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Support error_if_no_space feature for thin pools.
Report more info about thinpool status:
(out_of_data (D), metadata_read_only (M), failed (F) also as health
attribute.)
Add new dm_report_compact_fields function to cause report outout
(dm_report_output) to ignore fields which don't have any value set
in any of the rows reported. This provides support for compact report
output where only fields which have something to report are displayed.
The dm_report_set_output_selection was not implemented in the end -
we have dm_report_init_with_selection instead. This is just a remnant
from development code that got into libdevmapper.h by mistake.
Support new PASSTHROUGH 'feature' flag.
Add dm_config_node to pass in policy args.
Really use origin_uuid instead of using extra call
to pass seg_areas.
Switch to 64bit feature flag bit set so there is
enough space in future for new bits...
When transaction_id is set 0 for thin-pool, libdm avoids validation
of thin-pool, unless there are real messages to be send to thin-pool.
This relaxes strict policy which always required to know
in front transaction_id for the kernel target.
It now allows to activate thin-pool with any transaction_id
(when transaction_id is passed in)
It is now upto application to validate transaction_id from life
thin-pool volume with transaction_id within it's own metadata.
Some values are reserved for special purpose like 'undefined', 'unmanaged' etc.
When using >, <, >= and < comparison operators where the range is considered,
do not include reserved values as proper values in this range which
would otherwise result in not so obvious criteria match (as the reserved value is
actually transparent for the user). It's incorrect.
Example scenario:
$ vgs -o vg_name,vg_mda_copies vg1 vg2
VG #VMdaCps
vg1 1
vg2 unmanaged
The "unmanaged" is actually mapped onto reserved value
18446744073709551615 (2^64 - 1) internally.
Such reseved value is already caught on selection criteria input
properly:
$ vgs -o name,vg_mda_copies vg1 vg2 -S 'vg_mda_copies=18446744073709551615'
Numeric value 18446744073709551615 found in selection is reserved.
However, we still need to fix situaton where the reserved value may be
included in resulting range:
Before this patch:
$ vgs -o vg_name,vg_mda_copies vg1 vg2 -S 'vg_mda_copies >= 1'
VG #VMdaCps
vg1 1
vg2 unmanaged
With this patch applied:
$ vgs -o vg_name,vg_mda_copies vg1 vg2 -S 'vg_mda_copies >= 1'
VG #VMdaCps
vg1 1
From the examples above, we can see that without this patch applied,
the vg_mda_copies >= 1 also matched the reserved value 18446744073709551615
(which is represented by the "unamanged" string on report). When
applying the operators, such values must be skipped! They're meant to
be matched only against their string representation only, e.g.:
$ vgs -o name,vg_mda_copies vg1 vg2 -S 'vg_mda_copies=unmanaged'
VG #VMdaCps
vg2 unmanaged
...or any synonyms:
$ vgs -o name,vg_mda_copies vg1 vg2 -S 'vg_mda_copies=undefined'
VG #VMdaCps
vg2 unmanaged
This is probably better approach than 3880ca5eca.
If dm module is not loaded during dm_is_dm_major call, there are no
lines for dm in /proc/devices, of course. Normally, dm_is_dm_major
is called to check existing devices, hence if module is not loaded,
we can expect there's no DM device present at the same time so we
can directly return 0 here (meaning the major number being inspected
is not dm device's one).
See also https://bugzilla.redhat.com/show_bug.cgi?id=1059711.
For dm_is_dm_major to determine whether the major number given as
an argument belongs to a DM device, libdm code needs to know what
the actual DM major is to do the comparison.
It may happen that the dm-mod module is not loaded during this
call and so for the completness let's try our best before we start
giving various errors - we can still make use of dm-mod autoloading,
though only since kernels 2.6.36 where this feature was introduced.
Add extra safety detection for thin pool transaction id
and query pool status after confirmed message.
In case there is a missmatch, immeditelly abort further
processing.
This patch adds a new flag --deferred to dmsetup remove. If this flag is
specified and the device is open, it is scheduled to be deleted on
close.
struct dm_info is extended.
The existing dm_task_get_info() is converted into a wrapper around the
new version dm_task_get_info_with_deferred_remove() so existing binaries
can still use the old smaller structure.
Recompiled code will pick up the new larger structure.
From: Mikulas Patocka <mpatocka@redhat.com>
Using "[ ]" operator together with "&&" (or ",") inside causes the
string list to be matched if and only if all the items given match
the value reported and the number of items also match. This is
strict list matching and the original behaviour we already have.
In contrast to that, the new "{ }" operator together with "&&" inside
causes the string list to be matched if and only if all the items given
match the value reported but the number of items don't need to match.
So we can provide a subset in selection criteria and if the subset
is found, it matches.
For example:
$ lvs -o name,tags
LV LV Tags
lvol0 a
lvol1 a,b
lvol2 b,c,x
lvol3 a,b,y
$ lvs -o name,tags -S 'tags=[a,b]'
LV LV Tags
lvol1 a,b
$ lvs -o name,tags -S 'tags={a,b}'
LV LV Tags
lvol1 a,b
lvol3 a,b,y
So in the example above the a,b is subset of a,b,y and therefore
it also matches.
Clearly, when using "||" (or "#") inside, the { } and [ ] is the
same:
$ lvs -o name,tags -S 'tags=[a#b]'
LV LV Tags
lvol0 a
lvol1 a,b
lvol2 b,c,x
lvol3 a,b,y
$ lvs -o name,tags -S 'tags={a#b}'
LV LV Tags
lvol0 a
lvol1 a,b
lvol2 b,c,x
lvol3 a,b,y
Also in addition to the above feature, fix list with single value
matching when using [ ]:
Before this patch:
$ lvs -o name,tags -S 'tags=[a]'
LV LV Tags
lvol0 a
lvol1 a,b
lvol3 a,b,y
With this patch applied:
$ lvs -o name,tags -S 'tags=[a]'
LV LV Tags
lvol0 a
In case neither [] or {} is used, assume {} (the behaviour is not
changed here):
$ lvs -o name,tags -S 'tags=a'
LV LV Tags
lvol0 a
lvol1 a,b
lvol3 a,b,y
So in new terms 'tags=a' is equal to 'tags={a}'.
2.02.106 added suffixes to some LV uuids in the kernel.
If any of these LVs is activated with 2.02.105 or earlier,
and then a later version is used, the LVs appear invisible and
activation commands fail.
The code now has to check the kernel for both old and new uuids.
We have "help" and "?" defined as implicit fields now. As such, we
don't need to export these names in libdevmapper (as it was introduced
by commit 7c86131233 within this release).
If anyone uses these field names by mistake, the libdevmapper code can
error out correctly if it detects that the set of explicit field names
(the ones supplied by "fields" arg in dm_report_init/dm_report_init_with_selection)
contains any of the implicit field names (the ones defined internally
by libdevmapper itself).
Making "help" and "?" implicit also simplifies code since the
dm_report_init caller (lvm/dmsetup) doesn't need to check on
dm_report_init return whether "help" or "?" was hit while parsing
fields/sort keys in libdevmapper.
The libdevmapper now sets internal "RH_ALREADY_REPORTED" flag
after it reports the "help" or "?" implicit field. Then libdevmapper
itself checks for this flag in dm_report_object and if found,
the actual reporting is skipped (because the "help" implicit field
was reported instead of the actual report).
Ordering string list items on reports is also new compared to
previous state where items were not ordered at all and they
got reported simply as they appeared/were processed.
Warn when --udevcookie/DM_UDEV_COOKIE is used with 'dmsetup remove --force'.
When command is doing multiple ioctl operations on a single device,
it may invoke udev activity, that is colliding with further ioctl commands.
The result of such operation becomes unpredictable.
Use of --retry could partially help...
Share DM_REPORT_FIELD_RESERVED_NAME_{HELP,HELP_ALT} between libdm and
any libdm user to handle reserved field names, in this case the virtual
field name to show help instead of failing on unrecognized field.
The libdm user also needs to check the field name so it can fire
proper code in this case (cleanup, exit etc.).
If there ever would be a second call to dm_lib_init()
and envvar would be improperly set, some last set value
would be used while it should reset to default mangling mode.
When the node enters dtree with implicit dependency, it
automatically has udev flags from parent node
and could not be changed later when the node has been
entered again via i.e lvm's preload tracking.
Resolve this by tracking whether the node has been
created by implicit dependency tracking or has been
entered explicitely. Implicit node could be later
upgraded by an explicit _add_dev() with proper udev_flags.
For implicit devices add special udev flags to avoid
any scan and udev rule processing if we resume such device.
Patch allows easier removing of orphan nodes.
When the last entry in the timeout queue is unregistered,
wakeup sleeping condition, so the thread is deleted earlier.
So the thread resource is release earlier.
Also when monitored with tools like valgrind this eliminites reported
leak.
Individual events are handled through separate threads,
so once we have more then a single thread in this eventwait
sleeping, we got race on the dm_log setting, since
if one event is timeout out on alarm, while another is still waiting,
then dm log has been restored to NULL and the next sigalarm
has been reported as error.
Fix it by introducing counter which is protected via mutex,
and only when the last event is released, logging is restored.
TODO: libdm seems to have some static vars which may audit
for this type of use.
Reuse _node_send_messages for just checking
for valid transaction_id with preload.
This allows earlier detection of incosistent thin pool.
Code does the same thing, except for sending messages.
Improve testing of transation_id to not allow other difference
then either kernel TID is equal or is lower by oned and there
are queued messages for transaction.
Mark messages as submitted if the transaction_id is already matching.
Do not try to deactivate node on failure here and leave it on
proper error path of the caller.
Add internal error warning when string value is used
as sort value for numerical field.
Using log_warn since the function itself does not return error,
so we do not confuse log_error() checker.
Send error message on stdout, since after _display_info_long()
command return errors.
Patch makes consistent behavior for command:
dmsetup info -c non-existing-dev
&
dmsetup info non-existing-dev
Now both commands report error on stderr when they return error status
for non-existing device.
On modern systems udev manages nodes in /dev/mapper directory.
It creates, deletes and renames the nodes according to the
state of the kernel driver.
When the dmsetup is compiled without udev support (--enable-udev_sync)
and runs on the system with running udevd it tries to manage nodes in
/dev/mapper too, so it can race with udev.
dmsetup checks if the node was created/deleted/renamed with the stat
syscall, and skips the operation if it was. However, if udev
creates/deletes/renames the node after the stat syscall and before the
mknod/unlink/rename syscall, dmsetup reports an error.
Since in the system everything happened as expected, skip reporting
error for such case.
These races can be easily provoked by inserting sleep at appropriate
places.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
This file may be included by other programs, so it should be compliant
with the C standard.
* use __linux__ instead of linux - __linux__ is always defined, linux is
not defined when gcc runs in standard-compliant mode (with -std=c89 or
-std=c99) because the C standard doesn't allow polluting namespace
with arbitrary defines.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Just like we have symbolic names assigned to general DM udev flags
(DM_UDEV_* flags), we have the same for any subsystem flags now
(DM_SUBSYSTEM_UDEV_FLAG*), making it easier to use.
Each subsystem rule that needs to import any of DM_SUBSYSTEM_UDEV_FLAG*
flags is responsible for doing so. This simply moves control of these
flags from general 10-dm.rules to any subsystem rule using these flags
as each subsystem knows better how to handle these flags on its own.
Do not allow passing '' names to kernel.
This test was missing also in kernel, so it has allowed
to create device with '' name. This then confused dmsetup tool,
since such name is unexpected and unsupported. To remove
such name from table, user has to use -j -m to specify which device
should be removed.
This patch fixes the posibility to run this operation:
dmsetup rename existingdev ''
after this operation commands like 'dmsetup table' are failing.
This patch prohibits to use such name.
Recent kernels allow messages to respond with a string.
Add dm_task_get_message_response() to libdevmapper to perform some
basic sanity checks and return this.
Have 'dmsetup message' display any response.
DM statistics will make extensive use of this.
(From Mikulas.)
84 files changed, 1540 insertions(+), 442 deletions(-)
Mostly bug fixes this time.
Also note:
md raid replaces dm mirroring as the default implementation.
Can call out to thin_repair to fix thin metadata.
Improved clvmd error detection/debugging information.
Support tests with abort when libdm encounters internal
error - i.e. for dmsetup tool.
Code execution will be aborted when
env var DM_ABORT_ON_INTERNAL_ERRORS is set to 1
363 files changed, 19863 insertions(+), 9055 deletions(-)
This is a very large release - so expect bugs!
Please treat this release like a release candidate.
Changes to the external interfaces since 2.02.98 are not yet frozen.
Updated releases will follow quickly (days not weeks) as any problems
are handled.
Clear send_messages flag when they have been delivered successfully.
There is no need to validate it for all other activations of the same
node in the dm_tree.
Also add extra debug message which shows the reason for skipping
sending of messages because the transaction_id has already the matching
value.
Instead of calling syslog() from signal event handler,
run all logging code in the main loop.
Also it needs to take the lock and check for list
only when really needed.
Switch to use libdm dm_get_status_snapshot() function for
reading status info.
This fixes bug, where the code was using 32bit integers,
while the snapshot target is able to return 64bit sizes.
However this also means, someone is using >1TB snapshot
cow devices, which is actually very bad idea anyway, since the
perfomance and memory usage in this case is very bad.
To detect mounted device, use also /proc/self/mountinfo
as so far the check was only able to detect ext4 mounted filesystem.
TODO:
Once proper testing for this feature is added, it may appear,
mountinfo check is enough and covers all cases and sysfs check
could be removed.
Sharing char* with field has a problem in error path,
when we allocate event, but fail to allocate timeout string.
Instead of creating complicated error paths to resolve
it individually stop using unions, and let the resource
to be released in a simple _free_message().
This was a regression introduced with e33fd978a8
(libdm v1.02.68/lvm2 v2.02.89) with the introduction of new output
fields blkdevname and blkdevs_used for ls and deps dmsetup commands.
A new common '_process_options' fn was added with that commit, but the
fn was called prematurely which then broke processing of
'dmsetup splitname -o' which should implicitly use '-c' option
and this was failing after the commit:
alatyr/~ $ dmsetup splitname -o lv_name /dev/mapper/vg_data-test
Option not recognised: lv_name
Couldn't process command line.
The '-c' had to be used for correct operation:
alatyr/~ $ dmsetup splitname -c -o lv_name /dev/mapper/vg_data-test
LV
test
Now fixed to work as it did before:
alatyr/~ $ dmsetup splitname -o lv_name /dev/mapper/vg_data-test
LV
test
When a section was empty in a configuration tree (no children - this is
allowed) and we were looking for a config node inside that section, the
_find_config_node function incorrectly returned the section itself if
the node inside that section was not found.
For example the configuration below:
The config:
abc {
}
And a function call to get the "def" node inside "abc" section:
_find_config_node(..., "abc/def")
...returned the "abc" node instead of NULL ("def" not found).
This in turn caused segfaults in the code using lookups in such
a configuration tree as we (correctly) expected that the node
returned was always the one we were looking for or NULL if not
found. But if incorrect node was returned instead, we processed
that as if this was the node we were looking for and so we
processed its value as well. But sections don't have values => segfault.
This patch fixes problem reported here:
https://www.redhat.com/archives/dm-devel/2013-January/msg00311.html
Fixing it by separating function for duplicating string token.
---
When /etc/lvm/lvm.conf is truncated at the first '"' of a line, all LVM
utilities crash with a segfault.
The segfault only seems to occur if the last character is the first '"'
(double quote) of a line. If you truncate it at any other point, lvm
detects the error and report parse error
lvm.conf ends like this.
$hexdump -C lvm.conf
....
69 72 20 3d 20 22 2f 64 65 76 22 0a 0a 0a 20 20 |ir = "/dev"... |
20 20 23 20 41 6e 20 61 72 72 61 79 20 6f 66 20 | # An array of |
64 69 72 65 63 74 6f 72 69 65 73 20 74 68 61 74 |directories that|
20 63 6f 6e 74 61 69 6e 20 74 68 65 20 64 65 76 | contain the dev|
69 63 65 20 6e 6f 64 65 73 20 79 6f 75 20 77 69 |ice nodes you wi|
73 68 0a 20 20 20 20 23 20 74 6f 20 75 73 65 20 |sh. # to use |
77 69 74 68 20 4c 56 4d 32 2e 0a 20 20 20 20 73 |with LVM2.. s|
63 61 6e 20 3d 20 5b 20 22 2f 78 22 2c 0a 20 20 |can = [ "/x",. |
20 20 20 20 20 20 20 20 20 20 20 22 | "|
...
Reported-by: dongmao zhang <dmzhang suse com>
If the resume of preloaded node fails, do not leave such
node in the table - since it may not be easy to detach such
node later when the node is i.e. internal.
i.e. failing activation of the thin pool with mismatching
chunk size may leave -tpool device in the table, which
could have been then removed only by dmsetup command.
Setting this environment variable will cause a full fallback
to old direct node and symlink management in libdevmapper and lvm2.
It means:
- disabling udev synchronization
(--noudevsync in dmsetup and --noudevsync + activation/udev_sync=0
lvm2 config)
- disabling dm and any subsystem related udev rules
(--noudevrules in dmsetup and activation/udev_rules=0 lvm2 config)
- management of nodes/symlinks under /dev directly by libdevmapper/lvm2
(--verifyudev in dmsetup and activation/verify_udev_operations=1
lvm2 config)
- not obtaining any device list from udev database
(devices/obtain_device_list_from_udev=0 lvm2 config)
Note: we could set all of these before - there's no functional change!
However the DM_DISABLE_UDEV environment variable is a nice shortcut
to make it easier for libdevmapper users so that one can switch off all
of the udev management off at one go directly on the command line,
without a need to modify any source or add any extra switches.
cookie_set variable found in the struct dm_task should be always
set to 1 after dm_task_set_cookie_call, even if udev_sync is disabled
as the cookie itself carries synchronization informations *as well as*
extra flags to control other aspects of udev support.
For example, one could disable the synchronization itself, but still
direct the libdm code to disable library fallback via
DM_UDEV_DISABLE_LIBRARY_FALLBACK flag. These extra flags still need
to be carried out!
A concrete example:
$ dmsetup create test --table "0 1 zero" --noudevsync
This disables synchronization with udev. As the --verifyudev option is
not used, we don't want to do any corrections. In other words, we
need DM_UDEV_DISABLE_LIBRARY_FALLBACK flag to be used. However,
with --noudevsync this was not the case - the flag was ignored!
This patch fixes the case when noudevsync is used but there are still
some extra flags passed within the cookie flag part. The synchronization
part of the cookie stays zero (which is ok as dm_udev_wait call on such a
cookie is simply a NOOP).
Reset counter after thin pool resize failure.
If the pool goes above threshold, support unmounting
of all thin volumes if the lvextend fails to avoid
overfilling of the pool.
Patch clears the flag if thin pool is stacked over mirror.
Since thin pool could be used to stack device over mirrors,
it needs resume properly i.e. mirrors with corelog which are otherwise
unconditionally skipped (for pvmove functionality).
If we were defining a section (which is a node without a value) and
the value was created automatically on dm_config_create_node call,
we were wasting resources as the next step after creating the config
node itself was assigning NULL for the node's value.
The dm_config_node_create + dm_config_create_value sequence should be
used instead for settings and dm_config_node_create alone for sections.
The majority of the code already used the correct sequence. Though
with dm_config_node_create fn creating the value as well, the pool
memory was being trashed this way.
This patch removes the node value initialization on dm_config_create_node
fn call and keeps it for the direct dm_config_create_value fn call.
A regression introduced in 2.02.89 (11e520256b)
caused the lvm dumpconfig <node> to print out
the node as well as its subsequent siblings.
The information about "only_one" mode got lost.
Before this patch (just an example node):
# lvm dumpconfig global/use_lvmetad
use_lvmetad=1
thin_check_executable="/usr/sbin/thin_check"
thin_check_options="-q"
(...all nodes to the end of the section)
With this patch applied:
# lvm dumpconfig global/use_lvmetad
use_lvmetad=1
Remove executable path detection in udev rules and use sbindir that
is configured, but still provide the original functionality by means
of 'configure --enable-udev-rule-exec-detection'.
Normally, the exec path for the tools called in udev rules should
not differ from the sbindir used, however, there are cases this is
necessary. For example different environments could be assembled
in a way that these path differ for some reason (distribution installer,
initrd ...).
This functionality is kept for compatibility only. Any environment
moving the binaries around and using different paths should be fixed
eventually!
There were several hard-coded values for run directory around the code.
Also, some tools are DM specific only, others are LVM specific and there
was no distinction made here before. With this patch applied, we have
this cleaned up a bit (subsystem in brackets, defaults in parentheses):
[common] configurable PID_DIR (/var/run)
lvm [lvm] configurable RUN_DIR (/var/run/lvm)
configurable locking dir (/var/lock/lvm)
clvmd [lvm] configurable pid file (PID_DIR/clvmd.pid)
socket (RUN_DIR/clvmd.sock)
lvmetad [lvm] configurable pid file (PID_DIR/lvmetad.pid)
socket (RUN_DIR/lvmetad.socket)
dm [dm] configurable DM_RUN_DIR (/var/run)
cmirrord [dm] configurable pid file (PID_DIR/cmirrord.pid)
dmeventd [dm] configurable pid file (PID_DIR/dmeventd.pid)
server fifo (DM_RUN_DIR/dmeventd-server)
client fifo (DM_RUN_DIR/dmeventd-client)
The changes briefly:
- added configure --with-default-pid-dir
- added configure --with-default-dm-run-dir
- added configure --with-lvmetad-pidfile
- by default, using one common pid directory for everything
(only lvmetad was not following this before)
With latest changes in the udev, some deprecated functions were removed
from libudev amongst which there was the "udev_get_dev_path" function
we used to compare a device directory used in udev and directore set in
libdevmapper. The "/dev" is hardcoded in udev now (udev version >= 183).
Amongst other changes and from packager's point of view, it's also
important to note that the libudev development library ("libudev-devel")
could now be a part of the systemd development library ("systemd-devel")
because of the udev + systemd merge.
In some occasional case dmevent restart was experiencing problems
with obtaining pid lockfile. So this patch tries to send several more kill
message until daemon kills itself so there is would reponse.
With this small loop the restart seems to work reliable,
although the loopsize and usleep are just randomly picked for now.
Just to make it clearer since there is the "dmsetup info -c -o blkdevname"
as well that shows the "block device name for this mapping", having a
"BlkDevName" header on output.
It's a bit confusing then if the "dmsetup info -c -o devs_used,blkdevs_used"
is named with a plural "DevNames"/"BlkDevNames" but at the same time having
a totally different meaning than the singular form "BlkDevName".
DevNames --> DevNamesUsed
BlkDevNames --> BlkDevNamesUsed
...makes it much more comprehensible.
LISTEN_PID and LISTEN_FDS environment variables are defined only during systemd
"start" action. But we still need to know whether we're activated during
"reload" action as well - we use the reload action to call "dmeventd -R"/"lvmetad -R"
for statefull daemon restart. We can't use normal "restart" as that is simply
composed of "stop" and "start" and we would lose any state the daemon has.
Auto mode can't deal with multiple mangled names. We can do that while working
in hex mode, but in auto mode, this would lead to device name ambiguity.
Be more strict when unmangling names on ioctl return - require the name to be
properly mangled in 'auto' and 'hex' mode. There really should not be any
blacklisted character since the names should be renamed already (by means of
renaming it directly or running 'dmsetup mangle' for automatic rename).
Avoid using NULL pointers from udev. It seems like some older versions of udev
were improperly returning NULL in some case, so do not silently break here,
and give at least a warning to the user.
Since lvm seems to call driver_version(NULL, 0) this would lead
to crash. Though the combination of the code is probably very hard to hit.
If the user doesn't supply version buffer, just skip printing to buffer.
pvcreate gives
WARNING: Ignoring unsupported value for metadata/pvmetadataignore.
It was warning if there is no config file entry instead of only if the node
exists but is empty.
Should be faster then strncpy - since we could avoid clearing 4KB pages
with each strncpy(...,PATH_MAX).
Also it's easy to check whether string fit - and eventually avoid
to continue working we incomplete string.
If we have good enough glibc to return number of needed chars, do not
loop try to reach good size, but use this size directly for allocation,
saving also last strdup.
Since now we start with 16 bytes - skip buffer realloc for shorter string.
We don't have anything better yet...
The problems the watch rule caused when removing devices should be covered
now with the "retry remove" logic. It's also better to have this maintained
by us, rather than having this rule anywhere else without proper control.
Device-mapper in kernel uses '\' as escape character so it's better
to double it to avoid any confusion when using existing device names
with '\' in the table specification.
For example:
dmsetup create x --table "0 8 linear /dev/mapper/a\x20b 0"
should pass just fine now without a need to explicitly escape the '\' char
like this:
dmsetup create x --table "0 8 linear /dev/mapper/a\\x20b 0"
dm_task_get_name_mangled will always return mangled form of the name while
the dm_task_get_name_unmangled will always return unmangled form of the name
irrespective of the global setting (dm_set/get_name_mangling_mode).
This is handy in situations where we need to detect whether the name is already
mangled or not. Also display functions make use of it.
If dm_task_set_name/newname is called, the name provided will be
automatically translated to correct encoded form with the hex enconding
so any character not on udev whitelist will be mangled with \xNN
format where NN is hex value of the character used.
By default, the name mangling mode used is the one set during
configure with the '--with-default-name-mangling' option.
This option configures the default name mangling mode used, one of:
AUTO, NONE and HEX.
The name mangling is primarily used to support udev character whitelist
(0-9, A-Z, a-z, #*-.:=@_) so any character that is not on udev whitelist
will get translated into an encoded form \xNN where NN is the hex value
of the character.
