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There are likely more bits of code that can be removed,
e.g. lvm1/pool-specific bits of code that were identified
using FMT flags.
The vgconvert command can likely be reduced further.
The lvm1-specific config settings should probably have
some other fields set for proper deprecation.
For reporting commands (pvs,vgs,lvs,pvdisplay,vgdisplay,lvdisplay)
we do not need to repeat the label scan of devices in vg_read if
they all had matching metadata in the initial label scan. The
data read by label scan can just be reused for the vg_read.
This cuts the amount of device i/o in half, from two reads of
each device to one. We have to be careful to avoid repairing
the VG if we've skipped rescanning. (The VG repair code is very
poor, and will be redone soon.)
Recent changes allow some major simplification of the way
lvmcache works and is used. lvmcache_label_scan is now
called in a controlled fashion at the start of commands,
and not via various unpredictable side effects. Remove
various calls to it from other places. lvmcache_label_scan
should not be called from anywhere during a command, because
it produces an incorrect representation of PVs with no MDAs,
and misclassifies them as orphans. This has been a long
standing problem. The invalid flag and rescanning based on
that is no longer used and removed. The 'force' variation is
no longer needed and removed.
The improved detection of bad metadata when scanning
(where errors were ignored before) means we now have to
override some errors when forcibly erasing damaged metadata.
This is a temporary hacky workaround to the problem of
reads going through bcache and writes not using bcache.
The write path wants to read parts of data that it is
incrementally writing to disk, but the reads (using
bcache) don't work because the writes are not in the
bcache. For now, add a dev to bcache before each attempt
to read it in case it's being used on the write path.
Create a new dev->bcache_fd that the scanning code owns
and is in charge of opening/closing. This prevents other
parts of lvm code (which do various open/close) from
interfering with the bcache fd. A number of dev_open
and dev_close are removed from the reading path since
the read path now uses the bcache.
With that in place, open(O_EXCL) for pvcreate/pvremove
can then be fixed. That wouldn't work previously because
of other open fds.
When process_each_pv() calls vg_read() on the orphan VG, the
internal implementation was doing an unnecessary
lvmcache_label_scan() and two unnecessary label_read() calls
on each orphan. Some of those unnecessary label scans/reads
would sometimes be skipped due to caching, but the code was
always doing at least one unnecessary read on each orphan.
The common format_text case was also unecessarily calling into
the format-specific pv_read() function which actually did nothing.
By analyzing each case in which vg_read() was being called on
the orphan VG, we can say that all of the label scans/reads
in vg_read_orphans are unnecessary:
1. reporting commands: the information saved in lvmcache by
the original label scan can be reported. There is no advantage
to repeating the label scan on the orphans a second time before
reporting it.
2. pvcreate/vgcreate/vgextend: these all share a common
implementation in pvcreate_each_device(). That function
already rescans labels after acquiring the orphan VG lock,
which ensures that the command is using valid lvmcache
information.
This fixes the use of lvmcache_label_rescan_vg() in the previous
commit for the special case of independent metadata areas.
label scan is about discovering VG name to device associations
using information from disks, but devices in VGs with
independent metadata areas have no information on disk, so
the label scan does nothing for these VGs/devices.
With independent metadata areas, only the VG metadata found
in files is used. This metadata is found and read in
vg_read in the processing phase.
lvmcache_label_rescan_vg() drops lvmcache info for the VG devices
before repeating the label scan on them. In the case of
independent metadata areas, there is no metadata on devices, so the
label scan of the devices will find nothing, so will not recreate
the necessary vginfo/info data in lvmcache for the VG. Fix this
by setting a flag in the lvmcache vginfo struct indicating that
the VG uses independent metadata areas, and label rescanning should
be skipped.
In the case of independent metadata areas, it is the metadata
processing in the vg_read phase that sets up the lvmcache
vginfo/info information, and label scan has no role.
Move the location of scans to make it clearer and avoid
unnecessary repeated scanning. There should be one scan
at the start of a command which is then used through the
rest of command processing.
Previously, the initial label scan was called as a side effect
from various utility functions. This would lead to it being called
unnecessarily. It is an expensive operation, and should only be
called when necessary. Also, this is a primary step in the
function of the command, and as such it should be called prominently
at the top level of command processing, not as a hidden side effect
of a utility function. lvm knows exactly where and when the
label scan needs to be done. Because of this, move the label scan
calls from the internal functions to the top level of processing.
Other specific instances of lvmcache_label_scan() are still called
unnecessarily or unclearly by specific commands that do not use
the common process_each functions. These will be improved in
future commits.
During the processing phase, rescanning labels for devices in a VG
needs to be done after the VG lock is acquired in case things have
changed since the initial label scan. This was being done by way
of rescanning devices that had the INVALID flag set in lvmcache.
This usually approximated the right set of devices, but it was not
exact, and obfuscated the real requirement. Correct this by using
a new function that rescans the devices in the VG:
lvmcache_label_rescan_vg().
Apart from being inexact, the rescanning was extremely well hidden.
_vg_read() would call ->create_instance(), _text_create_text_instance(),
_create_vg_text_instance() which would call lvmcache_label_scan()
which would call _scan_invalid() which repeats the label scan on
devices flagged INVALID. lvmcache_label_rescan_vg() is now called
prominently by _vg_read() directly.
To do label scanning, lvm code calls lvmcache_label_scan().
Change lvmcache_label_scan() to use the new label_scan()
based on bcache.
Also add lvmcache_label_rescan_vg() which calls the new
label_scan_devs() which does label scanning on only the
specified devices. This is for a subsequent commit and
is not yet used.
New label_scan function populates bcache for each device
on the system.
The two read paths are updated to get data from bcache.
The bcache is not yet used for writing. bcache blocks
for a device are invalidated when the device is written.
No longer use the external 'result' pointer internally to set up the
cached label. The callback _set_label_read_result() is now given the
internal label pointer directly
Callers that don't need the result are no longer required to pass a
label pointer into label_read().
Callers that read larger amounts of data now get a pointer to read-only
data directly without copying it through an intermediate buffer. This
data is owned by the device layer so the callers no longer free it.
If it obtains the data, it passes it into the supplied callback function
and returns 1. Otherwise the callback receives failed = 1.
Updated config_file_read_fd to use this and similarly return the data
via a callback fn of its own.
Dedicated functions are now used to process each piece of data obtained,
so the refactoring in this file gives us one for the vgsummary and one
for the metadata header. This new type of function takes two parameters
(for now), the obtained data plus a single struct (that must not
reference any data on the stack) that wraps up the entire context needed
to process it.
Rename dev_read() to dev_read_buf() - the function that reads data
into a supplied buffer.
Introduce a new dev_read() that allocates the buffer it returns and
switch the important users over to this. No caller may change the
returned data. (For now, callers are responsible for freeing it after
use, but later the device layer will take full ownership.)
dev_read_buf() should only be used for tiny buffers or unimportant code
(such as the old disk formats).
The creation of wrapped around metadata - where the start of metadata is
written up to the end of the buffer and the remainder follows back at
the start of the buffer - is now restricted to cases where writing the
metadata in one piece wouldn't fit. This shouldn't happen in 'normal'
usage so let's begin treating the code for this as a special case that
can be ignored when optimising 'normal' cases.
If there is sufficient space in the metadata area, align the next
metadata to a disk offset that is a multiple of 4096 bytes and
don't write it circularly. If it doesn't all fit at the end
of the metadata area, go back to the start and write it all there
contiguously.
If there is insufficient space to use the new stricter rules, revert to
the original behaviour, aligning on 512-byte boundaries wrapping around
the circular buffer as required.
Use new ALIGN_ABSOLUTE macro when calculating the start location
of new metadata and adjust the end of buffer detection so that
there is no longer an imposed gap between old and new metadata.
Currently both start and offset should always be divisible by alignment,
so this should have no effect, but a later patch will increase alignment
so these variables can no longer be optimised out.
Expand out the metadata wrapping calculations to prepare
to support a larger alignment.
The current alignment is 512 bytes so
(mdac_area_start + rlocn->offset) % alignment is zero.
Mark the first metadata area on each text format PV as MDA_PRIMARY.
Pass this information down to the device layer so that when
there are two metadata areas on a block device, we can easily
distinguish two independent streams of I/O.
Introduce enum dev_io_reason to categorise block device I/O
in debug messages so it's obvious what it is for.
DEV_IO_SIGNATURES /* Scanning device signatures */
DEV_IO_LABEL /* LVM PV disk label */
DEV_IO_MDA_HEADER /* Text format metadata area header */
DEV_IO_MDA_CONTENT /* Text format metadata area content */
DEV_IO_FMT1 /* Original LVM1 metadata format */
DEV_IO_POOL /* Pool metadata format */
DEV_IO_LV /* Content written to an LV */
DEV_IO_LOG /* Logging messages */
When an ignored metadata area gets flagged for use again, make sure the
code doesn't try to parse its old metadata. Firstly by trying to detect
this situation and skipping the read (while still remembering the
position reached in the circular buffer), and secondly by clearing the
invalid live metadata location on disk as a precaution when subsequently
writing out the precommitted metadata.
Problems showed up when a metadata area in one VG got moved to
another VG in ignored state (still holding metadata for the original
VG) and then later got brought into use in the new VG - only the header
should be read in this case, not any of the metadata content.
vgmerge suffers from a similar problem to the one fixed in commit
8146548d25 ("vgsplit: Fix intermediate
metadata corruption.")
When merging, splitting or renaming VGs, use a new PV status flag
PV_MOVED_VG to mark the PVs that hold metadata with the old VG name and
use this to provide PV-level granularity instead of incorrectly assuming
all PVs in the VG are the same.
Changing the VG of a PV uses the same on-disk mechanism as vgrename.
This relies on recognising both the old and new VG names. Prior to this
patch the vgsplit code incorrectly provided the new VG name twice
instead of the old and new ones. This lead the low-level mechanism not
to recognise the device as already belonging to a VG and so paying no
attention to the location of its existing metadata, sometimes partly
overwriting it and then later trying to read the corrupt metadata and
issuing a checksum error.
lvmcache_foreach_mda() can fail for numerous reasons
and failing error code cannot be ignored (out-of-memory...)
TODO: might need more error handling tunning.
Fix code checking that the 2nd mda which is at the end of disk really
fits the available free space and avoid any DA and MDA interleaving when
we already have DA preallocated. This mainly applies when we're restoring
a PV from VG backup using pvcreate --restorefile where we may already have
some DA preallocated - this means the PV was in a VG before with already
allocated space from it (the LVs were created). Hence we need to avoid
stepping into DA - the MDA can never ever be inside in such case!
The code responsible for this calculation was already in
_text_pv_add_metadata_area fn, but it had a bug in the calculation where
we subtracted one more sector by mistake and then the code could still
incorrectly allocate the MDA inside existing DA. The patch also renames
the variable in the code so it doesn't confuse us in future.
Also, if the 2nd mda doesn't fit, don't silently continue with just 1
MDA (at the start of the disk). If 2nd mda was requested and we can't
create that due to unavailable space, error out correctly (the patch
also adds a test to shell/pvcreate-operation.sh for this case).
In order to reject out of place reshaping with segment data_offset
field on old runtime, add a respective segment type incompatibility
flag causing "+RESHAPE_DATA_OFFSET" to be suffixed to the segment
type name.
Prohibit activation of reshaping RaidLVs on incompatible
lvm2 runtime by storing e.g. 'raid5+RESHAPE' segment type
strings in the lvm2 metadata. Incompatible runtime not
supporting reshaping won't be able to activate those thus
avoiding potential data corruption.
Any new non-reshaping lvconvert command will reset the
segment type string from 'raid5+RESHAPE' to 'raid5'.
See commits
0299a7af1e and
4141409eb0
for segtype flag support.
Since lvmetad is using 'MISSING' in status for 'another' purpose,
we need to support ATM also flag get from this place.
Until fixed better - we accept both flags - alhough lvm2 will
only print in flags.
Switch METADATA_FORMAT flag usage to be stored via segtype
instead of 'status' flag which appeared to cause major
incompatibility troubles.
For backward compatiblity segtype flags are still accepted also
via 'status' bits which were used from version 2.02.169 so metadata
saved by this newer lvm2 version should still work nicely, although
new save version will no longer work on this older lvm2 version.
Allow storing LV status bits with segment type name field.
Switching to this since this field has better support for compatibility
with older version of lvm2 - since such unknown segtype will not cause
complete invisiblity of metadata from older lvm2 code - just the
particular LV will become unusable with unknown type of segment.
This patch fixed lvm2 compilation running on x32 arch.
(Using 64bit x86 cpu features but running on 32b address space,
so consuming less mem in VM).
On x32 arch 'time_t' is 64bit while 'long' is 32bit.
Cache pool read/writes metadata_format within its segment type..
For CachePoolLV unselected metadata format is NOT stored in metadata.
For CacheLV when metadata format is not present/selected in lvm2 metadata,
it's automatically assumed to be the version 1 (backward compatible).
To ensure older lvm2 will not 'miss-read' metadata with new version 2,
such LV is marked with METADATA_FORMAT status flag (segment is
specifying metadata format). So when cache uses metadata format 2,
it will become inaccesible on older system without such support.
(kernel dm cache < 1.10, lvm2 < 2.02.169).
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
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.
Previously, a command sent lvmetad new VG metadata in vg_commit().
In vg_commit(), devices are suspended, so any memory allocation
done by the command while sending to lvmetad, or by lvmetad while
updating its cache could deadlock if memory reclaim was triggered.
Now lvmetad is updated in unlock_vg(), after devices are resumed.
The new method for updating VG metadata in lvmetad is in two phases:
1. In vg_write(), before devices are suspended, the command sends
lvmetad a short message ("set_vg_info") telling it what the new
VG seqno will be. lvmetad sees that the seqno is newer than
the seqno of its cached VG, so it sets the INVALID flag for the
cached VG. If sending the message to lvmetad fails, the command
fails before the metadata is committed and the change is not made.
If sending the message succeeds, vg_commit() is called.
2. In unlock_vg(), after devices are resumed, the command sends
lvmetad the standard vg_update message with the new metadata.
lvmetad sees that the seqno in the new metadata matches the
seqno it saved from set_vg_info, and knows it has the latest
copy, so it clears the INVALID flag for the cached VG.
If a command fails between 1 and 2 (after committing the VG on disk,
but before sending lvmetad the new metadata), the cached VG retains
the INVALID flag in lvmetad. A subsequent command will read the
cached VG from lvmetad, see the INVALID flag, ignore the cached
copy, read the VG from disk instead, update the lvmetad copy
with the latest copy from disk, (this clears the INVALID flag
in lvmetad), and use the correct VG metadata for the command.
(This INVALID mechanism already existed for use by lvmlockd.)
Previously, vgcfgrestore would attempt to vg_remove the
existing VG from lvmetad and then vg_update to add the
restored VG. But, if there was a failure in the command
or with vg_update, the lvmetad cache would be left incorrect.
Now, disable lvmetad before the restore begins, and then
rescan to populate lvmetad from disk after restore has
written the new VG to disk.
A number of places are working on a specific dev when they
call lvmcache_info_from_pvid() to look up an info struct
based on a pvid. In those cases, pass the dev being used
to lvmcache_info_from_pvid(). When a dev is specified,
lvmcache_info_from_pvid() will verify that the cached
info it's using matches the dev being processed before
returning the info. Calling code will not mistakenly
get info for the wrong dev when duplicate devs exist.
This confusion was happening when scanning labels when
duplicate devs existed. label_read for the first dev
would add an info struct to lvmcache for that dev/pvid.
label_read for the second dev would see the pvid in
lvmcache from first dev, and mistakenly conclude that
the label_read from the second dev can be skipped
because it's already been done. By verifying that the
dev for the cached pvid matches the dev being read,
this mismatch is avoided and the label is actually read
from the second duplicate.
