses an error target
- whether device name/uuid is reserved
- FILTER_MODE_PRE_LVMETAD:
When this mode is used, we check DM device usability by looking:
- whether device is empty
- whether device is suspended (only on devices/ignore_suspended_devices=1)
- whether device uses an error target
- whether device name/uuid is reserved
- FILTER_MODE_POST_LVMETAD:
When this mode is used, we check DM device usability by looking:
- whether device is blocked
- whether device is suspended (only on devices/ignore_suspended_devices=1)
These modes will be used by subsequent patch to create different
instances of this filter, depending on lvmetad use.
Currently, there are 5 things that device_is_usable function checks
(for DM devices only, of course):
- is device empty?
- is device blocked? (mirror)
- is device suspended?
- is device composed of an error target?
- is device name/uuid reserved?
If answer to any of these questions is "yes", then the device is not usable.
This patch just adds possibility to choose what to check for exactly - the
device_is_usable function now accepts struct dev_usable_check_params make
this selection possible. This is going to be used by subsequent patches.
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
If using persistent filter and we're refreshing filters (just like we
do for pvcreate now after commit 54685c20fc),
we can't rely on getting the primary device of the partition from the cache
as such device could be already filtered by persistent filter and we get
a device cache lookup failure for such device.
For example:
$ lvm dumpconfig --type diff
devices {
obtain_device_list_from_udev=0
}
$lsblk /dev/sda
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 128M 0 disk
`-sda1 8:1 0 127M 0 part
$cat /etc/lvm/cache/.cache | grep sda
"/dev/sda1",
$pvcreate /dev/sda1
dev_is_mpath: failed to get device for 8:1
Physical volume "/dev/sda1" successfully created
The problematic part of the code called dev_cache_get_by_devt
to get the device for the device number supplied. Then the code
used dev_name(dev) to get the name which is then used in check
whether there's any mpath on top of this dev...
This patch uses sysfs to get the base name for the partition
instead, hence avoiding the device cache which is a correct
approach here.
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).
