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When mapping regions to a file descriptor, a temporary table of
extent descriptors is built using the dm_pool object building
interface.
Previously this use borrowed the dms->mem region and counter
table pool (since nothing can interleave with the allocation
while the caller is still in dm_stats_create_regions_from_fd()).
This turns out to be problematic for error recovery. When a
region creation operation fails partway through file mapping,
we need to roll back the set of already created regions and
this requires a listed handle: the dm_stats_list() will then
allocate from the same pool as the extents; we either have
to throw away valid list data, or leak the extent table, to
return the handle in a valid state.
Avoid this problem by creating a new, temporary mem pool in
_stats_create_file_regions() to hold the extent data, and
discarding it on exit from the function.
While cleaning up the table of already created regions during a
failed dm_stats_create_regions_from_fd(), list the handle once,
and call _stats_delete_region() directly. This avoids sending a
@stats_list message for each region deleted, reducing runtime
from 6s to 0.7s when cleaning up ~250 out of ~10000 regions:
# time dmstats create --filemap b.img
device-mapper: message ioctl on (253:0) failed: Cannot allocate memory
Failed to create region 246 of 309 at 9388032.
Could not create regions from file /root/b.img
<< pauses here >>
Command failed
real 0m6.267s
user 0m3.770s
sys 0m2.487s
# time dmstats create --filemap b.img
device-mapper: message ioctl on (253:0) failed: Cannot allocate memory
Failed to create region 246 of 309 at 9388032.
Could not create regions from file /root/b.img
Command failed
real 0m0.716s
user 0m0.034s
sys 0m0.581s
Testing the error path requires region creation to start to
fail part way through the operation (in order to have regions
to clean up): the simplest way is to ensure the system is
close to the kernel limit of 1/4 RAM or 1/2 vmalloc space
consumed by dmstats data.
Split dm_stats_delete_region() so that internal callers can manage
the handle state themselves.
dm_stats_delete_region() now just handles checking the state of the
handle, reporting validation errors, and calling dm_stats_list() if
necessary, before calling _stats_delete_region().
The new _stats_delete_region() function performs the actual group
member removal and region deletion, and requires a fully listed
handle to operate.
Callers that repeatedly delete regions can use a single listed
handle for many operations on the same device, avoiding one
message ioctl per region deleted: since @stats_list with many
regions is expensive, this yields large runtime improvements.
If we fail to create a region during dm_stats_create_regions_from_fd(),
we must remove all regions that were created to do this to date. This
needs to loop over the table of region_id values that were populated
by _stats_create_file_regions() before the error.
The code for this failure case in the out_remove branch incorrectly
uses the table index as the region_id:
for (--i; i != DM_STATS_REGION_NOT_PRESENT; i--) {
if (!dm_stats_delete_region(dms, i))
log_error("Could not delete region " FMTu64 ".", i);
}
This causes the cleanup code to delete a completely unrelated set
of regions (since the index here will always be nr_regions..0).
Fix it to pass the actual region_id stored in regions[i] instead.
Fix a silly bug in dm_stats_delete_region() that hugely inflates
runtimes when deleting a large number of regions.
For ~50,000 regions this change reduces the runtime from 98s to
6s on my test systems (a ~93% reduction).
The bug exists because dm_stats_delete_region() applies a truth
test to the return value of dm_stats_get_nr_areas(); this is
never correct usage - it will walk the entire region table and
calculate area counts for each region (which is roughly O(n^2)
in the number of regions, as dm_stats_delete_region() is being
called inside a region walk).
Although the individual area calculation is not that costly,
uselessly running anything 2,500,000,000 times over gets a bit
slow.
A much cheaper test (which is always true if the areas check is
true) is to just test dm_stats_get_nr_regions() or dms->regions;
if either is true it implies at least one area exists.
Old:
Performance counter stats for 'dmstats delete --allregions --alldevices':
98117.791458 task-clock (msec) # 1.000 CPUs utilized
127 context-switches # 0.001 K/sec
3 cpu-migrations # 0.000 K/sec
6,631 page-faults # 0.068 K/sec
307,711,724,562 cycles # 3.136 GHz
544,762,959,577 instructions # 1.77 insn per cycle
84,287,824,115 branches # 859.047 M/sec
2,538,875 branch-misses # 0.00% of all branches
98.119578733 seconds time elapsed
New:
Performance counter stats for 'dmstats delete --allregions --alldevices':
6427.251074 task-clock (msec) # 1.000 CPUs utilized
6 context-switches # 0.001 K/sec
0 cpu-migrations # 0.000 K/sec
6,634 page-faults # 0.001 M/sec
21,613,018,724 cycles # 3.363 GHz
3,794,755,445 instructions # 0.18 insn per cycle
852,974,026 branches # 132.712 M/sec
808,625 branch-misses # 0.09% of all branches
6.428953647 seconds time elapsed
Simplify info run for use only for INFO & STATUS.
Drop handling MKNODES within _info_run() call
and use more advanced _setup_task_run() directly.
This allows to further simplify _info_run().
Integrate also query for inactive table and
handle dm_task_run() and dm_task_get_info()
(thus switching to setup_task_run)
Add one exception case for DM_DEVICE_TARGET_MSG.
This allows further shortening and simplification of all
other users of this function.
It's actually not needed to call extra lv_has_target_type() to detect
snapshot merge is in progress - decode this right during status
capturing and save even few extra ioctl calls.
Drop LV from passed API arg - it's always segment being checked.
Also use_layer is now in full control of lv_info_with_seg_status().
It decides which device needs to be checked to get 'the most info'.
TODO: future version should be able to expose status from
Start moving selection of status taken for a LV into a single place.
The logic for showing info & status has been spread over multiple
places and were doing too complex decision going agains each other.
Unify selection of status of origin & cow scanned device.
TODO: in future we want to grab status for LV and layered LV and have
both statuses present for display - i.e. when 'old snapshot'
of thinLV is takes and there is ongoing merge - at some moment
we are not capable to show all needed info.
When lvm2 wants to see a status, it needs to validate,
segment for status reading is matching whan lvm2 expects in
metadata.
Also ensure status failure will not cause '0' from info reading
when actual info was collected properly.
Failure in 'status' reading is considered to be
a 'log_warn()' event only.
When we can't parse status, switch to warning as this is not
considered an errornous case. LVS is not supposed to return
error status code when device is not what it's been expected to
be - but it should be WARNING a user there is something unexpected.
Convert lvs -o lv_merge_failed,lv_snapshot_invalid to use
lv_info_and_status function.
This makes it equal to attr value showing this info
(as they were different since they were derived from
different data set and different logic as well).
Also saves couple extra ioctl that were needed to obtain this info.
When displaying <reporting_command> -o help, we'd like to have fields
grouped nicely, not starting having groups interleaved as it was before.
The code that displays the help output for fields takes the order as
written in columns.h file - this caused output like:
$ lvs -o help
Logical Volume Fields
---------------------
...field list...
Logical Volume Device Info and Status Combined Fields
-----------------------------------------------------
...field list...
Logical Volume Fields
---------------------
...field list...
Logical Volume Device Status Fields
-----------------------------------
...field list...
Logical Volume Fields
---------------------
...field list...
Instead, let's have it without groups interleaved which may be
a bit confusing, so:
Logical Volume Fields
---------------------
...field list...
Logical Volume Device Status Fields
-----------------------------------
...field list...
Logical Volume Device Info and Status Combined Fields
-----------------------------------------------------
...field list...
..and so on.
Use LVM_DBUSD_TEST_MODE env variable to customize what we test.
Default is the same where we try to test all combinations of all
modes. Renamed to make it consistent with the other env variables
that are used in the unit test.
- We check that all properties match the introspection data. We
don't verify values for every property as only lvm knows what they
should be.
- We are testing vg.Move
Added a properties changed signal on the job dbus object so that client
can wait for a signal that the job is complete instead of polling or
blocking on the wait method.
Allows the user to override the number of commands that get dumped
to the log when we encounter a lvm error. Also useful during
development when you don't want to see the blackbox output.
In case any SubLV of a RaidLV transiently fails, it needs
two "lvchange --refresh RaidLV" runs to get it to fully
operational mode again. Reason being, that lvm reloads all
targets for the RaidLV tree but doesn't resume the SubLVs
until after the whole tree has been reloaded in the first
refresh run. Thus the live mapping table of the SubLVs
still point to an "error" mapping and the dm-raid target
can't retrieve any superblock from the MetaLV(s) in processing
the constructor during this preload thus not discovering the
again accessible SubLVs. In the second run, the SubLV targets
map proper (meta)data, hence the constructor discovers those
fine now.
Solve by resuming the SubLVs of the RaidLV before
preloading the respective top-level RaidLV target.
Resolves: rhbz1399844
