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The copy of the VG which clvmd stashes in lvmcache should
not only be used between suspend and resume, but between
sequential LV operations in clvmd, so that clvmd does not
need to reread the VG for each one. Prepare for that by
renaming the stashed VG as "saved_vg".
The copy of VG metadata stored in lvmcache was not being used
in general. It pretended to be a generic VG metadata cache,
but was not being used except for clvmd activation. There
it was used to avoid reading from disk while devices were
suspended, i.e. in resume.
This removes the code that attempted to make this look
like a generic metadata cache, and replaces with with
something narrowly targetted to what it's actually used for.
This is a way of passing the VG from suspend to resume in
clvmd. Since in the case of clvmd one caller can't simply
pass the same VG to both suspend and resume, suspend needs
to stash the VG somewhere that resume can grab it from.
(resume doesn't want to read it from disk since devices
are suspended.) The lvmcache vginfo struct is used as a
convenient place to stash the VG to pass it from suspend
to resume, even though it isn't related to the lvmcache
or vginfo. These suspended_vg* vginfo fields should
not be used or touched anywhere else, they are only to
be used for passing the VG data from suspend to resume
in clvmd. The VG data being passed between suspend and
resume is never modified, and will only exist in the
brief period between suspend and resume in clvmd.
suspend has both old (current) and new (precommitted)
copies of the VG metadata. It stashes both of these in
the vginfo prior to suspending devices. When vg_commit
is successful, it sets a flag in vginfo as before,
signaling the transition from old to new metadata.
resume grabs the VG stashed by suspend. If the vg_commit
happened, it grabs the new VG, and if the vg_commit didn't
happen it grabs the old VG. The VG is then used to resume
LVs.
This isolates clvmd-specific code and usage from the
normal lvm vg_read code, making the code simpler and
the behavior easier to verify.
Sequence of operations:
- lv_suspend() has both vg_old and vg_new
and stashes a copy of each onto the vginfo:
lvmcache_save_suspended_vg(vg_old);
lvmcache_save_suspended_vg(vg_new);
- vg_commit() happens, which causes all clvmd
instances to call lvmcache_commit_metadata(vg).
A flag is set in the vginfo indicating the
transition from the old to new VG:
vginfo->suspended_vg_committed = 1;
- lv_resume() needs either vg_old or vg_new
to use in resuming LVs. It doesn't want to
read the VG from disk since devices are
suspended, so it gets the VG stashed by
lv_suspend:
vg = lvmcache_get_suspended_vg(vgid);
If the vg_commit did not happen, suspended_vg_committed
will not be set, and in this case, lvmcache_get_suspended_vg()
will return the old VG instead of the new VG, and it will
resume LVs based on the old metadata.
Whenever we make visible LV out of previously invisible one,
reload it's table - the is mandator for proper udev rule
processing as well as ensure content of dm table is correct.
TODO: this new generic rule probably make extra raid rules unnecessary.
When snapshot is created in read-only mode with 'lvcreate -s -pr...',
lvm2 still needs to be able to write to layered -cow volume
to store metadata and exceptions blocks.
TODO: in some case we might be able to do full tree with read-only
volume but this probably needs futher validation:
1. checking snapshot header already exist
2. origin & snapshot are both in read-only mode.
Occasionaly users may need to peek into 'component devices.
Normally lvm2 does not let users activation component.
This patch adds special mode where user can activate
component LV in a 'read-only' mode i.e.:
lvchange -ay vg/pool_tdata
All devices can be deactivated with:
lvchange -an vg | vgchange -an....
Introduce:
lv_is_component() check is LV is actually a component device.
lv_component_is_active() checking if any component device is active.
lv_holder_is_active() is any component holding device is active.
So this is a bit more complex and possibly worth futher checking.
ATM clvmd drops cmd->mem mempool AFTER refresh of cmd.
So anything allocating from cmd->mem during toolcontext init
will likely die at some point in time.
As a quick fix - just use regular malloc/free for 'dso' alloction.
It's worth to note - cmd->libmem seems to be often misused
causing hidden memleaking for clvmd.
Build dso plugin name during segtype initialisation and just
use the string during command life-time.
Also slightlt update message verbosity and make it very_verbose
when operation is going to be made and 'verbose' when it's done.
Avoid using same return code for reporting 2 different things
and stricly report error code by return value and add new
parameter for reporting monitoring status.
This makes easier to recognize which error we got from dm_event
and continue only with ENOENT.
In fact pvmove does support 'clustered-core' target for clustered
pvmove of LVs activated on multiple nodes.
This patch restores support for activation of pvmove on all nodes
for LVs that are also activate on all nodes.
Add protectional internall error whenever we spot activation
of 'exclusive' only segments in 'non-exclusive' mode.
TODO: possibly the activation locking could be enhanced to handle
this fully behind the scene - as for now this works purely for
lvchange/vgchange activation.
In case of failed legs, raid replaces those with
e.g. "vg-lv_rimage_0-missing_0_0" mapped to an error target.
Those errouneously remain on deactivation.
Fix by removing them on deactivation/removal of the RaidLV.
Check also all snapshosts when resume is requested,
the origin volume is already resume, but possibly
some subLV or snapshot LV could be suspended if
we are still in critical_section.
Only thin-pool with origin_only suspend is allowed to be not suspending anything.
In such case pairing resume will 'decrement' critical section counter.
Just like suspend handles preload for pvmove finish,
in similar way handle suspend of starting pvmove.
In this case the precommited metadata are checked for list of PVMOVEed
LVs and those are suspended in with committed metadata.
Whenever pvmove tree is going to be generated for suspend
and such LV has a user - use this 'using LV' to generate
correct dm tree holding all components.
LV is asked for resume, and its already resume and tool
is inside 'critical_section()' check if there is any suspended sub LV.
In that case 'resume' operation will not be skipped.
When old snapshot is merged, lvm2 still can report some data about
merged 'snapshot' - i.e. it occupied space in VG.
This patch fixes regression from commit:
6fd20be629
and resolved RHBZ: 1460161
In order to support striped raid5/6/10 LV reshaping (change
of LV type, stripesize or number of legs), this patch
introduces infrastructure prerequisites to be used
by raid_manip.c extensions in followup patches.
This base is needed for allocation of out-of-place
reshape space required by the MD raid personalities to
avoid writing over data in-place when reading off the
current RAID layout or number of legs and writing out
the new layout or to a different number of legs
(i.e. restripe)
Changes:
- add members reshape_len to 'struct lv_segment' to store
out-of-place reshape length per component rimage
- add member data_copies to struct lv_segment
to support more than 2 raid10 data copies
- make alloc_lv_segment() aware of both reshape_len and data_copies
- adjust all alloc_lv_segment() callers to the new API
- add functions to retrieve the current data offset (needed for
out-of-place reshaping space allocation) and the devices count
from the kernel
- make libdm deptree code aware of reshape_len
- add LV flags for disk add/remove reshaping
- support import/export of the new 'struct lv_segment' members
- enhance lv_extend/_lv_reduce to cope with reshape_len
- add seg_is_*/segtype_is_* macros related to reshaping
- add target version check for reshaping
- grow rebuilds/writemostly bitmaps to 246 bit to support kernel maximal
- enhance libdm deptree code to support data_offset (out-of-place reshaping)
and delta_disk (legs add/remove reshaping) target arguments
Related: rhbz834579
Related: rhbz1191935
Related: rhbz1191978
Add to commits 87117c2b25 and 0b8bf73a63 to avoid refreshing two
times altogether, thus avoiding issues related to clustered, remotely
activated RaidLV. Avoid need to repeat "lvchange --refresh RaidLV"
two times as a workaround to refresh a RaidLV. Fix handles removal
of temporary *-missing-* devices created for any missing segments
in RAID SubLVs during activation.
Because the kernel dm-raid target isn't able to handle transiently
failing devices properly we need
"[dm-devel][PATCH] dm raid: fix transient device failure processing"
as well.
test: add lvchange-raid-transient-failures.sh
and enhance lvconvert-raid.sh
Resolves: rhbz1025322
Related: rhbz1265191
Related: rhbz1399844
Related: rhbz1404425
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).
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.
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.
Translate log_info() into log_very_verbose() which is macro
supposed to be used by our code.
log_info() is internal macro with eventually some 'symbolic' meaning
in syslogging daemons.
Check for dm-raid target version with non-standard raid4 mapping expecting the dedicated
parity device in the last rather than the first slot and prohibit to create, activate or
convert to such LVs from striped/raid0* or vice-versa in order to avoid data corruption.
Add related tests to lvconvert-raid-takeover.sh
Resolves: rhbz1388962
Avoid monitoring of activated cache-pool - where the only purpose ATM
is to clear metadata volume which is actually activate in place
of cache-pool name (using public LV name).
Since VG lock is held across whole clear operation, dmeventd cannot
be used anyway - however in case of appliction crash we may
leave unmonitored device.
In future we may provide better mechanism as the current name
replacemnet is creating 'uncommon' table setups in case the metadata
LV is more complex type like raid (needs some futher thinking about
error path results).
Another point to think about is the fact we should not clear device
while holding lock (i.e. dmeventd mirror repair cannot work in cases
like this).
We have only 2 users of _lv_active() - one was already checking for ==1
while the other use (_lv_is_active()) could have take '-1' as a sign of having
an LV active. So return 0 and log_debug also the reason while detection
has failed (i.e. in case --driverload n - it's kind of expectable,
but might have confused user seeing just <backtrace>).
Add more code to properly store status for snapshot segment
maintaining lvm2 fiction of COW and snapshot internal volumes.
The key issue here is however not though-through reporting
logic - as there is no single answer for whole line state.
It not counting with layer and we may need few more ioctl to
cover all reporting needs depending upon what is actually
needed.
In reality we need to 'cache' more ioctl status queries for
individual LVs and their segments (so they checked at most once).
The other 'hard' topic for conversion is mirror segment handling.
Also we definitelly need to relocate some logic into segment's methods,
yet it might be complex as we have not clear border between targets.
TODO: define more clearly how are reporting fields defined in case
we 'stack' volumes like - cache of stacked thin LV snapshot origin.
To get better control when flushing is used add extra arg when
setting up dm task.
By default now check dm device status without flush.
(At this moment this should effect only thin and cache volumes).
Also switch dev_manager_thin_pool_status() to use more
readable 'flush' parameter instead of 'no_flush'.
Before executing modprobe for given module name, just check
if the module is not already present in /sys/module.
Useful when checking dm-cache-policy modules as we do not
having matching interface like for targets.
A snapshot merge into its origin cannot be initiated while the devices
are in use. If there is outside interference (such as from udev),
the suspend (preload) and resume stages can reach conflicting decisions
about whether or not to proceed.
Try to make the logic more robust by checking the inactive or live
table during resume. (This is still not perfect.)
Commit 844b009584 tried to move
limit for usage of noflush to 'preload' however this was not
correctly processed.
Intead explicitly check for which types we do not want noflush
and also add debug message in this case.
dmeventd daemon may call further code itself that looks at /dev, e.g.
via dmeventd_lvm2_command call. We need to have a consistent view of
the /dev content at that time. Therefore, sync /dev content before
calling monitoring hook which contacts dmeventd.
This problem was quite hidden before, but now it has manifested itself
because of recent additions to dev-cache code where we started looking
at device holders as seen in sysfs. What happened here was that the
device was already in sysfs, but not yet under /dev and this triggered
the new error message sometimes:
log_error("%s: failed to find associated device structure for holder %s.", devname, devpath);
This problem has manifested recently in our api/pytest.sh test from
testsuite where we create thin pool LVs and thin LVs and hence it also
causes dmeventd to be used as well and these error messages were
visible there.
Remove long outstand unused code lines, which were already
been obsoleted by other code.
Statuses and snapshot tree creation is already handled differently.
Also drop some 'extra' log_error() and use only stack;
since error has already been reported.
lv preload for detached LVs started to be used also
for various other types which just happens to pass through
weak if() condition.
TODO: find here better solution to rather explicitly check
for types we really need to preload.
We do not won't to 'expose' internals of VG struct.
ATM we use lists to keep all LVs - we may want to switch
to better struct for quicker 'search'.
Since we do not need 'lists' but always actual LV,
switch find_lv_in_vg_by_lvid() to return LV,
and replaces some use case of find_lv_in_vg()
with 'better' working find_lv() which already
returns LV.
Existing messaging intarface for thin-pool has a few 'weak' points:
* Message were posted with each 'resume' operation, thus not allowing
activation of thin-pool with the existing state.
* Acceleration skipped suspend step has not worked in cluster,
since clvmd resumes only nodes which are suspended (have proper lock
state).
* Resume may fail and code is not really designed to 'fail' in this
phase (generic rule here is resume DOES NOT fail unless something serious
is wrong and lvm2 tool usually doesn't handle recovery path in this case.)
* Full thin-pool suspend happened, when taken a thin-volume snapshot.
With this patch the new method relocates message passing into suspend
state.
This has a few drawbacks with current API, but overal it performs
better and gives are more posibilities to deal with errors.
Patch introduces a new logic for 'origin-only' suspend of thin-pool and
this also relates to thin-volume when taking snapshot.
When suspend_origin_only operation is invoked on a pool with
queued messages then only those messages are posted to thin-pool and
actual suspend of thin pool and data and metadata volume is skipped.
This makes taking a snapshot of thin-volume lighter operation and
avoids blocking of other unrelated active thin volumes.
Also fail now happens in 'suspend' state where the 'Fail' is more expected
and it is better handled through error paths.
Activation of thin-pool is now not sending any message and leaves upto a tool
to decided later how to finish unfinished double-commit transaction.
Problem which needs some API improvements relates to the lvm2 tree
construction. For the suspend tree we do not add target table line
into the tree, but only a device is inserted into a tree.
Current mechanism to attach messages for thin-pool requires the libdm
to know about thin-pool target, so lvm2 currently takes assumption, node
is really a thin-pool and fills in the table line for this node (which
should be ensured by the PRELOAD phase, but it's a misuse of internal API)
we would possibly need to be able to attach message to 'any' node.
Other thing to notice - current messaging interface in thin-pool
target requires to suspend thin volume origin first and then send
a create message, but this could not have any 'nice' solution on lvm2
side and IMHO we should introduce something like 'create_after_resume'
message.
Patch also changes the moment, where lvm2 transaction id is increased.
Now it happens only after successful finish of kernel transaction id
change. This change was needed to handle properly activation of pool,
which is in the middle of unfinished transaction, and also this corrects
usage of thin-pool by external apps like Docker.
Older lvm2 tools where always providing linear mapping for thin pool.
Recent lvm2 version however support external usage of thin pool and
empty/unused pools are loaded without such external linear mapping.
So this patch covers 'upgrade' problem, where older tool has activated
thin-pool with 'linear' layer mapping, and newer tools didn't expected
such mapping to exist and were not able to deactivate such table.
So before checking for new layout in dm-table, check if there is not
an old one already there.
Check splitted leg is active before preload.
(Since splitmirrors currently only does work active raid volumes
it's not a change for current code flow).
Minor optimization included - when already positively checked
for raid image don't check again for raid metadata.
for_each_sub_lv() normally does not put pool_lv into deps.
So for now go around it in 'lv_preload()' and add explicit
call with pool.
TODO: think about a better way, we want pool_lv deps only in certain
moments, so maybe for_each_sub_lv() needs new arg for this.
When raid is being splitted, extracted leg & metadata
is still floating in the table - and thus we need to
detect this case and properly preload their matching
table so consequent activation of extracted LVs properly
renames (and FREES) existing raid images, so ongoing
image name shifting will work.
