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It could be actually better to use even cache origin in
read-only mode so there could no be some 'acidental'
change being done on this volume.
This however need further tools enhancment - where we would need
to handle whole subtree on 'lvchange -pr/-prw'.
When command calls backup() more then once (which is actually not
wanted) this warning message is shown repeatedly:
"WARNING: This metadata update is NOT backed up."
Instead now print message just once and less confuse user.
Add this functionality to lvconvert:
'lvconvert --thin cachedLV --thinpool vg/poll'
Converts cachedLV to external origin (which will be read-only).
New thin volume is created in thinpool LV and it's using external
origin as source for unprovisioned chunks.
This conversion happens online (while volume is in use).
Thin LV remains fully writable.
Cached external origin no longer could be written so cache will be used
ONLY for read operations. For this limitation we require cache mode
to be writethrough (as writeback cannot write to read-only volumes).
When thinLV is later removed cached external origin is again
fully usable, just note, LV remain in 'read-only' mode.
When read-write is needed, 'lvchange -prw' has to be used.
Single external origin could be user by multiple thinLV in
multiple differen thin pool.
When cache volume may be converted from normal to -real layer LV
we need to improve logic for call cache_check.
With this patch, we register call for cache_check only when metadata LV
is not yet present in active table slot (should match initial table
load).
This avoids unwanted checking when cache would become layer device
online.
The system is likely in some very inconsisten state.
Do not try to make it even more problematic with trying
to invoke tools like thin_check via callback.
External origin could be reloaded via more locks.
It's actually even more complex then thin-pool,
as it may be active on more nodes for linear LVs
(and maybe even more types).
External origin is always read-only thus unmodifiable
device so there should not be a problem accesing it
through multiple nodes.
Also for thin-pool check first presence of active thin-pool.
FIXME:
It's not easy to detect on which nodes this device is active
Thus manipulation with such device may require checking every
node and it active state and refresh.
But since such setup is quite complex to prepare and use,
hopefully there are not user trying to 'explore' this usage yet.
To be ready to show status of cache volume, call the status
with layer. Layer is automatically detected in this case when
cache volume is used in 'layered' form (needs -real suffix).
Avoid printing misleading message about single dirty block.
Instead properly detect condition where the 'cleaner' policy
needs to be installed without 'overloading' dirty variable.
Also print warning if we would be clearing read-only volume.
(it really shouldn't happen).
External origin could be activated as stand-alone device.
When the last thin LV is removed, external origin is no longer
the external origin and it's layer property was dropped.
Ensure dm table is correct by reloading external origin
(when it's active).
When LV is external origin, show info for LV but
status for -layer. So we expose more info to a user
as otherwise active external origin is only linear
mapping of -real layer.
We do the same for i.e. old snaphost origin.
Activation of raid has brough up also splitted image with tracing
(without taking lock for this).
So when raid is now activate - such image is not put into
table (with _rmeta). When user needs such device, just active it.
When --count=0 interval numbers are miscalculated:
Interval #18446744069414584325 time delta: 999920887ns
Interval #18446744069414584325 current err: -79113ns
End interval #18446744069414584325 duration: 999920887ns
This is because the command line argument is cast through the
uint32_t type, and fixed to UINT32_MAX:
_count = ((uint32_t)_int_args[COUNT_ARG]) ? : UINT32_MAX;
We also need to handle --count=0 specially when calculating the
interval number: since intervals count from #1, this must account
for the implicit "minus one" when converting from zero to the
UINT64_MAX value used (which is too large to store in _int_args).
The time management code mixes tests of the _timer_fd value with
code that should be timer agnostic: this causes problems for users
of the usleep() timer, since it cannot properly detect the start
of a new interval:
Beginning first interval
Interval #18446744069414584348 time delta: 1000000000ns
Interval #18446744069414584348 current err: 0ns
End interval #18446744069414584348 duration: 1000000000ns
Adjusted sample interval duration: 1000000000ns
[...]
Beginning first interval
Interval #18446744069414584349 time delta: 1000000000ns
Interval #18446744069414584349 current err: 0ns
End interval #18446744069414584349 duration: 1000000000ns
Adjusted sample interval duration: 1000000000ns
Separate these out, by defining a _timer_running() call that each
timer implements, and only define _timer_fd if we are compiling
with TIMERFD enabled.
Although the usleep() interval timer is not used if the Linux
TIMERFD interface is available it should still provide reasonably
good timing.
Instead of trying to estimate the error from the duration of the
last sleep, peg it to the start time of the program, and use the
value of ((start_time - now) % interval) to correct the current
interval duration.
This always pulls us back into sync at the end of each interval,
rather than relying on trying to incrementally adjust the time
duration at each interval start.
This greatly reduces drift when the usleep() clock is used.
The dm_bit_copy() macro uses the source (bs1) bitset size as the
limit for memcpy:
memcpy((bs1) + 1, (bs2) + 1, ((*(bs1) / DM_BITS_PER_INT) + 1)..)
This is safe if the destination bitset is smaller than the source,
or if the two bitsets are of the same size.
With a destination that is larger (e.g. when resizing a bitmap to
add more capacity), the memcpy will overrun the source bitset and
set garbage bits in the destination.
There are nine uses of the macro currently (8 in libdm/regex, and
1 in daemons/cmirrord): in each case the two bitsets are always of
equal size so the behaviour is unchanged.
Fix the macro to use bs2's size to simplify resizing bitsets and
avoid the need for another copy macro.
Commit 0690392040 revealed a problem
in raid metadata manipulation.
We do two operations in one table reload:
- raid leg/image extraction
- rename remaining raid legs
This should be made in separate steps. Otherwise we do an
uncorrectable table change on error path (leaving tables
for admin and dmsetup).
As a hotfix - restore the previous logic and use a single
new function _lv_update_and_reload_list which activates exclusively
extracted LVs on the list before resuming suspended raid LV.
This restore 'rename' functionality upon resume.
Also still preserve the 'origin_only' logic - although we know
it's not working properly for cluster and LV stacking.
Further fixes are needed.
If FIEMAP returns a single extent after the first call, no extent
boundary is detected and the first extent is not counted by the
normal mechanism.
In this case, increment nr_extents at the same time the extent is
added to the region table, before returning.
backup is not 'tested' for success and also it should
actually happen just when command is finished.
We do not target to make backups with each inter-step
metadata change.
RAID is LV property
TODO: only 2 flags are seg->status: PVMOVE & MERGING
At least the second one should be soon elimanted as again
we merge LV not a segment.
This is another place for 'common' use pattern or
reload and activation of deleted devices.
(Moving the exclusive activation to _deactivate_and_remove_lvs()).
TODO: looks like halve of raid function is reloading
just 'origin' - and the other full LV.
It's useful to be able to specify a minimum number of bits for a
new bitmap parsed from a list, for e.g. to allow for expansing a
group without needing to copy/reallocate the bitmap.
Add a backwards compatible symbol for programs linked against old
versions of the library.
It is sometimes convenient to iterate over the set bits in a dm
bitset in reverse order (from the highest set bit toward zero), or
to quickly find the last set bit.
Add dm_bit_get_last() and dm_bit_get_prev(), mirroring the existing
dm_bit_get_first() and dm_bit_get_next().
dm_bit_get_prev() uses __builtin_clz when available to efficiently
test the bitset in reverse.
Add a macro for the clz (count leading zeros) operation.
Use the GCC __builtin_clz() for clz() if it is available and fall
back to a shift based implementation on systems that do not set
HAVE___BUILTIN_CLZ.
Split out the loop that iterates over each batch of FIEMAP
extent data from the function that sets up and calls the ioctl
to reduce nesting and simplify local variable use:
_stats_get_extents_for_file()
-> _stats_map_extents()
The _stats_map_extents() function is responsible for detecting
eof and extent boundaries and adding whole, allocated extents
to the file extent table for region creation.
Check that all region_id values specified in a group bitmap are
actually present: although this should not normally happen when
using the dmstats tool, it is possible as a result of manual
changes (or bugs) for a group descriptor to contain one or more
group_id values that do not exist.
Check for this situation when reading group descriptors, warn
the user the user, and clear these bits in the bitmap when
formatting it for output.
If a region has a a DMS_GROUP tag in aux_data where the first
region_id in the bitmap is not the same as the containing region,
dmstats will segfault:
# '2' is never a valid group bitset list for region_id == 0
# dmsetup message vg_hex/root 0 "@stats_set_aux 0 DMS_GROUP=img:2#"
# dmsetup message vg_hex/root 0 "@stats_list"
0: 45383680+16384 16384 dmstats DMS_GROUP=img:2#
1: 46071808+32768 32768 dmstats -
2: 47382528+16384 16384 dmstats -
# dmstats list
Segmentation fault (core dumped)
The crash will occur in some arbitrary dm_stats_get_* property
method - this happens while processing the 1st region_id in the
bitset, because the region is marked as grouped, but there is
no group bitmap present at dms->groups[2]->regions.
Fix this by detecting a mismatch between the expected region_id
and dm_bit_get_first() for the parsed bitset during
_parse_aux_data_group().
Handle files that contain multiple logical extents in a single
physical extent properly:
- In FIEMAP terms a logical extent is a contiguous range of
sectors in the file's address space.
- One or more physically adjacent logical extents comprise a
physical extent: these are the disk areas that will be mapped
to regions.
- An extent boundary occurs when the start sector of extent
n+1 is not equal to (n.start + n.length).
This requires that we accumulate the length values of extents
returned by FIEMAP until a discontinuity is found (since each
struct fiemap_extent returned by FIEMAP only represents a single
logical extent, which may be contiguous with other logical
extents on-disk).
This avoids creating large numbers of regions for physically
adjacent (logical) extents and fixes the earlier behaviour which
would only map the first logical extent of the physical extent,
leaving gaps in the region table for these files.
